Method and apparatus for post-cmp cleaning of transparent substrates
Patent Information
- Application Number
- CN202611426720.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-14
- Publication Date
- 2026-11-03
AI Technical Summary
Traditional wet CMP post-cleaning methods cannot effectively retain CeO2, Ce(OH)4, or SiO2 particles within scratches on the surface of quartz substrates, resulting in high difficulty and cost in scratch repair and hindering photolithography processes.
Plasma bombardment of a transparent substrate with a positive bias voltage is used to selectively remove particles in flat areas while retaining particles in scratches. Combined with ultraviolet irradiation and heat treatment, the chemical bonding between particles and scratch sidewalls is enhanced.
It enables selective cleaning of quartz substrate surfaces, ensuring product cleanliness, reducing scratch repair costs, improving scratch repair efficiency, and is suitable for short-wavelength photolithography processes.
Smart Images
Figure CN123035889A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of integrated circuit technology, and in particular to a method and apparatus for cleaning transparent substrates after CMP. Background Technology
[0002] Post-CMP cleaning is a critical process in semiconductor manufacturing to remove residual polishing fluid, nano-abrasive particles, metal ions, and organic matter from the surface of quartz substrates. It directly determines the yield of subsequent photolithography or deposition. If cleaning is not thorough, it will cause particle defects, metal diffusion short circuits, or low-k dielectric damage.
[0003] Generally, traditional wet CMP post-cleaning methods typically remove all particles from the flat areas and scratches on the surface of a quartz substrate to ensure its cleanliness. However, the inventors of this application have discovered that polishing particles made of materials such as CeO2, Ce(OH)4, or SiO2 in CMP polishing slurries have extremely low absorption rates (<5%) for ultraviolet light in the photolithography band, and their transmittance is similar to that of a transparent quartz substrate. These particles can be used to repair scratches on the quartz substrate surface. Traditional wet CMP post-cleaning methods remove all the filling particles within the scratches, which is detrimental to scratch repair. During the repair process, repair particles must be refilled into the scratches, which is difficult and prone to causing surface contamination, resulting in low scratch repair efficiency and high repair costs.
[0004] Therefore, there is an urgent need to provide a post-CMP cleaning method for transparent substrates that can selectively clean the surface of quartz substrates, so as to improve the repair efficiency of scratches on the surface of quartz substrates and reduce the cost of scratch repair. Summary of the Invention
[0005] The purpose of this invention is to provide a method and apparatus for cleaning transparent substrates after CMP that can selectively clean the surface of quartz substrates, thereby improving the repair efficiency of scratches on the surface of quartz substrates and reducing the cost of scratch repair.
[0006] To achieve the above objectives, the present invention provides a method for cleaning a transparent substrate after CMP, comprising the following steps: Provide a transparent substrate that has undergone CMP process and is ready for cleaning; Plasma bombardment of transparent substrates; A positive bias voltage is applied to the transparent substrate to remove particles in the flat areas of the transparent substrate surface, while retaining particles in the scratches on the transparent substrate surface.
[0007] The aforementioned CMP post-cleaning method for transparent substrates employs plasma bombardment of the transparent substrate, applying a positive bias voltage during the plasma bombardment process to selectively clean flat areas and surface scratches on the transparent substrate surface. During plasma bombardment, a sheath layer separates the plasma from the substrate. Applying a positive bias voltage raises the substrate potential above the plasma potential, causing the sheath layer to invert into an electron sheath layer. Positive ions are repelled and can hardly reach the transparent substrate surface. Only neutral free radicals, plasma ultraviolet photons, and low-energy electrons act on the transparent substrate. Due to the repulsion of positive ions, sputtering and ion-enhanced etching disappear, and the surface reaction degenerates into pure chemical etching using free radicals and photons. Particles in the flat areas protrude from the surface, opening up the entire upper hemisphere space to receive a full flux of free radicals. These free radicals chemically decompose the particulate material, causing it to volatilize, or isotropically erode the substrate from the bottom / around the particles, reducing the contact area, causing loss of adhesion, and resulting in detachment. Simultaneously, plasma ultraviolet photons also reach the exposed particles, providing photo-assisted decomposition. The particle dose in the flat areas exceeds the removal threshold, effectively removing particles from the transparent substrate surface. The dose received by particles within the scratch is discounted multiple times. After free radicals enter the groove, they undergo multiple Knudsen diffusion collisions. Some of them are lost due to adhesion / recombination on the sidewalls. Furthermore, the bottom of the scratch can only receive free radicals through the open solid angle, resulting in a significant decrease in flux. Consequently, the dose received by particles within the scratch is far below the removal threshold and is retained in situ.
