JP5662079B2 - Etching method - Google Patents

Description

  The present invention relates to an etching processing method for forming a hole or the like having a high aspect ratio.

  In a semiconductor device manufactured from a semiconductor wafer using a plasma etching process, it is required to form a pattern having a depth larger than the diameter of the opening, for example, a hole having a high aspect ratio.

  In order to form a hole with a large aspect ratio, it is particularly necessary to frequently use sputtering of the target film by cations in the plasma. In this case, as shown in FIG. 12, holes 121 formed in the target film 120 are used. The cation 122 stays at the bottom of the hole 121 and the staying cation 122 electrically inhibits the continuation of the cation 123 from reaching the bottom of the hole 121, thereby changing the course of the cation 123 that continues in the hole 121. There are things to do. As a result, a problem such as distortion of the hole 121 may occur.

  In response to this, a technique for introducing electrons into the bottom of a hole has been developed (see, for example, Patent Document 1). Thereby, the cation staying at the bottom of the hole is electrically neutralized, and the path of the subsequent cation is not changed.

JP 2007-134530 A

  However, in recent years, with the progress of miniaturization of each part, it is required to form a hole having a higher aspect ratio, for example, a hole having an aspect ratio of 30 or more in the target film. When the aspect ratio is 30 or more, there is a problem that even if the above-described method is used, the hole cannot be prevented from being distorted.

  An object of the present invention is to provide an etching method that can prevent a pattern from being distorted even if the aspect ratio of the pattern to be formed is high.

In order to achieve the above object, an etching processing method according to claim 1 includes a processing chamber in which plasma is generated, a mounting table disposed in the processing chamber, and a mounting table disposed in the processing chamber facing the mounting table. A first high-frequency power having a relatively high frequency is applied to the inside of the processing chamber, and a second high-frequency power having a frequency lower than that of the first high-frequency power is applied to the mounting table, In a substrate processing apparatus in which direct-current power is applied to an electrode, etching that has an etching target film and a mask film formed on the etching target film and that performs an etching process on a substrate placed on the mounting table A processing method comprising: a pattern shape improving step for improving a shape of a pattern formed on a mask film on the substrate; and the etching process using the mask film having an improved pattern shape. Etching the target layer in a plasma and a target film etching step of forming a pattern on the etching target film, in the pattern improvement step, etching the mask layer by plasma, in the target film etching step, the While applying DC power to the electrode, at least the second high-frequency power is applied to the mounting table in the form of a pulse wave, and the second high-frequency power is applied to the electrode while the DC power is applied to the electrode. By creating a state that is not applied to the pedestal, the sheath generated on the surface of the substrate is extinguished and electrons generated from the electrode to which the DC power is applied enter the pattern .

  The etching processing method according to claim 2 is the etching processing method according to claim 1, wherein, in the target film etching step, the first high-frequency power is also applied in a pulse wave shape, and the first high-frequency power is applied to the processing chamber. It is characterized by creating a state where it is not applied to the inside.

  According to a third aspect of the present invention, in the etching method of the second aspect, in the target film etching step, the first high frequency power and the second high frequency power are synchronized and applied in a pulse waveform. It is characterized by that.

  The etching processing method according to claim 4 is the etching processing method according to any one of claims 1 to 3, wherein, in the target film etching step, the direct current is applied at a potential lower than a bias voltage potential generated in the substrate. Electric power is applied to the electrode.

  The etching processing method according to claim 5 is the etching processing method according to any one of claims 1 to 4, wherein in the target film etching step, the second high-frequency power is applied to the mounting table, and the frequency is 1 kHz. It is applied in the form of any pulse wave of ˜50 KHz.

  The etching processing method according to claim 6 is the etching processing method according to claim 5, wherein the frequency is any of 10 KHz to 50 KHz.

  The etching method according to claim 7 is the etching method according to any one of claims 1 to 6, wherein, in the target film etching step, a duty ratio of the second high-frequency power applied in a pulse wave shape. Is 10% to 90%.

  An etching treatment method according to an eighth aspect is the etching treatment method according to the seventh aspect, wherein the duty ratio is any one of 50% to 90%.

  The etching method according to claim 9 is the etching method according to any one of claims 1 to 8, wherein the second high frequency power is not applied to the mounting table in the target film etching step. Characterized by lasting at least 5 microseconds.

  The etching processing method according to claim 10 is the etching processing method according to any one of claims 1 to 9, wherein an aspect ratio of a pattern formed on the etching target film in the target film etching step is 30 or more. It is characterized by being.

  The etching method according to claim 11 is the etching method according to any one of claims 1 to 10, wherein the mask film is an organic film, and the pattern shape improving step is etched by the plasma. A mask film curing step of curing the mask film by bringing electrons into contact with the mask film is characterized.

  An etching processing method according to a twelfth aspect is the etching processing method according to the eleventh aspect, wherein the DC power is applied to the electrode in the mask film curing step.

  The etching processing method according to claim 13 is the etching processing method according to claim 12, wherein, in the mask film curing step, the voltage of the applied DC power is −900V or less.

  The etching processing method according to claim 14 is the etching processing method according to any one of claims 11 to 13, wherein plasma is generated from a deposition gas in the mask film curing step.

  The etching treatment method according to claim 15 is the etching treatment method according to any one of claims 1 to 10, wherein the mask film is an inorganic film.

  The etching processing method according to claim 16 is the etching processing method according to claim 15, wherein the inorganic film includes at least a polysilicon film.

  The etching treatment method according to claim 17 is the etching treatment method according to any one of claims 1 to 16, wherein in the pattern shape improvement step, the shape of the pattern is improved to improve the hole of the mask film. When viewed from above, the shape is made close to a perfect circle.

  The etching method according to claim 18, wherein in the etching method according to any one of claims 1 to 17, the target film etching step generates plasma from a mixed gas containing at least helium gas. And

  According to the present invention, since the shape of the pattern formed in the mask film on the substrate is improved, the shape defect of the pattern formed in the mask film is reflected in the shape of the pattern formed in the etching target film. Can be prevented. In addition, when the etching target film is etched with plasma using a mask film having an improved pattern shape, DC power is applied to the electrode, and second high-frequency power is applied to the mounting table in a pulse waveform. Since a state in which the second high-frequency power is not applied to the mounting table is created, a large amount of electrons can be generated and a state in which the sheath on the substrate disappears can be created. Can be reliably introduced into the bottom of the pattern formed. As a result, it is possible to prevent the pattern from being distorted even if the formed pattern has a high aspect ratio.

