A mask preparation method and mask structure

Abstract

The present invention provides a novel mask structure and preparation method. A quartz glass substrate is provided. At least two laser beams are injected into the interior of the glass substrate from different angles and intersect to form a laser interference point, so that crystallization occurs at the laser interference point to obtain a designed shape with a target light transmittance. The crystal body located inside the quartz glass substrate and having the target light transmittance and the designed shape is obtained by cooling. The novel mask has a simple preparation process and is easy to clean and maintain. The designed shape is completely sealed and is not easily deformed during use, resulting in no change in the image of the exposed pattern after it passes through a protective film. The designed shape is formed by glass transforming into crystal, which has a lower thermal expansion coefficient and effectively reduces the thermal effect of the mask.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a mask preparation method and a mask structure. Background Art

[0002] The traditional mask structure is an aluminum alloy frame mounted on the side of the glass substrate where the image is engraved. The aluminum alloy frame is used to cover the protective film. All exposed areas of the mask must be covered by the protective film. Figure 1 As shown. The most important function of the protective film is to prevent dust from falling on the side of the mask with patterns, and to prevent contamination particles from imaging on the wafer surface. The process flow of traditional mask preparation is: first, a uniform Cr / CrOx film is deposited on the substrate using physical methods, and then photoresist or electronic glue is spin-coated, and the pattern is generated using a light beam or electron beam exposure process, and finally an etching process is performed, such as Figure 2 shown.

[0003] Traditional mask preparation involves a complex process (including physical deposition, electron beam exposure, development, etching, and cleaning). The protective film is typically made of a polymer material. This can become susceptible to damage after prolonged use or purging. Furthermore, the protective film can "loosen," bending downward under the influence of gravity, causing the exposed pattern to be magnified after it passes through the protective film. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a mask preparation method and a mask structure to solve the problem that the traditional mask preparation process in the prior art is complicated, and the protective film will be deformed due to damage and relaxation after long-term use or blowing, resulting in the exposure pattern being magnified after passing through the protective film.

[0005] To achieve the above-mentioned and other related objectives, the present invention provides a method for preparing a mask, the method at least comprising:

[0006] Step 1: providing a quartz glass substrate;

[0007] Step 2: irradiating a quartz glass substrate with at least two laser beams from different angles, intersecting within the quartz glass substrate to form a laser interference point, causing recrystallization at the laser interference point, thereby obtaining a designed shape having a target light transmittance, the designed shape including thickness and line width;

[0008] Step 3: Cooling to obtain a crystal body located inside the quartz glass substrate, having the target light transmittance and the designed shape.

[0009] Optionally, the frequencies and amplitudes of the at least two laser beams in step 2 are the same.

[0010] Optionally, the position of the laser interference point in step 2 is controlled by a computer.

[0011] Optionally, the laser interference point in step 2 is formed at a position approximately 1 / 2 thickness of the quartz glass substrate, so that the designed shape is formed at a position approximately 1 / 2 thickness of the quartz glass substrate.

[0012] Optionally, the designed shape in step 2 is formed in one step, and the graphic line width of the designed shape during the one-step forming is controlled by the size of the light spot at the laser interference point; if the designed shape is too complex to be formed in one step, multiple forming is adopted.

[0013] Optionally, the size of the light spot is controlled by the power of the at least two laser beams.

[0014] Optionally, the power needs to satisfy the requirement that a single laser beam maintains a light energy form when passing through the quartz glass substrate without generating excess energy, so that the energy is converted into internal energy at the interference point and melts the quartz glass.

[0015] Optionally, the target light transmittance is determined by the thickness d of the designed shape and the crystalline structure obtained by different cooling methods.

[0016] Optionally, the target light transmittance ranges from 4% to 25%.

