Silicide Source Body Contacts for Closed Cell Lateral MOSFET
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Solution Overview
Problem
Conventional closed cell lateral MOSFET devices face challenges in maintaining ruggedness while minimizing on-resistance, as the use of large butting contacts to connect the source and body increases cell pitch, and periphery body contacts reduce ruggedness, especially under fast voltage transients.
Innovation Solution
The implementation of silicided source and body diffusion regions with minimally sized contacts, where the metal silicide layer provides electrical connection between the source and body regions, allowing for smaller contact sizes and reduced cell pitch without compromising ruggedness, using refractory metals like platinum, titanium, or cobalt to form a conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large butting contacts are used to connect source and body regions, then ruggedness is improved, but cell pitch increases causing on-resistance to worsen
Solution Approach 1:
The patent changes the material parameter of the contact region by forming a highly doped N+ contact region with specific doping concentration (1e19 to 1e21 atoms/cm³), which reduces contact resistance and allows smaller contact dimensions while maintaining electrical performance and ruggedness
Solution Approach 2:
The patent introduces a vertical dimension by forming the N+ contact region that overlaps both the source region and body region in the cross-sectional view, creating a three-dimensional contact structure that reduces the planar cell pitch requirement while maintaining electrical connection
2Length of moving object
If periphery body contacts are used to minimize cell pitch, then on-resistance is improved, but ruggedness deteriorates under fast voltage transients
Solution Approach 1:
The patent performs preliminary doping action by forming the highly doped N+ contact region in advance within the source cell structure, creating a low-resistance path before any transient events occur, which prevents parasitic bipolar turn-on and ensures ruggedness
3Length of moving object
If minimally sized contacts are used with silicided regions, then cell pitch is reduced improving on-resistance, but manufacturing complexity increases
Solution Approach 1:
The patent segments the contact formation process into distinct stages: first forming the N+ contact region through selective doping, then forming the silicide layer separately, which simplifies each individual step while enabling the overall miniaturization and reduced cell pitch
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 approach ensures the ruggedness of the transistor while maintaining a small cell pitch, enabling efficient high-current conduction with reduced on-resistance and increased channel density, thus enhancing the reliability and performance of power MOSFET devices.
Implementation Method 1
the metal silicide layer provides electrical connection between the source and body regions
Implementation Method 2
using refractory metals like platinum, titanium, or cobalt to form a conductive layer
Data Source
AI summary
A closed cell lateral MOSFET device includes minimally sized source/body contacts formed in source cells with silicided source and body diffusion regions formed therein. In this manner, the cell pitch of the cellular transistor array is kept small while the ruggedness of the transistor is ensured. In other embodiments, a closed cell lateral MOSFET device is formed using silicided source and body diffusion regions and self-aligned contacts or borderless contacts as the source/body contacts. The polysilicon gate mesh can be formed using minimum polysilicon-to-polysilicon spacing to minimize the cell pitch of the cellular transistor array.