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High Voltage V MOSFET

IP.com Disclosure Number: IPCOM000088661D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Matino, H: AUTHOR

Abstract

This article describes an improved vertical metal oxide semiconductor field-effect transistor (MOSFET) wherein thick oxide regions 5 are formed at the bottom of the gate grooves 10, and base region 3 has a plain junction with n- drain drift region 2. The breakdown voltage of the FET is increased because the base drain junction does not include such curvature, where excessive electric field 5 is imposed, as to result in the breakdown of the FET. Further, the oxide region 5 insures high breakdown voltage as well as low capacitance between the gate electrode and the drain region whereby switching speed of the FET is increased.

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High Voltage V MOSFET

This article describes an improved vertical metal oxide semiconductor field- effect transistor (MOSFET) wherein thick oxide regions 5 are formed at the bottom of the gate grooves 10, and base region 3 has a plain junction with n- drain drift region 2. The breakdown voltage of the FET is increased because the base drain junction does not include such curvature, where excessive electric field 5 is imposed, as to result in the breakdown of the FET. Further, the oxide region 5 insures high breakdown voltage as well as low capacitance between the gate electrode and the drain region whereby switching speed of the FET is increased.

The V-MOSFET is manufactured with a conventional double diffusion technique and an anisotropic etching technique. P type impurity and n type impurity are successively intruded into n- epitaxial layer 2 oriented in the <100> direction to form base region 3 and source region 4. The length of channel 7 can be made less than 1 mu m with this double diffusion technique.

Then the layer 2 is anisotropically etched to form the gate groove 10 whose bottom generally aligns with the bottom of the base region 3. One of the etchants suitable for this purpose is a hot potassium hydroxide solution. The bottom of groove 10 is then oxidized, typically, by anodizing it in 48 % HF, with conventional masking followed by heating in an oxidizing atmosphere. It is preferable that the oxide region 5 reach the N+ drain region 1.

Protective insul...