Mask Blank Substrate Corner Design for Flatness Control
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Solution Overview
Problem
Conventional methods for selecting mask substrates for exposure systems require extensive time and labor to ensure flatness and position accuracy, which is critical for achieving the 65 nm design rule in semiconductor manufacturing, as they need to simulate the flatness after chucking and often result in substrate deformation leading to pattern transfer defects.
Innovation Solution
A mask blank substrate with specific flatness conditions, where the flatness of a 2 mm inward area from the outer peripheral end surface is 0.6 μm or less, and at least three corner portions have a rising shape, allowing for accurate chucking without simulation, enhancing position accuracy and reducing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to select mask substrates, then flatness information can be acquired, but much time and labor are required for simulation and measurement
Solution Approach 1:
The patent applies preliminary action by pre-forming specific corner shapes (rising shapes) on the mask substrate before chucking. This preliminary shaping of corners compensates for deformation that would occur during chucking, eliminating the need for time-consuming simulations and repeated measurements to achieve the required flatness after mounting
Solution Approach 2:
The patent changes the geometric parameters of the substrate corners by forming rising shapes with specific height ranges (0.01-0.06 μm). This parameter modification allows the substrate to maintain required flatness after chucking without requiring extensive measurement and simulation processes
2Productivity
If mask substrates are chucked on the mask stage, then exposure can be performed, but substrate deformation occurs leading to position accuracy degradation
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming rising shapes at the corners of the mask substrate. These pre-formed corner shapes counteract the deformation forces that occur during chucking, preventing position accuracy degradation and maintaining pattern transfer precision without sacrificing production efficiency
Solution Approach 2:
The patent applies local quality by modifying only the corner portions of the substrate while keeping the central flatness measurement area unchanged. The rising shapes are formed specifically at corners with heights controlled within 0.01-0.06 μm, providing localized compensation for chucking-induced deformation without affecting the overall flatness requirements
Data Source
AI summary
In a mask blank substrate to be chucked by a mask stage of an exposure system, the flatness of a rectangular flatness measurement area excluding an area of 2 mm inward from an outer peripheral end surface on a main surface of the mask blank substrate on its side to be chucked by the mask stage is 0.6 μm or less, and at least three of four corner portions of the flatness measurement area each have a shape that rises toward the outer peripheral side.