JP2005055597A - Halftone phase shift mask manufacturing method and pattern transfer method - Google Patents

Abstract

A single-layer film of a translucent light-shielding layer made of any one of metal-silicon oxide, metal-silicon nitride, and metal-silicon oxynitride film, or a multilayer film made up of a transparent layer and a light-shielding layer To provide a manufacturing method that suppresses surface roughness and unevenness of the substrate surface of a halftone phase shift mask.
1) A single-layer film of a translucent light-shielding layer made of any one of metal-silicon oxide, metal-silicon nitride, and metal-silicon oxynitride on a transparent substrate, or a transparent layer and light shielding A multilayer film composed of layers is formed, and 2) the single layer film or the multilayer film is selectively removed by dry etching using an etching gas containing chlorine atoms.
[Selection] Figure 2

Description

  The present invention relates to a photomask for exposure transfer used in a photolithography process in a semiconductor manufacturing process, and in particular, by providing a phase difference between exposure light passing through the photomask, the resolution of the transfer pattern is reduced. The present invention relates to a method of manufacturing a halftone phase shift mask improved and a pattern transfer method using a photolithographic method using the photomask.

  In a semiconductor manufacturing process, a photomask is used as a mask for pattern exposure for forming a fine pattern on a silicon wafer or the like. One type of photomask is a phase shift mask using a phase shift method. The phase shift method is one of the techniques for improving the resolution when transferring a fine pattern, and has been actively developed.

  In principle, by providing a phase shift unit in adjacent areas on the mask so that the phase difference of the transmitted light is 180 degrees, the transmitted light is diffracted and interferes with each other, reducing the light intensity at the boundary. As a result, the resolution of the transfer pattern is improved. This has the effect of improving the resolution of the fine pattern and the effect of improving the depth of focus, which are remarkably superior to those of a normal photomask.

  A halftone phase shift mask has been developed as a kind of the phase shift mask as described above. A halftone phase shift mask is a mask pattern formed on a transparent substrate, which is composed of a transmissive part that transmits light with a strength that substantially contributes to exposure and a semi-transmissive part that does not substantially contribute to exposure. is there.

  By providing the semi-transmission part with the function of phase inversion of the transmitted light and the light-shielding function within the pattern within the sensitivity of the resist, the light passing through the vicinity of the boundary between the transmission part and the semi-transmission part is mutually The edge shape of the light intensity is steepened so as to cancel each other, and the resolution and depth of focus characteristics are improved, and the mask pattern is faithfully transferred onto the wafer.

  In recent years, in order to further improve the resolution of a pattern transferred onto a silicon wafer, a high-transmittance halftone mask in which the light transmittance at the semi-transmissive portion is increased has been proposed. The high-transmittance halftone mask has a high transmissivity in the semi-transmitting part, and the intensity of light that is transmitted with the phase reversed is also increased. For this reason, the phase canceling effect is enhanced, and the resolution at the time of pattern transfer to the silicon wafer is further improved.

  Furthermore, in order to cope with the shortening of the exposure wavelength accompanying the recent miniaturization of semiconductor patterns, a halftone mask corresponding to shorter wavelength exposure than before is required. In order to cope with a shorter wavelength, it is necessary to increase the transmissivity of the semi-transmissive portion at a short wavelength, and a material with higher transparency is selected, and the exposure wavelength at the exposure wavelength, which is the original optical characteristic of the phase shift mask, is selected. The amount of phase inversion and the transmittance are set so as to satisfy desired conditions.

  As a halftone phase shift mask, a pattern obtained by patterning a translucent light shielding layer or a halftone film comprising a transparent layer and a light shielding layer on a transparent substrate is generally used.

As a material for forming the halftone film, a single layer film or a multilayer film made of a nitride of metal and silicon, an oxide and an oxynitride is known (for example, Patent Document 1, Patent Document 2, Patent Document). 3 and Patent Document 4).

