A method for repairing defects on a phase shift blank mask substrate and a repair material

Abstract

The present application relates to the technical field of blank mask substrate defect repair, and in particular to a phase shift blank mask substrate defect repair method and a repair material, wherein the blank substrate mark-free defect classification is realized through DUV dark field interference chromatic aberration positioning, the protrusion milling, the pit repair and the low-temperature solidification are completed in the same sealed cavity, and the in-situ solid-phase crystallization is realized by using the double-form repair material and the interface modification additive. The present application solves the problems of difficult positioning, process fragmentation and large film layer damage in the prior art, realizes the accurate repair of nanoscale defects, the matching degree of the repair layer and the substrate optical performance is greater than 95%, the repair working hours are shortened by 90%, and is suitable for panel, packaging and semiconductor industry fields.

Description

Technical Field

[0001] This invention relates to the field of blank photomask substrate defect repair technology, and in particular to a method and repair material for repairing defects in phase-shifted blank photomask substrates. Background Technology

[0002] The phase-shifted blank photomask substrate is the core carrier of the photolithography process, and the quality of the film layer determines the imaging accuracy and lifespan of the photomask. Substrate manufacturing can produce black defects (light-blocking bumps) and white defects (light-transmitting pits). When defects exceed specifications, rework repair is required to reduce production costs.

[0003] Currently, the mainstream phase-shift blanking mask substrate is a MoSi+Cr bilayer heterostructure, and the corresponding defects can be divided into three categories: defects only in the Cr surface layer, defects only in the MoSi inner layer, and MoSi / Cr penetrating double-layer pits. Existing repair techniques have the following drawbacks: Positioning difficulties: Traditional optical inspection relies on photolithographic marks or graphic contours for positioning. When there are no reference marks on the blank substrate, manual blind scanning is required. Tiny defects of 5~20nm are difficult to capture, resulting in poor positioning accuracy. Process fragmentation: Protrusion removal and pit repair need to be carried out in different steps in different equipment. The cross-cavity transfer of workpieces is prone to secondary pollution. Furthermore, processes such as FIB, laser, and CMP are independent of each other and cannot be adapted to the double-layer heterogeneous structure. Significant film damage: FIB relies on gallium ion implantation for film formation, while lasers and high-energy electron beams rely on high-temperature degradation of precursors, leading to lattice damage and high-temperature phase transitions in MoSi films. Poor material compatibility: Existing repair materials cannot be simultaneously adapted to double-layer film repair, the Cr / MoSi interface has poor adhesion, interlayer delamination, and high impurity content; Photoresist repair defects: The whole-wafer rework and recoating process is wasteful of materials, micro-drop repair has large step differences and thermal diffusion and overflow problems, and laser / ion beam etching to remove raised photoresist defects can easily burn adjacent areas.

[0004] Therefore, developing a defect repair technology that is adaptable to blank substrates, low-damage, closed-loop, and has high material matching is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, the first aspect of the present invention provides a method for repairing defects in a phase-shifted blank photomask substrate, comprising at least the following steps: S1. The phase-shifted blank photomask substrate is inspected using the DUV dark field interferometric imaging full-domain scanning method to identify and distinguish between protrusion defects and pit defects. S2. Place the phase-shifted blank photomask substrate in a sealed inert atmosphere cavity to maintain a constant temperature and inert environment in the cavity; use a micro probe to perform targeted milling to remove the protrusion defects in the cavity to complete the protrusion defect repair. S3. Fill the pit defect with repair material and cure it by electron beam irradiation to complete the pit defect repair; S4. Perform surface roughness and reflectivity tests on the phase-shifted blank photomask substrate after step S3. After passing the tests, complete the repair.

[0006] When DUV (deep ultraviolet) light waves irradiate a substrate, the difference in optical refractive index between defective and normal areas causes interference chromatic aberration, such as phase shift of reflected light from raised areas and phase shift of transmitted light from pitted areas. This chromatic aberration signal is captured by dark-field imaging, and combined with software algorithms, defect types and coordinates are automatically classified. This technology, based on the principle of optical interference, does not rely on traditional photolithography markings and fundamentally solves the industry problem of lack of reference positioning for blank substrates.