It is a figure which shows roughly the structure of the substrate processing apparatus which performs the etching processing method which concerns on the 1st Embodiment of this invention. It is a figure which shows the shape of the hole formed in the oxide film by the conventional etching processing method, FIG. 2 (A) is a longitudinal cross-sectional view of the hole formed in the oxide film, FIG. 2 (B) is an oxide film FIG. 2C is a horizontal sectional view of a hole at a depth of 300 nm from the surface, FIG. 2C is a horizontal sectional view of a hole at a depth of 700 nm from the surface of the oxide film, and FIG. FIG. 2E is a horizontal sectional view of a hole when the depth from the surface is 1500 nm, FIG. 2E is a horizontal sectional view of the hole when the depth from the surface of the oxide film is 2300 nm, and FIG. It is a longitudinal cross-sectional view of the mask film | membrane before formation of a hole, FIG.2 (G) is a top view of the hole formed in the mask film | membrane in FIG.2 (F). It is sectional drawing which shows roughly the structure of a part of wafer processed by the etching processing method which concerns on this Embodiment. It is process drawing which shows the etching processing method which concerns on this Embodiment. It is a figure for demonstrating the shape improvement of the hole of a mask film | membrane in the etching processing method which concerns on this Embodiment, FIG. 5 (A) is an expanded longitudinal cross-sectional view of the hole vicinity of a mask film | membrane, FIG. FIG. 5C is a plan view showing holes in the mask film before shape improvement, and FIG. 5C is a plan view showing holes in the mask film after shape improvement. It is a figure for demonstrating hardening of the mask film | membrane in the etching processing method which concerns on this Embodiment, FIG. 6 (A) is an expanded longitudinal cross-sectional view of the hole vicinity of a mask film | membrane, FIG.6 (B) is before hardening. FIG. 6C is a plan view showing holes in the mask film after curing. FIG. 7A is a diagram for explaining the formation of holes in the SiO ₂ film in the etching method according to the present embodiment, and FIG. 7A is a diagram for explaining the etching of the SiO ₂ film, and FIG. ) Is a diagram for explaining electrical neutralization of cations staying at the bottom of the hole. It is a figure for demonstrating the high-frequency power for plasma generation and the high-frequency power for ion attraction which are applied in the etching processing method which concerns on this Embodiment, and the electric current which flows through the surface vicinity of a wafer. It is sectional drawing which shows roughly the structure of a part of wafer processed by the etching processing method which concerns on the 2nd Embodiment of this invention. It is process drawing which shows the etching processing method which concerns on this Embodiment. It is a figure for demonstrating the shape improvement of the hole of a mask film | membrane in the etching processing method which concerns on this Embodiment, FIG. 11 (A) is an expanded longitudinal cross-sectional view of the hole vicinity of a mask film | membrane, FIG.11 (B) FIG. 11 is a plan view showing holes in the mask film before shape improvement, and FIG. 11C is a plan view showing holes in the mask film after shape improvement. It is a longitudinal cross-sectional view for demonstrating generation | occurrence | production of the distortion of the hole in the conventional etching processing method. It is a figure for demonstrating the modulation | alteration of the application of the high frequency electric power in the etching processing method which concerns on 1st Embodiment, FIG. 13 (A) shows the modulation state of the application of the high frequency electric power for ion attraction, FIG. B) shows the waveform of the high frequency power for ion attraction when the high frequency power for ion attraction is repeatedly turned on and off. It is a figure for demonstrating the form of deposition of the deposit in the frontage of a hole, FIG. 14 (A) shows the case of a continuous application, and FIG. 14 (B) shows the case of a pulse wave-like application. It is a figure for demonstrating the form of the change of the electron density in the process chamber in the case of a continuous application and the case of a pulse wave application. It is a figure for demonstrating the form of the change of the electron temperature in the process chamber in the case of a continuous application and the case of a pulse-like application. It is a figure for demonstrating the adhesion form of a radical, FIG. 17 (A) shows the case of continuous application, and FIG. 17 (B) shows the case of a pulse-like application. It is a figure for demonstrating the adhesion form of a radical when the mixed gas containing He gas as a noble gas is used in the case of continuous application.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a description will be given of a substrate processing apparatus that executes an etching processing method according to a first embodiment of the present invention.

  FIG. 1 is a diagram schematically showing a configuration of a substrate processing apparatus that executes an etching processing method according to the present embodiment. This substrate processing apparatus performs a plasma etching process on a semiconductor device wafer (hereinafter simply referred to as “wafer”) as a substrate.

  In FIG. 1, a substrate processing apparatus 10 has, for example, a chamber 11 that accommodates a wafer W having a diameter of 300 m, and a cylindrical susceptor 12 on which a semiconductor device wafer W is placed is disposed. Has been. In the substrate processing apparatus 10, a side exhaust path 13 is formed by the inner side wall of the chamber 11 and the side surface of the susceptor 12. An exhaust plate 14 is disposed in the middle of the side exhaust path 13.

  The exhaust plate 14 is a plate-like member having a large number of through holes, and functions as a partition plate that partitions the interior of the chamber 11 into an upper part and a lower part. Plasma is generated in an upper part (hereinafter referred to as “processing chamber”) 15 inside the chamber 11 partitioned by the exhaust plate 14 as will be described later. Further, an exhaust pipe 17 that exhausts gas inside the chamber 11 is connected to a lower portion 16 (hereinafter referred to as “exhaust chamber (manifold)”) inside the chamber 11. The exhaust plate 14 captures or reflects the plasma generated in the processing chamber 15 to prevent leakage to the manifold 16.

  TMP (Turbo Molecular Pump) and DP (Dry Pump) (both not shown) are connected to the exhaust pipe 17, and these pumps evacuate the chamber 11 to reduce the pressure. The pressure inside the chamber 11 is controlled by an APC valve (not shown).

  A first high-frequency power source 18 is connected to the susceptor 12 inside the chamber 11 via a first matching device 19, and a second high-frequency power source 20 is connected via a second matching device 21. One high frequency power supply 18 applies a relatively high frequency, for example, 40 MHz plasma generation high frequency power (first high frequency power) to the susceptor 12, and the second high frequency power supply 20 has a relatively low frequency, for example, 2 MHz. The high frequency power for ion attraction (second high frequency power) is applied to the susceptor 12. Thereby, the susceptor 12 functions as an electrode. Further, the first matching unit 19 and the second matching unit 21 reduce the reflection of the high frequency power from the susceptor 12 to maximize the application efficiency of the high frequency power to the susceptor 12.

  The upper part of the susceptor 12 has a shape in which a small-diameter cylinder protrudes from the tip of a large-diameter cylinder along a concentric axis, and a step is formed in the upper part so as to surround the small-diameter cylinder. An electrostatic chuck 23 made of ceramics having an electrostatic electrode plate 22 therein is disposed at the tip of a small diameter cylinder. A first direct current power source 24 is connected to the electrostatic electrode plate 22, and when a positive potential direct current power is applied to the electrostatic electrode plate 22, the surface of the wafer W on the electrostatic chuck 23 side (hereinafter, referred to as the “electrostatic electrode plate 22”). A negative potential is generated on the “back surface”), and a potential difference is generated between the electrostatic electrode plate 22 and the back surface of the wafer W, and the wafer W is electrostatically charged by the Coulomb force or the Johnson-Rahbek force resulting from the potential difference. It is sucked and held by the chuck 23.

  In addition, a focus ring 25 is placed on a step in the upper part of the susceptor 12 so as to surround the wafer W attracted and held by the electrostatic chuck 23 on the upper part of the susceptor 12. The focus ring 25 is made of Si. That is, since the focus ring 25 is made of a semi-conductor, the plasma distribution area is expanded not only on the wafer W but also on the focus ring 25, so that the plasma density on the peripheral edge of the wafer W is increased to the center of the wafer W. Maintain the same plasma density as above. This ensures the uniformity of the plasma etching process performed on the entire surface of the wafer W.

