JPH05142747A - Production of photomask - Google Patents

Abstract

PURPOSE:To improve the production yield of the photomask for phase shift and to shorten the time for producing the photomask for phase shift. CONSTITUTION:A transparent film 4 to constitute a phase shifter material is deposited over the entire surface of the 1st photomask P1 to be formed with phase shifters and thereafter, phase shift patterns 3 consisting of a light shielding film formed on the 2nd photomask P2 are transferred onto the 1st photomask P1 by using a light exposing technique and the phase shifters are formed on the 1st photomask P1 by processing the transparent film 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask (reticle) manufacturing technique used in a manufacturing process (wafer process) of a semiconductor integrated circuit device, and is particularly effective when applied to a phase shift photomask. Regarding technology.

[0002]

2. Description of the Related Art As semiconductor integrated circuits become finer and the design rules for elements and wiring are on the order of submicrons, i
In the photolithography process of transferring an integrated circuit pattern on a photomask onto a semiconductor wafer by using light such as a line (wavelength 365 nm), deterioration of pattern accuracy becomes a serious problem.

That is, when a pattern composed of a light-transmitting region and a light-shielding region on a photomask is transferred onto a wafer, two lights transmitted through each of the pair of light-transmitting regions sandwiching the light-shielding region are , The two light beams interfere with each other at their boundaries and intensify each other on the wafer.

As a result, the contrast of the projected image of the pattern on the wafer is lowered and the depth of focus is reduced, so that the transfer accuracy of a fine pattern having a wavelength of light is significantly reduced. become.

Therefore, as a means for improving such a problem, a phase shift technique for improving the contrast of a projected image by changing the phase of light passing through a photomask has been attracting attention.

For example, in Japanese Examined Patent Publication No. 62-59296, a phase shifter composed of a transparent thin film is provided in one of a pair of light transmission areas sandwiching a light shielding area on a photomask, and the phase shifter is transmitted through the pair of light transmission areas. There is disclosed a phase shift photomask in which the intensity of light at the boundary between the two lights on the wafer is weakened by making the phases of the two lights opposite to each other.

Further, in Japanese Unexamined Patent Publication No. 62-67514, a minute light transmitting region having a light resolution or less is provided around a light transmitting region on a photomask, and a phase is provided in one of the light transmitting regions. A phase shift photomask is disclosed in which a shifter is provided and the phases of two lights transmitted through the pair of light transmission regions are made opposite to each other to improve the pattern transfer accuracy.

Further, in Japanese Patent Laid-Open No. 2-140743, a phase shifter is provided in a part of a light transmission region on a photomask, and two phases of light transmitted through a portion with the phase shifter and a portion without the phase shifter are provided. By making the opposite phases of
A photomask for phase shift that improves pattern transfer accuracy is disclosed.

Conventionally, these phase shift photomasks are manufactured by the following method.

First, an electron beam resist is spin-coated on a glass substrate (mask blanks) having a light-shielding film such as Cr vapor-deposited on its entire surface, and a latent image of an integrated circuit pattern is formed on the electron beam resist using an electron beam drawing apparatus. After the formation, the electron beam resist is developed, and the light-shielding film is etched using the resist pattern remaining on the light-shielding film as a mask to form a normal photomask.

Then, a transparent film such as Spin On Glass, which is a phase shifter material, is deposited on the entire surface of the photomask, and an electron beam resist is spin-coated on the transparent film. Then, after forming a latent image of the phase shift pattern on the electron beam resist using an electron beam drawing apparatus, the electron beam resist is developed, the transparent film is etched using the resist pattern remaining on the transparent film as a mask, A phase shifter is formed in a predetermined light transmitting area of the photomask.

In order to make the phases of the light transmitted through the light transmission region where the phase shifter is formed and the light transmitted through the light transmission region where the phase shifter is not formed opposite to each other, the wavelength of the light is λ and the phase is With the refractive index of the shifter as n, the film thickness (d) of the phase shifter is set so as to satisfy the relationship of d = λ / 2 (n−1).

For example, when the wavelength of light is 365 nm (i-line) and the refractive index of spin-on-glass, which is a phase shifter material, is 1.5, the film thickness of the phase shifter is about 365 nm.

[0014]

The above-described method of manufacturing the phase shift photomask has the following problems.

First, in the process of manufacturing a photomask for phase shift, an electron beam drawing apparatus is used both when exposing a resist deposited on a light-shielding film and when exposing a resist deposited on a transparent film. To do.

