JP2007171651A - Method for correcting defect in photomask having gradation, and photomask having gradation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for correcting defects in a semitransparent film of a photomask having gradation, by which a minute defect can be corrected by the use of the present photomask defect correcting device and a resist film residual amount on a substrate where a pattern is to be transferred can be controlled, and to provide a photomask having gradation. <P>SOLUTION: The photomask having gradation has a desired pattern on a transparent substrate, with the patterned film comprising a light-shielding film which does not transmit exposure light and a semitransparent film which transmits exposure light at the desired transmittance, and the photomask includes a mixture of a light-shielding region where at least the light-shielding film exists, a semitransparent region where the semitransparent film exists, and a transmission region where neither the light-shielding film nor the semitransparent film exists. The method for correcting defects in the semitransparent region of the photomask is such that a semitransparent film for correction is formed in a defect portion so that the transmitted light quantity in the corrected portion of the semitransparent region, after the defect correction to the transmitted light quantity of the normal semitransparent film region that does not have defects. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention uses a single photomask having gradations instead of performing a plurality of lithography steps using a plurality of photomasks in a photolithography technique used for pattern formation of a semiconductor element, an image display element, or the like. The present invention relates to a defect correcting method for a photomask having gradations and a photomask having corrected gradations, which are used in a manufacturing technique for reducing the number of lithography processes by forming a resist profile having a step according to the amount of transmitted light.

Regarding pattern formation methods that reduce the number of lithography processes such as image display elements such as semiconductor elements and liquid crystal display devices (LCDs), for example, a method that reduces the number of lithography times by the reflow method or a number of lithography times by the ashing method (For example, refer to Patent Document 1 and Patent Document 2).
In addition, the above-mentioned patent document discloses a photomask having a light-shielding pattern (hereinafter referred to as a slit mask) having a minute slit below the resolution limit of an exposure apparatus used for this purpose, and a transmitted light amount with respect to exposure light. A photomask having a gradation in which is changed (hereinafter also referred to as a gradation mask or a graytone mask) is described. Since the slit of the slit mask has a size less than the resolution limit, the slit mask itself does not form an image on the resist, but transmits the exposure light corresponding to the size to the area including the surrounding non-opening region. For this reason, the slit mask is a mask that functions as if there is a translucent film in the area where the slit is formed and the area including the periphery thereof.

  In photolithography, if a defect exists on the photomask, the defect is transferred onto the transfer substrate and causes a reduction in yield. Therefore, before transferring the mask pattern onto the transfer substrate, the defect inspection apparatus uses the photomask. The presence or absence of a defect and the location of the defect are checked. If a defect exists, a defect correction process is performed by a defect correction device, and the defect is supplied as a photomask free of defects that affect transfer. Defect correction is an important technique when using a large mask such as a photomask for LCD. On the other hand, with the miniaturization of the pattern dimension, the size of the defective portion of the photomask that needs to be corrected has become smaller and the accuracy in correction has also become smaller.

There are two types of defects in a photomask: when an originally required pattern is missing or missing (referred to as a white defect) and when an unnecessary surplus pattern exists (referred to as a black defect). . In the case of a black defect, a normal pattern can be obtained by removing the surplus portion. As a correction method, a correction method using a laser beam and a correction method using a focused ion beam (hereinafter also referred to as FIB) are currently available. Are the mainstream methods, both of which are methods of directly removing and correcting the defect film.
As a method for correcting white defects, generally, a method in which an opaque film is formed and deposited on a defective portion by using a laser CVD technique or a gas assist FIB film forming technique is widely used.

  In the correction of the defect portion of the slit mask or the gradation mask described above, if there is a defect portion in the light shielding portion, the defect portion can be corrected using a conventional photomask defect correction technique. However, since the correction method used for the defect portion of the conventional photomask light-shielding portion cannot be directly applied to the correction of the slit portion or the defect portion of the translucent film, another defect correction method has been proposed.

  For example, as a method for correcting a defective portion of a slit portion of a slit mask, a defect that does not restore the defective portion to the same shape as the corrected portion but forms a correction pattern that can obtain a gray tone effect equivalent to a normal pattern A correction method is known (see Patent Document 3). FIG. 6 is a partial plan view for explaining a black defect correcting method for the slit portion of the slit mask. FIG. 6A shows a case where the black defect 65 is generated in the slit portion 63, as shown in FIG. In this method, a defect pattern is partially removed and a correction pattern is formed so that a gray tone effect equivalent to that of a normal pattern can be obtained. FIG. 7 is a partial plan view for explaining a method for correcting white defects in the slit portion of the slit mask. FIG. 7 (1) shows a case where a white defect occurs in the slit portion, as shown in FIG. 7 (2). This is a method in which a correction film is spot-formed on a defective portion so that a gray tone effect equivalent to a normal pattern can be obtained.

