Synthetic Quartz Substrate Machining for Shape Accuracy
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Solution Overview
Problem
The manufacturing of electronic grade synthetic quartz glass substrates with recesses, channels, or steps faces challenges in maintaining high accuracy of shape factors such as size, bottom wall thickness, and parallelism, which can lead to shape changes and residual stress issues during machining, affecting their performance in photomask and nanoimprint applications.
Innovation Solution
A method involving the use of synthetic quartz glass substrates with controlled birefringence, machining to form recesses, channels, or steps, and subsequent mirror finish polishing or wet etching to remove residual stress, ensuring minimal shape changes and high accuracy of shape factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If machining is performed to form recesses, channels, or steps in the substrate, then the functional requirements for photomask or NIL mold are met, but residual stress is generated causing shape factor changes (flatness and parallelism)
Solution Approach 1:
The substrate is pre-conditioned by controlling OH content and performing annealing before machining to minimize residual stress generation during subsequent machining operations, thereby maintaining shape factor accuracy while enabling functional features
Solution Approach 2:
The patent applies stress relief treatments (thermal or chemical) after machining to change the physical state of the substrate, removing residual stress and restoring flatness and parallelism to acceptable levels while preserving the machined functional features
2Manufacturing precision
If the substrate surface experiences substantial changes of flatness and parallelism before and after working, then resurfacing is required, but this increases process complexity and cost
Solution Approach 1:
The substrate undergoes preliminary annealing and OH content control before machining to pre-establish low residual stress conditions, preventing substantial shape changes during machining and eliminating the need for resurfacing operations
Solution Approach 2:
Stress relief treatments are applied after machining to change the physical state of the substrate, removing residual stress and restoring flatness and parallelism, thereby avoiding complex resurfacing operations
3Manufacturing precision
If high accuracy of shape factors is maintained throughout the process, then focal shift and pattern distortion are minimized, but the manufacturing process becomes more complex
Solution Approach 1:
The substrate is pre-conditioned by controlling OH content and performing annealing before machining to establish low residual stress conditions, maintaining shape factor accuracy throughout the process while using straightforward, well-established techniques
Solution Approach 2:
Stress relief treatments (thermal or chemical) are applied after machining to change the physical state of the substrate, removing residual stress and restoring flatness and parallelism to high accuracy levels without requiring complex additional processes
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 achieves high accuracy of shape factors with minimal changes in flatness and parallelism, reducing the risk of focal shifts or pattern distortions, and ensuring the substrates maintain their precision before and after machining, suitable for advanced applications like photolithography and nanoimprint lithography.
Implementation Method 1
wet etching the substrate with a glass etching solution until a work affected layer is removed, thereby removing the residual stress due to machining
Implementation Method 2
mirror finish polishing the machined surface, or by wet etching the substrate with a glass etching solution, to remove the residual stress due to machining
Data Source
AI summary
An electronic grade synthetic quartz glass substrate having a recess, channel or step is manufactured by machining at least one surface of a synthetic quartz glass substrate having a maximum birefringence of up to 3 nm/cm in its entirety to form a recess, channel or step, and removing the residual stress due to machining.