Blank photomask substrate, preparation method and regeneration mode

Abstract

The invention relates to the technical field of semiconductor product preparation, and particularly provides a blank photomask substrate, a preparation method and a regeneration mode, the blank photomask substrate comprises a substrate, and the substrate is sequentially provided with a spacing layer, a plurality of optical film layers and a photoresist layer from bottom to top; according to the preparation method provided by the invention, before the raw material substrate is subjected to substrate coating, the substrate is coated with the spacing layer. Even if defective products appear in the subsequent substrate coating procedure, the coated film does not need to be removed in a chemical mode, chemical waste liquid is avoided, the substrate and the coating film are directly separated by directly removing the spacing layer, and the problem that the coating film is not clean is effectively avoided. And moreover, the newly added spacing layer can also avoid the situation that coating particles are sputtered into the inner layer of the substrate in the substrate coating process, and the situation that the thickness of the substrate is changed by subsequent surface treatment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor product preparation, and specifically provides a blank mask substrate, a preparation method and a regeneration method. Background Art

[0002] A photomask is a pattern transfer tool or master used in the microelectronics manufacturing process. It carries intellectual property information, including graphic designs and process technologies. Existing photomask production and preparation processes are typically divided into upstream and downstream stages. The upstream stage produces complete, blank photomasks without any information, while the downstream stage directly performs photolithography of the information pattern onto the blank photomask.

[0003] The production quality of upstream blank photomask substrates directly impacts the yield rate of subsequent photomask products. Currently, the primary production process for blank photomask substrates is as follows: incoming material inspection, substrate cleaning, substrate coating, substrate coating, and substrate inspection. Due to process limitations, process failures (NGs) (defective products that occur during the production process) cannot be completely avoided. When NGs occur, particularly after the substrate coating process, chemical stripping is required to restore the defective product to its original state for re-production. However, in practice, it is very common for the stripping process to be incomplete or for the coating to splash onto the inner layers of the substrate. Consequently, the defective substrates must undergo surface treatment (grinding, polishing, cleaning, and inspection and measurement) before they can be reused.

[0004] However, after these surface treatments, the thickness of the substrate may change. Once it is found to exceed the usable specifications, the substrate will no longer be worth reworking, causing serious waste and directly affecting the factory's production costs. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a blank photomask substrate that can be easily recycled, a preparation method, and a recycling method.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a blank mask substrate comprises the following steps: S1, incoming material inspection, inspecting substrate surface defects; S2, substrate cleaning, acid and alkali cleaning of substrates with qualified surfaces; S3, spacer layer coating, coating a high-transmittance spacer layer on the cleaned substrate surface; S4, substrate coating, sequentially sputtering different optical film layers on the spacer layer; S5, substrate coating, coating a photoresist layer after coating is completed; S6, substrate inspection and measurement, performing standardized inspection on the finished product.

[0008] In this solution, before the raw substrate is coated with a substrate, a spacer layer is first coated on the substrate. Even if defective products are produced in the subsequent substrate coating process, there is no need to chemically remove the coated film to avoid the generation of chemical waste liquid. Instead, the substrate and the coating are directly separated by removing the spacer layer, effectively avoiding the problem of unclean coating. The newly added spacer layer can also prevent the coating particles from sputtering into the inner layer of the substrate during the substrate coating process, reducing the situation where the subsequent surface treatment changes the thickness of the substrate.

[0009] When coating the spacer layer, it is necessary to ensure that the spacer layer is flat and has uniform thickness to ensure that the refractive index of the subsequent mask substrate is qualified. For this reason, in step S3, for small-sized substrates, the spacer layer is coated using the Spin coating method, and for large-sized substrates, the spacer layer is coated using the Slit coating method.

[0010] In this solution, substrates with a size of 700mm*800mm or less are generally considered small-sized substrates. Since small-sized substrates have a small area, spin coating is used, which has high precision and low cost (by rotating the substrate, centrifugal force is used to achieve uniform spreading of the liquid material). Substrates with a size of 700mm*800mm or more are considered large-sized substrates. Due to the large area of large-sized substrates, it is difficult to ensure that the entire surface can be coated evenly and flatly using the spin coating method. Therefore, slit coating is used, which increases the cost but can effectively achieve high-precision coating. (The liquid material is evenly coated on the substrate surface through a slit die and formed into a stable film through drying or curing.)

