Vertical GaN Back Electrode Structure for Low Contact Resistance
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Solution Overview
Problem
In the manufacturing of vertical GaN semiconductor devices, achieving high adhesion of the back electrode while reducing contact resistance and thermal resistance is challenging, especially when using laser peeling techniques, as the flattening process before forming the back surface electrode can hinder adhesion and increase contact resistance.
Innovation Solution
A GaN semiconductor device with a chip formation substrate featuring irregularities such as trapezoidal convex portions and concave portions on the back surface, which are flattened to ensure uniform height and varying depth, allowing for high adhesion of the back electrode, and a method involving laser irradiation to form a transformation layer for peeling and subsequent CMP flattening to enhance contact area and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the back surface is flattened before forming the back surface electrode, then the manufacturing process is simplified, but the adhesion between the back surface electrode and the GaN substrate deteriorates
Solution Approach 1:
The back surface is flattened in advance before forming the back surface electrode, creating a preliminarily processed surface that facilitates subsequent electrode formation while maintaining adequate adhesion through the controlled flattening process
2Reliability
If the back surface is thinned to reduce thermal resistance, then the thermal performance is improved, but the structural strength and adhesion may deteriorate
Solution Approach 1:
The back surface undergoes localized thinning and flattening treatments in specific regions, creating areas with different thicknesses and surface qualities that optimize both thermal resistance reduction and structural strength maintenance in different zones of the substrate
3Reliability
If contact resistance is reduced by improving back surface contact, then thermal resistance is reduced, but the manufacturing complexity increases
Solution Approach 1:
The surface parameters of the back surface are modified through controlled flattening and thinning processes, changing the physical characteristics such as surface roughness and thickness to achieve reduced contact resistance and thermal resistance through parameter optimization rather than complex structural modifications
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
The solution achieves high adhesion and reduced contact resistance of the back electrode, thereby lowering thermal resistance and improving the overall performance of the vertical GaN device, as demonstrated by proportional I-V characteristics and increased contact area.
Implementation Method 1
laser irradiation to form a transformation layer for peeling
Implementation Method 2
subsequent CMP flattening to enhance contact area and adhesion
Data Source
AI summary
A gallium nitride semiconductor device includes: a chip formation substrate made of gallium nitride and having one surface and an other surface opposite to the one surface; a one surface side element component disposed on the one surface and providing a component of an one surface side of a semiconductor element; and a metal film constituting a back surface electrode in contact with the other surface. The other surface has an irregularity provided by a plurality of convex portions with a trapezoidal cross section and a plurality of concave portions located between the convex portions; and an upper base surface of the trapezoidal cross section in each of the plurality of convex portions is opposed to the one surface.