LED Die Laser Lift-Off With Elastomer Cushioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The laser lift-off process in LED fabrication often results in thermal decomposition of the n-GaN layer, causing explosive forces that lead to cracks and micro-cracks in the dice, device leakage, and reliability issues, and requires additional costly dicing steps to separate individual dice.
Innovation Solution
A method involving a receiving plate with an elastomeric polymer layer that absorbs kinetic energy during laser lift-off, allowing for the removal of semiconductor structures without a secondary substrate, thereby preventing damage and eliminating the need for dicing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser lift-off is performed to remove substrate, then substrate is successfully removed, but thermal decomposition causes explosive forces creating cracks and micro-cracks in the LED dice
Solution Approach 1:
A receiving plate is introduced as an intermediary component between the substrate and the LED dice during laser lift-off. The receiving plate captures the explosive force and momentum transfer from the decomposing n-GaN layer, preventing direct damage to the dice. This mediator absorbs the harmful kinetic energy while allowing the substrate removal process to proceed.
Solution Approach 2:
The receiving plate is positioned in advance to cushion the impact before the explosive force reaches the LED dice. By having the receiving plate ready to absorb the momentum transfer during laser lift-off, the system prevents cracks and micro-cracks from forming in the dice structure.
2Ease of manufacture
If continuous secondary substrate is bonded before laser lift-off to hold dice in place, then dice are held securely during processing, but additional dicing step is required to separate individual dice
Solution Approach 1:
The invention extracts and eliminates the continuous secondary substrate from the process. Instead of bonding a continuous substrate to hold dice in place, the receiving plate with adhesive polymer layer individually captures each dice during laser lift-off, removing the need for subsequent dicing operations to separate individual dice.
Solution Approach 2:
The adhesive polymer layer on the receiving plate performs the function of holding dice in place during laser lift-off without requiring a separate continuous secondary substrate. The system uses the receiving plate's adhesive properties to self-service the positioning function, eliminating the need for additional dicing steps.
3Ease of manufacture
If secondary substrate is used to hold dice together during laser lift-off, then dice remain in place during processing, but explosive force causes damage to epitaxial layers
Solution Approach 1:
The receiving plate acts as an intermediary that protects the epitaxial layers from damage during laser lift-off. It absorbs the explosive force and momentum transfer, preventing the damage that would otherwise occur to the delicate epitaxial structures while still maintaining dice stability during processing.
4Ease of operation
If dicing process is used to separate individual dice, then single dice can be picked up, but equipment cost and yield loss increase
Solution Approach 1:
The invention extracts and eliminates the dicing process from the manufacturing flow. By using the receiving plate to individually capture and position dice during laser lift-off, the system achieves dice separation without requiring costly dicing equipment or accepting the yield losses associated with mechanical or laser dicing operations.
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 enables the fabrication of thin, undamaged LED dice without the need for a secondary substrate, reducing costs and improving yield by preventing damage from momentum transfer and eliminating the dicing process.
Implementation Method 1
the thermal decomposition of the n-GaN layer 20 (FIG. 1C) at the interface with the substrate 12 (e.g., GaN/sapphire interface)
Implementation Method 2
the elastomeric polymer layer on the receiving plate functions as a shock absorber to absorb kinetic energy from the semiconductor structures via momentum energy transfer
Implementation Method 3
placing the substrate and the receiving plate in physical contact with an adhesive force applied by the elastomeric polymer layer
Data Source
AI summary
A method for fabricating light emitting diode (LED) dice includes the steps of: providing a substrate, and forming a plurality of die sized semiconductor structures on the substrate. The method also includes the steps of providing a receiving plate having an elastomeric polymer layer, placing the substrate and the receiving plate in physical contact with an adhesive force applied by the elastomeric polymer layer, and performing a laser lift-off (LLO) process by directing a uniform laser beam through the substrate to the semiconductor layer at an interface with the substrate to lift off the semiconductor structures onto the elastomeric polymer layer. During the laser lift-off (LLO) process the elastomeric polymer layer functions as a shock absorber to reduce momentum transfer, and as an adhesive surface to hold the semiconductor structures in place on the receiving plate.