JP4936709B2 - Plasma etching method and semiconductor device manufacturing method - Google Patents

Description

  The present invention relates to a plasma etching method and a semiconductor device manufacturing method in which an object to be processed such as a glass substrate for manufacturing a flat panel display (FPD) is etched using plasma of a processing gas.

  When manufacturing a thin film transistor (TFT) used in an FPD (flat panel display) typified by a liquid crystal display (LCD), a gate electrode is formed on a glass substrate, and gate insulation made of silicon nitride or the like is formed on the gate electrode. A film is formed. Then, a film for forming the semiconductor layer and the source and drain electrodes is sequentially formed thereon, and the source and drain electrodes and the channel portion are formed by etching.

  After the gate electrode and the source / drain electrode are formed as described above, the gate insulating film and the surface protective film (passivation film) are etched for the purpose of forming a contact hole for wiring connection. At this time, for the purpose of reducing mask consumption and manufacturing process, a plurality of contact holes having different depths, that is, contact holes connected to the gate electrode and contact holes connected to the source / drain electrodes are formed once. Forming with a mask pattern obtained by a photolithography process is performed (for example, Patent Document 1).

By the way, the source / drain electrodes have a structure in which Al, which is a low-resistance wiring material, AlNd is used as a base material, and molybdenum (Mo) or an alloy thereof is laminated as a barrier metal, for example, a Mo / Al / Mo structure, A Mo / AlNd / Mo structure is employed. In this case, the upper Mo layer is used for preventing spikes in the silicon nitride film and controlling the taper, and the lower Mo layer is used for preventing interdiffusion with Si serving as the underlying layer of the wiring layer. The upper Mo layer is usually formed as a thin film of about 50 nm in order to ensure shape controllability during wet etching.
JP 2003-224138 A

As described above, two types of contact holes having different depths, that is, a contact hole connected to the gate electrode and a contact hole connected to the source / drain electrode, are formed by the mask pattern obtained by one photolithography process. In the etching process, when a silicon nitride film as an etching target film is etched, a Mo layer is etched unless a sufficient etching selectivity is obtained with respect to Mo as a barrier metal on the upper layer of the source / drain electrode. It may disappear and adversely affect TFT characteristics and display characteristics. For this reason, conventionally, etching with a high etching rate and a high etching selectivity has been performed using a processing gas such as SF ₆ and O ₂ , SF ₆ and O ₂ and He, and SF ₆ and N ₂ .

However, in recent years, glass substrates for FPDs tend to increase in size, and those with long sides exceeding 2 m have appeared. As the substrate size increases, it becomes difficult to ensure sufficient etching selectivity throughout the substrate surface. FIG. 6 shows the substrate area when the plasma etching process is performed on the substrate G having a different size using SF ₆ / O ₂ / He gas, the etching selectivity of the silicon nitride film to the Mo film, and the Mo film. The relationship of the etching rate is shown. From FIG. 6, the etching rate of the Mo film increases as the substrate area increases, and conversely, the etching selectivity of the silicon nitride film (the etching rate of the silicon nitride film / the etching rate of the Mo film) tends to decrease. Can be read. In particular, when the substrate area is 27000 cm ² (1500 mm × 1800 mm), the etching selectivity of silicon nitride film / Mo film is less than 10 and the Mo film is etched at a high etching rate, which adversely affects the TFT characteristics. There is concern.

  Accordingly, the present invention provides an etching method capable of sufficiently obtaining an etching selectivity of a silicon nitride film with respect to a source / drain electrode including a refractory metal material film such as Mo even when processing a large glass substrate. With the goal.

In order to solve the above problems, a first aspect of the present invention is to provide a thin film transistor having a gate electrode including a refractory metal material film and a source / drain electrode including a refractory metal material film in a processing chamber of a plasma processing apparatus. The object to be processed is etched using plasma of a processing gas containing CF ₄ and O _2, and the silicon nitride film above the gate electrode and the source / drain electrodes is etched, A plasma etching method for forming a plurality of contact holes having different depths reaching the gate electrode and the source / drain electrodes at a time , wherein the refractory metal material film is a film made of molybdenum or a molybdenum alloy, The flow rate ratio between the CF ₄ gas and the O ₂ gas is
0% <[O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 30%
The plasma etching method is characterized by satisfying the above.

