CN117484380A

CN117484380A - Polishing method and polishing system for mask substrate

Info

Publication number: CN117484380A
Application number: CN202311756751.1A
Authority: CN
Inventors: 任雨萌; 季明华; 高世栋
Original assignee: Shanghai Chuanxin Semiconductor Co ltd
Current assignee: Shanghai Chuanxin Semiconductor Co ltd
Priority date: 2023-12-19
Filing date: 2023-12-19
Publication date: 2024-02-02

Abstract

The invention provides a polishing method and a polishing system for a mask substrate. The polishing method of the mask substrate adopts polishing liquid without abrasive, so that the damage of the abrasive to the mask substrate is avoided. And before polishing, a repair layer is formed on the surface of the mask substrate so as to fill the rugged surface of the mask substrate by using the repair layer, and only the surface of the repair layer is required to be polished in the subsequent polishing process. The repair layer is made of amorphous silicon, has good light transmittance, does not influence the efficacy of the mask, and the cationic polymer in the polishing solution can be combined with molecules on the surface of the amorphous silicon so as to reduce the stability of the molecular structure on the surface of the amorphous silicon, thereby being beneficial to polishing the amorphous silicon in a non-abrasive state. And the polishing method also uses micro-nano bubble solution in the polishing process so as to utilize micro-nano bubbles to impact the surface of the amorphous silicon, thereby further improving the planarization speed and effect.

Description

Polishing method and polishing system for mask substrate

Technical Field

The invention relates to the technical field of integrated circuit preparation, in particular to a polishing method and a polishing system of a mask substrate.

Background

A Mask is one of the indispensable precision components in micro-nano processing technology, and is composed of a patterned light shielding film and a Mask substrate to transfer a pattern onto a wafer through a photolithography process. Wherein the light transmittance and flatness of the mask substrate have an important influence on the overall performance of the reticle. In this regard, the prior art often uses synthetic quartz glass as the mask substrate to meet the requirement of higher light transmittance of the mask. And polishing the surface of the mask substrate using a chemical mechanical polishing process (Chemical Mechanical Polishing, CMP) to improve the flatness of the mask substrate. However, in the mechanical polishing process, abrasive grains are mixed in the polishing liquid for polishing, and these abrasive grains easily damage the surface of the mask substrate. As shown in fig. 1, although the size of the abrasive particles G1 is small to the nanometer level, in view of the dispersibility problem of the abrasive particles G1, the abrasive particles G1 in the polishing liquid are agglomerated into large-particle abrasives G2, and these large-particle abrasives G2 are extremely liable to cause defects such as scratches S, pits P, and the like on the surface of the mask substrate 10. In addition, in the mechanical polishing process, in order to secure the polishing effect, the polishing head applies a certain polishing pressure toward the surface of the mask substrate 10, which tends to cause a part of the abrasive grains G1 to be embedded in the surface of the mask substrate 10, affecting the flatness of the mask substrate 10. In this regard, in the prior art, during the subsequent cleaning of the mask substrate 10, a corrosive component is added to the cleaning solution to remove the embedded abrasive particles G1. This not only damages the surface of the mask substrate 10, but also introduces new defects that exacerbate the roughness of the surface of the mask substrate 10.

Therefore, a new polishing process is needed to solve the above technical problems.

Disclosure of Invention

The invention aims to provide a polishing method and a polishing system for a mask substrate, which are used for solving the problems of avoiding damage of an abrasive in a polishing solution to the mask substrate and improving at least one of polishing effect and polishing efficiency.

In order to solve the above technical problems, the present invention provides a polishing method of a mask substrate, including:

providing a mask substrate;

forming a repair layer on the surface of the mask substrate;

performing a chemical mechanical polishing process on the repair layer by adopting polishing solution without abrasive and micro-nano bubble solution; wherein the polishing solution comprises a cationic polymer.

Optionally, in the polishing method of a mask substrate, the cationic polymer includes polydimethyldiallylammonium chloride, polyethylenimine and/or polyallylamine.

Optionally, in the polishing method of a mask substrate, the concentration of ammonium salt in the cationic polymer is less than or equal to 250ppm.

