Optical Inspector Selective Scattered Radiation Blocker
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Solution Overview
Problem
Detecting defects in transparent wafers, such as those used in LED production, is challenging due to the difficulty in separating scattered light from the top and bottom surfaces, which affects light extraction efficiency and device performance.
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 processing the radiation types and intensities to determine the presence of defects on the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a normal or oblique laser with a beam block and pinhole is used to separate top and bottom surface scattered light, then the bottom surface scattered light can be separated, but the device complexity increases and measurement precision is compromised
Solution Approach 1:
The patent divides the detection of scattered light into two separate detection paths: one for top surface scattered light and one for bottom surface scattered light. By using multiple detectors positioned at different angles, the system segments the measurement process to accurately distinguish between light scattered from different surfaces, resolving the technical contradiction between measurement precision and device complexity.
2Device complexity
If scattered light from both top and bottom surfaces is measured together, then the measurement process is simplified, but defect detection accuracy deteriorates
Solution Approach 1:
The patent applies local quality by assigning different detection characteristics to different spatial locations. Detectors are positioned at specific angles to receive scattered light predominantly from specific surfaces (top or bottom). This localized detection approach maintains a relatively simple measurement process while achieving high defect detection accuracy by focusing each detector on its optimal detection zone.
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 by effectively separating and analyzing scattered radiation from the top and bottom surfaces, improving light extraction efficiency and reducing the risk of defective LED devices.
Implementation Method 1
a polarizing beam splitter that receives reflected radiation from the sample
Implementation Method 2
a time varying beam reflector, a radiating source that irradiates a first position on the time varying beam reflector with source radiation
Implementation Method 3
a telecentric scan lens that directs the source radiation from the time varying beam reflector onto a sample
Implementation Method 4
The types of radiation include specular reflection, near specular scattered radiation, and scattered radiation
Data Source
AI summary
An optical inspector includes a radiating source, a time varying beam reflector, a telecentric scan lens, a blocker, a focusing lens, an aperture, and a detector. The radiating source irradiates a first position of on the time varying beam reflector with a source beam. 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. A portion of the source beam travels through the transparent sample to another surface. The blocker blocks scattered radiation originating at the other surface. Scattered radiation originating from the transparent sample is not redirected by the blocker and is focused by the focusing lens to a first focal plane. The focused scattered radiation passes through the aperture before irradiating the detector. The detector output an intensity measurement of the scattered radiation that irradiates the detector.