In the first aspect, the flow rate ratio between the CF ₄ gas and the O ₂ gas is:
2% ≦ [O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 20%
It is preferable to satisfy.
Further, a gate insulating film made of silicon nitride and a surface protective film made of silicon nitride are laminated on the gate electrode, and a surface protective film made of silicon nitride is formed on the source / drain electrodes. Well,
In the contact holes having different depths, the ratio of the depth D ₁ of the contact hole reaching the gate electrode and the depth D ₂ of the contact hole reaching the source / drain electrode is D ₁ : D ₂ = 1.8-3.0: 1 may be sufficient.
Further, the etching selectivity of the gate insulating film with respect to the source / drain electrodes is preferably 10 or more.
The flow rate of the CF ₄ gas, is preferably 2L / min or more.

Moreover, it is preferable to perform 10 to 50% overetching with respect to the main etching time.
Moreover, it is preferable that processing pressure is the range of 2-66.7Pa.
Further, the plasma processing apparatus is a parallel plate type plasma processing apparatus, and it is preferable that the plasma processing is performed by supplying a high frequency of 0.1 to 1.5 W per 1 cm ^{2 of} an object to be processed.

The object to be processed is preferably a flat panel display substrate. In this case, the area of the object to be processed is preferably 27000 cm ² or more.

  According to a second aspect of the present invention, there is provided a control program which operates on a computer and controls the plasma processing apparatus so that the plasma etching method according to the first aspect is performed at the time of execution. .

A third aspect of the present invention is a computer-readable storage medium storing a control program that runs on a computer,
The control program provides a computer-readable storage medium that controls the plasma processing apparatus so that the plasma etching method of the first aspect is performed at the time of execution.

According to a fourth aspect of the present invention, there is provided a processing chamber for performing a plasma etching process on an object to be processed;
A support for placing the object to be processed in the processing chamber;
Exhaust means for depressurizing the processing chamber;
Gas supply means for supplying a processing gas containing CF ₄ and O ₂ into the processing chamber;
A controller for controlling the plasma etching method of the first aspect to be performed in the processing chamber;
A plasma processing apparatus is provided.

A fifth aspect of the present invention is an object to be processed in which a thin film transistor having a gate electrode including a refractory metal material film and a source / drain electrode including a refractory metal material film is formed in a processing chamber of a plasma processing apparatus. In contrast, an etching process is performed using plasma of a processing gas containing CF ₄ and O _2, and the silicon nitride film above the gate electrode and the source / drain electrodes is etched. look including the step of forming a plurality of depth reaching to the drain electrode of different contact hole at a time, the high a melting point metal material film is made of molybdenum or molybdenum alloy layer, the said CF ₄ gas O ₂ gas The flow rate ratio is
0% <[O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 30%
A method for manufacturing a semiconductor device is provided.

According to the present invention, CF ₄ and O ₂ are included for an object to be processed on which a thin film transistor having a gate electrode including a refractory metal material film and a source / drain electrode including a refractory metal material film is formed. By performing the etching process using the plasma of the processing gas, the upper silicon nitride film can be etched with a high etching selectivity while suppressing the etching of the refractory metal material film on the surface of the source / drain electrode. Therefore, even on a large object to be processed such as an FPD glass substrate, a plurality of contact holes respectively reaching the underlying gate electrode and source / drain electrodes are etched once while ensuring in-plane uniformity of etching. It can be formed by processing.

Further, since the processing gas containing CF ₄ and O ₂ has a high etching selectivity of the silicon nitride film to the refractory metal material film, not only the refractory metal material film on the source / drain electrode surface but also the gate electrode surface Even when the refractory metal material film is exposed, etching of the refractory metal material film can be suppressed. Therefore, it is possible to perform sufficient over-etching on the object to be processed, and it is possible to ensure in-plane uniformity of etching, which has been difficult to realize particularly in a large-sized object to be processed.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a plasma etching apparatus for performing an etching method according to an embodiment of the present invention. The plasma etching apparatus 1 is configured as a capacitively coupled parallel plate plasma etching apparatus that performs etching on an FPD glass substrate (hereinafter referred to as “substrate”) G. Here, as the FPD, a liquid crystal display (LCD), a light emitting diode (LED) display, an electro luminescence (EL) display, a fluorescent display tube (VFD), a plasma display panel (PDP), and the like. Illustrated.

