Low voltage power MOSFET device and process for its manufacture

US6580123B2 · kind B2 · utility

Assignee

• International Rectifier Corporation · US

Inventor

• Naresh Thapar · San Diego, US

Key dates

• Filing date: Mar 21, 2001
• Grant date: Jun 17, 2003
• Expiry date: Aug 3, 2021

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D64/516

Abstract

A trench type power MOSFET has a thin vertical gate oxide along its side walls and a thickened oxide with a rounded bottom at the bottom of the trench to provide a low RDSON and increased VDSMAX and VGSMAX and a reduced Miller capacitance. The walls of the trench are first lined with nitride to permit the growth of the thick bottom oxide to, for example 1000 å to 1400 å and the nitride is subsequently removed and a thin oxide, for example 320 å is regrown on the side walls. In another embodiment, the trench bottom in amorphized and the trench walls are left as single crystal silicon so that oxide can be grown much faster and thicker on the trench bottom than on the trench walls during an oxide growth step. A reduced channel length of about 0.7 microns is used. The source diffusion is made deeper than the implant damage depth so that the full 0.7 micron channel is along undamaged silicon. A very lightly doped diffusion of 1000 å to 2000 å in depth could also be formed around the bottom of the trench and is depleted at all times by the inherent junction voltage to further reduce Miller capacitance and switching loss.