JPH05232679A - Production of mask and method for correcting mask defect - Google Patents

Abstract

PURPOSE:To form a phase shifter having plural phase differences with high accuracy by suppressing the fluctuation in process conditions, etc., and to correct a phase shifter defect without complicating a mask structure. CONSTITUTION:This process for production of the phase shift mask includes a stage for forming prescribed light shielding patterns on a transparent substrate 1, a stage for forming prescribed transparent thin film patterns 3 for applying the phase differences to exposing light on the substrate 1, a stage for forming a coating film consisting of a negative type radiation sensitive material on the substrate 1, a stage for irradiating the prescribed regions of the coating film, for example, the regions including the pattern edges of the transparent thin-film patterns 3 or the regions proximate to the pattern edges of the transparent thin-film patterns 3 with active chemical rays, a stage for developing the prescribed patterns 4 by dissolving the regions not irradiated with the active chemical rays on the coating film and a stage for executing a heat treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask used for forming a fine pattern in various solid-state elements such as semiconductor elements, superconductor elements, magnetic elements, optical integrated circuit elements, etc., and a method for manufacturing the mask. This is related to the correction method.

[0002]

2. Description of the Related Art Conventionally, a reduction projection exposure method has been mainly used for forming a fine pattern in a solid state element such as a large scale integrated circuit. One of the methods capable of dramatically improving the resolution by using the above method is a method of introducing a phase difference between exposure lights passing through adjacent transmission regions on a mask (hereinafter, referred to as a phase shift method. Called) is proposed.

In this method, for example, in the case of a repeating pattern of an elongated transmissive area and an opaque area, one of the transmissive areas is set so that the phase difference of light passing through the transmissive areas on the mask which are adjacent to each other becomes approximately 180 degrees. A transparent material (hereinafter referred to as a phase shifter) for introducing a phase difference is provided on the mask. The mask used in the phase shift method can be manufactured by providing a phase shifter on a predetermined transmission region of a chromium mask which has been conventionally used. Regarding this, for example, IEE, Transaction on Electron Devices, ED 29, No. 12 (1982).
1828 to 1836 (IEEE, Tra)
ns. Electron Devices, ED29,
No. 12 (1982) pp 1828-1836).

On the other hand, it is difficult to apply the above method to all patterns. For example, when the phase shift method is applied to a U-shaped pattern, the arrangement of the phase shifter patterns becomes as shown in FIG. 12, for example. That is, the pattern region 8 not provided with the phase shifter and the pattern region 9 provided with the phase shifter are arranged in direct contact with each other. For this reason, there is a problem that a desired pattern cannot be transferred because the lights cancel each other at the boundary between the two areas.

Therefore, in order to relax the limitation of the pattern to which the phase shift method can be applied, there is a method of providing, for example, a region having a phase difference of 90 degrees at the boundary between the phase differences of 0 degrees and 180 degrees. In this method, for example, mask patterns are arranged as shown in FIG. Here, the first transmission pattern region 10 is a transmission region not provided with a phase shifter,
Of the second transmission region 11 has a phase difference of 90 degrees, and the second transmission region 11 has a phase difference of 90 degrees.
This is a region provided with a phase shifter that provides a frequency. Since the phase difference of the exposure light that has passed through the adjacent transmission regions becomes 90 degrees, the light blocking effect due to the light interference at the boundary portion is weakened. Therefore, a desired U-shaped pattern can be transferred.

This is described, for example, in Japanese Patent Publication No. 2-34854.

Conventionally, as in the example shown in FIG. 13, in order to form a phase shifter pattern having two phase differences of 180 degrees and 90 degrees, an electron beam resist material is used as the phase shifter material and an electron beam irradiation dose is used. Was used to control the phase difference, that is, the phase shifter film thickness. About these, for example, 35th International Symposium on Electron, Ion and Photon
Beams (1991) L1 (THE 35TH I
NTERNATIONAL SYMPOJIUM ON
ELECTRON, ION AND PHOTON
BEAMS (1991) L1).

By the way, when a solid-state element such as a DRAM is manufactured by using the above-mentioned phase shift mask, a mask pattern defect causes a significant decrease in yield. Therefore,
A technique for manufacturing a defect-free mask or a technique for completely correcting a defect is essential.

In the case of a phase shift mask, when a phase shifter defect occurs, not only the normal phase shift effect cannot be obtained, but also this portion is transferred as a defect. Therefore, a technique for correcting the phase shifter defect is also needed.

As a method of correcting defects in the phase shifter pattern of the phase shift mask, the structure of the mask is made to be a structure in which defects can be easily corrected in advance, and a focused ion beam (FI
Methods have been proposed for repairing defects using selective etching techniques such as B). For example, it has a mask structure in which a second phase shifter layer for defect correction is provided between the phase shifter and the mask substrate. For example, the 51st
Proceedings of the 2nd Annual Meeting of the Japan Society of Applied Physics, 2nd Volume, 493 pages, 27p-ZC-10.

[0011]

In the above prior art, the film thickness of the phase shifter formed after development is controlled by adjusting the electron beam irradiation amount so that the phase difference becomes 90 degrees. Therefore, there is a problem that it is difficult to accurately control the phase difference to 90 degrees due to variations in process conditions such as the electron beam irradiation amount. Further, since an organic material such as a resist material is used as the phase shifter material, there is a problem that sufficient durability cannot be obtained as the phase shifter.

Further, in the above-mentioned conventional technique, there is a problem that the mask structure and the mask manufacturing process are complicated because the phase shifter defect can be corrected.