As a method for correcting a photomask having a translucent film, for example, a halftone phase shift mask capable of recovering transfer characteristics within a correction capability range of an existing correction device in correcting a concave defect portion of a halftone phase shift mask. Is disclosed (see Patent Document 4).
Japanese Patent No. 3415602 JP 2000-66240 A Japanese Patent No. 3556591 Japanese Patent No. 3465091

In photolithography using a slit mask or gradation mask, even a very small defect in a semi-transparent film that semi-transmits exposure light affects the formation of a resist image on the transferred substrate. There was a need.
However, while the correction method described in Patent Document 3 requires a correction technique below the transfer resolution limit of the exposure machine, the minimum width that can be corrected by the current photomask defect correction apparatus is about 2 μm. In addition, there is a problem that it is not sufficiently small with respect to the transfer resolution limit of the exposure machine, so that it is particularly difficult to correct a minute defect.

  On the other hand, as shown in Patent Document 4, a correction technique while considering the transfer performance in consideration of the performance of the correction device is common in correcting a halftone phase shift mask. However, there is a problem that the amount of residual resist film on the transferred substrate corresponding to the semi-transparent region cannot be controlled even if the size can be controlled.

  The present invention has been made in view of the above problems. That is, in a method for correcting a defect in a semi-transparent film of a photomask having a gradation for reducing the number of photolithography processes used for manufacturing an LCD or the like, a minute defect is corrected using a current photomask defect correcting apparatus. A method for correcting a defect in a semi-transparent region of a photomask having a gradation capable of controlling the amount of residual resist film on a transferred substrate that has passed through the semi-transparent region and a photomask having a corrected gradation are provided. To do.

  In order to solve the above problems, a defect correcting method for a semi-transparent region of a photomask having a gradation according to the invention of claim 1 has a desired pattern on a transparent substrate, and a film for forming the pattern is provided on the transparent substrate. A light-shielding film that substantially does not transmit exposure light, and a semi-transparent film that transmits the exposure light at a desired transmittance. A light-shielding region in which at least the light-shielding film exists on the transparent substrate, the semi-transparent In a method for correcting a defect in a semi-transparent region of a photomask having a gradation in which a semi-transparent region where a film is present and a transmissive region where neither the light-shielding film nor the semi-transparent film is present are mixed, A translucent film for correction is formed on the defect portion so that the transmitted light amount of the corrected portion after the defect portion correction is equal to the transmitted light amount of a normal semi-transparent region having no defect. is there.

According to a second aspect of the present invention, there is provided a defect correcting method for a semi-transparent region of a photomask having a gradation, wherein the defect portion is white. When the area (X ₁ ) of the defect portion is smaller than the minimum area that can be corrected by the correction device that corrects the correction portion, the energy transmittance of the normal translucent region is expressed as I _H %. When the energy transmittance of the defect portion is 100%, the film-forming area of the semitransparent film for correction is Y, and the energy transmittance is I _C %, the I _C satisfies the following relational expression (1). It is characterized by.
_{Y = X 1 × (I C} -I H I C) / (I H -I H I C) (1)

  A defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 3 is the defect correcting method for a semi-transparent region of a photomask having gradation according to claim 2, The film-forming area Y of the transparent film is equal to the minimum area that can be corrected by the correction device.

According to a fourth aspect of the present invention, there is provided a defect correcting method for a semi-transparent region of a photomask having a gradation, wherein the defect portion is white. A semi-transparent film for correcting the correction portion is covered when the defect portion has an area (X ₂ ) slightly larger than the minimum area that can be corrected by the correction device that corrects the correction portion. The area of the non-defective portion is A, the area of the portion where the semi-transparent film for correction overlaps the semi-transparent region is B, the energy transmittance of the semi-transparent region is I _H %, and the energy transmittance of the defect portion Is 100%, and energy transmissivity of the correcting translucent film is I _C %, the A, B and I _C satisfy the following relational expression (2).
X ₂ = {(1−I _C ) A + (I _H I _C −I _C −I _H ) B} / (I _H −I _C ) (2)

  A defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 5 is the defect correcting method for a semi-transparent region of a photomask having gradation according to claim 4, The film formation area of the transparent film is equal to the minimum area that can be corrected by the correction device.

  A defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 6 is the defect correcting method for a semi-transparent region of a photomask having gradation according to claim 1, wherein the defect portion is white. In the case where the area of the defect portion is much larger than the minimum area that can be corrected by the correction device that corrects the correction portion, the same energy as that of the translucent film is inscribed in the defect portion. A translucent film for correcting the transmittance is formed.

  A defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 7 is the defect correcting method for a semi-transparent region of a photomask having gradation according to claim 6, The correction method according to any one of claims 2 to 5 is further applied to a gap portion between the transparent film and the defect portion.

  A defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 8 is the defect correcting method for a semi-transparent region of a photomask having gradation according to claim 1, wherein the defect portion is white. 8. The defect part according to claim 2, which is a defect part, and after the semitransparent film around the white defect part is removed by laser light or a focused ion beam to shape the white defect part, The defect portion is corrected by a method.

