TWI699612B - Half tone mask and half tone mask blank - Google Patents

Abstract

Previously, in the multi-gray halftone mask, the pinhole defects formed on the semi-permeable film were detected and corrected by the defect inspection device. Therefore, for example, it is difficult to repair the fine pinhole defects below the detection limit. . In order to solve this problem, the present invention provides the following halftone mask: the semipermeable film of the halftone mask is set such that the phase difference relative to the transparent substrate is 60 to 90 degrees, and the transmittance is 20% to 50%, This prevents the photoresist as the transferred body from being exposed to light due to pinholes below a certain size of the semipermeable film, and can reduce the risk of pattern defects in the product.

Description

Halftone masks and halftone mask blanks

The present invention relates to a multi-gray-scale halftone mask and a halftone mask blank used in flat panel displays and the like.

In technical fields such as flat panel displays, phase shifters are not used, but multi-gray light masks called halftone masks (or gray tone masks) are used. This halftone mask has a semi-transparent film The transmittance to limit the exposure. By using a halftone mask, photoresist patterns with different film thicknesses can be formed by a single exposure, the number of lithography steps in the manufacturing steps of the flat panel display can be reduced, and the manufacturing cost can be reduced. Regarding such a semi-permeable film, the semi-permeable film is used as an auxiliary pattern of the pattern realized by the light-shielding film for the purpose of improving the resolution of the fine pattern, and it has substantially the same "phase shifter" used in the binary mask. Different functions.

The halftone mask for this purpose uses a semi-transmissive film having a transmittance between a transparent substrate and a light-shielding film. For example, a transparent substrate, a semi-transparent film, and a light-shielding film can achieve 3 gray scales. In addition, it is also possible to use semi-permeable films with a variety of transmittances to achieve a halftone mask of 4 gray levels or more.

Generally, in the manufacturing process of the photomask, when occasional defects such as pinholes occur due to foreign matter during film formation, developer mist when forming the photomask pattern, etc., the defects are caused by the use of photomask lithography. In the step, it is sensitized by the photoresist as the transferred body. Therefore, after the completion of the light mask, defect inspections should be performed, and the light mask should be repaired if necessary.

In the case of a halftone mask, the following technology has been used previously: When a pinhole defect of a semipermeable membrane is detected in the defect inspection step, a carbon film is formed at the pinhole part by using a FIB device (focused ion beam device) To fix the defect. Patent Document 1 discloses a technique in which the coordinates of pinhole defects are recognized by a defect inspection device, and a carbon film is formed at the pinhole portion using a FIB device.

[Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-256759

[Problems to be Solved by the Invention] As flat-panel displays have increased in image quality and patterns have been refined, countermeasures against poor exposure caused by fine pinholes have become increasingly important. However, generally speaking, the defect detection of halftone masks is more difficult than binary masks. That is, the defect inspection is to detect defects optically. Although the light-shielding film can be detected by the contrast of light, the semi-transparent film has the condition of light transmission, so it is not like a pinhole. It is difficult to detect the "white defect" caused by a part of the semipermeable membrane.

Therefore, when a small amount of pinholes (white defects) not detected by the defect inspection device remain, the photoresist is exposed to light by the halftone mask, and the photoresist is exposed to the pinholes, and the photoresist is present. There is a danger that the thickness of the film is locally thinner than the desired film thickness.

Patent Document 1 discloses a repair technology for forming a carbon film matching the transmittance of the semipermeable membrane at the pinhole portion by a FIB device. However, there is a problem in that the repair step is complicated, and when the defect size is small, the repair is difficult . In addition, the repair technology of forming a carbon film by the FIB device is used to repair the defects detected by the defect inspection device. Therefore, the defect below the sensitivity limit of the defect inspection device cannot be repaired, especially for the white semi-permeable membrane. Defects, there is a problem that the detection of minor defects is inherently difficult. Therefore, the photoresist after exposure by the halftone mask needs to be checked again for defects.

