JPH05307258A - Photomask and its production - Google Patents

Abstract

PURPOSE:To improve the pattern transfer accuracy of the phase shift mask by a multistage system and to simplify the process for production of the phase shift mask by the multistage system. CONSTITUTION:This phase shift mask 1 is arranged with phase shifters 5 and 90 deg. shifters 6 respectively in a part of transmission regions 4. The opening width of a part of the transmission regions 4 is deliberately expanded and the 90 deg. shifters 6 are arranged therein, by that, the decrease in the exposure in the corresponding region on a semiconductor wafer is lessened. The phase shifters 5 and the 90 deg. shifters 6 are formed by the same process for production, by that the process for production of the phase shift mask 1 of the multistage system is simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used in a semiconductor manufacturing process and the like, and more particularly to a technology effectively applied to a phase shift mask.

[0002]

2. Description of the Related Art In recent years, in a VLSI manufacturing process that requires a technique for processing a fine pattern of 0.5 μm to 0.3 μm or less, the phase of light passing through a photomask is reversed to increase the contrast of a projected image. The introduction of improving phase shift technology is under consideration.

Various methods have been proposed for the above-mentioned phase shift technique. As a typical example thereof, the phase of transmitted light is changed by 180 degrees in one of a pair of transmission regions sandwiching a light shielding region on a photomask. There is a so-called Levenson method (Japanese Patent Laid-Open No. 62-50811) in which a phase shifter is arranged.

However, the Levenson method is
The phase shifter cannot be arranged without contradiction in a pattern in which the transmissive region 4 and the light shielding region 3 are complicatedly combined as shown in FIG. Further, for example, in the “h” type pattern as shown in FIG. 25, the phase shifter cannot be arranged in a part of the transmissive region 4, and in order to use the positive type photoresist, double exposure is required. There are many practical restrictions.

Therefore, a so-called multi-stage system has been proposed as a system for solving the above-mentioned restrictions of the Levenson system. This is a phase shifter that changes the phase of transmitted light by 90 degrees (hereinafter referred to as a 90 degree shifter) or a phase shifter that changes stepwise from 0 degree to 180 degrees (hereinafter, a tilt shifter) around a normal phase shifter. 25). For example, in the case of the “h” type pattern shown in FIG. 25, the phase shifters 5 and 90 are placed at the positions shown in FIG.
Degree shifters (or tilt shifters) 6 are arranged respectively.

[0006]

However, in the above-described multi-stage phase shift mask, when the 90-degree shifter (or tilt shifter) is arranged in the transmissive region having a narrow pattern width, the corresponding region on the semiconductor wafer is not formed. Since the exposure amount is reduced, there is a problem that the pattern transfer accuracy is reduced.

In order to manufacture a multi-stage phase shift mask, a normal phase shifter is formed, and then a part thereof is locally etched using a focused ion beam (FIB) to form a 90 ° shifter. Or, after forming a normal phase shifter, a film is locally deposited in its vicinity by using an ion assisted CVD method or an optical CVD method.
Since it is necessary to form the 0-degree shifter, there is a problem that not only an apparatus such as a FIB apparatus or a CVD apparatus is required but also the photomask manufacturing process becomes complicated.

Therefore, an object of the present invention is to provide a technique capable of arranging a 90-degree shifter (or a tilt shifter) in a part of a transmissive region without lowering the pattern transfer accuracy of a photomask. ..

Another object of the present invention is to provide a technique capable of simplifying the manufacturing process of a photomask having a 90-degree shifter (or tilt shifter).

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0011]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

In the multi-stage phase shift mask according to the present invention, a 90-degree shifter (or a tilt shifter) is arranged in a transmission area having a wide opening width, or an opening of a transmission area in which a 90-degree shifter (or a tilt shifter) is arranged. It is an expanded version.