In this case, since the light-shielding film is made of a conductive material such as Cr, there is no problem of charging, but the transparent film is made of an insulating material such as spin-on-glass, so that the transparent film is charged at the time of exposure and the electron There is a problem that the beam is deflected and the drawing accuracy is lowered. Therefore, in the manufacturing process of the phase shift photomask, it is essential to take measures to prevent the transparent film from being charged.

Further, in electron beam drawing, it is necessary to reduce the film thickness of the electron beam resist to about 0.3 to 0.5 μm in order to improve drawing accuracy. Therefore, the adhesiveness between the electron beam resist and the transparent film is lowered, and the resist is locally peeled off. As a result, a portion which should remain on the photomask is etched, so-called white defect is likely to occur.

Further, unlike the light exposure apparatus, the electron beam drawing apparatus irradiates the resist with an electron beam in a vacuum atmosphere, so that fine dust is easily generated due to pressure fluctuations when the photomask is taken in and out of the apparatus. If the dust adheres to the photomask, it may cause defects.

It is extremely difficult to repair defects, especially white defects, generated in the phase shifter. This is because it is necessary to adjust the film thickness, refractive index, and transparency of the phase shifter before and after the correction to correct the defects that occur in the phase shifter, so higher correction accuracy is required than in the normal photomask defect correction. Because it is done.

Therefore, in the manufacturing process of the photomask for phase shift, it is necessary to suppress the occurrence of defects as much as possible.

Further, since electron beam drawing is a method of drawing a pattern by scanning one electron beam, it takes not only a long time to manufacture one phase-shifting photomask, but also the same pattern. When a plurality of phase shift photomasks are manufactured, the manufacturing time increases in proportion to the number.

That is, when a plurality of phase-shifting photomasks having the same pattern are manufactured, and only the light-shielding pattern unrelated to the phase-shifting pattern is repaired, the phase-shifting pattern has uncorrectable defects. For example, when peeling off the phase shifter and starting again from the transparent film application,
In either case, the time required for forming the phase shift pattern is the same as that for manufacturing the first one phase shift photomask.

As described above, in the manufacturing process of the phase shift photomask, the total time until the phase shift photomask is finally completed and the time occupied by the electron beam drawing apparatus become extremely long. Therefore, it is necessary to shorten this time as much as possible.

Therefore, an object of the present invention is to provide a technique capable of improving the manufacturing yield of phase shift photomasks.

Another object of the present invention is to provide a technique capable of reducing the time required for manufacturing a phase shift photomask.

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.

[0027]

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 method of manufacturing a phase shift photomask according to the present invention, a first photomask on which a phase shifter is to be formed and a second photomask in which a phase shift pattern is formed of a light-shielding film are prepared. After a transparent film, which will be the phase shifter material, is applied to the entire surface of one photomask, the phase shift pattern formed on the second photomask is transferred to the first photomask all at once using the optical exposure technique and is transparent. This is a method of forming a phase shifter on the first photomask by processing the film.

[0029]

According to the above-mentioned means, the phase shift pattern formed on the second photomask is collectively transferred to the first photomask by using the light exposure technique, so that the transparent film is prevented from being charged during the exposure. be able to.

Further, since the photoresist can be thickened by the light exposure, the adhesion between the photoresist and the transparent film is improved, and the local peeling of the resist can be prevented.

Further, since the photoexposure device irradiates the photoresist with exposure light under normal pressure, it is possible to avoid generation of dust due to pressure fluctuation when the photomask is taken in and out of the device.

According to the above-mentioned means, the phase shift patterns formed on the second photomask are collectively transferred to the first photomask by using the light exposure technique, so that a plurality of phase shift photomasks having the same pattern are formed. When making one,
In any case, such as when repairing only the light-shielding pattern that is unrelated to the phase shift pattern or when the phase shifter has a defect that cannot be repaired and the phase shifter is peeled off and the transparent film is coated again, The time required to form the shift pattern can be significantly reduced.

Further, since the phase shift pattern of the second photomask is composed of the light-shielding film, the defect correction of the phase shift pattern can be performed by using the ordinary defect correction technique of the photomask.

[0034]

EXAMPLES A method of manufacturing a phase shift photomask according to an example of the present invention will be described below.

FIG. 1 shows a _first photomask P _{1 on} which a phase shifter is formed. FIG. 1 (a) is a plan view of the main part thereof, and FIG. 1 (b) is IA-IA of FIG. 1 (a). It is sectional drawing in a line. The photomask P ₁ is a reticle for transferring a predetermined integrated circuit pattern onto a semiconductor wafer, for example, on which an original image of an integrated circuit pattern having a size five times the actual size is formed, and is hereinafter referred to as a working reticle.