  A shower head 26 is disposed on the ceiling of the chamber 11 so as to face the susceptor 12. The shower head 26 includes, for example, an upper electrode plate 27 made of silicon, a cooling plate 28 that detachably supports the upper electrode plate 27, and a lid 29 that covers the cooling plate 28. The upper electrode plate 27 is made of a disk-like member having a large number of gas holes 30 penetrating in the thickness direction, and is made of Si that is a semiconductor. A buffer chamber 31 is provided inside the cooling plate 28, and a processing gas introduction pipe 32 is connected to the buffer chamber 31, and the processing gas introduction pipe 32 is connected to a processing gas supply device (not shown). ing.

  For example, the processing gas supply device appropriately adjusts the flow ratio of various gases to generate a mixed gas, and the mixed gas is supplied into the processing chamber 15 through the processing gas introduction pipe 32, the buffer chamber 31, and the gas hole 30. Introduce.

  A second DC power source 33 is connected to the upper electrode plate 27 of the shower head 26, and DC power having a negative potential is applied to the upper electrode plate 27. At this time, positive ions are implanted into the upper electrode plate 27, and accordingly, the upper electrode plate 27 emits (secondary) electrons to improve the electron density distribution in the plasma inside the processing chamber 15.

  In the substrate processing apparatus 10, the processing gas introduced into the processing chamber 15 is excited by high-frequency power for plasma generation applied to the processing chamber 15 from the first high-frequency power source 18 through the susceptor 12 to become plasma. . The positive ions in the plasma are attracted toward the wafer W by the high-frequency power for ion attraction applied by the second high-frequency power source 20 to the susceptor 12, and the wafer W is subjected to plasma etching.

  By the way, as described above, for example, when a hole having an aspect ratio of 30 or more is formed by plasma etching, the hole is distorted even if the method according to Patent Document 1 described above is used.

  Therefore, the inventor of the present invention, as shown in FIG. 2A, the depth from the surface of the oxide film 35 in each of the holes 34 distorted by the conventional etching method is 300 nm (corresponding to an aspect ratio of 4). Observation of horizontal sections 36a to 36d of 700 nm (corresponding to an aspect ratio of 9), 1500 nm (corresponding to an aspect ratio of 20), and 2300 nm (corresponding to an aspect ratio of 30) reveals that FIG. E) It was confirmed that the hole 34 was not distorted only in the vicinity of the bottom, but was also distorted in a relatively shallow portion, and the tendency of distortion in each of the horizontal sections 36a to 36d was the same. .

  Further, the present inventor confirmed the shape of the hole 38 in the mask film 37 on the oxide film 35 before the formation of the hole 34 as shown in FIG. 2 (F), as shown in FIG. 2 (G). The hole 38 was distorted in plan view, and it was confirmed that the tendency of the distortion was the same as the tendency of distortion in each of the horizontal cross sections 36a to 36d.

  As a result of careful consideration of these confirmed facts, the present inventor has found that the hole 34 is distorted mainly due to the defective shape of the hole 38. When the hole 34 is formed in the oxide film 35 by plasma etching, the hole in the mask film 37 is obtained. The inventor has obtained knowledge that the distortion of 38 is reflected in the hole 34.

  In the etching processing method according to the present embodiment, based on this knowledge, distortion of holes in the mask film is eliminated before forming holes in the oxide film.

  Hereinafter, the etching method according to the present embodiment will be described in detail.

  FIG. 3 is a cross-sectional view schematically showing the structure of a part of a wafer processed by the etching method according to the present embodiment.

In FIG. 3, a wafer W includes a silicon part 39 to be a base part, a SiO ₂ film 40 (etching target film) having a thickness of 2600 nm, for example, formed on the silicon part 39, and the SiO ₂ film 40. For example, a carbon film 41 having a thickness of 900 nm, a SiON film 42 formed on the carbon film 41, a BARC film (antireflection film) 43 formed on the SiON film 42, And a photoresist film 45 formed on the BARC film 43 and having a hole 44 (pattern) exposing the BARC film 43. The carbon film 41, the SiON film 42, the BARC film 43, and the photoresist film 45 are all organic films (organic films).

  FIG. 4 is a process diagram showing the etching method according to the present embodiment.

  In FIG. 4, first, the wafer W is placed on the susceptor 12 inside the chamber 11 and attracted and held by the electrostatic chuck 23 (FIG. 4A).

  Next, the inside of the chamber 11 is depressurized by the exhaust pipe 17, the internal pressure is set to, for example, 15 mTorr (1.96 Pa) by the APC valve, the flow rate is, for example, 300 sccm of CO gas, and the flow rate is, for example, A mixed gas with 300 sccm Ar (argon) gas is introduced into the processing chamber 15 from the shower head 26 and applied to the processing chamber 15 without applying DC power to the upper electrode plate 27, for example, for generating 200 W of plasma. And, for example, 300 W of high-frequency power for ion attraction is applied to the susceptor 12 (pattern shape improvement step).

  At this time, as shown in FIG. 5A, the mixed gas is excited by the high-frequency power for plasma generation to generate plasma, and the sheath 46 is formed on the surface of the wafer W due to the high-frequency power for ion attraction. Occur. The sheath is a plasma particle density resulting from a difference in the arrival speed of electrons and cations in the plasma to the wafer, in particular, a region where the electron density is low, and accelerates cations toward the wafer, while electrons move to the wafer. Stop progress.

  Here, since the output value of the high frequency power for ion attraction is relatively low, the generated sheath 46 is thin and does not accelerate the positive ions 47 in the plasma so much. Therefore, each cation 47 sputters the photoresist film 45 weakly. At this time, the skirt portion 44a and the protruding shape 44b of the hole 44 constituting most of the distortion of the hole 44 are preferentially sputtered and removed. In addition, radicals in the plasma are also preferentially reacted with the skirt portion 44a and the protruding shape 44b to remove them. As a result, the shape of the distorted hole 44 as shown in FIG. 5B is improved and approaches a perfect circle shape as shown in FIG.

When the shape of the hole 44 is improved, the mixed gas may be mixed with, for example, any one of O ₂ gas, CO ₂ gas, H ₂ / N ₂ gas, and NH ₃ gas instead of the CO gas described above. in addition, a rare gas if necessary, for example, may be further added Ar gas or O ₂ gas.

Further, the pressure inside the chamber 11, the output value of the applied high frequency power for plasma generation and high frequency power for ion attraction, and the flow rate of the mixed gas may be changed as necessary. For example, instead of the above-described mixed gas, a mixed gas of O ₂ gas having a flow rate of, for example, 5 sccm, COS gas having a flow rate of, for example, 10 sccm, and Ar gas having a flow rate of, for example, 300 sccm is used as the processing chamber 15. It may be introduced inside.

  Furthermore, you may apply DC power to the upper electrode plate 27 as needed. In this case, the electron density distribution in the plasma inside the processing chamber 15 is improved, and the shape of the hole 44 can be improved almost uniformly over the entire surface of the wafer W.

When the shape of the hole 44 is improved, the photoresist film 45 is etched until the diameter of the hole 44 becomes larger than a desired diameter in order to improve the shape of the hole 44 with certainty. Accordingly, the film thickness of the photoresist film 45 is also reduced. Therefore, when a hole 51 described later is formed in the SiO ₂ film 40 by plasma etching, the photoresist film 45 is formed before the depth of the hole 51 reaches a desired value. There is a risk of exhaustion.

