Bonded Substrate for Epitaxial Growth via Direct Bonding
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Solution Overview
Problem
Conventional semiconductor manufacturing processes face challenges in achieving substrates with high strength, low leakage current, efficient heat dissipation, and high breakdown voltage, particularly due to the use of SOI substrates with oxide layers as insulators, which are poor heat conductors, and heavily doped substrates that can bow or break during epitaxial growth.
Innovation Solution
A method involving the direct bonding of a heavily doped first substrate with a lightly doped second substrate, followed by annealing to form a high impedance layer, which eliminates the need for oxide layers and enhances heat dissipation, reduces leakage current, and increases substrate strength and breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an oxide layer is added into two silicon substrates to be used as an insulator and bonding layer, then leakage current is reduced, but heat dissipation efficiency deteriorates
Solution Approach 1:
The invention extracts and removes the oxide layer from the bonding interface between substrates. By eliminating the oxide layer that causes poor heat conduction, the patent achieves direct substrate bonding while maintaining electrical insulation through alternative means, thus resolving the contradiction between reducing leakage current and improving heat dissipation efficiency
Solution Approach 2:
The invention changes the bonding parameters by using direct bonding without oxide layers. This parameter change allows the bonding interface to have both good electrical insulation properties and excellent thermal conduction properties, simultaneously addressing both requirements that were previously conflicting
2Strength
If a heavily doped substrate is utilized to increase substrate strength, then substrate strength is improved, but leakage current increases due to low resistivity
Solution Approach 1:
The invention applies local quality by creating a bonded substrate structure where different regions have different doping concentrations. The first substrate can be heavily doped for strength while the second substrate has appropriate doping for low leakage current, and the bonding interface provides electrical insulation. This spatial differentiation of doping quality resolves the contradiction between substrate strength and leakage current reduction
3Strength
If a heavily doped substrate is used in the epitaxial growth process, then substrate strength is improved, but the substrate tends to bow or break due to lattice coefficient mismatch
Solution Approach 1:
The invention segments the substrate into multiple bonded substrates with different doping concentrations and material properties. This segmentation allows each substrate to be optimized for specific functions while the bonding interface accommodates lattice mismatch, preventing bowing and breaking during epitaxial growth. The segmented structure resolves the contradiction between strength and stability
4Strength
If an oxide layer is used as a bonding layer between substrates, then bonding is achieved, but heat dissipation efficiency deteriorates
Solution Approach 1:
The invention extracts and eliminates the oxide layer from the bonding interface. By removing this thermally insulating layer, the patent enables direct bonding between substrates, achieving both strong mechanical bonding and excellent thermal conduction. This extraction resolves the contradiction between bonding strength and heat dissipation efficiency
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 bonded substrate achieves improved heat dissipation efficiency, reduced leakage current, increased substrate strength, and higher breakdown voltage, making it suitable for high-power and high-frequency semiconductor applications without the drawbacks of conventional SOI substrates.
Implementation Method 1
directly bonding a first surface of the first substrate with a second surface of the second substrate to form a bonded substrate
Implementation Method 2
annealing the bonded substrate to form a high impedance layer in the bonded substrate
Implementation Method 3
annealing the bonded substrate to form a high impedance layer
Data Source
AI summary
A bonded substrate for epitaxial growth and a method for forming the same are disclosed. The method includes steps of providing a first substrate, which has a first dopant concentration; providing a second substrate, which has a second dopant concentration, wherein the second dopant concentration is lower than the first dopant concentration; directly bonding a first surface of the first substrate with a second surface of the second substrate to form a bonded substrate; annealing the bonded substrate to form a high impedance layer in the bonded substrate; and removing part of the second substrate to expose the high impedance layer depending on the requirements whereby, the bonded substrate formed by the method could have a heavily doped substrate which includes a stronger strength and the impedance layer formed thereon, which could effectively increase the substrate strength, reduce the leakage current, and sustains a higher breakdown voltage.