Optionally, in the polishing method of a mask substrate, the polishing solution further includes polyethylene glycol.

Optionally, in the polishing method of a mask substrate, the concentration of polyethylene glycol is less than or equal to 100ppm.

Optionally, in the polishing method of a mask substrate, the material of the repair layer includes amorphous silicon.

Optionally, in the polishing method of a mask substrate, the diameter of the micro-nano bubbles in the micro-nano bubble solution is less than or equal to 100nm.

Based on the same inventive concept, the present invention also provides a polishing system for a mask substrate, comprising: a film generation module, a mechanical polishing module and a bubble supply module; wherein,

the film generation module is used for forming a repair layer on the surface of the mask substrate;

the mechanical polishing module is used for polishing the repair layer by adopting an abrasive-free polishing solution, and the polishing solution comprises a cationic polymer;

and the bubble supply module is used for mixing micro-nano bubble solution into the polishing solution in the process of polishing the repair layer.

Optionally, in the polishing system for a mask substrate, the mechanical polishing module includes a polishing table, a polishing pad, a polishing head, and a liquid supply; the mask substrate is positioned on the polishing pad and is accommodated in a limit groove of the polishing head; the liquid supply device is positioned at one side of the polishing table and is used for spraying the polishing liquid to the polishing pad.

Optionally, in the polishing system for a mask substrate, the bubble supply module includes a bubble generator and a showerhead; wherein the bubble generator is used for generating the micro-nano bubble solution; the spray head is communicated with the bubble generator and used for spraying the micro-nano bubble solution to the polishing pad so as to mix the micro-nano bubble solution with the polishing solution.

In summary, the present invention provides a polishing method and a polishing system for a mask substrate. Compared with the prior art, the polishing method of the mask substrate adopts the polishing solution without the abrasive to polish, thereby avoiding the damage of the abrasive to the mask substrate. And before polishing, forming a repair layer on the surface of the mask substrate so as to fill the rugged surface of the mask substrate by using the repair layer, wherein the surface of the repair layer is only required to be polished in the subsequent polishing process. The material of the repairing layer is amorphous silicon, the repairing layer has good light transmittance, the efficacy of the mask is not affected, and the cationic polymer in the polishing solution can be combined with molecules on the surface of the amorphous silicon, so that the stability of the molecular structure on the surface of the amorphous silicon is reduced, and the amorphous silicon is polished in a non-abrasive state. And the method also uses micro-nano bubble solution in the polishing process so as to utilize micro-nano bubbles to impact the surface of the amorphous silicon, thereby further improving the planarization speed and effect. Therefore, the polishing method provided by the invention effectively avoids the application defect of the abrasive, and improves the polishing efficiency and polishing effect.

Drawings

Those of ordinary skill in the art will appreciate that the figures are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

Fig. 1 is a schematic view of a prior art structure in which abrasive grains cause surface defects of a mask substrate.

Fig. 2 is a flow chart of a method of polishing a mask substrate in an embodiment of the invention.

Fig. 3 is a schematic view of a structure of a mask substrate in an embodiment of the present invention.

Fig. 4 is a schematic view of a structure of forming a repair layer on a mask substrate in an embodiment of the present invention.

Fig. 5 is a schematic view of the structure of the polishing repair layer in the embodiment of the present invention.

Fig. 6 is a schematic molecular diagram of the reaction of amorphous silicon with PDADMAC in an embodiment of the present invention.

Fig. 7 is a schematic diagram of the incorporation of nitrogen atoms into amorphous silicon in PDADMAC in an embodiment of the present invention.

FIG. 8 is a schematic molecular diagram of the reaction of amorphous silicon with PEG and PDADMAC in an embodiment of the invention.

Fig. 9 is a schematic structural view of a polished repair layer in an embodiment of the present invention.

Fig. 10 is a schematic diagram of a polishing system for a mask substrate in accordance with an embodiment of the present invention.