[0007] In some implementations, the DUV dark-field interferometric imaging global scanning utilizes the optical interference chromatic aberration between the phase-shifted thin film and the defect region to distinguish between protruding defects and pitted defects.

[0008] In some embodiments, in step S2, the inert atmosphere is an argon atmosphere, and the constant temperature of the cavity is 80~120℃. As an example, the constant temperature of the cavity can be 80℃, 90℃, 100℃, 110℃, 120℃, or any value within the range of 80~120℃.

[0009] In some embodiments, step S2 involves using an AFM (Atomic Force Microscopy) microprobe for point milling. The milling depth is controlled in real-time using AFM in-situ depth measurement to avoid over-milling and damage to the basement membrane.

[0010] In some embodiments, in step S3, the material supply path is switched according to the size of the pit defect, and repair material is quantitatively supplied to the pit location.

[0011] In some embodiments, the repair material has two application forms: aerosol and micro-paste, and satisfies at least one of the following characteristics: (1) For pit defects with a size <0.2μm, spray the repair material in the form of aerosol; (2) For pit defects with a size of 0.3~5μm, apply micro paste-like repair material to fill the pit.

[0012] In some embodiments, in step S3, electron beam irradiation curing satisfies at least one of the following characteristics: (1) The energy of the electron beam is 400~420eV; (2) The temperature for electron beam irradiation curing is 90~120℃; (3) The time for electron beam irradiation curing is 80~120 min.

[0013] Optionally, the energy of the electron beam is 400~420eV. As an example, the energy of the electron beam can be 400eV, 410eV, 420eV, or any value within the range of 400~420eV.

[0014] Optionally, the electron beam irradiation curing temperature is 90~120℃. As an example, the electron beam irradiation curing temperature can be 90℃, 100℃, 110℃, 120℃, or any value within the range of 90~120℃.

[0015] Optionally, the electron beam irradiation curing time is 80~120 min. As an example, the electron beam irradiation curing time can be 80 min, 90 min, 100 min, 110 min, 120 min, or any value within the range of 80~120 min.

[0016] This invention employs a low-energy electron beam (<500eV) and a low-temperature inert environment (≤120℃). The low-energy electron beam provides sufficient energy for the pyrolysis and volatilization of the organic carrier (<120℃), but not enough to destroy the substrate lattice. At low temperature, the interface-modifying agent guides the metal powder in the repair material to directly crystallize through solid-phase diffusion, forming a crystal structure homogeneous with the substrate. This technology transforms "high-energy pyrolysis deposition" into "low-temperature desolventizing + in-situ solid-phase crystallization," fundamentally avoiding film damage caused by ion implantation and high-temperature pyrolysis.

[0017] In some embodiments, step S4 includes: performing surface roughness and reflectivity detection on the phase-shifted blank photomask substrate after step S3; repeating step S3 and subsequent operations on unqualified points until the detection is qualified; repeating the full-area scan of step S1 to confirm that the overall repair effect is complete.

[0018] This invention integrates the entire process of positioning, milling, repair, and inspection into a single sealed cavity, avoiding the fragmented process of multiple cavity openings and material loading / unloading in traditional separate equipment operations. AFM probes control the milling depth in real time, and in-situ closed-loop inspection (surface roughness + reflectivity) dynamically adjusts the material replenishment amount, forming a closed-loop control chain of "inspection-repair-re-inspection," ensuring zero pollution and high precision in the repair process.

[0019] A second aspect of the present invention provides a repair material for the above-described method for repairing defects in a phase-shifted blank photomask substrate, the repair material comprising metal powder, a volatile organic carrier, and an interface modifier.

[0020] In some embodiments, the repair material comprises, by weight percentage, 55-88% metal powder, 8-43% volatile organic carrier, and the remainder being interface modifiers.

[0021] The repair material provided by this invention is composed of high-purity metal powder, low-temperature volatile organic carrier and interface modifier. By adjusting the powder ratio and carrier content, the material viscosity is controlled and formulated into two application forms: aerosol or micro paste. After the carrier is removed at low temperature, the powder crystallizes in situ under the action of interface modifier, forming a repair layer with the same physicochemical properties and crystal phase as the substrate.

