JP2002341515A - Phase shifting mask blank, and method for producing phase shifting mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high quality phase shifting mask blank having high intrasurface uniformity of a phase shifting film and improved chemical resistance by using a target containing a metal, silicon and silicon oxide when the phase shifting film containing the metal, silicon, oxygen and nitrogen is produced by sputtering. SOLUTION: In the method for producing the phase shifting mask blank by disposing one or more phase shifting films containing a metal, silicon, oxygen and nitrogen on a transparent substrate, the phase shifting films are deposited by reactive sputtering in a nitrogen-containing atmosphere using a target containing the metal, silicon and silicon oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor integrated circuit,
The present invention relates to a phase shift mask blank and a method of manufacturing a phase shift mask used for fine processing of a CCD (charge coupled device), an LCD (liquid crystal display device), a magnetic head, and the like. The present invention relates to a halftone type phase shift mask blank and a method of manufacturing a phase shift mask which can attenuate the intensity of the phase shift mask.

[0002]

2. Description of the Related Art Photomasks used for a wide range of applications, including the manufacture of semiconductor integrated circuits such as ICs and LSIs, basically include a light-shielding film containing chromium as a main component on a light-transmitting substrate. It is formed in a predetermined pattern.
In recent years, pattern miniaturization has rapidly progressed in response to market requirements such as higher integration of semiconductor integrated circuits, and this has been responded to by shortening the exposure wavelength.

[0003] However, while shortening the exposure wavelength improves the resolution, it causes a decrease in the depth of focus, lowers the stability of the process, and adversely affects the product yield.

In order to solve such a problem, there is a phase shift method as one of effective pattern transfer methods, and a phase shift mask is used as a mask for transferring a fine pattern.

This phase shift mask (halftone type phase shift mask) is formed by pattern-forming a phase shifter 2 on a substrate 1 as shown in FIGS. 6A and 6B, for example. The light transmitted through both the substrate exposed portion (first light transmitting portion) 1a where no phase shifter film exists and the phase shifter portion (second light transmitting portion) 2a forming the pattern portion on the mask. By setting the phase difference to 180 degrees as shown in FIG. 6B, the light intensity at the interference portion becomes zero due to interference of light at the pattern boundary portion, and the contrast of the transferred image can be improved. Things. Also, by using the phase shift method, it is possible to increase the depth of focus when obtaining the required resolution, compared to the case where a normal mask having a general exposure pattern made of a chrome film or the like is used. It is possible to improve the resolution and the margin of the exposure process.

The above-mentioned phase shift masks can be practically classified into a complete transmission type phase shift mask and a halftone type phase shift mask depending on the light transmission characteristics of the phase shifter. The perfect transmission type phase shift mask is
The light transmittance of the phase shifter is equivalent to that of the substrate, and the mask is transparent to the exposure wavelength. On the other hand, in a halftone phase shift mask, the light transmittance of the phase shifter is about several% to several tens% of the exposed part of the substrate.

FIG. 1 shows a basic structure of a halftone type phase shift mask blank, and FIG. 2 shows a basic structure of a halftone type phase shift mask. The halftone type phase shift mask blank shown in FIG. 1 has a halftone type phase shift film 2 formed on a substrate 1 transparent to exposure light. The halftone type phase shift mask shown in FIG. 2 has a halftone type phase shifter portion 2a for patterning the shift film 2 to form a pattern portion on the mask, and a substrate exposed portion having no phase shift film. 1a
Is formed.

Here, the exposure light transmitted through the phase shifter 2a is shifted in phase with respect to the exposure light transmitted through the substrate exposed portion 1a (see FIGS. 6A and 6B). Further, the exposure light transmitted through the phase shifter 2a has such a light intensity that the resist on the substrate to be transferred is not exposed to the resist.
The transmittance of the phase shifter 2a is set. Therefore, the phase shifter 2a has a function of substantially blocking the exposure light.