[0008] In summary, the above-mentioned post-CMP cleaning method for transparent substrates can selectively clean the surface of quartz substrates. This method can effectively remove particles from the flat areas of the transparent substrate surface, ensuring product cleanliness, while retaining particles within surface scratches. CeO2 particles, Ce(OH)4 particles, or SiO2 particles within the scratches can be directly used to repair the scratches, which helps to improve the repair efficiency of scratches on the surface of quartz substrates and reduce scratch repair costs.
[0009] In one embodiment, the above-described post-CMP cleaning method for transparent substrates further includes the following step: applying a negative bias voltage to the transparent substrate to remove particles from flat areas and scratches on the surface of the transparent substrate.
[0010] In one embodiment, the step of plasma bombarding the transparent substrate includes the following steps: Bombard the transparent substrate with oxygen plasma; The transparent substrate is bombarded with fluorine and / or chlorine plasma; The transparent substrate was bombarded again with oxygen plasma.
[0011] In one embodiment, the pressure for plasma treatment of the transparent substrate is no greater than 10 mTorr.
[0012] In one embodiment, after applying a positive bias voltage to the transparent substrate to remove particles from the flat areas of the transparent substrate surface and retain the particles within the scratches on the transparent substrate surface, the method further includes the following step: The transparent substrate is subjected to ultraviolet light irradiation and / or baking treatment.
[0013] In one embodiment, the temperature of ultraviolet irradiation and / or baking is not greater than 200°C.
[0014] In one embodiment, after applying a positive bias voltage to the transparent substrate to remove particles from the flat areas of the transparent substrate surface and retain the particles within the scratches on the transparent substrate surface, the method further includes the following step: The transparent substrate is subjected to rapid thermal annealing.
[0015] In one embodiment, the rapid thermal annealing temperature is no greater than 400°C.
[0016] On the other hand, the present invention also provides a post-CMP cleaning device for transparent substrates, comprising: a cleaning chamber, a plasma source, and a bias module, wherein the plasma source is disposed at the top of the cleaning chamber and the bias module is disposed at the bottom of the cleaning chamber.
[0017] The aforementioned transparent substrate CMP post-cleaning device is used to implement the aforementioned transparent substrate CMP post-cleaning method. This device can selectively clean the surface of the quartz substrate, effectively remove particles from the flat areas of the transparent substrate surface, ensure product cleanliness, and retain particles within surface scratches. CeO2 particles, Ce(OH)4 particles, or SiO2 particles within the scratches can be directly used to repair the scratches, which helps to improve the repair efficiency of scratches on the quartz substrate surface and reduce scratch repair costs.
[0018] In one embodiment, the post-CMP cleaning device for transparent substrates further includes a curing module connected to the cleaning chamber. The curing module is used to perform energy excitation treatment on the cleaned transparent substrate to enhance the chemical bonding between particles and scratch sidewalls. Attached Figure Description
[0019] Figure 1 This is a flowchart illustrating a post-CMP cleaning method for a transparent substrate according to one embodiment. Figure 2 This is a schematic diagram of the structural principle of a post-CMP cleaning device for transparent substrates according to an embodiment.
[0020] Explanation of reference numerals in the attached figures: 10-Transparent substrate, 20-Cleaning chamber, 30-Plasma source, 40-Bias module, 50-Suction component. Detailed Implementation
[0021] The present invention will be described more clearly and completely by way of embodiments and in conjunction with the accompanying drawings, but the present invention is not limited to the scope of the following embodiments.
[0022] As semiconductor lithography technology evolves towards shorter wavelengths (such as 248nm, 193nm, and even the EUV band), the surface quality requirements for quartz (Qz) substrates used in photomasks are becoming increasingly stringent. In the chemical mechanical polishing (CMP) process of quartz substrates, abrasive particles in the polishing slurry (such as cerium dioxide (CeO2) and silicon dioxide (SiO2)) can create nanoscale scratches on the substrate surface, typically between 10nm and 30nm in depth. These defects, whose size is close to or larger than the wavelength used in lithography, cause severe Mie or Rayleigh scattering, resulting in incident light intensity loss, optical path deviation, and stray light generation. This is one of the most serious killer defects in advanced photomask manufacturing.