In the accompanying drawings:

10-masking a substrate;

a 20-mask substrate; 21-a repair layer;

30-polishing solution; 31-micro-nano bubble solution;

40-a polishing table; 41-a polishing pad; 42-polishing head; 43-liquid feeder;

50-bubble generator; 501-a gas supply reaction unit; 502-a liquid reaction unit; 51-a spray head;

s-scratching; p-pits; c-bulge; g1-abrasive particles; g2—large particle abrasive.

Detailed Description

The invention will be described in further detail with reference to the drawings and the specific embodiments thereof in order to make the objects, advantages and features of the invention more apparent. It should be noted that the drawings are in a very simplified form and are not drawn to scale, merely for convenience and clarity in aiding in the description of embodiments of the invention. Furthermore, the structures shown in the drawings are often part of actual structures. In particular, the drawings are shown with different emphasis instead being placed upon illustrating the various embodiments. It should be further understood that the terms "first," "second," "third," and the like in this specification are used merely for distinguishing between various components, elements, steps, etc. in the specification and not for indicating a logical or sequential relationship between the various components, elements, steps, etc., unless otherwise indicated.

Referring to fig. 2, the present embodiment provides a polishing method for a mask substrate, including:

step one S10: providing a mask substrate;

step two S20: forming a repair layer on the surface of the mask substrate;

step three S30: performing a chemical mechanical polishing process on the repair layer by adopting polishing solution without abrasive and micro-nano bubble solution; wherein the polishing solution comprises a cationic polymer.

It can be understood that the polishing method of the mask substrate provided in this embodiment uses the polishing solution without abrasive to polish, so as to avoid the damage of the abrasive to the mask substrate. And before polishing, forming a repair layer on the surface of the mask substrate so as to fill the rugged surface of the mask substrate by using the repair layer, wherein the surface of the repair layer is only required to be polished in the subsequent polishing process. Furthermore, the material of the repairing layer is amorphous silicon, the repairing layer has good light transmittance, the efficacy of the mask is not affected, and the cationic polymer in the polishing solution can be combined with molecules on the surface of the amorphous silicon, so that the stability of the molecular structure on the surface of the amorphous silicon is reduced, and the amorphous silicon is polished in a non-abrasive state. And mixing a micro-nano bubble solution into the polishing solution in the polishing process so as to impact the surface of the amorphous silicon by utilizing micro-nano bubbles, thereby effectively improving the planarization speed and effect. Based on the above, the polishing method of the mask substrate provided by the embodiment avoids the application defect of the abrasive, and improves the polishing efficiency and the polishing effect.

The polishing method of the mask substrate provided in this embodiment is specifically described below with reference to fig. 2 to 10.

Step one S10: referring to fig. 3, a mask substrate 20 is provided.

The mask substrate 20 is used as a bottom plate of a photolithography mask, and has better light transmittance. And is preferably: quartz glass substrates, borosilicate substrates, aluminum silicate substrates, silicon carbide substrates, and the like. Further, the mask substrate 20 may be a substrate obtained by slicing a raw material, a substrate recovered by a waste reticle, or a substrate which does not reach the standard after polishing. Based on this, the surface to be polished of the mask substrate 20 generally has defects such as scratches S, pits P, and/or protrusions C.

Step two S20: referring to fig. 3 and 4, a repair layer 21 is formed on the surface of the mask substrate 20.

