JP2012199437A - Method of manufacturing semiconductor element and photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor element and a photomask by which a photomask and a semiconductor wafer can be easily separated even if the photomask is strongly adhered to a negative photoresist.SOLUTION: There is provided a method of manufacturing a semiconductor element comprising: a step of applying a negative photoresist on a surface of a wafer; a first exposure step of performing an exposure by adhering a surface of a first photomask and the negative photoresist, the surface of the first photomask including a groove portion provided in a region which is included in a surface on which a mask pattern is provided and in which the mask pattern is not provided; a first separation step of introducing a gas via the groove portion and separating the first photomask and the wafer on which the negative photoresist is applied; a development step of developing the negative photoresist and forming a pattern of the negative photoresist including an opening; and a step of forming an electrode using liftoff technology on the surface of the wafer exposed to the opening.

Description

  Embodiments described herein relate generally to a method for manufacturing a semiconductor device and a photomask.

  When the photoresist coated on the surface of the semiconductor wafer and the photomask are closely exposed, the resolution is increased, but the photomask and the photoresist may be excessively adhered.

  For example, when a cyclized rubber negative photoresist is applied to a polished mirror surface, it may be difficult to separate the semiconductor wafer and the photomask. In particular, a large-diameter and thin wafer causes cracking and chipping in the separation process, thereby reducing productivity.

  If a groove is provided in a region where the mask pattern layer is not formed on the surface of the photomask and air is introduced into the groove, it is easy to separate the photomask and the semiconductor wafer. However, there is a problem that chipping caused by providing a groove in the photomask and insufficient exposure due to light scattering in the groove.

Japanese Patent Laid-Open No. 62-5243

  Provided are a method for manufacturing a semiconductor element and a photomask capable of easily separating a photomask and a semiconductor wafer even when the adhesion strength between the negative photoresist and the photomask is high.

  A step of applying a negative photoresist on the surface of the wafer; and the surface of the first photomask having a groove portion provided in a region where the mask pattern is not provided among the surfaces provided with the mask pattern; A first exposure step in which the negative photoresist is exposed in close contact, and a gas is introduced through the groove, and the first photomask and the wafer coated with the negative photoresist are provided. A first separation step of separating; a developing step of developing the negative photoresist to form a pattern of the negative photoresist having an opening; and a lift-off method on the surface of the wafer exposed in the opening And a step of forming an electrode using the method. A method of manufacturing a semiconductor device is provided.

FIG. 1A is a schematic plan view of a photomask used in the method for manufacturing a semiconductor device according to the first embodiment, and FIGS. 1B to 1D are processes for separating the photomask from the semiconductor wafer. FIG. 2A to 2D are process cross-sectional views until an electrode is formed on one surface of a semiconductor wafer in the semiconductor element manufacturing method according to the first embodiment. 5 is a flowchart until an electrode is formed in the method for manufacturing a semiconductor device according to the first embodiment. 4A to 4C are process cross-sectional views until an opening is provided in a photoresist in the method of manufacturing a semiconductor device according to the second embodiment. 5 is a flowchart until an electrode is formed in the method for manufacturing a semiconductor element according to the second embodiment. 6A to 6D are process cross-sectional views of a method for manufacturing a light-emitting element according to a comparative example. FIG. 7A is a schematic plan view of a first photomask used in a modification of the method for manufacturing the light emitting device according to the second embodiment, and FIG. 7B is a schematic plan view of the second photomask. is there. It is a model perspective view of the light emitting element manufactured by the manufacturing method of this embodiment. It is process sectional drawing of the manufacturing method of the photomask concerning embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a schematic plan view of a photomask used in the method for manufacturing a semiconductor device according to the first embodiment, and FIGS. 1B to 1D are processes for separating the photomask from the semiconductor wafer. FIG.

  The (first) photomask 30 includes a mask base material made of quartz or glass, a mask pattern region 31 made of a chromium film or the like provided on the surface 30a, and the mask pattern region 31 of the surface 30a. And a groove portion 32 provided in a non-region. The thickness of the mask base material is, for example, 5 mm.