[0011] Preferably, the spacer layer is an amorphous fluorine-containing polymer material having a permeability greater than that of the substrate.

[0012] Preferably, the coating thickness of the spacer layer is estimated in advance according to the size of the substrate and the use requirements. The calculation formula for the estimated thickness of the spacer layer includes: D = λ / 4n

[0013] Where D is the estimated thickness of the spacer layer, λ is the wavelength of the light source incident on the spacer layer, and n is the refractive index of the spacer layer.

[0014] In this solution, since the high-transmittance spacer film is between the substrate and the optical film layer, the change in the overall thickness will affect the reflectivity of the complete blank substrate. This formula can be used to estimate the estimated thickness of the spacer layer, so that the thickness of each layer of film during the substrate coating process can be conveniently determined based on the estimated thickness to ensure the reflectivity requirements of the blank substrate.

[0015] A method for regenerating a mask substrate, based on a blank mask substrate prepared by the above-mentioned blank mask substrate preparation method, includes the following steps: St1, high-temperature treatment of the substrate to degrade and decompose the spacer layer; St2, solvent immersion of the substrate after high-temperature treatment; St3, hot water immersion of the substrate after solvent immersion; St4, rinsing the substrate surface with a water gun; St5, thickness inspection.

[0016] In this solution, since the blank mask substrate additionally includes a spacer layer, the spacer layer is an amorphous fluoropolymer material. Regardless of whether it is the recycling of defective products or the recycling of finished blank substrates, the spacer layer can be directly removed through this method. Without affecting the substrate, the substrate and the optical film layer can be directly separated, allowing the substrate to be reused without surface treatment, thereby reducing substrate waste.

[0017] Preferably, in step St1, the high temperature treatment includes standing for 0.5 to 1 hour in an environment of 300 to 400° C. By placing the substrate in a high temperature environment, the high-transmittance spacer layer is degraded and initially decomposed.

[0018] Preferably, in step St2, the solvent soaking includes soaking in a perfluorinated or nearly perfluorinated solvent for 1 to 2 hours.

[0019] In this solution, since the amorphous fluoropolymer material is only soluble in specific perfluorinated or near-perfluorinated solvents, the degraded spacer layer can be completely decomposed in the solvent, and the perfluorinated or near-perfluorinated solvent will not react with the substrate and will not affect the thickness of the substrate.

[0020] Preferably, in step St3, the hot water soaking comprises soaking in deionized water at 80 to 120° C. for 10 to 30 minutes. The hot deionized water soaking removes the solvent residue on the surface of the substrate.

[0021] Preferably, in step St3, the hot water soaking adopts an overflow process.

[0022] In this solution, the overflow process can prevent the deionized water from evaporating due to heating and the liquid level from dropping, ensuring uniform liquid coverage during the cleaning or processing process. It can also promptly remove dissolved or peeled impurities to prevent them from re-attaching to the substrate surface, thereby improving cleaning efficiency.

[0023] A blank photomask substrate is manufactured using the above-mentioned blank photomask substrate manufacturing method, comprising a substrate on which a spacer layer, a multilayer optical film layer and a photoresist layer are sequentially arranged from bottom to top.

[0024] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0025] 1. The blank substrate preparation method of the present invention differs from conventional methods in that a spacer layer is applied to the raw substrate before coating. Even if defective products are subsequently produced during the coating process, there is no need to chemically remove the coated film, thus avoiding the generation of chemical waste. Instead, the spacer layer is directly removed to separate the substrate and the coated film, effectively preventing the problem of unclean coating. Furthermore, the added spacer layer prevents particles from the coating from sputtering into the inner layers of the substrate during the coating process, minimizing the risk of subsequent surface treatment altering the substrate thickness.