In the etching processing method according to the present embodiment, the photoresist film 45, the BARC film 43, and the SiON film are formed after the hole 44 is shaped and before the hole 51 is formed in the SiO ₂ film 40. The film 42 and the carbon film 41 are cured. For example, as shown in FIG. 4B, a hardened layer 48 is formed on the surface of the photoresist film 45 or the like.

Here, after improving the shape of the hole 44, the pressure inside the chamber 11 is set to 50 mTorr (6.67 Pa), for example, by an APC valve, and the flow rate is, for example, 100 sccm of H ₂ gas, and the flow rate is, for example, , A mixed gas of 40 sccm of CF ₄ gas and Ar gas having a flow rate of, for example, 800 sccm is introduced into the processing chamber 15, and, for example, DC power of −900 V is applied to the upper electrode plate 27. For example, high-frequency power for plasma generation of 300 W is applied to the inside, while high-frequency power for ion attraction is not applied to the susceptor 12 (mask film curing step).

  At this time, as shown in FIG. 6A, not only plasma is generated from the mixed gas, but the upper electrode plate 27 emits electrons 49 to increase the electron density inside the processing chamber 15. Further, a self-bias voltage is generated on the wafer W due to the high-frequency power for generating plasma, and the sheath 50 on the surface of the wafer W is generated due to the self-bias voltage. The sheath 50 is extremely thin and hardly prevents the electrons 49 from traveling to the wafer W. Therefore, the electrons 49 inside the processing chamber 15 reach and come into contact with the BARC film 43 exposed in the photoresist film 45 and the holes 44. In general, since an organic film is cured when it comes into contact with electrons, a cured layer 48 is formed on the surface of the photoresist film 45 or the BARC film 43. Further, the electrons 49 are not only in contact with the photoresist film 45, but are also doped into the photoresist film 45 and the BARC film 43, SiON film 42 and carbon film 41 formed thereunder to cure these films.

Further, since CF ₄ gas is a deposition gas, the plasma of CF ₄ gas generates a deposit in the reaction with the photoresist film 45, and the deposit is formed on the surface of the photoresist film 45 and the BARC film 43, in particular, a hole. It adheres to the inner surface of 44. Thereby, the hole 44 having a large diameter as shown in FIG. 6B can be returned to the hole 44 having a desired diameter as shown in FIG. 6C.

When the photoresist film 45 or the like is cured, for example, a mixed gas of H ₂ gas and Ar gas, H ₂ gas, COS gas, and Ar is used instead of the mixed gas of H ₂ gas, CF ₄ gas, and Ar gas described above. A mixed gas of gas, COS gas, CF ₄ gas, and Ar gas may be used.

  Further, the pressure inside the chamber 11, the applied DC power and the output value of the high-frequency power for plasma generation, and the flow rate of the mixed gas may be changed as necessary. For example, DC power of −900 V or less is applied to the upper electrode. You may apply to the board 27. FIG. In this case, the amount of electrons emitted from the upper electrode plate 27 can be increased, and the absolute value of the potential difference between the wafer W and the upper electrode plate 27 can be secured above a predetermined value. As a result, the number of electrons that reach and come into contact with the photoresist film 45 and the BARC film 43 can be increased.

  In the etching method according to the present embodiment, the shape improvement of the hole 44 and the curing of the photoresist film 45 and the like described above are each performed once.

Next, after the photoresist film 45 and the like are cured, holes 51 to be described later are formed in the SiO ₂ film 40 by plasma etching, as shown in FIG.

Here, after the photoresist film 45 and the like are cured, the pressure inside the chamber 11 is set to, for example, 30 mTorr (4.00 Pa) by an APC valve, and the flow rate is, for example, 32 sccm of C ₄ F ₆ gas, Mixing of C ₄ F ₈ gas with a flow rate of, for example, 16 sccm, CF ₄ gas with flow rate of, for example, 24 sccm, Ar gas with a flow rate of, for example, 600 sccm, and O ₂ gas with a flow rate of, for example, 36 sccm Gas is introduced into the processing chamber 15, DC power of −300 V, for example, is applied to the upper electrode plate 27, and high-frequency power for generating plasma of 2200 W is applied to the processing chamber 15, for example, to the susceptor 12. For example, high frequency power for ion attraction of 7800 W is applied (target film etching step).

At this time, as shown in FIG. 7A, plasma is generated from the mixed gas, and electrons 53 are emitted from the upper electrode plate 27, but the wafer W is self-induced due to high-frequency power for ion attraction with high output. A bias voltage is generated, and a sheath 52 is generated on the surface of the wafer W due to the self-bias voltage. The sheath 52 is extremely thick and almost prevents the electrons 53 from traveling to the wafer W, while greatly accelerating the cations 54 in the plasma. Accordingly, each cation 54 strongly sputters the bottom of the hole 44, and in particular, the BARC film 43, the SiON film 42, and the carbon film 41 are etched inside the hole 44, and the exposed SiO ₂ film 40 is etched.

When the SiO ₂ film 40 is etched, the C ₄ F ₆ gas, the C ₄ F ₈ gas, the CF ₄ gas, the Ar gas, and the O ₂ gas are not mixed, but, for example, C ₄ F ₆ gas, Ar A mixed gas of gas and O ₂ gas, C ₄ F ₈ gas, Ar gas and O ₂ gas, C ₄ F ₆ gas, C ₄ F ₈ gas, Ar gas and O ₂ gas may be used, and If necessary, CF ₄ gas, C ₃ F ₈ gas or COS gas may be added.

Further, the pressure inside the chamber 11, the output value of the applied DC power, the output value of the high frequency power for plasma generation and the high frequency power for ion attraction, and the flow rate of the mixed gas may be changed as necessary. For example, the pressure inside the chamber 11, for example, set to 20 mTorr (2.67 Pa), flow rate, for example, a _C 4 _{F 6} gas 50 sccm, flow rate, for example, a _C 4 _{F 8} gas 20 sccm, flow rate However, for example, a mixed gas of Ar gas of 200 sccm and O ₂ gas of flow rate of, for example, 55 sccm is introduced into the processing chamber 15, and, for example, DC power of −300 V is applied to the upper electrode plate 27, For example, high frequency power for plasma generation of 1000 W may be applied to the inside of the processing chamber 15, and high frequency power for ion attraction of, for example, 7800 W may be applied to the susceptor 12.

Here, each cation 54 also strongly sputters the photoresist film 45, but since the photoresist film 45 is hardened, it is not consumed immediately. Even if the photoresist film 45 is consumed, the photoresist film 45 is also consumed. Since the BARC film 43, the SiON film 42, and the carbon film 41 formed below are also cured, these films are not consumed immediately. Thereby, the selection ratio of the photoresist film 45 etc. with respect to the SiO ₂ film 40 is maintained, and the photoresist film 45 etc. can maintain the function as a mask film for a predetermined period. As a result, holes 51 are formed at locations corresponding to the holes 44 in the SiO ₂ film 40.