FIG. 1A shows a surface 30 a provided with a mask pattern region 31 and a groove 32.
As for the number of the groove parts 32, two lines parallel to the X axis and two lines parallel to the Y axis are provided. However, the number and arrangement of the groove portions 32 are not limited to this. For example, the number of the groove portions 32 may be 1 to 100. Further, the arrangement of the grooves 32 may be asymmetrical or irregular. For example, when the number of the groove portions 32 is not so large as 2 to 10 or the like, the groove portions 32 can be easily formed, and the photomask 30 and the semiconductor wafer 44 can be easily separated.

When the contact exposure process is used, it is easy to increase the resolution of the resist pattern. In FIG. 1B, a negative photoresist (not shown) is applied to the surface of the semiconductor wafer 44 by a spin coating method or the like, and cured by a heat treatment or the like (resist baking). The semiconductor wafer 44 is placed on the stage 50 with the negative photoresist on the upper side, and the semiconductor wafer 44 is fixed to the stage 50 by vacuum suction or the like. In this state, exposure is performed with light G from the light source while the negative photoresist and the mask pattern region 31 are in close contact with each other.
The semiconductor wafer 44 may be any semiconductor as long as it contains a semiconductor, and the entire semiconductor wafer 44 is not necessarily made of a semiconductor. For example, the “semiconductor wafer 44” includes a substrate or a layer made of a material other than a semiconductor and a semiconductor layer laminated.

  Subsequently, as shown in FIG. 1C, the stage 50 and the photomask 30 are relatively separated. At this time, the semiconductor wafer 44 is desirably maintained in a state of being vacuum-sucked on the stage 50. Then, a gas 36 such as air is introduced into the groove 32. In this case, the end of the groove 36 functions as an air inlet for the gas 36. The gas 36 introduced into the groove 32 spreads between the negative photoresist and the photomask 30, and the semiconductor wafer 44 and the photomask 30 are separated as shown in FIG. Since the gas 36 is introduced from the groove 32 so as to spread on the semiconductor wafer 44, the separation between the photomask 30 and the semiconductor wafer 44 can be promoted.

  When the groove portion 32 is not provided in the photomask 30, the photomask 30 and the semiconductor wafer 44 stick to each other, and the stage 50 and the photomask 30 are relatively separated while the wafer 44 is vacuum-adsorbed to the stage 50. However, the wafer 44 may not be separated from the photomask 30. In other words, the force of sticking to the photomask 30 is greater than the force of vacuum suction to the stage 50, and the wafer 44 may be separated from the stage 50 while part of the wafer 44 is stuck to the photomask 30. In this case, the wafer 44 is cracked or broken. Further, when the entire wafer 44 is stuck to the photomask 30, peeling may be difficult.

  On the other hand, according to the present embodiment, by providing the groove 32 in the photomask 30, it is possible to prevent the semiconductor wafer 44 and the photomask 30 from sticking to each other. As a result, it is possible to prevent the semiconductor wafer 44 from being cracked or chipped when the semiconductor wafer 44 fixed to the photomask 30 is peeled off.

2A to 2D are process cross-sectional views until an electrode is formed on one surface of a semiconductor wafer in the semiconductor element manufacturing method according to the first embodiment.
FIG. 3 is a flowchart up to formation of electrodes in the method of manufacturing a semiconductor device according to the first embodiment.

The semiconductor wafer 44 is, for example, a GaP substrate 40 having translucency, provided on the GaP substrate 40 includes a light-emitting _{layer, In x (Al y Ga 1} -y) 1-x P (0 ≦ x ≦ 1 , 0 ≦ y ≦ 1), and the like. However, the semiconductor wafer 44 may be another compound semiconductor or a material such as Si. Further, the semiconductor element is not limited to the light emitting element. The GaP substrate 40 has a predetermined thickness, for example, a surface after polishing is used as a mirror surface, and an electrode or the like is formed thereon.

  As shown in FIG. 2A, a negative type photoresist 30 such as a cyclized rubber is applied to the mirror surface 40a obtained by mirror polishing the surface of the GaP substrate 40 having a flat surface (FIG. 3). S100). The mask pattern region 31 side of the photomask 30 and the surface 20a of the photoresist 20 are brought into close contact with each other, and a first exposure process is performed (S102 in FIG. 3).