In order to pattern these halftone films, a method of forming a fine resist pattern on the film and performing dry etching using plasma is employed. As the etching gas at this time, a compound gas containing fluorine atoms having high reactivity with silicon, which is the main constituent element of the halftone film, is used.
JP-A-62-52550 JP-A 63-202748 JP-A-5-181257 JP-A-7-140635

  Patterns with excellent dimensional controllability and shape perpendicularity in the manufacturing process of half-tone phase shift masks consisting of single-layer films or multi-layer films of metal and silicon nitride, oxide and oxynitride described above. It is important to ensure the uniformity of the amount of phase inversion and the transmittance in the plane at the same time as it is important.

  However, in the dry etching method as described above, at the end of etching, the vicinity of the interface between the halftone film and the underlying transparent substrate is exposed to ions or radicals containing fluorine element in the plasma. At this time, a reaction product with low volatility formed by a constituent element of the halftone film having low reactivity with fluorine remains in the vicinity of the interface. Further, at the time of over-etching after completion of etching, ions or radicals containing fluorine accelerate etching of the transparent substrate.

  As a result of the above, roughening or unevenness occurs on the surface of the transparent substrate. Such surface roughness and unevenness on the surface of the transparent substrate cause variations in the phase inversion amount and transmittance of the obtained halftone phase shift mask, resulting in variations in resolution within the mask surface.

  The present invention provides a single-layer film of a translucent light-shielding layer composed of any of metal-silicon oxide, metal-silicon nitride, metal-silicon oxynitride film, or a multilayer film composed of a transparent layer and a light-shielding layer. Method and pattern for manufacturing a halftone phase shift mask that promotes an etching reaction at the end of dry etching and suppresses surface roughness and unevenness of the substrate by reducing etching of the quartz substrate surface during overetching It is an object to provide a transfer method.

The present invention provides a method for manufacturing a halftone phase shift mask,
1) A single layer film of a translucent light-shielding layer made of any of metal-silicon oxide, metal-silicon nitride, metal-silicon oxynitride on a transparent substrate, or a multi-layer consisting of a transparent layer and a light-shielding layer Forming a film;
2) a step of selectively removing the single layer film or the multilayer film by dry etching using an etching gas containing chlorine atoms;
A method for manufacturing a halftone phase shift mask.

Further, the present invention provides a method for producing a halftone phase shift mask,
1) A single layer film of a translucent light-shielding layer made of any of metal-silicon oxide, metal-silicon nitride, metal-silicon oxynitride on a transparent substrate, or a multi-layer consisting of a transparent layer and a light-shielding layer Forming a film;
2) A step of forming a resist film on the single layer film or the multilayer film, and forming a resist pattern by electron beam or laser beam drawing and development,
3) a step of selectively removing the single layer film or the multilayer film by dry etching using an etching gas containing chlorine atoms;
A method for manufacturing a halftone phase shift mask.

Further, the present invention provides a method of manufacturing a halftone phase shift mask according to the invention, the etching gas, chlorine (Cl ₂₎ gas 5～95Vol%, boron trichloride (BCl ₃₎ to consist 5～95Vol% A method of manufacturing a halftone phase shift mask characterized by the above.

  Further, the present invention is a pattern transfer method characterized in that a pattern is formed by exposure transfer by photolithography using a halftone phase shift mask manufactured by the method of manufacturing a halftone phase shift mask according to the above invention. is there.

  As described above, according to the present invention, the roughness of the opening surface and the occurrence of unevenness are suppressed by increasing the reactivity of the halftone film at the end of etching and reducing the reactivity with the quartz substrate at the time of overetching. A halftone phase shift mask is obtained.

  Therefore, it is possible to provide a halftone type phase shift mask in which the variation in the amount of phase inversion and the transmittance in the mask surface is reduced as compared with the conventional case, and the variation in the resolution in the surface is improved.

  Hereinafter, the present invention will be described based on embodiments.

  1A and 1B are sectional views showing an example of the structure of a halftone phase shift mask manufactured by the method of manufacturing a halftone phase shift mask according to the present invention. 2A to 2E are cross-sectional views showing an example of the manufacturing process of the halftone phase shift mask of the present invention.

