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

• US 20050009255A1
• Filed: 07/06/2004
• Published: 01/13/2005
• 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
• Granted Patent: US 7,754,550 B2
• Time in Patent Office: Days
• US Class Current: 438/173
• 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;

depositing a layer of polysilicon of given thickness into and lining the interior of said trenches;

oxidizing said layer of polysilicon to convert it into a layer of an oxide of a given thickness;

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 1, which includes the further step of oxidizing a thin layer of said substrate during the oxidation of said layer of polysilicon.

3. The process of claim 1, which includes the further step of growing and then removing a thin layer of oxide in said trench before the deposition of said layer of polysilicon to define rounded corners in the bottom of said trenches.

4. The process of claim 2, which includes the further step of growing and removing a thin layer of oxide in said trench before the deposition of said layer of polysilicon to define rounded corners in the bottom of said trenches.

5. The process of claim 1, wherein said substrate is monocrystaline silicon or silicon carbide.

6. The process of claim 2, wherein said substrate is monocrystaline silicon or silicon carbide.

7. The process of claim 3, wherein said substrate is monocrystaline silicon or silicon carbide.

8. The process of claim 4, wherein said substrate is monocrystaline silicon or silicon carbide.

9. A process for the manufacture of a trench type Schottky diode in which oxide layers lining the trenches of said device are formed by oxidizing a polysilicon layer deposited into said trenches.

10. The process of claim 9, wherein said trenches are formed in a substrate of silicon or silicon carbide.

11. The process of claim 9, which includes the further step of growing and removing a thin layer of oxide in said trench before the deposition of said layer of polysilicon to define rounded corners in the bottom of said trenches.

12. The process of claim 10, which includes the further step of growing and removing a thin layer of oxide in said trench before the deposition of said layer of polysilicon to define rounded corners in the bottom of said trenches.

13. 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 bottom wall;

growing a layer of convertible material that can converted to an insulator over at least said sidewalls of said trenches; and

converting said convertible material to an insulator in a chemical reaction.

14. A process according to claim 13, wherein said semiconductor body is comprised of silicon.

15. A process according to claim 13, wherein said semiconductor body is comprised of SiC.

16. A process according to claim 13, further comprising forming a layer of said convertible material over said bottom of said trenches.

17. A process according to claim 13, further comprising thermally oxidizing at least said sidewalls of said trenches, and removing said oxidation prior to forming said layer of said convertible material.

18. A process according to claim 13, wherein said convertible material comprises polysilicon.

19. A process according to claim 13, further comprising oxidizing a portion of said semiconductor body below said convertible material.

20. A process according to claim 13, further comprising forming conductive bodies in said trenches.

21. A process according to claim 20, further comprising forming a schottky barrier in electrical contact with said conductive bodies in said trenches and in schottky contact with semiconductor body.