[0013]

The above problems are caused by manufacturing a phase shift mask having a predetermined transmission pattern and a transparent thin film pattern for imparting a phase difference to transmitted light, which is used when a mask pattern is transferred onto a substrate. In the method, a step of forming a predetermined light-shielding pattern on a transparent substrate, a step of forming a predetermined transparent thin film pattern for giving a phase difference to exposure light on the substrate, and a negative-type radiation-sensitive layer on the substrate. A step of forming a coating film made of a material, and a step of irradiating a predetermined region of the coating film, for example, a region including a pattern edge portion of the transparent thin film pattern or a region close to the pattern edge of the transparent thin film pattern with active actinic radiation. And a step of developing a predetermined pattern by dissolving an active actinic ray non-irradiated area of the coating film, and a step of further heat treatment.

Further, the above problem can be solved by a mask defect repairing method in which the predetermined region is a region including a defective portion of the transparent thin film pattern or a region close to the defective portion of the transparent thin film pattern.

Further, the above problem is caused by using the mask so that the film thickness d of the negative radiation-sensitive material is adjusted so that the phase difference of the exposure light introduced by the film is within 90 degrees. The relationship of d ≦ λ / {4 (n-1)} with respect to the wavelength λ of the exposure light used when the mask pattern is exposed on the substrate and the refractive index n of the negative radiation-sensitive material at the wavelength λ. This is solved by a mask manufacturing method and a mask defect repairing method that satisfy the above conditions.

Further, the problem is that the film thickness d of the coating film made of the negative radiation sensitive material is set so that the phase difference of the exposure light introduced by the coating film is about 360 degrees, that is, substantially the same phase. With respect to the wavelength λ of the exposure light used when the mask pattern is exposed on the substrate using the mask, and the refractive index n of the negative radiation-sensitive material at the wavelength λ, (3/4) · {λ / ( n-1)} ≦ d ≦ (5/4) · {λ / (n-1)}, which is solved by a mask defect repairing method.

Further, the above problem is caused by using a material containing at least a coatable silicon compound containing a residual silanol group as the radiation sensitive material, or by using a material containing an acid generator and a residual silanol group as the radiation sensitive material. The solution is to use a material containing at least a compound.

[0018]

As described above, according to the phase shift method, the phase difference of the light passing through the transmission regions on the mask which are adjacent to each other is almost 1
This is a method of improving the resolution by setting it to 80 degrees. Therefore, it is necessary to provide a phase shifter for introducing a phase difference into a predetermined transmission area on the mask.

Generally, the optimum value of the phase shifter film thickness for introducing the phase difference of 180 degrees is determined by the following equation.

[0020]

## EQU1 ## d1 = .lamda ./ {2 (n1-n0)} (Equation 1) where d1 is the phase shifter film thickness, .lamda. Is the exposure wavelength, and n1 is the refractive index of the phase shifter film at the exposure wavelength .lamda. Further, n0 is the refractive index of air at the exposure wavelength λ, and may be considered to be 1 in practice. From (Formula 1), the phase difference is 90
The thickness of the phase shifter for the introduction is d1 / 2.

There are various methods for forming the phase shifter pattern. For example, after forming a predetermined light-shielding pattern on a transparent substrate, a phase shifter film, for example, a silicon oxide film is uniformly formed on this substrate so as to have a film thickness d1 determined by (Equation 1). There is a method of processing the above into a predetermined pattern using a resist.

By the way, as described in the section of the prior art, in the method of arranging the phase shifter which gives the phase difference of 180 degrees, the applicable pattern may be limited. Therefore, as a method of relaxing such a limit, as described in JP-A-2-34854, 0
There is a method of gradually changing the phase difference from degrees to 180 degrees. This method utilizes that the interference effect of the exposure light in this portion becomes smaller as the phase difference change becomes smaller than 180 degrees, and the light-shielding pattern is hard to be formed.

As a method of manufacturing the above-mentioned phase shift mask, Japanese Patent Laid-Open No. 34854/1990 discloses a method of vapor-depositing a material of a phase shifter, for example, a silicon oxide film, a plurality of times so that the phase difference gradually changes. A method of etching a shifter film and a mask substrate stepwise, a method of repeating resist coating / resist pattern formation / curing treatment, and the like are described. However, in the former two methods, the steps of vapor deposition and etching need to be performed a plurality of times, which makes the mask manufacturing process complicated. Further, in the third method, as shown in FIG. 8 of JP-A-2-34854, a region for giving a phase difference of 180 degrees is formed by a plurality of times of vapor deposition or coating. For this reason, not only the mask manufacturing process becomes complicated, but also film thickness variations due to vapor deposition and coating are accumulated, which may make it difficult to accurately control the phase difference to 180 degrees.

By the way, a coating type silicon compound such as coating type glass has a property that it becomes transparent like glass by heat treatment at a temperature of about 200 ° C. or higher and high mechanical durability is obtained. Further, a coating type silicon compound such as a coating type glass containing residual silanol groups has a property of acting negatively by being exposed to an actinic ray such as an electron beam. By using the above properties, the above-mentioned phase shifter pattern can be easily formed directly without processing using a resist or the like.

Therefore, as shown in FIG. 1, first, a first phase shifter 3 is formed by a known method so that the phase difference becomes 180 degrees, that is, the film thickness satisfies (Equation 1). Thereafter, a coating film made of a coating type silicon compound containing residual silanol groups, for example, coating type glass is formed on the substrate. This material acts negatively by being exposed to actinic rays such as electron rays. Here, the film thickness d of the coating film is d ≦ λ / {4 (n− so that the phase difference of the exposure light introduced by the coating film is 90 degrees or less.
The coating film is formed so as to satisfy the relationship of 1)}. In addition,
n is the refractive index of the coating type silicon compound at the exposure wavelength λ. Here, by appropriately selecting the coating conditions, it is possible to smoothly change the film thickness of the coating film in the vicinity of the pattern edge of the first phase shifter 3 as shown in FIG.

Next, a predetermined region near the pattern edge of the first phase shifter 3 is irradiated with an active actinic ray, for example, an electron beam, and the second phase shifter 4 is developed by developing with a predetermined developing solution. Can be formed.