Here, when the SiO ₂ film 40 is etched to increase the depth of the hole 51, the cation 54 accelerated by the sheath 52 and entered the hole 51 stays at the bottom of the hole 51. In the etching method according to the present embodiment, electrons 53 are positively introduced into the bottom of the hole 51 in order to electrically neutralize the staying cation 54. Specifically, high-frequency power for ion attraction and high-frequency power for plasma generation are applied in the form of pulse waves (target film etching step). More specifically, a first period in which both high frequency power for ion attraction and high frequency power for plasma generation are applied, and a second period in which both high frequency power for ion attraction and high frequency power for plasma generation are not applied. Control is performed such that the period is alternately repeated at a predetermined cycle. In other words, the high frequency power for plasma generation from the first high frequency power supply 18 is modulated and applied to the susceptor 12, and the high frequency power for ion attraction from the second high frequency power supply 20 is converted to the high frequency power for plasma generation. Modulated at the same timing as the modulation and applied to the susceptor 12. A typical example of the applied modulation corresponds to a pulse-like modulation as shown in FIG. Note that FIG. 13A typically shows a modulation state of application of high-frequency power for ion attraction. In FIG. 13A, a period in which the high frequency power for ion attraction is applied is period A, and a period in which the high frequency power for ion attraction is not applied is period B. In this typical example, ON / OFF of the high frequency power for ion attraction is repeated. The waveform of the high frequency power for ion attraction in this case is as shown in FIG.

  FIG. 8 is a diagram showing the relationship between the high frequency power for plasma generation, the high frequency power for ion attraction, and the current flowing near the surface of the wafer. In FIG. 8, the horizontal axis indicates time, and the vertical axis indicates power value or current value.

  In FIG. 8, when the high-frequency power 55 for plasma generation and the high-frequency power 56 for ion attraction are applied in the form of a pulse wave synchronously, the output of the high-frequency power 56 for ion attraction and the high-frequency power 55 for plasma generation is output. The value is 0, and a state in which the high frequency power 56 for ion attraction and the high frequency power 55 for plasma generation are not applied is positively created.

  When the high frequency power 56 for ion attraction and the high frequency power 55 for plasma generation are no longer applied, the sheath 52 disappears as shown in FIG. At this time, since the application of the negative potential DC power to the upper electrode plate 27 is continued, the electrons 53 generated by the incidence of cations on the upper electrode plate 27 are applied to the upper electrode plate 27. A state of being accelerated by the negative DC voltage and entering the hole 51 at a high speed without being blocked by the sheath 52 occurs. Thereby, the cation 54 staying at the bottom of the hole 51 is electrically neutralized.

  Here, the flow of electrons introduced to the bottom of the hole 51 is observed as a current flowing near the surface of the wafer. However, as shown in FIG. 8, a current 57 flowing near the surface of the wafer W is used for ion attraction. After the output values of the high-frequency power 56 and the plasma-generating high-frequency power 55 become zero, a short time, specifically, 5 μs has passed, and after a lapse of a short time, it flows in a spike, and then rapidly The current value of the current 57 decreases.

  After the output value of the high frequency power 56 for ion attraction becomes 0, the current 57 flows after 5 μs has elapsed after the output value of the high frequency power for ion attraction 56 becomes 0, It is considered that it takes about 5 μs for the electron temperature to sufficiently decrease and the sheath 52 to disappear. On the other hand, the current 57 flows in a moment, and then the current value of the current 57 rapidly decreases because of a rapid decrease in the cation density necessary for generating the electrons 53 emitted from the upper electrode plate 27. it is conceivable that. Therefore, in order to electrically neutralize the cation 54 that stays by introducing a certain amount of electrons 53 into the bottom of the hole 51, the output value of the high-frequency power 56 for ion attraction becomes zero, that is, The state in which the high-frequency power 56 for ion attraction is not applied may be continued for at least 5 μsec.

Therefore, it is not necessary to lengthen the state in which the output value of the high frequency power 56 for ion attraction etc. becomes zero with the high frequency power for plasma generation 55 and the high frequency power for ion attraction applied in the form of pulse waves. In other words, the duty ratio of the high frequency power 55 for plasma generation and the high frequency power 56 for ion attraction may be set high. Specifically, the duty ratio may be set to any of 10% to 90%, preferably 50% to 90%. In this case, since the duty ratio is 90% at the maximum, it is possible to surely create a state where the high frequency power 56 for ion attraction is not applied, so that the electrons 53 can be reliably introduced into the bottom of the hole 51. Further, since the sheath 52 disappears in a state where the high frequency power 56 for ion attraction is not applied, the spatter by the positive ions 54 is reduced and the etching efficiency of the SiO ₂ film 40 is reduced. In this case, the duty ratio is the lowest However, since it is 50%, the occurrence of the state in which the sheath 52 disappears can be moderately suppressed, and the etching efficiency of the SiO ₂ film 40 can be prevented from being lowered. In the etching method according to the present embodiment, the duty ratio is set to 70%.

  Further, since the frequency of the pulse wave (pulse frequency) of the high-frequency power 55 for plasma generation and the high-frequency power 56 for ion attraction is higher, the frequency at which the electrons 53 are introduced into the bottom of the hole 51 can be increased. Is preferably higher. On the other hand, if the frequency is too high, the state in which the high frequency power 56 for ion attraction is not applied cannot be maintained for a time necessary for the sheath 52 to disappear. Therefore, the frequency of the pulse wave of the high-frequency power 55 for plasma generation and the high-frequency power 56 for ion attraction may be 1 KHz to 50 KHz, and preferably 10 KHz to 50 KHz. . In the etching method according to the present embodiment, the frequency of the pulse wave is set to 10 KHz.

  In the etching method according to the present embodiment, since the application of the negative potential direct current power to the upper electrode plate 27 is continued even when the high frequency power 56 for ion attraction is not applied, the upper electrode plate The potential of 27 is also negative. On the other hand, if the high-frequency power 56 for ion attraction is not applied to the susceptor 12, almost no bias voltage is generated on the wafer W, so that the potential near the wafer W becomes almost zero. Accordingly, the absolute value of the potential difference between the wafer W and the upper electrode plate 27 can be secured to a predetermined value or more, and the potential difference guides the electrons 53 toward the wafer W. Therefore, the introduction of the electrons 53 into the bottom of the hole 51 is promoted. can do. Further, by continuing to apply the negative potential DC power to the upper electrode plate 27, it is possible to continue the emission of the electrons 53 from the upper electrode plate 27, thereby increasing the electron density inside the processing chamber 15. Thus, the probability that the electrons 53 are introduced into the bottom of the hole 51 can be improved.

  In the etching method according to the present embodiment, when the electrons 53 are introduced into the bottom of the hole 51, the output value of the high frequency power 56 for ion attraction is set to 0, but the wafer W and the upper electrode plate 27 If the absolute value of the potential difference can be secured at a predetermined value or more, the electrons 53 can be guided toward the wafer W, so that the output value of the high frequency power 56 for ion attraction need not necessarily be zero. . For example, when DC power of −300 V is applied to the upper electrode plate 27, the value of the high frequency power 56 for ion attraction may be set so that the bias voltage generated in the wafer W is higher than −300V.

Thereafter, continued application of the pulse wave of the high frequency power 56 for attracting the high-frequency power 55 and the ions for plasma generation, as shown in FIG. 4 (D), eliminates carbon film 41 is exhausted, the SiO ₂ film 40 For example, when the hole 51 having an aspect ratio of 30 or more is formed and the silicon part 39 is exposed at the bottom of the hole 51, the etching processing method according to the present embodiment is finished.

According to the etching method according to the present embodiment, since the shape of the hole 44 formed in the photoresist film 45 is improved, the shape of the hole 51 formed in the SiO ₂ film 40 is formed in the photoresist film 45. It is possible to prevent the shape defect (distortion or the like) of the formed hole 44 from being reflected.