  As shown in FIG. 1A, a first example of a halftone phase shift mask according to the present invention is a halftone having a two-layer structure of a light-shielding film pattern 12a and a transparent film pattern 13a on a transparent substrate 11. A film pattern 17a is formed.

  In the second example, as shown in FIG. 1B, a translucent light-shielding film pattern 14a is formed on a transparent substrate 11.

  As shown in FIG. 2, first, on a transparent substrate (quartz substrate) 21, for example, a halftone film 27 made of oxide, nitride, or nitride oxide made of zirconium and silicon is formed by sputtering. Form. Thereafter, a resist 25 is applied and a mask pattern is drawn by an electron beam or a laser beam. Further development processing is performed to form a resist pattern 25a (FIGS. 2A to 2C).

Examples of the material for forming the semitransparent light-shielding film, the transparent film, and the light-shielding film for the halftone film include an intermetallic compound (silicide) of a metal such as an alkali element or a transition element and silicon. Among these, silicides of group 4A to 6A elements called refractory metal silicides are important in terms of their characteristics. Among these metal silicides, materials for halftone phase shift masks include, for example, zirconium and silicon as main constituent elements.

  Other than zirconium, hafnium, titanium, molybdenum or the like is used as a main metal element, and materials containing two or more of them are listed.

  Note that a film containing chromium as a main component may be formed on the halftone film in order to further partially form a light shielding film pattern.

  Next, the formation film (halftone film 27) made of any one of metal-silicon oxide, metal-silicon nitride, and metal-silicon nitride oxide exposed from the resist pattern 25a is selectively removed by etching. As a result, a halftone film pattern (mask pattern) 27a is formed on the transparent substrate to produce a halftone phase shift mask (FIGS. 2D to 2E).

  On the other hand, when forming a film mainly composed of chromium on the halftone film, the resist pattern is used as a mask and the chromium film is etched using a mixed gas of chlorine and oxygen. The halftone film is selectively removed by etching using the pattern as a mask to form a pattern, thereby producing a halftone phase shift mask (not shown).

  The dry etching reaction proceeds in the process of introducing a gas containing halogen atoms, generating plasma, adsorption of radicals and molecules, generation of reactants by ion bombardment, and desorption thereof.

  In order to promote the reaction, conditions that generate highly volatile reaction products are advantageous, but on the other hand, side etching in the pattern side wall direction and isotropic etching reactions are likely to occur, so etching by pattern dimensions. In order to form a fine pattern that does not cause a difference in reaction (microloading), it is preferable to use a film made of a metal and silicon that generates an appropriate amount of low-volatile halide.

  In the dry etching of the halftone film 27 in the present invention, first, a halftone film pattern 27a having a good shape and size is formed under an etching condition using an etching gas containing fluorine atoms. Thereafter, etching using an etching gas containing chlorine atoms is performed when etching of the halftone film is completed and overetching is performed.

  A gas containing fluorine atoms is highly reactive with silicon forming a halftone film and forms a highly volatile substance, so that isotropic etching is likely to occur. On the other hand, in the reaction with the metal that is a constituent element of the halftone film, a low-volatile substance is often formed, and anisotropic etching is likely to occur.

  Therefore, in the halftone film as described above, etching with a gas containing fluorine atoms causes an etching reaction having an intermediate property between isotropic and anisotropic. A pattern with high perpendicularity can be formed.

  In many cases, the gas containing chlorine atoms forms a highly volatile substance in the reaction with the metal constituting the halftone film as described above as compared with the case where the gas containing fluorine atoms is used. In addition, in the reaction with a quartz substrate made of silicon or oxygen, a reaction product having a lower volatility is formed than when a gas containing fluorine atoms is used.

  Therefore, in the vicinity of the interface between the halftone film and the quartz substrate, by using a gas containing chlorine atoms, the etching reaction of the halftone film is likely to occur and the etching reaction of the quartz substrate is less likely to occur. The halftone film can be removed by etching without giving.

  Thus, in the present invention, the high volatility of the reaction product between the quartz substrate and the halftone film near the interface is used to promote the etching reaction at the end of etching after pattern formation by etching, and at the time of overetching. In order to suppress this reaction, the low reactivity of the quartz substrate made of Si and O and the low volatility of the reaction product are used.

