CN115291471A - Photomask and manufacturing method thereof - Google Patents

Abstract

A photomask and a forming method thereof are provided, wherein the forming method comprises the following steps: providing a transparent substrate comprising a middle area and an edge area surrounding the middle area; forming a plurality of discrete shielding patterns on the surface of the middle area of the transparent substrate; providing a silica aerogel protective cover, adhering the silica aerogel protective cover to the surface of the edge area of the transparent substrate, sealing the shielding pattern and the middle area of the transparent substrate by using the silica aerogel protective cover to provide an annular frame, adhering the annular frame to the surface of the edge area of the transparent substrate, and surrounding the silica aerogel protective cover by using the annular frame; and forming a protective film on the top surface of the annular frame to seal the inner space of the annular frame. The method can prevent the generation of dust haze defects.

Description

Photomask and manufacturing method thereof

technical field

The present application relates to the field of photomasks, in particular to a photomask capable of preventing the generation of "haze" defects and a manufacturing method thereof.

Background technique

Photolithography is an indispensable and important technology in the integrated circuit manufacturing process. The photolithography process generally includes steps: firstly coat photosensitive materials such as photoresist on the surface of the wafer, and after the photoresist material is dried, expose the mask pattern on the photomask plate to the light with a specific light source through an exposure machine. On the photoresist photosensitive material, the photoresist photosensitive material is then developed with a developer to form a photoresist pattern on the surface of the wafer, and the photoresist pattern is used as a mask during the subsequent ion implantation process or etching process graphics.

The existing photomask pellicle structure generally includes: a transparent substrate; a number of discrete shielding patterns (or mask patterns) are formed on the surface of the transparent substrate; an annular frame is positioned on the surface of the transparent substrate, and the annular frame Surrounding the shielding pattern; a protective film on the top surface of the annular frame, the protective film and the annular frame are used to seal the photomask.

However, during the use of the existing photomask, growth defects in the form of foreign objects will be formed on the photomask, and these growth defects are also called "haze", which affects the precision and accuracy of exposure.

Contents of the invention

Some embodiments of the present application provide a method for manufacturing a photomask, including:

providing a transparent substrate comprising a middle region and an edge region surrounding the middle region;

forming several discrete masking patterns on the surface of the middle region of the transparent substrate;

A silica airgel protective cover is provided, and the silica airgel protective cover is adhered to the surface of the edge area of the transparent substrate, and the silica airgel protective cover seals the masking pattern and the transparent substrate. middle area

providing an annular frame, adhering the annular frame to the surface of the edge region of the transparent substrate, the annular frame enclosing the silica airgel protective cover;

A protective film closing the inner space of the ring frame is formed on the top surface of the ring frame.

In some embodiments, the silica airgel protective cover includes an annular side wall and a top wall connected to the annular side wall and closing an opening at one end of the annular side wall.

In some embodiments, the outer diameter of the silica airgel protective cover is less than or equal to the inner diameter of the annular frame, and the height of the silica airgel protective cover is less than or equal to the height of the annular frame.

In some embodiments, it also includes: forming support pillars on the surface of the shielding pattern, the size of the support pillars is smaller than the size of the shielding pattern; after adhering the silica airgel protective cover on the transparent When the surface of the edge region of the substrate is on the surface, the top surface of the support column is in contact with the inner surface of the silica airgel protective cover part.

In some embodiments, the silica airgel protective cover is adhered to the surface of the edge region of the transparent substrate through a first adhesive layer.

In some embodiments, the silica airgel protective cover has a refractive index of <1.01, a light transmittance of >=90%, a pore diameter of 1-6 nm, and a density of <3 kg/m3.

In some embodiments, the forming process of the silica airgel protective cover includes: providing a mold, the mold has a mold pattern corresponding to the shape of the silica airgel protective cover to be formed; Silica airgel is filled in the pattern of the mold to form a silica airgel protective cover; the mold is removed.

In some embodiments, the method of filling the silica airgel in the mold pattern includes a sol-gel method, a solvent deposition method or a chemical vapor deposition method.

In some embodiments, the silica airgel protective cover is used to adsorb ammonium ions, sulfate ions and pollution particles, preventing "haze" defects on the surface of the middle area of the photomask and the surface of the masking pattern .

In some embodiments, the ring frame is adhered to the edge area of the transparent substrate by a second adhesive layer.

