METHOD OF FORMING A TRENCH MOS GATE ON A POWER SEMICONDUCTOR DEVICE

• US 20010006836A1
• Filed: 05/11/2000
• Published: 07/05/2001
• Est. Priority Date: 02/04/1994
• Status: Active Grant

• Current Assignee: Katsumi Nakamura, Katsuomi Shiozawa, Shuuichi Tominaga, Tadaharu Minato
• Original Assignee: Katsumi Nakamura, Katsuomi Shiozawa, Shuuichi Tominaga, Tadaharu Minato
• Inventors: Nakamura, Katsumi, Minato, Tadaharu, Shiozawa, Katsuomi, Tominaga, Shuuichi
• Granted Patent: US 6,710,401 B2
• Time in Patent Office: Days
• US Class Current: 438/268
• CPC Class Codes: H01L 21/76232 of trenches having a shape other than rectangular or V-shape, e.g. rounded corners, oblique or rounded trench walls H01L21/76229 takes precedence
• CPC Class Codes: H01L 21/76264 SOI together with lateral isolation, e.g. using local oxidation of silicon, or dielectric or polycristalline material refilled trench or air gap isolation regions, e.g. completely isolated semiconductor islands
• CPC Class Codes: H01L 21/76286 Lateral isolation by refilling of trenches with polycristalline material
• CPC Class Codes: H01L 21/763 Polycrystalline semiconductor regions H01L21/76264 takes precedence
• CPC Class Codes: H01L 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/66325 controlled by field-effect, e.g. insulated gate bipolar transistors [IGBT]
• CPC Class Codes: H01L 29/66348 with a recessed gate
• CPC Class Codes: H01L 29/66356 Gated diodes, e.g. field controlled diodes [FCD], static induction thyristors [SITh], field controlled thyristors [FCTh]
• CPC Class Codes: H01L 29/66378 the other device being a controlling field-effect device
• CPC Class Codes: H01L 29/66666 Vertical transistors H01L29/66712, H01L29/66742 take precedence
• CPC Class Codes: H01L 29/66734 with a step of recessing the gate electrode, e.g. to form a trench gate electrode
• CPC Class Codes: H01L 29/7391 Gated diode structures
• CPC Class Codes: H01L 29/7394 on an insulating layer or substrate, e.g. thin film device or device isolated from the bulk substrate H01L29/7398 takes precedence
• CPC Class Codes: H01L 29/7397 and a gate structure lying on a slanted or vertical surface or formed in a groove, e.g. trench gate IGBT
• CPC Class Codes: H01L 29/7455 produced by an insulated gate structure
• CPC Class Codes: H01L 29/78 with field effect produced by an insulated gate H01L29/7725, H01L29/775, H01L29/778 take precedence
• CPC Class Codes: H01L 29/7801 DMOS transistors, i.e. MISFETs with a channel accommodating body or base region adjoining a drain drift region lateral high-voltage MISFETs with channel well and drain offset region H01L29/7835
• CPC Class Codes: H01L 29/7813 : with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/7824 : with a substrate comprising an insulating layer, e.g. SOI-LDMOS transistors
• CPC Class Codes: H01L 29/7827 : Vertical transistors H01L29/7802, H01L29/78642 take precedence

Abstract

There is disclosed a method of fabricating a semiconductor device which includes the steps of forming a trench (4), and repeating the formation and removal of an oxide film (a sacrificial oxide film) twice to provide a rounded configuration (5b) of an opening portion of the trench (4) and a rounded configuration (6b) of a bottom thereof and to draw defects in a semiconductor layer into a silicon oxide film (8), reducing the defects adjacent the inner wall of the trench (4), whereby electric field concentration on a gate is prevented and the mobility of carriers in channels is improved for an improvement in characteristic, particularly an on-state voltage, of a power device.

Claims

1. A method of fabricating a semiconductor device, comprising the steps of:

(a) anisotropically etching a substrate made of semiconductor to form a trench extending in a direction of the thickness of said substrate;

(b) performing a first thermal oxidation to form a first sacrificial oxide film in said trench;

(c) removing said first sacrificial oxide film;

(d) performing a second thermal oxidation to form a second sacrificial oxide film in said trench after said step (c);

(e) removing said second sacrificial oxide film;

(f) forming an insulating film comprising a part of a control electrode in said trench after said step (e); and

(g) filling said trench to form said control electrode opposed to said substrate through said insulating film comprising said part of said control electrode.

2. The method of

claim 1

, wherein

said second thermal oxidation is performed in a water-containing atmosphere, and

said first thermal oxidation is performed at a first temperature higher than a second temperature at which said second thermal oxidation is performed.

3. The method of

claim 2

, wherein

said first temperature is not less than 1000°

C.

4. A method of fabricating a semiconductor device, comprising the steps of:

(a) anisotropically etching a substrate made of semiconductor to form a trench having an aspect ratio of from 2 to 30 and extending in a direction of the thickness of said substrate;

(b) performing a thermal oxidation in an atmosphere of oxygen at a temperature not less than 1000°

C. to form in said trench a sacrificial oxide film having a thickness one-tenth to three-tenths the size of an opening portion of said trench;

(c) removing said sacrificial oxide film;

(d) forming an insulating film comprising a part of a control electrode in said trench after said step (c); and

(e) filling said trench to form said control electrode opposed to said substrate through said insulating film comprising said part of said control electrode.