In view of this, the present invention provides the following halftone mask and a halftone mask blank for manufacturing the halftone mask. The halftone mask can prevent fine semi-transparent films that are difficult to detect due to a certain size or less. Pinholes (white defects) caused by poor exposure of the photoresist film.

[Means for Solving the Problem] The present invention proposes a halftone mask characterized by having a pattern of a light-shielding film and a pattern of a semipermeable film on a transparent substrate, and the transmittance of the semipermeable film relative to the transparent substrate is 20% to 50%, the retardation of the semipermeable film with respect to the transparent substrate is 60 degrees to 90 degrees.

In addition, in the halftone mask of the present invention, the transmittance of the semipermeable film with respect to the transparent substrate is 30%, and the retardation of the semipermeable film with respect to the transparent substrate is 80 degrees to 90 degrees.

By making the semi-permeable film in the half-tone mask have a specific phase difference, due to the interference effect at the boundary of the specific width of the transparent area and the semi-permeable film area, the semi-permeable film of the half-tone mask can be The pinholes below the specific size of the photoresist will not image dissection on the photoresist, or make the film thickness variation caused by the photoresist converge within the allowable range of the exposure margin (margin).

In the halftone mask of the present invention, the light shielding film is a chromium film, and the semipermeable film is a chromium oxide film, a nitride film, or an oxynitride film.

By controlling and adjusting the composition and thickness of the chromium oxide film, nitride film, or oxynitride film, it is possible to form a pattern of a semipermeable film with desired transmittance and phase difference on the halftone mask.

In the halftone mask of the present invention, the size of the pattern of the semipermeable film is reduced by a predetermined correction amount (correction value) relative to the design value.

By adopting such a semi-permeable film pattern, it is possible to eliminate defects of the photoresist due to fine pinholes below a certain size, and to form a photoresist pattern according to the design value.

The present invention also provides a halftone mask blank, which is characterized by having a semi-permeable film and a light-shielding film on a transparent substrate, the transmittance of the semi-permeable film relative to the transparent substrate is 20% to 50%, and the semi-permeable film The phase difference with respect to the aforementioned transparent substrate is 60 degrees to 90 degrees.

In addition, in the halftone mask blank of the present invention, the transmittance of the semipermeable film with respect to the transparent substrate is 30%, and the retardation of the semipermeable film with respect to the transparent substrate is 80 degrees to 90 degrees.

By using such a half-tone mask blank, a semi-permeable film that matches the specifications is selected to manufacture a half-tone mask, and a half-tone mask that can avoid the resolution of fine pinholes below a certain size of the semi-permeable film can be manufactured at low cost. Matte.

[Effects of the Invention] In summary, according to the present invention, a halftone mask blank and a halftone mask can be provided at low cost, which are aimed at pinholes below a specific size, especially below the detection limit that was difficult to repair in the past. The pinholes can also prevent pattern abnormalities caused by transfer. As a result, it is possible to provide a halftone mask that can reduce the risk of product pattern defects in the lithography step using the halftone mask of the present invention.

(Principle for solving the problem) According to the halftone mask of the present invention, the phase difference between the transparent substrate and the transparent substrate is set in a specific area for a semipermeable film having a predetermined transmittance with respect to exposure, thereby avoiding a specific size or less The pinholes of the photoresist are resolved on the photoresist, so there is no need to repair the pinholes of the semipermeable film, and the photoresist can be prevented from producing defects due to the pinholes.

That is, due to the interference effect of the exposure of the transparent area and the semi-permeable film area, the transmission intensity of the exposure near the boundary of the transparent area and the semi-permeable area is reduced, thereby reducing the lower limit of the resolution of the semi-permeable film to the hole shape The value is set to the target specific pinhole size or more, thereby preventing pinholes below the specific pinhole size from being resolved on the photoresist and causing the photoresist to open (the film thickness becomes zero or less than the allowable lower limit).