  This plasma etching apparatus 1 has a chamber 2 formed into a rectangular tube shape made of aluminum, for example, whose surface is anodized (anodized). A prismatic susceptor support 3 made of an insulating material is provided at the bottom of the chamber 2, and a susceptor for placing a substrate G, which is a substrate to be processed, on the susceptor support 3. 5 is provided. The susceptor 5 is made of aluminum that has been anodized (anodized) and functions as a lower electrode. An insulating member 4 is provided on the outer periphery and upper surface periphery of the susceptor 5.

  Further, the susceptor 5 is provided with an electrostatic adsorption mechanism for electrostatically adsorbing the substrate G and a gas flow path for supplying a heat medium gas to the back surface of the substrate G (none is shown).

  A power supply line 12 for supplying high frequency power is connected to the susceptor 5, and a matching unit 13 a and a first high frequency power supply 14 a are connected to the power supply line 12. For example, high frequency power of 13.56 MHz is supplied to the susceptor 5 from the first high frequency power supply 14a. By supplying power from the first high-frequency power source 14a, the processing gas is turned into plasma and bias power is supplied to the susceptor 5 which is the lower electrode. In addition, the second high frequency power supply 14b is connected to the feeder 12 of the first high frequency power supply 14a via a matching unit 13b. The second high frequency power supply 14b supplies a high frequency power having a frequency lower than that of the first high frequency power supply 14a, for example, 3.2 MHz, and is superimposed on the high frequency power for plasma formation.

  A shower head 15 that functions as an upper electrode is provided above the susceptor 5 so as to face the susceptor 5 in parallel. The shower head 15 is supported on the upper portion of the chamber 2, has a space 17 therein, and has a number of discharge holes 18 for discharging a processing gas on the surface facing the susceptor 5. The shower head 15 is grounded and forms a pair of parallel plate electrodes together with the susceptor 5.

A gas inlet 19 is provided on the upper surface of the shower head 15, and a gas supply pipe 20 is connected to the gas inlet 19. A processing gas supply mechanism 21 is connected to the gas supply pipe 20. Yes. A processing gas supply mechanism 21 includes a CF ₄ supply source 22 for supplying a CF ₄ gas, and a _{O 2} supply source 23 for supplying an _{O 2} gas. By using CF ₄ and O ₂ as processing gases, a stable discharge region is widened (specifically, etching can be performed under high pressure and low power conditions), so that stable etching processing is realized. .

Gas lines 22 a and 23 a are connected to the CF ₄ supply source 22 and the O ₂ supply source 23, respectively. These gas lines are connected to a gas supply pipe 20 so that gas from each supply source reaches the shower head 15 via each gas line and the gas supply pipe 20 and is discharged from the discharge hole 18 of the shower head. Yes. Each gas line is provided with a valve 32 and a mass flow controller 33.

  An exhaust pipe 34 is connected to the bottom of the side wall of the chamber 2, and an exhaust device 35 is connected to the exhaust pipe 34. The exhaust device 35 includes a vacuum pump such as a turbo molecular pump, and is configured so that the inside of the chamber 2 can be evacuated to a predetermined reduced pressure atmosphere. Further, a substrate loading / unloading port 36 and a gate valve 37 for opening and closing the substrate loading / unloading port 36 are provided on the side wall of the chamber 2, and a load lock chamber (adjacent to the substrate G with the gate valve 37 opened) ( (Not shown).

  Each component of the plasma etching apparatus 1 is connected to and controlled by a process controller 50 having a CPU. The process controller 50 includes a user interface 51 including a keyboard that allows a process manager to input commands to manage the plasma etching apparatus 1, a display that visualizes and displays the operating status of the plasma etching apparatus 1, and the like. It is connected.

  The process controller 50 stores a recipe in which a control program (software) for realizing various processes executed by the plasma etching apparatus 1 under the control of the process controller 50 and processing condition data are recorded. A storage unit 52 is connected.

  Then, if necessary, in response to an instruction from the user interface 51, an arbitrary recipe is called from the storage unit 52 and is executed by the process controller 50, so that the plasma etching processing apparatus 1 controls the process controller 50. The desired processing is performed. In addition, recipes such as the control program and processing condition data may be stored in a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a flash memory, or other recipes. It is also possible to transmit the data from the device at any time via, for example, a dedicated line and use it online.

