Light Shielding Plate Positioning for Exposure Apparatus
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Solution Overview
Problem
Existing exposure apparatuses face challenges in accurately positioning a light shielding plate due to misalignment between the drive reference position and the exposure reference, leading to inconsistent shielding of the peripheral region on a wafer, which affects the precision of solder ball formation in flip-chip mounting processes.
Innovation Solution
An exposure apparatus with an optical system, including a light shielding plate that is rotatably and shift-drivably positioned based on relative position information between the optical axis and the axis of rotation, ensures precise alignment and positioning of the light shielding plate to maintain consistent shielding of the peripheral region during the exposure process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light shielding plate is arranged on a wafer to shield the peripheral region, then the shielding function is achieved, but the light shielding plate has to be retracted each time the wafer is replaced, causing restrictions in space and throughput
Solution Approach 1:
The light shielding plate is extracted from the wafer surface and relocated to the projection optical system side, specifically to a position optically conjugate with the wafer periphery. This allows the shielding function to be maintained without interfering with wafer handling operations, eliminating the need to retract the shield during wafer replacement.
Solution Approach 2:
The patent introduces an intermediary positioning mechanism that places the light shielding plate at an optically conjugate position rather than directly on the wafer. This intermediary position serves as a mediator that maintains the shielding effect while avoiding conflicts with wafer replacement operations, thereby improving throughput.
2Reliability
If the light shielding plate is positioned based on the position of the periphery shot region on the wafer, then the peripheral region shielding is achieved, but misalignment between the drive reference position and the actual center position of the wafer causes displacement errors
Solution Approach 1:
The patent implements a feedback mechanism where the actual position of the wafer center is detected and used to adjust the drive reference position of the light shielding plate. By acquiring information on the relative position between the drive reference position and the wafer center, and feeding this information back to correct the positioning, the system eliminates displacement errors caused by initial misalignment.
Solution Approach 2:
The patent changes the positioning parameter from a fixed drive reference position to a dynamically adjusted reference that accounts for the actual wafer center position. By modifying the reference position parameter based on detected misalignment, the system achieves accurate positioning of the light shielding plate despite initial setup errors.
Data Source
AI summary
An exposure apparatus including an optical system, includes a light shielding plate, a rotational drive unit configured to rotatably drive the light shielding plate around an axis of rotation along an optical path in the optical system, a shift drive unit configured to shift-drive the light shielding plate in a direction intersecting the axis of rotation, an acquisition unit configured to acquire information relating to a relative position between a reference axis serving as a reference when a pattern image is projected on a substrate by the optical system and the axis of rotation, and a control unit configured to control the rotational drive unit and the shift-drive unit so that, when projecting the pattern image on a circumferential portion near an outer edge of the substrate, the light shielding plate is positioned at a predetermined position based on the information relating to the relative position.