In addition, on the other hand, in the area near the pinhole, particularly in the semipermeable membrane area surrounding the pinhole, the exposure intensity is reduced, so the photoresist film thickness may become thicker. Therefore, for the transmittance of the semi-permeable film, and for the photoresist to be patterned by the lithography step, the phase shift range of the semi-permeable film is set in the optimal range, so that the needle of the semi-permeable film The thickness of the photoresist film at a portion corresponding to the hole is within the allowable range, thereby countermeasures against pinhole defects of the semipermeable film.

Therefore, the idea is completely different from the conventional method of detecting and repairing pinholes of the semipermeable membrane of the light mask, to prevent defects in the photoresist.

In this way, the solution to the problem of the present invention is to prevent defects of the photoresist by adjusting the resolution near the pinhole. Therefore, the optimum range of the phase shift of the semipermeable film also depends on the target semipermeable film The pinhole size. As an example, the transmittance of the semi-permeable film is determined according to the film thickness of the necessary photoresist. The transmittance of the semi-permeable film of the halftone mask is generally set to a value of about 30%. Therefore, the transmittance is 30% below The situation is explained in detail as an example. In addition, the following is explained: as the pinhole size, focusing on the size corresponding to the lower limit of the conventional defect inspection device, it can also be used for pinholes of semipermeable membranes that cannot be repaired in principle in the prior art Avoid photoresist defects caused by pinholes.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, each embodiment and each example do not provide a limited explanation in determining the gist of the present invention. In addition, the same reference numerals are sometimes attached to the same or the same components, and the description is omitted.

FIG. 1 shows the cross-sectional shape of a halftone mask of 3 gray scales. With the prior manufacturing technology, a pattern of a light-shielding film 2 made of, for example, a chromium film, and a pattern of a semipermeable film 3 made of, for example, chromium oxide, are formed on the transparent substrate 1.

The manufacturing process of a 3-gray halftone mask is as follows, for example. (1) First, prepare a light-shielding blank covering almost the entire surface of the transparent substrate 1 with the light-shielding film 2, form a first photoresist pattern on the light-shielding film 2, and use it as a mask to expose the light-shielding film 2 Etching is performed to form a light shielding pattern. (2) Next, after removing the remaining first photoresist pattern, a semipermeable film 3 covering the transparent substrate 1 and the light shielding film 2 is formed. (3) Next, a second photoresist pattern is formed on the semipermeable film 3, and the exposed semipermeable film 3 is etched using this as a mask to form a semitransparent pattern.

In addition, a semi-permeable film 3 and a light-shielding film 2 can also be sequentially formed on the transparent substrate 1, and a photoresist pattern can be used for etching in the order of the light-shielding film 2 and the semi-permeable film 3 to form a halftone mask. An etching stopper film is placed between the film and the light-shielding film, and is composed of at least the same type of film material. In addition, the light-shielding film is not limited to a single layer, as long as it has a structure that satisfies an optical density of 3.0 or more.

2 shows the phase difference dependence of the intensity of exposure (transmitted light) transmitted through pinholes (white defects) in the semipermeable film 3 with a diameter of 0.5-2 μm when the transmittance of the semipermeable film 3 is 30%. The symbols ◇, □, △, and ○ in the figure indicate the exposure intensities with pinhole diameters (defect sizes) of 2.0, 1.5, 1.0, and 0.5 μm, respectively. In addition, the transmittance is the transmittance of the semipermeable film 3 assuming that the transmittance of the transparent substrate 1 for exposure is 100%, and the retardation is the retardation of the semipermeable film 3 with respect to the transparent substrate 1. In addition, the exposure wavelength is the mixed wavelength of the i to g line.

In FIG. 2, the broken line A and the broken line B indicate the upper limit and the lower limit of the allowable range of exposure intensity. When the upper limit is exceeded, the photoresist is exposed to light, and the film thickness is greatly reduced (opening) and becomes a white defect. When it is below the lower limit, the exposure amount is insufficient, and the photoresist film thickness increases, which becomes a black defect.