Next, a processing operation when carrying out an embodiment of the present invention by the plasma etching apparatus 1 will be described.
As shown in FIG. 2, a substrate G on which a TFT is formed is prepared. In this substrate G, a gate electrode 102 is partially formed on a glass panel (substrate) 101. The gate electrode 102 includes a refractory metal material and has a structure in which a Mo layer 102a, an Al layer 102b, and a Mo layer 102c are stacked in order from the bottom. A gate insulating film 103 made of silicon nitride (Si ₃ N ₄ ) is formed on the entire surface of the gate electrode 102 and the glass panel 101. On the gate insulating film 103, an a-Si (amorphous silicon) film 104 is formed as a Si-based film for forming a transistor, and a channel portion 105 is formed above the gate electrode. On the a-Si film 104, a source electrode 106 and a drain electrode 107 containing Mo as a refractory metal material are formed. The source electrode 106 and the drain electrode 107 have a structure in which Mo layers 106a and 107a, Al layers 106b and 107b, and Mo layers 106c and 107c are stacked in this order from the bottom. A passivation film 108 made of silicon nitride (Si ₃ N ₄ ) is formed on the source electrode 106 and the drain electrode 107 to protect the surface of the TFT. As the refractory metal material, for example, molybdenum alloy, tungsten, tungsten alloy, or the like can be used in addition to molybdenum. Here, examples of the molybdenum alloy include molybdenum nitride and an alloy of titanium and molybdenum, and examples of the tungsten alloy include titanium / tungsten alloy, tungsten silicide, and tungsten nitride.

  First, after opening the gate valve 37, the substrate G having the above structure is loaded into the chamber 2 from a load lock chamber (not shown) via the substrate loading / unloading port 36 and placed on the susceptor 5. In this case, the transfer of the substrate G is performed by a lifter pin (not shown) that is inserted into the susceptor 5 so as to protrude from the susceptor 5. Thereafter, the gate valve 37 is closed, and the inside of the chamber 2 is evacuated to a predetermined degree of vacuum by the exhaust device 35, and the etching process is started.

For example, as shown in FIG. 3, the etching process is performed with the use of a pre-patterned photoresist film PR as a mask to form a plurality of contact holes having different depths at a time.
That is, a contact hole connected to the gate electrode 102 and a contact hole connected to the source / drain electrodes 106 and 107 by an etching process using the mask pattern of the photoresist film PR obtained by one photolithography process. Two types of contact holes having different depths are formed.

First, CF ₄ gas and O ₂ gas are introduced into the chamber 2 as processing gases at a predetermined flow rate. That is, the valves 32 of the CF ₄ supply source 22 and the O ₂ supply source 23 are opened, and the CF ₄ gas and the O ₂ gas are supplied to the gas supply pipe 20 and the gas inlet 19 while the flow rate is controlled to a predetermined amount by the mass flow controller 33. To the space 17 of the shower head 15. The processing gas is uniformly discharged from the space 17 to the substrate G through the discharge holes 18. Thereby, the inside of the chamber 2 is controlled to a predetermined pressure.

From the viewpoint of obtaining a sufficient etching selectivity, the flow rate of the CF ₄ gas is, for example, 0.2 to 0.4 L when the size of the substrate G is 3300 to 3900 cm ² (more specifically, about 3600 cm ² ). / Min (sccm), and preferably ² to 3 L / min (sccm) when the size of the substrate G is 25000 to 30000 cm ² (more specifically, about 27000 cm ² ). Further, when the size of the substrate G is 40000-45000 cm ² (more specifically, about 42000 cm ² ), it is preferably 3-4 L / min (sccm). Moreover, the pressure in the chamber 2 is preferably 2 to 66.7 Pa, more preferably 6.7 to 46.7 Pa, from the viewpoint of ensuring high selectivity in etching, shape controllability, and in-plane uniformity.

In this state, high-frequency power is applied from the first high-frequency power source 14a (and the second high-frequency power source 14b if necessary) to the susceptor 5 as the lower electrode via the matching unit 13a (matching unit 13b). A high-frequency electric field is generated between the susceptor 5 as an electrode and the shower head 15 as an upper electrode, and the processing gas is dissociated into plasma, whereby the substrate G is etched. The high frequency power is preferably set to 0.1 to 1.5 W per 1 cm ² area of the substrate G from the viewpoint of securing the etching rate, shape controllability, and in-plane uniformity.

