Buried Oxide Transcap Devices for High Voltage Operation
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Solution Overview
Problem
Semiconductor variable capacitors face challenges in achieving high operating voltage, quality factor, and linearity while minimizing interface charge traps, which degrade device performance.
Innovation Solution
The semiconductor variable capacitor design includes a semiconductor region between non-insulative regions with different doping types, a buried oxide layer, and a silicide-blocking layer to reduce interface charge traps and enhance performance, allowing for higher voltage operation and improved capacitance control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional variable capacitor design is used, then the device can achieve basic capacitance variation, but interface charge traps degrade the quality factor and linearity at higher operating voltages
Solution Approach 1:
The patent introduces a buried oxide layer as an intermediary between the semiconductor region and the substrate, and a silicide-blocking layer as another intermediary to prevent charge trap formation at interfaces. These intermediary layers isolate the semiconductor region from direct contact with surfaces that would otherwise generate interface charge traps, thereby maintaining high quality factor and linearity at higher operating voltages
2Adaptability or versatility
If the operating voltage is increased, then the capacitance control range is improved, but interface charge traps increase and degrade device performance
Solution Approach 1:
The buried oxide layer and silicide-blocking layer serve as protective intermediaries that enable the device to operate at higher voltages to achieve broader capacitance control range, while preventing the formation of interface charge traps that would otherwise degrade performance at these higher voltage levels
3Reliability
If a simple capacitor structure is used, then the device complexity is low, but the ability to operate at high voltage with high quality factor is limited
Solution Approach 1:
The patent segments the capacitor structure into distinct functional layers: a semiconductor region, a buried oxide layer, and a silicide-blocking layer. Each layer performs a specific function - the semiconductor region provides capacitance variation, the buried oxide layer isolates from substrate, and the silicide-blocking layer prevents charge trap formation. This segmentation enables high voltage operation with high quality factor while keeping the overall structure relatively simple and manufacturable
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 design enables semiconductor variable capacitors to operate at higher voltages with increased quality factor and linearity, reducing performance degradation from interface charge traps and optimizing capacitance control.
Implementation Method 1
A variable capacitor, which may be referred to as a varactor, is often used in inductor-capacitor (LC) circuits to set the resonance frequency of an oscillator... Any junction diode exhibits this effect (including p-n junctions in transistors), but devices used as variable capacitance diodes are designed with a large junction area and a doping profile specifically chosen to improve the device performance
Data Source
AI summary
Certain aspects of the present disclosure provide semiconductor variable capacitors. One example semiconductor variable capacitor generally includes a semiconductor region, a first insulator region disposed below the semiconductor region, a first non-insulative region disposed below the first insulator region, a second non-insulative region disposed adjacent to the semiconductor region, and a third non-insulative region disposed adjacent to the semiconductor region, wherein the semiconductor region is disposed between the second non-insulative region and the third non-insulative region. In certain aspects, the semiconductor variable capacitor may include a second insulator region disposed above the semiconductor region and a second semiconductor region disposed above the second insulator region.