In view of the material of the mask substrate 20, the conventional process needs to grind and polish the mask substrate 20 with a polishing solution containing an abrasive to improve the flatness of the mask substrate 20. However, the abrasive causes new defects to be formed on the surface of the mask substrate 20, and if the abrasive in the polishing liquid is removed, it is difficult to planarize the mask substrate 20 with stable structure although the new defects can be avoided. Therefore, in this embodiment, the repair layer 21 is formed on the surface of the mask substrate 20, and the repair layer 21 is made of amorphous silicon (amorphous silicon, a-Si). On the one hand, the repair layer 21 may fill and repair the scratch S, the pit P, or the crack on the surface of the mask substrate 20. On the other hand, although the surface of the repair layer 21 formed is uneven based on the unevenness of the surface of the mask substrate 20, the repair layer 21 is made of amorphous silicon, and the grinding and polishing of amorphous silicon are easier than the grinding and polishing of the mask substrate 20. The reason is that the amorphous silicon structure is randomly distributed, has no regular crystallization property, has a plurality of suspension bonds, and has good free cutting property. Therefore, amorphous silicon is easy to be modified by chemical reagents, and a smooth surface with better flatness can be obtained under the grinding and polishing without abrasive materials. In addition, the amorphous silicon has good transmittance in ultraviolet band, and has no adverse effect on the transmittance of a mask plate formed subsequently. Further, the specific forming method of the repair layer 21 is not limited in this embodiment, and may be an evaporation process, a sputtering process, a chemical vapor deposition process, or the like. And, the specific thickness of the repair layer 21 is not limited in this embodiment, and may be determined according to the thickness of the mask substrate 20 and the defect level. The thickness of the repair layer 21 is in the range of 50nm to 250nm, for example.

Preferably, before the repair layer 21 is formed on the surface of the mask substrate 20, the mask substrate 20 needs to be cleaned and dried to remove removable contaminant particles such as dust on the surface of the mask substrate 20, thereby ensuring better cleanliness of the surface of the mask substrate 20.

Step three S30: referring to fig. 5 to 9, a chemical mechanical polishing process is performed on the repair layer 21 using an abrasive-free polishing liquid 30 and a micro-nano bubble solution 31; wherein the polishing liquid 30 comprises a cationic polymer.

Specifically, the repair layer 21 is polished using a chemical mechanical polishing apparatus to planarize the surface of the repair layer 21. Wherein, the polishing liquid 30 does not contain an abrasive, so that the problem of surface defects caused by the abrasive can be avoided during the polishing process. To ensure that a better polishing effect is obtained without an abrasive, the polishing liquid 30 used in this embodiment contains a cationic polymer. It should be noted that, the cationic polymer has high cationic activity, and is easy to exchange with the amorphous silicon surface of the repair layer 21, so as to weaken the molecular connection of the amorphous silicon and reduce the structural stability thereof, thereby being beneficial to removing part of the repair layer 21 in the polishing process. In addition, the cationic polymer can be adsorbed on the polished surface to form a layer of protective film, so that the surface quality after polishing is improved. Preferably, the cationic polymer includes, but is not limited to, one or more of polydimethyldiallylammonium chloride (Poly dimethyl diallyl ammonium chloride, PDADMAC), polyethylenimine (PEI), polyallylamine (PAAM). And the molecular weight Mw of each cationic polymer ranges from 10000 to 200000.

Illustratively, as shown in fig. 6 and 7, the polishing liquid 30 is PDADMAC. Since the repair layer 21 is made of amorphous silicon, and the amorphous silicon is easily hydrogenated, the repair layer 21 includes a large number of si—h bonds and si—si bonds. While the OH "in the polishing liquid 30 attacks both Si-H bonds and Si-Si bonds, thereby forming Si-OH bonds and polarizing adjacent silicon bonds. And, the aqueous solution of PDADMAC consists of three high electronegativity ions, respectively: tetramethyl ammonium, chloride, and hydroxyl. Hydroxyl or chloride ions induce polarization between adjacent surface silicon atoms and subsequently bond with positively charged nitrogen atoms. When the high electronegativity nitrogen atoms and OH-/Cl-of the PDADMAC molecule are bonded to the silicon atoms on the surface of the repair layer 21, the bonding force of the adjacent Si-Si bonds is weaker than the bonding force between the polymer and the Si atoms, thereby facilitating removal during polishing and polishing of the repair layer 21. Further, the present embodiment is not limited to the specific concentration and ratio of each solution component in the polishing liquid 30. Preferably, the concentration of ammonium salt in PDADMAC is less than or equal to 250ppm.

