Multi-surface Optical Inspector for Transparent Wafer Defect Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Detecting defects in transparent wafers, such as cracks, growth defects, and contaminants, is challenging due to the difficulty in separating scattered light from the top and bottom surfaces, which affects the light extraction efficiency and performance of LED devices.
Innovation Solution
A surface optical inspector system that uses a time varying beam reflector, telecentric scan lens, polarizing beam splitter, and detectors to separate and measure specular and near specular scattered radiation, allowing for the detection of defects by distinguishing between top and bottom surface reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a beam block with pinhole is used to separate top and bottom surface scattered light, then bottom surface scattered light can be separated, but the device complexity increases and alignment precision requirements increase
Solution Approach 1:
A polarizing beam splitter is introduced as an intermediary optical element between the incident light and the detectors. This beam splitter uses polarization properties to selectively transmit light from the top surface while blocking light from the bottom surface, eliminating the need for complex beam blocks with pinholes and achieving superior separation without increasing device complexity
Solution Approach 2:
The system changes the polarization state of light using waveplates and a polarizing beam splitter. By manipulating the polarization parameter of the incident light and the reflected light, the system achieves separation of top and bottom surface signals without mechanical complexity, transforming an optical path separation problem into a polarization state control problem
2Measurement precision
If multiple detectors are used to measure different radiation types, then measurement precision improves, but device complexity increases
Solution Approach 1:
The optical detection system is segmented into multiple functional channels: a first detector for measuring specular reflection from the top surface, a second detector for measuring scattered radiation from the top surface, and a third detector for measuring scattered radiation from the bottom surface. Each detector is paired with specific optical components (waveplates, beam splitters) that direct specific radiation types to the appropriate detector, enabling precise multi-parameter measurement while maintaining modular system architecture
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 accurate detection of defects on transparent wafers, improving light extraction efficiency and preventing defects from leading to non-functional LED devices by effectively separating and analyzing scattered radiation from both surfaces.
Implementation Method 1
a polarizing beam splitter that receives reflected radiation from the sample
Implementation Method 2
a telecentric scan lens that directs the source radiation from the time varying beam reflector onto a sample
Implementation Method 3
a time varying beam reflector, a radiating source that irradiates a first position on the time varying beam reflector
Data Source
AI summary
An optical inspector includes a radiating source, a time varying beam reflector, a telecentric scan lens, a first waveplate, a second waveplate, a polarizing beam splitter, and a detector. The radiating source irradiates the first waveplate with a linearly polarized source beam generating a circularly polarized source beam, which irradiates a first position of on the time varying beam reflector. The time varying beam reflector directs the source beam to the telecentric scan lens, which in turn directs the source beam to a transparent sample. The reflected radiation from the transparent sample is directed via the telecentric lens and the time varying beam reflector to the second waveplate, which converts circularly polarized reflected radiation to linearly polarized reflected radiation including radiation that is vertically polarized and radiation that is horizontally polarized. The polarizing beam splitter redirects vertically polarized reflected radiation to the detector while horizontally polarized reflected radiation passes through.