Composite Handle Substrate with SiC Diffusion Barrier for RF Resistivity
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Solution Overview
Problem
Existing methods for forming high resistivity handle substrates for composite substrates face challenges such as recrystallization of charge-trapping layers during high-temperature processing, leading to reduced RF performance, and issues with deposition of silicon and carbon species on chamber walls, which require extensive cleaning and can introduce dopants that reduce resistivity.
Innovation Solution
A method involving a monocrystalline silicon base substrate exposed to a carbon single precursor at reduced pressure to form a polycrystalline silicon carbide layer, followed by growth of a polycrystalline charge trapping layer, which acts as a diffusion barrier and maintains high resistivity characteristics, while minimizing dopant incorporation and chamber contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon and carbon alloy intermediate layer is formed by simultaneous flow of silicon and carbon precursor gases, then the charge-trapping layer is protected from recrystallization during high-temperature processing, but deposits form on chamber walls and susceptor requiring extensive cleaning
Solution Approach 1:
The process is segmented into three distinct sequential steps: first forming the silicon carbide intermediate layer using only carbon precursor, then forming the silicon charge-trapping layer using only silicon precursor, and finally forming the polycrystalline silicon layer. This segmentation prevents simultaneous deposition on chamber walls while maintaining the protective function of the intermediate layer.
Solution Approach 2:
The silicon carbide intermediate layer is formed in advance before the silicon charge-trapping layer. This preliminary action creates a protective barrier that prevents recrystallization of subsequent layers during high-temperature processing, while being formed under conditions that minimize chamber contamination.
2Ease of manufacture
If silicon and carbon precursor gases flow simultaneously to grow the intermediate layer, then the intermediate layer is formed, but particles are created and transported onto substrate surfaces rendering substrates unsuitable
Solution Approach 1:
The formation process is divided into separate sequential steps: first the silicon carbide intermediate layer is formed using carbon precursor alone, then the silicon charge-trapping layer is formed using silicon precursor alone. This eliminates simultaneous gas flow that generates particles, while still achieving the desired intermediate layer structure.
3Adaptability or versatility
If CZ silicon substrate with residual boron is used as base substrate, then the substrate is readily available, but boron migrates to the base wafer surface during charge trapping layer growth reducing resistivity
Solution Approach 1:
The silicon carbide intermediate layer acts as an intermediary barrier between the boron-containing CZ silicon substrate and the charge-trapping layer. This intermediate layer prevents boron migration to the surface during processing, maintaining high resistivity while allowing the use of readily available CZ substrates.
4Object-affected harmful factors
If extensive chamber cleaning by etching is performed to remove deposits, then chamber contamination is removed, but manufacturing time is increased reducing throughput
Solution Approach 1:
The harmful carbon-containing deposits are extracted from the chamber by eliminating the step that creates them. By forming the silicon carbide intermediate layer using only carbon precursor in a separate first step rather than simultaneous flow, the source of extensive chamber contamination is removed, eliminating the need for time-consuming cleaning cycles.
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 results in a high resistivity handle substrate with improved RF performance and reduced manufacturing complexity, as it forms a thick, stochiometric polycrystalline silicon carbide layer that effectively prevents dopant migration and maintains high resistivity, enhancing the substrate's performance and manufacturing efficiency.
Implementation Method 1
exposing the base substrate to a carbon single precursor at a pressure below atmospheric pressure to form a polycrystalline silicon carbide layer
Implementation Method 2
a thick, stochiometric polycrystalline silicon carbide layer that effectively prevents dopant migration and maintains high resistivity
Implementation Method 3
growing a polycrystalline charge trapping layer on the polycrystalline silicon carbide layer
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a method for forming a high resistivity handle substrate for a composite substrate, the method comprising : - providing a base substrate made of silicon; - exposing the base substrate to a carbon single precursor at a pressure below atmospheric pressure to form a polycrystalline silicon carbide layer of at least 10 nm on the surface of the base substrate; and then - growing a polycrystalline charge trapping layer on the carbon-containing layer.