Further, polyethylene glycol (Polyethylene glycol, PEG) is added to the polishing solution 30 without abrasive provided in this embodiment. As shown in fig. 8, PEG is a nonionic polymer with good chemical and thermal stability. During polishing, PEG may improve the roughness of the surface of the repair layer 21 by interacting with the surface. Specifically, PEG molecules form a passivation layer on the surface of the repair layer 21 by self-assembly. The passivation layer not only can fill the rugged surface of the repair layer 21 and improve the roughness of the surface of the repair layer 21, but also can protect the surface of the repair layer 21 from being scratched by instruments or chemically corroded. And increasing the concentration of PEG can increase passivation effect, so that polishing pressure needs to be increased to remove part of the passivation layer, and based on this, the raised structure on the surface of the repair layer 21 can be subjected to larger pressure, which is beneficial to accelerating removal of the raised structure and providing flatness of the surface of the repair layer 21. And, the PEG molecules may also react with the oxide or other impurities on the surface of the repair layer 21, so as to facilitate removal of the oxide or other impurities on the surface of the repair layer 21. In addition, under the combined action of the components such as PDADMAC in the polishing solution 30, the polishing efficiency and polishing effect on the repair layer 21 can be effectively improved. The present example is not limited to parameters such as specific concentration or capacity of PEG. Optionally, the concentration of PEG is less than or equal to 100ppm.

With continued reference to fig. 5, in the polishing process of the repair layer 21, the polishing method for a mask substrate provided in this embodiment further mixes the micro-nano bubble solution 31 into the polishing solution 30, so that the repair layer 21 is polished by using the polishing solution 30 without abrasive and the micro-nano bubble solution 31. Wherein, the micro-nano bubbles in the micro-nano bubble solution 31 have a series of characteristics different from the conventional bubbles, such as large specific surface area, slow rising speed of the solution, high gas dissolution rate, high mass transfer efficiency, high negative charge property, and the like. And when the micro-nano bubbles collapse, high-pressure and high-speed shock waves and micro-jet flow can be generated and directed to the surface of the repair layer 21, so that the planarization rate and the planarization effect are effectively improved. Preferably, the micro-nano bubbles are nano bubbles with the diameter smaller than or equal to 100nm. Compared with micro bubbles, the nano bubbles have better stability and removal capability.

As is clear from the above, the polishing method of the mask substrate provided in this embodiment uses the polishing solution 30 without abrasive to polish, so as to effectively avoid the problem of surface defects of the mask substrate 20 caused by abrasive. And repairing the defect on the surface of the mask substrate 20 by forming the repairing layer 21, wherein the repairing layer 21 is made of amorphous silicon, has good light transmittance, does not affect the efficacy of the mask, and is easy for the cationic polymer in the polishing solution 30 to react, so that the stability of the molecular structure on the surface of the amorphous silicon is weakened, and the amorphous silicon is polished in the abrasive-free state. In addition, the polishing solution 30 further contains PEG, which is easily adsorbed on the surface of amorphous silicon, and can improve the roughness of the surface of amorphous silicon. In addition, the micro-nano bubble solution 31 is mixed into the polishing solution 30 during the polishing process, so that the micro-nano bubbles are utilized to impact the surface of the amorphous silicon, and the planarization speed and effect are further improved.

Based on this, the post-polishing substrate structure shown in fig. 9 can be formed by the combined action of the repair layer 21 and the polishing liquid 30. That is, the mask substrate 20 has a repair layer 21 formed thereon with a flat surface. In the subsequent mask forming process, film layers such as a phase-shifting layer, a metal shading layer, an anti-reflection layer or a photoresist layer can be formed on the repair layer 21 with a flat surface; the formation of the film layer is a preparation process well known to those skilled in the art, and the description of this embodiment is omitted herein. Note that, the polishing method of the mask substrate provided in this embodiment is not limited to processing one surface of the mask substrate 20, and may also process both the upper and lower surfaces of the mask substrate 20. That is, one repair layer 21 is formed on each of the opposite surfaces of the mask substrate 20, and the two repair layers 21 are polished with the polishing liquid 30 without abrasive, respectively or simultaneously, to form a substrate structure having flat upper and lower surfaces.