For example, light-shielding patterns 2a to 2c are formed on the main surface of the working reticle P ₁ formed of a transparent synthetic quartz glass substrate 1 having a refractive index of about 1.47. These light-shielding patterns 2a to 2c form, for example, part of a wiring pattern that connects semiconductor elements.

The light shielding patterns 2a to 2c have, for example, 5
It is composed of a Cr film having a film thickness of about 00 to 3000 Å. The width of each of the light shielding patterns 2a to 2c and the interval between them are, for example, about 1.5 to 2.5 μm.

To form the light-shielding patterns 2a to 2c on the main surface of the glass substrate 1, a Cr film is deposited on the entire surface of the glass substrate 1 by using, for example, a sputtering method, and then a positive type film is formed on the entire surface of the Cr film. The electron beam resist is spin coated.

Next, after forming latent images of the light-shielding patterns 2a to 2c on the electron beam resist by using an electron beam drawing apparatus (not shown), the electron beam resist is developed to remove the exposed portion, and then the Cr film is formed. The Cr film is etched using the resist pattern remaining on the mask as a mask.

After that, the light-shielding patterns 2a to 2c are inspected for defects, and if any defects are present, the defects are corrected by a conventional method.

[0041] Figure 2 illustrates in the working reticle P ₁ for transferring a phase shift pattern, for example, the second photomask P ₂ to the original phase shift pattern of the actual size of 5 times the dimension are formed, the Figure (a) is a plan view of the main part,
FIG. 2B is a sectional view taken along line IIB-IIB in FIG. Hereinafter, this photomask P ₂ is referred to as a master reticle.

Like the working reticle P ₁ , the master reticle P ₂ is composed of a transparent synthetic quartz glass substrate 1 having a refractive index of about 1.47, for example. On the main surface of the glass substrate 1, for example, 500 to 3000
The phase shift pattern 3 made of a Cr film having a film thickness of about Å is formed.

The phase shift pattern 3 is formed by the same method as the light shielding patterns 2a to 2c.
That is, a positive type electron beam resist is spin-coated on a glass substrate 1 having a Cr film deposited on the entire surface, and a latent image of a phase shift pattern 3 is formed on the electron beam resist by using an electron beam drawing apparatus. The line resist is developed, and the Cr film is etched by using the resist pattern remaining on the Cr film as a mask.

After that, the phase shift pattern 3 is inspected for defects, and if there is any defect, the defect is corrected by a conventional method.

Alignment marks M ₁ and M ₂ for aligning the light shielding patterns 2a to 2c and the phase shift pattern 3 are formed in the remaining areas of the working reticle P ₁ and the master reticle P ₂ , respectively. ..

The alignment mark M ₁ of the working reticle P ₁ is composed of a Cr film formed in the same step as the light-shielding patterns 2a to 2c.
₂ of the alignment mark M _2, the phase shift pattern 3
It is composed of a Cr film formed in the same process as.

The alignment mark M ₁ and the alignment mark M ₂ are, for example, one line segment and the other two line segments arranged in parallel on both sides of this line segment. There is.

Therefore, when the working reticle P ₁ and the master reticle P ₂ are superposed on each other, the alignment mark M ₂ (or M ₁ ) is located in the middle of the two line segments constituting the alignment mark M ₁ (or M ₂ ). When one line segment that constitutes the position is positioned, it can be determined that the light shielding patterns 2a to 2c and the phase shift pattern 3 are accurately aligned.

In order to transfer the phase shift pattern 3 of the master reticle P ₂ onto the predetermined area of the working reticle P ₁ , first, as shown in FIG.
The transparent film 4 made of, for example, spin-on glass is spin-coated on the main surface of the working reticle P ₁ on which 2c is formed.

The film thickness (d) of the transparent film 4 is set so that the refractive index is n and the wavelength of the exposure light is λ, and d = λ / 2 (n-1) or an odd multiple thereof.

For example, the wavelength of the exposure light is 365 nm (i
Line), if the refractive index of spin-on-glass is 1.5,
The film thickness of the transparent film 4 is set to about 365 nm.

Next, as shown in FIG. 4, a positive photoresist film 5 is spin-coated on the main surface of the working reticle P ₁ having the transparent film 4 deposited thereon. In order to secure the adhesion between the photoresist film 5 and the transparent film 4, the photoresist film 5 has a film thickness of about 1 to 2 μm.

Next, as shown in FIG. 5, the working reticle P ₁ and the master reticle P ₂ are set at predetermined positions of an optical exposure device (not shown). Then, the detected images of the alignment marks M ₁ and M ₂ are simultaneously captured, the detected images are directly compared, and the relative positions are aligned, so-called on-axis alignment method is used to align the two.