Although the case where the negative type radiation sensitive material is used has been described here as an example, the same pattern can be formed by using the positive type radiation sensitive material.

The operation will be further described with reference to FIGS. 2 and 3. When only the phase shifter pattern having a phase difference of 180 degrees is arranged, the light intensity becomes small at the end of the phase shifter pattern, and this portion is transferred as a light shielding pattern. Therefore, the desired mask pattern cannot be transferred.

On the other hand, by forming the phase shifter pattern as described above, the phase difference of the light passing through the mask portion shown in FIG. 1 immediately after passing through the mask changes as shown in FIG. Here, the case where the phase difference of the exposure light of 90 degrees is further introduced by the second phase shifter 4 will be considered as an example. On the phase shifter pattern having a phase difference of 180 degrees, the phase difference further changes by 90 degrees. On the other hand, the phase difference becomes 90 degrees in the portion where the phase shifter pattern is not formed. During this period, the phase difference gradually changes from 270 degrees to 90 degrees.

From the above, the light intensity of the light passing through the mask portion of FIG. 1 on the substrate for transferring the pattern changes as shown in FIG. When the phase difference is 90 degrees, the light interference effect is smaller than when the phase difference is 180 degrees, so that the attenuation of the light intensity can be suppressed smaller than when the phase difference is 180 degrees. Usually, a resist film in a region where a light intensity of a certain level or more is obtained is dissolved after development in the case of a positive resist, and conversely remains after development in a negative resist.
A pattern is formed. Therefore, by gradually changing the phase difference, the light-shielding region is not formed in the region corresponding to the pattern edge portion of the first phase shifter 3, so that the pattern is not formed on the substrate.

In the above description, the film thickness of the second phase shifter 4 is described as an example in which the phase difference is introduced by 90 degrees, but the film thickness of the second phase shifter 4 is It is preferable that the thickness is not close to a film thickness at which a phase difference is introduced by 180 degrees. In practice, the phase difference may be such that it is not transferred as a light-shielding pattern, and it is desirable that it is 120 degrees or less, preferably 90 degrees or less. That is, the coating film thickness d of the second phase shifter 4 is d ≦ (2/3) · {λ / 2 (n−
1)} is satisfied, preferably d ≦ λ /
It is desirable to satisfy the relationship of {4 (n-1)}. This is because the interference effect of light becomes stronger as the phase difference approaches 180 degrees.

By the way, when a solid-state element such as a DRAM is manufactured by using the above-mentioned phase shift mask, a mask pattern defect causes a significant decrease in yield. In the case of the phase shift mask, a technique for easily repairing the phase shifter defect is required.

The types of phase shifter defects of the phase shift mask include A: phase shifter defect, B: phase shifter remaining, and C: foreign matter on the phase shifter. C can be sufficiently removed by cleaning the mask.

For B, FIB (focused ion beam)
It can be corrected by selectively removing the phase shifter by using, for example. However, since gallium ions are mainly used as the ion species, the mask transmittance may decrease in the ion beam irradiation region. If the remaining phase shifter has a size less than the pattern resolution limit, it need not be modified.

As a technique for correcting the phase shifter defect of A, there is a method as described in the section of the prior art. In this method, it is necessary to devise a mask structure in advance so that the phase shifter defect can be repaired. But,
For this reason, there are disadvantages that the mask manufacturing becomes complicated and the production cost becomes high.

By the way, in general, when a coating film is formed by a spin coating method or the like, a smooth coating film surface is formed as compared with the steps of the substrate on which the coating film is formed, or the coating film surface is The unevenness tends to be smaller than the unevenness of the substrate on which the coating film is formed. For example, by using appropriate coating conditions, the fine recesses are sufficiently filled, and it is possible to form a relatively flat coating surface with no irregularities. In a relatively large concave area, the coating film thickness at the step portion gradually changes, and a smooth surface is formed.

Therefore, first, a coating film is formed using a negative-type radiation-sensitive material, in particular, a coatable silicon compound such as a coatable glass which can obtain high durability by heat treatment.
Here, by using appropriate coating conditions, a relatively flat coating surface can be formed as described above. Thereafter, by irradiating an active actinic ray such as an electron beam or an ion beam into the region including the phase shifter defect and developing the pattern to form the region including the phase shifter defect, the defect of the phase shifter defect can be corrected. it can.

The defect correction principle when the phase shifter defect defect 5 as shown in FIG. 5 is detected in the mask inspection process will be described. FIG. 4 is a schematic cross-sectional view of the mask when the film thickness of the second phase shifter 4'is such that the phase difference is introduced by 360 degrees, that is, the coating film thickness value that is twice d1 from (Equation 1). The figure is shown. When the size of the phase shifter defect defect is, for example, about the coating film thickness or less, the phase shifter defect defect 5 can be obtained by appropriately selecting the coating conditions.
Can be filled in to form a relatively flat coating film surface. As a result, after the defect correction process as described above, the first
Since the phase difference between the exposure light passing through the phase shifter 3 and the exposure light passing through the area after the defect correction is 360 degrees, that is, the same phase, the same effect as when there is no phase shifter defect is obtained. ..

FIG. 6 is a cross section of the mask when the film thickness of the second phase shifter 4 is such that a phase difference of 90 degrees or less is introduced, for example, a phase difference of 30 degrees is introduced. FIG. The coating thickness is d from (Equation 1)
The film thickness value is 1/6 times that of 1. When a material containing silicon oxide as a main component such as coating type glass is used for the phase shifter, the refractive index is about 1.45, and thus the coating film thickness in this case is about 70 nm. On the other hand, reduction ratio 5: 1
When a 0.2 μm pattern is transferred by using the reduction projection exposure apparatus of No. 2, the mask pattern size is 1.0 μm. Therefore, it is considered that the coating film thickness value is sufficiently smaller than the pattern size, and the size of the phase shifter defect defect is usually larger. In such a case, the portion of the phase shifter deficiency defect 5 is not sufficiently flattened and a recess is likely to be formed. However, since the phase shifter defect defect 5 is filled, the phase change is 180
The phase shifter defect defect 5 is less likely to be transferred. That is, the phase shifter defect defect 5 can be repaired.