[0026] 2. The blank substrate prepared by the method provided by the present invention additionally includes a spacer layer, which is an amorphous fluorine-containing polymer material. Whether it is the recycling of defective products or the recycling of finished blank substrates, the spacer layer can be directly removed by this method, and the substrate and the optical film layer can be directly separated without affecting the substrate, so that the substrate can be reused without surface treatment, thereby reducing substrate waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an undue limitation of the present invention. Obviously, the drawings described below are only some embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive effort. In the accompanying drawings:

[0028] Figure 1 It is a process flow chart of the preparation of the present invention;

[0029] Figure 2 It is a process flow chart of regeneration of the present invention;

[0030] Figure 3 Schematic diagram of a blank substrate of the present invention.

[0031] In the above drawings, the corresponding reference numerals are as follows:

[0032] 1-blank mask substrate, 11-substrate, 12-spacer layer, 13-optical film layer, 14-photoresist layer.

[0033] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0034] In conjunction with the accompanying drawings, the technical solution of the present invention is clearly and completely described through the specific implementation methods of the embodiments of the present invention.

[0035] Example 1:

[0036] A method for preparing a blank photomask substrate, such as Figure 1 As shown, the process includes the following steps: S1, incoming material inspection, inspecting substrate surface defects; S2, substrate cleaning, performing acid and alkali cleaning on substrates with qualified surfaces; S3, spacer layer coating, coating a high-transmittance spacer layer on the cleaned substrate surface; S4, substrate coating, sputtering optical film layers on the spacer layer in sequence; S5, substrate coating, coating a photoresist layer after coating is completed; S6, substrate inspection and measurement, performing standardized inspection on the finished product.

[0037] Specifically, in step S1, it is necessary to use manual or automated equipment to check whether the surface and edge of the raw material substrate have surface defects, scratches, etc. After the raw material substrate passes the inspection, it enters step S2, and the film-forming surface of the raw material substrate is acid-alkali cleaned to meet the coating requirements. In step S3, it is necessary to ensure that the spacer layer is flat and the thickness is uniform. The flatness of the spacer layer is less than 1% to ensure that the refractive index R of the subsequent finished blank mask substrate is qualified. For this reason, in step S3, substrates below 700mm*800mm are small-sized substrates. Small-sized substrates have a small area and are coated with spin coating. By rotating the substrate, centrifugal force is used to achieve uniform spreading of the liquid material, which has high precision and low cost. For substrates greater than or equal to 700mm*800mm, they are large-sized substrates. Due to the large area of large-sized substrates, it is difficult to ensure that the entire surface can be coated evenly and flatly using the spin coating method. Therefore, slit coating is used to evenly coat the liquid material on the surface of the substrate through a slit die head, and a stable film is formed by drying or curing. Although the cost is increased, it can effectively achieve high-precision coating. After the spacer layer is applied, step S4 is performed, where the substrate is coated using DC reactive sputtering to deposit different chromium films onto the substrate. The film thickness varies depending on customer requirements. Next, step S5 involves applying the photoresist layer. The photoresist layer is applied in the same manner as the spacer layer in step S3, also ensuring a flatness of less than 1%. Finally, step S6 inspects the finished blank photomask substrate to ensure that its refractive index meets the requirements.

[0038] It should be noted that in step S3, the spacer layer uses an amorphous fluoropolymer material, and it is necessary to ensure that the transmittance is greater than the transmittance of the substrate, and its transmittance needs to be greater than 95%, and the temperature resistance is not less than 200°C. It is preferred to use Teflon AF directly. And because the high-transmittance spacer film is between the substrate and the optical film layer, the change in overall thickness will affect the reflectivity of the complete blank substrate, so the coating thickness of the spacer layer is estimated in advance according to the size of the substrate and the use requirements. The estimated thickness of the spacer layer is calculated by the formula D=λ / 4n, where D is the estimated thickness of the spacer layer, λ is the wavelength of the light source incident on the spacer layer, and n is the refractive index of the spacer layer. Generally, the thickness of the spacer layer is between 0.03um and 1um. If it is too thin, the flatness cannot be guaranteed. If it is too thick, the cost increases and the coating difficulty increases. Therefore, the thickness of the spacer layer is preferably between 0.05um and 0.5um. After the spacer layer is established, the properties of the subsequent film layers must be adjusted in sequence, that is, the thickness, reaction gas composition, etc. must be adjusted to meet the final product specifications. By estimating the thickness of the spacer layer, the thickness of each layer of film during the substrate coating process can be conveniently determined based on the estimated thickness to ensure the reflectivity requirement of the blank substrate.

