Light-Emitting Device Wafer Testing Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional high voltage light-emitting devices face challenges in identifying and isolating electrical defects in individual elements during fabrication, which can degrade the reliability of the device due to the difficulty in measuring the electrical properties of each element separately.
Innovation Solution
A method is introduced where a wafer is divided into a test site and a device site, with specific light-emitting elements formed on each site. Conductive pads are created for each element, allowing for sequential current flow testing of electrical properties while keeping others inactive, enabling the correlation of properties between test and device elements, and subsequent division into separate light-emitting devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electrical testing methods are used on high voltage light-emitting devices, then the overall electrical yield can be measured, but the electrical properties of individual light-emitting elements cannot be identified
Solution Approach 1:
The patent divides the testing approach by separating test sites from device sites on the wafer. Test sites contain light-emitting elements with independently accessible electrodes designed specifically for electrical characterization, while device sites contain elements configured for final product operation. This segmentation allows precise measurement of individual element properties without requiring complex probing of the complete device structure.
Solution Approach 2:
The patent introduces conductive pads as intermediary structures between the light-emitting elements and external measurement equipment. These pads provide accessible electrical contact points that simplify the measurement process, allowing current to be applied to and measured from individual elements without directly probing the element terminals, thus reducing testing complexity while maintaining measurement precision.
2Power
If multiple light-emitting elements are electrically connected in series to form high voltage devices, then the light output and voltage rating increase, but the reliability decreases due to undetected electrical defects
Solution Approach 1:
The patent implements preliminary electrical testing of individual light-emitting elements at the test sites before the elements are assembled into high voltage devices. By measuring and characterizing each element's electrical properties (forward voltage, reverse leakage current) while they are still individually accessible on the wafer, defects can be identified and problematic elements can be sorted out before they are connected in series, ensuring higher reliability of the final high voltage device assembly.
3Reliability
If electrical testing is performed on the complete high voltage device, then the overall performance can be verified, but the time and resources required for testing increase
Solution Approach 1:
The patent segments the testing process into two stages: individual element testing at test sites, and final device verification at device sites. By testing elements individually while they are still on the wafer and easily accessible, the majority of electrical characterization is completed quickly without requiring assembly into the complete high voltage device. This reduces the time and resources needed for final device testing, as only a subset of verified good elements needs to be assembled and undergo final verification.
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 method allows for precise identification and monitoring of electrical defects in high voltage light-emitting devices, enhancing their reliability by ensuring each element's electrical properties are characterized and defects are located, thereby improving the overall yield and performance.
Implementation Method 1
The light-emitting principle of the LED is the transformation of electrical energy to optical energy by applying electrical current to the p-n junction to generate electrons and holes. Then, the LED emits light when the electrons and the holes combine.
Data Source
AI summary
A method for forming a light-emitting device of the present application comprises providing a wafer; forming a first plurality of light-emitting elements on the wafer; providing a first connection structure to connect each of the first plurality of light-emitting elements; and applying a current flow to one of the first plurality of light-emitting elements for testing at least one electrical property of the light-emitting element while no current flow is applied to the remaining of the first plurality of light-emitting elements.