By the etching process, the substrate G penetrates the passivation film 108 and the gate insulating film 103 as shown in FIG. 4 and passes through the hole 111 reaching the gate electrode 102 and the passivation film 108, for example, the drain electrode 107 (or the like). A hole 112 reaching the source electrode 106) is formed at a time.
Usually, when the thickness of the passivation film 108 is 1, the thickness of the gate insulating film 103 is about 0.8 to 2.0. Therefore, in the two types of holes 111 and 112 having different depths, the gate electrode 102 is formed. The ratio of the depth D ₁ of the hole 111 reaching the depth D ₂ and the depth D ₂ of the hole 112 reaching the drain electrode 107 (or the source electrode 106) is, for example, D ₁ : D ₂ = 1.8 to 3.0 : 1.

  After performing the etching process in this manner, the application of the high frequency power from the first high frequency power source 14a (and the second high frequency power source 14b) is stopped, the gas introduction is stopped, and then the pressure in the chamber 2 is set to a predetermined value. The pressure is reduced to Then, the gate valve 37 is opened, and the substrate G is unloaded from the chamber 2 to the load lock chamber (not shown) via the substrate loading / unloading port 36, thereby completing the etching process for the substrate G.

  As shown in FIG. 4, the hole 111 is formed by etching the passivation film 108 and the gate insulating film 103, and the hole 112 is formed by etching only the passivation film 108. Therefore, in order to form the holes 111 and 112 by batch etching, the etching process is continued even after the passivation film 108 is etched off and the holes 112 are formed, that is, even after the Mo layer 107c of the drain electrode 107 is exposed. It is necessary to. Therefore, the exposed Mo layer 107c of the drain electrode 107 is continuously exposed to plasma until the gate insulating film 103 is etched off and the hole 111 is formed.

In addition, as the size of the substrate has been increased, it is becoming difficult to ensure the uniformity of etching within the substrate surface, particularly with a large substrate of 27000 cm ² or more. In order to avoid this, sufficient over-etching is performed. This overetching is performed in a time of, for example, about 10 to 50% with respect to the main etching time determined based on the time until the gate insulating film 103 is etched off and the hole 111 is exposed. By performing over-etching in addition to main etching in this way, the exposed drain electrode 107 (or source electrode 106) is further exposed to plasma for a predetermined time.

For the above reasons, in order to simultaneously form the hole 111 and the hole 112 by etching on the substrate G having the TFT structure as illustrated in FIG. 4, the gate is formed on the Mo layer 107 c on the surface of the drain electrode 107. It is necessary to sufficiently increase the etching rate of silicon nitride (Si ₃ N ₄ ) constituting the insulating film 103, that is, to improve etching selectivity.

Therefore, in this embodiment, CF ₄ and O ₂ are used as process gases and the conditions of the plasma etching process are controlled, so that the source electrode 106 and the drain electrode 107 can be formed even on a large substrate of 1500 mm × 1800 mm size or more. It is possible to etch silicon nitride at a high selectivity of 10 or more with respect to Mo which is a material.

5 uses a plasma etching apparatus 1 having a configuration similar to that shown in FIG. 1 on a glass substrate having a TFT structure having the same structure as FIG. 2, and changes the flow rate ratio of the processing gas to perform plasma etching. The etching rate and the etching selectivity when processing is performed are shown. The numerical values in parentheses in the figure indicate the flow rate ratio and the etching rate or selection ratio at that time. The meaning of each plot is as follows.
S-SiN E / R: etching rate of the glass substrate S with respect to the silicon nitride film (gate insulating film 103).
S-Mo E / R: Etching rate for Mo (Mo layer 107c) of the glass substrate S.
L-SiN E / R: Etching rate with respect to the silicon nitride film (gate insulating film 103) of the glass substrate L.
L-Mo E / R: Etching rate for Mo (Mo layer 107c) of the glass substrate L.
S-Sel (SiN / Mo): etching selectivity of the silicon nitride film to Mo in the glass substrate S.
L-Sel (SiN / Mo): etching selectivity of the silicon nitride film to Mo in the glass substrate L.