  That is, the bond energy between two atoms of Si and O, between two atoms of Si and F, and between two atoms of Si and Cl is Si—O: 190 kcal / mol, Si—F: 148 kcal / mol, Si—Cl. : 99 kcal / mol, and it is estimated that Cl is less likely to occur than F in the etching reaction on the quartz substrate surface. The boiling points of these silicon halide reaction products under atmospheric pressure are SiF: −86 ° C. and SiCl: 58 ° C., and F generates a highly volatile reactant compared to Cl. Moreover, the boiling point of the reaction product of a metal, for example, zirconium, which is a constituent element of the halftone film is ZrF: 600 ° C., ZrCl: 331 ° C., and Cl is changed to F in the etching reaction of the halftone film near the interface. Compared to this, a highly volatile reactant is produced.

  Therefore, if the method of the present invention uses a gas containing Cl as an etching gas without using a gas containing F at the end of etching and at the time of overetching, the halftone film etching reaction at the end of dry etching is promoted. By reducing the etching of the exposed surface of the quartz substrate, which is the base during overetching, an effect of suppressing the occurrence of roughness and unevenness can be obtained.

  Hereinafter, the present invention will be described specifically by way of examples.

  A halftone film containing zirconium, silicon, oxygen and nitrogen as main components was formed on a quartz substrate by sputtering. Subsequently, a photoresist was coated on the halftone film of the quartz substrate, laser beam drawing was performed, and development processing was performed to form a resist pattern.

Next, the halftone film was selectively removed using a commercially available ICP photomask dry etching apparatus using the resist pattern as a mask. At this time, the etching rate of the halftone film was measured by changing the high frequency power from the bias power source (RIE power source). The dry etching conditions are as follows.
(Etching conditions)
Etching gas: BCl ₃ + Cl ₂
・ Gas pressure: 37.5mT
・ High frequency output: 50W, 100W, 150W, 200W, 250W (power supply for RIE), 500W (power supply for ICP)
The results are shown in FIG. In addition, resist patterning was performed on the quartz substrate in the same manner as described above, and the etching rate of the quartz substrate was measured. The results are shown in FIG.

As can be seen from FIG. 4, the halftone film can be etched at a sufficient rate by using a mixed gas of BCl ₃ and Cl ₂ . It can also be seen that etching can be performed at a sufficient rate by changing the high-frequency power from the bias power source. At this time, FIG.
As shown in FIG. 4, the etching rate of the quartz substrate is low.

A halftone film containing zirconium, silicon, oxygen and nitrogen as main components was formed on a quartz substrate by sputtering. Subsequently, an electron beam resist on the halftone film of the quartz substrate was coated, electron beam drawing was performed, and a development process was performed to form a resist pattern. Next, the halftone film was selectively removed using a commercially available ICP photomask dry etching apparatus using the resist pattern as a mask. The dry etching conditions are as follows.
(Etching conditions)
Etching gas: C ₂ F ₆ + O ₂
・ Gas pressure: 3mT
・ High frequency output: 50W (RIE power supply), 100W (ICP power supply)
The etching rate of the halftone film when the gas flow rate ratio under such etching conditions was changed was measured. The results are shown in FIG.

As shown in FIG. 6, it can be seen that etching can be performed at a sufficient rate by using a mixed gas of C ₂ F ₆ and O ₂ . It was also confirmed that the pattern shape and accuracy after etching were good.

  FIG. 3 is a process explanatory diagram of the third embodiment. First, a light-shielding film 32 was formed by forming a halftone film containing zirconium, silicon and nitrogen as main components on a transparent substrate. At this time, the thickness of the light-shielding film was 120 mm. Next, a transparent film 33 was formed on the light-shielding film by a reactive sputtering method using a zirconium silicide target and a silicon target in combination and adding an appropriate amount of oxygen to argon gas. The film thickness of the transparent film at this time was 650 mm.