[0039] Taking a CrN / Cr / CrO multilayer photomask as an example, the light source wavelength is 365nm, and the refractive index n of the Teflon AF material used in the spacer layer is 1.34-1.35 (taking the middle value of 1.345). The calculated thickness of the spacer layer to be applied in step S3 is 365 / (4*1.345) = 67.84nm = 0.06784um, which meets the required thickness range. However, this thickness is only a theoretical value, and actual coating should be based on this thickness, but there will be errors. Therefore, the properties of subsequent optical film layers and the final stacked optical film layer values need to be adjusted individually.

[0040] Specifically, the CrN light-shielding optical film, the Cr light-shielding optical film, and the CrO anti-reflective optical film are sputtered sequentially. These optical film layers can be sputtered using either a DC vacuum sputtering system or an RF sputtering system. Using inert Ar as the primary sputtering gas, the reaction gas flow rate is adjusted to control the atomic percentage of the optical film layer, adjust film thickness, reflectivity, optical density (OD), and other optical parameters. This ensures that the stacked mask substrate has a reflectivity (R) between 11.5% and 12.5% and an optical density (OD) of 3.0±1.

[0041] It's important to note that if the measured data for the final film stack doesn't meet product specifications, the reaction gas flow rates for each layer must be adjusted. This adjustment will alter the resulting film thickness and atomic ratio. This allows for adjustments to be made to optical parameters to ensure that reflectivity, optical density (OD), and other parameters meet requirements at specific wavelengths.

[0042] In this embodiment, a spacer layer is first coated on the raw substrate before the substrate is coated. Even if defective products are produced in the subsequent substrate coating process, there is no need to chemically remove the coated film to avoid the generation of chemical waste liquid. Instead, the substrate and the coated film are directly separated by removing the spacer layer, effectively avoiding the problem of unclean coating. The newly added spacer layer can also prevent the coating particles from sputtering into the inner layer of the substrate during the substrate coating process, reducing the situation where the thickness of the substrate is changed by subsequent surface treatment.

[0043] Example 2:

[0044] A photomask substrate regeneration method, such as Figure 2 As shown, a blank mask substrate prepared by a blank mask substrate preparation method provided in Example 1 includes the following steps: St1, performing high-temperature treatment on the substrate to degrade and decompose the spacer layer; St2, soaking the substrate after high-temperature treatment in a solvent; St3, soaking the substrate in hot water after solvent soaking; St4, rinsing the surface of the substrate with a water gun; St5, thickness inspection.

[0045] Specifically, in step St1, the high-temperature treatment includes standing at 300-400°C for 0.5-1h. The substrate is placed in a high-temperature environment by soaking or in an oven to degrade and preliminarily decompose the high-transmittance spacer layer. In step St2, the solvent soaking includes soaking in a perfluorinated or near-perfluorinated solvent for 1-2h. Since the amorphous fluoropolymer material will only dissolve in a specific perfluorinated or near-perfluorinated solvent, the degraded spacer layer can be completely decomposed in the solvent, and the perfluorinated or near-perfluorinated solvent will not react with the substrate and will not affect the thickness of the substrate. In step St3, the hot water soaking includes soaking in deionized water at 80-120°C for 10-30min. Soak in hot deionized water to remove the solvent residue on the surface of the substrate. In step St4, high-purity deionized water is used in combination with spraying to rinse the particle impurities on the substrate. In the final step St5, the substrate is dried and then inspected manually or by machine. When the basic thickness and surface flatness meet the requirements, it can be used again as a raw material substrate to prepare a blank mask substrate.

