Planarization method for MoSi-based photomask substrate

Abstract

The invention relates to a planarization method for a MoSi-based photomask substrate. The method comprises the following steps: providing a MoSi-based photomask substrate; or, providing a photomask substrate, and depositing a MoSi thin film on the photomask substrate to form the MoSi-based photomask substrate; the MoSi-based photomask substrate is subjected to primary planarization treatment, and a primary polished MoSi-based photomask substrate is obtained; and carrying out re-planarization treatment on the MoSi-based photomask substrate subjected to primary polishing, so as to obtain a MoSi-based photomask substrate subjected to secondary polishing. According to the invention, the surface roughness is reduced, the uniformity of the film surface is improved, and the consistency of the overall performance of the photomask is ensured.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and to a planarization method for MoSi (molybdenum silicon) based photomask substrates, and more particularly to a method for synergistic planarization of MoSi based photomask substrates using chemical mechanical polishing (CMP) and ion beam polishing (IBP) processes. Background Technology

[0002] In semiconductor photolithography, the photomask is a crucial component for accurately transferring circuit patterns to the wafer, and the surface quality of its substrate plays a decisive role in photolithography accuracy. MoSi material, due to its excellent optical, thermal, and mechanical properties, is often used as a photomask substrate. However, during the fabrication of MoSi substrates, due to factors such as deposition processes and material growth characteristics, surface roughness and step height differences inevitably occur. These surface defects cause light scattering and diffraction during propagation, thereby reducing photolithography resolution and affecting chip manufacturing yield and performance.

[0003] To address the surface planarization issue of MoSi substrates, various process technologies have been developed in the industry, but all have limitations that are difficult to overcome and cannot meet the manufacturing requirements of high-end photomasks: 1) CMP process achieves surface planarization through the synergistic effect of mechanical grinding and chemical etching, but it has the following defects in MoSi substrate processing: Limited reduction in surface roughness: Although CMP process can quickly remove macroscopic unevenness, it has limited improvement on microscopic roughness, usually only reducing surface roughness to 1-2nm, which is difficult to meet the requirements of high-end photomasks for ultra-smooth surfaces (<0.5nm); Insufficient surface uniformity: CMP process may produce local over-polishing or under-polishing phenomena during polishing, resulting in poor surface uniformity and affecting the overall performance of the photomask; Risk of surface damage: Mechanical grinding in CMP process may cause scratches or microcracks on the surface of MoSi film, affecting the service life of the photomask; Polishing slurry contamination: Chemical components in CMP polishing slurry may remain on the surface, which is difficult to clean thoroughly, resulting in surface contamination; 2) IBP process uses high-energy ion beams to bombard the material surface and selectively sputter to remove microscopic protrusions. While atomic-level surface smoothing can theoretically meet the requirements for ultra-smooth surfaces, this process faces multiple limitations in industrial applications: Low processing efficiency: Although the IBP process can achieve atomic-level smoothing, its material removal rate is low and the processing time is long, making it unsuitable for large-scale production; High cost: IBP equipment is expensive, and the process consumes a lot of energy, resulting in a high overall cost; High requirements for initial surface quality: The IBP process has high requirements for initial surface roughness. If the surface roughness is too large, the IBP processing time will increase significantly, and it may even fail to achieve the expected results; Surface stress problems: High-energy ion beam bombardment may cause stress on the surface of MoSi films, affecting the mechanical properties and stability of the films; 3) Defects of other surface treatment technologies: Wet etching: The etching rate is difficult to control precisely, which may lead to over-etching or under-etching of the surface; The etching solution may cause chemical damage to the MoSi film, affecting its optical properties; The surface uniformity is poor, making it difficult to achieve an ultra-smooth surface; Dry etching: The etching rate is slow, and the processing efficiency is low; Byproducts may be generated during the etching process, contaminating the surface; High equipment requirements and high cost. Summary of the Invention

[0004] This invention provides a planarization method for MoSi-based photomask substrates, specifically a method for the synergistic planarization of CMP and IBP processes for MoSi-based photomask substrates. This method overcomes the shortcomings of existing technologies, achieves ultra-precision planarization of the molybdenum-silicon surface, improves photomask quality, and meets the requirements of high-end semiconductor manufacturing processes.