[0017] Optionally, the thickness of the designed shape is d = N*λ / [2*(n2-n1), so that the light passing through the crystal has a phase increase of 180°, where N is an odd number greater than or equal to 1, preferably 1, λ is the exposure machine wavelength, n1 is the refractive index of the quartz glass, and n2 is the refractive index of the crystal.

[0018] Optionally, the cooling method is from room temperature to extreme cold, so that the structure of the crystal changes, and the structure of the crystal is at least one of phosphotyrite, cristobalite, α-quartz, β-quartz, coesite, and steven.

[0019] A mask structure, comprising at least:

[0020] Quartz glass substrate;

[0021] The crystal body is arranged inside the quartz glass substrate, and is formed by recrystallization and cooling through laser interference. The crystal body has a target light transmittance and a designed shape, and the designed shape includes thickness and line width.

[0022] Preferably, the plane shape of the designed shape is formed by the continuous line width, wherein the plane is parallel to the incident surface or the exit surface of the quartz glass substrate.

[0023] Preferably, the crystal body is disposed at a position approximately 1 / 2 of the thickness of the quartz glass substrate.

[0024] Preferably, the target light transmittance ranges from 4% to 25%.

[0025] Preferably, the thickness of the crystal body is d=N*λ / [2*(n2-n1), where N is an odd number greater than or equal to 1, preferably 1, λ is the wavelength of the exposure machine, n1 is the refractive index of the quartz glass, and n2 is the refractive index of the crystal body.

[0026] Preferably, the structure of the crystal is at least one of phosphotyrite, cristobalite, α-quartz, β-quartz, coesite, and steven.

[0027] As described above, the mask preparation method and mask structure of the present invention have the following beneficial effects:

[0028] 1. The new mask preparation process is simple and easy to clean and maintain.

[0029] 2. The design shape is completely sealed and is not easily deformed during use, resulting in no change in the imaging of the exposed pattern after it passes through the protective film.

[0030] 3. The design shape is that glass is transformed into crystal, with a lower thermal expansion coefficient, which effectively reduces the thermal effect of the mask. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Shown is a schematic diagram of a conventional mask structure in the prior art;

[0032] Figure 2 Shown is a schematic diagram of the process flow of traditional mask preparation in the prior art;

[0033] Figure 3 Shown is a schematic diagram of the process flow of preparing the novel mask of the present invention;

[0034] Figure 4 Shown is a schematic top view of a novel mask structure of the present invention;

[0035] Figure 5 Shown is a schematic cross-sectional view of a novel mask structure of the present invention;

[0036] Figure 6 Schematic diagram showing comparison of the imaging of the SiO2 crystals in the mask of the present invention with a phase shift of 0 degree and 180 degrees;

[0037] Figure 7 Shown is a schematic diagram of the mask production process of the present invention.

[0038] Among them, 1-quartz glass substrate, 2-crystal. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] See also Figure 3 The present invention provides a mask preparation method, the method at least comprising:

[0041] Step 1: Provide a quartz glass substrate 1, wherein the refractive index n1 of the quartz glass substrate 1 is determined by factors such as different materials. The size of the high-quality quartz glass substrate 1 can be adjusted according to the hardware of the exposure machine;

[0042] Step 2: Using at least two laser beams to penetrate the interior of the glass substrate from different angles and intersect to form a laser interference point, so that crystallization at the laser interference point obtains a designed shape with a target light transmittance;

[0043] Furthermore, in step 2, a computer controls two laser beams with the same frequency and amplitude. The laser device is turned on, and the two laser beams of the same frequency and amplitude are directed at different angles into the quartz glass substrate 1, causing them to focus at a single point within the substrate. As the two laser beams interfere at the intersection, their energy is converted from optical energy to internal energy, releasing a large amount of heat, causing the glass to melt and recrystallize. The computer controls the spatial position of the interference point within the glass, with the interference point positioned at a height H1 from the upper surface of the quartz glass substrate 1 and a height H2 from the lower surface. The large number of microcrystals are arranged into the desired pattern.

