EUV Lithography Glass Substrate Flatness Control
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Solution Overview
Problem
The challenge in EUV lithography is achieving a glass substrate with extremely low flatness and total thickness distribution for reflective photomasks, while maintaining defect-free surfaces to ensure accurate pattern transfer during semiconductor manufacturing, as existing methods struggle to simultaneously meet stringent flatness and thickness requirements.
Innovation Solution
A method involving preliminary polishing, measurement, and corrective polishing of the glass substrate's surfaces to achieve flatness and thickness within specific quality assurance areas, followed by finishing polishing to ensure surface roughness and defect reduction, using techniques like gas cluster ion beam etching to locally adjust the back surface and maintain surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing methods are used to reduce flatness and total thickness distribution, then manufacturing precision improves, but productivity deteriorates due to the need for multiple polishing steps and rework
Solution Approach 1:
The invention performs preliminary measurement of the glass substrate's thickness distribution and flatness before polishing, and uses this measurement information to guide the polishing process. This preliminary action allows the polishing to be targeted and efficient, avoiding unnecessary polishing steps and rework, thereby improving both manufacturing precision and productivity
Solution Approach 2:
The invention implements a feedback mechanism where the glass substrate is measured after polishing, and if the flatness and total thickness distribution do not meet specifications, the substrate is returned for rework. This feedback loop ensures high manufacturing precision while allowing efficient handling of non-conforming products through systematic rework procedures
2Manufacturing precision
If multiple polishing steps are performed to achieve required flatness and thickness distribution, then manufacturing precision improves, but device complexity increases due to multiple processing steps
Solution Approach 1:
The invention applies polishing treatment locally to specific areas of the glass substrate based on measurement results, rather than uniformly polishing the entire surface. This local quality approach reduces the number of polishing steps needed while achieving the required flatness and total thickness distribution, thereby simplifying the overall process complexity
Solution Approach 2:
By performing preliminary measurement and planning the polishing strategy before actual polishing, the invention determines the minimum necessary polishing steps required. This preliminary action prevents unnecessary polishing steps, reducing device complexity while maintaining manufacturing precision
3Manufacturing precision
If stringent flatness and thickness requirements are enforced, then manufacturing precision improves, but ease of manufacture deteriorates due to difficulty in meeting specifications
Solution Approach 1:
The invention implements comprehensive feedback through measurement after polishing, allowing real-time assessment of whether stringent specifications are met. This feedback mechanism provides clear guidance for adjustments and rework, making it easier to manufacture products that meet the stringent flatness and total thickness distribution requirements by systematically identifying and correcting deviations
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
This approach effectively reduces large defects and maintains low total thickness distribution and flatness, enabling high-quality optical member base materials for EUV lithography with improved productivity and cost reduction, even when stringent demands are not fully met.
Implementation Method 1
using techniques like gas cluster ion beam etching to locally adjust the back surface and maintain surface smoothness
Implementation Method 2
A method involving preliminary polishing, measurement, and corrective polishing of the glass substrate's surfaces to achieve flatness and thickness within specific quality assurance areas, followed by finishing polishing to ensure surface roughness and defect reduction
Data Source
AI summary
The present invention relates to a method for producing an optical member base material for EUVL, comprising performing the following in this order to obtain an optical member base material for EUVL: a preliminary-polishing step of preliminarily polishing a film forming surface and a back surface of the film forming surface of a glass substrate; a measuring step of measuring a total thickness distribution and a flatness of the glass substrate; and a corrective-polishing step of locally polishing only the back surface of the glass substrate depending on the measurement result of the measuring step.