TRENCH SCHOTTKY RECTIFIER DEVICE AND METHOD FOR MANUFACTURING THE SAME

• US 20110084353A1
• Filed: 10/12/2010
• Published: 04/14/2011
• Est. Priority Date: 10/12/2009
• Status: Active Grant

• Current Assignee: PFC Device Holdings Ltd. (PFC Device, Inc.)
• Original Assignee: PFC Device Corp. (PFC Device, Inc.)
• Inventors: Chen, Mei-Ling, Kuo, Hung-Hsin, CHAO, Kou-Liang, Su, Tse-Chuan
• Granted Patent: US 8,618,626 B2
• Time in Patent Office: Days
• US Class Current: 257/484
• CPC Class Codes: H01L 21/2256 through the applied layer
• CPC Class Codes: H01L 21/28537 Deposition of Schottky electrodes
• CPC Class Codes: H01L 29/0623 Buried supplementary region, e.g. buried guard ring multi-RESURF H01L29/0634
• CPC Class Codes: H01L 29/402 Field plates
• CPC Class Codes: H01L 29/66143 Schottky diodes
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

A trench Schottky rectifier device includes a substrate having a first conductivity type, a plurality of trenches formed in the substrate, and an insulating layer formed on sidewalls of the trenches. The trenches are filled with conductive structure. There is an electrode overlying the conductive structure and the substrate, and thus a Schottky contact forms between the electrode and the substrate. A plurality of embedded doped regions having a second conductivity type are formed in the substrate and located under the trenches. Each doped region and the substrate form a PN junction to pinch off current flowing toward the Schottky contact so as to suppress current leakage.

Claims

1. A trench Schottky rectifier device comprising:

a substrate having a first conductivity type;

a plurality of trenches formed in the substrate;

an insulating layer formed on sidewalls of the trenches;

a conductive structure formed in the trenches;

an electrode overlying the conductive structure and the substrate, wherein a Schottky contact forms between the electrode and the substrate; and

a plurality of doped regions having a second conductivity type formed in the substrate and located under the trenches, and in contact with the conductive structure in the trenches,

wherein each of the doped regions and the substrate form a PN junction to pinch off current flowing toward the Schottky contact in a reverse bias mode.

2. The trench Schottky rectifier device according to claim 1, further comprising an isolation layer on an inactive area of the substrate.

3. The trench Schottky rectifier device according to claim 1 wherein the substrate comprises a relatively heavily-doped N-type silicon layer and a relatively lightly-doped N-type epitaxial layer.

4. The trench Schottky rectifier device according to claim 3 wherein the plurality of doped regions comprises P-type dopants.

5. The trench Schottky rectifier device according to claim 1 wherein the electrode is made of aluminum or aluminum alloy, and the trench Schottky rectifier device further comprises an adhesion layer made of titanium or titanium nitride disposed between the electrode and the substrate.

6. The trench Schottky rectifier device according to claim 1 wherein the conductive structure is a polysilicon structure.

7. The trench Schottky rectifier device according to claim 6 wherein the polysilicon structure protrudes from the trenches.

8. The trench Schottky rectifier device according to claim 1 wherein the conductive structure is a metal structure.

9. The trench Schottky rectifier device according to claim 8, further comprising a guard ring having the second conductivity type in an edge area of the substrate.

10. A method for fabricating a trench Schottky rectifier device, comprising steps of:

providing a substrate having a first conductivity type;

forming a plurality of trenched in the substrate;

forming an insulating layer on sidewalls of the trenches;

forming a plurality of doped regions having a second conductivity type under the trenches;

filling the trenches with a conductive structure in contact with the doped regions; and

forming an electrode overlying the conductive structure and the substrate to form a Schottky contact between the electrode and the substrate,

wherein each of the doped regions and the substrate form a PN junction to pinch off current flowing toward the Schottky contact in a reverse bias mode.

11. The method according to claim 10, further comprising a step of forming an isolation layer on an inactive area of the substrate.

12. The method according to claim 11, wherein the isolation layer is an oxide layer formed by a thermal oxidation process.

13. The method according to claim 10 wherein before the step of forming the oxide layer on the sidewalls of the trenches, the method further comprises steps of:

forming a sacrificial layer on the sidewalls of the trenches; and

removing the sacrificial layer to smooth the sidewalls of the trenches.

14. The method according to claim 10 wherein the substrate comprises a relatively heavily-doped N-type silicon layer and a relatively lightly-doped N-type epitaxial layer.

15. The method according to claim 14 wherein the step of forming the plurality of doped regions further comprising a step of doping the substrate with P-type dopants through bottoms of the trenches to form the doped regions under the trenches.

16. The method according to claim 10 wherein the conductive structure is a polysilicon structure and the step of forming the conductive structure comprises steps of:

forming a polysilicon layer covering the substrate by a chemical vapor deposition procedure; and

performing an etch-back procedure to remove a portion of the polysilicon layer out of the trenches.

17. The method according to claim 10 wherein the conductive structure is a tungsten structure and the step of forming the conductive structure comprises steps of:

forming a tungsten layer covering the substrate by a chemical vapor deposition procedure; and

performing an etch-back procedure to remove a portion of the tungsten layer out of the trenches.

18. The method according to claim 10 wherein the step of forming the electrode further comprising steps of:

forming an adhesion layer made of titanium or titanium nitride on the conductive structure and the substrate by a sputtering process;

sintering the adhesion layer;

forming a metal layer made of aluminum or aluminum alloy on the adhesion layer by another sputtering process; and

sintering the metal layer.

19. The method according to claim 10, further comprising a step of forming a guard ring in an edge area of the substrate.

20. The method according to claim 19 wherein the step of forming the guard ring comprising steps of:

forming a depression in the edge area of the substrate;

doping the depression to introduce dopants in to the substrate;

performing a thermal drive-in step or an annealing step to activate the dopants.