Wafer Inspection Timing Control for Stage Offset Noise Reduction
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Solution Overview
Problem
Stage vibration during wafer inspection causes image distortion, leading to reduced inspection quality and potential rejection of qualified wafers due to noisy images.
Innovation Solution
A wafer inspection system that includes an optical device, movable stage, position measurement device, and control device to mitigate position offset errors by controlling the timing of the light source and image sensor based on real-time dynamic position errors, reducing noise in captured images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stage vibration occurs during wafer inspection, then the inspection process can continue without interruption, but image distortion and noise increase reducing inspection quality
Solution Approach 1:
The system performs preliminary measurement of stage position using a position measurement device (e.g., laser interferometer) to obtain dynamic position errors before image capture. The control device calculates timing adjustments based on these pre-measured position offsets, allowing the image sensor to capture images at optimized moments that compensate for anticipated stage vibration, thus maintaining inspection quality without interrupting the inspection process
Solution Approach 2:
The system dynamically adjusts the timing of image capture based on real-time stage position feedback. The control device modifies the timing of the image sensor operation according to measured dynamic position errors, transforming the static inspection process into a dynamic adaptive system that responds to actual stage conditions, thereby maintaining image quality despite ongoing vibrations
2Device complexity
If conventional image capture timing is used without compensation, then the inspection process is simple, but stage vibration causes image distortion and noise
Solution Approach 1:
The system implements a feedback loop where the position measurement device continuously monitors stage position and feeds this information to the control device. The control device uses this feedback to calculate and apply timing adjustments to the image sensor operation, creating a closed-loop system that automatically compensates for stage vibration without requiring complex manual intervention or system redesign
Solution Approach 2:
The control device acts as an intermediary between the position measurement device and the image sensor. It receives position offset data from the measurement device, processes this information to determine optimal timing adjustments, and translates these adjustments into control signals for the image sensor, thereby mediating the interaction between measurement and capture subsystems to eliminate vibration effects
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
Improves the quality of wafer inspection by minimizing image noise and distortion, ensuring accurate inspection results.
Implementation Method 1
The position measurement device is configured to obtain a position offset between an actual moving path of the movable stage and the predetermined moving path
Implementation Method 2
The image sensor is configured to capture the reflected light through an imaging optical and generate an image of the wafer accordingly
Data Source
AI summary
A wafer inspection system includes an optical device, a movable stage, a position measurement device, and a control device. The optical device is configured to generate a light toward a wafer and capture a reflected light. The movable stage is configured to move the wafer. The position measurement device is configured to obtain a position offset between an actual path and a predetermined path. The position offset includes a first error and a second error. A stage coordinate system has a first and a second stage axis perpendicular to each other, and the first and the second errors are parallel to the first and the second stage axis, respectively. The control device is configured to control a timing for emitting the light or control a timing to capture the reflected light according to the position offset in real time in order to mitigate undesired effects caused by the position offset.