[0005] This invention provides a planarization method for MoSi-based photomask substrates, comprising the following steps: A MoSi-based photomask substrate is provided; or, a photomask substrate is provided on which a MoSi thin film is deposited to form the MoSi-based photomask substrate. The MoSi-based photomask substrate is subjected to preliminary planarization treatment to obtain a first-polished MoSi-based photomask substrate; and The first-polished MoSi-based photomask substrate is then re-planarized to obtain a second-polished MoSi-based photomask substrate.

[0006] Furthermore, the photomask substrate comprises quartz glass and a silicon substrate. Preferably, the photomask substrate is quartz glass.

[0007] Further, the thickness of the MoSi film is 90-100 nm. Preferably, the thickness of the MoSi film is 100 nm. Specifically, the thickness of the MoSi film is determined according to specific requirements.

[0008] Furthermore, a MoSi thin film is deposited on the surface of the photomask substrate using physical vapor deposition (PVD).

[0009] Furthermore, a preliminary planarization process is performed using chemical mechanical polishing (CMP). This preliminary planarization process includes: The MoSi-based photomask substrate is fixed on the stage of the CMP equipment; Setting chemical mechanical polishing parameters; and The CMP equipment is started to perform preliminary planarization on the surface of the MoSi thin film on the MoSi-based photomask substrate to obtain the first-polished MoSi-based photomask substrate. The preliminary planarization process of CMP is a rough polishing stage, the purpose of which is to quickly remove macroscopic uneven areas on the surface of the MoSi thin film and reduce the surface roughness to the 1-2nm level. The CMP process can uniformly act on the entire surface, avoiding unevenness in local areas. After CMP treatment, the surface roughness is significantly reduced, providing a smoother base surface for the subsequent IBP process.

[0010] Furthermore, the chemical mechanical polishing parameters include a single polishing pressure, a single polishing time, and a polishing disc rotation speed. The single polishing pressure is 1-5 psi, the single polishing time is 1-5 min, and the polishing disc rotation speed is 100-110 rpm. Preferably, the single polishing pressure is 3 psi, the single polishing time is 3 min, and the polishing disc rotation speed is 100 rpm.

[0011] Furthermore, it also includes: A polishing slurry is prepared for use in a preliminary planarization treatment. The polishing slurry comprises silica abrasive and an oxidant. The silica abrasive (silica abrasive is made of SiO2 nano- to micron-sized particles) has a particle size of 50-60 nm and a concentration of 5-8 wt%. The oxidant is H2O2 with a concentration of 2-5 wt%. The pH value of the polishing slurry is 9-9.5. Preferably, the silica abrasive has a particle size of 50 nm and a concentration of 5 wt%, and the H2O2 concentration is 2 wt%. The preliminary planarization treatment efficiently removes surface protrusions through a combination of mechanical grinding (silica abrasive) and chemical etching (oxidant). The chemical components in the polishing slurry remove surface contaminants.

[0012] Furthermore, the pH of the polishing solution is adjusted to 9.5 using a pH adjuster (ammonia NH4OH).

[0013] Furthermore, it also includes: The MoSi-based photomask substrate was cleaned after the first polishing process to remove residual polishing slurry; and The cleaned and polished MoSi-based photomask substrate is then dried.

[0014] Furthermore, the drying process includes blowing or drying with nitrogen gas.

[0015] Furthermore, a re-planarization process is performed using ion beam polishing (IBP), which includes: The dried, first-polished MoSi-based photomask substrate is transferred to the IBP equipment; Setting ion beam polishing parameters; and The IBP (In-Planetization) equipment is activated to perform a re-planarization process on the surface of the MoSi thin film on the first-polished MoSi-based photomask substrate to obtain the second-polished MoSi-based photomask substrate. The IBP process, which performs re-planarization, is a fine polishing stage that can complete microscopic planarization in a short time. Through ion beam bombardment, localized microscopic defects are eliminated, aiming to remove microscopic uneven areas and reduce surface roughness to below 0.5 nm, achieving an ultra-smooth surface. The IBP process can planarize the surface at the atomic scale, eliminating microscopic defects that CMP (Chemical Metallurgy Process) cannot handle. After IBP treatment, the surface finish is significantly improved, light scattering is reduced, and the optical performance of the photomask is enhanced.