[0023] This invention provides a method and apparatus for cleaning transparent substrates after CMP (Continuous Metallurgy Processing). This method and apparatus can selectively clean the surface of a quartz substrate, effectively removing particles from flat areas of the transparent substrate surface to ensure product cleanliness. It can also retain particles within surface scratches. CeO2, Ce(OH)4, or SiO2 particles within the scratches can be directly used to repair the scratches, enabling the transparent substrate to effectively meet the exposure requirements of short-wavelength lithography processes. This method and apparatus for cleaning transparent substrates after CMP helps improve the repair efficiency of scratches on the quartz substrate surface, reduces scratch repair costs, and improves the product yield of transparent substrates.
[0024] Please refer to the following: Figure 1 A method for cleaning a transparent substrate after CMP (Continuous Metallurgy Processing) includes the following steps: Step S11: Provide a transparent substrate that has been processed by CMP and is to be cleaned.
[0025] Specifically, the transparent substrate can be any transparent substrate, and it can be any shape such as square or round. For ease of explanation, this embodiment uses a glass substrate as an example, specifically a quartz glass substrate (quartz substrate) used as a photomask in the semiconductor field. Further, nanoscale scratches are generated on the surface of the transparent substrate after CMP processing, and tiny polishing particles naturally fill the nanoscale scratches during the CMP process. These polishing particles include at least one of CeO2 particles, Ce(OH)4 particles, or SiO2 particles.
[0026] Step S12: Plasma bombardment is performed on the transparent substrate.
[0027] Specifically, to ensure efficient cleaning of the quartz substrate, the plasma preferably includes at least one of oxygen plasma, chlorine plasma, and fluorine plasma. Furthermore, to ensure that the plasma provides sufficiently high energy to remove contaminants from the transparent substrate surface and guarantees cleaning efficiency, while maintaining a sufficiently low particle density to prevent physical or chemical damage to the quartz substrate surface, the pressure used for plasma treatment of the quartz substrate is preferably no greater than 10 mTorr.
[0028] Step S13: Apply a positive bias voltage to the transparent substrate to remove particles in the flat areas of the transparent substrate surface, while retaining particles in the scratches on the transparent substrate surface.
[0029] In this embodiment, a positive bias voltage is applied to the transparent substrate during plasma bombardment to achieve selective cleaning of flat areas and surface scratches on the transparent substrate surface. Specifically, during plasma bombardment of the transparent substrate, a sheath layer separates the plasma from the substrate. When a positive bias voltage is applied to the transparent substrate, the substrate potential is raised above the plasma potential, and the sheath layer reverses to become an electron sheath layer. Positive ions are repelled and can hardly reach the surface of the transparent substrate. Only neutral free radicals, plasma ultraviolet photons, and low-energy electrons act on the transparent substrate. Due to the repulsion of positive ions, sputtering and ion-enhanced etching disappear, and the surface reaction degenerates into pure chemical etching of free radicals and photons. Particles in the flat areas protrude from the surface, opening up the entire upper hemisphere space to receive the full flux of free radicals. The free radicals chemically decompose the particulate material, causing it to volatilize, or isotropically etch the substrate from the bottom / around the particles, reducing the contact area, losing adhesion, and causing them to fall off. At the same time, plasma ultraviolet photons also reach the exposed particles directly, providing photo-assisted decomposition. The particle dose in the flat areas exceeds the removal threshold, and the particles on the surface of the transparent substrate are effectively removed. The dose received by particles within the scratch is discounted multiple times. After free radicals enter the groove, they undergo multiple Knudsen diffusion collisions. Some of them are lost due to adhesion / recombination on the sidewalls. Furthermore, the bottom of the scratch can only receive free radicals through the open solid angle, resulting in a significant decrease in flux. Consequently, the dose received by particles within the scratch is far below the removal threshold and is retained in situ.
[0030] The aforementioned CMP-fed cleaning method for transparent substrates employs plasma bombardment of the transparent substrate, applying a positive bias voltage during the plasma bombardment process to selectively clean flat areas and surface scratches on the transparent substrate surface. This method effectively removes particles from flat areas of the transparent substrate surface, ensuring product cleanliness, while retaining particles within surface scratches. CeO2, Ce(OH)4, or SiO2 particles within the scratches can be directly used to repair the scratches, helping to improve the repair efficiency of quartz substrate surface scratches and reduce scratch repair costs.
[0031] In one embodiment, step S12 includes the following steps: Step S121: Bombard the transparent substrate with oxygen plasma.
