Mask Blank Substrate Processing Using Catalyst Referred Etching
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Solution Overview
Problem
Conventional methods fail to achieve high smoothness and low-defect quality on mask blank substrates required for EUV exposure, particularly with surface roughness below 0.08 nm Rms, and existing substrate processing techniques are not suitable for EUV exposure applications, leading to issues with defect inspection and substrate quality.
Innovation Solution
A mask blank substrate processing device and method incorporating Catalyst Referred Etching (CARE) with a catalytic surface plate and physical cleaning, using pure water as processing fluids, to achieve high smoothness and low-defect quality by removing foreign matters and microscopic protrusions, while maintaining substrate material integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing and cleaning methods are used on mask blank substrates, then the substrate can be processed with existing equipment, but the surface roughness cannot achieve the required 0.08 nm Rms or below for EUV exposure
Solution Approach 1:
The invention changes the chemical parameters of the processing fluid from conventional acids to pure water, and changes the mechanical parameters of the processing method from simple polishing to CARE (Chemical-Assisted Rubbing Etching). This combination achieves surface roughness of 0.08 nm Rms or below while maintaining processability through a systematic processing flow.
Solution Approach 2:
The invention introduces a catalytic surface plate as an intermediary that facilitates the CARE process. The catalytic surface plate with specific surface area (0.1 to 10 m²) acts as a mediator between the pure water processing fluid and the mask blank substrate, enabling the chemical-assisted rubbing etching that achieves the required surface smoothness.
2Measurement precision
If high sensitivity defect inspection is performed to detect minute defects, then defect detection capability is improved, but false defects occur due to background noise from surface roughness
Solution Approach 1:
The invention performs preliminary surface treatment using CARE and physical cleaning methods before defect inspection. By pre-reducing surface roughness to 0.08 nm Rms or below, the substrate is prepared in advance to minimize background noise, enabling subsequent high-sensitivity defect inspection without false positives.
3Manufacturing precision
If Catalyst Referred Etching is used to achieve high smoothness, then surface roughness is reduced to 0.08 nm Rms or below, but the processing complexity increases
Solution Approach 1:
The invention segments the surface treatment process into distinct stages: CARE processing stage and physical cleaning stage. The CARE processing is further divided into sub-stages with different catalytic surface plate surface areas. This segmentation allows complex surface treatment to be achieved through manageable, sequential steps rather than a single complex process.
4Reliability
If multiple processing steps are performed to remove foreign matters and achieve low-defect quality, then defect quality is improved, but processing time increases
Solution Approach 1:
The invention merges multiple functions into integrated processing steps. The CARE process simultaneously achieves surface smoothing and foreign matter removal. The physical cleaning step combines ultrasonic cleaning and brush cleaning to remove both particles and organic substances in one integrated sequence. This merging reduces total processing time while maintaining low-defect quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method provides a mask blank substrate with high-level smoothness and low-defect quality, suitable for EUV exposure, reducing surface defects and enhancing the quality of multilayer reflective films and transfer masks, thereby meeting stringent semiconductor design rules.
Implementation Method 1
causing a principal surface of a crystalline substrate such as SiC and a catalyst to be close to, or in contact with each other with a processing liquid such as an acidic liquid therebetween, and using active species produced from molecules in the processing liquid adsorbed to the catalyst, selectively removing, by mechanical processing and polishing, microscopic protrusions (machining-affected layer) generated as a crystal defect on the principal surface
Data Source
AI summary
Provided are a mask blank substrate processing device, a mask blank substrate processing method, a mask blank substrate fabrication method, a mask blank fabrication method, and a transfer mask fabrication method, for surface processing a mask blank substrate such that a high-level smoothness and a low-defect quality are satisfied. A mask blank substrate processing device (1) comprises: substrate support means (3) for supporting a substrate (Y); a catalytic surface plate (4) comprising a catalytic face (4a) which is positioned opposite the principal surface of the substrate (Y); relative movement means (5) for causing the catalytic face (4a) and the principal surface to move relative to each other in a state of being either in contact or in close proximity; first processing fluid supply means (6) which supplies a first processing fluid for CARE to the principal surface; and physical cleaning means (7) for removing foreign matter which has adhered to the principal surface from the principal surface, using a physical action.