FIG. 7 is a schematic view of a mask cross section when two types of phase shifter defect defects 5 and 5'are detected. In this case, in order to correct the phase shifter deficiency defect 5, the second phase difference in which the phase difference is approximately 360 degrees or the phase is almost the same as that of the exposure light passing through the area provided with the phase shifter. Or the second phase shifter 4 having a phase difference of about 90 degrees or less may be provided.

Here, in order to introduce the phase difference of approximately 360 degrees, the wavelength λ of the exposure light used when the mask pattern is exposed on the substrate using the mask, and the phase shifter 4'at the wavelength λ. The film thickness d of the phase shifter 4 ′ is (3/4) · {λ / (n−1)} ≦ d ≦ (5/4) · {λ / (n−1) )} Is satisfied. Further, in order to introduce a phase difference of 90 degrees or less, the relationship of d ≦ λ / {4 (n−1)} may be satisfied.

On the other hand, in order to correct the phase shifter defect 5 ', a second phase shifter 4 "having a phase difference of about 180 degrees may be provided. In this case, (1/4) .multidot. The relationship of {λ / (n-1)} ≦ d ≦ (3/4) · {λ / (n-1)} may be satisfied.

As can be seen from the above, since the film thickness of the second phase shifter for defect correction is different, it is necessary to separately correct the phase shifter defect defects 5 and 5 '. here,
Since the film thickness of the second phase shifter 4'is twice the film thickness of the second phase shifter 4 ", the total phase difference is 360 degrees by dividing the second phase shifter 4'into two times. In this case, since the coating is performed twice in total, the coated film surface can be further flattened.

By using the method as described above, it becomes possible to easily correct the phase shifter defect defect without specially devising the mask structure.

Further, by using this method, it is possible to correct the phase shifter residual defect. That is, as shown in FIG. 10, the second phase shifter 4 ′ having a phase difference of 360 degrees may be formed in the region including the phase shifter residual defect 6. As a result, the phase shifter residual defect 6 can be corrected. If the thickness of the phase shifter residual defect 6 is about 90 degrees or less in terms of phase difference, or if the size is less than the resolution limit, this defect is difficult to be transferred, and the defect is corrected. It may not be necessary.

As described above, by using the present invention, it is possible to efficiently inspect and correct phase shifter defects.

Example 1 One example of the present invention will be described below.

A phase shift mask for a wiring pattern manufacturing process of a large-scale integrated circuit of a 64-megabit DRAM (dynamic random access memory) class having a minimum design dimension of 0.3 μm was manufactured. A process for manufacturing a phase shift mask for a 5: 1 i-line (exposure wavelength 365 nm) reduction projection exposure apparatus having a numerical aperture NA = 0.50 according to this embodiment will be described with reference to FIGS.

First, a transparent quartz conductive film 22 and a chromium film 23 were laminated in this order on a synthetic quartz substrate 21. Here, the transparent conductive film 22 is provided to prevent charge-up during electron beam writing. Also, the chrome film 23
Is used as a light-shielding film.

Although the chromium film is used as the light-shielding film here, a film opaque to the exposure light, such as a molybdenum silicide film, may be used. A second phase film may be provided between the transparent conductive film 22 and the chrome film 23 in order to facilitate the defect correction when a phase shifter defect occurs. The second phase shifter film can be provided on the chrome film.

A positive resist RE2000 is formed on the above substrate.
P (Hitachi Kasei, product name) was applied to a film thickness of 0.5 μm.
After heat treatment at a temperature of 100 ° C for 30 minutes, accelerating voltage 30k
A predetermined transmission pattern was drawn with an electron beam using a V electron beam drawing apparatus. Then, predetermined development and heat treatment were performed to form a desired resist pattern. Next, using the resist pattern as a mask, the chromium film was wet-etched using a predetermined etching solution and etching conditions. After that, the resist pattern was removed to form a desired light shielding pattern as shown in FIG.

Next, coating glass OCD type 7 (Tokyo Ohka, product name) was spin-coated on the above substrate to form a coating film. Here, the coating type glass film is used as a phase shifter film. The material of the phase shifter film is not limited to the above, and other coating type glass or organic polymer material may be used, but it is preferable that the transmittance for the exposure light is 90% or more.

Generally, the optimum value of the phase shifter film thickness is determined by the equation (1). Where d is the phase shifter film thickness, λ
Is the exposure wavelength, and n is the refractive index of the phase shifter film at the exposure wavelength λ. In this embodiment, λ = 365 nm, n = 1.
It was 45. According to the equation (1), the film thickness of the coating type glass film is 406 nm. On the other hand, it was found that the coating type glass film had a thickness of 90% of the coating thickness when the steps described below were performed. Therefore, in this example, the coating thickness of the coating type glass film was set to 451 nm.

Thereafter, the above substrate was heat-treated at a temperature of 200 ° C. for 30 minutes using a hot air convection furnace. here,
The heat treatment temperature and time conditions are not limited to the above values.

Next, a negative resist RD2000N (Hitachi Chemical Co., Ltd., product name) is formed on the mask substrate to a film thickness of 0.5 μm.
Applied to. After heat treatment at a temperature of 80 ° C. for 30 minutes, a predetermined phase shifter pattern was subjected to electron beam drawing using an electron beam drawing device with an acceleration voltage of 30 kV. Then, predetermined development and heat treatment were performed to form a desired resist pattern. next,
The coated glass film was wet-etched using the resist pattern as a mask and using a predetermined etching solution and etching conditions. Then, the resist pattern was removed to form a desired phase shifter pattern 24 as shown in FIG.