Subsequently, exposure light such as i-line is irradiated from above the master reticle P ₂ to form a latent image of the phase shift pattern 3 on the photoresist film 5 on the working reticle P ₁ , and then, as shown in FIG. As described above, the exposed portion of the photoresist film 5 is removed with a developing solution to form a resist pattern 5 a on the transparent film 4.

Then, by etching the transparent film 4 using the resist pattern 5a as a mask, as shown in FIG. 7, the phase shifter 4a made of the transparent film 4 is formed in a predetermined region on the main surface of the working reticle P _1. The formed phase shift photomask is completed.

According to this embodiment having the above structure, the following effects can be obtained.

(1) Since the phase shift pattern 3 composed of the Cr film on the master reticle P ₂ is transferred onto the working reticle P ₁ by using the light exposure technique, the transparent film 4 is prevented from being charged during the exposure. be able to.

As a result, it is possible to prevent a decrease in pattern transfer accuracy, so that the reliability and manufacturing yield of the phase shift photomask are improved.

(2) The phase shift pattern 3 on the master reticle P ₂ is processed by the optical exposure technique to make the working reticle P
_Since it is transferred onto ₁ , the thickness of the photoresist film 5 is
The photoresist film 5 can be made as thick as about 2 μm.
It is possible to secure the adhesiveness between the transparent film 4 and the transparent film 4.

As a result, local peeling of the photoresist film 5 can be prevented, so that the occurrence of defects in the phase shift photomask is reduced and the manufacturing yield thereof is improved.

(3) The phase shift pattern 3 on the master reticle P ₂ is processed by using the optical exposure technique to make the working reticle P 2.
_{Since the image} is transferred onto the substrate ₁ , it is possible to avoid generation of dust due to pressure fluctuations when the master reticle P ₂ and the working reticle P ₁ are taken in and out of the exposure apparatus.

As a result, the amount of foreign matter attached to the master reticle P ₂ and the working reticle P ₁ is reduced, so that the occurrence of defects in the phase shift photomask is reduced,
The manufacturing yield is improved.

(4) The phase shift pattern 3 on the master reticle P ₂ is processed by the optical exposure technique to make the working reticle P
_Since it is transferred onto _{1 at} a time, when manufacturing multiple photomasks for phase shift of the same pattern, when correcting only the light-shielding pattern unrelated to the phase shift pattern, there is an uncorrectable defect in the phase shift pattern. Therefore, in any case, such as when the phase shifter is peeled off and the transparent film is coated again, the time required to form the phase shift pattern can be significantly reduced.

(5) Since the phase shift pattern 3 on the master reticle P ₂ is made of the same Cr film as the light shielding patterns 2a to 2c, the defect correction of the phase shift pattern 3 is performed by using the ordinary defect correction technique of the photomask. It becomes possible to do.

As a result, the correction rate of the defects generated in the phase shift pattern is improved, so that the reliability and manufacturing yield of the phase shift photomask are improved.

Further, since the time required to correct the defects generated in the phase shift pattern can be shortened, the time required to manufacture the phase shift photomask can be shortened.

Although the invention made by the present inventor has been concretely described above 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 embodiment, the working reticle P ₁
Light shielding patterns 2a to 2c and master reticle P ₂
Although the case where the phase shift pattern 3 is formed by using the positive type electron beam resist has been described, it may be formed by using the negative type electron beam resist.

In this case, since the light-shielding area and the light-transmitting area are reversed, the working reticle P ₁ has the light-transmitting areas 6a to 6c as shown in FIG. 8 and the light-transmitting area. Alignment mark M
₁ is formed.

On the master reticle P ₂ , a phase shift pattern 3 composed of a light transmitting area as shown in FIG. 9 is formed. However, since the alignment mark is required to be able to detect the alignment mark on the working reticle passes through the master reticle, a peripheral alignment marks as a light transmissive region, the alignment mark M ₂ where the mark itself and the light shielding region It is formed.

In the above-described embodiment, the case where spin-on glass is used as the material of the phase shifter has been described, but a silicon oxide film deposited by using the CVD method, for example, can be used.

[0072]

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

(1) According to the present invention, charging of the transparent film at the time of exposure can be avoided, so that the reliability and manufacturing yield of the phase shift photomask can be improved.

(2) According to the present invention, the adhesiveness between the transparent film and the photoresist spin-coated thereon can be ensured, so that the manufacturing yield of the phase shift photomask can be improved.