Some embodiments of the present application also provide a photomask, which is characterized in that it includes:

a transparent substrate comprising a central region and an edge region surrounding the central region;

a plurality of discrete masking patterns on the surface of the intermediate region of the transparent substrate;

A silica airgel protective cover, the silica airgel protective cover is adhered to the surface of the edge region of the transparent substrate, and the silica airgel protective cover seals the masking pattern and the transparent substrate middle area

a ring frame, the ring frame is adhered to the surface of the edge region of the transparent substrate, the ring frame surrounds the silica airgel protective cover;

A protective film on the top surface of the annular frame enclosing the inner space of the annular frame.

In some embodiments, the silica airgel protective cover includes an annular side wall and a top wall connected to the annular side wall and closing an opening at one end of the annular side wall.

In some embodiments, the outer diameter of the silica airgel protective cover is less than or equal to the inner diameter of the annular frame, and the height of the silica airgel protective cover is less than or equal to the height of the annular frame.

In some embodiments, it also includes: a support column located on the surface of the masking figure, the size of the support column is smaller than the size of the masking figure, the top surface of the support column is in contact with the silica airgel The inner surface of the protective cover part is in contact.

In some embodiments, the silica airgel protective cover is adhered to the surface of the edge region of the transparent substrate through a first adhesive layer.

In some embodiments, the silica airgel protective cover has a refractive index of <1.01, a light transmittance of >=90%, a pore diameter of 1-6 nm, and a density of <3 kg/m3.

In some embodiments, the silica airgel protective cover is used to adsorb ammonium ions, sulfate ions and pollution particles, preventing "haze" defects on the surface of the middle area of the photomask and the surface of the masking pattern .

In some embodiments, a second adhesive layer is located between the annular frame and the surface of the edge region of the transparent substrate.

The method for forming a photomask in some of the aforementioned embodiments of the present application provides a transparent substrate, the transparent substrate includes a middle region and an edge region surrounding the middle region; several discrete A shielding pattern; a silica airgel protective cover is provided, and the silica airgel protective cover is adhered to the surface of the edge area of the transparent substrate, and the silica airgel protective cover seals the shielding pattern And the middle area of the transparent substrate provides a ring frame, the ring frame is adhered to the edge area surface of the transparent substrate, the ring frame surrounds the silica airgel protective cover; on the top of the ring frame The surface forms a protective film that closes the inner space of the ring frame. Because the silicon dioxide airgel protective cover that forms has the characteristics of low refractive index, high light transmittance, high porosity, and high adsorption, thereby the silicon dioxide airgel protective cover that forms will not be exposed to light. The exposure light in the process has an impact or a small impact (and because the silica airgel protective cover is in the shape of a cover, the thickness can be small, and the silica airgel protective cover will not interfere with the middle of the shielding pattern and the transparent substrate There is direct contact with the surface of the area, so it will have less impact on the exposure light), and the formed silica airgel protective cover can absorb the ammonium ions and sulfuric acid from the outside through the pores at the junction of the protective film of the photomask. Root ions and pollution particles (particles) will be adsorbed by the airgel, and the pollution particles (particles) that can be adsorbed by the protective film (the side facing the transparent substrate), pollution particles (particles) generated by the metal frame due to the environment, and adhesives The pollution particles (particles) produced by embrittlement caused by long-term ultraviolet light irradiation can be adsorbed, and the remaining chemicals (S, N, ammonium ions and sulfur ions, etc.) in the process of making photomasks can also be adsorbed by airgel , thereby preventing the formation of "haze" defects on the surface of the masking pattern, the surface of the middle region 21 of the photomask 20 and/or the surface of the phase shift layer during the use of the photomask, and improving the accuracy of exposure and accuracy.

Further, the refractive index of the silica airgel protective cover is <1.01, the light transmittance>=90%, the pore diameter is 1-6nm, and the density is <3kg/m ³ , under these specific parameters, the two The silica airgel protective cover 205 can better absorb ammonium ions, sulfate ions and corresponding pollution particles, while having minimal impact on exposure light.

Description of drawings

1-5 are structural schematic diagrams of the process of making a photomask in some embodiments of the present application;

6-8 are schematic structural diagrams of the formation process of the silica airgel protective cover in some embodiments of the present application;

Fig. 9 is a schematic diagram of the formation process of silica airgel in some embodiments of the present application.