In this test, two types of glass substrates (S, L) having different sizes were used. The plasma etching process conditions for each glass substrate are as follows. In this test, overetching of 20% with respect to the main etching time was performed after the main etching.
<Glass substrate S; size 550 mm × 650 mm>
Gap between upper and lower electrodes: 210mm
High frequency power: 1560W (13.56MHz)
Processing pressure: 20 Pa (150 mTorr)
Process gas flow rate: CF ₄ flow rate was fixed at 300 mL / min (sccm), and O ₂ flow rate was changed.
Lower electrode temperature: 25 ° C

<Glass substrate L; size 1500 mm × 1800 mm>
Gap between upper and lower electrodes: 210mm
High frequency power (2 frequency applied to the lower electrode): 6000 W (13.56 MHz) / 1500 W (3.2 MHz)
Processing pressure: 33.3 Pa (250 mTorr)
Process gas flow rate: CF ₄ flow rate was fixed at 2400 mL / min (sccm), and O ₂ flow rate was changed.
Lower electrode temperature: 25 ° C

From FIG. 5, it can be seen that in the case of the glass substrate S, if the percentage of the flow rate ratio O ₂ / (CF ₄ + O ₂ ) of the processing gas is in the range of 2% to 10%, the selection ratio is 10 or more. . Further, in the case of the glass substrate L, it can be read that the selection ratio is 10 or more when the percentage of the process gas flow rate ratio O ₂ / (CF ₄ + O ₂ ) is 20% or less.
Therefore, as a flow rate ratio of the processing gas,
0% <[O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 30%
Preferably,
2% ≦ [O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 20%
More preferably. When processing a large substrate G having a size of 27000 cm ² or more, the flow rate of the CF ₄ gas is preferably 2 L / min or more.

Next, SF ₆ / O ₂ / He or CF ₄ / O ₂ is used as a processing gas, and a glass substrate (size: 1500 mm × 1800 mm) having a TFT structure similar to that in FIG. 2 is shown in FIG. Etching was performed under the conditions shown in Table 1 using a plasma etching apparatus 1 having the same configuration as shown. The etching rate of the gate insulating film and the etching rate of Mo were measured, and the etching selectivity (the etching rate of the gate insulating film / the etching rate of Mo) was obtained. The results are also shown in Table 1.

From Table 1, good etching of 26.5 to 41.3 by using CF ₄ and O ₂ as processing gases at a flow rate ratio of [O ₂ / (CF ₄ + O ₂ )] × 100 = about 14% It has been shown that selectivity can be obtained. On the other hand, when SF ₆ type processing gas was used, the etching selectivity was about 10, and it was considered that it could not cope with the further increase in the size of the substrate.

Further, as in the above test, SF ₆ / O ₂ / He or CF ₄ / O ₂ was used as the processing gas, and a larger glass substrate having a TFT structure similar to that shown in FIG. 2 (size: 1870 mm × 2200 mm), the plasma etching apparatus 1 having the same configuration as that shown in FIG. 1 was used, and etching was performed under the following conditions.

<Example 4>
High frequency power: 12kW (13.56MHz)
Processing pressure: 26.7 Pa (200 mTorr)
Process gas flow rate: CF ₄ flow rate 3600 mL / min (sccm), O ₂ flow rate 600 mL / min (sccm)

<Comparative example 4>
High frequency power: 12kW (13.56MHz)
Processing pressure: 20 Pa (150 mTorr)
Process gas flow rate: SF ₆ flow rate 1500 mL / min (sccm), O ₂ flow rate 1500 mL / min (sccm), He flow rate 3000 mL / min (sccm)

The etching selectivity in this test was 10 for Comparative Example 4 and 23 for Example 4. From this result, for a large glass substrate (size: 1870 mm × 2200 mm), a high selection ratio can be obtained by using CF ₄ / O ₂ gas, but SF ₆ / O ₂ / He gas is sufficient. It was confirmed that the selectivity was not obtained.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.
For example, in the above embodiment, a capacitively coupled parallel plate etching apparatus is used. However, any apparatus can be used as long as it can form plasma with the gas species of the present invention. Can be used.

  The present invention can be suitably used in the manufacturing process of, for example, FPD.

Sectional drawing which shows schematic structure of a plasma etching apparatus. The drawing which shows the cross-sectional structure of the board | substrate with which the etching method of this invention is applied. The figure explaining the state which is carrying out the plasma etching process to the board | substrate. The figure which shows the cross-section of the board | substrate after a plasma etching process. The graph which shows the relationship between process gas flow ratio, an etching rate, and etching selectivity. The graph which shows the relationship between the etching rate by the conventional process gas, an etching selectivity, and a substrate area.