  The optical constant of the light-shielding film 32 was previously confirmed by preliminary experiments, and the refractive index n = 2.084 and the extinction coefficient k = 1.106. Similarly, the optical constants of the transparent film 33 were refractive index n = 2.092 and k = 0.336.

  Thus, by using a zirconium silicide target on a quartz substrate and forming a two-layer film with a transparent film as the upper layer and a light-shielding film as the lower layer, the phase inversion amount for ArF laser exposure light (wavelength 193 nm) is 179. .18 deg. A blank for halftone phase shift mask corresponding to VUV exposure having a transmittance of 6.09% was obtained.

  Next, a halftone phase shift mask was produced using the blank for halftone phase shift mask obtained as described above. First, a chromium layer 36 mainly composed of chromium was formed on the halftone film by sputtering. Further, a positive resist 35 containing an organic substance as a main component was applied, and after drying, the pattern forming portion was exposed with an electronic drawing apparatus. Thereafter, development was performed with an organic solvent to form a desired resist pattern 35a (FIGS. 3A to 3C).

Next, as shown in FIG. 3D, the chrome layer pattern 36a was selectively removed by using a commercially available dry etching apparatus for a photomask, using the resist pattern 35a as a mask. Thereafter, the halftone film 37 was selectively removed by etching using the resist pattern 35a and the chromium layer pattern 36a as a mask to obtain a halftone film pattern 37a as shown in FIG. The dry etching conditions are as follows. An ICP type apparatus was used as the dry etching apparatus.
(Chrome layer)
Etching gas: Cl ₂ + O ₂
・ Gas pressure: 10mT
・ High frequency output: 5W (RIE power supply), 350W (ICP power supply)
(Halftone film)
Etching gas: C ₂ F ₆ + O ₂
・ Gas pressure: 3mT
・ High frequency output: 50W (RIE power supply), 100W (ICP power supply)
(Over-etching)
Etching gas: BCl ₃ + Cl ₂
・ Gas pressure: 5mT
-High frequency output: 75W (RIE power supply), 100W (ICP power supply)

A halftone film containing zirconium, silicon, oxygen and nitrogen as main components was formed on a quartz substrate by sputtering. Subsequently, an electron beam resist on the halftone film of the quartz substrate was coated, electron beam drawing was performed, and a development process was performed to form a resist pattern. Next, the halftone film was selectively removed using a commercially available ICP photomask dry etching apparatus using the resist pattern as a mask. The dry etching conditions are as follows.
(Etching conditions)
Etching gas: BCl ₃ + Cl ₂
Gas flow ratio: BCl ₃ / Cl ₂ = 50/0 SCCM, 47.5 / 2.5, 40/10 SCCM, 30/20 SCCM, 20/30 SCCM, 10/40 SCCM, 2.5 / 47.5, 0/50 SCCM
The results are shown in FIG. In addition, resist patterning was performed on the quartz substrate in the same manner as described above, and the etching rate of the quartz substrate was measured. The results are shown in FIG.

As shown in FIG. 9, when the BCl ₃ / Cl ₂ gas flow rate ratio is changed, the etching rate of the halftone film tends to be increased by using 5% by volume to 95% by volume of BCl ₃ gas. . On the other hand, as shown in FIG. 10, since there is no change in the etching rate of the quartz substrate, the etching reaction of the halftone film is promoted and the etching reaction of the quartz substrate is suppressed at the gas flow rate ratio. I understand.

The etching reaction of the halftone film is suppressed when the mixing ratio of BCl ₃ gas in the BCl ₃ / Cl ₂ mixed gas is about 5% by volume or 95% by volume. Thus, BCl ₃ / Cl ₂ gas flow rate ratio of the over-etching conditions of Example 3, it is preferable to set the BCl ₃ gas flow rate below 5 volume% to 95 volume%.

  In the first to fourth embodiments, a halftone film mainly composed of zirconium, silicon, oxygen, and nitrogen is used. However, in addition to zirconium, a halftone equivalent to these embodiments is also used when a metal such as tantalum or niobium is used. A mold phase shift mask can be produced.

