Wafer Angular Alignment Using Die-Edge Optical Measurement
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Solution Overview
Problem
Existing semiconductor fabrication methods face challenges in achieving precise angular alignment of wafers during ion exposure processes, leading to non-uniformity within the wafer and variations between wafers, which affect device performance and increase defects.
Innovation Solution
A method and apparatus that utilize a camera to measure the position of integrated circuit dies on a wafer, determine angular displacement, and rotate the platen to align the wafer with respect to the ion beam, ensuring accurate angular alignment and uniform ion distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional wafer alignment methods are used, then the alignment process is simpler, but the angular alignment precision is insufficient leading to non-uniform ion distribution
Solution Approach 1:
The patent replaces traditional mechanical alignment systems with an optical measurement system using a camera to capture wafer images and determine angular position. The camera-based optical system measures the angular displacement of the wafer relative to the ion beam, eliminating the need for complex mechanical alignment mechanisms while achieving higher precision.
Solution Approach 2:
The patent introduces a camera as an intermediary device between the wafer and the alignment control system. The camera captures images of the wafer and provides angular position data to the control system, which then calculates the angular displacement and controls the platen rotation. This intermediary enables precise measurement without direct mechanical contact or complex alignment mechanisms.
2Manufacturing precision
If manual alignment adjustment is used, then the equipment is simpler, but the within-wafer uniformity of ion exposure deteriorates
Solution Approach 1:
The patent implements a feedback control system where the camera continuously monitors the wafer's angular position, the control system calculates the angular displacement from the measured position, and the platen is rotated by the calculated amount to correct the alignment. This closed-loop feedback ensures accurate angular alignment and consistent within-wafer uniformity across multiple wafers.
Solution Approach 2:
The system performs self-alignment by automatically measuring the wafer's actual angular position and rotating the platen by the calculated displacement amount. The control system autonomously determines the required correction and executes the alignment without manual intervention, ensuring consistent precision across different wafers.
3Reliability
If angular alignment measurement is not performed, then the process is faster, but the wafer-to-wafer process variations increase
Solution Approach 1:
The patent performs angular alignment measurement as a preliminary step before ion exposure by capturing wafer images and calculating angular displacement in advance. This preliminary measurement allows the system to pre-determine the required platen rotation amount, ensuring accurate alignment before the actual ion exposure process begins.
Solution Approach 2:
The patent replaces time-consuming mechanical alignment procedures with rapid optical measurement using a camera. The camera-based system quickly captures wafer images and calculates angular position, providing measurement data much faster than traditional mechanical alignment methods while ensuring consistent wafer-to-wafer reliability.
Data Source
AI summary
In an embodiment, a method includes: placing a wafer on an implanter platen, the wafer including integrated circuit dies; measuring a position of the wafer by measuring a position of an outer edge of the integrated circuit dies with a camera; determining an angular displacement between the position of the wafer and a reference position of the wafer; and rotating the implanter platen by the angular displacement.