According to Figure 2, the condition that the variation of the photoresist film thickness is within the allowable range of the exposure margin is that when the diameter of the pinhole is 0.5 μm, at least the phase difference is within the range of 30 degrees to 120 degrees. , When the diameter of the pinhole is 1.0μm, the phase difference is in the range of 30 degrees to 90 degrees, and when the diameter of the pinhole is 1.5 μm, the phase difference is in the range of 60 degrees to 90 degrees. When the diameter of the pinhole is 2.0 μm, the phase difference is in the range of 80 degrees to 110 degrees.

For example, the detection sensitivity of the defect inspection device is 1.5μm, and it is difficult to repair pinholes below the detection sensitivity. However, if the phase difference of the semipermeable membrane with respect to the permeable membrane is set to 60 to 90 degrees (the dotted chain in Figure 2 The range shown by the line), then such pinholes will not lighten the photoresist. Alternatively, even if a pinhole of 1.5 μm is detected in the defect inspection device, since it does not become a defect in the photoresist as the object to be transferred, there is no need for repair.

In addition, in order to allow the semipermeable membrane 3 to have a larger pinhole of 2.0 μm in diameter, a phase difference of 80 degrees to 90 degrees may be set. Therefore, regardless of the detection sensitivity of the defect inspection device, an appropriate pinhole size can be determined corresponding to the minimum size of the repair target, and the transmittance and phase difference can be set in accordance with it.

Figure 3 shows the surface shape of the photoresist in the case of exposure by a halftone mask, where the halftone mask is present on the semipermeable film 3 with a transmittance of 30% and a phase difference of 30 degrees and 80 degrees. Pinholes of various diameters. It can be understood that in the case of a phase difference of 30 degrees, a pinhole with a diameter of 2.0 μm sensitizes the photoresist of the transferred body and opens holes in the photoresist film. However, in the case of a phase difference of 80 degrees, The pinholes on the photoresist as the transferred body will not be resolved, preventing the photoresist from opening.

Fig. 4 shows the cross-sectional shape of the part corresponding to the pinhole of the photoresist exposed using a halftone mask with a pinhole of 2μm in diameter on the semipermeable film. The solid line shows the transmittance of 30% and the phase difference. The cross-sectional shape of the photoresist film thickness in the case of an 80-degree semipermeable film, and the broken line shows the cross-sectional shape of the photoresist film thickness in the case of a semipermeable film having a transmittance of 30% and a phase difference of 30 degrees.

In the case of a semi-permeable film with a phase difference of 30 degrees, there is an opening with a photoresist film thickness of 0 (zero). However, in the case of a semi-permeable film with a phase difference of 80 degrees, there is no opening and therefore With sufficient film thickness, white defects can be avoided, and the film thickness variation is also within the allowable range of the exposure margin.

As described above, the larger the size of the white defect to be tolerated, the stricter the control of the retardation is required. When the transmittance of the semipermeable membrane 3 changes, the value of the optimal retardation also changes. For example, when it is desired to allow a pinhole size of 1.5 μm, for a semi-permeable membrane with a transmittance of 30%, the range of the phase difference that satisfies the exposure margin is 60 degrees to 80 degrees, and it is desired to further allow it to a larger size of 2.0 μm. At this time, the phase difference needs to be controlled at 80 degrees. On the other hand, for the semipermeable membrane 3 with a transmittance of 50%, when it is desired to allow the pinhole size to be 1.5 μm, the phase difference ranges from 50 degrees to 70 degrees. When it is desired to allow the pinhole size to be 2.0 μm, the best The phase difference is 60 degrees.

In this way, according to the transmittance and the desired allowable pinhole size, the range and optimal value of the phase that should be controlled are changed. The optimal phase difference when the pinhole size is to be allowed to 2.0μm, the transmission of the semipermeable membrane When the rate is 10%, 20%, 30%, 40%, 50%, the optimum phase difference is 100 degrees, 90 degrees, 80 degrees, 70 degrees, and 60 degrees. The transmittance of the semipermeable membrane can be selected according to the customer's desire, etc., and the retardation can be determined for the transmittance.

