FET Body Contact Resistance via Segmented Doping
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Solution Overview
Problem
Field Effect Transistors (FETs), particularly those with thin-film silicon on insulator (SOI), face challenges in implementing well contacts with low resistance and high parasitic capacitance, leading to varying device characteristics and threshold voltages, as well as the potential for sneak paths that degrade device performance, especially under high voltage operations.
Innovation Solution
The semiconductor device features a raised source region and a contact region of a different conductivity type, with a silicide metal in contact and metal contacts connecting to these regions, along with an isolation structure between the silicide metal and the raised source region, forming a symmetric FET with an isolated body contact, which allows for accurate control of electric bias and optimized drain region for high voltage tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If body doping is increased to reduce body-contact resistance, then body contact resistance decreases, but device performance degrades due to higher gate voltage requirements
Solution Approach 1:
The segmented body contact structure with lightly-doped and heavily-doped regions allows the device to maintain low threshold voltage (improving ease of operation) while achieving low body contact resistance through the heavily-doped region, thus resolving the contradiction between improving body contact resistance and maintaining device performance.
2Reliability
If body doping is too low beneath the isolation region, then threshold voltage is maintained, but sneak paths form between source and drain
Solution Approach 1:
The invention places a lightly-doped body contact region between the source/drain regions and the heavily-doped body contact region. This lightly-doped region acts as a barrier that prevents sneak paths from forming, while maintaining the low threshold voltage characteristics. The segmentation creates an electrical barrier that blocks parasitic current paths without requiring high doping levels throughout the entire body contact structure.
Data Source
AI summary
A semiconductor structure and method of manufacture and, more particularly, a field effect transistor that has a body contact and method of manufacturing the same is provided. The structure includes a device having a raised source region of a first conductivity type and an active region below the raised source region extending to a body of the device. The active region has a second conductivity type different than the first conductivity type. A contact region is in electric contact with the active region. The method includes forming a raised source region over an active region of a device and forming a contact region of a same conductivity type as the active region, wherein the active region forms a contact body between the contact region and a body of the device.