In order to form a multi-stage phase shift mask, as an example, a thin film as a phase shifter material is deposited on a glass substrate on which predetermined light-shielding regions and transmission regions are formed respectively, and then a predetermined film is formed on the thin film. Resist is used as a mask, and then the thin film is anisotropically etched using the resist as a mask, and then the resist is isotropically receded to reduce the area thereof, and then the small area resist is used. Is used as a mask to anisotropically etch a part of the thin film.

[0014]

According to the phase shift mask described above, it is possible to reduce the decrease in the exposure amount in the corresponding region on the semiconductor wafer, so that it is possible to improve the pattern transfer accuracy of the multi-stage phase shift mask. ..

Further, according to the above-described method of manufacturing the phase shift mask, the phase shifter and the second phase shifter can be formed in the same manufacturing process, so that the manufacturing process of the multi-stage phase shift mask is simplified. Can be converted.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of an essential part of a multi-stage phase shift mask 1 according to an embodiment of the present invention, and FIG.
It is sectional drawing in the II line.

This phase shift mask 1 is a reticle for transferring a predetermined integrated circuit pattern onto a semiconductor wafer, for example, on which an original image of the integrated circuit pattern having a size five times the actual size is formed.

In the effective exposure area on the transparent glass substrate 2 made of synthetic quartz having a refractive index of about 1.47, a transmission area 4 surrounded by a light shielding area 3 made of a metal film such as chromium or chromium oxide. It is provided. This transparent area 4
Consists of, for example, "h", "i" and "T" shaped patterns.

A portion of the "h" shaped transmission region 4 and "i"
A phase shifter 5 that changes the phase of transmitted light by 180 degrees is arranged on the entire surface of the transparent region 4 of the shape. A 90-degree shifter 6 for changing the phase of transmitted light by 90 degrees is arranged in a part of the “h” -shaped transmission area 4. Neither the phase shifter 5 nor the 90-degree shifter 6 is arranged in the “T” -shaped transmission region 4. With these, the transmissive region 4 except for the region where the 90-degree shifter 6 is arranged is configured such that the phases of the exposure light transmitted through the adjacent regions are changed by 180 degrees.

The phase shifter 5 and the 90-degree shifter 6
Consists of a transparent thin film such as spin-on-glass. When the wavelength of the exposure light is λ, the refractive index of the exposure atmosphere is n ₀ , and the refractive index of the phase shifter 5 is n ₁ , the film thickness (d ₁ ) of the phase shifter 5 is d ₁ ≈ [λ / 2 (n ₁ −n ₀ )]. The film thickness (d ₂ ) of the 90-degree shifter 6 is set so that d ₂ ≉ [λ / 4 (n ₁ −n ₀ )].

In this embodiment, when the 90-degree shifter 6 is arranged in a part of the "h" -shaped transmission region 4, the 90-degree shifter 6 is arranged in a region having a wide opening width. As a result, it is possible to reduce the decrease in the exposure amount in the corresponding region on the semiconductor wafer, and thus it is possible to improve the pattern transfer accuracy of the phase shift mask 1.

Phase shift mask 1 shown in FIGS. 3 and 4.
Is an example in which the opening width of a part of the transmissive region 4 is intentionally enlarged, and the 90-degree shifter 6 is disposed therein. Also in this case, it is possible to reduce the decrease in the exposure amount in the corresponding region on the semiconductor wafer, so that it is possible to improve the pattern transfer accuracy of the phase shift mask 1.

FIG. 5 shows an embodiment in which the phase shifter 5 and the 90-degree shifter 6 are arranged in a part of the transmissive region 4 formed of a plurality of rectangular patterns. Also in this case, by arranging the 90-degree shifter 6 in a region having a large opening width, it is possible to reduce the decrease in the exposure amount in the corresponding region on the semiconductor wafer.

FIG. 6 shows an embodiment in which the phase shifter 5 and the 90-degree shifter 6 are arranged in a part of the transmissive region 4 of the pattern shown in FIG. Again,
By arranging the 90-degree shifter 6 in a region having a wide opening width or arranging the 90-degree shifter 6 in a region having a wide opening width, it is possible to reduce a decrease in the exposure amount in a corresponding region on the semiconductor wafer. it can.