  A defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 9 is the defect correcting method for a semi-transparent region of a photomask having gradation according to claim 1, wherein the defect portion is black. The method according to any one of claims 2 to 7, which is a defect portion, and the black defect portion is removed by a laser beam or a focused ion beam so that the energy transmittance of the defect portion is set to 100%. Thus, the defect portion is corrected.

  The defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 10 is a defect in a semi-transparent region of a photomask having gradation according to any one of claims 1 to 9. In the correction method, both of the light shielding film and the semitransparent film are mainly composed of chromium.

  A defect correcting method for a semi-transparent region of a photomask having gradation according to the invention of claim 11 is the defect correcting method for a semi-transparent region of a photomask having gradation according to claim 10, wherein the light shielding film is chromium. Alternatively, it is made of chromium nitride, and the translucent film is made of chromium oxide or chromium oxynitride.

  A photomask having a gradation according to the invention of claim 12 has a desired pattern on a transparent substrate, and the film forming the pattern includes a light-shielding film that does not substantially transmit exposure light, and the exposure light. A semi-transparent film that transmits at a desired transmittance, and on the transparent substrate, a light-shielding region where at least the light-shielding film exists, a semi-transparent region where the semi-transparent film exists, and the light-shielding film and the semi-transparent film A non-existing transmissive region, and a photomask having a gradation, the photomask having the gradation has a translucent region in which a defect portion is corrected, and the defect-corrected translucent region The translucent film for correction is formed in the defective part so that the transmitted light quantity of the corrected part after the defect part correction becomes equal to the transmitted light quantity of a normal semi-transparent region having no defect. To do.

The defect correction method for a semi-transparent region of a photomask having gradation according to the present invention can be corrected conventionally by controlling the transmissivity of a semi-transparent film formed for correction using a current photomask defect correction apparatus. Gradation that makes it possible to correct even small defects that are less than or near the minimum size that can be processed by a correction device, and that can accurately control the amount of residual resist on the transferred substrate. A photomask having
The defect correcting method for the semi-transparent region of the photomask with gradation of the present invention uses a conventional chrome-based material photomask blank, and corrects the defect using existing mask manufacturing equipment, inspection equipment, and correction equipment. A photomask having different gradations can be obtained. Therefore, according to the present invention, a photomask having high quality gradation can be obtained at low cost.
By using the defect correcting method for a semi-transparent region of a photomask having gradation according to the present invention, the number of photolithography steps of a semiconductor element or an image display element can be efficiently reduced, and a low-cost semiconductor element or image display can be achieved. An element can be realized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a defect correcting method for a translucent region of a photomask having gradation and a photomask having gradation will be described below with reference to the drawings.
1 to 5 are schematic plan views showing an embodiment of a defect correcting method for a photomask having gradation according to the present invention. 6 and 7 are schematic views showing examples of a photomask having a gradation having a defective portion before the correction method of the present invention is performed.

(Photomask with a gradation having a defective part)
A photomask having a gradation to which the correction method of the present invention is applied has a desired pattern on a transparent substrate, and the film forming the pattern substantially does not transmit exposure light, and exposure light. A semi-transparent film that transmits at a desired transmittance, and the light-shielding region where at least the light-shielding film is present, the semi-transparent region where the semi-transparent film is present, and both the light-shielding film and the semi-transparent film This is a photomask having a gradation in which a non-existing transmission region is mixed.

  FIG. 6 shows an example of a photomask having a gradation having a white defect portion before performing the correction method of the present invention, and FIG. 6A is a schematic plan view of the defect portion of the photomask. 6 (b) is a schematic cross-sectional view taken along line CC of FIG. 6 (a). As shown in FIG. 6A, a light shielding region 62a in which a light shielding film 62 and a semitransparent film 63 are laminated in this order on a transparent substrate 61, a semitransparent region 63b in which a semitransparent film 63 is present, and When the light-shielding film 62 and the transmissive region where neither the semi-transparent film 63 exists are mixed, and the white defect portion 64 exists in the semi-transparent region 63b where the semi-transparent film 63 exists. Indicates.

  FIG. 7 shows another example of a photomask having a gradation having a white defect portion before performing the correction method of the present invention. The schematic plan view of the defective portion of the photomask is the same as that of FIG. 6A, but illustrates a photomask having a different cross-sectional shape. The light-shielding film 72 is formed by stacking the light-shielding film 72 on the semitransparent film 73. The region 72a, the semi-transparent region 73b where the semi-transparent film 73 exists, and the light-transmitting region where neither the light-shielding film 72 nor the semi-transparent film 73 exists are mixed, and the semi-transparent film 73 exists. The case where the white defect part 64 exists in the translucent area | region 73b to perform is shown.

  The photomasks illustrated in FIGS. 6 and 7 each have a light shielding region composed of a light shielding film and a semi-transparent film. However, as the photomask used in the present invention, a part of the light shielding region is formed only by the light shielding film. May be. In the case of the photomask shown in FIG. 7, when the light shielding film 72 is formed by pattern etching, the light shielding film is used to prevent the semitransparent film in the lower semitransparent region from being damaged by overetching. An intermediate layer that is transparent to exposure light such as silicon oxide may be provided between 72 and the translucent film 73. As described above, a photomask having a gradation for performing the correction method of the present invention uses a portion where at least a light-shielding film is present as a light-shielding region, and a region where only a semi-transparent film exists, or is transparent to a semi-transparent film and exposure light. The region where the intermediate layer exists is a translucent region.