[0032] This embodiment employs oxygen plasma bombardment of a transparent substrate to oxidize and decompose organic contaminants and activate the surface. Specifically, the oxygen plasma generates reactive oxygen free radicals (O₂, O₂). + O - O * The active oxygen radicals react with hydrocarbon organic residues to generate volatile gaseous products such as CO2 and H2O, achieving residue-free stripping of organic matter. At the same time, the active oxygen radicals break the surface chemical bonds and introduce oxygen-containing functional groups, which significantly improves hydrophilicity and provides a more uniform reaction interface for the S12 fluorine / chlorine chemical etching step.
[0033] Step S122: Bombard the transparent substrate with fluorine and / or chlorine plasma.
[0034] Specifically, fluorine-based plasmas can be, but are not limited to, using CF4, NF3, or SF6, and chlorine-based plasmas can be, but are not limited to, using Cl2 or BCl3. Fluorine radicals and / or chlorine radicals desorb particles through the synergistic effect of ion bombardment and chemical etching, removing inorganic residues and metal contaminants.
[0035] Step S123: Bombard the transparent substrate with oxygen plasma again.
[0036] This embodiment employs oxygen plasma to oxidize and decompose the byproduct residues of step S122, and to repair the surface chemical state. Specifically, oxygen free radicals react with fluoropolymers to generate CO2 and HF volatilization, and oxidize with metal chlorides to generate volatile oxides, removing the fluorine / chlorine-containing byproducts generated in step S122. Simultaneously, oxygen free radicals can oxidize trace metal residues that were not completely removed in step 2 into high-valence oxides, eliminate surface passivation caused by fluorine / chlorine, restore hydroxyl balance and hydrophilicity, and repair the surface chemical state, preparing it for subsequent thin film deposition or bonding. Furthermore, the active particles in the high-energy oxygen plasma can break the original Si-O-Si siloxane bonds on the quartz surface and introduce highly active Si-OH groups, which facilitates more efficient and stronger bonding of CeO2 particles, Ce(OH)4 particles, and / or SiO2 particles to the scratch sidewalls during subsequent scratch repair treatment.
[0037] In one embodiment, the above-described post-CMP cleaning method for transparent substrates further includes the following steps: Step S14: Apply a negative bias voltage to the transparent substrate to remove particles from the flat areas and scratches on the surface of the transparent substrate.
[0038] Specifically, a negative bias voltage is applied to the quartz substrate, making the substrate potential lower than the plasma potential. The sheath electric field accelerates positive ions towards the surface of the quartz substrate. These ions have high kinetic energy and their incident direction is almost perpendicular to the surface. The directional ions directly bombard the exposed particles. Ion collisions and adsorbed free radicals synergistically generate ion-enhanced chemical etching. The vertical ion trajectory can reach the bottom particles. Ions entering at a grazing angle bombard the upper edge sidewalls of the scratches. Sputtering combined with ion-enhanced etching causes the sidewalls to recede, the opening to widen, and the aspect ratio to continuously decrease, gradually exposing the internal particles, which are then directly bombarded and removed like particles in the flat area. This embodiment, by applying a negative bias voltage to the transparent substrate during plasma bombardment, can simultaneously remove particles from both the flat areas and scratches on the transparent substrate surface, meeting the scratch cleaning requirements. The transparent substrate CMP post-cleaning method of this invention can selectively retain or remove particles within the scratches as needed, meeting the application requirements of different scenarios and having a wide range of applications.
[0039] In one embodiment, after step S13, the method further includes the following steps: subjecting the transparent substrate to ultraviolet light irradiation and / or baking. Alternatively, subjecting the transparent substrate to rapid thermal annealing.
[0040] This embodiment applies an energy-excitation treatment to the transparent substrate after surface cleaning by ultraviolet light irradiation or heat treatment. This provides sufficient energy to initiate chemical bonding between the particles retained within the scratches and the scratch sidewalls, enhancing the chemical adhesion between the particles and the scratch sidewalls and repairing the scratches. Specifically, after completing the surface cleaning process of the quartz substrate, an energy-excitation treatment is applied to the quartz substrate by ultraviolet light irradiation or heat treatment. This provides sufficient energy to initiate chemical bonding between the particles retained within the scratches and the scratch sidewalls, allowing the CeO2 particles and Ce(OH)2 particles to bond together. )4 The polishing particles and / or SiO2 particles form strong chemical bonds (such as Si-O-Ce bonds) with the SiO2 matrix on the scratch sidewalls, enhancing the chemical bonding between the polishing particles and the scratch sidewalls, ensuring that the particles are fixed in the scratch, and thus repairing the scratch. Furthermore, to avoid introducing residual stress on the surface due to excessively high temperatures, which could damage the optical uniformity of the transparent substrate, it is preferable that the temperature of ultraviolet irradiation and / or baking does not exceed 200°C, and the temperature of rapid thermal annealing does not exceed 400°C.
