Notchless Wafer Chamfering Apparatus with Optical Feedback Control
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Solution Overview
Problem
The manufacturing of notchless wafers faces challenges in achieving precise cross-sectional shape control of the chamfered portion due to the absence of a notch for alignment, leading to variations in the chamfered shape and increased costs from requiring expensive alignment mechanisms for crystal orientation mark detection.
Innovation Solution
A chamfering apparatus with a rotatable stage and control means that allows for precise rotational positioning of the wafer, enabling measurement and feedback control of the chamfered shape, ensuring the measured value is used for chamfering control at the corresponding rotational position, thus suppressing circumferential variation and achieving high precision without the need for an additional alignment mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a notch is removed to create a notchless wafer, then stress concentration and slipping are reduced, but alignment precision for chamfering control is lost
Solution Approach 1:
The patent uses optical copying to create an image of the crystal orientation mark on the wafer back surface. This optical copy serves as a virtual alignment reference that can be processed and measured without physically contacting or damaging the actual mark, enabling precise chamfering control on notchless wafers
Solution Approach 2:
The patent introduces an optical system as an intermediary between the crystal orientation mark and the measurement/control system. By capturing an optical image of the mark and processing it through image analysis algorithms, the system achieves precise alignment without requiring direct mechanical contact or additional physical alignment features on the wafer
2Measurement precision
If expensive alignment mechanisms are added to detect crystal orientation marks, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical alignment mechanisms with an optical measurement system. Instead of using mechanical sensors or physical alignment tools to detect the crystal orientation mark, the system uses optical imaging combined with image processing algorithms to achieve precise detection and measurement
Solution Approach 2:
The patent creates an optical copy (image) of the crystal orientation mark and performs all measurements and analysis on this digital copy rather than requiring complex physical measurement mechanisms. This approach simplifies the hardware while maintaining high measurement precision through software-based image analysis
3Device complexity
If rotational position control is not implemented, then device complexity is reduced, but chamfered shape variation increases
Solution Approach 1:
The patent implements a feedback control system where the optical image of the crystal orientation mark is analyzed to determine the actual rotational position of the wafer. This measured position information is then fed back to the rotational drive system to correct any deviations, ensuring that the chamfering operation is performed at the precise intended location despite variations in wafer placement or rotation
Solution Approach 2:
The patent performs preliminary measurement and positioning of the crystal orientation mark using optical imaging before the actual chamfering operation begins. By determining the rotational position in advance and making necessary adjustments before machining starts, the system ensures accurate chamfering without requiring complex real-time control during the cutting process
Data Source
AI summary
A chamfering apparatus including chamfering part for removing notch, cleaning part for cleaning and drying wafer, and chamfered-shape measuring part for measuring chamfered shape, each of chamfering and cleaning part, and chamfered-shape measuring part including rotatable stage for holding wafer and control unit for controlling rotational positions of rotatable stage and wafer, rotatable stage having reference position serving as reference of rotational positions at beginning of rotation, wherein wafer is held wherein rotational position of wafer at beginning of rotation relative to reference position is at same rotational position on all rotatable stages, and control unit to control rotational position of wafer to be at predetermined position at beginning and end of rotation. As a result, the chamfering apparatus and method for manufacturing notchless wafer allowing appropriate feedback control even in notchless wafer, suppress variation in chamfered shape dimension, and achieve desired cross-sectional shape precision of wafer chamfered portion.