  In the present invention, the light-shielding film pattern that does not substantially transmit exposure light means a light-shielding film pattern that transmits exposure light by one exposure and does not expose the photosensitive resist at the exposure wavelength. In the exposure wavelength, a transmittance of 0.1% or less is desirable.

Hereinafter, description will be made with reference to FIG. 6, but the present invention can also be applied to the case of FIG.
As shown in FIG. 6, as the transparent substrate 61 of the photomask to which the photomask correcting method of the present invention is applied, usually optically polished soda lime glass and borosilicate glass used for the photomask are used. Or low expansion glass such as aluminoborosilicate glass, synthetic quartz glass, fluorite, calcium fluoride, etc. can be used, and synthetic quartz glass is preferred when the exposure light has a short wavelength.

  In the present invention, the light shielding film 62 may be any thin film that can be used as a normal mask material, such as a chromium-based film, molybdenum silicide, tantalum, aluminum, silicon, silicon oxide, and silicon oxynitride. However, a chromium-based film composed mainly of chromium, which has been used most frequently, is more preferable in terms of cost and quality of the mask blank. As the chromium-based film, a single layer film made of a material selected from chromium, chromium oxide, chromium nitride, and chromium oxynitride is usually used. Among these chromium-based films, film formation is easy and versatile. A chromium film or a chromium nitride film that can easily reduce film stress is more preferable. For example, when chromium is used as the light shielding film, the film thickness is in the range of about 50 nm to 150 nm.

  In the present invention, the translucent film 63 is not particularly limited as long as it has translucency to transmit exposure light with a desired transmittance. For example, an oxide film, a nitride film, A carbide film or a silicide film can be used. Specific examples include a chromium oxide film, a chromium oxynitride film, a tantalum oxide film, a tantalum nitride film, and a tantalum silicide film. The translucency of the translucent film 63 can be controlled by adjusting the film thickness.

  Further, in order to maintain the advantage that the translucent film 63 and the light shielding film 62 can be patterned by the same etching equipment and process, the translucent film 63 is preferably made of the same material as the light shielding film 62. When a chromium-based material is used as the preferred material for the light-shielding film 62 as described above, the translucent film 63 is a film having a relatively high transmittance and containing chromium, oxygen, nitrogen, carbon, and the like. The film composition and film thickness can be optimized so as to reduce the reflectivity when stacked on the film. Among the chromium-based semi-transparent films, a chromium oxide film or a chromium oxynitride film that can relatively easily control the characteristics of both the transmittance and the antireflection function is more preferable. For example, when a chromium oxide film is used as a translucent film, the film thickness is in the range of about 5 nm to 150 nm. This is because if the film thickness is less than 5 nm or exceeds 150 nm, a difference in transmittance as a translucent film with respect to the light-shielding film is hardly generated. In the case of a translucent film containing oxygen, nitrogen, carbon, etc., the absorbance varies depending on the composition, so that the desired transmittance and antireflection function can be realized by simultaneously controlling the film thickness and composition.

  In the present invention, it is preferable that the translucent film 63 forming the translucent film region 63b has a transmittance of 15% to 85% with respect to the exposure light. In the translucent region 63b where the translucent film 63 exists, if the transmittance is less than 15%, it is difficult to make a difference from the light shielding region 62a in the resist pattern formation using the photomask having the gradation of the present invention. This is because when the ratio exceeds 85%, it becomes difficult to make a difference from the transmission region in forming the resist pattern.

(Defect correction method for photomask with gradation)
As described above, a conventional defect correction method can be used to correct a defective portion in a light shielding region of a photomask having gradation. Hereinafter, embodiments of a method for correcting a defect portion in a semi-transparent region of a photomask having gradation according to the present invention will be described separately for a case where a defect portion is a white defect and a case of a black defect.

(How to correct white defects in translucent areas)
The method for correcting a white defect in a semi-transparent region of the present invention is to form a semi-transparent film such as chromium on the defective portion using a laser CVD technique, or a semi-transparent film such as carbon using a gas assist FIB film forming technique. Forming and correcting the transparent film itself is the same as that of the prior art such as the halftone phase shift mask, but the prior art can correct only by optimizing the size and position of the film for correction. On the other hand, in the present invention, the transmittance of the translucent film formed for correction is also controlled. For example, in the case of correction using the laser CVD technique, by controlling the following three parameters, it is possible to correct a semi-transparent film even for minute defects in a semi-transparent region of a photomask having gradation. To do.
1. Film forming position of the correction semitransparent film: Usually, the film can be formed with an accuracy of about +/− 100 nm.
2. Film-forming area of the semi-transparent film for correction: Usually, the film can be formed in an area of a minimum of about 2 μm □.
3. The transmissivity of the correcting translucent film is usually controllable at about +/- 2%.
According to the correction method of the present invention, it is possible to correct a defect having a size smaller than or equal to the minimum size that can be processed by the correction device, or a size near the minimum size.
Next, embodiments of the present invention will be described in more detail by dividing them according to the size of the white defect portion.

