Diamond Substrate With Thin SiC Layer for Reliable GaN Bonding
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Solution Overview
Problem
Existing semiconductor laminated structures face issues with bonding reliability due to melt-back reactions at high temperatures, poor heat dissipation from using titanium films, and unclear crystal growth of gallium nitride on silicon carbide substrates, leading to reduced reliability and heat dissipation.
Innovation Solution
A substrate for semiconductor devices comprising a diamond substrate with a thin silicon carbide layer having a thickness of 20 nm or less and an arithmetic mean roughness of 0.5 nm or less, where the silicon carbide layer is amorphous or polycrystalline, facilitating easy bonding with a nitride or oxide semiconductor layer and enhancing heat dissipation and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin silicon film is deposited on diamond substrate to enable bonding, then bonding capability is improved, but melt-back reaction occurs at high temperature reducing reliability
Solution Approach 1:
The patent changes the material parameter from silicon to silicon carbide, which has higher thermal stability and resistance to melt-back reactions. The silicon carbide layer maintains the bonding function while withstanding high temperature processing (800°C or higher) without undergoing harmful reactions with gallium nitride, thus resolving the contradiction between bonding capability and reliability at high temperature.
Solution Approach 2:
The patent uses a composite structure consisting of a diamond substrate with a silicon carbide layer deposited on its surface. This composite material combines the high thermal conductivity of diamond with the high temperature stability of silicon carbide, achieving both easy bonding and reliability under high temperature conditions.
2Ease of manufacture
If a titanium film is used to bond silicon carbide substrate to diamond substrate, then bonding is achieved, but thermal conductivity decreases due to titanium's lower thermal conductivity
Solution Approach 1:
The patent removes the titanium bonding layer from the structure and directly bonds the silicon carbide substrate to the diamond substrate. This extraction of the problematic titanium layer eliminates the thermal conductivity bottleneck while maintaining bonding capability through direct silicon carbide-to-diamond bonding, thus improving heat dissipation without sacrificing bonding functionality.
Solution Approach 2:
The patent creates a direct bond between silicon carbide and diamond substrates, forming a composite structure with high thermal conductivity throughout. This eliminates the need for low thermal conductivity bonding materials like titanium, maintaining excellent heat dissipation properties while achieving reliable bonding.
3Ease of operation
If diamond substrate surface is left rough, then natural surface properties are maintained, but bonding to semiconductor layer becomes difficult
Solution Approach 1:
The patent applies a silicon carbide layer to the diamond substrate surface, creating a localized modification that provides bonding functionality. The silicon carbide layer has different surface properties than the underlying diamond, offering improved bonding characteristics to the semiconductor layer while the bulk diamond substrate retains its natural properties including high thermal conductivity.
4Strength
If silicon carbide substrate is used with thickness greater than 20 nm, then structural stability is improved, but heat dissipation performance deteriorates
Solution Approach 1:
The patent optimizes the silicon carbide layer thickness to 20 nm or less, finding the optimal balance between structural stability and heat dissipation. This thin thickness parameter allows sufficient structural support while minimizing thermal resistance, enabling excellent heat dissipation through the diamond substrate without compromising the stability of the layered structure.
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 proposed solution allows for reliable bonding of diamond substrates with semiconductor layers, improving heat dissipation and heat resistance by reducing thermal resistance at the bonding interface and ensuring stable crystal growth.
Implementation Method 1
depositing silicon carbide on a part or all of one surface of a diamond substrate to form a silicon carbide layer
Implementation Method 2
diamond substrates, which have a high thermal conductivity of 500 W/mK or more
Data Source
AI summary
A substrate (1) for a semiconductor device of the present invention includes a diamond substrate (10) and a silicon carbide layer (20) located on a part or all of one surface (10a) of the diamond substrate (10), wherein the silicon carbide layer (20) has a thickness of 20 nm or less, and wherein a surface (20a) of the silicon carbide layer (20) has an arithmetic mean roughness Ra of 0.5 nm or less.