[0022] In some embodiments, the metal powder includes at least one of Mo powder, Si powder, and Cr powder.

[0023] Optionally, the repair material includes Mo powder and Si powder, wherein the mass ratio of Mo powder to Si powder is 5-40:30-50.

[0024] Optionally, the repair material includes Mo powder, Si powder and Cr powder, wherein the mass ratio of Mo powder, Si powder and Cr powder is 10-30:20-40:20-40.

[0025] In some embodiments, the volatile organic carrier includes at least one of isopropanol and alkanes.

[0026] Optionally, the volatile organic carrier includes isopropanol and alkanes.

[0027] In some embodiments, the interface modifying agent includes an organosilane interface modifying agent.

[0028] Beneficial effects: This invention provides a method and repair material for repairing defects in a phase-shifted blank photomask substrate, which has the following advantages: (1) The present invention uses the DUV dark field interferometric imaging full-domain scanning method to detect phase-shifted blank photomask substrates, which can accurately capture tiny defects. The positioning error is much lower than that of manual blind scanning, and it is suitable for various blank substrates without patterns.

[0029] (2) This invention integrates the entire process of identification, positioning, milling, repair and testing into a single sealed cavity, avoiding the process of breaking the cavity and loading and unloading multiple times in the traditional separate equipment operation.

[0030] (3) The present invention adopts low temperature in-situ solid-state crystallization technology, with mild conditions of ≤120℃ low temperature and ≤500eV low energy, without high temperature thermal phase change and ion implantation damage, the intact film layer is not affected, and secondary phase defects are avoided.

[0031] (4) The optical performance matching degree between the repair layer and the substrate after in-situ crystallization of the present invention is >95%, and the repair time is shortened by 90%; and the dual-morphology repair material covers the full-size defects from nanometer to micrometer, without the need for frequent material replacement.

[0032] (5) The in-situ closed-loop re-inspection of the present invention can correct over-repair and under-repair problems in real time. The scrap rate of over-repair / under-repair is much lower than that of the existing process, which greatly reduces the cost of rework.

[0033] (6) This invention has no harmful impurities remaining and meets the stringent cleanliness requirements of high-end EUV / DUV blank masks. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Experimental methods not specifically specified in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the solvent for the solutions involved in this invention is water; the room temperature is 25°C; and the raw materials, consumables, and equipment used are all commercially available.

[0035] In the following examples, the purity of the metal powder is ≥5N.

[0036] Example 1 (Repairing MoSi Layers) The first aspect of this example provides a method for repairing defects in a phase-shifted blank photomask substrate, including the following steps: S1. The phase-shifted blank photomask substrate is inspected using the DUV dark field interferometric imaging full-domain scanning method. The optical interference color difference between the phase-shifted thin film and the defect area is used to identify and distinguish between protruding defects and pit defects. S2. Place the phase-shifted blank photomask substrate in a sealed inert argon atmosphere chamber and maintain the chamber at a constant temperature of 100°C. Use an AFM micro probe to perform targeted milling to remove the protrusion defects within the chamber to complete the protrusion defect repair. S3. Keep the substrate stationary, switch the aerosol supply branch, spray the aerosol repair material onto the pit defect, and use a 420eV low-energy electron beam and 100℃ electric irradiation to cure for 100 minutes to form a repair layer to complete the repair of the pit defect (0.01~0.2um nano-micropore defect). S4. Perform surface roughness and reflectivity detection on the phase-shifted blank photomask substrate after step S3. Repeat step S3 and subsequent operations for unqualified points until the detection is qualified. Then repeat the full-area scan of step S1 to confirm that the overall repair effect is complete.

[0037] The second aspect of this example provides an aerosol remediation material, which, by weight percentage, comprises 30% Mo powder, 35% Si powder, 32% volatile organic carrier, and 3% interface modifier.

[0038] The volatile organic carriers include isopropanol and alkanes.

[0039] The preparation method of the aerosol repair material is as follows: first, add the interface modification agent to the volatile organic carrier and stir and mix at room temperature; then add Mo powder and Si powder respectively, disperse at high speed to form a mixed liquid, and atomize the mixed liquid under high pressure to form the aerosol repair material.