(First embodiment)
The first embodiment is a case where the size of the white defect portion is smaller than the minimum area where the correction film can be formed by the correction device, and is usually the case where the size of the white defect portion is about 1 to 2 μm.
FIG. 1 is a partial schematic plan view for explaining the first embodiment. FIG. 1A is a schematic plan view before correction, and a white defect portion 12 having a size of 1 to 2 μm is formed in a semi-transparent region 11. Exists. FIG. 1B is a schematic plan view after correction by the defect correction method of the present invention. A laser-transparent film 13 made of chrome or the like is formed over the above-described white defect portion to form white defects. A photomask having a gradation in which the portion is corrected and the defective portion is corrected is obtained.

  In the white defect correction method according to the first embodiment, the transmitted light amount before and after the correction is made equal, and the transmitted light amount at the corrected position after the correction becomes the transmitted light amount in a normal translucent area without a defect. The energy transmittance of the corrected portion is determined so as to be equal. In this case, since the size of the defect portion is smaller than the minimum area where the correction film can be formed by the correction device, the film formation area of the correction translucent film is from the viewpoint of forming a better resist image on the transfer substrate during transfer. More preferably it is fixed to the smallest possible area of the correction device.

Therefore, the area of the white defect portion 12 is X ₁ , the area of the correction translucent film 13 is Y, the energy transmissivity of the normal translucent region 11 having no defect is I _H %, and the energy transmissivity of the defect portion 12. Is 100% and the energy transmissivity of the translucent film 13 for correction is I _C %.
(Y−X ₁ ) × I _H I _C + X ₁ × I _C = Y × I _H
Therefore,
_{Y = X 1 × (I C} -I H I C) / (I H -I H I C) (1)
In the present embodiment, the energy transmittance I _C of the correction translucent film 13 satisfies the above relational expression (1). Further, as described above, it is more preferable to fix Y to the minimum possible area of the correction device. Specifically, the energy transmittance I _C % satisfying the relational expression (1) can be obtained by controlling the film thickness of a semitransparent film such as chromium formed for correction.

(Second Embodiment)
The second embodiment is a case where the size of the white defect portion is slightly larger than the minimum area where the correction film can be formed by the correction device, and is usually the case where the size of the white defect portion is about 2 to 3 μm. .
FIG. 2 is a schematic partial plan view for explaining the second embodiment. FIG. 2A is a schematic plan view before correction, and a white defect portion 22 having a size of 2 to 3 μm is formed in the translucent region 21. Exists. FIG. 2B is a schematic plan view after correction by the defect correction method of the present invention, and a semi-transparent film 23 such as chromium is formed on most of the white defect portion 22 by using a laser CVD technique. A white defect portion is corrected, and a photomask having a gradation in which the defect portion is corrected is obtained.

  In the white defect correction method of the second embodiment, if the film-forming area of the translucent film at the correction location is increased, the resist image on the transferred substrate becomes non-uniform at the time of transfer, so the film-forming area itself is kept to a minimum. It is preferable that the correction device has a minimum area that can be corrected, so that the amount of transmitted light before and after correction becomes equal. That is, the energy transmittance of the corrected portion is determined so that the transmitted light amount of the corrected portion after correction becomes equal to the transmitted light amount of a normal translucent area having no defect.

Therefore, the area of the white defect portion 22 is X ₂ , the area of the defect portion 22 that is not covered by the correction semitransparent film 23 at the correction portion is A, and the correction semitransparent film 23 is overlapped with the lower semitransparent region 21 Where B is the energy transmissivity of a normal translucent region having no defects, I _H %, the energy transmissivity of the defect part is 100%, and the energy transmissivity of the translucent film for correction is I _C %.
_{A × 100 + B × I H} I C + (X 2 -A-B) × I C = (X 2 + B) × I H
Therefore,
X ₂ = {(1−I _C ) A + (I _H I _C −I _C −I _H ) B} / (I _H −I _C ) (2)
In the present embodiment, it is preferable that A, B, and I _C satisfy the relational expression (2). Specifically, the areas A and B and the energy transmittance I _C % of the corrected portion are determined so that the above relational expression (2) is established. I _C % can be controlled by the film thickness of a semitransparent film such as chromium to be formed as in the first embodiment.
Also in this embodiment, as in the first embodiment, when the film-forming area of the correction semi-transparent film is increased, the resist image on the transferred substrate at the time of transfer becomes non-uniform, so the film-forming area is minimized. Preferably, the film-forming area of the correcting translucent film is preferably fixed to the smallest possible area of the correcting device.