Next, an embodiment of the method of manufacturing the phase shift mask 1 will be described with reference to FIGS.

First, as shown in FIG. 7, a spin-on-glass film 7 is spun on a glass substrate 2 on which a light-shielding region 3 and a transmissive region 4 are respectively formed by a known photomask manufacturing method using an electron beam drawing method or the like. After coating, a resist 8 having a predetermined pattern is formed on the spin-on-glass film 7.
To form.

In this case, the film thickness (d ₁ ) of the spin-on-glass film 7 is expressed by the following equation: d ₁ ≈ [λ / 2 (n ₁ −n ₀ )] (where λ is the wavelength of the exposure light and n ₀ Is the refractive index of the exposure atmosphere, and n ₁ is the refractive index of the spin-on glass)
Is set to satisfy.

Next, as shown in FIG.
After the spin-on-glass film 7 is anisotropically etched by using as a mask, the resist 8 is isotropically retracted by ashing using oxygen or ozone to reduce its area, as shown in FIG.

Next, as shown in FIG. 10, a part of the spin-on-glass film 7 is anisotropically etched by using the resist 8 having a small area as a mask to halve the film thickness of the resist film. A phase shifter 5 is formed in the lower part of 8, and a 90 degree shifter 6 is formed around the phase shifter 5. After that, the resist 8 on the phase shifter 5 is removed by ashing or the like to complete the phase shift mask 1 shown in FIGS.

According to the manufacturing method described above, the phase shifter 5
Since the 90 ° shifter 6 and the 90 ° shifter 6 can be formed in the same process, the manufacturing process of the multi-stage phase shift mask 1 can be simplified. Further, when forming the 90-degree shifter 6, a FIB device, a CVD device, etc. are not necessary.

According to the manufacturing method described above, the 90-degree shifter 6 is formed on the entire periphery of the phase shifter 5 including the upper portion of the light shielding region 3. Therefore, in order to prevent the pattern transfer accuracy from being deteriorated due to a part of the 90-degree shifter 6 being arranged over the adjacent transmissive region 4,
The width of the 0-degree shifter 6 needs to be smaller than the minimum width of the light shielding region 3.

Next, another embodiment of the method for manufacturing the phase shift mask 1 will be described with reference to FIGS.

In this embodiment, when the spin-on-glass film 7 is spin-coated on the glass substrate 2 on which the light-shielding region 3 and the transmissive region 4 are respectively formed, as shown in FIG. 7a and the upper spin-on-glass film 7b, and a thin etching stopper layer 9 is provided between them. A resist 8 having a predetermined pattern is formed on the upper spin-on-glass film 7b.

The etching stopper layer 9 is made of a material having an etching rate different from that of spin-on-glass, for example, a silicon nitride film. In this case, the film thickness (d ₁ ) of each of the lower spin-on-glass film 7a and the upper spin-on-glass film 7b is represented by the following formula d ₁ ≈ [λ / 4 (n ₁ −n ₀ )] (where λ is the exposure (Wavelength of light, n ₀ represents the refractive index of the exposure atmosphere, and n ₁ represents the refractive index of spin-on-glass)
Is set to satisfy.

Next, as shown in FIG. 12, the upper spin-on-glass film 7b is isotropically etched using the resist 8 as a mask to form the phase shifter 5, and then the phase shifter 5 is formed.
As shown in FIG. 13, by etching the etching stopper layer 9 using the resist 8 as a mask, the etching stopper layer 9 is left only under the resist 8.

Next, as shown in FIG. 14, the lower spin-on-glass film 7a is anisotropically etched by using the etching stopper layer 9 as a mask to thin the lower spin-on-glass film 7a around the phase shifter 5. The phase shift mask 1 is completed by forming the 90-degree shifter 6 made of a laminated film with the etching stopper layer 9 and then removing the resist 8 on the phase shifter 5. In addition,
When etching the lower spin-on-glass film 7a, the resist 8 may be used as a mask.