(3) According to the present invention, since the amount of foreign matter attached to the phase shift photomask can be reduced, the manufacturing yield of the phase shift photomask can be improved.

(4) According to the present invention, since the phase shift pattern is transferred using the light exposure technique, when a plurality of phase shift photomasks having the same pattern are manufactured,
The manufacturing time can be significantly reduced.

(5) According to the present invention, since the correction rate of the defects generated in the phase shift pattern is improved, the reliability and the manufacturing yield of the phase shift photomask are improved.

(6) According to the present invention, it is possible to shorten the time required to correct a defect generated in the phase shift pattern, and thus it is possible to shorten the manufacturing time of the phase shift pattern.

[Brief description of drawings]

FIG. 1 shows a first photomask used in an embodiment of the present invention, in which FIG. 1 (a) is a plan view of relevant parts, and FIG. 1 (b) is the same drawing.
It is sectional drawing in the IA-IA line | wire of (a).

2A and 2B show a second photomask used in one embodiment of the present invention. FIG. 2A is a plan view of a main part thereof, and FIG.
It is sectional drawing in the IIB-IIB line of (a).

FIG. 3 is a fragmentary cross-sectional view of a first photomask showing a method for manufacturing a phase shift photomask.

FIG. 4 is a fragmentary cross-sectional view of a first photomask showing a method for manufacturing a phase shift photomask.

FIG. 5 is a cross-sectional view of essential parts of a first photomask and a second photomask, showing a method of manufacturing a phase shift photomask.

FIG. 6 is a fragmentary cross-sectional view of a first photomask showing a method for manufacturing a phase shift photomask.

7A and 7B show a photomask for phase shift, FIG. 7A is a plan view of a main part thereof, and FIG. 7B is a VIIA-VIIA view of FIG. 7A.
It is sectional drawing in a line.

8A and 8B show a first photomask used in another embodiment of the present invention, in which FIG. 8A is a plan view of relevant parts, and FIG.
It is sectional drawing in the VIIIA-VIIIA line of (a).

9A and 9B show a second photomask used in another embodiment of the present invention, in which FIG. 9A is a plan view of relevant parts, and FIG.
It is sectional drawing in the IXB-IXB line of (a).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass substrate 2a-2c Light-shielding pattern 3 Phase shift pattern 4 Transparent film 4a Phase shifter 5 Photoresist film 5a Resist pattern 6a-6c Light transmission area P ₁ First photomask (working reticle) P ₂ Second photomask ( Master reticle) M ₁ alignment mark M ₂ alignment mark

Front page continuation (72) Inventor Shinji Kuniyoshi 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Inside Musashi Plant, Hitachi Ltd. (72) Masamichi Kobayashi 5-20 Kamimizuhoncho, Kodaira-shi, Tokyo Hitachi Ltd. Musashi factory, No. 1 stock company

Claims (4)

[Claims] 1. A phase shifter made of a transparent film is provided on one of a pair of light transmission regions formed on a glass substrate, and the phases of two lights transmitted through the pair of light transmission regions are opposite to each other. A method of manufacturing a shift photomask, comprising:
An electron beam resist is spin-coated on a first glass substrate having a light-shielding film deposited on the entire surface, and a latent image having a predetermined pattern is formed on the electron beam resist using an electron beam drawing apparatus, and then the electron beam resist is formed. To develop the first photomask by etching the light-shielding film using the resist pattern remaining on the light-shielding film as a mask, and forming an electron on the second glass substrate having the light-shielding film deposited on the entire surface. A line resist is spin-coated, a latent image of a phase shift pattern is formed on the electron beam resist using an electron beam drawing apparatus, the electron beam resist is developed, and the resist pattern remaining on the light shielding film is used as a mask. A step of etching the light-shielding film to manufacture a second photomask, a transparent film serving as a phase shifter material is deposited on the entire surface of the first photomask, and then a photomask is formed on the transparent film. After spin-coating a resist and forming a latent image of the phase shift pattern formed on the second photomask on the photoresist using a photo-exposure device, the photoresist is developed and left on the transparent film. A method of manufacturing a photomask, comprising the step of etching the transparent film using the resist pattern as a mask to form a phase shifter. 2. The method of manufacturing a photomask according to claim 1, wherein the transparent film is made of spin-on glass. 3. The method of manufacturing a photomask according to claim 1, wherein alignment marks for alignment with each other are formed in the respective remaining areas of the first and second photomasks. 4. After manufacturing the second photomask,
2. The method of manufacturing a photomask according to claim 1, wherein the quality of the phase shift pattern is inspected, and the defect is corrected if necessary.