GaN Substrate Division via Multiphoton Absorption Laser Grooving
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Solution Overview
Problem
Group III nitride semiconductor substrates, such as GaN, are challenging to cleave accurately due to poor cleavability, leading to deviations in division guide grooves during chip division, resulting in defective appearances and reliability issues due to debris contamination from laser processing.
Innovation Solution
A method involving laser processing with specific wavelength and energy density to form division guide grooves using multiphoton absorption, followed by debris removal with a lower energy density laser beam to prevent substrate damage and enhance surface cleanliness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deep division guide grooves are formed on GaN substrate by laser processing, then the cleavability and division precision are improved, but the substrate material is heated and scattered as debris, causing surface contamination
Solution Approach 1:
The laser processing is divided into two separate steps: first forming the division guide groove, then removing debris. This segmentation allows each step to be optimized independently, solving the contradiction between groove formation and debris generation.
Solution Approach 2:
The debris generated during laser processing is not discarded but utilized as a marker. The debris pattern created by the laser beam serves as a visual guide for subsequent breaking operations, converting the harmful debris into a beneficial positioning reference.
2Manufacturing precision
If high energy density laser beam is applied to form division guide groove, then the groove depth and precision are improved, but the substrate surface is damaged by excessive heating
Solution Approach 1:
The laser processing parameters are segmented into two distinct regimes: high energy density for groove formation and low energy density for debris removal. This allows the substrate to withstand the intense processing without cumulative damage.
Solution Approach 2:
The laser beam application follows a periodic pattern with two distinct phases: a high-intensity phase for groove formation followed by a low-intensity phase for debris removal. This periodic variation in energy density prevents continuous overheating while maintaining processing effectiveness.
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 allows for precise substrate division with improved reliability and appearance of nitride semiconductor devices by selectively removing debris without damaging the substrate, reducing defects in die bonding and wire bonding.
Implementation Method 1
forming a division guide groove by applying a laser beam having a wavelength and energy density causing multiphoton absorption to the surface of a substrate
Implementation Method 2
the debris is sublimated by absorbing the laser beam having the wavelength not absorbed by the substrate material
Implementation Method 3
removing deposits (particularly debris resulting from transformation and scattering of the substrate material in the step of forming the division guide groove) from the surface of the substrate by applying a laser beam
Data Source
AI summary
A method of manufacturing a nitride semiconductor device includes the steps of: forming a division guide groove by applying a laser beam having a wavelength and energy density causing multiphoton absorption to a surface of a substrate having a group III nitride semiconductor layer grown on a major surface thereof; removing deposits from the surface of the substrate by applying a laser beam having the wavelength to the surface of the substrate at energy density causing substantially no multiphoton absorption on the substrate; and dividing the substrate along the division guide groove.