High Resistivity SOI Substrate Dielectric Barrier
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Solution Overview
Problem
Current semiconductor on insulator (SOI) substrates for radiofrequency applications face challenges with low resistivity issues due to contamination and recrystallization of polycrystalline silicon layers, leading to reduced performance and stability during heat treatments.
Innovation Solution
A method involving the formation of a dielectric material layer, such as silicon nitride or silicon oxide, between the high resistivity silicon substrate and the polycrystalline silicon layer, with a thickness of 0.5 to 10 nm, to prevent recrystallization and trap contaminants, ensuring the polycrystalline silicon layer maintains high resistivity and stability during thermal processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polycrystalline silicon layer is deposited between the oxide layer and the HR silicon substrate, then the substrate resistivity is improved, but the polycrystalline silicon recrystallizes at high temperature causing doping agents to diffuse and reduce substrate resistivity
Solution Approach 1:
A thin dielectric material layer (0.5-10 nm) is introduced as an intermediary between the polycrystalline silicon layer and the HR silicon substrate. This dielectric layer acts as a barrier that prevents direct thermal interaction and doping agent diffusion, thereby maintaining the polycrystalline silicon structure stability during heat treatments while preserving the high resistivity characteristics.
Solution Approach 2:
The structure combines multiple materials with complementary properties: the polycrystalline silicon layer provides electrical passivation and high resistivity, while the thin dielectric material layer provides thermal and diffusion barrier properties. This composite structure resolves the contradiction by leveraging the strengths of each material while mitigating their individual weaknesses.
2Reliability
If heat treatment is applied to make oxygen precipitate and obtain high resistivity, then substrate resistivity is improved, but oxygen atoms diffuse in the substrate forming low resistivity regions
Solution Approach 1:
The thin dielectric material layer serves as a barrier that controls and limits oxygen atom diffusion during heat treatment. By preventing uncontrolled oxygen migration, this intermediary layer enables the heat treatment process to successfully precipitate oxygen and form high resistivity regions without creating unwanted low resistivity zones, thereby improving both resistivity and manufacturing precision.
3Reliability
If surface contamination occurs before bonding, then low resistivity layer is formed under the oxide layer, but the contaminants are encapsulated at the bonding interface
Solution Approach 1:
The thin dielectric material layer is deposited on the HR silicon substrate before bonding, serving as a preliminary protective barrier. This preliminary action prevents surface contaminants from directly contacting and affecting the substrate during the bonding process, thereby maintaining high resistivity characteristics even when contamination occurs.
Solution Approach 2:
The dielectric material layer acts as an intermediary barrier between external contaminants and the HR silicon substrate. This intermediary structure encapsulates contaminants away from the substrate, preventing them from forming low resistivity regions and maintaining the electrical properties of the substrate.
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 effectively maintains high resistivity and stability of the polycrystalline silicon layer, reducing the impact of heat treatments and minimizing resistivity drops, thereby enhancing the performance and reliability of radiofrequency devices.
Implementation Method 1
formation of a dielectric material layer, such as silicon nitride or silicon oxide, between the high resistivity silicon substrate and the polycrystalline silicon layer... to prevent recrystallization
Implementation Method 2
trap contaminants, ensuring the polycrystalline silicon layer maintains high resistivity and stability during thermal processes
Data Source
Figure 1~2
Figure 3~4B
Figure 4C~4D
AI summary
The invention relates to a method for manufacturing a semiconductor on insulator type substrate for radiofrequency applications, comprising the following steps in sequence: (a) provision of a silicon substrate (1) with an electrical resistivity of more than 500 Ohm. cm, (b) formation of a polycrystalline silicon layer (4) on said substrate (1), said method comprising a step between steps a) and b) to form a dielectric material layer (5), different from a native oxide layer, on the substrate (1), between 0.5 and 10 nm thick.