Detailed ways

During the use of the existing photomask, growth defects in the form of foreign objects will be formed on the photomask, and these growth defects are also called "haze", which affects the precision and accuracy of exposure.

The study found that during the use of the photomask, the high-energy photons generated by the exposure light source will cause foreign matter-like growth defects (located on the transparent substrate and/or the surface of the masking pattern) to form on the photomask. Haze" defect.

Further studies have found that the material of the "haze" defect includes ammonium sulfate crystals, and the generation of the "haze" defect includes several reasons. 1) During the use of the photomask, the ammonium and sulfate radicals in the external environment Ions will enter the internal air through the pores at the junction of the protective film, react under the excitation of high-energy photons generated by the exposure light source, and finally attach to the photomask to form "haze" (ammonium sulfate crystals). 2), during the use of the photomask, the pollution particles (particles) adsorbed by the protective film (facing the transparent substrate side), the pollution particles (particles) produced by the metal frame due to the environment, and the adhesives due to long-term ultraviolet light Contamination particles (particles) produced by embrittlement caused by irradiation will enter the air inside the protective film, and finally adhere to the masking pattern or transparent substrate or halftone phase shift film, resulting in adhesion defects. 3) In the prior art, when making photomasks, various chemicals are used in the process, and some compounds remain in the photomasks. These compounds include ammonium ions and sulfur ions. The high-energy photons produced by them in the exposure light source Under excitation, the reaction will generate "haze" (ammonium sulfate crystals).

To this end, the present application provides a photomask and a manufacturing method thereof, which can prevent the "haze" defect of the photomask during use.

The specific implementation manners of the present application will be described in detail below in conjunction with the accompanying drawings. When describing the embodiments of the present application in detail, for the convenience of explanation, the schematic diagrams will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the protection scope of the present application. In addition, the three-dimensional space dimensions of length, width and depth should be included in actual production.

Some embodiments of the present application firstly provide a method for manufacturing a photomask, and the photomask manufacturing process will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 1 , a transparent substrate 201 is provided, the transparent substrate 201 includes a middle region 21 and an edge region 22 surrounding the middle region 21 ; several discrete shielding patterns 202 are formed on the surface of the middle region 21 of the transparent substrate 201 .

The transparent substrate 201 is used as a carrier of a photomask, and the material of the transparent substrate 201 is a light-transmitting material, and the light transmittance of the transparent substrate 201 is greater than 90%. In some embodiments, the material of the transparent substrate 201 may be quartz glass or soda glass. In some other embodiments, the material of the transparent substrate 201 may also be fused silica, calcium fluoride, silicon nitride, titanium oxide alloy, and sapphire.

The transparent substrate 201 includes a middle region 21 and an edge region 22 surrounding the middle region 21, the middle region 21 may be in the shape of a square or a circle or other suitable shapes, and the edge region 22 is in the form of a ring and surrounds the middle region 21. Area 21. The middle area 21 is used to form a shielding pattern (or mask pushing) 202, and the middle area 21 can also be used to form a phase shift layer, and the edge area 22 is subsequently used to form a ring frame.

The material of the shielding pattern 202 is an opaque material, and the shielding pattern 202 can be a single-layer or multi-layer stacked structure (such as a stacked structure of two or more layers). In some embodiments, the material of the masking pattern 202 may be one or more of nickel, aluminum, ruthenium, molybdenum, titanium or tantalum. In some other embodiments, the material of the mask pattern 202 can also be nickel, aluminum, ruthenium, molybdenum, titanium, tantalum, chromium oxide, iron oxide, niobium oxide, chromium nitride, molybdenum trioxide, molybdenum nitride, One or more of chromium oxide, titanium nitride, zirconium nitride, titanium oxide, tantalum nitride, tantalum oxide, silicon dioxide, niobium nitride, silicon nitride, neutral alumina, and aluminum oxide.

In some embodiments, the forming process of the shielding pattern 202 may include: forming a shielding material layer (not shown in the figure) on the surface of the transparent substrate 201 by sputtering or deposition; A patterned mask layer (such as a patterned photoresist layer) (not shown in the figure) is formed on the patterned mask layer, and the patterned mask layer exposes the area where the masking material layer needs to be etched; so The patterned mask layer is a mask, the exposed masking material layer is removed by etching, and the remaining masking material layer on the surface of the transparent substrate 201 is used as a masking pattern 202 .