  The photomask 30 has a structure in which a mask pattern layer 31a made of a light shielding body is formed on the surface of a light-transmitting substrate such as glass or quartz. In the mask pattern region 31, various mask patterns for forming active elements can be formed. FIG. 2A shows a mask pattern layer 31a for forming electrodes on the mirror surface 40a. In the specific example shown in FIG. 2A, the mask pattern layer 31a functions as a light-shielding region (for example, black) for forming electrodes by the lift-off method. The planar shape can be, for example, an annular shape with a width of 2 to 10 μm.

  The groove 32 is provided in any one of the dicing load regions where the mask pattern layer for the active element is not provided. Here, the dicing load region is a region provided between a plurality of semiconductor elements formed on the wafer, and is a region for separating these semiconductor elements by a method such as dicing, scribing, or cleavage. In general, the dicing load region is a light transmitting region of the negative photomask 30. Therefore, in the specific example shown in FIG. 2A, the negative photoresist 20 in the region facing the groove 32 is supposed to be exposed.

  After completion of the first exposure process, the photomask 30 is separated from the semiconductor wafer 44. At this time, a gas such as air is introduced through the groove 32, and the separation between the semiconductor wafer 44 coated with the photoresist 20 and the photomask 30 is promoted (FIG. 1C). For this reason, the photomask 30 and the semiconductor wafer 44 can be easily separated (S104 in FIG. 3).

  Subsequently, when the photoresist 20 is developed (S106 in FIG. 3), a desired opening 21 is formed as shown in FIG. 2B. Subsequently, an electrode 61 made of the metal film 60 is formed on the surface 40a of the GaP substrate 40 by using a lift-off method (S108 in FIG. 3). That is, as shown in FIG. 2C, the metal film 60 is formed on the opening 21 and the surrounding photoresist 20 by using a vapor deposition method or a sputtering method. Further, when the photoresist 20 is peeled off, the metal film 60 on the photoresist 20 is removed and the electrode 61 can be left in the opening 21 as shown in FIG.

  In this case, as shown in FIG. 2B, when the end portion on the opening 21 side of the negative photoresist 20 is formed in a reverse taper shape, the metal film 60 is improved from the pattern of the patterned photoresist 20. Can be separated. That is, a so-called step break can be caused in the metal film 60. In this case, if a negative photoresist containing an alkali-soluble resin as a negative photosensitive composition is used, a reverse taper shape can be easily formed.

As described above with reference to FIG. 2, according to the present embodiment, by providing the groove 32 in the photomask 30, separation of the semiconductor wafer 44 can be promoted.
However, providing the groove 32 may reduce the light transmittance of that portion. When the negative resist is exposed, if the exposure amount of the negative resist immediately below the groove 32 is reduced, the negative resist that should remain after the development may disappear. This can cause pattern defects.

On the other hand, in the second embodiment of the present invention, it is possible to solve the shortage of the exposure amount in the portion immediately below the groove portion 32.
4A to 4C are process cross-sectional views until an opening is provided in a photoresist in the method of manufacturing a semiconductor device according to the second embodiment.
FIG. 5 is a flowchart until the electrodes are patterned in the method of manufacturing a semiconductor device according to the second embodiment.

  First, as shown in FIG. 4A, a negative type photoresist 30 such as cyclized rubber is applied to the mirror surface 40a of the GaP substrate 40 having a flat surface (S200 in FIG. 5). The mask pattern region 31 side of the photomask 30 and the surface 20a of the photoresist 20 are brought into close contact with each other, and a first exposure process is performed (S202 in FIG. 5). In this case, the negative photoresist 20 in the region facing the groove 32 should be originally exposed. However, in the dicing process of the groove 32, a dent (or unevenness) 32a may be formed on the bottom surface of the groove 32. If there is a dent (or unevenness) 32a, the light from the exposure light source is scattered, resulting in an underexposed region 20b. Alternatively, even if chipping generated in the dicing process of the groove 32 remains in the vicinity of the groove 32, the underexposed region 20b is generated.

  When the underexposed area 20b is developed, the photoresist 20 disappears in an area where the photoresist 20 should be left, and an unnecessary opening is generated. In the second embodiment, in order to suppress the generation of such an unnecessary opening, gas is introduced through the groove 32 to separate the photomask 30 and the semiconductor wafer 44 (S204), and then the second. An exposure process is performed (S206).