Further, since the photoresist film 45 and the like are cured by the electrons 49, it is possible to prevent the photoresist film 45 from being consumed at an early stage when the SiO ₂ film 40 is etched by plasma, and thus the SiO ₂ film. At 40, the hole 51 can be reliably formed.

Further, when the SiO ₂ film 40 is etched by plasma, a negative potential direct current power is applied to the upper electrode plate 27, and a high frequency power 56 for ion attraction is applied to the susceptor 12 in the form of a pulse wave so as to attract ions. Therefore, a state in which a large amount of electrons 53 can be generated and the sheath 52 on the surface of the wafer W is extinguished can be created. Can be reliably introduced into the bottom of the hole 51 formed in the SiO ₂ film 40.

  As a result, even when the aspect ratio of the hole 51 to be formed is high, it is possible to prevent the side portion of the hole 51 from bulging and the hole 51 from being distorted.

Further, in the etching method according to the present embodiment, when the SiO ₂ film 40 is etched with plasma, the high frequency power 55 for generating plasma is also applied in the form of a pulse wave, and the high frequency power 55 for generating plasma is changed to the processing chamber 15. Since a state that is not applied to the inside is created, it is possible to reliably create a state in which the sheath 52 disappears.

  Further, in the etching processing method according to the present embodiment, the high frequency power 55 for plasma generation and the high frequency power 56 for ion attraction are synchronized and applied in the form of a pulse wave, so that the high frequency power 55 for plasma generation and the ions are applied. It is possible to create a state in which the high-frequency power 56 for drawing is not applied together, and thus it is possible to more reliably create a state in which the sheath 52 disappears.

  By the way, when the high frequency power 55 for plasma generation and the high frequency power 56 for ion attraction are continuously applied (hereinafter referred to as “continuous application”), as shown in FIG. In some cases, the deposits adhere to the carbon film 41 in the frontage 63 of the 51 and the protrusion 41a is formed, so that the frontage 63 becomes narrower.

  On the other hand, when the high-frequency power 55 for plasma generation and the high-frequency power 56 for ion attraction are synchronized and applied in the form of a pulse wave as in the present embodiment (hereinafter referred to as “pulse wave application”). As shown in FIG. 14B, the protruding portion 41a is not formed, and the frontage 63 is not narrowed.

  The present inventors conducted various verifications in order to elucidate the phenomenon described above. As a result, plasma generation depends on whether the high-frequency power 55 for plasma generation and the high-frequency power 56 for ion attraction are applied in synchronization. It was confirmed that the electron density and the electron temperature generated in the processing chamber 15 sometimes change. Specifically, as shown in FIG. 15, in the case of continuous application, the electron density maintains a high value without changing, whereas in the case of pulse wave application, the electron density is high-frequency power 56 for ion attraction. It decreases when no etc. is applied. It was also confirmed that the time for the electron density to decrease as the duty ratio decreases became longer. Furthermore, as shown in FIG. 16, in the case of continuous application, the electron temperature (more specifically, the emission intensity when the Ar gas in the mixed gas is excited) does not change and maintains a substantially constant value. On the other hand, in the case of pulse wave application, although the electron temperature rises for a moment, it has been confirmed that the time during which the electron temperature is lower is longer than that in the case of continuous application, and the time becomes longer as the duty ratio becomes smaller. That is, it was confirmed that the electron density and the electron temperature in the case of pulse wave application were lower than the electron density and the electron temperature in the case of continuous application when considered in terms of time on average.

  When the electron density or the electron temperature decreases, the dissociation of the mixed gas into radicals does not proceed and the degree of dissociation decreases. When the degree of dissociation decreases, the radical adhesion coefficient increases. Here, the radical adhesion coefficient is an index indicating the ease of adhesion to a layer when the radical collides with a certain layer. The radical easily adheres to a certain layer when the adhesion coefficient increases. When the degree of dissociation decreases, the radical adhesion coefficient increases. The decrease in the degree of dissociation indicates that the radical energy is low. When the radical energy is low, the radical only collides with a certain layer several times. It was thought that it was easy to lose energy and stay on the spot.

  That is, in the case of continuous application, since the electron density and the electron temperature are high, the degree of dissociation increases while the adhesion coefficient decreases. As a result, as shown in FIG. 17A, the radicals generated from the mixed gas, in particular, the CF-based radicals 64 lose only energy gradually even when they repeatedly collide with the surface of the carbon film 41. The radicals 64 do not adhere to the surface of the hole 41, and the radicals 64 lose the energy for rebounding from the carbon film 41 only after reaching the opening 63, and are directly attached to the carbon film 41 in the vicinity of the opening 63 as a deposit. Thereby, the frontage 63 becomes narrow.

  On the other hand, in the case of pulse wave application, since the electron density and the electron temperature are low, the degree of dissociation is lowered while the adhesion coefficient is increased. As a result, as shown in FIG. 17B, the CF radical 64 generated from the mixed gas easily loses energy when it collides with the surface of the carbon film 41 and adheres to the surface of the carbon film 41 as it is. The radical 64 does not reach the frontage 63 and the frontage 63 does not become narrow.

  That is, in the etching method according to the present embodiment, the high frequency power 55 for plasma generation and the high frequency power 56 for ion attraction are synchronized and applied in the form of pulse waves, so that the radicals 64 generated from the mixed gas are attached. The coefficient increases, and the radicals 64 adhere to the surface of the carbon film 41 without reaching the frontage 63. As a result, the opening 63 is not narrowed, and the cation 54 can smoothly enter the hole 51. Further, the cation 54 does not collide with the protrusion 41a and the course is not changed. Thereby, it is possible to reliably prevent the side portion of the hole 51 from bulging and the distortion of the hole 51 from occurring.

Since the possibility that the frontage 63 becomes narrow becomes lower as the adhesion coefficient of the radical 64 is higher, it is preferable that the adhesion coefficient of the radical 64 is higher. However, in general, higher-order CF-based gases such as C ₄ F ₆ gas and C _{4 Since 4} F ₈ gas has a higher adhesion coefficient of CF radicals generated than lower order CF-based gases, for example, CF ₂ gas and CF ₄ gas, C ₄ F ₆ is used as the CF-based gas in the mixed gas. It is preferable to use gas or C ₄ F ₈ gas. The adhesion coefficient of C ₄ F ₆ gas or C ₄ F ₈ gas is about 0.1 to 0.01, and the adhesion coefficient of CF ₂ gas or CF ₄ gas is about 0.01 to 0.0001.

  In the case of pulse wave application, the lower the duty ratio, the lower the electron density and electron temperature, and the higher the CF radical adhesion coefficient. Therefore, the duty ratio is preferably lower, for example, 70% or less, more preferably 50% or less. Thereby, possibility that the frontage 63 will become narrow can be made lower.

In the etching method according to the present embodiment described above, when the holes 51 are formed by plasma etching, C ₄ F ₆ gas, C ₄ F ₈ gas, CF ₄ gas, Ar gas, and O ₂ gas are used. Although the mixed gas is introduced into the processing chamber 15 and plasma is generated from the mixed gas, He (helium) gas may be mixed as a rare gas instead of Ar gas.

