Sensor Wafer Edge Gap Measurement for Heater Pedestal Centering
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Solution Overview
Problem
Current methods for aligning semiconducting wafers on heating pedestals rely on manual eye alignment, leading to inaccuracies and require costly and time-consuming on-wafer uniformity tests to confirm proper centering, resulting in inefficient processing and reduced uniformity.
Innovation Solution
A sensor wafer with edge sensors is used to measure the gap distance between the sensor wafer and the annular wall of the pedestal, determining the center-point offset and enabling a placement controller to accurately position wafers, thereby improving centering accuracy and reducing processing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual eye alignment is used to center the substrate on the heating pedestal, then the alignment process is simple and quick, but the alignment accuracy is insufficient leading to non-uniform processing
Solution Approach 1:
A sensor wafer with edge sensors is introduced as an intermediary tool between the substrate and the heating pedestal. The sensor wafer measures the gap distance between the substrate edge and the annular wall, providing objective measurement data that replaces subjective visual alignment. This intermediary device enables precise centering determination without requiring complex alignment systems directly on the substrate.
2Reliability
If on-wafer uniformity tests are performed to confirm proper substrate centering, then the processing uniformity can be verified, but the testing process is time-consuming and costly
Solution Approach 1:
The sensor wafer performs preliminary centering measurement before the actual substrate processing. By measuring the gap distance between the substrate edge and the annular wall at multiple locations, the system determines the center-point offset in advance. This preliminary action verifies processing uniformity conditions without requiring time-consuming on-wafer uniformity tests, as the centering accuracy is confirmed prior to processing.
Solution Approach 2:
Instead of testing the actual substrate for uniformity, a sensor wafer is used as a copy or surrogate to perform the measurement. The sensor wafer replicates the centering measurement function without requiring expensive test substrates or lengthy processing cycles. The gap distance measurements on the sensor wafer provide sufficient information to verify centering accuracy.
3Manufacturing precision
If extensive on-wafer uniformity testing is conducted to ensure accurate centering, then the processing quality is improved, but the production efficiency decreases due to reduced throughput
Solution Approach 1:
The mechanical and time-intensive process of performing on-wafer uniformity tests is replaced by an electrical/electronic measurement system. Edge sensors on the sensor wafer electrically measure the gap distance to the annular wall, providing rapid centering data. This substitution of measurement methodology achieves accurate centering verification without reducing production throughput, as the electronic measurement is much faster than physical uniformity testing.
Data Source
AI summary
Embodiments disclosed herein include a method of determining the position of a sensor wafer relative to a pedestal. In an embodiment, the method comprises placing a sensor wafer onto the pedestal, wherein the sensor wafer comprises a first surface that is supported by the pedestal, a second surface opposite the first surface, and an edge surface connecting the first surface to the second surface, wherein a plurality of sensor regions are formed on the edge surface, and wherein the pedestal comprises a major surface and an annular wall surrounding the sensor wafer. In an embodiment, the method further comprises determining a gap distance between each of the plurality of sensor regions and the annular wall. In an embodiment, the method may further comprise determining a center-point offset of a center-point of the sensor wafer relative to a center point of the annular wall from the gap distances.