As the halftone type phase shift mask, a single layer type halftone type phase shift mask having a simple structure has been proposed. As such a single layer type halftone type phase shift mask, tungsten silicide is used. And those having a phase shift film made of an oxide or oxynitride of metal and silicon such as molybdenum silicide and tantalum silicide (Japanese Patent Application Laid-Open No. 7-1406).
No. 35 gazette).

As a method of manufacturing such a phase shift mask, a method of patterning a phase shift mask blank by lithography is used. In this lithography method, a resist is applied on a phase shift mask blank, a desired portion of the resist is developed by exposure to an electron beam or ultraviolet light and then developed, and after exposing the phase shift film surface, the patterned resist film is used as a mask. A desired portion of the phase shift film is etched to expose the substrate. Thereafter, the resist film is peeled off to obtain a phase shift mask.

[0011]

By the way, in the above-mentioned phase shift film, a phase shift film containing an oxide is formed in order to increase the transmittance. It is performed by reactive sputtering using oxygen as a sputtering gas using a target. However, when oxygen is used for the sputtering gas, the oxygen reacts with the film formed on the target or the shield due to high reactivity of oxygen, or the oxygen gas concentration near the oxygen gas inlet increases,
Since oxygen according to the atmospheric oxygen concentration is taken into the film, the oxygen content is distributed in the plane, and the higher the oxygen content, the higher the transmittance and the lower the refractive index of the film. However, there is a problem that the uniformity of the film decreases. Further, there is also a problem that it is susceptible to an acid such as sulfuric acid used as a pretreatment or a cleaning liquid in cleaning or the like in a mask manufacturing process, and has insufficient chemical resistance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a phase shift mask blank having in-plane uniformity of optical characteristics and chemical resistance, and a method of manufacturing the phase shift mask. I do.

[0013]

Means for Solving the Problems and Embodiments of the Invention As a result of intensive studies to solve the above problems, the present inventor has found that a phase shift film containing metal, silicon, oxygen and nitrogen is formed on a transparent substrate. In a method for manufacturing a phase shift mask blank comprising one or more layers, a target containing a metal, silicon and silicon oxide is used as a target, and reactive sputtering is performed in an atmosphere containing nitrogen, so that an optical in-plane of the phase shift film is formed. It has been found that a phase shift film having uniform chemical properties and chemical resistance can be obtained, and the present invention has been accomplished.

That is, the present invention provides the following method for manufacturing a phase shift mask blank and a phase shift mask. Claim 1: A method for manufacturing a phase shift mask blank comprising one or more phase shift films containing metal, silicon, oxygen and nitrogen on a transparent substrate, wherein the phase shift film uses a target containing metal, silicon and silicon oxide. And forming a film by reactive sputtering in an atmosphere containing nitrogen. In a preferred embodiment, the metal is molybdenum. In a preferred embodiment, the content of the silicon oxide in the target is 3 to 20% in a molar ratio. In a preferred embodiment, the total of silicon and silicon oxide in the target is in a molar ratio of 60 to 90%, and the method of manufacturing a phase shift mask blank according to any one of claims 1 to 3. Preferably, the phase shift film converts the phase of the transmitted exposure light by 180 ± 5 degrees and has a transmittance of 3 to 40%. Manufacturing method of mask blank. (6) A method for manufacturing a phase shift mask, wherein the phase shift mask blank obtained by the method according to any one of (1) to (5) is patterned by lithography.

According to the present invention, when a phase shift film is formed by a sputtering method, a target containing a metal, silicon and silicon oxide is used as a target, nitrogen is used as a sputtering gas, and oxygen-free or almost no oxygen is used. By forming a film in an atmosphere, it is possible to obtain a transmittance sufficient to function as a halftone type phase shift mask without using a highly reactive oxygen gas for film formation. In addition, the chemical properties can be uniform in the plane and the chemical resistance can be improved.

Hereinafter, the present invention will be described in more detail. In the phase shift mask blank of the present invention, as shown in FIG. 1, one or more phase shift films containing metal, silicon, oxygen and nitrogen are provided on a transparent substrate 1 through which exposure light such as quartz or CaF ₂ is transmitted. In the method for manufacturing a phase shift mask blank, a phase shift film 2 is formed by reactive sputtering using a target containing metal, silicon and silicon oxide as a target and using nitrogen as a sputtering gas.