Next, as shown in FIG. 20, a second coating type glass film 25 was formed on the substrate. In the present embodiment, the second
The phase difference was introduced by 30 degrees by the coating type glass film 25 of. Therefore, the coating film thickness of the coating type glass film 25 is set to 451 / 6≈75 nm from the above. The second
Although the film thickness of the coating type glass film 25 is not limited to the above, it is preferable that the film thickness is not close to a film thickness value at which the phase difference is introduced by 180 degrees, and the phase difference becomes about 90 degrees or less. preferable. After that, the substrate was heat-treated at a temperature of 80 ° C. for 5 minutes using a hot air convection furnace. Here, the temperature and time of the heat treatment are not limited to the above values, but it goes without saying that it is not preferable to use the conditions of the heat treatment temperature and the heat treatment time such that the heat treatment does not dissolve in a predetermined developing solution.

Next, a desired pattern was drawn by irradiating a predetermined region including the pattern edge of the phase shifter pattern 24 with the electron beam 26 by using an electron beam drawing apparatus with an accelerating voltage of 30 kV (FIG. 21). In this embodiment, electron beam 2 is used as the active actinic ray.
Although 6 is used, the invention is not limited to this, and it is also possible to use, for example, laser light.

After that, it was developed with methanol for 30 seconds, dried, and further heat-treated at a temperature of 200 ° C. for 30 minutes, and then, as shown in FIG.
A second phase shifter pattern 27 was formed as shown in FIG. Here, the conditions of the heat treatment are not limited to the above, but in order to improve the mechanical durability, the heat treatment temperature is preferably the glass transition temperature of the material or higher, for example, 200 ° C. or higher. As described above, the phase shift mask having the desired pattern was manufactured.

In this embodiment, the area including the pattern edge of the phase shifter is irradiated with the electron beam as the active actinic ray. However, the invention is not limited to this. For example, as shown in FIG. The second phase shifter pattern 27 may be formed adjacent to the phase shifter pattern 24 by irradiation and development.

As a result of pattern transfer using the phase shift mask manufactured as described above and the above-described reduction projection exposure apparatus, a desired pattern could be transferred with good resolution.

Further, by using the phase shift mask manufactured in this embodiment, it is possible to transfer a fine pattern which cannot be resolved by the conventional transmission type mask. It can be manufactured with a high yield.

Example 2 256 Mbit DRAM with a minimum design size of 0.25 μm
A phase shift mask for a wiring pattern manufacturing process of a large scale integrated circuit of a class was manufactured. Numerical aperture NA according to this embodiment NA = 0.4
KrF excimer laser with 5: 1 reduction ratio of 5 (exposure wavelength 2
A manufacturing process of a phase shift mask for a 48 nm reduction projection exposure apparatus will be described.

First, a transparent conductive film was laminated on a synthetic quartz substrate, and a silicon oxide film was further vapor-deposited as a phase shifter film for defect correction. In equation (1), λ = 248n
From m and n = 1.5, the phase shifter film thickness is 248 nm. Therefore, the thickness of the silicon oxide film is set to 248 nm. Here, the material of the phase shifter film is not limited to the above, and other materials may be used, but it is preferable that the transmittance for the exposure light is 90% or more.

After that, a chromium film having a thickness of 80 nm was vapor-deposited as a light-shielding film on the substrate. Next, a positive resist RE2000P (Hitachi Chemical Co., Ltd., product name) was applied on the substrate to a film thickness of 0.5 μm. After heat treatment at a temperature of 100 ° C. for 30 minutes, a predetermined transmission pattern was drawn with an electron beam using an electron beam drawing device with an acceleration voltage of 30 kV. Then, predetermined development and heat treatment were performed to form a desired resist pattern. Next, using the resist pattern as a mask, the chromium film was wet-etched using a predetermined etching solution and etching conditions, and then the resist pattern was removed to form a desired light-shielding pattern.

Next, coating glass OCD type 7 (Tokyo Ohka, product name) was spin-coated on the substrate to form a coating glass film as a phase shifter film. In the equation (1), λ = 248 nm and n = 1.49, and thus the phase shifter film thickness is 253 nm. On the other hand, it was found that the coating type glass film had a thickness of 90% of the coating thickness when the steps described below were performed. Therefore, in this example, the coating film thickness of the coating type glass film was set to 281 nm. Here, the material of the phase shifter film is not limited to the above, and other materials may be used, but it is preferable that the transmittance for the exposure light is 90% or more.

Thereafter, the above substrate was heat-treated at a temperature of 80 ° C. for 10 minutes using a hot air convection furnace. Here, the conditions of temperature and time of heat treatment are not limited to the above values.

Next, a predetermined phase shifter pattern was subjected to electron beam drawing using an electron beam drawing apparatus having an accelerating voltage of 30 kV, and predetermined development and heat treatment were performed to form a desired phase shifter pattern.

Next, coating type glass OCD type 7 (Tokyo Ohka, product name) is spin-coated on the above substrate again, and the second
A coating type glass film was formed as the phase shifter film. In this example, the coating film thickness was set to 24 nm so that the phase difference was introduced by 30 degrees by the second phase shifter film. here,
In this embodiment, the phase difference is introduced by 30 degrees by the second phase shifter, but the present invention is not limited to this. In addition,
When the phase difference introduced by the second phase shifter has a value close to 180 degrees, there is a possibility that a light blocking pattern may be formed due to light interference. Therefore, the phase difference introduced by the second phase shifter is more preferably about 120 degrees or less.

Here, the material of the second phase shifter film is not limited to the above, and other materials may be used, but it is necessary that the material is sensitive to active actinic radiation.
The transmittance for exposure light is preferably 90% or more.

