LED Die Laser Lift-Off With Elastomeric Shock-Absorbing Plate
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Solution Overview
Problem
The laser lift-off process in semiconductor fabrication for light emitting diode (LED) dice often results in thermal decomposition of the n-GaN layer, leading to explosive forces that cause cracks and micro-cracks, 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, preventing damage and eliminating the need for dicing by holding the dice in place and facilitating their separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser lift-off is performed to separate semiconductor structures from substrate, then the semiconductor structures can be transferred to a receiving plate, but thermal decomposition of the n-GaN layer causes explosive forces that create cracks and micro-cracks in the dice
Solution Approach 1:
A receiving plate with an elastomeric polymer layer is introduced as an intermediary between the semiconductor structures and the final destination. This receiving plate absorbs the explosive forces during laser lift-off, preventing direct damage to the semiconductor structures while still enabling successful transfer.
Solution Approach 2:
The elastomeric polymer layer on the receiving plate is positioned beforehand to cushion and absorb the explosive forces generated during laser lift-off. This pre-positioned cushioning layer prevents cracks and micro-cracks from forming in the semiconductor structures during the separation process.
2Stability of the object's composition
If a continuous secondary substrate is bonded before laser lift-off to hold the dice in place, then the dice remain stable during processing, but the explosive force causes damage to the epitaxial layers and additional dicing is required
Solution Approach 1:
The function of holding the semiconductor structures during laser lift-off is extracted from a continuous secondary substrate and replaced by the elastomeric polymer layer on the receiving plate. This eliminates the need for bonding a separate secondary substrate and subsequent dicing operations, simplifying the overall process while maintaining structural stability.
3Manufacturing precision
If the laser beam is focused to lift off semiconductor structures, then precise separation is achieved, but momentum transfer during lift-off causes device leakage and reliability issues
Solution Approach 1:
The harmful momentum transfer during laser lift-off is converted into a beneficial effect by using the elastomeric polymer layer to absorb and dissipate this momentum. The polymer layer transforms the potentially damaging kinetic energy into harmless deformation of the polymer itself, protecting the semiconductor structures from damage.
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, high-yield LED dice without damage, reducing costs and improving reliability by absorbing momentum energy and allowing for precise placement of semiconductor structures without the need for secondary substrates or dicing.
Implementation Method 1
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 2
the elastomeric polymer layer on the receiving plate functions as a shock absorber to absorb kinetic energy from the semiconductor structures
Implementation Method 3
the laser beam carries an energy density well below an absorption threshold of the substrate, allowing it to transmit through the substrate. In contrast, the laser energy density is high enough to cause photo-inducted decomposition of the semiconductor layer at the interface with the substrate
Implementation Method 4
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.