[0046] It should be noted that in step St3, the hot water immersion process adopts an overflow process. The overflow process can prevent the deionized water from evaporating due to heating and the liquid level from dropping, ensuring uniform liquid coverage during the cleaning or treatment process. It can also promptly remove dissolved or peeled impurities to prevent them from re-attaching to the substrate surface, thereby improving cleaning efficiency.

[0047] In this embodiment, since the blank mask substrate additionally includes a spacer layer, the spacer layer is an amorphous fluoropolymer material. Regardless of whether it is the regeneration of defective products or the regeneration of finished blank substrates, the spacer layer is directly removed by this method, and the substrate and the optical film layer are directly separated without affecting the substrate, so that the substrate can be reused without surface treatment, thereby reducing substrate waste.

[0048] Example 3:

[0049] A blank photomask substrate 1 is made using the blank photomask substrate preparation method described in Example 1, such as Figure 3 As shown, it includes a substrate 11, on which a spacer layer 12, a multilayer optical film layer 13 and a light-blocking layer 14 are sequentially arranged from bottom to top.

[0050] The performance of the blank mask substrate 1 in this embodiment is no different from that of the traditional blank mask substrate, but subsequent recycling and regeneration can directly recycle the substrate 11 quickly, efficiently, without damage, and with low pollution through the method of Example 2, greatly improving the economic benefits of the enterprise.

[0051] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing a blank mask substrate, characterized in that: Including steps: S1. Incoming material inspection, inspection of substrate surface defects; S2, substrate cleaning, acid and alkali cleaning of substrates with qualified surfaces; S3, spacer layer coating, coating a high-penetration spacer layer on the cleaned substrate surface; S4, substrate coating, sputtering different optical film layers on the spacer layer in sequence; S5, coating the substrate, and applying a photoresist layer after the coating is completed; S6. Inspection and measurement of substrates, and standardized inspection of finished products.

2. The method for preparing a blank photomask substrate according to claim 1, wherein: In the step S3, for a small-sized substrate, the spacer layer is coated by a spin coating method, and for a large-sized substrate, the spacer layer is coated by a slit coating method.

3. The method for preparing a blank photomask substrate according to claim 2, wherein: The spacer layer is made of an amorphous fluorine-containing polymer material having a greater permeability than that of the substrate.

4. The method for preparing a blank photomask substrate according to claim 3, wherein: The coating thickness of the spacer layer is estimated in advance according to the size of the substrate and the use requirements. The calculation formula for the estimated thickness of the spacer layer includes: D = λ / 4n Where D is the estimated thickness of the spacer layer, λ is the wavelength of the light source incident on the spacer layer, and n is the refractive index of the spacer layer.

5. A method for regenerating a photomask substrate, comprising: preparing a blank photomask substrate according to any one of claims 1 to 4; wherein: Including steps: St1, subjecting the substrate to high temperature treatment to degrade and decompose the spacer layer; St2, soaking the substrate after high temperature treatment in a solvent; St3, soaking the substrate in hot water after solvent soaking; St4, using a water gun to rinse the surface of the substrate; St5, thickness inspection.

6. A photomask substrate regeneration method according to claim 5, characterized in that: In the step St1, the high temperature treatment includes standing at 300-400° C. for 0.5-1 hour.

7. The photomask substrate regeneration method according to claim 5, wherein: In the step St2, the solvent soaking includes soaking in a perfluorinated or nearly perfluorinated solvent for 1 to 2 hours.

8. The photomask substrate regeneration method according to claim 5, wherein: In the step St3, the hot water soaking includes soaking in deionized water at 80 to 120° C. for 10 to 30 minutes.

9. The photomask substrate regeneration method according to claim 8, characterized in that: In step St3, the hot water soaking adopts an overflow process.

10. A blank mask substrate, characterized in that: The blank mask substrate is made by the method for preparing a blank mask substrate according to any one of claims 1 to 4, comprising a substrate on which a spacer layer, a multilayer optical film layer and a photoresist layer are sequentially arranged from bottom to top.

Images