  For example, as shown in FIG. 4B, the same photomask 30 can be exposed while being shifted from the semiconductor wafer 44 by a predetermined distance. That is, the groove 32 is brought into contact with the semiconductor wafer 44 at a location different from the location where the groove 32 is in contact in the first exposure step. Such a second exposure step can be referred to as shift exposure (S206). Subsequently, the photomask 30 and the semiconductor wafer 44 are separated (S208).

  For the underexposure region 20b generated in the first exposure step, the second exposure step is performed in the region of the photomask 30 where the groove 32 is not provided. For this reason, the exposure amount becomes sufficient, and generation of unnecessary openings in the developing process can be suppressed as shown in FIG. 4C (S210). Thus, in the electrode lift-off process, it is possible to form an electrode without leaving an unnecessary metal film (S212).

  6A to 6D are process cross-sectional views of a method for manufacturing a light-emitting element according to a comparative example.

  If the second exposure process is not performed, an unnecessary opening 122 is generated in the underexposed area 120b by the developing process as shown in FIG. 6B. For this reason, as shown in FIG. 6C, the unnecessary metal film 162 is also deposited on the surface of the semiconductor wafer 144. For this reason, as shown in FIG. 6D, in the lift-off process of the electrode 161, an unnecessary metal film 162 may be formed also in the underexposed region 120b below the groove 132. If there are many unnecessary metal films 162 in the dicing road, chipping including unnecessary metal films 162 and the like on the surface of the chip occurs, which is not preferable, and the appearance is also poor.

  In the present embodiment, the groove 32 can have a width of 20 to 30 μm and a depth of 20 μm, for example, in order to facilitate separation of the photomask 30 and the semiconductor wafer 44. In this case, the groove 32 can be formed by, for example, a dicing method using a diamond blade. However, fine irregularities are generated on the bottom and inner walls of the groove 32 formed by rotating the diamond blade. For this reason, a region that is insufficiently exposed may be generated by the light transmitted through the groove 32 and scattered. On the other hand, in the second embodiment, the lift-off of the electrode is facilitated by performing the shift exposure.

  FIG. 7A is a schematic plan view of a first photomask used in a modification of the method for manufacturing the light emitting device according to the second embodiment, and FIG. 7B is a schematic plan view of the second photomask. is there.

  That is, in the present modification, when the second exposure process is performed on the underexposed region 20b, the second photomask 38 different from the first photomask 30 is used. For example, the first photomask 30 is provided with two grooves 32 parallel to the X-axis and the Y-axis at an intermediate portion of the mask base material.

  The second photomask 38 has a light-transmitting region 39 that can be exposed to a region of the photoresist immediately below the groove 32 in the first exposure step. That is, two flat light transmission regions 39 parallel to the X axis and the Y axis are provided. The width of the light transmitting region 39 is preferably slightly larger than the width of the groove 32 of the first photomask 30 and does not overlap the mask pattern region 31.

  Further, since the non-exposed region below the mask pattern layer 31a of the electrode in the first exposure step is not exposed in the second exposure step, a light shielding region having a larger area than the mask pattern layer 31a is provided. In this case, for example, a wide area other than the light-transmitting region 39 may be used as a light-shielding region (for example, black). Further, in order to easily separate the second photomask 38 and the semiconductor wafer 44, it is preferable to provide the groove portion 32 in addition to the light transmitting region 39.

  Thus, even if an underexposed region is generated in the vicinity of the groove 32 in the first exposure step, exposure can be added in the second exposure step to form a desired photoresist pattern.

  According to the first and second embodiments and the modifications thereof, it is possible to easily separate a photomask and a semiconductor wafer while using a negative photoresist that is chemically stable and has high mechanical strength. It becomes easy. For this reason, compared with the manufacturing method using a positive photoresist, the manufacturing method of a semiconductor element rich in mass productivity is attained.

FIG. 8 is a schematic perspective view of the light emitting device according to the present embodiment.
An epitaxial layer side electrode 70 is provided on the surface of the epitaxial layer 42. On the other hand, an electrode 61 as shown in FIG. 2D is provided on the mirror surface 40a of the GaP substrate 40 made of a single crystal having translucency, and can be bonded to the mounting member side. The emitted light from the light emitting layer 42a is emitted upward, laterally, and downward of the light emitting element.