  At this time, the defect image is obtained as an image of an optical microscope image, a scanning electron microscope image, an ion image, etc., and, for example, an optical simulation such as Prolith made by KLA Tencor is used to transfer a translucent region equivalent to a normal portion. It is desirable to select the optimum film forming position, transmittance, etc. of the correcting translucent film so that the characteristics can be obtained. It is also possible to acquire a corrected image and guarantee transfer performance by optical simulation.

(Third embodiment)
In the third embodiment, the area (X ₃ ) of the white defect portion is much larger than the minimum area where the correction film can be formed by the correction apparatus.
FIG. 3 is a partial schematic plan view for explaining the third embodiment. FIG. 3A is a schematic plan view before correction. In the translucent region 31, for example, a white defect portion 32 having a size exceeding 3 μm. Exists. FIG. 3B is a schematic plan view after the correction by the defect correction method of the present invention, and a semitransparent film 33 such as chromium is formed in contact with the white defect portion 32 by using a laser CVD technique. A white defect portion is corrected, and a photomask having a gradation in which the defect portion is corrected is obtained.

In the white defect correction method of the third embodiment, since the size of the white defect portion 32 is very large, as shown in FIG. 3B, a correction translucent film 33 is formed in the defect area. be able to. In this case, the correcting translucent film 33 is formed in a rectangular shape inscribed in the defect portion 32 with the same transmittance as that of the normal portion with a large possible area. A plurality of rectangular correction semi-transparent films 33 can be formed by changing the rectangular dimension according to the defect shape. As described above, the transmitted light amount before and after correction is made equal.
Furthermore, if necessary, the correction method of the first embodiment or the second embodiment is applied to the gap between the formed semi-transparent film 33 for correction and the outer periphery of the defect 32. It is also possible to apply.

(Fourth embodiment)
The fourth embodiment is a method suitable for a case where the white defect portion is indefinite and has a complicated shape, and is a method of forming a correction semitransparent film after shaping the white defect portion.
FIG. 4 is a schematic partial plan view for explaining the fourth embodiment. FIG. 4A is a schematic plan view before correction, and a white defect portion 42 having a complex indefinite shape is formed in a semi-transparent region 41. Exists. FIG. 4B is a schematic plan view in the middle of correction by the defect correction method of the present invention. The semitransparent film 41 around the white defect portion 42 is removed by a laser beam or a focused ion beam, and the white defect portion is shaped. After forming the shaped white defect portion 43, next, as shown in FIG. 4C, a laser CVD technique is used to form a white defect portion 43 that covers the shaped white defect portion 43, such as a semitransparent film 44 such as chromium. The defective portion is corrected, and a photomask having a gradation in which the defective portion is corrected is obtained.

In the fourth embodiment, the shaping shape of the white defect portion can be changed depending on the shape of the defect portion, but a rectangular shape is more preferable because it is easy to correct.
For correcting the shaped white defect portion 43, any one of the methods of the first to third embodiments can be applied depending on the size of the white defect portion. In the example shown in FIG. 4C, the method of the first embodiment is applied, and the appropriate transmittance of the correction translucent film is obtained using the relational expression (1).

(How to correct black defects in translucent areas)
Next, a case where the defective portion is a black defect will be described. FIG. 5 is a partial plan view schematically illustrating the black defect correcting method of the present invention. FIG. 5A is a schematic plan view before correction, and a black defect portion 52 exists in the translucent area 51. In the case of a black defect portion, first, the black defect portion 52 is removed by a laser beam or a gas assist focused ion beam, and as shown in FIG. 5B, the defect portion becomes a white defect portion 53, and the energy transmittance thereof is 100%. And
Next, a semitransparent film for correction is formed on the white defect portion 53 by any of the white defect correction methods described in the first to third embodiments, and the defect portion is corrected. A photomask having a tone is obtained. In the example of FIG. 5C, a correction translucent film 54 is formed so as to cover the white defect portion 53.
In the correction method shown in FIG. 5, a method of removing even the semitransparent film in the peripheral portion when removing the black defect portion is shown. In this case, for example, a focused ion beam is used even for a minute defect. Thus, it is possible to correct only the black defect portion by 100% transmission without intentionally expanding the defect area.

Example 1
About 380 nm of commercially available photoresist (ip-3500 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied on a photomask blank in which a light-shielding film made of chromium is formed to about 100 nm on an optically polished 330 × 450 mm synthetic quartz substrate. Then, after baking for 15 minutes on a hot plate heated to 120 degrees, a desired light-shielding film pattern was drawn with a photomask laser drawing apparatus LRS11000-TFT3 manufactured by Micronic. The pattern drawn here is a pattern for finally completely shielding light.
Next, development was performed with a dedicated developer (NMD3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to obtain a resist pattern for a light shielding film.

  Next, the resist pattern was used as an etching mask, the chromium film was etched, and the remaining resist pattern was stripped to obtain a desired light-shielding film pattern. For the etching of the chromium film, a commercially available cerium nitrate wet etchant (MR-ES manufactured by The Inktec Co., Ltd.) was used. The etching time for the chromium film was about 60 seconds.