  When Ar gas cations are implanted into the upper electrode plate 27 made of silicon, the upper electrode plate 27 emits secondary electrons, but when He gas cations are implanted into the upper electrode plate 27 made of silicon, The electrode plate 27 emits more secondary electrons. Specifically, the secondary electron emission coefficient for implantation of He cation in silicon is 0.172, and the secondary electron emission coefficient for implantation of Ar cation in silicon is 0.024. Therefore, the amount of secondary electrons emitted from the upper electrode plate 27 can be increased by mixing He gas instead of Ar gas. As a result, when the hole 51 is formed, the number of electrons 53 penetrating into the hole 51 can be increased in the second period in which both the high frequency power for ion attraction and the high frequency power for plasma generation are not applied. Electrical neutralization of the cations 54 retained at the bottom of 51 can be performed reliably.

  It has been confirmed by the present inventors that when the He gas is excited, the electron temperature becomes higher than the electron temperature when the Ar gas is excited. Therefore, when the He gas is mixed with the mixed gas, the degree of dissociation becomes very high, and the radical adhesion coefficient is greatly reduced.

  When the adhesion coefficient of radicals is greatly reduced, as shown in FIG. 18, the radicals 65 adhere to the surface of the carbon film 41 because they lose only energy gradually even if they repeatedly collide with the surface of the carbon film 41. In addition, even when the radical 65 reaches the opening 63, energy is not yet lost, and therefore, the radical 65 does not adhere to the carbon film 41 in the vicinity of the opening 63 as a deposit, and enters the hole 51 toward the bottom. After that, the collision with the side wall of the hole 51 is repeated several times to lose energy, and the deposition thin film 41b is formed by adhering to the side wall of the hole 51 as a deposit. That is, since the frontage 63 does not become narrow, the cation 54 does not collide with the protrusion 41a and the course is not changed.

  Further, since the He cation has a significantly smaller mass than the Ar cation, even if it collides with the side wall of the hole 51, the side wall is not etched.

  As a result, it is possible to prevent the side portion of the hole 51 from bulging and the hole 51 from being distorted.

  Hereinafter, the etching method according to the second embodiment of the present invention will be described in detail.

  Since the configuration and operation of this embodiment are basically the same as those of the first embodiment described above, the description of the overlapping configuration and operation will be omitted, and the description of the different configuration and operation will be described below. Do.

  FIG. 9 is a cross-sectional view schematically showing a partial structure of a wafer processed by the etching method according to the present embodiment.

In FIG. 9, a wafer Wa includes a silicon part 39 as a base, a SiO ₂ film 40 (etching target film) having a thickness of 2600 nm, for example, formed on the silicon part 39, and a SiO ₂ film 40 And a residual film 59 made of SiO ₂ and formed on the polysilicon film 58. The polysilicon film 58 and the residue film 59 have holes 60 that expose the SiO ₂ film 40. The residue film 59 is made of a residue of a SiO ₂ film as a hard mask film used when forming the hole 60 in the polysilicon film 58. The polysilicon film 58 and the residue film 59 are all inorganic films (inorganic films).

  FIG. 10 is a process diagram showing the etching method according to the present embodiment.

  In FIG. 10, first, the wafer Wa is placed on the susceptor 12 inside the chamber 11 and attracted and held by the electrostatic chuck 23 (FIG. 10A).

Next, the inside of the chamber 11 is depressurized by the exhaust pipe 17, the internal pressure is set to 40 mTorr (5.33 Pa) by an APC valve, and the flow rate is, for example, 150 sccm of HBr gas, and the flow rate is, for example, A mixed gas of 5 sccm of O ₂ gas and NF ₃ gas having a flow rate of, for example, 7 sccm is introduced into the processing chamber 15 from the shower head 26, and the DC power is not applied to the upper electrode plate 27 without applying DC power to the processing chamber 15. For example, high-frequency power for generating plasma of 900 W is applied to the inside, and high-frequency power for ion absorption of, for example, 150 W is applied to the susceptor 12 (pattern shape improvement step).

  At this time, as shown in FIG. 11A, the mixed gas is excited to generate plasma, and a sheath 61 is generated on the surface of the wafer Wa. Again, since the output value of the high frequency power for ion attraction is relatively low, the generated sheath 61 is thin and does not accelerate the cations 62 in the plasma so much. Therefore, each cation 62 sputters the polysilicon film 58 and the residue film 59 weakly. At this time, the skirt 60a and the protruding shape 60b of the hole 60 constituting most of the distortion of the hole 60 are preferentially sputtered and removed. Further, radicals in the plasma are also preferentially reacted with the skirt 60a and the protruding shape 60b to remove them. As a result, the shape of the distorted hole 60 as shown in FIG. 11B is improved and approaches a perfect circle shape as shown in FIG.

When the shape of the hole 60 is improved, the mixed gas may be mixed with a halogen-based gas such as CF ₄ gas or Cl ₂ instead of the HBr gas or NF ₃ gas described above. If necessary, a rare gas such as Ar gas or O ₂ gas may be further added.

Further, the pressure inside the chamber 11, the output value of the applied high frequency power for plasma generation and high frequency power for ion attraction, and the flow rate of the mixed gas may be changed as necessary. For example, the pressure inside the chamber 11 is set to 10 mTorr (1.33 Pa), and instead of the mixed gas described above, the flow rate is, for example, 50 sccm of CF ₄ gas, the flow rate is, for example, 400 sccm, Ar gas, and the flow rate However, for example, a mixed gas of 20 sccm of O ₂ gas is introduced into the processing chamber 15, and a DC power is not applied to the upper electrode plate 27. For example, 500 W of high-frequency power for ion attraction may be applied to the susceptor 12.

  Furthermore, you may apply DC power to the upper electrode plate 27 as needed. In this case, the electron density distribution in the plasma inside the processing chamber 15 is improved, and the shape of the hole 60 can be improved almost uniformly over the entire surface of the wafer Wa.

Next, after improving the shape of the hole 60, as shown in FIG. 10B, the hole 51 is formed in the SiO ₂ film 40 by plasma etching. Processing conditions at this time, for example, the pressure inside the chamber 11, the type of mixed gas, the mixing ratio of various gases constituting the mixed gas, the output value of DC power applied to the upper electrode plate 27, and the high frequency power for plasma generation And the output value of the high frequency power for ion attraction are the same as those in the first embodiment, and in particular, the high frequency power for ion attraction and the high frequency power for plasma generation may be applied in a pulse wave shape. The frequency and duty ratio are the same as those in the first embodiment. Thereby, the hole 51 can be formed while electrically neutralizing the cation 54 staying at the bottom of the hole 51.

  At this time, since the polysilicon film 58 and the residue film 59 are less likely to be consumed by plasma than the photoresist film 45 and the like, the mask film can be formed in forming the holes 51 without curing the polysilicon film 58 and the residue film 59. Can be sufficiently described.

After that, as shown in FIG. 10D, when the polysilicon film 58 and the residue film 59 are consumed, the hole 51 is formed in the SiO ₂ film 40, and the silicon portion 39 is exposed at the bottom of the hole 51. The etching processing method according to the present embodiment is finished.

According to the etching method according to the present embodiment, since the shape of the hole 60 formed in the polysilicon film 58 and the residue film 59 is improved, the shape of the hole 51 formed in the SiO ₂ film 40 is changed to polysilicon. It is possible to prevent the shape defect (distortion or the like) of the hole 60 formed in the film 58 or the residue film 59 from being reflected.

