Camera-Based Wafer Alignment for Uniform Ion Exposure
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Solution Overview
Problem
Existing semiconductor fabrication processes face challenges in achieving precise angular alignment of wafers during ion exposure, leading to within-wafer uniformity issues, wafer-to-wafer process variations, and increased device defects due to coarse alignment using notches.
Innovation Solution
An ion exposure apparatus with a platen and sensors, such as cameras, measures the angular position of integrated circuit dies on the wafer, correcting misalignment by rotating the platen to align the wafer with the ion beam, ensuring precise angular alignment and uniform ion distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If coarse alignment using notches is used during wafer placement, then the placement process is simple and fast, but the angular alignment precision is insufficient leading to within-wafer uniformity issues
Solution Approach 1:
The patent replaces the mechanical notch-based alignment system with an optical sensing system using cameras and image processing. The camera captures images of the wafer, and software algorithms determine the angular position by analyzing features on the wafer surface, substituting mechanical alignment references with optical detection and computational analysis.
Solution Approach 2:
The patent introduces an intermediary alignment mark or feature on the wafer that serves as a reference for the camera system. This intermediary element bridges the gap between the simple mechanical placement and the precise optical measurement, allowing the camera to detect angular position without requiring complex direct measurement of the wafer orientation.
2Reliability
If sensors and rotation correction are implemented, then within-wafer uniformity improves, but the apparatus complexity increases
Solution Approach 1:
The patent implements a feedback control system where the camera measures the actual angular position of the wafer, compares it to the desired position, and the platen rotates to correct any misalignment. This closed-loop feedback ensures accurate alignment while maintaining simplicity through automated correction rather than complex mechanical precision requirements.
Solution Approach 2:
The system performs self-alignment by automatically detecting its own misalignment through the camera and correcting it through automated platen rotation. The apparatus monitors and adjusts its own state without requiring external intervention or complex pre-calibration, making the system self-correcting and reducing overall complexity.
3Measurement precision
If precise angular measurement is performed, then misalignment correction is accurate, but the measurement system becomes more complex
Solution Approach 1:
The patent replaces complex mechanical angle encoders or interferometric measurement systems with a simpler camera-based optical system. Standard digital cameras capture images of the wafer, and software algorithms process these images to calculate angular position, substituting specialized measurement hardware with off-the-shelf components and computational methods.
Solution Approach 2:
The system creates a digital copy or image of the wafer using the camera, then performs angular measurement on this digital representation rather than directly on the physical wafer. This allows complex measurements to be performed through software analysis of the image copy, avoiding the need for complex physical measurement apparatus.
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 positions 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.