  Next, the thus-obtained substrate with a light-shielding film pattern was subjected to a light-shielding film pattern dimension inspection, a pattern defect inspection, and a light-shielding film pattern was corrected as necessary, so that there was no light-shielding film defect. Next, this substrate was thoroughly washed, and a chromium oxide film as a translucent film was formed by a sputtering method. The film thickness of the chromium oxide film was about 30 nm, and the transmittance was about 40% (wavelength g line: 436 nm).

Next, a commercially available photoresist (ip-3500 manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied again thereon at about 380 nm, and baked on a hot plate heated to 120 ° C. for 15 minutes.
Subsequently, an image to be a semitransparent film pattern was drawn again with a laser drawing apparatus LNIC11000-TFT3 manufactured by Micronic Co., Ltd. and developed with a dedicated developer (NMD3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to obtain a resist pattern for a translucent film. Note that the drawing apparatus LRS11000 has an alignment drawing function, and forms a translucent film pattern in alignment with the formed light-shielding film pattern.

  Next, using the resist pattern as a mask, the semitransparent film is etched with a commercially available cerium nitrate wet etchant (MR-ES manufactured by The Inktec Co., Ltd.), then the exposed light shielding film is etched, and the remaining resist is removed. A photomask having a gradation in which a light-shielding region, a semi-transparent region, and a light-transmitting region are mixed on a transparent substrate is obtained.

  Next, when the defect inspection of the photomask having this gradation was performed, a minute white defect having a size of 1 μm □ was detected in the semitransparent region of the semitransparent film pattern.

Next, a chromium translucent film was formed and deposited by using a laser CVD technique so as to cover the minute white defect portion. Since the minimum area that can be corrected of the FIB used in this example was 2 μm □, the minimum area that can be corrected for the film formation area of the chromium film for correction was 2 μm □. In the relational expression (1) described in the first embodiment, I _C was calculated by substituting X ₁ = 1, Y = 4, and I _H = 0.4, and I _C = 0.35 was obtained. . Therefore, the film thickness of the chrome film for correction is adjusted, and the translucent film for correction having a transmittance of 35% (wavelength g line: 436 nm) made of a chrome film with a correction size of 2 μm □ of the minimum area that can be corrected. And a photomask having a gradation in which the white defect portion was corrected was obtained.
When the photomask having the corrected gradation was used for the manufacture of the LCD element, it was possible to form patterns with different resist residual film thickness without defects on the transfer substrate.

(Example 2)
A photomask having gradation was manufactured by the same method as in Example 1, and defect inspection was performed. As a result, an irregular black defect having a size of about 1 × 2 μm was detected in the semitransparent region of the semitransparent film pattern.

Next, the black defect portion was removed by a laser beam from a laser correcting device to obtain a white defect portion having a rectangular shape (2 × 2 μm) in which the transmittance of the defect portion was 100%.
Subsequently, a semitransparent chrome film for correction was formed on the white defect portion by using laser CVD having a minimum area of 2 μm □ that can be corrected in the same manner as in Example 1. In the relational expression (1) described in the first embodiment, when I _C was calculated by substituting X ₁ = 2, Y = 4, and I _H = 0.4, I _C = 0.31 was obtained. . Therefore, the film thickness of the chrome film for correction is adjusted, and the translucent for correction with a transmittance of 31% (wavelength g-line: 436 nm) made of a chrome film with a correction size of 2 μm □ of the minimum area that can be corrected. A photomask having a gradation in which a film was formed and the white defect portion was corrected was obtained.
This photomask having the corrected gradation was able to form patterns with different resist residual film thickness without defects on the transfer substrate.

It is a partial plane schematic diagram which shows 1st Embodiment of the white defect correction method of the photomask with a gradation of this invention. It is a partial plane schematic diagram which shows 2nd Embodiment of the white defect correction method of the photomask with a gradation of this invention. FIG. 9 is a partial plan view schematically illustrating a third embodiment of a method for correcting a white defect in a photomask having gradation according to the present invention. It is a partial plane schematic diagram which shows 4th Embodiment of the white defect correction method of the photomask with a gradation of this invention. It is a partial plane schematic diagram which shows one Embodiment of the black defect correction method of the photomask with a gradation of this invention. It is a schematic diagram which shows an example of the photomask which has a gradation which has a defect part before performing the correction method of this invention. It is a cross-sectional schematic diagram which shows another example of the photomask with a gradation which has a defect part before performing the correction method of this invention. It is a fragmentary top view explaining the black defect correction method of the slit part of the conventional slit mask. It is a fragmentary top view explaining the white defect correction method of the slit part of the conventional slit mask.