[0016] Further, the ion beam polishing parameters include ion beam energy, ion beam incident angle, secondary polishing time, and ion source. The ion beam energy is 100-500 eV, the ion beam incident angle is 30-60°, the secondary polishing time is 1-10 min, and the ion source is Ar⁺. Preferably, the ion beam energy is 300 eV, the ion beam incident angle is 45°, and the secondary polishing time is 5 min. The re-planarization process uses a high-energy ion beam to bombard the surface, selectively removing microscopic protrusions to achieve atomic-level flatness.

[0017] Furthermore, it also includes: Clean the MoSi-based photomask substrate that has undergone secondary polishing.

[0018] In this invention, a planarization method for MoSi-based photomask substrates uses CMP as a preliminary treatment to rapidly reduce surface roughness, and IBP as a fine treatment to further improve surface quality. CMP provides a good foundation for IBP, while IBP compensates for the shortcomings of CMP in achieving microscopic flatness. The principle of the planarization method is as follows: CMP (Chemical Molybdenum Polishing) involves mechanical grinding and chemical etching. Silica abrasives in the polishing slurry rub against the MoSi surface under pressure, removing surface protrusions. Oxidants (such as H2O2) in the polishing slurry react chemically with MoSi, softening the surface material and making it easier for the abrasives to remove. The synergistic effect of mechanical grinding and chemical etching achieves efficient and uniform surface planarization. In IBP (Inductively Coupled Processing), a high-energy ion beam (such as Ar⁺) bombards the MoSi surface at a specific angle, transferring the energy of surface atoms to the interior of the material. This allows for the selective sputtering removal of atoms from protrusions. By controlling the ion beam energy and incident angle, atomic-scale surface planarization can be achieved, eliminating microscopic defects. Furthermore, ion beam bombardment can remove surface contaminants, further improving surface quality.

[0019] The present invention has at least the following beneficial effects: 1) In the planarization method for MoSi-based photomask substrates, the present invention combines CMP and IBP processes to reduce the surface roughness of the MoSi thin film to below 0.5 nm, achieving an ultra-smooth surface. This not only reduces surface roughness but also improves the uniformity of the film surface, ensuring the consistency of the overall photomask performance, significantly reducing light scattering on the photomask surface, and improving the contrast and resolution of the lithographic pattern, thereby improving the manufacturing yield of semiconductor devices; 2) The method of the present invention optimizes the process parameters of CMP and IBP (such as polishing slurry formulation, polishing pressure, ion beam energy, etc.), resulting in good process repeatability, suitability for large-scale production, and applicability. It has wide applicability to different types of photomask substrates (such as quartz glass, silicon substrates, etc.) and MoSi thin films of different thicknesses; 3) The CMP and IBP processes have clear sequences and distinct layers, ensuring that each step addresses specific surface problems and avoids resource waste. Moreover, as independent process modules, CMP and IBP can adjust parameters or replace equipment according to specific needs. Furthermore, CMP and IBP equipment are commonly used in semiconductor manufacturing, eliminating the need for additional equipment development, reducing the cost and difficulty of technology implementation, and making it easy to promote and apply; 4) The planarization method provided by this invention provides key technical support for the manufacturing of high-end photomasks, which helps to promote the further development of the semiconductor industry. Attached Figure Description

[0020] To further illustrate the above and other advantages and features of the various embodiments of the present invention, a more specific description of the embodiments of the invention will be presented with reference to the accompanying drawings. It is to be understood that these drawings depict only typical embodiments of the invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by identical or similar reference numerals for clarity.

