Micro-LED Beam Profiling Using Refractive Transmission Medium
Solution Overview
Problem
Existing methods for characterizing the beam emitted from light emitting semiconductor devices, such as micro-LEDs, are unable to profile the entire beam from -90 degrees to +90 degrees to the normal and cannot perform characterization at the wafer level, limiting their effectiveness in measuring divergent beams and device performance.
Innovation Solution
A method and apparatus using a transmission medium with a refractive index greater than air, which diffuses light emitted from the semiconductor device, allowing for the capture of light at angles up to ±90 degrees to the normal, and a camera system to profile the beam by determining intensity and angle of emission, enabling wafer-level characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera and lens system is used to form a real image of a divergent beam directly onto a detector, then the beam profile can be captured, but the detector or lens must be very large and placed very close to the laser device
Solution Approach 1:
A transmission medium with refractive index greater than air is introduced as an intermediary between the light emitting device and the detector. This medium refracts the divergent light beams, effectively reducing the angular spread of light reaching the detector. Consequently, a smaller detector area can capture the same angular range of the beam profile, resolving the contradiction between measurement capability and detector size.
2Measurement precision
If a goniometer is used to characterise light from an LED device, then beam characterization can be performed, but devices must be diced and packaged before accurate characterization
Solution Approach 1:
The transmission medium is positioned to receive light directly from the light emitting surface of the device on the wafer, before dicing and packaging operations. This preliminary measurement capability allows beam characterization to be performed at an earlier stage in the manufacturing process, eliminating the requirement to dice and package devices before characterization, thus improving ease of manufacture while maintaining measurement precision.
3Adaptability or versatility
If existing characterization methods are used, then some beam parameters can be measured, but the entire beam from -90 degrees to +90 degrees cannot be profiled
Solution Approach 1:
The refractive index parameter of the transmission medium is specifically chosen to be greater than air (e.g., glass or other transparent materials). This parameter change in the optical path refracts the light beams, compressing the angular spread. Light emitted at angles up to ±90 degrees relative to the normal is refracted to smaller angles in the transmission medium, allowing the entire beam range to be captured by a detector of practical size while maintaining angular resolution through calibrated refractive index compensation.
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 comprehensive beam profiling of micro-LEDs from -90 degrees to +90 degrees, facilitating sample engineering testing, high-volume production testing, and ensuring devices meet performance specifications, while allowing for testing on the wafer before packaging.
Implementation Method 1
A transmission medium with a refractive index greater than air is provided. The transmission medium has a diffusion surface configured to diffuse light emitted from the semiconductor device and transmitted through the transmission medium
Implementation Method 2
a diffusion surface, opposite the first surface, and configured to diffuse light emitted from the semiconductor device and transmitted through the transmission medium
Data Source
AI summary
Methods and apparatus (100) for profiling a beam of a light emitting semiconductor device. The apparatus comprises a light emitting semiconductor device (102) comprising an active region (108) formed on a substrate (104) and configured to generate light when a suitable electrical current is applied to contacts on an upper surface of the device and a light emitting surface (110) defined by a lower surface of the substrate opposite the contacts. The apparatus further comprises a transmission medium (112) comprising a first surface (114) in contact with at least part of the light emitting surface of the semiconductor device and a diffusion surface (116), opposite the first surface, and configured to diffuse light emitted from the micro-LED and transmitted through the transmission medium.