SiC Monolayer Buffer for Group III Nitride on Silicon
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Solution Overview
Problem
Current methods for growing high-quality group III nitride layers on silicon substrates face challenges due to lattice and thermal mismatch, leading to poor crystalline structure and interface quality, particularly with the use of AlN buffer layers and SiC layers formed through hydrocarbon carbonization, which require high temperatures and result in rough interfaces.
Innovation Solution
A method involving the formation of a silicon carbide (SiC) atomic monolayer on a silicon substrate using ultra-low flow organometallic compounds, such as trimethylaluminum, in a MetalOrganic Chemical Vapour Deposition (MOCVD) reactor, followed by the growth of group III nitride layers like AlN, which prevents Si diffusion, protects the substrate, and introduces compressive stress for improved crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If AlN buffer layer is used between silicon substrate and GaN layer, then crystalline structure is improved, but lattice mismatch and thermal stress remain problematic
Solution Approach 1:
The patent introduces an AlGaN intermediate layer with graded composition between the AlN buffer layer and GaN layer. This intermediate layer acts as a mediator that gradually transitions the lattice constant and thermal properties, reducing the abrupt mismatch at interfaces and thereby improving both crystalline structure quality and interface stability.
Solution Approach 2:
The patent employs graded buffering where the aluminum composition in the AlGaN layer is gradually changed from high aluminum content near the AlN buffer to lower aluminum content near the GaN layer. This parameter change in composition allows progressive adaptation to lattice and thermal differences, resolving the contradiction between achieving good crystalline structure and maintaining interface stability.
2Quantity of substance
If hydrocarbons are used to carbonize silicon surface for SiC layer formation, then SiC layer is formed, but substrate temperature must be much higher and interface becomes rough
Solution Approach 1:
The patent replaces the conventional hydrocarbon-based chemical vapor deposition method with a molecular beam epitaxy (MBE) approach using elemental carbon source. This substitution of the deposition mechanism allows SiC layer formation at lower temperatures with better interface control, avoiding the rough interfaces caused by high-temperature hydrocarbon processing.
Solution Approach 2:
The patent changes the processing temperature parameter from high temperature (required for hydrocarbon carbonization) to lower temperature (using MBE with elemental carbon). This parameter change enables SiC layer formation while maintaining interface smoothness and avoiding the roughness problem associated with high-temperature hydrocarbon processing.
3Manufacturing precision
If Al pre-seeding is increased to improve surface morphology, then AlN nucleation layer morphology improves, but too much aluminum accumulates causing 3-D growth mode
Solution Approach 1:
The patent uses a short duration Al pre-seeding step (5 seconds) that provides just enough aluminum to improve surface morphology and initiate proper AlN nucleation, but stops before excessive aluminum accumulation occurs. This partial action approach achieves the beneficial morphology improvement while avoiding the harmful 3-D growth mode caused by aluminum excess.
Solution Approach 2:
The patent implements controlled pre-seeding where the aluminum deposition time and amount are precisely regulated based on the desired surface morphology outcome. This feedback-controlled approach ensures that aluminum is deposited only to the extent needed for morphology improvement, preventing over-deposition and the resulting 3-D growth instability.
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 achieves high-quality group III nitride layers with full width at half maximum (FWHM) values below 1000 arc sec, significantly improving crystalline quality and reducing stress, enabling the production of semiconductor devices like FETs, LEDs, and solar cells with enhanced performance.
Implementation Method 1
providing at least one organometallic compound which contains Al, in a flow of less than 5 μmol/min... forming a silicon carbide (SiC) atomic monolayer on a silicon substrate using ultra-low flow organometallic compounds, such as trimethylaluminum, in a MetalOrganic Chemical Vapour Deposition (MOCVD) reactor
Data Source
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AI summary
The present invention relates to semiconductor process technology and devices. In particular, the present invention relates to a method for forming a high quality group III nitride layer on a silicon substrate and to a device obtainable therefrom. According to the method, a pre-dosing step is applied to a silicon substrate, wherein the substrate is exposed to at least 0,01 µmol/cm2 of one or more organometallic compounds containing Al, in a flow of less than 5 µmol/min. The invention is equally related to the semiconductor structure obtained by the method, and to a device comprising said structure.