Thereafter, the substrate was heat-treated at a temperature of 80 ° C. for 5 minutes using a hot air convection furnace. Here, the conditions of temperature and time of heat treatment are not limited to the above values.

Next, a predetermined phase shifter pattern region was drawn by using an electron beam drawing device with an acceleration voltage of 30 kV. After that, the substrate was developed with methanol for 30 seconds and dried, and then further heat-treated at a temperature of 200 ° C. for 30 minutes to form a second phase shifter pattern. Here, the conditions of the heat treatment are not limited to the above, but the heat treatment temperature is preferably 200 ° C. or higher in order to improve mechanical durability. As described above, a phase shift mask having a desired pattern was obtained.

As a result of pattern transfer using the phase shift mask manufactured as described above and the above-mentioned reduction projection exposure apparatus, a desired pattern could be transferred with good resolution.

Example 3 A phase shift mask for a wiring pattern manufacturing process of a large-scale integrated circuit of a 64-megabit DRAM (dynamic random access memory) class having a minimum design dimension of 0.3 μm was manufactured. FIG. 14 and FIG. 15 show a part of the mask pattern of the phase shift mask for the 5: 1 i-line (exposure wavelength 365 nm) reduction projection exposure apparatus having the numerical aperture NA = 0.52 according to the present embodiment.

FIG. 14 shows a mask pattern for transferring a U-shaped transmission pattern. The light shielding film 7 is selectively removed to form a U-shaped transmission pattern 15, and then the second phase shifter 4 is formed to a thickness such that a phase difference of about 60 degrees is introduced onto the transmission pattern 15. Formed. Further, the first phase shifter 3 is formed to have a film thickness such that the phase difference is introduced by 180 degrees.

On the other hand, FIG. 15 shows a mask pattern for transferring a U-shaped light-shielding pattern. After forming the second phase shifter 4 in the transmissive region, the first phase shifter 3 was further formed.

The mask manufacturing process in this embodiment will be described in more detail below.

First, a transparent quartz conductive film and a chromium film were laminated in this order on a synthetic quartz substrate. Here, the transparent conductive film is used to prevent charge-up during electron beam writing, and the chromium film is used as a light-shielding film.

A positive resist RE2000 is formed on the above substrate.
P (Hitachi Kasei, product name) was applied to a film thickness of 0.5 μm.
After heat treatment at a temperature of 100 ° C for 30 minutes, accelerating voltage 30k
A predetermined transmission pattern was drawn with an electron beam using a V electron beam drawing apparatus. Then, predetermined development and heat treatment were performed to form a desired resist pattern. Next, using the resist pattern as a mask, the chromium film was wet-etched using a predetermined etching solution and etching conditions. After that, the resist pattern was removed to form a desired light-shielding pattern.

Next, coating type glass OCD type 7 (Tokyo Ohka, product name) was spin-coated on the above substrate to form a coating film. Generally, the optimum value of the phase shifter film thickness is determined by the equation (1). In this embodiment, λ = 365 nm and n =
It is 1.45, and the film thickness of the coating type glass film is 406 nm according to the equation (1). On the other hand, it was found that the coating type glass film had a thickness of 90% of the coating thickness when the steps described below were performed. Therefore, in this embodiment, the coating film thickness of the coating type glass film as a phase shifter is 451 nm.
Becomes Therefore, the coating film thickness is set to 150 nm so that the phase difference is introduced by about 60 degrees. The film thickness of the coating type glass film is not limited to the above, but it is preferable that the film thickness is not close to a film thickness value at which the phase difference is introduced by 180 degrees, and the phase difference is about 90 degrees or less. preferable.

Thereafter, the above substrate was heat-treated at a temperature of 200 ° C. for 30 minutes using a hot air convection furnace. here,
The heat treatment temperature and time conditions are not limited to the above values.

Next, a negative resist RD2000N (Hitachi Chemical Co., Ltd., product name) is formed on the mask substrate to a film thickness of 0.5 μm.
Applied to. After heat treatment at a temperature of 80 ° C. for 30 minutes, a predetermined pattern was drawn with an electron beam using an electron beam drawing device with an acceleration voltage of 30 kV. Then, predetermined development and heat treatment were performed to form a desired resist pattern. Next, the coating type glass film was wet-etched using the resist pattern as a mask and using a predetermined etching solution and etching conditions. Then, the resist pattern was removed to form a desired second phase shifter pattern 4.

Next, a second coating type glass film was formed on the above substrate. In this example, the second coating type glass film was used to introduce a phase difference of 180 degrees. Therefore, the second
From the above, the coating thickness of the coating type glass film was set to 451 nm.

Then, the substrate was heat-treated at a temperature of 80 ° C. for 5 minutes using a hot air convection furnace. Here, the temperature and time of the heat treatment are not limited to the above values, but it goes without saying that it is not preferable to use the conditions of the heat treatment temperature and the heat treatment time such that the heat treatment does not dissolve in a predetermined developing solution.

Next, a predetermined phase shifter pattern was drawn by using an electron beam drawing device with an acceleration voltage of 30 kV. After that, develop with methanol for 30 seconds and dry, and further heat at 2
Heat treatment was performed at 00 ° C. for 30 minutes to form the first phase shifter pattern 3. Here, the conditions of the heat treatment are not limited to the above, but in order to improve the mechanical durability, the heat treatment temperature is preferably the glass transition temperature of the material or higher, for example, 200 ° C. or higher. As described above, the phase shift mask having the desired pattern was manufactured.

As a result of pattern transfer using the phase shift mask manufactured as described above and the above-mentioned reduction projection exposure apparatus, a desired pattern could be transferred with good resolution.

Example 4 A phase shift mask for a wiring pattern manufacturing process of a large-scale integrated circuit of a 64-megabit DRAM (dynamic random access memory) class having a minimum design dimension of 0.3 μm was used in Example 1.
Manufactured as described in. A part of the mask pattern of the phase shift mask according to the present embodiment is shown in FIGS.

