Substrate Chuck Alignment Using Reference Mark Detection
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Solution Overview
Problem
In photolithographic processes, especially for manufacturing devices like semiconductor chips and MEMS, the alignment of optical systems with substrate chucks is prone to misalignment during chuck replacement, leading to detection field misalignment and difficulties in detecting alignment marks on substrates.
Innovation Solution
A method using a pattern forming apparatus with a movable stage, a holding unit with a fixed optical system for detecting alignment marks from the suction surface side of the substrate, and a detection unit for measuring a reference mark to ensure accurate alignment of alignment marks within the detection field, even during chuck replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical system for detecting alignment marks is provided on the substrate stage, then alignment marks can be detected from the substrate stage side, but misalignment of the chuck causes misalignment of the optical system and moves the detection field, making it difficult to detect alignment marks
Solution Approach 1:
A reference mark is introduced as an intermediary element that is detected by the optical system to calculate the actual position of the detection field. This reference mark serves as a mediator between the optical system and the substrate, allowing the system to compensate for chuck misalignment by calculating the detection field position based on reference mark detection results
Solution Approach 2:
The system implements a feedback mechanism where the detection unit detects the reference mark position, calculates the detection field position based on this feedback, and then determines the substrate position accordingly. This closed-loop feedback ensures that alignment mark detection remains accurate even when the chuck is misaligned
2Adaptability or versatility
If the chuck for sucking the substrate is replaceable, then different chucks can be used for different substrates, but misalignment of the replaced chuck causes misalignment of the optical system
Solution Approach 1:
The reference mark is pre-positioned on the chuck before substrate processing. When the chuck is replaced, the reference mark remains in place, allowing the system to pre-calculate the detection field position based on the reference mark. This preliminary positioning of the reference mark enables quick compensation for chuck replacement without requiring real-time alignment adjustments
Solution Approach 2:
The reference mark serves as a copy or proxy for the chuck's position information. Instead of directly measuring the chuck's alignment, the system detects the reference mark (a simplified copy of the positioning information) and uses this to infer the detection field position, thereby maintaining alignment precision despite chuck replacement
Data Source
AI summary
A method of disposing a substrate on a holding unit using a pattern forming apparatus which forms a pattern on the substrate, the pattern forming apparatus comprising: a stage, the holding unit removably attached to the stage and configured to suck and hold the substrate, an optical system, and configured to detect an alignment mark of the substrate from a suction surface side of the substrate, the optical system having plural optical elements, and a detection unit configured to detect a reference mark for measuring a position of a detection field of the optical system, the method comprising: detecting a position of the reference mark, and disposing the substrate on the holding unit using the detected position of the reference mark so that the alignment mark of the substrate detected from the suction surface side of the substrate by the optical system is disposed in the detection field.