Laser Lift-Off Sequencing for Gas-Controlled Epitaxial Separation
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Solution Overview
Problem
The laser lift-off method for separating semiconductor-epitaxial structures from sapphire substrates often causes stress and bending deformation due to gas production during the separation process, leading to potential damage to the semiconductor-epitaxial structure.
Innovation Solution
A new laser lift-off method that initiates separation from the edge area of a semiconductor device, evacuates gas produced during the process, and then proceeds to separate in an inner area, using a pressing device to manage stress and prevent overbending, ensuring gas is evacuated and does not cause damage to the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser irradiation is applied to separate semiconductor-epitaxial structure from substrate, then separation is achieved, but gas production causes stress and bending deformation that damages the structure
Solution Approach 1:
The laser irradiation process is divided into multiple scanning paths: an outer scanning path that irradiates peripheral regions first to create initial separation and evacuation channels, followed by an inner scanning path that irradiates central regions. This segmentation allows gas to escape through the outer path while the inner path completes the separation, preventing gas accumulation and reducing stress-induced deformation.
2Productivity
If laser separates substrate and semiconductor-epitaxial structure, then separation is achieved, but yet-to-separate portions are torn off by overbending
Solution Approach 1:
The outer scanning path performs preliminary separation at the peripheral regions before the inner scanning path processes the central regions. This preliminary action creates initial gaps and evacuation channels that allow subsequent gas release without causing overbending or tearing of the remaining connected portions, thereby maintaining structural integrity throughout the separation process.
3Power
If gas is produced during laser separation, then separation reaction occurs, but gas sneaks into yet-to-separate portions and causes stress cracking
Solution Approach 1:
The outer scanning path extracts gas from the separation zone by creating open channels at the periphery through which gas can escape. By removing gas from the system through these outer channels before the inner scanning path completes separation, the harmful gas is taken out of the critical zone, preventing stress cracking and improving reliability.
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 effectively prevents damage to the semiconductor-epitaxial structure by evacuating gas produced during separation, reducing stress and deformation, and ensuring complete separation without tearing or bulging of the substrate and semiconductor-epitaxial structure portions.
Implementation Method 1
irradiate a laser onto an edge area of a semiconductor device, wherein light of the laser is projected on a side of the semiconductor-epitaxial structure connected to the substrate
Implementation Method 2
a side of the semiconductor-epitaxial structure connected to the substrate absorbs energy from the laser and starts thermal decomposition
Data Source
AI summary
The present disclosure provides a laser lift-off method for separating substrate and semiconductor-epitaxial structure, which includes: providing at least one semiconductor device, wherein the semiconductor device includes a substrate and at least one semiconductor-epitaxial structure disposed in a stack-up manner; irradiating a laser onto an edge area of the semiconductor device to separate portions of the substrate and the semiconductor-epitaxial structure in the edge area; and pressing against the edge area of the semiconductor device vis a pressing device, then irradiating the laser onto an inner area of the semiconductor device to separate portions of the substrate and the semiconductor-epitaxial structure in the inner area wherein gas is generated during separating the portions of the substrate and the semiconductor-epitaxial structure in the inner area and evacuated from the edge area, to prevent damage of the semiconductor-epitaxial structure during the separating process.