[0021] Figure 1 A schematic flowchart of a planarization method for a MoSi-based photomask substrate is shown in some embodiments of the present invention. Detailed Implementation

[0022] It should be noted that the components in the accompanying drawings may be shown exaggerated for illustrative purposes and may not be to scale.

[0023] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0024] In this invention, unless otherwise specified, the quantifiers “a” and “one” do not exclude scenarios involving multiple elements.

[0025] It should also be noted that, in the embodiments of the present invention, only a portion of the parts or components may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, the required parts or components can be added as needed for specific scenarios.

[0026] It should also be noted that within the scope of this invention, the terms "same", "equal", and "equal to" do not mean that the two values ​​are absolutely equal, but allow for a certain reasonable error. In other words, the terms also cover "substantially the same", "substantially equal", and "substantially equal to".

[0027] It should also be noted that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not explicitly or implicitly suggest that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] Furthermore, the embodiments of the present invention describe the process steps in a specific order. However, this is only for the convenience of distinguishing each step, and is not a limitation on the order of each step. In different embodiments of the present invention, the order of each step can be adjusted according to the process.

[0029] In the following embodiments, the photomask substrate is quartz glass; Example 1 This embodiment provides a planarization method for MoSi-based photomask substrates. Figure 1 The flowchart of the flattening method is shown, including the following steps: A photomask substrate is provided with a clean and uncontaminated surface. A MoSi thin film is deposited on the photomask substrate using the PVD method to form a MoSi-based photomask substrate. The thickness of the MoSi thin film is 100 nm, and the surface roughness of the deposited MoSi thin film is about 2.5 nm. A preliminary planarization process for a MoSi-based photomask substrate is performed using CMP (chemical mechanical polishing) to obtain a one-time polished MoSi-based photomask substrate. The process includes: fixing the MoSi-based photomask substrate on the stage of a CMP apparatus; setting the chemical mechanical polishing parameters (one-time polishing pressure of 3 psi, one-time polishing time of 3 min, and polishing disc rotation speed of 100 rpm); preparing a polishing slurry for the preliminary planarization process, the slurry comprising silica abrasive and an oxidant, the silica abrasive having a particle size of 50 nm and a concentration of 5 wt%, and H2O2 concentration of 2 wt%; adjusting the pH of the polishing slurry to 9.5 using a pH adjuster (ammonia NH4OH); starting the CMP apparatus to perform preliminary planarization on the MoSi thin film surface on the MoSi-based photomask substrate to obtain a one-time polished MoSi-based photomask substrate; cleaning the one-time polished MoSi-based photomask substrate to remove residual polishing slurry; and drying the cleaned one-time polished MoSi-based photomask substrate (by blowing with nitrogen or baking). The surface roughness of the MoSi thin film on the MoSi-based photomask substrate was reduced to 1.2 nm in a single polishing process. A secondary polished MoSi-based photomask substrate was obtained by re-planarizing a first-polished MoSi-based photomask substrate using an IBP process. The process included: transferring the dried first-polished MoSi-based photomask substrate to an IBP device; setting the ion beam polishing parameters (ion beam energy 300 eV, ion beam incident angle 45°, secondary polishing time 5 min, ion source Ar⁺); starting the IBP device to re-planarize the MoSi thin film surface on the first-polished MoSi-based photomask substrate to obtain the secondary polished MoSi-based photomask substrate; and cleaning the secondary polished MoSi-based photomask substrate. After IBP treatment, the surface roughness of the MoSi thin film on the secondary polished MoSi-based photomask substrate was reduced to 0.3 nm, achieving an ultra-smooth surface.

[0030] The results of the above-mentioned secondary polishing of MoSi-based photomask substrates were analyzed: The surface morphology of the treated MoSi film was characterized using atomic force microscopy (AFM), and the results showed that the surface roughness (Ra) was 0.3 nm and the surface uniformity was good. Scanning electron microscopy (SEM) revealed that the MoSi thin film surface had no obvious scratches or defects, meeting the manufacturing requirements for high-end photomasks.

[0031] Comparative Example 1 The only difference between this comparative example and Example 1 is that no replanarization process was performed (i.e., the IBP process was not used). Everything else is the same as Example 1. The final surface roughness is 1.2 nm.