In other embodiments, before forming the shielding pattern 202, a phase shift layer (not shown in the figure) may also be formed on the surface of the middle region 21 of the transparent substrate 201, and the phase shift layer is used to change the The phase of the exposure light within the exposure to improve the resolution of the exposure. The material of the phase shift layer is MoSi or MoSiON.

In some embodiments, after the shielding pattern 202 is formed, a supporting pillar (not shown in the figure) is formed on the surface of the shielding pattern 202, the size of the supporting pillar is smaller than the size of the shielding pattern 203, and the support After the column is used, when the silica airgel protective cover is adhered to the surface of the edge region of the transparent substrate, the top surface of the support column is in contact with the inner surface of the silica airgel protective cover part, Therefore, it plays a role of supporting the silica airgel protective cover, so as to improve the mechanical stability of the silica airgel protective cover. The support column can be made of light-transmitting or opaque material. In some embodiments, the material of the support pillars may be silicon oxide, silicon nitride or polysilicon.

Referring to Fig. 2, a silica airgel protective cover 205 is provided, and the silica airgel protective cover 205 is adhered to the surface of the edge region 22 of the transparent substrate 201, and the silica airgel protective cover 205 The masking pattern 202 and the middle area 21 of the transparent substrate 201 are sealed.

Because the silicon dioxide airgel protective cover 205 that forms has the characteristics of low refractive index, high light transmittance, high porosity, and high adsorption, thereby the silicon dioxide airgel protective cover 205 that forms will not The exposure light in the exposure process is affected or has little influence (and because the silica airgel protective cover 205 is a cover shape, the thickness can be small, and the silica airgel protective cover 205 will not interfere with the shielding pattern 202 There is direct contact with the surface of the middle area of the transparent substrate 201, so it will have less impact on the exposure light), and the formed silica airgel protective cover 205 can pass the outside world through the pores at the junction of the protective film of the photomask The incoming ammonium ions, sulfate ions and pollution particles will be adsorbed by the airgel, and the pollution particles (particles) adsorbed by the protective film (the side facing the transparent substrate) and the pollution particles generated by the metal frame due to the environment (particle), adhesives are adsorbed by pollution particles (particles) produced by embrittlement caused by long-term ultraviolet light irradiation, and can also remove residual chemicals (S, N, ammonium ions and sulfide ions, etc. ) can be adsorbed by airgel, thereby preventing the formation of "haze" on the surface of the masking pattern 202, the surface of the middle region 21 of the photomask 201 and/or the surface of the phase shift layer during the use of the photomask ” defects, improving the precision and accuracy of exposure.

The silica airgel protective cover 205 includes an annular side wall and a top wall that is connected with the annular side wall and closes an opening at one end of the annular side wall, and the silica airgel protective cover 205 is not closed. The opening faces the surface of the transparent substrate 201 and is bonded to the surface of the edge region 22 of the transparent substrate 201 .

In some embodiments, the outer diameter of the silica airgel protective cover 205 is less than or equal to the inner diameter of the subsequently formed annular frame, and the height of the silica airgel protective cover 205 is less than or equal to the subsequently formed annular frame. The height of the frame. In a specific embodiment, referring to FIG. 3 or FIG. 4, the outer diameter of the silica airgel protective cover 205 is smaller than the inner diameter of the subsequently formed annular frame 204, and the silica airgel protective cover 205 The height is smaller than that of the subsequently formed ring frame 204 (refer to FIG. 3 or FIG. 4 ). In another specific embodiment, referring to Fig. 5, the outer diameter of the silica airgel protective cover 205 is equal to the inner diameter of the ring frame 204 formed subsequently, and the height of the silica airgel protective cover 205 is equal to The height of the subsequently formed ring frame 204 . In another specific embodiment, the outer diameter of the silica airgel protective cover 205 is smaller than the inner diameter of the subsequently formed annular frame, and the height of the silica airgel protective cover 205 is equal to the subsequently formed annular frame the height of. In another specific embodiment, the outer diameter of the silica airgel protective cover 205 is equal to the inner diameter of the subsequently formed annular frame, and the height of the silica airgel protective cover 205 is smaller than that of the subsequently formed annular frame the height of.

In some embodiments, the silica airgel protective cover 205 has a refractive index <1.01, a light transmittance >=90%, a pore diameter of 1-6 nm, and a density of <3 kg/m ³ . In this case, the silica airgel protective cover 205 can better absorb ammonium ions, sulfate ions and corresponding pollution particles (particles), and at the same time have minimal impact on exposure light.