[0044] Furthermore, the position of the designed shape within the quartz glass is controlled by a computer. The farther away from the surface, the larger the surface contamination particle size that can be tolerated, and the corresponding preparation difficulty increases. It is recommended that the values ​​of H1 and H2 be the same, approximately equal to 1 / 2 of the thickness of the quartz glass substrate 1.

[0045] Further, see Figure 4 The design shape in step 2 is formed in one go. The line width of the design shape during one go is controlled by the size of the light spot at the laser interference point. The size of the light spot here can be adjusted by adjusting the laser power, etc., which can improve the efficiency during forming. The power needs to meet the requirement that a single laser beam maintains the form of light energy when passing through the quartz glass substrate and does not generate excess energy, so that it is converted into internal energy at the interference point and melts the quartz glass. If the design shape is too complex to be formed in one go, multiple forming processes are used.

[0046] Furthermore, the target transmittance is determined by the thickness d of the designed shape and the structure of the crystal 2 obtained by different cooling methods. The target transmittance ranges from 4% to 25%. Too high a transmittance will result in exposure of the "dark area" photoresist.

[0047] Furthermore, the thickness d of the designed shape can be adjusted during molding by controlling the laser power and irradiation time.

[0048] Further, see Figure 5 The thickness of the designed shape is d = N*λ / [2*(n2-n1), so that the light passing through crystal 2 has a 180° phase increase, where N is an odd number (N=1, 3, 5...), λ is the wavelength of the exposure machine, n1 is the refractive index of quartz glass, and n2 is the refractive index of crystal 2. This makes the light intensity change in the edge area of ​​the pattern steeper, thereby obtaining higher pattern resolution.

[0049] Furthermore, the thickness d of the designed shape (d = N*λ / [2*(n2-n1)]) is designed. The larger the N value, the thicker the corresponding thickness, the greater the laser power consumption required during production, and the higher the cost. It is recommended to use N = 1.

[0050] Step three: cooling to obtain a crystal body 2 located inside the quartz glass substrate 1 with target transmittance and designed shape. The crystal body 2 is SiO2 crystal. Compared with the mask of traditional structure, the designed shape is completely sealed.

[0051] Furthermore, the cooling method is from room temperature to extremely cold, so that the structure of the crystal 2 changes, and the structure of the crystal 2 is at least one of phosphotyrite, cristobalite, α-quartz, β-quartz, coesite, and stochastic.

[0052] A mask structure, the mask structure at least comprising:

[0053] Quartz glass substrate 1;

[0054] The crystal body 2 is provided inside the quartz glass substrate and is formed by recrystallization and cooling by laser interference. The crystal body 2 has a target light transmittance and a designed shape, and the designed shape includes thickness and line width.

[0055] Furthermore, the plane shape of the designed shape is formed by a continuous line width, wherein the plane is parallel to the incident surface or the exit surface of the quartz glass substrate 1 .

[0056] Further, the target light transmittance ranges from 4% to 25%.

[0057] Furthermore, the thickness of the crystal 2 is d=N*λ / [2*(n2-n1), where N is greater than or equal to one, preferably N is 1, λ is the exposure machine wavelength, n1 is the refractive index of quartz glass, and n2 is the refractive index of the crystal 2.

[0058] Furthermore, the structure of the crystal 2 is at least one of phosphotyrite, cristobalite, α-quartz, β-quartz, coesite, and steven.

[0059] The mask structure can be manufactured through the above steps.