[0041] On the other hand, please see Figure 2The present invention also provides a post-CMP cleaning device for transparent substrates, comprising: a cleaning chamber 20, a plasma source 30, and a bias module 40. The plasma source 30 is disposed at the top of the cleaning chamber 20, the cleaning chamber 20 having a cleaning chamber for accommodating the transparent substrate 10, and the bias module 40 being disposed at the bottom of the cleaning chamber 20. The post-CMP cleaning device for transparent substrates of this embodiment is used to implement the above-described post-CMP cleaning method for transparent substrates. This device can selectively clean the surface of a quartz substrate, effectively removing particles from flat areas of the transparent substrate 10 surface, ensuring product cleanliness, and retaining particles within surface scratches. CeO2 particles, Ce(OH)4 particles, or SiO2 particles within the scratches can be directly used to repair the scratches, helping to improve the repair efficiency of scratches on the transparent substrate surface and reduce scratch repair costs.
[0042] In one embodiment, the post-CMP cleaning apparatus for transparent substrates further includes a curing module (not shown in the figure). The curing module is connected to the cleaning chamber and is used to perform energy-excitation treatment on the cleaned transparent substrate to enhance the chemical bonding between particles and scratch sidewalls. Specifically, the curing apparatus may include, but is not limited to, at least one of a UV curing apparatus, a dryer, and a rapid annealing furnace.
[0043] In one embodiment, the post-CMP cleaning device for transparent substrates further includes a suction member 50. The cleaning chamber 20 is provided with an exhaust port, and the suction member 50 is connected to the exhaust port. The suction member 50 is used to discharge the reaction gas generated during the cleaning process to avoid contamination of the chamber and ensure the cleanliness of the cleaning chamber.
[0044] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the scope of the present invention.
Claims
1. A method for cleaning a transparent substrate after CMP, characterized in that, Includes the following steps: Provide a transparent substrate that has undergone CMP process and is ready for cleaning; The transparent substrate is subjected to plasma bombardment; A positive bias voltage is applied to the transparent substrate to remove particles in the flat areas of the transparent substrate surface, while retaining particles in the scratches on the transparent substrate surface.
2. The cleaning method for transparent substrates after CMP according to claim 1, characterized in that, It also includes the following steps: A negative bias voltage is applied to the transparent substrate to remove particles from the flat areas and scratches on the surface of the transparent substrate.
3. The cleaning method for transparent substrates after CMP according to claim 1, characterized in that, The step of bombarding the transparent substrate with plasma includes the following steps: The transparent substrate was bombarded with oxygen plasma. The transparent substrate is bombarded with fluorine and / or chlorine plasma; The transparent substrate was then bombarded again with oxygen plasma.
4. The cleaning method for transparent substrates after CMP according to claim 1, characterized in that, The pressure for plasma treatment of the transparent substrate is no greater than 10 mTorr.
5. The cleaning method for transparent substrates after CMP according to claim 1, characterized in that, After the step of applying a positive bias voltage to the transparent substrate to remove particles in the flat areas of the transparent substrate surface and retain particles in the scratches on the transparent substrate surface, the method further includes the following step: The transparent substrate is subjected to ultraviolet light irradiation and / or baking treatment.
6. The cleaning method for transparent substrates after CMP according to claim 5, characterized in that, The temperature of the ultraviolet irradiation and / or baking shall not exceed 200°C.
7. The cleaning method for transparent substrates after CMP according to claim 1, characterized in that, After the step of applying a positive bias voltage to the transparent substrate to remove particles in the flat areas of the transparent substrate surface and retain particles in the scratches on the transparent substrate surface, the method further includes the following step: The transparent substrate is subjected to rapid thermal annealing.
8. The cleaning method for transparent substrates after CMP according to claim 7, characterized in that, The rapid thermal annealing temperature is no greater than 400°C.
9. A post-CMP cleaning apparatus for transparent substrates, characterized in that, include: The cleaning chamber includes a plasma source and a bias module. The plasma source is located at the top of the cleaning chamber, and the bias module is located at the bottom of the cleaning chamber.
10. The post-CMP cleaning apparatus for transparent substrates according to claim 9, characterized in that, The transparent substrate CMP post-cleaning device further includes a curing module, which is connected to the cleaning chamber. The curing module is used to perform energy excitation treatment on the transparent substrate after cleaning to enhance the chemical bonding between particles and scratch sidewalls.