As described above, by adjusting the retardation of the semipermeable membrane 3, even if there is a pinhole with a diameter below the detection limit of the inspection device, it is possible to prevent the occurrence of defective film thickness of the photoresist.

Therefore, from the halftone mask blank in which the semipermeable film 3 and the light-shielding film 2 are formed on the transparent substrate 1, the transmittance that matches the specifications of the mask (or the customer's request) is selected to manufacture the halftone mask Therefore, it is possible to avoid defects of the photoresist caused by fine pinholes below the detection limit, wherein the phase difference and transmittance of the semipermeable film 3 with respect to the transparent substrate 1 are 60 degrees to 90 degrees and 20%, respectively ~50%. As a result, the cost of the correction step of the halftone mask can be greatly reduced, and the product yield can be improved.

In addition, the transmittance and retardation can be controlled by the film thickness and composition of the semipermeable membrane, and by separately controlling the transmittance and retardation, a desired semipermeable membrane can be obtained. For example, if the phase difference and transmittance of films with different film thicknesses and compositions are measured and documented in advance, it is possible to form a semipermeable film that matches the specifications of the halftone mask.

As such a semipermeable film, for example, oxide films, nitride films, oxynitride films, and carbon oxide films of chromium (Cr), titanium (Ti), nickel (Ni), molybdenum (Mo), etc. can be used to adjust oxygen and nitrogen The composition and film thickness of, carbon, are sufficient.

These films can be formed by reactive sputtering. For example, in the adjustment of the composition of the chromium oxynitride film, it is possible to target chromium by sputtering using a gas obtained by mixing oxygen, nitrogen, or nitrous oxide in argon to form the film, and by changing the gas The mixing ratio (partial pressure) can control the composition. In addition, for example, in the case of a chromium oxide film, a mixed gas of argon and oxygen may be used, and in the case of a chromium nitride film, a mixed gas of argon and nitrogen may be used. In this case, a mixed gas of argon, oxygen, and carbon dioxide can be used. In addition, the same applies to other metals.

In addition to the reactive sputtering method, a reactive vapor deposition method or a CVD method using an organic metal source as a raw material can also be used to form a semipermeable film and control its composition.

The mechanism for avoiding the defects of the photoresist caused by the pinholes of the semipermeable membrane will be described in detail below.

Figure 5 shows (a) a halftone mask with patterns of a light-shielding film and a semipermeable film on a transparent substrate, and (b) exposure intensity distribution and (c) exposure in the case of exposure using the halftone mask Film thickness distribution of post-developed photoresist. In Figure 5 (b) and (c), the solid line represents the exposure intensity and the film thickness distribution of the photoresist film when the phase difference of the semipermeable film relative to the transparent substrate is 80 degrees, and the dotted line represents the semipermeable film relative to the transparent substrate. The exposure intensity when the phase difference of the substrate is 30 degrees and the film thickness distribution of the photoresist film. In addition, the transmittance of the semipermeable membrane is 30%, and the exposure wavelength is a mixed wavelength of i-line to g-line, NA=0.1.

As shown in FIG. 5(b), in either case, in the area of the light-shielding film of the halftone mask, the exposure intensity is 0, and in the area of the semi-permeable film, the exposure intensity is about 30%.

However, in the area of the semipermeable film near the boundary between the semipermeable film and the transparent substrate, compared to the semipermeable film with a retardation of 30 degrees, in the case of a semipermeable film with a retardation of 80 degrees, due to interference effects , The exposure intensity decreases.

On the other hand, as shown in Figure 5(c), the film thickness of the photoresist in the area of the transparent substrate is 0μm, and the film thickness of the photoresist in the area of the semipermeable film is the light of the light-shielding film area. Regardless of the film thickness between the film thicknesses of the resist, three types of film thickness regions are formed by one exposure.

