Step-and-Scan Exposure Apparatus Edge Shot Focusing
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Solution Overview
Problem
In microdevice manufacturing through photolithography, step-and-scan exposure apparatuses face challenges in accurately focusing the mask pattern on substrates, especially for edge shots where portions are outside the substrate edge, leading to increased variations in layer width and MR height due to imperfect mechanical precision and complex detection processes.
Innovation Solution
The exposure method and apparatus synchronize the movement of the mask and substrate while shifting the exposure region from one end to the other within each pattern projection region, using a detection device to adjust the substrate's position along the optical axis, ensuring precise focusing even for regions partially outside the substrate edge, and maintaining consistent scanning directions among adjacent shots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If step-and-scan exposure is performed with conventional detection methods, then exposure of multiple shots can be completed, but the substrate surface location cannot be accurately detected for edge shots, leading to poor focusing
Solution Approach 1:
The patent introduces a new detection dimension by measuring the substrate surface location at multiple positions (both inside and outside the substrate edge) and combining these measurements. The detection device captures surface location information in different spatial dimensions to calculate the actual substrate surface location, overcoming the limitation of conventional single-point detection methods that fail at substrate edges.
Solution Approach 2:
The patent employs an intermediary calculation process that uses the detected surface locations at multiple positions as intermediate data points. By calculating the average or interpolated value of these intermediate measurements, the system derives the accurate substrate surface location even for edge shots where direct detection is insufficient.
2Productivity
If edge shots are exposed without accurate substrate surface detection, then exposure can be completed quickly, but variations in layer width and MR height increase
Solution Approach 1:
The patent performs preliminary detection of the substrate surface location at multiple positions before the actual exposure process. By预先 (in advance) calculating the accurate substrate surface location using these preliminary measurements, the system ensures that focusing is optimized before exposure begins, preventing variations in layer width and MR height without slowing down the overall production rate.
3Manufacturing precision
If mechanical precision is improved to reduce variations, then focusing accuracy increases, but device complexity and cost increase
Solution Approach 1:
The patent replaces reliance on high-precision mechanical positioning with an optical/electronic detection and calculation system. Instead of improving mechanical precision to achieve accurate focusing, the system uses detection devices to measure substrate surface locations and calculates the required focus position, substituting mechanical complexity with computational simplicity.
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 reduces variations in layer width and MR height across microdevices by enabling precise detection and adjustment of the substrate surface, even for edge regions, thereby improving the consistency and quality of microdevice manufacturing.
Implementation Method 1
a detection device for detecting a location of a surface of the substrate along a direction of an optical axis of the optical projection system
Implementation Method 2
exposing a substrate by projecting a pattern formed in a mask onto a plurality of regions in the substrate one by one by means of a scanning system
Data Source
AI summary
For each of pattern projection regions, a mask and a substrate are moved in synchronization with each other in an X direction while projecting a portion of a mask pattern through an optical projection system onto a portion of the pattern projection region. An exposure region is thereby shifted from one of two ends of the pattern projection region toward the other end, the two ends being opposed to each other in the X direction. If the pattern projection region is a peripheral projection region that has a portion located outside the edge of the substrate, of the two ends of the region opposed to each other in the X direction, the exposure region is shifted from the one end that is greater in length of a portion laid over the substrate toward the other end.