[0040] Example 2 (Repairing the MoSi layer) The first aspect of this example provides a method for repairing defects in a phase-shifted blank photomask substrate, including the following steps: S1. The phase-shifted blank photomask substrate is inspected using the DUV dark field interferometric imaging full-domain scanning method. The optical interference color difference between the phase-shifted thin film and the defect area is used to identify and distinguish between protruding defects and pit defects. S2. Place the phase-shifted blank photomask substrate in a sealed inert argon atmosphere chamber and maintain the chamber at a constant temperature of 100°C. Use an AFM micro probe to perform targeted milling to remove the protrusion defects within the chamber to complete the protrusion defect repair. S3. Keep the substrate stationary, switch the micro paste supply branch, apply micro paste repair material to the pit defect, and use a 420eV low-energy electron beam and 100℃ electric irradiation to cure for 100 minutes to form a repair layer to complete the repair of the pit defect (0.3-5μm pit defect). S4. Perform surface roughness and reflectivity detection on the phase-shifted blank photomask substrate after step S3. Repeat step S3 and subsequent operations for unqualified points until the detection is qualified. Then repeat the full-area scan of step S1 to confirm that the overall repair effect is complete.

[0041] The second aspect of this example provides a micro-paste-type repair material, which, by weight percentage, comprises 25% Mo powder, 45% Si powder, 28% volatile organic carrier, and 2% interface modifier.

[0042] The volatile organic carriers include isopropanol and alkanes.

[0043] The preparation method of the micro-paste-type repair material is as follows: first, add the interface modification agent to the volatile organic carrier and stir and mix at room temperature, then add Mo powder and Si powder respectively, and disperse at high speed to prepare the micro-paste-type adhesive repair material.

[0044] Example 3 (Repair of MoSi / Cr penetrating double-layer pits) The first aspect of this example provides a method for repairing defects in a phase-shifted blank photomask substrate, including the following steps: S1. The phase-shifted blank photomask substrate is inspected using the DUV dark field interferometric imaging full-domain scanning method. The optical interference color difference between the phase-shifted thin film and the defect area is used to identify and distinguish between protruding defects and pit defects. S2. Place the phase-shifted blank photomask substrate in a sealed inert argon atmosphere chamber and maintain the chamber at a constant temperature of 100°C. Use an AFM micro probe to perform targeted milling to remove the protrusion defects within the chamber to complete the protrusion defect repair. S3. Keep the substrate stationary, switch the aerosol supply branch, spray the aerosol repair material onto the pit defect, and use a 400eV low-energy electron beam and 100℃ electric irradiation to cure for 100 minutes to form a repair layer and complete the repair of the pit defect (0.005-0.2μm pit defect). S4. Perform surface roughness and reflectivity detection on the phase-shifted blank photomask substrate after step S3. Repeat step S3 and subsequent operations for unqualified points until the detection is qualified. Then repeat the full-area scan of step S1 to confirm that the overall repair effect is complete.

[0045] The second aspect of this example provides an aerosol remediation material, which, by weight percentage, comprises 20% Mo powder, 25% Si powder, 35% Cr powder, 18% volatile organic carrier, and 2% interface modifier.

[0046] The volatile organic carriers include isopropanol and alkanes.

[0047] The preparation method of the aerosol repair material is as follows: first, add the interface modification agent to the volatile organic carrier and stir and mix at room temperature; then add Mo powder, Si powder and Cr powder respectively, disperse at high speed to form a mixed liquid, and atomize the mixed liquid under high pressure to form the aerosol repair material.

