Epitaxial Layer Configuration for SOI Backside Bias Shielding
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Solution Overview
Problem
Silicon-on-insulator (SOI) semiconductor devices suffer from the backside bias effect, which affects the breakdown voltage of metal-oxide-semiconductor field-effect transistors and is not adequately addressed by existing technologies.
Innovation Solution
A semiconductor device structure is developed with a stacked epitaxial layer configuration of specific conductivity types (p-type, n-type, p-type) formed over a substrate and oxide layer, using epitaxial growth processes to minimize defects and reduce current leakage, effectively shielding signal interference from the backside substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If silicon-on-insulator substrate is used, then leakage current is reduced and power efficiency is improved, but backside bias effect occurs affecting breakdown voltage
Solution Approach 1:
The semiconductor substrate is segmented into multiple functional layers: a base silicon layer, a buried oxide layer, and a stacked epitaxial layer structure with alternating conductivity types (p-n-p or n-p-n). This segmentation isolates the active device region from the substrate, reducing leakage current while the epitaxial stack shields the breakdown voltage from backside bias effects.
Solution Approach 2:
The buried oxide layer serves as an intermediary between the base silicon layer and the epitaxial layers, providing electrical isolation. The epitaxial layers with alternating conductivity types act as an intermediate shield that protects the MOSFET breakdown voltage from substrate bias effects, allowing the SOI structure to maintain both low leakage and stable breakdown voltage.
2Reliability
If additional circuits are added to minimize backside bias effect, then breakdown voltage stability is improved, but device complexity increases
Solution Approach 1:
The backside bias effect is extracted and addressed at the substrate level through the epitaxial layer stack rather than requiring additional compensation circuits in the device logic. This extracts the problem from the circuit domain and solves it through physical structure, reducing overall device complexity.
Solution Approach 2:
The alternating conductivity type epitaxial layers convert the potential harm of substrate bias effects into a beneficial shielding mechanism. The p-n-p or n-p-n structure creates internal field effects that counteract backside bias, transforming what would be a harmful interference into a protective feature without adding circuit complexity.
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 epitaxial layer configuration reduces the influence of the backside bias effect, improving the semiconductor device's performance by maintaining uniform breakdown voltage and stability under varying currents.
Implementation Method 1
forming a first epitaxial layer over the oxide layer; forming a second epitaxial layer over the first epitaxial layer; and forming a third epitaxial layer over the second epitaxial layer
Data Source
AI summary
A semiconductor device is provided. The semiconductor device includes a substrate, an oxide layer disposed over the substrate, and a first epitaxial layer disposed over the oxide layer. The first epitaxial layer has the first conductivity type. The semiconductor device also includes a second epitaxial layer disposed over the first epitaxial layer and a third epitaxial layer disposed over the second epitaxial layer. The second epitaxial layer has a second conductivity type that is opposite to the first conductivity type. The third epitaxial layer has the first conductivity type.