High-Resistivity Handle Substrate with SiC Dopant Barrier
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Solution Overview
Problem
Existing methods for forming high resistivity handle substrates for composite substrates face issues such as chamber contamination, particle formation, and reduced manufacturing throughput due to simultaneous use of multiple precursor gases, and dopant migration leading to reduced RF performance.
Innovation Solution
A method involving a monocrystalline silicon base substrate exposed to a single carbon precursor at reduced pressure to form a polycrystalline silicon carbide layer, followed by a polycrystalline charge trapping layer, which includes a silicon intrinsic epitaxial layer if necessary, to maintain high resistivity and prevent dopant diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple precursor gases are used simultaneously to form the intermediate layer, then the layer formation speed increases, but chamber contamination and particle formation occur
Solution Approach 1:
The process is divided into two separate steps: first forming the intermediate silicon-carbon alloy layer using only carbon precursor, then forming the polycrystalline silicon layer using silicon precursor. This segmentation prevents simultaneous gas reactions that cause chamber contamination while maintaining overall productivity.
Solution Approach 2:
The intermediate silicon-carbon alloy layer is formed in advance before the polycrystalline silicon layer. This preliminary action creates a foundation layer that prevents direct contact between silicon precursor and chamber walls, eliminating contamination while enabling subsequent rapid silicon layer deposition.
2Ease of manufacture
If standard CZ silicon substrates are used, then manufacturing cost is reduced, but dopant migration occurs reducing RF performance
Solution Approach 1:
The intermediate silicon-carbon alloy layer acts as a diffusion barrier between the CZ silicon substrate and the polycrystalline silicon layer. This intermediary prevents boron dopant migration from the substrate while allowing the use of cost-effective standard CZ silicon substrates.
Solution Approach 2:
The charge trapping layer is formed as a composite structure with an intermediate silicon-carbon alloy layer and a polycrystalline silicon layer. This composite structure provides both the cost advantage of CZ substrates and the RF performance required, as the silicon-carbon layer blocks dopant diffusion.
3Reliability
If the charge trapping layer is made thicker to improve RF performance, then dopant diffusion is better blocked, but manufacturing time increases
Solution Approach 1:
The charge trapping layer is segmented into two parts: a thin intermediate silicon-carbon alloy layer that provides the primary dopant diffusion barrier, and a polycrystalline silicon layer that provides additional charge trapping capability. This segmentation achieves effective dopant blocking with reduced total thickness compared to a single thick polycrystalline layer.
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 ensures high resistivity and rapid layer formation with minimal contamination, preserving RF performance by forming a thick, stoichiometric silicon carbide layer that acts as a diffusion barrier, reducing chamber cleaning frequency and improving throughput.
Implementation Method 1
exposing the base substrate to a single carbon precursor at a pressure below atmospheric pressure to form a polycrystalline silicon carbide layer
Implementation Method 2
forming a thick, stoichiometric silicon carbide layer that acts as a diffusion barrier
Implementation Method 3
The multilayer structure of the charge trapping layer makes it possible to prevent the phenomenon of recrystallization of the main polycrystalline layer when the substrate is exposed to a high temperature
Data Source
AI summary
A method for forming a high resistivity handle substrate for a composite substrate comprises: 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 having a thickness 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.