According to the above manufacturing method, the phase shifter 5
Since the 90 ° shifter 6 and the 90 ° shifter 6 can be formed in a continuous process, the manufacturing process of the multi-stage phase shift mask 1 can be simplified. Further, when forming the 90-degree shifter 6, a FIB device, a CVD device, etc. are not necessary.

In the manufacturing method shown in FIGS. 15 to 17, the lower spin-on-glass film 7a and the upper spin-on-glass film 7a and the upper spin-on-glass film 7a are replaced by the thin etching stopper layer 9 provided between the lower spin-on-glass film 7a and the upper spin-on-glass film 7b. In this example, the spin-on-glass film 7b and the spin-on-glass film 7b are made of spin-on-glass having different etching rates.

As a combination of spin-on-glasses having different etching rates, spin-on-glass baked at a low temperature and spin-on glass baked at a high temperature can be exemplified.

In this case, as shown in FIG. 16, the upper spin-on-glass film 7b is isotropically etched by using the resist 8 as a mask to form the phase shifter 5, and then as shown in FIG. The lower spin-on-glass film 7a is anisotropically etched using the resist 8 as a mask to form a 90-degree shifter 6 composed of the lower spin-on-glass film 7a around the phase shifter 5.

According to the manufacturing method described above, the phase shifter 5
Since the 90 ° shifter 6 and the 90 ° shifter 6 can be formed in the same process, the manufacturing process of the multi-stage phase shift mask 1 can be simplified. Further, when forming the 90-degree shifter 6, a FIB device, a CVD device, etc. are not necessary.

In the manufacturing method shown in FIGS. 18 to 19, instead of the above-described manufacturing method, first, the upper spin-on-glass film 7b is anisotropically etched using the photoresist 8 as a mask (FIG. 18), and thereafter. The lower spin-on-glass film 7a is isotropically etched using the resist 8 as a mask to form a 90-degree shifter 6 composed of an upper spin-on-glass film 7b around the phase shifter 5.

Also in this case, since the phase shifter 5 and the 90-degree shifter 6 can be formed in the same step, the manufacturing process of the multi-stage phase shift mask 1 can be simplified. Further, when forming the 90-degree shifter 6, a FIB device, a CVD device, etc. are not necessary.

In the manufacturing method shown in FIG. 20, the resist 8 is used as a mask to etch the spin-on-glass film 7 isotropically, and then the glass substrate 2 is etched using the resist 8 and the light-shielding film as a mask. 5 and 9
The 0 degree shifter 6 and the 0 degree shifter 6 are formed in the same step.

In this case, the film thickness (d ₁ ) of the spin-on-glass film 7 is expressed by the following equation: d ₁ ≈ [λ / 4 (n ₁ −n ₀ )] (where λ is the wavelength of the exposure light and n ₀ Is the refractive index of the exposure atmosphere, and n ₁ is the refractive index of the spin-on glass)
And the digging depth (d ₃ ) when etching the glass substrate 2 is set to satisfy the following equation: d ₃ ≈ [λ / 4 (n ₃ −n ₀ )] (where λ is The wavelength of the exposure light, n ₀ represents the refractive index of the exposure atmosphere, and n ₃ represents the refractive index of the glass substrate 2).

Further, according to this method, an etching stopper layer is provided at a predetermined depth of the glass substrate 2, or a thin film layer made of a material different from glass is formed between the light shielding film and the glass substrate 2. You may dig in a thin film layer.

In the manufacturing method shown in FIG. 21, a lower spin-on-glass film 7a and an upper spin-on-glass film 7b having different etching rates are laminated under the light-shielding film, and first, the resist 8 is used as a mask to form the upper spin-on-glass film. After the anisotropic etching of 7b, the lower spin-on-glass film 7a is isotropically etched by using the resist 8 and the light-shielding film as a mask, so that the phase shifter 5 and the 90-degree shifter 6 are formed using the same mask. To form.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

In the above-described embodiment, the case where the 90-degree shifter for changing the phase of the transmitted light by 90 degrees is formed around the phase shifter. However, as shown in FIG. 22, the transmitted light is transmitted around the phase shifter 5. It can also be applied to the case of forming the tilt shifter 10 in which the phase is changed stepwise from 0 degree to 180 degrees.