Here, in the phase shift including the metal, silicon, oxygen and nitrogen according to the present invention, the metals include W,
Mo, Ti, Ta, Zr, Hf, Nb, V, Co, Cr
Or Ni, etc., of which molybdenum (Mo) is preferable.

The composition of the phase shift film of the present invention is 5 to 25 atomic%, particularly 5 to 20 atomic%, metal such as molybdenum, 10 to 50 atomic%, particularly 20 to 50 atomic%, and 1% oxygen.
It is preferable that the content of the nitrogen atom is 70 to 70 atomic%, particularly 3 to 30 atomic%, nitrogen is 5 to 70 atomic%, particularly 20 to 60 atomic%.

Further, the phase shift film according to the present invention is formed on a transparent substrate by reactive sputtering using at least a metal, silicon and silicon oxide as a target, and has a transmittance of several percent to several tens of exposure light. % (Especially 3-4
0%), and the phase of the light transmitted through the phase shifter is 1% of the light transmitted only through the transparent substrate.
It is preferable to have a phase difference of 80 ± 5 degrees.

As a method of forming the phase shift film of the present invention, the reactive sputtering method is preferable as described above. In this case, a target containing metal, silicon and silicon oxide may be used. Is partially or entirely metal silicide, particularly preferably silicon and metal silicide, which contains silicon oxide. For example, to produce a target by a sintering method, metal, silicon, and silicon oxide are mixed and sintered so as to have a predetermined composition.
Alternatively, a metal silicide and silicon oxide, or a metal silicide, silicon, and silicon oxide may be mixed so as to have a predetermined composition and sintered by hot pressing or HIP.

If the content of silicon oxide in the target is too small, a predetermined transmittance of the phase shift film cannot be obtained. If the content is too large, there is a problem that a large amount of dust is generated and particles are generated. The amount is preferably 3 to 20%, especially 3 to 15% by molar ratio. Further, it is preferable that the total of silicon and silicon oxide in the target be 60 to 90%, particularly 75 to 90% by mole ratio. If it is less than 60%, a predetermined transmittance of the phase shift film cannot be obtained, and if it exceeds 90%, dust is easily generated during the film formation, which causes a defect. The types of metals are W, M
o, Ti, Ta, Zr, Hf, Nb, V, Co, Cr or Ni, among which molybdenum (Mo) is preferable from the viewpoint of etching resistance and chemical resistance.

As the sputtering method, direct current (DC)
A power source or a radio frequency (RF) power source may be used, and a magnetron sputtering method or a conventional method may be used. In addition,
The film forming apparatus may be a passing type or a single-wafer type.

The sputtering gas used for forming the phase shift film is preferably a sputtering gas containing nitrogen, particularly a sputtering gas containing nitrogen substantially containing no oxygen. As an introduction method, nitrogen alone or a mixed gas of nitrogen and an inert gas such as argon may be introduced into the film formation chamber. In the case of an inert gas such as nitrogen and argon, both gases may be mixed beforehand and then introduced into the film formation chamber, or argon gas and nitrogen gas may be separately introduced near the target. In this case, as the sputtering conditions, any conditions may be used as long as the sputtering film (phase shift film) can be formed, but the gas pressure is preferably 0.05 to 10 Pa.

In the phase shift mask blank of the present invention, the phase shift film may be formed in two or more layers.

Further, as shown in FIG. 3, a Cr-based light-shielding film 3 is provided on the phase shift film 2, or as shown in FIG. The anti-reflection film 4 can be formed on the Cr-based light-shielding film 3. In this case, CrO,
It is preferable to use a Cr-based film such as CrN, CrON, or CrCON.