Based on the same inventive concept, the present embodiment also provides a polishing system for a mask substrate for performing the above-described polishing method for a mask substrate. Referring to fig. 10, the polishing system for a mask substrate includes: a film generation module, a mechanical polishing module, and a bubble supply module. Wherein the film generation module is used for forming a repair layer 21 on the surface of the mask substrate 20; the mechanical polishing module is used for polishing the repairing layer 21 by adopting polishing solution 30 without abrasive; the bubble supply module is used for mixing micro-nano bubble solution 31 into the polishing solution 30 during the polishing of the repair layer 21.

Specifically, the embodiment is not limited to a specific method for forming the repair layer 21, and may be an evaporation process, a sputtering process, a chemical vapor deposition process, or the like. Therefore, the present embodiment is not particularly limited in the structure and type of the thin film formation module. Illustratively, the repair layer 21 is formed by a sputtering process, and the thin film forming module is a sputtering apparatus.

The mechanical polishing module is a chemical mechanical polishing device. As shown in fig. 10, the mechanical polishing module includes a polishing table 40, a polishing pad 41, a polishing head 42, and a liquid supply 43. Wherein, the polishing table 40 is used as a supporting structure of the mechanical polishing module to play a role of supporting and bearing; and, the polishing table 40 is also capable of rotating in a clockwise or counterclockwise direction to facilitate polishing of the surface of the repair layer 21. The polishing pad 41 is attached to the bearing surface of the polishing table 40, and not only rubs the surface of the repair layer 21, but also stores the polishing liquid 30, so as to ensure a sufficient reaction between the surface of the repair layer 21 and the polishing liquid 30. Preferably, the polishing pad 41 is a polyurethane polishing pad, and has a hardness ranging from 52HD to 62HD.

And the polishing head 42 is located on the polishing pad 41 and is used for limiting and moving the structure to be processed formed by the repair layer 21 and the mask substrate 20 in the polishing process. Wherein, a limit groove T is arranged on one side of the polishing head 42 close to the polishing pad 41. The structure to be treated is accommodated in the limit groove T, and the repairing layer 21 faces and is located on the polishing pad 41. Further, a motor is further connected to the other side of the polishing head 42, so as to drive the polishing head 42 to rotate, thereby driving the structure to be processed to rotate and improving the polishing effect. The rotation directions of the polishing head 42 and the polishing table 40 may be the same or opposite, and the rotation rates of the two may be the same or different, which is not particularly limited in this embodiment. Still further, an air film is further disposed in the limit groove T, and by inflating and deflating the air film, the pressure applied by the polishing head 42 to the structure to be treated can be adjusted, so as to adjust the polishing degree of the repair layer 21. Preferably, the polishing pressure ranges are: 0.5 PSI-4 PSI.

The liquid supply 43 is located at one side of the polishing table 40 for spraying the polishing liquid 30 to the polishing pad 41. Preferably, the polishing liquid 30 includes a cationic polymer and PEG. The cationic polymer may be combined with molecules of the amorphous silicon surface of the repair layer 21 to weaken the molecular connection of the amorphous silicon surface, facilitating polishing of the amorphous silicon surface in an abrasive-free state. PEG is easy to be adsorbed on the surface of amorphous silicon, so that the roughness of the surface of amorphous silicon can be improved, and the polishing effect is further improved. The polishing liquid 30 further includes other components such as water and a pH adjuster, which are not described in detail in this embodiment. Preferably, the pH regulator is KOH or HNO ₃ And the pH of the polishing liquid 30 is about 8. And, preferably, the polishingThe flow range of the optical liquid 30 is: 100 ml/min-150 ml/min.

With continued reference to fig. 10, the bubble supply module includes a bubble generator 50 and a spray head 51. Wherein the bubble generator 50 is configured to generate the micro-nano bubble solution 31. The present embodiment is not limited to the bubble generator 50 generating the micro-nano bubble solution 31 by means of gyratory shearing, pressurized dissolution, electrochemistry, microporous pressurization, or mixed jet. Illustratively, the bubble generator 50 forms the micro-nano bubble solution 31 by pressurized dissolution. The bubble generator 50 includes a gas supply reaction unit 501 and a liquid reaction unit 502 connected. The gas supply reaction unit 501 is configured to supply high-pressure gas to the liquid reaction unit 502, where the liquid reaction unit 502 has a solution therein, the high-pressure gas is dissolved in the solution in a saturated manner, and the gas is released from the solution with gradual pressure release, so as to form micro-nano bubbles. Alternatively, the gas may be oxygen or ozone, etc., and the gas supply reaction unit 501 may continuously or intermittently supply high pressure gas into the liquid reaction unit 502. And, the solution may be water, pure water, or other liquid. Preferably, the micro-nano bubbles adopted in the embodiment are nano bubbles with a diameter of less than or equal to 100nm.