  According to the experiments of the present inventor, the mirror surface 40a of the substrate of such a light emitting element has high adhesion strength with the negative photoresist, and is likely to be cracked or chipped in the process of separating the photomask and the semiconductor wafer. It has been found. For example, when the wafer diameter is 3 inches or more and the wafer thickness is 200 μm or less, the adhesion strength is further increased and separation is difficult. For this reason, it is not easy to separate the photomask and the semiconductor substrate coated with the negative photoresist, and as a result, it is difficult to form electrodes using the lift-off method.

  Furthermore, the laminated body of the GaP substrate 40 and the InAlGaP-based epitaxial layer 42 tends to bend into a shape that protrudes downward in FIG. Therefore, for example, in the step shown in FIG. 2A, the semiconductor wafer 44 to which the photomask 30 is closely attached has a stress that tends to bend in a direction that protrudes downward in FIG. 2A. Works. This stress tends to deform the semiconductor wafer 44 in contact with the photomask 30 like a so-called sucker. As a result, adhesion between the photomask 30 and the semiconductor wafer 44 is promoted, and separation is often difficult. This tendency becomes more prominent as the semiconductor wafer 44 becomes larger in diameter and thinner.

  Actually, according to an experiment by the present inventor, when the semiconductor wafer 44 is curved so as to have a convex shape with respect to the photomask 30, it is found that the photomask 30 and the semiconductor wafer 44 are hardly fixed. did. This is considered to be because when the stress that causes the semiconductor wafer 44 to be convexly curved acts on the photomask 30, separation proceeds from the peripheral edge of the semiconductor wafer 44 and air is easily introduced sequentially. It is done.

  On the other hand, when the semiconductor wafer 44 is curved in a concave shape, that is, sucker shape with respect to the photomask 30, separation from the peripheral edge of the semiconductor wafer 44 and introduction of air becomes difficult, and the photomask 30 and the semiconductor wafer 44 are fixed to each other. Is likely to occur.

  On the other hand, according to the present embodiment, by providing the groove portion 32 in the photomask 30, the semiconductor wafer 44 on which the stress that deforms in a sucker shape acts on the photomask 30 is surely removed from the photomask 30. And it becomes possible to separate easily. As a result, in a semiconductor wafer including a laminated body of a GaP substrate and an InAlGaP-based epitaxial layer, even when patterning is performed on the GaP substrate side, it is possible to prevent adhesion to the photomask 30 and to achieve a stable process. Is possible.

Furthermore, negative photoresists are often made of cyclized rubber materials. It has also been found that the cyclized rubber-based material has high adhesiveness and is easily fixed to the photomask 30.
On the other hand, when the semiconductor element manufacturing method according to the first and second embodiments and the modifications associated therewith is used, the photomask 30 and the semiconductor wafer 44 coated with the negative photoresist 20 can be easily formed. And can be reliably separated. In addition, the use of the negative photoresist 30 makes it possible to manufacture a light emitting device with high productivity.

  FIG. 9 is a process cross-sectional view of the photomask manufacturing method according to the embodiment.

  As shown in FIG. 9A, a groove forming photoresist 81 is applied to the first surface of a mask substrate 80 made of quartz or the like. As shown in FIGS. 9B to 9D, the dicing blade 84 is rotated from above the photoresist 81 to form the groove 83. As shown in FIG. 9 (d), the chip residue due to dicing is accumulated on the photoresist 81 as a chipping 85 or the like, but adhesion to the surface of the mask substrate 80 can be suppressed.

Subsequently, as shown in FIG. 9E, the groove forming photoresist 81 is peeled off, and the mask substrate 80 is washed. At this time, the chipping 85 is removed together with the photoresist 81, and the surface of the mask substrate 80 can be cleaned. Further, as shown in FIG. 9F, the unevenness of the bottom surface and the inner side wall of the groove 83 generated by dicing is covered with a coating material 86 such as light-transmitting SiO ₂ to reduce light scattering. Since the thickness of the coating material 86 is smaller than the depth of the groove 83, a gas can be introduced.