It can be understood that in the region on the transparent substrate side near the boundary between the semipermeable film and the transparent substrate, the thickness of the photoresist film of the semipermeable film with a retardation of 80 degrees is increased compared to the semipermeable film with a retardation of 30 degrees. Larger, thicker than the photoresist film thickness of semi-permeable film That is, in a region of a specific size on the transparent substrate side of the periphery of the semipermeable film with a retardation of 80 degrees, the exposure intensity is reduced compared to the region of the semipermeable film. Therefore, compared with the thickness of the photoresist film in the region of the semipermeable film, the thickness of the photoresist film in the region of the specific size is formed to be thicker, and furthermore, with the distance from the semipermeable film, the photoresist The tendency of the agent film thickness to decrease.

Therefore, when there is a minute specific size on the semipermeable film, for example, a pinhole defect of 2 μm or less, the transparent substrate of the pinhole portion surrounded by the semipermeable film is exposed in the halftone mask. However, by setting the phase difference to 80 degrees, the photoresist film thickness equivalent to the region near the boundary between the semipermeable film and the transparent substrate has a sufficient film thickness, as shown in the cross-sectional view of FIG. The photoresist around the hole prevents the formation of pinholes in the photoresist film.

FIG. 6 shows an enlarged view of the vicinity of the boundary between the semipermeable film and the transparent substrate in the photoresist film thickness distribution of FIG. 5(c). In FIG. 6, the solid line shows the shape of the photoresist film when the phase difference between the semi-transparent film and the transparent substrate is 80 degrees, and the broken line shows the light when the phase difference between the semi-transparent film and the transparent substrate is 30 degrees. For the shape of the resist film, the one-dot chain line α shows the boundary position between the semipermeable film 3 and the transparent substrate 1.

As shown in Figure 6, when the phase difference is 80 degrees, compared with the phase difference of 30 degrees, when the diffracted exposure and the exposure through the semipermeable film interfere with each other at the boundary between the semipermeable membrane and the transmission region, Since it exerts a function of suppressing the exposure intensity near the boundary, the non-resolution region on the side surface of the photoresist expands to the transmission region side. Therefore, the size of the pattern width of the semipermeable membrane 3 is adjusted (sizing) according to the pre-designed value, whereby the width of the semipermeable membrane pattern can be determined.

Therefore, in order to realize, for example, a photoresist pattern having a pattern size of a design value determined by the characteristics of an electronic circuit (referred to simply as a design size for simplicity), the semi-transparent film 3 of the halftone mask is reduced in advance to have A semipermeable film for avoiding the phase difference of pinhole defects may be sufficient, for example, the difference between the pattern width dimension of the semipermeable film having a phase difference of 80 degrees and the width dimension of the photoresist pattern formed by exposure.

FIG. 7 is a plan view of a halftone mask showing the size correction of the semipermeable film. In FIG. 7, the dotted line D represents the pattern (or photoresist pattern) of the design size. With respect to the broken line D, the pattern size of the semipermeable film 3 having a phase difference for avoiding pinhole defects is reduced by the difference component s on each side. That is, with respect to the dotted line D, the pattern size is reduced by the correction amount -s (one side). In this way, by using the semi-permeable film 3 that has undergone size correction (or size change), the photoresist can achieve a desired pattern (pattern according to the design size), and can prevent pinholes caused by the semi-permeable film Open holes.

In addition, in order to prevent defects of the photoresist due to the pinholes of the semipermeable film 3, only the size of the semipermeable film may be corrected.

The above-mentioned correction amount (difference amount) depends on the transmittance of the semipermeable membrane and the NA value of the exposure device. FIG. 8 shows the results of analyzing the dependence of the correction amount on the transmittance and the NA value in the case of a phase difference of 80 degrees by simulation. The correction amount depends on the semi-transmittance and the NA of the exposure machine, and there is a tendency that as the transmittance increases, the absolute value of the correction amount increases, and as the NA of the exposure machine increases, the correction amount decreases.

