Process for forming thick oxides on Si or SiC for semiconductor devices

• US 7,754,550 B2
• Filed: 07/06/2004
• Issued: 07/13/2010
• Est. Priority Date: 07/10/2003
• Status: Active Grant

• Current Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Original Assignee: International Rectifier Corporation (Infineon Technologies AG)
• Inventors: Chiola, Davide, He, Zhi
• Primary Examiner(s): MANDALA, MICHELLE
• Application Number:
  US10/885,378
• Publication Number:
  US 20050009255A1
• Time in Patent Office: 2,198 Days
• Field of Search: 438/167, 438/570, 438/576, 438/770, 438/FOR.335, 438/637, 438/638, 257/E21.579, 257/E51.009, 257/E33.051, 257/E27.068, 257/E21.163
• US Class Current: 438/167
• CPC Class Codes: H01L 21/32105 Oxidation of silicon-containing layers
• CPC Class Codes: H01L 29/6606 the devices being controllable only by variation of the electric current supplied or the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched, e.g. two-terminal devices
• CPC Class Codes: H01L 29/8725 of the trench MOS barrier type [TMBS]

Abstract

The gate oxide in the trenches of a trench type Schottky device are formed by oxidizing a layer of polysilicon deposited in trenches of a silicon or silicon carbide substrate. A small amount of the substrate is also oxidized to create a good interface between the substrate and the oxide layer which is formed. The corners of the trench are rounded by the initial formation and removal of a sacrificial oxide layer.

Claims

1. The process for forming a trench type Schottky device comprising the steps of forming spaced trenches into the surface of a substrate each trench including sidewalls and a bottom;

growing and then removing a thin layer of oxide in said trench to define rounded corners in the bottom of said trenches;

depositing a layer of polysilicon directly on said sidewalls and said bottom of each trench;

oxidizing said layer of polysilicon using a thermal oxidation process to convert it into a layer of an oxide of a given thickness;

continuing said thermal oxidation process to oxidize a thin more than 100 Å

thick layer of said substrate after the oxidation of said layer of polysilicon improving adherence of said converted layer of oxide;

filling said trenches with a layer of conductive polysilicon which is insulated from said substrate by said layer of oxide, and applying a Schottky contact to the top of said substrate and in contact with the tops of the mesas between said trenches and with said conductive polysilicon in said trenches.

2. The process of claim wherein said substrate is monocrystalline silicon or silicon carbide.

3. A process for manufacturing a semiconductor device comprising:

providing a semiconductor body;

forming a plurality of spaced trenches in said semiconductor body, each trench including sidewalls and a bottom wall;

thermally oxidizing at least said sidewalls of said trenches, and removing said oxidation to define rounded corners in the bottom of said trenches;

growing a layer of convertible material that can be converted to an insulator directly on at least said sidewalls of said trenches;

converting said convertible material to an insulator in a chemical reaction; and

oxidizing a thin more than 100 Å

thick portion of said semiconductor body below said convertible material after said converting of said convertible material to said insulator improving adherence of said insulator.

4. A process according to claim 3, wherein said semiconductor body is comprised of silicon.

5. A process according to claim 3, wherein said semiconductor body is comprised of SiC.

6. A process according to claim 3, further comprising forming a layer of said convertible material over said bottom of said trenches.

7. A process according to claim 3, wherein said convertible material comprises polysilicon.

8. A process according to claim 3, further comprising forming conductive bodies in said trenches.

9. A process according to claim 8, further comprising forming a schottky barrier in electrical contact with said conductive bodies in said trenches and in schottky contact with said semiconductor body.