Wafer Alignment Apparatus Using Reflection Part for Edge Detection
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Solution Overview
Problem
The challenge in accurately detecting the circumferential edge of a wafer with a beveled portion, which affects the precision of alignment in semiconductor manufacturing, due to differences in light reflection between the beveled and inner portions of the wafer.
Innovation Solution
An alignment apparatus that uses an imaging unit, an irradiation unit, and a reflection part to create a luminance distribution pattern, allowing a control unit to detect the alignment mark and circumferential edge with high accuracy by distinguishing the luminance differences between the beveled portion and the reflection part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a reflective type sensor (camera) is used to detect the alignment mark and circumferential edge by imaging the wafer, then the detection capability is improved, but the measurement precision deteriorates due to varying light reflection states between the beveled portion and the inner portion of the wafer
Solution Approach 1:
A reflection part is introduced as an intermediary element between the light source and the imaging unit. This reflection part reflects light from the beveled portion back toward the imaging unit, creating a controlled light path that enhances the luminance difference between the beveled portion and the inner portion, thereby improving measurement precision while maintaining detection capability
Solution Approach 2:
The invention utilizes luminance (light intensity) changes rather than color changes to differentiate regions. By controlling the reflection of light to create distinct luminance patterns between the beveled portion and the inner portion, the system achieves precise detection based on luminance distribution rather than color differentiation
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
Enables precise detection of the wafer's alignment mark and circumferential edge, improving the accuracy of wafer orientation and positioning during semiconductor processing.
Implementation Method 1
a reflection part configured to reflect toward the imaging region the light that is irradiated from the irradiation unit upwardly while passing through an outside of the wafer
Implementation Method 2
an imaging unit configured to image, from a position below the wafer, an imaging region having a strip shape extending in a diametrical direction of the wafer across a circumferential edge of the wafer
Data Source
AI summary
An alignment apparatus for aligning a wafer by optically detecting an alignment mark includes an imaging unit configured to image an imaging region extending across a circumferential edge of the wafer, an irradiation unit configured to irradiate light toward the imaging region, a reflection part configured to reflect toward the imaging region the light that is irradiated from the irradiation unit upwardly, and a control unit configured to detect the circumferential edge. The reflection part has a reflectance making a luminance difference between the outside of the wafer and the circumferential edge of the wafer in a luminance distribution pattern obtained by imaging the imaging region. The control unit detects the alignment mark and the circumferential edge based on the luminance distribution pattern.