Further, when the SiO ₂ film 40 is etched by plasma, a negative potential direct current power is applied to the upper electrode plate 27, and a high frequency power 56 for ion attraction is applied to the susceptor 12 in the form of a pulse wave so as to attract ions. This creates a state in which the high frequency power 56 is not applied to the susceptor 12, so that the electrons 53 can be reliably introduced into the bottom of the hole 51 formed in the SiO ₂ film 40.

  As a result, even when the aspect ratio of the hole 51 to be formed is high, it is possible to prevent the side portion of the hole 51 from bulging and the hole 51 from being distorted.

  In the etching method according to the present embodiment, when the hole 51 is formed by plasma etching, the polysilicon film 58 and the residue film 59 are used as a mask film. When these films are etched by plasma, The consumption of is small. Therefore, it is not necessary to cure the polysilicon film 58 and the residue film 59, and the efficiency of the etching method can be improved.

  In the etching processing method according to each of the above-described embodiments, the high frequency power for plasma generation and the high frequency power for ion attraction are synchronized and applied in the form of a pulse wave, but the sheath on the surface of the wafer W (Wa) These high frequency powers do not necessarily have to be applied in a synchronized manner if extinguishing conditions can be created.

Further, in the etching method according to each of the above-described embodiments, when the SiO ₂ film 40 is etched with plasma, not only the high frequency power for ion attraction but also the high frequency power for plasma generation is applied in a pulse waveform. If it is possible to create a state in which the sheath on the surface of the wafer W (Wa) disappears, the high-frequency power for generating the plasma does not necessarily have to be applied in the form of a pulse wave.

Further, an etching processing method according to each embodiment described above, SiO ₂ film 40, that is, holes in the oxide film by the etching plasma is applied when formed, a nitride film by etching the plasma, for example, This may be applied when holes are formed in the SiN film.

  The etching method according to each embodiment described above is applied to the substrate processing apparatus 10 in which the high frequency power for plasma generation and the high frequency power for ion attraction are applied to the susceptor 12, but the etching according to each embodiment is performed. The processing method may be applied to a substrate processing apparatus in which high frequency power for plasma generation is applied to the upper electrode plate and high frequency power for ion attraction is applied to the susceptor.

  The substrate on which the substrate processing apparatus that executes the etching processing method according to each of the above-described embodiments performs plasma etching processing is not limited to a wafer for semiconductor devices, but includes an FPD (Flat Panel Display) including an LCD (Liquid Crystal Display) and the like. For example, various substrates, photomasks, CD substrates, printed boards and the like may be used.

  As described above, the present invention has been described using the above embodiments, but the present invention is not limited to the above embodiments.

  An object of the present invention is to supply a computer or the like a storage medium that records a software program that implements the functions of the above-described embodiments, and the CPU of the computer reads and executes the program stored in the storage medium. Is also achieved.

  In this case, the program itself read from the storage medium realizes the functions of the above-described embodiments, and the program and the storage medium storing the program constitute the present invention.

  Examples of storage media for supplying the program include RAM, NV-RAM, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD (DVD-). Any optical disc such as ROM, DVD-RAM, DVD-RW, DVD + RW), magnetic tape, non-volatile memory card, other ROM, or the like may be used. Alternatively, the program may be supplied to the computer by downloading it from another computer or database (not shown) connected to the Internet, a commercial network, a local area network, or the like.

  Further, by executing the program read by the CPU of the computer, not only the functions of the above embodiments are realized, but also an OS (operating system) running on the CPU based on the instructions of the program. Includes a case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.

  Furthermore, after the program read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion board or This includes a case where the CPU or the like provided in the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

  The form of the program may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, and the like.

W, Wa Wafer 10 Substrate processing apparatus 12 Susceptor 15 Processing chamber 18 First high frequency power supply 20 Second high frequency power supply 40 SiO ₂ film 41 Carbon film 42 SiON film 43 BARC films 44, 51, 60 Hole 45 Photoresist film 55 Plasma High-frequency power for generation 56 High-frequency power for ion attraction 58 Polysilicon film 59 Residual film

Claims (18)

A processing chamber in which plasma is generated, a mounting table disposed in the processing chamber, and an electrode disposed in the processing chamber facing the mounting table, wherein the first in the processing chamber has a relatively high frequency. In the substrate processing apparatus, the second high frequency power having a frequency lower than that of the first high frequency power is applied to the mounting table, and the direct current power is applied to the electrode.
An etching method comprising: an etching target film; and a mask film formed on the etching target film, and performing an etching process on a substrate placed on the mounting table.
A pattern shape improving step for improving the shape of the pattern formed on the mask film on the substrate;
A target film etching step of forming a pattern on the etching target film by etching the etching target film with plasma using a mask film having an improved shape of the pattern ,
In the pattern shape improvement step, the mask film is etched with plasma,
In the target film etching step, the DC power is applied to the electrode, and at least the second high-frequency power is applied to the mounting table in the form of a pulse wave, while the DC power is applied to the electrode. By creating a state in which the second high-frequency power is not applied to the mounting table, the sheath generated on the surface of the substrate is extinguished and electrons generated from the electrode to which the DC power is applied enter the pattern. Etching method characterized by the above.   2. The etching method according to claim 1, wherein in the target film etching step, the first high-frequency power is also applied in a pulse wave shape to create a state in which the first high-frequency power is not applied to the inside of the processing chamber. .   3. The etching method according to claim 2, wherein in the target film etching step, the first high-frequency power and the second high-frequency power are applied in a pulse waveform in synchronization with each other.   4. The etching method according to claim 1, wherein, in the target film etching step, the DC power is applied to the electrode at a potential lower than a potential of a bias voltage generated in the substrate. 5. .   5. The device according to claim 1, wherein in the target film etching step, the second high-frequency power is applied to the mounting table in the form of a pulse wave having a frequency of 1 KHz to 50 KHz. Etching method.   The etching method according to claim 5, wherein the frequency is any one of 10 KHz to 50 KHz.   The duty ratio of the second high-frequency power applied in a pulse waveform in the target film etching step is any one of 10% to 90%. Etching method.   8. The etching processing method according to claim 7, wherein the duty ratio is any of 50% to 90%.   9. The etching method according to claim 1, wherein in the target film etching step, the state in which the second high-frequency power is not applied to the mounting table continues for at least 5 microseconds.   The etching method according to claim 1, wherein an aspect ratio of a pattern formed on the etching target film in the target film etching step is 30 or more. The mask film is an organic film,
The pattern shape improving step includes a mask film curing step in which electrons are brought into contact with the mask film etched with the plasma to cure the mask film. Etching method.   12. The etching method according to claim 11, wherein in the mask film curing step, the DC power is applied to the electrode.   13. The etching method according to claim 12, wherein in the mask film curing step, the voltage of the applied DC power is −900 V or less.   The etching processing method according to claim 11, wherein in the mask film curing step, plasma is generated from a deposition gas.   The etching method according to claim 1, wherein the mask film is an inorganic film.   The etching method according to claim 15, wherein the inorganic film includes at least a polysilicon film.   17. The pattern shape improvement step includes improving the shape of the pattern so that the shape of the hole of the mask film approaches a perfect circle when viewed from above. The etching treatment method according to item.   The etching method according to claim 1, wherein in the target film etching step, plasma is generated from a mixed gas containing at least helium gas.

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