In FIG. 16, the second phase shifter 4 is arranged to transfer a key-shaped transmission pattern. On the other hand, FIG. 17 utilizes the fact that the light intensity is sufficiently reduced at the pattern edge portion of the first phase shifter 3 while the light intensity is not sufficiently reduced at the pattern edge portion of the second phase shifter 4, utilizing the stripe shape. The light-shielding pattern of is transferred.

As a result of pattern transfer using the phase shift mask manufactured as described above and the reduction projection exposure apparatus, a desired pattern could be transferred with good resolution.

Example 5 A phase shift mask for a wiring pattern manufacturing process of a large-scale integrated circuit of a 64-megabit DRAM (dynamic random access memory) class having a minimum design dimension of 0.3 μm was manufactured. A phase shifter defect repairing process of a phase shift mask for a 5: 1 i line (exposure wavelength 365 nm) reduction projection exposure apparatus having a numerical aperture NA = 0.52 according to this embodiment will be described with reference to FIGS. 24 to 27.

In this embodiment, a mask having a structure in which a transparent conductive film 22 is laminated on a synthetic quartz substrate 21 and a chromium film 23 and a phase shifter pattern 24 are formed on the transparent conductive film 22 will be described as an example. Here, the transparent conductive film 22 is provided to prevent charge-up during electron beam writing.

The phase shift mask for the exposure apparatus manufactured by the known method was inspected by using a predetermined mask pattern defect inspection apparatus. As a result, the phase shifter defect 28 and the second phase shifter defect phase 29 were detected. Figure 24
The cross-sectional shape of the mask is shown, but this figure shows the cross-sectional shape estimated from the result of observing the mask pattern surface.

Next, the phase shifter defect correction process will be described. First, the coated glass OCD type 7 was formed on the substrate.
(Tokyo Oka, product name) was spin-coated to form a coating film 25 as shown in FIG. Here, the coating type glass is used as the negative type radiation sensitive material, but the present invention is not limited to this, and other negative type resist materials can be used, but the transmittance for exposure light is 90% or more. Is preferred.

Generally, the optimum value of the phase shifter film thickness is determined by the equation (1). Where d is the phase shifter film thickness, λ
Is the exposure wavelength, and n is the refractive index of the phase shifter film at the exposure wavelength λ. In this example, the refractive index n of the coating type glass with respect to λ = 365 nm was 1.45. According to the equation (1), the film thickness of the coating type glass film is 406 nm. Therefore, in this example, the coating was performed so that the film thickness was 45 nm, which gives a phase difference of about 20 degrees. Here, the coating film thickness value is preferably a film thickness value such that the phase difference is 45 degrees or less.

Thereafter, the substrate was heat-treated at a temperature of 80 ° C. for 5 minutes using a hot air convection furnace. Here, the temperature and time conditions of the heat treatment are not limited to the above.

Next, an electron beam 26 was applied to a region including the phase shifter defect 28 and the second phase shifter defect 29 by using an electron beam drawing device having an accelerating voltage of 30 kV (FIG. 26). After that, develop with methanol for 30 seconds, dry and then 200 ℃
After heat-treating for 30 minutes, as shown in FIG.
The phase shifter pattern 27 of No. 1 was formed.

As a result of pattern transfer using the phase shift mask with the defects corrected as described above and the reduction projection exposure apparatus, the phase shifter defect 27 and the second phase shifter defect 29 are not transferred, The desired pattern could be transferred with good resolution.

[0097]

As described above, according to the present invention, a phase shifter pattern having a plurality of phase differences can be formed with high accuracy and easily. Further, according to the present invention, the phase shifter defect can be easily corrected.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating the operation of the mask according to the present invention.

FIG. 3 is a schematic diagram illustrating the operation of the mask according to the present invention.

FIG. 4 is a schematic view showing another embodiment of the present invention.

FIG. 5 is a schematic view showing an example of a cross section of a phase shift mask having a phase shifter defect.

FIG. 6 is a schematic view showing another embodiment of the present invention.

FIG. 7 is a schematic view showing an example of a cross section of a phase shift mask having a phase shifter defect.

FIG. 8 is a schematic view showing another embodiment of the present invention.

FIG. 9 is a schematic view showing another embodiment of the present invention.

FIG. 10 is a schematic view showing an example of a cross section of a phase shift mask having a phase shifter defect.

FIG. 11 is a schematic view showing another embodiment of the present invention.

FIG. 12 is a schematic view showing an example of a conventional phase shift mask.

FIG. 13 is a schematic view showing an example of a conventional phase shift mask.

FIG. 14 is a schematic view showing another embodiment of the phase shift mask according to the present invention.

FIG. 15 is a schematic view showing another embodiment of the phase shift mask according to the present invention.

FIG. 16 is a schematic view showing another embodiment of the phase shift mask according to the present invention.

FIG. 17 is a schematic view showing another embodiment of the phase shift mask according to the present invention.

FIG. 18 is a schematic view showing a part of the manufacturing process of a phase shift mask which is another embodiment of the present invention.

FIG. 19 is a schematic view showing a part of the manufacturing process of a phase shift mask which is another embodiment of the present invention.

FIG. 20 is a schematic view showing a part of the manufacturing process of a phase shift mask which is another embodiment of the present invention.

FIG. 21 is a schematic view showing a part of the manufacturing process of a phase shift mask which is another embodiment of the present invention.

FIG. 22 is a schematic view showing a part of a cross section of a phase shift mask which is another embodiment of the present invention.

FIG. 23 is a schematic view showing a part of a cross section of a phase shift mask which is another embodiment of the present invention.

FIG. 24 is a schematic view showing an example of a cross section of a phase shift mask having a phase shifter defect.

FIG. 25 is a schematic view showing a part of the manufacturing process of a phase shift mask which is another embodiment of the present invention.

