Substrate Mark Measurement Autofocus Offset Control
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Solution Overview
Problem
In substrate mark position measurement, existing techniques face challenges in achieving high accuracy and throughput due to variations in substrate thickness, leading to increased measurement time and degraded throughput when the preset substrate thickness is inappropriate.
Innovation Solution
A measurement apparatus that includes a wafer alignment detector and an autofocus detector, which determines the starting point of the image autofocus operation by selecting the distance with less variation between substrates, either from the upper or lower surface to the mark, using refractive index information to adjust the focus position, thereby reducing the search range and improving measurement speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the starting point of image autofocus operation is determined based on preset substrate thickness amount, then the measurement operation can be performed, but the measurement time increases and throughput degrades when there is large variation in actual substrate thickness
Solution Approach 1:
The invention performs preliminary measurement of the substrate surface position using a substrate surface detection system before the image autofocus operation. This preliminary action provides accurate starting point information that accounts for actual substrate thickness variations, eliminating the need for broad search ranges and reducing measurement time while maintaining focus accuracy.
Solution Approach 2:
The invention uses feedback from the substrate surface detection system to dynamically adjust the starting point of the image autofocus operation. The detected substrate surface position is fed back to calculate an appropriate offset, creating a closed-loop system that adapts to individual substrate variations and optimizes measurement efficiency.
2Adaptability or versatility
If the search range of image autofocus operation is expanded to accommodate substrate thickness variation, then measurement coverage is improved, but measurement time increases
Solution Approach 1:
The substrate surface detection system performs preliminary measurement to determine the actual substrate surface position before the image autofocus search begins. This preliminary action provides accurate information about substrate thickness variations, allowing the search range to be appropriately limited rather than expanded, thus reducing measurement time while maintaining adaptability to different substrates.
Solution Approach 2:
The invention dynamically changes the search parameters (starting point and search range) of the image autofocus operation based on the detected substrate surface position and calculated offset. By adjusting these parameters according to actual substrate conditions rather than using fixed preset values, the system adapts to substrate variations without requiring expanded search ranges.
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 enhances the accuracy and throughput of substrate mark position measurement by selecting the appropriate starting point based on the distance with less variation, ensuring rapid and precise focus positioning.
Implementation Method 1
an autofocus detector for measuring a height position of the first surface of the substrate
Implementation Method 2
a wafer alignment detector including a light reception system that receives reflected light from the mark
Data Source
Figure 1
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AI summary
A measurement apparatus that measures a position of a mark (19) formed between a first surface and a second surface on a side opposite to the first surface of a substrate (3) is provided. The apparatus includes a stage (4) configured to hold and move the substrate, a first detector (16) configured to detect an image of the mark, a second detector (41) configured to detect a height position of the first surface, and a processor (P) configured to determine, based on the height position of the first surface detected by the second detector, an offset amount used to set the focus of the first detector to the mark. The processor includes a first mode in which the offset amount is determined based on a first distance set as a distance from the first surface to the mark, and a second mode in which the offset amount is determined based on a second distance set as a distance from the second surface to the mark.