In some embodiments, referring to FIG. 2 , the silica airgel protective cover 205 is adhered to the surface of the edge region 22 of the transparent substrate 201 through the first adhesive layer 207 . The material of the first adhesive layer 207 is an organic adhesive, and in some embodiments, the organic adhesive is rubber adhesive, polyurethane adhesive, acrylic adhesive, SEBS (styrene vinyl butadiene Styrene Styrene) adhesive, SEPS (Styrene Ethylene Propylene Styrene) adhesive or silicone adhesive.

In some embodiments, referring to FIG. 6-FIG. 8, the forming process of the silica airgel protective cover includes: referring to FIG. 6, a mold 101 is provided, and the mold 101 has an The mold pattern 102 corresponding to the shape of the airgel protective cover; with reference to Figure 7, silica airgel is filled in the mold pattern to form a silica airgel protective cover 205; with reference to Figure 8, the mold is removed, A silica airgel protective cover 205 is obtained. After the silica airgel protective cover 205 is obtained, the silica airgel protective cover 205 is adhered to the surface of the edge region 22 of the transparent substrate 201 through the first adhesive layer 207 .

In one embodiment, the method of filling the silica airgel in the mold pattern includes a sol-gel method, a solvent deposition method or a chemical vapor deposition method.

Among them, the sol-gel method is to use compounds containing highly chemically active components as precursors. These raw materials are evenly mixed in the liquid phase, and undergo hydrolysis and condensation chemical reactions to form a stable transparent sol system in the solution. The sol is aged. The colloidal particles are slowly aggregated to form a gel with a three-dimensional space network structure. The gel network is filled with solvents that have lost fluidity. The gel is dried, sintered and solidified to prepare molecular and even nano-substructure or nano-structure aerogels.

In some embodiments, the silicon source used when forming the silica airgel protective cover 202 by the sol-gel method includes methyl orthosilicate, ethyl orthosilicate, silica sol or water glass.

In some embodiments, referring to FIG. 9 , the process of forming the silica airgel protective cover 202 using a sol-gel method and silicon source using tetraethyl orthosilicate includes: TEOS (orthoethyl silicate), Mix EtOH (ethanol) and H ₂ O (water); add acid to adjust the PH value, mix and stir and seal at a constant temperature to form SiO ₂ alcohol gel; after aging and surface modification, a modified alcohol gel is formed; after Solvent replacement and atmospheric pressure drying to form SiO ₂ aerogels.

After the airgel protective cover 202 is formed, referring to FIG. 3 , an annular frame 204 is provided, and the annular frame 204 is adhered to the surface of the edge region 22 of the transparent substrate 201, and the annular frame 204 surrounds the silicon dioxide gas. Gel protective cover 205.

The ring frame 204 is used to support the protective film formed subsequently, and the masking pattern 202 on the photomask plate 201 and the middle area surface of the photomask plate 201 can be separated from the outside by the ring frame 204 and the protective film formed subsequently. Environmental isolation to prevent contamination of the external environment.

The ring frame 202 is a hollow ring, and the material of the ring frame 202 is a material with certain mechanical strength. In some embodiments, the material of the ring frame 202 is aluminum. In some other embodiments, the material of the ring frame 202 may be aluminum alloy, ceramics, carbon steel or other suitable metal or non-metal materials.

In some embodiments, the ring frame 204 is adhered to the edge area of the transparent substrate through the second adhesive layer 203 .

The material of the second adhesive layer 203 is an organic adhesive, and in some embodiments, the organic adhesive is rubber adhesive, polyurethane adhesive, acrylic adhesive, SEBS (styrene vinyl butadiene Styrene Styrene) adhesive, SEPS (Styrene Ethylene Propylene Styrene) adhesive or silicone adhesive.

Referring next to FIG. 4 , a protective film 206 is formed on the top surface of the ring frame 204 to close the inner space of the ring frame 204 .

In this embodiment, when the top surface of the silica airgel protective cover 205 is lower than the top surface of the ring frame 204, the edge portion of the protective film 206 is located on the top surface of the ring frame 204, The middle portion of the protective film 206 is suspended over the top surface of the silica airgel protective cover 205 . In other embodiments, referring to FIG. 5 , the top surface of the silica airgel protective cover 205 is flush with the top surface of the annular frame 204 , and the edge portion of the protective film 206 is positioned on the annular frame 204 The top surface of the protective film 206 is located on the top surface of the silica airgel protective cover 205 .

