III-V Trench MOSFET Buried Field Shield via Etch and Regrowth
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Solution Overview
Problem
Existing technologies lack an effective method to form a buried field shield for III-V compound semiconductor trench MOSFETs, which is crucial for protecting the gate dielectric from high electric fields during the blocking off-state.
Innovation Solution
A buried field shield is formed in III-V compound semiconductor trench MOSFETs using an etch and regrowth method, where a p-type region is regrown under the gate trench to create a PN junction with the drift layer, thereby reducing the electric field across the gate dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If selective area ion implantation is used to form a buried field shield, then the dielectric at the trench bottom is protected and a highly doped contact region is formed, but this method is not suitable for III-V compound semiconductors due to limitations in selective area ion implantation
Solution Approach 1:
The patent changes the manufacturing approach from ion implantation to epitaxial regrowth, fundamentally altering the process parameters and mechanisms used to form the buried field shield in III-V compound semiconductors
Solution Approach 2:
The patent replaces the ion implantation process with an epitaxial regrowth process, substituting one manufacturing mechanism with another that is better suited for III-V compound semiconductors
2Reliability
If a buried field shield is added to protect the gate dielectric, then breakdown performance is improved, but the device structure becomes more complex
Solution Approach 1:
The patent combines the buried field shield formation with the existing epitaxial growth process, merging two functions into a single integrated manufacturing step that reduces overall process complexity
Solution Approach 2:
The epitaxial regrowth process serves multiple functions: it forms the body layer, creates the buried field shield, and provides dielectric protection, making the process multi-functional and reducing the need for separate manufacturing steps
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 buried field shield effectively reduces the electric field across the gate dielectric, preventing premature breakdown and enhancing the breakdown performance of III-V compound semiconductor trench MOSFETs.
Implementation Method 1
a buried field shield comprising a III-V compound semiconductor of the second conductivity type that is positioned at least partially below the bottom of the trench and is embedded in the drift layer, thereby forming a PN junction with the drift layer
Data Source
AI summary
The present invention is directed to III-V semiconductor trench MOSFETs comprising a buried field shield. The invention is further directed to an etch and regrowth method for forming this buried field shield. For example, in III-V trench MOSFETs with an n-type substrate, the region can be formed by an etch into the drift (n-type) and regrowth of p-type semiconductor to form the buried field shield in the trench area and a body/channel outside the trench area. With a narrow trench feature size, the regrowth will planarize enabling subsequent source epitaxy (n-type) without requiring ex-situ processing between body/channel and source growths, eliminating the need for additional masking of the regrowth.