Oxygen-Doped Semiconductor Layer for RF Isolation
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Solution Overview
Problem
In semiconductor manufacturing, particularly for radio frequency (RF) applications, the high resistivity handle silicon wafer in composite substrates like silicon-on-insulator (SOI) leads to carrier accumulation, causing cross-talk and non-linear distortion due to interactions between applied voltage and accumulated carriers, which deteriorates device performance.
Innovation Solution
A composite semiconductor substrate is developed with an oxygen-doped crystalline semiconductor layer acting as a trap-rich layer, formed by deposition, which includes polycrystalline silicon with oxygen dopants to trap carriers, reduce parasitic capacitance, and inhibit grain growth, thereby alleviating leakage current and non-linear distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high resistivity handle silicon wafer is used in composite substrate, then device-to-device isolation and passive device Q-factors are improved, but carrier accumulation occurs at the interface causing cross-talk and non-linear distortion
Solution Approach 1:
An intermediate layer (buried oxide layer or depleted layer) is introduced between the handle silicon wafer and the device layer. This intermediary structure prevents direct interaction between applied voltage and accumulated carriers at the interface, thereby eliminating cross-talk and non-linear distortion while preserving the high resistivity benefits for device isolation and Q-factors.
Solution Approach 2:
The electrical properties of the handle silicon wafer are modified by creating a depleted layer through thermal processing or plasma treatment. This changes the carrier concentration and distribution parameters, reducing carrier accumulation at the interface and preventing the harmful interactions that cause cross-talk and distortion.
2Object-generated harmful factors
If carrier accumulation is reduced by increasing resistivity, then cross-talk is reduced, but leakage current increases
Solution Approach 1:
Different regions of the substrate are given different electrical properties: the bulk handle silicon wafer maintains high resistivity to prevent cross-talk, while the interface region is modified through selective thermal or plasma treatment to create a depleted layer that controls carrier accumulation locally. This localized modification reduces cross-talk without creating excessive leakage current paths.
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 oxygen-doped crystalline semiconductor layer effectively mitigates parasitic capacitance and leakage current, improving RF device performance by reducing cross-talk and non-linear distortion, and allows for a flatter surface without the need for planarization operations, thus enhancing manufacturing efficiency.
Implementation Method 1
an oxygen-doped crystalline semiconductor layer acting as a trap-rich layer... includes polycrystalline silicon with oxygen dopants to trap carriers
Implementation Method 2
formed by deposition
Data Source
AI summary
A composite semiconductor substrate includes a semiconductor substrate, an oxygen-doped crystalline semiconductor layer and an insulative layer. The oxygen-doped crystalline semiconductor layer is over the semiconductor substrate, and the oxygen-doped crystalline semiconductor layer includes a crystalline semiconductor material and a plurality of oxygen dopants. The insulative layer is over the oxygen-doped crystalline semiconductor layer.