Further, the spray head 51 is communicated with the bubble generator 50 and is used for spraying the micro-nano bubble solution 31 onto the polishing pad 41 so that the micro-nano bubble solution 31 is mixed with the polishing solution 30, and then the micro-nano bubble solution 31 can directly act on the surface of the repair layer 21, thereby optimizing the polishing effect and efficiency. The flow rate of the micro-nano bubble solution 31 provided to the polishing pad 41 is not limited in this embodiment, and may be adjusted according to the process requirements.

In summary, the polishing method and polishing system for a mask substrate according to the present embodiment uses the polishing solution 30 without abrasive to polish, so as to avoid the defect of abrasive application. And repairing the defect on the surface of the mask substrate 20 by forming the repairing layer 21, wherein the repairing layer 21 is made of amorphous silicon, has good light transmittance, does not affect the efficacy of the mask, and is easy for the cationic polymer in the polishing solution 30 to react, so that the stability of the molecular structure on the surface of the amorphous silicon is weakened, and the amorphous silicon is polished in the abrasive-free state. In addition, the polishing solution 30 further contains PEG, which is easily adsorbed on the surface of amorphous silicon, and can improve the roughness of the surface of amorphous silicon. In addition, the micro-nano bubble solution 31 is mixed into the polishing solution 30 during the polishing process, so that the micro-nano bubbles are utilized to impact the surface of the amorphous silicon, and the planarization speed and effect are further improved.

It should also be appreciated that while the present invention has been disclosed in the context of a preferred embodiment, the above embodiments are not intended to limit the invention. Many possible variations and modifications of the disclosed technology can be made by anyone skilled in the art without departing from the scope of the technology, or the technology can be modified to be equivalent. Therefore, any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method of polishing a mask substrate, comprising:

providing a mask substrate;

forming a repair layer on the surface of the mask substrate;

2. The method for polishing a mask substrate according to claim 1, wherein the cationic polymer comprises polydimethyldiallylammonium chloride, polyethylenimine and/or polyallylamine.

3. The method for polishing a mask substrate according to claim 1 or 2, wherein the concentration of ammonium salt in the cationic polymer is less than or equal to 250ppm.

4. The method of polishing a mask substrate according to claim 1, wherein the polishing liquid further comprises polyethylene glycol.

5. The method for polishing a mask substrate according to claim 4, wherein the concentration of polyethylene glycol is 100ppm or less.

6. The method of claim 1, wherein the repair layer comprises amorphous silicon.

7. The method of polishing a mask substrate according to claim 1, wherein the micro-nano bubbles in the micro-nano bubble solution have a diameter of 100nm or less.

8. A polishing system for a mask substrate, characterized by being used for performing the polishing method for a mask substrate according to any one of claims 1 to 7, the polishing system for a mask substrate comprising: a film generation module, a mechanical polishing module and a bubble supply module; wherein,

9. The polishing system of claim 8, wherein the mechanical polishing module comprises a polishing table, a polishing pad, a polishing head, and a liquid supply; the mask substrate is positioned on the polishing pad and is accommodated in a limit groove of the polishing head; the liquid supply device is positioned at one side of the polishing table and is used for spraying the polishing liquid to the polishing pad.

10. The polishing system of a mask substrate according to claim 9, wherein the bubble supply module comprises a bubble generator and a showerhead; wherein the bubble generator is used for generating the micro-nano bubble solution; the spray head is communicated with the bubble generator and used for spraying the micro-nano bubble solution to the polishing pad so as to mix the micro-nano bubble solution with the polishing solution.