Since it is possible to calculate the correction amount (difference component) by simulation using the transmittance and phase difference of the semi-permeable film and the NA value of the exposure machine, the halftone mask can be determined based on the design size of the semi-permeable film and the difference component The pattern on the semipermeable membrane 3.

In addition, it is also possible to obtain basic data on the semi-transmittance of the photoresist pattern shape and the dependence of the NA value of the exposure device in advance without simulation, and determine the difference based on the basic data.

In addition, when applying reduced exposure, the size of each pattern of the halftone mask can be multiplied by the reduction magnification.

In addition, in the above-mentioned embodiment, the halftone mask of 3 gray scales has been described. However, of course, the present invention can also be applied to multi-gray halftone masks of 4 gray scales or more provided with semipermeable films having different transmittances. In the tone mask.

By performing this size correction, it is possible to realize the shape of the photoresist in accordance with the designed pattern, and to obtain a halftone mask that can prevent defects in the photoresist due to the pinholes of the semipermeable film, in addition to reducing the manufacturing cost of the mask It can also improve the yield of flat panel displays.

1‧‧‧Transparent substrate 2‧‧‧Light-shielding film 3‧‧‧Semi-transparent film

Figure 1 is a cross-sectional view of a halftone mask with 3 gray levels. FIG. 2 is a graph showing the phase difference dependence of the exposure intensity of the pinhole portion. Fig. 3 is a graph showing the needle hole diameter dependence of the surface shape of a photoresist. 4 is a graph showing the phase difference dependence of the cross-sectional shape of a photoresist. FIG. 5 is a graph showing the dependence of the phase difference between the exposure intensity using a halftone mask and the thickness distribution of the photoresist. 6 is a graph showing the dependence of the retardation of the photoresist film thickness distribution in the vicinity of the boundary between the transparent substrate and the semipermeable film. FIG. 7 is a plan view showing the size correction of the semi-permeable film of the halftone mask. Fig. 8 is a graph showing the transmittance and NA dependence of the size correction amount of a semipermeable membrane.

Claims (7)

A halftone mask, characterized in that: a pattern of a light-shielding film and a pattern of a semipermeable film are provided on a transparent substrate, the transmittance of the semipermeable film relative to the transparent substrate is 20%-50%, and the semipermeable film is relatively The phase difference on the aforementioned transparent substrate is 60 degrees to 90 degrees, and it is a combination of transmittance and phase difference at which white defects below the specified size will not be resolved. This combination is obtained based on the size of the white defect It is derived from the relationship between transmittance and phase difference. The halftone mask according to claim 1, wherein the transmittance of the semi-permeable film with respect to the transparent substrate is 30%, the phase difference of the semi-permeable film with respect to the transparent substrate is 80 degrees to 90 degrees, and white The aforementioned prescribed size of the defect is 2.0 μm. The halftone mask according to claim 1, wherein the allowable size of white defects in the semipermeable film is 0.5 μm or more and 2.0 μm or less. The halftone mask according to any one of claims 1 to 3, wherein the light shielding film is a chromium film, and the semipermeable film is a chromium oxide film, a nitride film, or an oxynitride film. The halftone mask according to claim 1 or 2, wherein the size of the pattern of the semipermeable film is reduced by a predetermined correction amount relative to the design value. A halftone mask blank, which is characterized by having a semi-permeable film and a light-shielding film on a transparent substrate, and the transmittance of the semi-permeable film relative to the transparent substrate is 20%~ 50%, the retardation of the semipermeable film with respect to the transparent substrate is 60 degrees to 90 degrees, and it is a combination of transmittance and retardation that does not resolve white defects below the specified size. This combination is achieved by It is obtained from the relationship between the transmittance and the phase difference obtained from the size of the white defect. The halftone mask blank according to claim 6, wherein the transmittance of the semipermeable film with respect to the transparent substrate is 30%, and the phase difference of the semipermeable film with respect to the transparent substrate is 80 degrees to 90 degrees, The aforementioned prescribed size of the white defect is 2.0 μm.

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