[0032] Comparative Example 2 The only difference between this comparative example and Example 1 is that no preliminary planarization treatment was performed (i.e., no CMP process was used). Everything else is the same as Example 1. The final surface roughness is 0.8 nm.

[0033] The results show that the planarization method for MoSi-based photomask substrates provided by the present invention can significantly reduce the surface roughness of MoSi films, and the effect is better than that of a single process.

[0034] While some embodiments of the present invention have been described in this application, those skilled in the art will understand that these embodiments are merely illustrative. Numerous variations, alternatives, and improvements will arise in those skilled in the art under the teachings of this invention without departing from its scope. The appended claims are intended to define the scope of the invention and thereby cover methods and structures within the scope of the claims themselves and their equivalents.

Claims

1. A planarization method for MoSi-based photomask substrates, characterized in that, Includes the following steps: A MoSi-based photomask substrate is provided; or, a photomask substrate is provided on which a MoSi thin film is deposited to form the MoSi-based photomask substrate. The MoSi-based photomask substrate is subjected to preliminary planarization treatment to obtain a first-polished MoSi-based photomask substrate; and The first-polished MoSi-based photomask substrate is then re-planarized to obtain a second-polished MoSi-based photomask substrate.

2. The planarization method for MoSi-based photomask substrates according to claim 1, characterized in that, The photomask substrate includes quartz glass and a silicon substrate.

3. The planarization method for MoSi-based photomask substrates according to claim 1, characterized in that, The thickness of the MoSi thin film is 90-100 nm.

4. The planarization method for MoSi-based photomask substrates according to claim 1, characterized in that, Preliminary planarization is performed using chemical mechanical polishing (CMP) technology. This preliminary planarization process includes: The MoSi-based photomask substrate is fixed on the stage of the CMP equipment; Setting chemical mechanical polishing parameters; and The CMP equipment is started to perform preliminary planarization treatment on the surface of the MoSi thin film on the MoSi-based photomask substrate to obtain the first-polished MoSi-based photomask substrate.

5. The planarization method for MoSi-based photomask substrates according to claim 4, characterized in that, The chemical mechanical polishing parameters include the primary polishing pressure, the primary polishing time, and the polishing disc rotation speed. The primary polishing pressure is 1-5 psi, the primary polishing time is 1-5 min, and the polishing disc rotation speed is 100-110 rpm.

6. The planarization method for MoSi-based photomask substrates according to claim 4, characterized in that, Also includes: A polishing slurry is prepared for use in a preliminary planarization process; the polishing slurry comprises silica abrasive and an oxidant, wherein the silica abrasive has a particle size of 50-60 nm and a concentration of 5-8 wt%, the oxidant is H2O2 with a concentration of 2-5 wt%, and the pH value of the polishing slurry is 9-9.

5.

7. The planarization method for MoSi-based photomask substrates according to claim 6, characterized in that, Also includes: The MoSi-based photomask substrate that has undergone primary polishing is cleaned to remove residual polishing slurry; as well as The cleaned and polished MoSi-based photomask substrate is then dried.

8. The planarization method for MoSi-based photomask substrates according to claim 7, characterized in that, Replanarization is performed using the ion beam polishing (IBP) process, which includes: The dried, first-polished MoSi-based photomask substrate is transferred to the IBP equipment; Setting ion beam polishing parameters; and The IBP equipment is started to perform a re-planarization process on the surface of the MoSi thin film on the first polished MoSi-based photomask substrate to obtain the second polished MoSi-based photomask substrate.

9. The planarization method for MoSi-based photomask substrates according to claim 8, characterized in that, The ion beam polishing parameters include ion beam energy, ion beam incident angle, secondary polishing time, and ion source. The ion beam energy is 100-500 eV, the ion beam incident angle is 30-60°, the secondary polishing time is 1-10 min, and the ion source is Ar⁺.

10. The planarization method for MoSi-based photomask substrates according to claim 8, characterized in that, Also includes: Clean the MoSi-based photomask substrate that has undergone secondary polishing.

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