The tilted shifter 10 can be formed by using the well-known low selective etching method or sputter etching method without using an FIB apparatus, a CVD apparatus or the like.

In the above-mentioned embodiment, the case where the present invention is applied to the phase shift mask using the negative type photoresist is explained, but it is also applicable to the phase shift mask using the positive type photoresist.

FIG. 23 shows the present invention in a phase shift mask 1 in which the same pattern as the pattern formed in the phase shift mask shown in FIGS. 3 and 4 is transferred onto a semiconductor wafer by using a positive photoresist. It is the applied example.

In this case, the reduction of the exposure dose in the corresponding region on the semiconductor wafer may be reduced by enlarging the minimum width portion of the transmissive region 3 in which the 90-degree shifter 6 is arranged.

In the above-mentioned embodiment, the case where the phase shifter and the 90-degree shifter are made of the spin-on-glass film has been described, but the phase shifter and the 90-degree shifter are made of other materials,
For example, it can also be applied to the case where it is composed of a silicon oxide film deposited by the CVD method.

[0055]

The effects obtained by the typical ones of the inventions disclosed in this application will be briefly described as follows.
It is as follows.

According to the present invention, it is possible to reduce the reduction of the exposure amount in the corresponding region on the semiconductor wafer, and therefore it is possible to improve the pattern transfer accuracy of the multi-stage phase shift mask.

According to the present invention, the phase shifter and the second phase shifter can be formed in the same manufacturing process, so that the manufacturing process of the multi-stage phase shift mask can be simplified.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of a phase shift mask that is an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a plan view of a main portion of a phase shift mask that is another embodiment of the present invention.

4 is a sectional view taken along line VI-VI in FIG.

FIG. 5 is a plan view of a main portion of a phase shift mask which is another embodiment of the present invention.

FIG. 6 is a plan view of a main part of a phase shift mask which is another embodiment of the present invention.

FIG. 7 is a cross-sectional view of an essential part of a glass substrate showing an embodiment of a method of manufacturing a phase shift mask according to the present invention.

FIG. 8 is a cross-sectional view of a main part of a glass substrate showing an embodiment of a method of manufacturing a phase shift mask according to the present invention.

FIG. 9 is a cross-sectional view of a main part of a glass substrate showing an embodiment of a method of manufacturing a phase shift mask according to the present invention.

FIG. 10 is a cross-sectional view of a main part of a glass substrate, showing an embodiment of a method of manufacturing a phase shift mask according to the present invention.

FIG. 11 is a cross-sectional view of a main part of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 12 is a fragmentary cross-sectional view of a glass substrate showing another embodiment of the method of manufacturing a phase shift mask according to the present invention.

FIG. 13 is a cross-sectional view of a main part of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 14 is a cross-sectional view of a main part of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 15 is a fragmentary cross-sectional view of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 16 is a cross-sectional view of an essential part of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 17 is a fragmentary cross-sectional view of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 18 is a fragmentary cross-sectional view of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 19 is a fragmentary cross-sectional view of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 20 is a cross-sectional view of essential parts of a glass substrate, showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 21 is a cross-sectional view of a main part of a glass substrate showing another embodiment of the method for manufacturing a phase shift mask according to the present invention.

FIG. 22 is a cross-sectional view of essential parts of a phase shift mask that is another embodiment of the present invention.

FIG. 23 is a plan view of a principal portion of a phase shift mask which is another embodiment of the present invention.

FIG. 24 is a plan view of a main part of a conventional phase shift mask.

FIG. 25 is a main-portion plan view showing an example of a pattern of a phase shift mask.