The material of the protection film 206 is a light-transmitting material.

Some embodiments of the present invention also provide a photomask, referring to FIG. 4 , including:

a transparent substrate 201, the transparent substrate 201 comprising a middle region 21 and an edge region 22 surrounding the middle region 21;

Several discrete shielding patterns 202 located on the surface of the middle region 21 of the transparent substrate 201;

A silica airgel protective cover 205, the silica airgel protective cover 205 adheres to the surface of the edge region 22 of the transparent substrate 201, and the silica airgel protective cover 205 seals the shielding Figure 202 and the middle area 21 of the transparent substrate 201;

An annular frame 204, the annular frame 204 is adhered to the surface of the edge region 22 of the transparent substrate 201, and the annular frame 204 surrounds the silica airgel protective cover 205;

A protective film 206 located on the top surface of the ring frame 204 closes the inner space of the ring frame.

In the photomask plate of the present application, owing to have silica airgel protective cover 205, and silica airgel protective cover 205 has low refractive index, high light transmittance, high porosity, and high adsorption property. characteristics, thus the formed silica airgel protective cover 205 will not affect or have little impact on the exposure light in the exposure process (and because the silica airgel protective cover 205 is a cover shape, the thickness can be smaller, And the silica airgel protective cover 205 will not have direct contact with the surface of the intermediate area of the shielding pattern 202 and the transparent substrate 201, so it will have less impact on the exposure light), and the formed silica airgel protects The cover 205 can absorb the ammonium ions, sulfate ions and pollution particles (particles) that the outside world enters through the pores of the protective film junction of the photomask, and can be absorbed by the airgel, and can make the protective film (facing the transparent substrate side) The adsorbed pollution particles (particles), the pollution particles (particles) produced by the metal frame due to the environment, and the pollution particles (particles) produced by the embrittlement of the adhesive due to long-term ultraviolet radiation The remaining chemicals (S, N, ammonium ions and sulfide ions, etc.) The "haze" defect is formed on the surface of the middle region 21 and/or the surface of the phase shift layer, which improves the precision and accuracy of exposure.

In some embodiments, the silica airgel protective cover 205 includes an annular side wall and a top wall connected to the annular side wall and closing an opening at one end of the annular side wall.

In some embodiments, the outer diameter of the silica airgel protective cover 205 is less than or equal to the inner diameter of the annular frame 204, and the height of the silica airgel protective cover 205 is less than or equal to the annular frame 204 in height.

In some embodiments, it also includes: a supporting column (not shown in the figure) located on the surface of the shielding figure 202, the size of the supporting column is smaller than the size of the shielding figure 202, and the top surface of the supporting column Contact with the inner surface of the silica airgel protective cover 205 part.

In some embodiments, the silica airgel protective cover 205 is adhered to the surface of the edge area of the transparent substrate through the first adhesive layer 207 .

In some embodiments, the silica airgel protective cover 205 has a refractive index <1.01, a light transmittance >=90%, a pore diameter of 1-6 nm, and a density of <3 kg/m ³ . In this case, the silica airgel protective cover 205 can better absorb ammonium ions, sulfate ions and corresponding pollution particles (particles), and at the same time have minimal impact on exposure light.

In some embodiments, it further includes a second adhesive layer 201 located between the ring frame 204 and the surface of the edge region 22 of the transparent substrate 201 .

In some embodiments, the wavelength of the exposure light when using the photomask of the present application for exposure is 193nm-436nm.

It should be noted that the definitions or descriptions of the same or similar parts in some embodiments of the photomask of the present application as in some embodiments of the aforementioned photomask forming method will not be repeated here. For details, please refer to the aforementioned photomask Definitions or descriptions of corresponding parts in some embodiments of the plate forming method.

Although the present application has been disclosed as above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can use the methods and technical contents disclosed above to analyze the present application without departing from the spirit and scope of the present application. Possible changes and modifications are made in the technical solution. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the application without departing from the content of the technical solution of the application belong to the technical solution of the application. protected range.