5. A method of fabricating a semiconductor device, comprising the steps of:

(a) anisotropically etching a substrate made of semiconductor to form a trench extending in a direction of the thickness of said substrate;

(b) performing a thermal oxidation to form a sacrificial oxide film in said trench;

(c) removing said sacrificial oxide film;

(d) oxidizing an inside of said trench at an atmosphere of oxygen at a temperature not less than 1000°

C. to form an insulating film comprising a part of a control electrode after said step (c); and

(e) filling said trench to form said control electrode opposed to said substrate through said insulating film comprising said part of said control electrode.

6. The method of

claim 5

, wherein

said thermal oxidation in said step (b) is performed in an atmosphere of oxygen at a temperature ranging from 950 to 1100°

C.

7. A method of fabricating a semiconductor device, comprising the steps of:

(a) anisotropically etching a substrate made of semiconductor to form a trench extending in a direction of the thickness of said substrate;

(b) providing on said substrate a mask having an edge backing away a predetermined distance from an opening portion of said trench;

(c) performing an isotropic dry etching on said substrate by using said mask;

(d) oxidizing an inside of said trench in an atmosphere of steam at a temperature not more than 1000°

C. after said step (c); and

(e) filling said trench to form a control electrode opposed to said substrate through said insulating film comprising a part of said control electrode.

8. The method of

claim 7

, wherein

said distance is 100 to 400 nm.

9. The method of

claim 7

, wherein

said isotropic dry etching is performed by using an O₂/CF₄ based gas, and a ratio R=O₂/CF₄ of the gas satisfies 1<

R<

5.

10. The method of

claim 7

, further comprising the steps of:

(f) performing a thermal oxidation to form a sacrificial oxide film in said trench; and

(g) removing said sacrificial oxide film,

said steps (f) and (g) being performed after said step (c) and before said step (d).

11. The method of

claim 10

, wherein

said thermal oxidation in said step (f) is performed in an atmosphere of oxygen at a temperature ranging from 950 to 1100°

C.

12. A method of fabricating a semiconductor device, comprising the steps of:

(a) providing a semiconductor layer on a substrate including an insulating film at least on its surface;

(b) anisotropically etching said semiconductor layer to form a trench extending in a direction of the thickness of said semiconductor layer;

(c) performing a thermal oxidation to form a sacrificial oxide film in said trench;

(d) removing a part of said substrate which lies under said trench and said sacrificial oxide film;

(e) oxidizing an inside of said trench in an atmosphere of oxygen at a temperature not less than 1000°

C. to form an isolation oxide film after said step (d); and

(f) filling said trench with a burying material.

13. A method of fabricating a semiconductor device, comprising the steps of:

(a) providing a semiconductor layer on a substrate including an insulating film at least on its surface;

(b) anisotropically etching said semiconductor layer to form a trench extending in a direction of the thickness of said semiconductor layer;

(c) removing a predetermined distance of a part of said insulating film on said substrate which lies under said trench to form a recess having a diameter greater than a diameter of said trench;

(d) performing an isotropic dry etching on said semiconductor layer;

(e) oxidizing an inside of said trench in an atmosphere of steam at a temperature not more than 1000°

C. to form an isolation oxide film after said step (d); and

(f) filling said trench with a burying material.

14. The method of

claim 13

, wherein

an isotropic etching of an oxide film is used in said step (c).

15. The method of

claim 13

, wherein

said predetermined distance is 100 to 400 nm.

16. The method of

claim 13

, wherein

said isotropic dry etching is performed by using an O₂/CF₄ based gas, and a ratio R=O₂/CF₄ of the gas satisfies 1<

R<

5.

17. The method of

claim 13

, further comprising the steps of:

(g) performing a thermal oxidation to form a sacrificial oxide film in said trench; and

(h) removing said sacrificial oxide film,

said steps (g) and (h) being performed after said step (d) and before said step (e).

18. The method of

claim 17

, wherein

said thermal oxidation in said step (g) is performed in an atmosphere of oxygen at a temperature ranging from 950 to 1100°

C.

19. A method of fabricating a semiconductor device, comprising the steps of:

(a) providing a semiconductor layer on a substrate including an insulating film at least on its surface;

(b) anisotropically etching said semiconductor layer to form a trench extending in a direction of the thickness of said semiconductor layer;

(c) performing a thermal oxidation to form a sacrificial oxide film in said trench;

(d) removing a part of said substrate which lies under said trench and said sacrificial oxide film;

(e) forming a polycrystalline semiconductor layer on an inner wall of said trench;

(f) oxidizing said polycrystalline semiconductor layer to form an isolation oxide film; and

(g) filling said trench with a burying material.

20. A method of fabricating a semiconductor device, comprising the steps of:

(a) providing a semiconductor layer on a substrate including a semiconductor oxide film;

(b) anisotropically etching said semiconductor layer to form a trench having an aspect ratio of from 2 to 30 and extending in a direction of the thickness of said semiconductor layer;

(c) performing a thermal oxidation in an atmosphere of oxygen at a temperature not less than 1000°

C. to form in said trench a sacrificial oxide film having a thickness one-tenth to three-tenths the size of an opening portion of said trench;

(d) removing said sacrificial oxide film;

(e) forming an isolation oxide film in said trench after said step (c); and

(f) filling said trench with a burying material.