Workpiece Characterization System Using Single Broadband Light Source
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Solution Overview
Problem
Current workpiece characterization systems for LEDs are limited in their ability to perform multiple characterization measurements efficiently and effectively, particularly due to the use of narrowband excitation sources that can interfere with photoluminescence emission, leading to inefficiencies in yield control and process optimization in the semiconductor processing industry.
Innovation Solution
A system and method utilizing a single broadband light source that acts as both an excitation and illumination source, with wavelength filtering to avoid interference with photoluminescence emission, allowing for simultaneous measurement of photoluminescence and encoded information from LEDs, enabling accurate and efficient characterization of LED properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrowband excitation source is used to excite photoluminescence in LEDs, then the photoluminescence emission can be excited, but the excitation light interferes with the photoluminescence emission measurement
Solution Approach 1:
The system separates the detection into two distinct optical paths: one for collecting photoluminescence emission at angle Θ2 and another for measuring reflected excitation light at angle Θ1. This spatial segmentation allows independent measurement of emission and reflection signals, eliminating interference between excitation light and photoluminescence detection
Solution Approach 2:
The system uses angle-resolved detection as an intermediary method to distinguish between photoluminescence emission and reflected excitation light. By measuring at different angles (Θ1 for reflection, Θ2 for emission), the system can separate and independently analyze the two light components, resolving the interference problem
2Reliability
If multiple characterization measurements are performed on LED wafers, then comprehensive yield control is achieved, but the process time increases leading to delays in correcting process drifts
Solution Approach 1:
The system combines multiple characterization measurements into a single integrated optical setup that simultaneously collects both photoluminescence emission and reflected light signals. This merging of measurement functions into one system enables comprehensive characterization without sequential measurement delays
Solution Approach 2:
The system enables continuous, real-time monitoring of LED wafer properties during fabrication by maintaining constant optical measurement capability. The uninterrupted collection of photoluminescence and reflection data allows immediate detection of process drifts and excursions, enabling timely corrections
3Device complexity
If a single broadband light source is used for both excitation and illumination, then system complexity is reduced, but spectral interference may occur across different wavelength regions
Solution Approach 1:
The system applies wavelength-specific analysis to different spectral regions: the broadband source covers UV through visible ranges, with photoluminescence emission analyzed in specific wavelength bands (e.g., 400-700nm) while reflected light analysis focuses on other regions. This local spectral quality control prevents interference by assigning different analytical treatments to different wavelength domains
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
This approach simplifies the characterization process, increases measurement accuracy, and enables real-time monitoring and control, improving LED wafer yield and reducing processing inefficiencies by allowing for simultaneous excitation and illumination with a single light source.
Implementation Method 1
Photoluminescence provides a rapid and non-contact method for determination of many parameters that affect yield. For LEDs of current market interest for lighting applications, especially Gallium Nitride ('GaN') and related alloys of Aluminum and Indium, UV light is used to excite photoluminescence of longer wavelengths of UV/Blue emission
Implementation Method 2
A single broadband light source is provided that generates a wide spectrum of light that traverses each of the regions of high absorption, the photoluminescence emission region and the region of wavelengths with encoded information
Data Source
AI summary
A workpiece characterization system for obtaining simultaneous measurement of layer and photoluminescence properties of a workpiece. The workpiece characterization system includes an excitation light and an illumination light each impinging upon a surface of a workpiece whereby the workpiece emits photoluminescent light and encodes light from said illumination source with layer information. The excitation light and the illumination light are generated from a single light source. The light from the single light source is filtered to remove wavelengths of light that correlate to light wavelengths emitted from the workpiece as a result of excitation. Wavelengths that correlate to light reflected from the workpiece that may contain encoded information are not filtered.