A halftone phase shift mask was manufactured in the same process as in Example 3 except that overetching of the halftone film was performed under the following conditions.
(Over-etching)
Etching gas: C ₂ F ₆ + O ₂
・ Gas pressure: 3mT
・ High frequency output: 70W (power supply for RIE), 100W (power supply for ICP)
With respect to the obtained halftone phase shift mask of Example 3 and Example 5 after removing the resist pattern and the chromium layer pattern, an opening (overetched portion) including the phase shift mask pattern was observed with an electron microscope. As a result, an electron micrograph of the halftone phase shift mask of Example 3 shown in FIG. 7 and an electron micrograph of the halftone phase shift mask of Example 5 shown in FIG. 8 were obtained.

  As is apparent from FIGS. 7 and 8, in the halftone phase shift mask of Example 5 using a gas containing fluorine at the time of over-etching, roughness and irregularities on the quartz substrate surface can be seen on the opening surface. On the other hand, it can be seen that the halftone phase shift mask of Example 3 using a gas containing chlorine at the time of overetching has no smooth surface or unevenness on the surface of the quartz substrate and has a smooth opening surface.

It is sectional drawing of the example of the halftone type | mold phase shift mask of this invention. It is sectional drawing of an example of the manufacturing process of the halftone type phase shift mask of this invention. 6 is a process explanatory diagram of Example 3. FIG. It is explanatory drawing which shows the relationship between the bias electric power in Example 1, and the etching rate of a halftone film. It is explanatory drawing which shows the relationship between the bias electric power in Example 1, and the etching rate of a quartz substrate. FIG. 6 is an explanatory diagram showing a change in etching rate of a halftone film in Example 2. Electron micrograph of the opening of the halftone phase shift mask produced in Example 3 Electron micrograph of the opening of the halftone phase shift mask produced in Example 5 It is explanatory drawing which shows the change of the etching rate of the halftone film in Example 4. FIG. It is explanatory drawing which shows the change of the etching rate of the quartz substrate in Example 4. FIG.

Explanation of symbols

11, 21, 31 ... Transparent substrate (quartz substrate)
12, 22, 32, ..., light-shielding films 12a, 22a, 32a, ..., light-shielding film patterns 13, 23, 33, ..., transparent films 13a, 23a, 33a, ..., transparent film patterns 14... Translucent light-shielding film 14 a... Translucent light-shielding film pattern 25, 35... Resist 25 a, 35 a ... resist pattern 36. Chrome layer pattern 17a ... halftone film pattern 27, 37 ... halftone film 27a, 37a ... halftone film pattern (mask pattern)

Claims (4)

In the manufacturing method of the halftone type phase shift mask,
1) A single layer film of a translucent light-shielding layer made of any of metal-silicon oxide, metal-silicon nitride, metal-silicon oxynitride on a transparent substrate, or a multi-layer consisting of a transparent layer and a light-shielding layer Forming a film;
2) a step of selectively removing the single layer film or the multilayer film by dry etching using an etching gas containing chlorine atoms;
A method for producing a halftone phase shift mask, comprising: In the manufacturing method of the halftone type phase shift mask,
1) A single layer film of a translucent light-shielding layer made of any of metal-silicon oxide, metal-silicon nitride, metal-silicon oxynitride on a transparent substrate, or a multi-layer consisting of a transparent layer and a light-shielding layer Forming a film;
2) A step of forming a resist film on the single layer film or the multilayer film, and forming a resist pattern by electron beam or laser beam drawing and development,
3) a step of selectively removing the single layer film or the multilayer film by dry etching using an etching gas containing chlorine atoms;
A method for producing a halftone phase shift mask, comprising: The etching gas is chlorine (Cl ₂₎ gas 5～95Vol%, boron trichloride (BCl ₃₎ according to claim 1 or claim 2 halftone type phase shift mask according to, comprising the 5～95Vol% Manufacturing method.   A pattern transfer method, wherein a pattern is formed by exposure transfer by a photolithography method using the halftone phase shift mask manufactured by the method of manufacturing a halftone phase shift mask according to claim 1, 2 or 3 .