Laser Scribing and Wet Etching for LED Wafer Singulation
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Solution Overview
Problem
Mechanical scribing tools used in semiconductor LED fabrication can adversely impact throughput, yield, reliability, and performance due to the hardness of substrate wafers, leading to scribe damage and radiant flux loss.
Innovation Solution
Laser scribing followed by wet etching is employed to create a laser scribing cut on semiconductor LEDs, reducing scribe damage and allowing for deeper scribe lines without compromising the performance of the LEDs, and the process is moved to the front end of fabrication to minimize impact on electrical contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical scribing tools are used to scribe LED wafers, then scribing can be performed, but scribe damage occurs and radiant flux loss increases
Solution Approach 1:
The patent replaces mechanical scribing tools with a laser-based scribing system. The laser beam creates scribe lines through photothermal ablation of the material, eliminating mechanical contact and associated damage. This substitution resolves the contradiction by maintaining scribing capability while eliminating mechanical-induced scribe damage and radiant flux loss.
Solution Approach 2:
The laser scribing process utilizes phase transitions (melting and vaporization) of the wafer material to create scribe lines. The concentrated laser energy raises the material temperature above its melting and vaporization points, enabling clean separation without mechanical stress. This phase transition mechanism eliminates the scribe damage problematic in mechanical scribing.
2Manufacturing precision
If laser scribing is performed deeper to improve singulation, then singulation quality improves, but scribe damage increases
Solution Approach 1:
By using laser scribing instead of mechanical tools, the system can achieve deeper scribe lines without the diminishing returns and increased damage associated with mechanical scribing. The laser maintains consistent energy delivery regardless of depth, enabling precise deep scribing that improves singulation without proportionally increasing damage.
Solution Approach 2:
The laser beam acts as an intermediary that transfers energy to the material without direct physical contact. This allows the scribing process to penetrate deeper into the substrate while the energy deposition remains controlled and localized, preventing the spread of damage that would occur with mechanical tools at equivalent depths.
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 reduces scribe damage, enhances light extraction, and allows for deeper scribe lines without increasing radiant flux loss, improving the yield and reliability of semiconductor LEDs.
Implementation Method 1
laser scribing comprises impinging a laser beam through the LED epitaxial region and partially into the substrate to produce the laser scribing cut
Implementation Method 2
the cleaning comprises wet etching the wafer through the LED epitaxial region that has been laser scribed and into the substrate that has been laser scribed
Data Source
AI summary
A wafer of light emitting diodes (LEDs) is laser scribed to produce a laser scribing cut. Then, the wafer is cleaned, for example by wet etching, to reduce scribe damage. Then, electrical contact layers for the LEDs are formed on the wafer that has been cleaned. Alternatively, the scribing cut may be produced by multiple etches before contact formation. Related LEDs are also described.