[0048] Example 4 (Repair of MoSi / Cr penetrating double-layer pits) The first aspect of this example provides a method for repairing defects in a phase-shifted blank photomask substrate, including the following steps: S1. The phase-shifted blank photomask substrate is inspected using the DUV dark field interferometric imaging full-domain scanning method. The optical interference color difference between the phase-shifted thin film and the defect area is used to identify and distinguish between protruding defects and pit defects. S2. Place the phase-shifted blank photomask substrate in a sealed inert argon atmosphere chamber and maintain the chamber at a constant temperature of 100°C. Use an AFM micro probe to perform targeted milling to remove the protrusion defects within the chamber to complete the protrusion defect repair. S3. Keep the substrate stationary, switch the micro paste supply branch, apply micro paste repair material to the pit defect, and cure it with 400eV low-energy electron beam and 100℃ electric irradiation for 100min to form a repair layer to complete the repair of pit defects (0.005-0.2μm pit defects); S4. Perform surface roughness and reflectivity detection on the phase-shifted blank photomask substrate after step S3. Repeat step S3 and subsequent operations for unqualified points until the detection is qualified. Then repeat the full-area scan of step S1 to confirm that the overall repair effect is complete.

[0049] The second aspect of this example provides a micro-paste-type repair material, which, by weight percentage, comprises 25% Mo powder, 30% Si powder, 35% Cr powder, 8% volatile organic carrier, and 2% interface modifier.

[0050] The volatile organic carriers include isopropanol and alkanes.

[0051] The preparation method of the micro-paste-type repair material is as follows: first, add the interface modification agent to the volatile organic carrier and stir and mix at room temperature, then add Mo powder, Si powder and Cr powder respectively, and disperse at high speed to prepare the micro-paste-type repair material.

[0052] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for repairing defects in a phase-shifted blank photomask substrate, characterized in that, At least the following steps are included: S1. The phase-shifted blank photomask substrate is inspected using the DUV dark field interferometric imaging full-domain scanning method to identify and distinguish between protrusion defects and pit defects. S2. Place the phase-shifted blank photomask substrate in a sealed inert atmosphere cavity to maintain a constant temperature and inert environment in the cavity; use a micro probe to perform targeted milling to remove the protrusion defects in the cavity to complete the protrusion defect repair. S3. Fill the pit defect with repair material and cure it by electron beam irradiation to complete the pit defect repair; S4. Perform surface roughness and reflectivity tests on the phase-shifted blank photomask substrate after step S3. After passing the tests, complete the repair.

2. The method for repairing defects in a phase-shifted blank photomask substrate according to claim 1, characterized in that, The DUV dark field interferometry imaging global scanning utilizes the optical interference color difference between the phase-shifted thin film and the defect region to distinguish between protruding defects and pitted defects.

3. The method for repairing defects in a phase-shifted blank photomask substrate according to claim 1, characterized in that, In step S2, the inert atmosphere is argon atmosphere, and the constant temperature of the cavity is 80~120℃.

4. The method for repairing defects in a phase-shifted blank photomask substrate according to claim 1, characterized in that, In step S2, AFM micro probes are used for fixed-point milling.

5. The method for repairing defects in a phase-shifted blank photomask substrate according to claim 1, characterized in that, The repair material has two application forms: aerosol and micro-paste, and meets at least one of the following characteristics: (1) For pit defects with a size <0.2μm, spray the repair material in the form of aerosol; (2) For pit defects with a size of 0.3~5μm, apply micro paste-like repair material to fill the pit.

6. The method for repairing defects in a phase-shifted blank photomask substrate according to claim 1, characterized in that, In step S3, electron beam irradiation curing satisfies at least one of the following characteristics: (1) The energy of the electron beam is 400~420eV; (2) The temperature for electron beam irradiation curing is 90~120℃; (3) The time for electron beam irradiation curing is 80~120 min.

7. The method for repairing defects in a phase-shifted blank photomask substrate according to claim 1, characterized in that, Step S4 includes: performing surface roughness and reflectivity detection on the phase-shifted blank photomask substrate after step S3; repeating step S3 and subsequent operations on unqualified points until the detection is qualified; repeating the full-area scan of step S1 to confirm that the overall repair effect is complete.

8. A repair material, characterized in that, The method for repairing defects in a phase-shifted blank photomask substrate according to any one of claims 1 to 7, wherein the repair material comprises metal powder, volatile organic carrier, and interface modifier.

9. The repair material according to claim 8, characterized in that, The metal powder includes at least one of Mo powder, Si powder, and Cr powder.

10. The repair material according to claim 8, characterized in that, The volatile organic carrier includes at least one of isopropanol and alkanes.