  The difference between the refractive index of the coating material 86 and the refractive index of the mask base material 80 is made smaller than the difference between the refractive index of the mask base material 80 and the refractive index of air. Further, the difference between the light transmittance of the coating material 86 and the light transmittance of the mask base material 80 is made smaller than the difference between the light transmittance of the mask base material 80 and the light transmittance of air. In this way, an underexposed region of the photoresist caused by light being scattered by the groove 83 is suppressed, and a desired photoresist pattern can be easily formed. The coating material 86 may be provided so as to extend to the mask pattern region.

  Thereafter, for example, a chromium film is applied to one surface of the mask substrate 80. Further, a drawing photoresist is applied on the chromium film. A desired mask pattern is drawn on the mask pattern region where the groove 83 is not formed. Subsequently, the photo resist for drawing is peeled off and the mask substrate 80 is washed to complete the photo mask. That is, the photomask according to the embodiment having the planar shape shown in FIG. 1A and the groove 32 having the cross-sectional shape shown in FIG. 9F is completed.

  When the photomask of this embodiment is used, the occurrence of an underexposed region below the groove is suppressed in the semiconductor element manufacturing process. For this reason, a yield is improved and the manufacturing method rich in mass productivity is provided.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

20 photoresist, 21 opening, 30 (first) photomask, 31 mask pattern region, 32 groove, 36 gas, 38 second photomask, 39 translucent region, 42 epitaxial layer, 42a light emitting layer, 44 semiconductor Wafer, 61 electrodes, 80 mask base material, 83 groove, 86 coating material

Claims (7)

Applying a negative photoresist to the surface of the wafer;
Of the surface provided with the mask pattern, the surface of the first photomask having a groove provided in a region where the mask pattern is not provided and the negative photoresist are exposed in close contact with each other. 1 exposure process;
A first separation step of introducing a gas through the groove and separating the first photomask and the wafer coated with the negative photoresist;
Developing the negative photoresist to form a pattern of the negative photoresist having an opening; and
Forming an electrode on the surface of the wafer exposed in the opening using a lift-off method;
A method for manufacturing a semiconductor device, comprising:   2. The method of manufacturing a semiconductor device according to claim 1, wherein the wafer includes a light-transmitting single crystal substrate and an epitaxial layer provided on the single crystal substrate and including a light emitting layer.   3. The method of manufacturing a semiconductor device according to claim 1, wherein an end portion of the negative photoresist on the opening side has a reverse tapered cross section. 4. Applying a photoresist to the surface of the wafer;
First exposure for exposing the surface of the first photomask having a groove provided in a region where the mask pattern is not provided, and the photoresist, in close contact with the surface provided with the mask pattern. Process,
A first separation step of introducing a gas through the groove to separate the first photomask and the wafer coated with the photoresist;
A second exposure step of shifting and exposing the first photomask so that the groove is located in a region different from the region of the wafer located below the groove in the first exposure step;
A second separation step of separating the first photomask and the semiconductor wafer coated with the photoresist by introducing a gas through the groove after the second exposure step;
A method for manufacturing a semiconductor device, comprising: Applying a photoresist to the surface of the wafer;
First exposure for exposing the surface of the first photomask having a groove provided in a region where the mask pattern is not provided, and the photoresist, in close contact with the surface provided with the mask pattern. Process,
A first separation step of introducing a gas through the groove to separate the first photomask and the wafer coated with the photoresist;
A second photomask having a mask pattern for shielding a region shielded by the mask pattern in the first exposure step and a groove portion, and using the second photomask having the groove portion of the first photomask. A second exposure step of exposing a region without passing through the groove of the second photomask;
A second separation step of separating the first photomask and the semiconductor wafer coated with the photoresist by introducing a gas through the groove after the second exposure step;
A method for manufacturing a semiconductor device, comprising:   6. The method of manufacturing a semiconductor device according to claim 1, wherein the wafer has a stress that curves in a concave shape with respect to the first photomask. A mask base material provided with a groove from the side of the first surface;
A mask pattern provided in a region of the first surface where the groove is not provided;
A coating material that covers at least the bottom surface of the groove and has a thickness smaller than the depth of the groove;
With
The difference between the refractive index of the coating material and the refractive index of the mask base material is smaller than the difference between the refractive index of the mask base material and the refractive index of air,
The difference between the light transmittance of the coating material and the light transmittance of the mask base material is smaller than the difference between the light transmittance of the mask base material and the light transmittance of air.

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