Claims (18)

1. A method for making a photomask, comprising: providing a transparent substrate comprising a middle region and an edge region surrounding the middle region; forming several discrete masking patterns on the surface of the middle region of the transparent substrate; A silica airgel protective cover is provided, and the silica airgel protective cover is adhered to the surface of the edge area of the transparent substrate, and the silica airgel protective cover seals the masking pattern and the transparent substrate. middle area providing an annular frame, adhering the annular frame to the surface of the edge region of the transparent substrate, the annular frame enclosing the silica airgel protective cover; A protective film closing the inner space of the ring frame is formed on the top surface of the ring frame. 2. The method for making a photomask as claimed in claim 1, wherein the silica airgel protective cover comprises an annular side wall and is connected to and closes the annular side wall. A top wall that is open at one end. 3. The method for making a photomask as claimed in claim 1, wherein the outer diameter of the silicon dioxide airgel protective cover is less than or equal to the inner diameter of the ring frame, and the silicon dioxide gas The height of the gel protective cover is less than or equal to the height of the ring frame. 4. The method for manufacturing a photomask as claimed in claim 1, further comprising: forming support columns on the surface of the masking pattern, the size of the supporting columns is smaller than the size of the masking pattern; When the silica airgel protective cover is adhered to the surface of the edge area of the transparent substrate, the top surface of the support column is in contact with the inner surface of the silica airgel protective cover part. 5 . The method for manufacturing a photomask according to claim 1 , wherein the silica airgel protective cover is adhered to the surface of the edge area of the transparent substrate through a first adhesive layer. 6 . 6. The method for making a photomask as claimed in claim 1, wherein the silica airgel protective cover has a refractive index<1.01, a light transmittance>=90%, and an aperture particle diameter of 1 ~6nm, density<3kg/m3. 7. The manufacturing method of photomask as claimed in claim 1 or 6, is characterized in that, the forming process of described silica airgel protective cover comprises: providing a mold, has and to be formed in the described mold A mold pattern corresponding to the shape of the silica airgel protective cover; filling the silica airgel in the mold pattern to form a silica airgel protective cover; removing the mold. 8. The manufacturing method of photomask as claimed in claim 7, is characterized in that, the method for filling silicon dioxide aerogel in described mold pattern comprises sol-gel method, solvent deposition method or chemical vapor deposition method . 9. the manufacture method of photomask as claimed in claim 1 is characterized in that, described silica airgel protective cover is used for adsorption ammonium ion and sulfate ion and pollution particle, prevents photomask The surface of the middle area and the surface of the shadow figure produce "haze" defects. 10 . The method for manufacturing a photomask according to claim 1 , wherein the ring frame is adhered to an edge region of the transparent substrate through a second adhesive layer. 11 . 11. A photomask, characterized in that it comprises: a transparent substrate comprising a central region and an edge region surrounding the central region; a plurality of discrete masking patterns on the surface of the intermediate region of the transparent substrate; A silica airgel protective cover, the silica airgel protective cover is adhered to the surface of the edge region of the transparent substrate, and the silica airgel protective cover seals the masking pattern and the transparent substrate middle area a ring frame, the ring frame is adhered to the surface of the edge region of the transparent substrate, the ring frame surrounds the silica airgel protective cover; A protective film on the top surface of the annular frame enclosing the inner space of the annular frame. 12. The photomask according to claim 11, wherein the silicon dioxide airgel protective cover comprises an annular side wall and an opening connected to the annular side wall and closing one end of the annular side wall. top wall. 13. The photomask according to claim 11, wherein the outer diameter of the silicon dioxide airgel protective cover is smaller than or equal to the inner diameter of the ring frame, and the silicon dioxide airgel protective cover The cover height is less than or equal to the height of the ring frame. 14. The photomask as claimed in claim 13, further comprising: a support post located on the surface of the mask pattern, the size of the support post is smaller than the size of the mask pattern, and the support post The top surface is in contact with the inner surface of the silica airgel shield portion. 15. The photomask according to claim 11, wherein the silica airgel protective cover is adhered to the surface of the edge area of the transparent substrate through a first adhesive layer. 16. The photomask according to claim 11, wherein the silica airgel protective cover has a refractive index<1.01, a light transmittance>=90%, and a pore size of 1-6nm. Density <3kg/m ³ . 17. The photomask as claimed in claim 11, wherein the silica airgel protective cover is used to adsorb ammonium ions and sulfate ions and contamination particles to prevent the middle area of the photomask from Surfaces and surfaces that obscure graphics produce "haze" defects. 18. The photomask of claim 11, wherein a second adhesive layer is located between the ring frame and the surface of the edge region of the transparent substrate.

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