High voltage power MOSFET having a voltage sustaining region that includes Doped Columns Formed by trench etching and diffusion from regions of oppositely doped polysilicon

• US 20050042830A1
• Filed: 09/20/2004
• Published: 02/24/2005
• Est. Priority Date: 12/31/2001
• Status: Active Grant

• Current Assignee: Richard A. Blanchard
• Original Assignee: Richard A. Blanchard
• Inventors: Blanchard, Richard A.
• Granted Patent: US 7,224,027 B2
• Time in Patent Office: Days
• US Class Current: 438/268
• CPC Class Codes: H01L 21/2257 the applied layer being silicon or silicide or SIPOS, e.g. polysilicon, porous silicon
• CPC Class Codes: H01L 29/0634 Multiple reduced surface field (multi-RESURF) structures, e.g. double RESURF, charge compensation, cool, superjunction (SJ), 3D-RESURF, composite buffer (CB) structures
• CPC Class Codes: H01L 29/0649 Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• CPC Class Codes: H01L 29/66333 Vertical insulated gate bipolar transistors
• CPC Class Codes: H01L 29/66712 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/7395 Vertical transistors, e.g. vertical IGBT
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors

Abstract

A method is provided for forming a power semiconductor device. The method begins by providing a substrate of a first or second conductivity type and then forming a voltage sustaining region on the substrate. The voltage sustaining region is formed by depositing an epitaxial layer of a first conductivity type on the substrate and forming at least one trench in the epitaxial layer. A first layer of polysilicon having a second dopant of the second conductivity type is deposited in the trench. The second dopant is diffused to form a doped epitaxial region adjacent to the trench and in the epitaxial layer. A second layer of polysilicon having a first dopant of the first conductivity type is subsequently deposited in the trench. The first and second dopants respectively located in the second and first layers of polysilicon are interdiffused to achieve electrical compensation in the first and second layers of polysilicon. Finally, at least one region of the second conductivity type is formed over the voltage sustaining region to define a junction therebetween.

Claims

1. A power semiconductor device comprising:

a substrate of a first or second conductivity type;

a voltage sustaining region disposed on said substrate, said voltage sustaining region including;

an epitaxial layer having a first conductivity type;

at least one trench located in said epitaxial layer;

a first layer of material located in the trench;

a second layer of material located over the first layer of polysilicon;

at least one doped column located adjacent to the trench and in the epitaxial layer, said at least one doped column having a dopant of the second conductivity type, said at least one doped column being formed by diffusion of the second dopant from the first layer of material into the epitaxial layer;

at least one region of said second conductivity disposed over said voltage sustaining region to define a junction therebetween.

2. The device of claim 1 wherein said first and second layers of material are high resistivity layers of material.

3. The device of claim 1 wherein said first and second layers of material are substantially electrically neutral.

4. The device of claim 1 wherein said at least one region further includes:

a gate dielectric and a gate conductor disposed above said gate dielectric;

first and second body regions located in the epitaxial layer to define a drift region therebetween, said body regions having a second conductivity type; and

first and second source regions of the first conductivity type located in the first and second body regions, respectively.

5. The device of claim 4 wherein said body regions include deep body regions.

6. The device of claim 1 wherein the second layer substantially fills the trench.

7. The device of claim 1 wherein said dopant is boron.

8. The device of claim 1 further comprising a first dopant diffused from the second layer to the first layer.

9. The device of claim 3 further comprising another dopant diffused from the second layer to the first layer to achieve the electrical neutrality in the first and second layers of material.

10. The device of claim 9 wherein said another dopant includes arsenic.

11. The device of claim 9 wherein said another dopant includes phosphorus.

12. The device of claim 9 wherein said another dopant includes phosphorus and arsenic.

13. The device of claim 1 wherein said power semiconductor device is selected from the group consisting of a vertical DMOS, V-groove DMOS, and a trench DMOS MOSFET, an IGBT, a diode and a bipolar transistor.

14. The device of claim 1 wherein said first and second layers of material are layers of polysilicon.

15. The device of claim 2 wherein said first and second layers of material are layers of polysilicon.

16. The device of claim 3 wherein said first and second layers of material are layers of polysilicon.

17. The device of claim 4 wherein said first and second layers of material are layers of polysilicon.

18. The device of claim 9 wherein said first and second layers of material are layers of polysilicon.