AlGaN Buffer Layer Crystallinity Productivity
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Solution Overview
Problem
Conventional methods for forming group III nitride semiconductor thin films on sapphire substrates face challenges in achieving low threading dislocation densities, leading to trade-offs between crystallinity and productivity, with increased film thickness required for improved crystallinity but resulting in higher costs and reduced productivity.
Innovation Solution
A film forming method involving the formation of a buffer layer with a wurtzite structure on a sapphire substrate using AlxGa1−xN with added substances like C, Si, Ge, Mg, Zn, or Cr, allowing for the achievement of high crystallinity with a thinner foundation layer, reducing threading dislocation density and increasing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the film thickness of the foundation layer is increased to improve crystallinity and reduce threading dislocation density, then the crystallinity is improved, but the productivity is reduced due to longer film formation time
Solution Approach 1:
The invention changes the compositional parameters of the buffer layer by incorporating specific substances (C, Si, Ge, Mg, Zn, or Cr) into the AlN buffer layer. This compositional modification allows the foundation layer to achieve high crystallinity with reduced threading dislocation density at a thinner film thickness, thereby improving productivity without sacrificing manufacturing precision
Solution Approach 2:
The invention creates a composite buffer layer structure by combining AlN with additional substances (forming AlxGa1-xN with added C, Si, Ge, Mg, Zn, or Cr). This composite material approach enhances the buffer layer's ability to reduce threading dislocations, allowing the foundation layer to achieve high crystallinity at reduced thickness
2Productivity
If conventional MOCVD is used to grow group III nitride semiconductor thin films on sapphire substrates, then productivity is high, but threading dislocation density remains high (10^9 to 10^10 cm^-2)
Solution Approach 1:
The invention introduces a modified buffer layer as an intermediary between the sapphire substrate and the foundation layer. This buffer layer, containing AlN with added substances, acts as a mediator that reduces threading dislocation propagation while maintaining the high productivity of MOCVD processing
Solution Approach 2:
The invention modifies the buffer layer composition parameters by adding specific substances to AlN, which changes the dislocation reduction mechanism and allows achieving lower threading dislocation densities while maintaining high productivity through standard MOCVD processes
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 method enables the production of high-quality group III nitride semiconductor thin films with reduced threading dislocation density and improved crystallinity at a smaller film thickness, enhancing productivity by shortening the film formation time while maintaining favorable threading dislocation density.
Implementation Method 1
forming a buffer layer made of an AlN film and deposited by sputtering on a sapphire substrate
Implementation Method 2
forming a foundation layer made of group III nitride semiconductor thereon by the MOCVD
Data Source
AI summary
An object of the present invention is to provide a film formation technique having high productivity by realizing a foundation layer having excellent crystallinity with a small film thickness of about 2 .mu.m. An embodiment of the present invention relates to a film forming method which includes the step of forming a buffer layer by sputtering on a sapphire substrate held by a substrate holder. The buffer layer includes an epitaxial film having a wurtzite structure prepared by adding at least one substance selected from the group consisting of C, Si, Ge, Mg, Zn, Mn, and Cr to Al.sub.xGa.sub.1-xN (where 0.ltoreq.x.ltoreq.1).