MOSFET Back Gate Compensation Doping for Threshold Voltage Control
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Solution Overview
Problem
MOSFETs face challenges in adjusting threshold voltage without increasing channel doping, which leads to short channel effects and performance degradation as devices are scaled down, especially with the shrinking channel length.
Innovation Solution
A MOSFET design incorporating a back gate with first, second, and third compensation doping regions, where the back gate is doped differently under the source and drain regions, channel region, and adjacent areas, allowing for non-uniform doping profiles and adjustable threshold voltage through bias voltage application, reducing leakage current and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel doping concentration is increased to raise threshold voltage, then threshold voltage is improved, but resistance of source/drain regions increases
Solution Approach 1:
The patent implements local quality by applying different doping concentrations to different regions: high doping in source/drain regions to maintain low resistance, and controlled doping in the channel region to adjust threshold voltage. The compensation doping regions are locally positioned to affect threshold voltage without increasing source/drain resistance, as they are placed in the channel area rather than the contact regions.
2Productivity
If channel length is reduced for scaling, then integration density is improved, but short channel effects increase and threshold voltage control deteriorates
Solution Approach 1:
The patent applies parameter changes by introducing compensation doping regions with specific doping concentrations and spatial distributions. These parameter adjustments to the doping profile compensate for the shortened channel length effects, restoring threshold voltage control despite the reduced channel dimensions enabled by scaling for higher integration density.
Solution Approach 2:
The compensation doping regions are introduced to preemptively counteract the adverse effects of short channel phenomena before they severely degrade device performance. By pre-positioning these doping regions with appropriate concentrations, the patent prevents threshold voltage roll-off and other short channel effects that would otherwise dominate in scaled devices.
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 solution effectively adjusts the threshold voltage of MOSFETs by controlling the channel length, suppressing short channel effects and reducing parasitic capacitance and contact resistance, while maintaining device performance.
Implementation Method 1
the back gate comprises first, second and third compensation doping regions... allowing for non-uniform doping profiles and adjustable threshold voltage through bias voltage application
Implementation Method 2
Channel doping is a known approach of tuning the threshold voltage... ions with a high doping concentration in the channel region
Data Source
AI summary
The present application discloses a MOSFET and a method for manufacturing the same, wherein the MOSFET comprises: an SOI wafer, which comprises a semiconductor substrate, a buried insulator layer, and a semiconductor layer, the buried insulator layer being disposed on the semiconductor substrate, and the semiconductor layer being disposed on the buried insulator layer; a gate stack, which is disposed on the semiconductor layer; a source region and a drain region, which are disposed in the semiconductor layer and on opposite sides of the gate stack; and a channel region, which are disposed in the semiconductor layer and sandwiched by the source region and the drain region, wherein the MOSFET further comprises a back gate disposed in the semiconductor substrate, and wherein the back gate comprises first, second and third compensation doping regions, the first compensation doping region is disposed under the source region and the drain region; the second compensation doping region extends in a direction away from the channel region and adjoining the first compensation doping region; and the third compensation doping region is disposed under the channel region and adjoining the first compensation doping region. By changing the doping type of the back gate, the MOSFET can have an adjustable threshold voltage, and can have a reduced parasitic capacitance and a reduced contact resistance in connection with the back gate.