Explanation of symbols

1; plasma etching apparatus 2; chamber 5; susceptor 14a; first high-frequency power source 14b; the second RF power supply 15, showerhead to 21; processing gas supply mechanism 22; CF ₄ source 23; _{O 2} supply source 50; Process Controller 101; Glass panel 102; Gate electrode 102a; Mo layer 102b; Al layer 102c; Mo layer 103; Gate insulating film 104; a-Si film 105; Channel portion 106; Source electrode 106a; Mo layer 106b; Mo layer 107; drain electrode 107a; Mo layer 107b; Al layer 107c; Mo layer 108; passivation film

Claims (14)

CF ₄ and O ₂ for a target object on which a thin film transistor having a gate electrode including a refractory metal material film and source / drain electrodes including a refractory metal material film is formed in a processing chamber of the plasma processing apparatus. A plurality of depths reaching each of the gate electrode and the source / drain electrodes by etching the silicon nitride film above the gate electrode and the source / drain electrodes. A plasma etching method for forming different contact holes at a time ,
The refractory metal material film is a film made of molybdenum or a molybdenum alloy;
The flow rate ratio between the CF ₄ gas and the O ₂ gas is
0% <[O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 30%
The plasma etching method characterized by satisfy | filling . CF ₄ Gas and O ₂ The gas flow ratio is
2% ≦ [O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 20%
The plasma etching method according to claim 1, wherein: A gate insulating film made of silicon nitride and a surface protective film made of silicon nitride are laminated on the gate electrode, and a surface protective film made of silicon nitride is formed on the source / drain electrodes,
In the contact holes having different depths, the ratio of the depth D ₁ of the contact hole reaching the gate electrode and the depth D ₂ of the contact hole reaching the source / drain electrode is D ₁ : D ₂ = The plasma etching method according to claim 1 or 2 , wherein the ratio is 1.8 to 3.0: 1. 4. The plasma etching method according to claim 1, wherein an etching selectivity of the gate insulating film with respect to the source / drain electrodes is 10 or more. 5. The plasma etching method according to any one of claims 1 to _4, wherein a flow rate of the CF ₄ gas is 2 L / min or more. The plasma etching method according to any one of claims 1 to 5 , wherein over-etching is performed by 10 to 50% with respect to a main etching time. The plasma etching method according to any one of claims 1 to 6 , wherein a processing pressure is in a range of 2 to 66.7 Pa. 2. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is a parallel plate type plasma processing apparatus, and performs plasma processing by supplying a high frequency of 0.1 to 1.5 W per 1 cm < ² > of an object to be processed. the plasma etching method according to any one of 7. The plasma etching method according to claim 1, wherein the object to be processed is a flat panel display substrate. The plasma etching method according to claim 9 , wherein an area of the object to be processed is 27000 cm ² or more. A control program that operates on a computer and controls the plasma processing apparatus so that the plasma etching method according to any one of claims 1 to 10 is performed at the time of execution. A computer-readable storage medium storing a control program that runs on a computer,
The computer-readable program is characterized in that, when executed, the control program controls the plasma processing apparatus so that the plasma etching method according to any one of claims 1 to 10 is performed. Possible storage medium. A processing chamber for performing a plasma etching process on an object to be processed;
A support for placing the object to be processed in the processing chamber;
Exhaust means for depressurizing the processing chamber;
Gas supply means for supplying a processing gas containing CF ₄ and O ₂ into the processing chamber;
A control unit for controlling the plasma etching method according to any one of claims 1 to 10 to be performed in the processing chamber;
A plasma processing apparatus comprising: CF ₄ and O ₂ for a target object on which a thin film transistor having a gate electrode including a refractory metal material film and source / drain electrodes including a refractory metal material film is formed in a processing chamber of the plasma processing apparatus. A plurality of depths reaching each of the gate electrode and the source / drain electrodes by etching the silicon nitride film above the gate electrode and the source / drain electrodes. viewing including the step of forming a different contact hole at a time of of,
The refractory metal material film is a film made of molybdenum or a molybdenum alloy;
The flow rate ratio between the CF ₄ gas and the O ₂ gas is
0% <[O ₂ / (CF ₄ + O ₂ )] × 100 ≦ 30%
The manufacturing method of the semiconductor device characterized by satisfying these .

Images