FIG. 26 is a plan view of a main part of a conventional phase shift mask.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Phase shift mask 2 Glass substrate 3 Light-shielding area 4 Transmission area 5 Phase shifter 6 90 degree shifter 7 Spin on glass film 7a Lower spin on glass film 7b Upper spin on glass film 8 Resist 9 Etching stopper layer 10 Tilt shifter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Moriuchi 2326 Imai, Ome-shi, Tokyo Inside the Device Development Center, Hitachi, Ltd. (72) Masayuki Morita 5-20-1 Mizumizuhonmachi, Kodaira-shi, Tokyo Date Tatsucho LSI Engineering Co., Ltd. (72) Inventor Yuichi Soda 2-6-2, Otemachi, Chiyoda-ku, Tokyo Inside Ritsudenshi Engineering Co., Ltd. (72) Inventor Seiichiro Shirai Imai, Ome, Tokyo 2326 Address Hitachi, Ltd. Device Development Center

Claims (7)

[Claims] 1. A phase shifter for changing a phase of transmitted light by 180 degrees in a part of a transmission region on a glass substrate, and a phase of changed by 90 degrees for the transmitted light, or for changing the phase of the transmitted light stepwise from 0 degree to 180 degrees. A photomask in which second phase shifters are respectively arranged, wherein the second phase shifter is arranged in a transmissive region having a wide opening width. 2. A phase shifter for changing a phase of transmitted light by 180 degrees in a part of a transmission area on a glass substrate and a phase shifter for changing the phase of transmitted light by 90 degrees, or changing the phase of the transmitted light stepwise from 0 degree to 180 degrees. A photomask in which second phase shifters are arranged, wherein the opening width of the transmissive region in which the second phase shifter is arranged is widened. 3. The photomask according to claim 1, wherein the width of the second phase shifter is smaller than the minimum width of the transmissive region or the light shielding region. 4. The method of manufacturing a photomask according to claim 1, 2 or 3, wherein after depositing a thin film as a phase shifter material on a glass substrate on which a predetermined light-shielding region and a predetermined light-transmitting region are respectively formed, Forming a resist having a predetermined pattern on the thin film, anisotropically etching the thin film using the resist as a mask, and then retracting the resist isotropically to reduce the area thereof. A method of manufacturing a photomask, comprising the steps of anisotropically etching a part of the thin film using a resist having an area as a mask to form a phase shifter and a second phase shifter, respectively. 5. The method of manufacturing a photomask according to claim 1, 2 or 3, wherein a first thin film as a phase shifter material is deposited on a glass substrate on which a predetermined light-shielding region and a predetermined light-transmitting region are formed. After that, a step of depositing a thin etching stopper layer on the first thin film, a second thin film serving as a phase shifter material on the etching stopper layer, and then a predetermined film on the second thin film. A step of forming a pattern resist, a step of forming a phase shifter by isotropically etching the second thin film using the resist as a mask, the etching stopper layer and the first mask using the resist as a mask A photomask comprising a step of forming a second phase shifter around the phase shifter by anisotropically etching the thin film. Production method. 6. The method of manufacturing a photomask according to claim 1, 2 or 3, wherein first and second etching rates differ from each other on a glass substrate on which a predetermined light-shielding region and a predetermined light-transmitting region are formed. After depositing each thin film, a step of forming a resist having a predetermined pattern on the second thin film, and isotropically etching the second thin film using the resist as a mask to form a phase shifter. A step of forming a second phase shifter around the phase shifter by anisotropically etching the first thin film using the photoresist as a mask, and manufacturing the photomask. Method. 7. The method of manufacturing a photomask according to claim 1, 2, or 3, wherein the first and second etching rates differ from each other on a glass substrate on which a predetermined light-shielding region and a predetermined light-transmitting region are formed, respectively. After depositing each of the thin films, a step of forming a photoresist having a predetermined pattern on the second thin film, a phase shifter by anisotropically etching the second thin film using the photoresist as a mask. Forming a second phase shifter around the phase shifter by isotropically etching the first thin film using the photoresist as a mask Production method.