Next, when a phase shift mask as shown in FIG. 2 is manufactured using the phase shift mask blank of the present invention, the phase shift mask is formed on the transparent substrate 1 as shown in FIG. After the film 2 is formed, a resist film 5 is formed on the phase shift film, the resist film 5 is patterned as shown in FIG. 5B, and further, as shown in FIG. After the phase shift film 2 is dry-etched or wet-etched, a method of stripping the resist film 5 as shown in FIG. In this case, the application, patterning (exposure, and development) of the resist film, and the removal and etching of the resist film can be performed by a known method.

[0027]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 Using a 3 ″ MoSi ₃ (SiO ₂ ) _0.5 target on a 6 ″ square quartz substrate, argon and nitrogen were used as sputtering gases at a flow ratio of 1:20.
Gas pressure during discharge 0.3 Pa, 200
W, MoSi by sputtering at a film formation temperature of 120 ° C
An ON film was formed.

The transmittance of the obtained sample at 248 nm was 5.8%, and the phase difference was 179 degrees. Laser Tech MPM-2 with in-plane uniformity at 248 nm wavelength
48, the variation in transmittance was 0.15.
% And the variation of the phase difference were 1.9%. The formula for calculating the variation is as follows. Variation in transmittance or phase difference (%) = ｛(max−mi)
n) / (max + min)｝ × 100 [where, max represents the maximum value of the transmittance or the phase difference in the plane, and min represents the minimum value of the transmittance or the phase difference in the plane. ]

The prepared phase shift mask blank was
Mixture of sulfuric acid and hydrogen peroxide at 0 ° C (mixing ratio 1: 4)
For 1 hour, the transmittance before and after the immersion was measured, and the chemical resistance was evaluated from the change. The change in the transmittance was 0.08%. As a result of analyzing the composition of this film by an X-ray photoelectron spectrometer (XPS), 13 atomic% of molybdenum, 34 atomic% of silicon, 11 atomic% of oxygen and 42 atomic% of nitrogen were obtained.
Atomic% was contained. Table 1 shows the results.

Example 2 The target was MoSi ₃ (S
It was replaced with iO _{2) 0.8,} MoSi under the same conditions as in Example 1
An ON film was formed. The transmittance of the obtained sample at 248 nm was 5.9%, and the phase difference was 180 degrees. When the in-plane variation was measured by the same method as in Example 1, the transmittance was 0.13% and the phase difference was 1.6%.
When the chemical resistance was evaluated in the same manner as in Example 1, the change in transmittance before and after immersion was 0.09%. As a result of analyzing the composition of this film by an X-ray photoelectron spectrometer (XPS), it was found that molybdenum was contained at 11 at%, silicon at 35 at%, oxygen at 14 at%, and nitrogen at 40 at%. Table 1 shows the results.

Example 3 The target was MoSi ₃ (S
iO ₂ ) MoSi under the same conditions as in Example 1 except that it was changed to _0.2.
An ON film was formed. The transmittance of the obtained sample at 248 nm was 5.5%, and the phase difference was 179 degrees. When the in-plane variation was measured by the same method as in Example 1, the transmittance was 0.19% and the phase difference was 1.8%.
When the chemical resistance was evaluated in the same manner as in Example 1, the change in transmittance before and after immersion was 0.08%. As a result of analyzing the composition of this film by an X-ray photoelectron spectrometer (XPS), it was found that 14 atomic% of molybdenum, 32 atomic% of silicon, 6 atomic% of oxygen, and 48 atomic% of nitrogen were contained. Table 1 shows the results.

Example 4 The target was MoSi
_A MoSiON film was formed under the same conditions as in Example 1 except that _2.3 (SiO ₂ ) was changed to _0.5 . 248 of the sample obtained
The transmittance in nm was 5.1%, and the phase difference was 181 degrees. When the in-plane variation was measured by the same method as in Example 1, the transmittance was 0.21% and the phase difference was 2.2%. When the chemical resistance was evaluated in the same manner as in Example 1, the change in transmittance before and after immersion was 0.11%. As a result of analyzing the composition of this film by an X-ray photoelectron spectrometer (XPS), it was found that 14 atomic% of molybdenum, 29 atomic% of silicon, 12 atomic% of oxygen, and 45 atomic% of nitrogen were contained. Table 1 shows the results.