Explanation of symbols

11, 21, 31, 41, 51 Translucent region 12, 22, 32, 42 White defect portion 13, 23, 33 Correction semi-transparent film 43 Shaped white defect portion 44 Correction semi-transparent film 52 Black defect portion 53 White defect portion 54 Translucent films 61 and 71 for correction Transparent substrates 62 and 72 Light-shielding films 63 and 73 Semi-transparent films 62a and 72a Light-shielding regions 63b and 73b Translucent regions 64 and 74 White defect portions 81 and 91 Light-shielding portion 83 , 93 Slit part 85 Black defect part (bridge)
86 Opening 94 Correction membrane

Claims (12)

A film having a desired pattern on a transparent substrate, the film forming the pattern is composed of a light-shielding film that does not substantially transmit exposure light, and a translucent film that transmits the exposure light at a desired transmittance, A gradation in which a light shielding region where at least the light shielding film is present, a semitransparent region where the semitransparent film is present, and a transmission region where neither the light shielding film nor the semitransparent film is present is mixed on a transparent substrate. In the method of correcting defects in the translucent region of the photomask with
Forming a translucent film for correction on the defective portion so that the transmitted light amount of the corrected portion after correcting the defective portion of the semi-transparent region is equal to the transmitted light amount of a normal semi-transparent region having no defect. A method for correcting a defect in a translucent region of a photomask having a characteristic gradation. When the defect portion is a white defect portion and the area (X ₁ ) of the defect portion is smaller than the minimum area that can be corrected by the correction device that corrects the correction location, the energy transmission of the normal translucent region When the rate is I _H %, the energy transmittance of the defect portion is 100%, the deposition area of the semitransparent film for correction is Y, and the energy transmittance is I _C %, the I _C is expressed by the following relational expression ( The method for correcting a defect in a translucent region of a photomask having gradation according to claim 1, wherein 1) is satisfied.
_{Y = X 1 × (I C} -I H I C) / (I H -I H I C) (1)   3. The method for correcting a defect in a semi-transparent region of a photomask having gradation according to claim 2, wherein the film-forming area Y of the semi-transparent film for correction is equal to the minimum area that can be corrected by the correction device. . When the defect portion is a white defect portion, and the area (X ₂ ) of the defect portion is slightly larger than the minimum area that can be corrected by the correction device that corrects the correction portion, The area of the defect portion that is not covered by the translucent film is A, the area of the portion where the correction translucent film overlaps the translucent area is B, and the energy transmissivity of the normal translucent area is I _H %, When the energy transmittance of the defect portion is 100% and the energy transmittance of the correcting translucent film is I _C %, the A, B, and I _C satisfy the following relational expression (2): The method for correcting a defect in a translucent region of a photomask having gradation according to claim 1.
X ₂ = {(1−I _C ) A + (I _H I _C −I _C −I _H ) B} / (I _H −I _C ) (2)   5. The method for correcting a defect in a semi-transparent region of a photomask having gradation according to claim 4, wherein the film-forming area of the semi-transparent film for correction is equal to a minimum area that can be corrected by the correction device.   In the case where the defect portion is a white defect portion, and the area of the defect portion is much larger than the minimum area that can be corrected by the correction device that corrects the correction portion, the defect portion is inscribed and the translucent 2. The method for correcting a defect in a translucent region of a photomask having gradation according to claim 1, wherein a translucent film for correcting the same energy transmittance as the film is formed.   7. The method for correcting a defect of a photomask having gradation according to claim 6, further comprising a gap between the semitransparent film for correction and the defect, according to any one of claims 2 to 5. A method for correcting a defect in a semi-transparent region of a photomask having gradation, characterized by applying the correction method described in 1.   The defect portion is a white defect portion, and after removing the translucent film around the white defect portion with a laser beam or a focused ion beam to shape the white defect portion, any one of claims 2 to 7 The defect correcting method for a translucent region of a photomask having gradation according to claim 1, wherein the defect portion is corrected by the method according to claim 1.   The defect portion is a black defect portion, and the black defect portion is removed by a laser beam or a focused ion beam so that the energy transmittance of the defect portion is 100%. Next, any one of claims 2 to 7. The defect correcting method for a translucent region of a photomask having gradation according to claim 1, wherein the defect portion is corrected by the method according to claim 1.   10. The translucent region of a photomask having gradation according to claim 1, wherein each of the light-shielding film and the translucent film contains chromium as a main component. Defect correction method.   11. The method for correcting a defect in a semi-transparent region of a photomask having gradation according to claim 10, wherein the light shielding film is made of chromium or chromium nitride, and the semi-transparent film is made of chromium oxide or chromium oxynitride. A film having a desired pattern on a transparent substrate, the film forming the pattern is composed of a light-shielding film that does not substantially transmit exposure light, and a translucent film that transmits the exposure light at a desired transmittance, A gradation in which a light shielding region where at least the light shielding film is present, a semitransparent region where the semitransparent film is present, and a transmission region where neither the light shielding film nor the semitransparent film is present is mixed on a transparent substrate. In the photomask with
The photomask having the gradation has a semi-transparent region in which the defect portion is corrected, and the transmitted light amount of the corrected portion after the defect portion correction in the semi-transparent region in which the defect is corrected is normal semi-transparent without a defect. A photomask having a gradation, wherein a correction translucent film is formed on the defective portion so as to be equal to the amount of transmitted light in the region.

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