FIG. 26 is a schematic view showing a part of the manufacturing process of a phase shift mask which is another embodiment of the present invention.

FIG. 27 is a schematic view showing a part of a cross section of a phase shift mask which is another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Mask substrate, 2 ... Antistatic film, 3 ... 1st phase shifter, 4 ... 2nd phase shifter, 4 '... 2nd phase shifter,
4 ″ ... second phase shifter, 5 ... phase shifter defective portion,
5 '... phase shifter defective portion, 6 ... phase shifter residual defect,
Reference numeral 7 ... Shading film, 8 ... Transmission pattern region not provided with phase shifter, 9 ... Transmission pattern region provided with phase shifter, 10 ...
A first transparent pattern area, 11 ... a second transparent pattern area,
12 ... Third transparent pattern region, 15 ... Transparent pattern, 21
... synthetic quartz substrate, 22 ... transparent conductive film, 23 ... chrome film, 24 ... phase shifter pattern, 25 ... second coating type glass film, 26 ... electron beam, 27 ... second phase shifter pattern,
28 ... Phase shifter defect, 29 ... Second phase shifter defect.

Claims (15)

[Claims] 1. A step of forming a predetermined light-shielding pattern on a transparent substrate, a step of forming a first transparent thin film pattern for giving a phase difference to exposure light, and a negative radiation-sensitive material on the substrate. And a step of irradiating a region over the part of the first transparent thin film pattern and the substrate with active actinic radiation, and removing a region not irradiated with active actinic radiation of the coat. And a step of forming a second transparent thin film pattern for gradually changing the phase difference given to the exposure light transmitted through the opening. 2. The mask manufacturing method according to claim 1, wherein the negative radiation-sensitive material is a material containing at least a coating silicon compound containing a residual silanol group. 3. The mask manufacturing method according to claim 1, wherein the negative-type radiation-sensitive material is a material containing at least an acid generator and a coatable silicon compound containing a residual silanol group. 4. A step of forming a predetermined light-shielding pattern on a transparent substrate, a step of forming a first transparent thin film pattern for giving a phase difference to exposure light, and a coating made of a radiation-sensitive material on the substrate. A step of forming a film, a step of irradiating an area not including an area extending over a part of the first transparent thin film pattern and the substrate with an active actinic ray, and removing an active actinic ray irradiation area of the coating film. And a step of forming a second transparent thin film pattern for gradually changing the phase difference given to the exposure light passing through the opening portion. 5. A heat treatment step is performed after removing the active actinic radiation-irradiated region of the coating film, as a means for gradually changing the phase difference given to the exposure light passing through the opening portion. Item 5. The mask manufacturing method according to Item 1 or 4. 6. The second transparent thin film according to claim 1, 2, 3 or 4, wherein the thickness of the second transparent thin film is formed so that a phase difference given to exposure light is 90 ° or less. The described mask manufacturing method. 7. A step of forming a coating film made of a negative-type radiation-sensitive material on a first transparent thin film pattern which imparts a phase difference to exposure light, and a region including a defective portion of the first transparent thin film pattern. A step of irradiating with active actinic radiation, and a step of forming a second transparent thin film pattern that gives a phase difference of 90 ° or less to the exposure light by removing a region not irradiated with active actinic radiation of the coating film. Characteristic mask defect correction method. 8. A step of forming a coating film made of a negative-type radiation-sensitive material on a first transparent thin film pattern which gives a phase difference to exposure light, and a region including a defective portion of the first transparent thin film pattern. A step of irradiating with active actinic radiation, and a step of forming a second transparent thin film pattern which gives a phase difference in the range of 270 ° to 450 ° to the exposure light by removing a region not irradiated with active actinic radiation of the coating film. A method of repairing a mask defect, comprising: 9. A step of forming a coating film made of a negative-type radiation-sensitive material on a first transparent thin film pattern which imparts a phase difference to exposure light, and a region including a defective portion of the first transparent thin film pattern. The step of irradiating with actinic rays and the exposure light from 90 ° to 2 °
And a step of forming a second transparent thin film pattern which gives a phase difference in the range of 70 °. 10. The mask defect repairing method according to claim 8, wherein the negative-type radiation sensitive material is a material containing at least a coating silicon compound containing residual silanol groups. 11. The negative-type radiation-sensitive material is a material containing at least an acid generator and a coatable silicon compound containing a residual silanol group.
The mask defect repairing method described in 0. 12. A step of forming a coating film made of a radiation-sensitive material on a first transparent thin film pattern which imparts a phase difference to exposure light, and active in a region of the first transparent thin film pattern which does not include a defective portion. And a step of forming a second transparent thin film pattern that gives a phase difference of 90 ° or less to the exposure light by removing the active actinic ray irradiation region of the coating film. Mask defect repair method. 13. A step of forming a coating film made of a radiation-sensitive material on a first transparent thin film pattern which imparts a phase difference to exposure light, and active in a region of the first transparent thin film pattern which does not include a defective portion. The step of irradiating with actinic rays and removing the active actinic ray irradiating region of the coating film make exposure light from 270 ° to 4 °
And a step of forming a second transparent thin film pattern that gives a phase difference in the range of 50 °. 14. A step of forming a coating film made of a radiation-sensitive material on a first transparent thin film pattern which imparts a phase difference to exposure light, and active in a region of the first transparent thin film pattern which does not include a defective portion. The step of irradiating with actinic rays and removing the active actinic ray irradiating region of the coating film can change the exposure light from 90 ° to 27 °.
And a step of forming a second transparent thin film pattern that gives a phase difference in the range of 0 °. 15. The heat treatment step is performed after removing the active actinic ray irradiation region of the coating film, as a means for forming a second transparent thin film that gives a phase difference to the exposure light. , 9, 10, 11, 12, 13, 14 or 15, the mask defect repairing method.