Comparative Example 1 Using a 3 ″ MoSi _3.5 target on a 6 ″ square quartz substrate, a mixed gas of argon, nitrogen and oxygen was used as a sputtering gas, and a flow ratio of argon gas and nitrogen gas was 1 : 20, the flow rate of oxygen gas was adjusted so that the transmittance when the phase difference was 180 degrees was about 6%, and a MoSiON film was formed under the same conditions and method as in Example 1. The transmittance of the obtained sample at 248 nm was 5.8%, and the phase difference was 180 degrees. When the in-plane variation was measured by the same method as in Example 1, the transmittance was 0.42% and the phase difference was 3.1%. When the chemical resistance was evaluated in the same manner as in Example 1, the change in transmittance before and after immersion was 0.32%. As a result of analyzing the composition of this film by an X-ray photoelectron spectrometer (XPS), it was found that 14 atomic% of molybdenum, 37 atomic% of silicon, 10 atomic% of oxygen, and 39 atomic% of nitrogen were contained. Table 1 shows the results.

[0035]

[Table 1]

[0036]

According to the present invention, when a phase shift film containing metal, silicon, oxygen and nitrogen is produced by a sputtering method, a target containing a metal, silicon and silicon oxide is used as a target, so A method of manufacturing a high-quality phase shift mask blank with high in-plane uniformity of the shift film and improved chemical resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a phase shift mask blank according to one embodiment of the present invention.

FIG. 2 is a sectional view of a phase shift mask according to one embodiment of the present invention.

FIG. 3 is a sectional view of a phase shift mask blank according to another embodiment of the present invention.

FIG. 4 is a sectional view of a phase shift mask blank according to another embodiment of the present invention.

5A and 5B illustrate a process of manufacturing a phase shift mask from a phase shift mask blank, wherein FIG. 5A shows a state in which a resist film is formed on the phase shift film of the phase shift mask blank, and FIG. FIG. 4C is a cross-sectional view showing a state in which the phase shift film is patterned by etching, and FIG. 4D is a cross-sectional view showing a state in which the phase shift mask is formed by removing the resist film.

6A and 6B are diagrams for explaining the principle of a halftone type phase shift mask, and FIG. 6B is an enlarged view of a portion X.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 1a Substrate exposed part 2 Phase shift film 2a Phase shifter part 3 Light shielding film 4 Antireflection film 5 Resist film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsushi Tsukamoto 28-1 Nishifukushima, Kazagi-mura, Nakakushiro-gun, Niigata Pref. 28-1 Nishi-Fukushima, Kushiro-mura, Japan Shin-Etsu Chemical Co., Ltd. (72) Inventor Satoshi Okazaki 28-1 Nishifukushima, Kazagusuku-mura, Nakakubijo-gun, Niigata Prefecture F-term in Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Laboratory 2H095 BB03 BB25 BC24

Claims (6)

[Claims] 1. A method for manufacturing a phase shift mask blank comprising a transparent substrate provided with one or more phase shift films containing metal, silicon, oxygen and nitrogen, wherein the phase shift film is formed of a target containing metal, silicon and silicon oxide. A method for producing a phase shift mask blank, comprising forming a film by reactive sputtering in an atmosphere containing nitrogen. 2. The method according to claim 1, wherein the metal is molybdenum. 3. The method for producing a phase shift mask blank according to claim 1, wherein the content of silicon oxide in the target is 3 to 20% in a molar ratio. 4. The method for manufacturing a phase shift mask blank according to claim 1, wherein the total of silicon and silicon oxide in said target is 60 to 90% by mole ratio. 5. The phase according to claim 1, wherein the phase shift film changes the phase of the transmitted exposure light by 180 ± 5 degrees and has a transmittance of 3 to 40%. Manufacturing method of shift mask blank. 6. A method for manufacturing a phase shift mask, comprising patterning a phase shift mask blank obtained by the method according to claim 1 by lithography.