[0060] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0061] In summary, the present invention offers a simple mask production process, easy cleaning and maintenance, a completely sealed design, and resistance to deformation during use, resulting in no change in the image of the exposed pattern after it passes through the protective film. Furthermore, the design allows for a glass-to-crystal transition, resulting in a lower coefficient of thermal expansion, effectively reducing thermal effects on the mask. Therefore, the present invention effectively overcomes the shortcomings of existing technologies and possesses high industrial value.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A mask preparation method, characterized in that: The method at least comprises: Step 1: providing a quartz glass substrate; Step 2: irradiating a quartz glass substrate with at least two laser beams from different angles, intersecting within the quartz glass substrate to form a laser interference point, causing recrystallization at the laser interference point, thereby obtaining a designed shape having a target light transmittance, the designed shape including thickness and line width; Step 3: Cooling to obtain a crystal body located inside the quartz glass substrate, having the target light transmittance and the designed shape.

2. The mask preparation method according to claim 1, wherein: The frequencies of the at least two laser beams in step 2 are the same; the amplitudes of the at least two laser beams are the same.

3. The mask preparation method according to claim 1, wherein: The position of the laser interference point in step 2 is controlled by a computer.

4. The mask preparation method according to claim 1, wherein: The laser interference point in step 2 is formed at a position approximately 1 / 2 of the thickness of the quartz glass substrate, so that the designed shape is formed at a position approximately 1 / 2 of the thickness of the quartz glass substrate.

5. The mask preparation method according to claim 1, wherein: The designed shape in step 2 is formed in one step, and the graphic line width of the designed shape is controlled by the spot size of the laser interference point.

6. The mask preparation method according to claim 1, wherein: The design shape in step 2 is formed multiple times.

7. The mask preparation method according to claim 5, wherein: The size of the light spot is controlled by the power of the at least two laser beams.

8. The mask preparation method according to claim 7, wherein: The power needs to satisfy the requirement that a single laser beam maintains the form of light energy when passing through the quartz glass substrate without generating excess energy, so that it is converted into internal energy at the interference point and melts the quartz glass.

9. The mask preparation method according to claim 1, wherein: The target light transmittance in step 2 is determined by the thickness d of the designed shape and the structure of the crystal.

10. The mask preparation method according to claim 1, wherein: The target transmittance in step 2 ranges from 4% to 25%.

11. The mask preparation method according to claim 1, wherein: The structure of the crystal in step 3 is obtained by different cooling methods.

12. The mask preparation method according to claim 11, wherein: The cooling method sets different cooling temperatures so that the structure of the crystal changes.

13. The mask preparation method according to claim 1, wherein: The structure of the crystal in step 3 is at least one of phosphotyrite, cristobalite, α-quartz, β-quartz, coesite, and steven.

14. The mask preparation method according to claim 9, wherein: The thickness of the designed shape is d = N*λ / [2*(n2-n1), so that the light passing through the crystal body has a 180° phase increase, where N is an odd number greater than or equal to 1, λ is the wavelength of the exposure machine, n1 is the refractive index of the quartz glass, and n2 is the refractive index of the crystal body.

15. A mask structure, characterized in that: The mask structure at least comprises: Quartz glass substrate; A crystal body is provided inside the quartz glass substrate. The crystal body is formed by recrystallizing and cooling the material of the quartz glass substrate through laser interference. The crystal body has a target transmittance and a designed shape, and the designed shape includes thickness and line width.

16. The mask structure according to claim 15, wherein: The crystal body is arranged at a position approximately 1 / 2 of the thickness of the quartz glass substrate.

17. The mask structure according to claim 15, wherein: The target light transmittance ranges from 4% to 25%.

18. The mask structure according to claim 15, wherein: The plane shape of the designed shape is formed by the continuous line width, wherein the plane is parallel to the incident surface or the exit surface of the quartz glass substrate.

19. The mask structure according to claim 15, wherein: The thickness of the crystal body is d=N*λ / [2*(n2-n1), where N is an odd number greater than or equal to one, λ is the wavelength of the exposure machine, n1 is the refractive index of the quartz glass, and n2 is the refractive index of the crystal body.

20. The mask structure according to claim 15, wherein: The structure of the crystal is at least one of phosphotyrite, cristobalite, α-quartz, β-quartz, coesite, and stochastic.

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