Semiconductor Light-Emitting Device Inspection via Photoluminescence Imaging
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Solution Overview
Problem
Existing inspection methods for semiconductor light-emitting devices fail to properly detect defective devices that emit light with shorter wavelengths, which can decline in photoluminescence intensity or cease to emit light over time, due to manufacturing defects or other issues.
Innovation Solution
An inspection method that irradiates semiconductor light-emitting devices with light of a wavelength shorter than the original wavelength, captures the photoluminescence image, and determines the device as defective if there are pixels with high photoluminescence intensity of a second wavelength, indicating potential defects, using image analysis to extract inspection regions and assess photoluminescence intensity and variance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection methods using visible light and prober contact are used, then appearance and basic light emitting performance can be inspected, but inspection time becomes excessively long and probe contact may cause flaws on the semiconductor light-emitting devices
Solution Approach 1:
The patent replaces the mechanical prober contact system with an optical inspection system using photoluminescence imaging. Instead of physically contacting the device with probes to measure light emitting performance, the system uses light irradiation and captures the photoluminescence emitted by the active layer, thereby eliminating mechanical contact while maintaining inspection accuracy and significantly reducing inspection time
Solution Approach 2:
The patent creates an optical copy (photoluminescence image) of the light emitting characteristics of the semiconductor light-emitting device. By capturing the photoluminescence image and analyzing pixel values, the system obtains information about light emitting performance without direct physical measurement, enabling rapid non-contact inspection
2Measurement precision
If conventional photoluminescence inspection only checks for insufficient blue light emission, then devices with low photoluminescence intensity can be detected, but devices emitting short-wavelength light that may fail over time cannot be properly detected
Solution Approach 1:
The patent applies local quality analysis by examining specific regions and pixel values within the photoluminescence image. Instead of only checking overall photoluminescence intensity, the system analyzes local color tone characteristics (hue, saturation, brightness) of individual pixels to detect short-wavelength light emission, enabling identification of localized defects that could lead to future device failure
Solution Approach 2:
The patent utilizes color changes in the photoluminescence image to detect defective devices. By analyzing the hue, saturation, and brightness of pixels, the system identifies deviations from normal color tones that indicate short-wavelength light emission, providing a visual and quantitative method to detect potential failures before they occur
3Measurement precision
If small-sized semiconductor light-emitting devices are inspected with prober contact, then light emitting performance can be measured, but proper contact between probe and device becomes difficult due to small pad electrode size
Solution Approach 1:
The patent replaces the mechanical prober contact system with a non-contact optical inspection method. By irradiating light and capturing photoluminescence images, the system measures light emitting performance without requiring physical contact, thereby eliminating the difficulty of contacting small pad electrodes while maintaining measurement accuracy for small-sized devices
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
Effectively detects defective semiconductor light-emitting devices that emit light with shorter wavelengths, ensuring proper screening and exclusion of devices that may deteriorate or fail to emit light, thereby improving the quality control of semiconductor light-emitting devices.
Implementation Method 1
the active layer of semiconductor light-emitting devices is excited with light irradiation and photoluminescence released from the excited active layer is observed
Data Source
AI summary
An inspection method for a semiconductor light-emitting device includes an image capturing step for capturing an image of photoluminescence released from the active layer, an inspection region extracting step for extracting an inspection region from the captured image; a luminance average determination step for, determining the semiconductor light emitting device as defective when a luminance average is smaller than a predetermined threshold, a luminance variance determination step for determining the semiconductor light emitting device as defective when a luminance variance is larger than a predetermined threshold, a color determination step for determining the semiconductor light-emitting device as defective when a pixel in which a color component indicating a photoluminescence intensity of light released from the active layer and having a wavelength shorter than the original emitting wavelength, and a total determination step for totally determining the semiconductor light-emitting device as defective when determined in at least one of these determination results within the inspection region.