Superjunction structures for power devices and methods of manufacture

• US 9,431,481 B2
• Filed: 09/19/2014
• Issued: 08/30/2016
• Est. Priority Date: 09/19/2008
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Lee, Jaegil
• Primary Examiner(s): Loke, Steven
• Assistant Examiner(s): Cruz, Leslie Pilar
• Application Number:
  US14/491,653
• Publication Number:
  US 20150069567A1
• Time in Patent Office: 711 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 29/045 by their particular orientation of crystalline planes
• CPC Class Codes: H01L 29/0615 by the doping profile or the shape or the arrangement of the PN junction, or with supplementary regions, e.g. junction termination extension [JTE] LDD or drain offset regions H01L29/7833
• CPC Class Codes: H01L 29/0619 with a supplementary region doped oppositely to or in rectifying contact with the semiconductor containing or contacting region, e.g. guard rings with PN or Schottky junction
• 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 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• 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 29/402 Field plates
• CPC Class Codes: H01L 29/404 Multiple field plate structures
• CPC Class Codes: H01L 29/4238 characterised by the surface lay-out
• CPC Class Codes: H01L 29/66712 Vertical DMOS transistors, i.e. VDMOS transistors
• 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 29/7397 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 29/74 Thyristor-type devices, e.g. having four-zone regenerative action two-terminal thyristors H01L29/87
• CPC Class Codes: H01L 29/7811 with an edge termination structure guard regions per se H01L29/0619; field plates per se H01L29/402
• 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 29/872 Schottky diodes

Abstract

In a general aspect, a power device can include an epitaxial layer of a first conductivity type, an active region, a termination region surrounding the active region, a plurality of trenches disposed in the epitaxial layer, and silicon material of a second conductivity type disposed in the plurality of trenches. The silicon material of the second conductivity type and a plurality of mesas defined in the epitaxial layer by the trenches, can define a plurality of concentric octagon-shaped pillars of alternating conductivity type, a first portion of the pillars being disposed in the active region and a second portion of the pillars being disposed in the termination region. Sidewalls of the plurality of trenches can define a first four legs and a second four legs of each of the pillars. The sidewalls can have a same crystallographic plane direction.

Claims

1. A power device comprising:

at least one epitaxial layer of a first conductivity type;

an active region;

a termination region surrounding the active region;

a plurality of trenches disposed in the at least one epitaxial layer; and

silicon material of a second conductivity type disposed in the plurality of trenches, the silicon material of the second conductivity type, together with a plurality of mesas defined in the at least one epitaxial layer by the plurality of trenches, defining a plurality of concentric octagon-shaped pillars of alternating conductivity type, at least a first portion of the concentric octagon-shaped pillars being disposed in the active region and at least a second portion of the concentric octagon-shaped pillars being disposed in the termination region,

sidewalls of the plurality of trenches defining a first four legs and a second four legs of each of the plurality of concentric octagon-shaped pillars, the sidewalls having a same crystallographic plane direction, the first four legs including at least two legs of a first length and the second four legs including at least two legs of a second length, the second length being different than the first length.

2. The power device of claim 1, wherein legs of the plurality of concentric octagon-shaped pillars increase in length in a direction away from a center of the plurality of concentric octagon-shaped pillars.

3. The power device of claim 1, further comprising:

a body region of the second conductivity type disposed in the at least one epitaxial layer;

a source region of the first conductivity type disposed in the body region; and

an insulated gate electrode disposed on at least a portion of the body region and at least a portion of the source region.

4. The power device of claim 1, wherein the same plane direction is a <

(tan 22.5)10>

plane direction.

5. The power device of claim 1, wherein the silicon material of the second conductivity type disposed in the plurality of trenches includes:

a first layer of silicon material of the second conductivity type having a first doping concentration; and

a second layer of silicon material of the second conductivity type disposed on the first layer of silicon material of the second conductivity type, the second layer of silicon material of the second conductivity type having a second doping concentration, the second doping concentration being different than the first doping concentration.

6. The power device of claim 5, wherein the first doping concentration is greater than the second doping concentration.

7. The power device of claim 5, wherein the first doping concentration is less than the second doping concentration.

8. The power device of claim 5, wherein the silicon material of the second conductivity type disposed in the plurality of trenches further includes a third layer of silicon material of the second conductivity type disposed on the second layer of silicon material of the second conductivity type, the third layer of silicon material of the second conductivity type having a third doping concentration, the third doping concentration being different than at least the second doping concentration.

9. The power device of claim 1, wherein at least one mesa of the plurality of mesas is a floating mesa, the floating mesa defining an isolation region between the active region and the termination region.

10. A method of forming a power device having an active region surrounded by a termination region, the method comprising:

forming a plurality of trenches in at least one epitaxial layer of a first conductivity type; and

filling the plurality of trenches with silicon material of a second conductivity type, the silicon material of the second conductivity type, together with a plurality of mesas defined in the at least one epitaxial layer by the plurality of trenches, defining a plurality of concentric octagon-shaped pillars of alternating conductivity type, at least a first portion of the concentric octagon-shaped pillars being disposed in the active region and at least a second portion of the concentric octagon-shaped pillars being disposed in the termination region,

each of the plurality of concentric octagon-shaped pillars having a first four legs of a first length and a second four legs of a second length, the second length being different than the first length, and

sidewalls of trenches defining the first four legs and the second four legs of each of the plurality of concentric octagon-shaped pillars having a same crystallographic plane direction.

11. The method of claim 10, further comprising:

prior to forming the plurality of trenches, rotating, by 22.5 degrees, a wafer in which the power device is formed.

12. The method of claim 10, wherein corner legs of the plurality of concentric octagon-shaped pillars gradually increase in length in a direction away from a center of the plurality of concentric octagon-shaped pillars.

13. The method of claim 10, further comprising:

forming a body region of the second conductivity type in the at least one epitaxial layer;

forming a source region of the first conductivity type in the body region; and

forming an insulated gate electrode on at least a portion of the body region and at least a portion of the source region.

14. The method of claim 10, wherein filling the plurality of trenches with silicon material of the second conductivity type includes:

forming a first epitaxial layer of the second conductivity type having a first doping concentration; and

forming a second epitaxial layer of the second conductivity type on the first epitaxial layer of the second conductivity type, the second epitaxial layer of the second conductivity type having a second doping concentration, the second doping concentration being different than the first doping concentration.

15. The method of claim 14, wherein filling the plurality of trenches with silicon material of the second conductivity type further includes forming a third epitaxial layer of the second conductivity type on the second epitaxial layer of the second conductivity type, the third epitaxial layer of the second conductivity type having a third doping concentration, the third doping concentration being different than at least the second doping concentration.

16. A power device comprising:

an epitaxial layer of a first conductivity type;

an active region disposed in the epitaxial layer of the first conductivity type;

a termination region disposed in the epitaxial layer of the first conductivity type and surrounding the active region;

a plurality of trenches disposed in the epitaxial layer of the first conductivity type; and

an epitaxial layer of a second conductivity type disposed in the plurality of trenches, the epitaxial layer of the second conductivity type, together with a plurality of mesas defined in the epitaxial layer of the first conductivity type by the plurality of trenches, defining a plurality of concentric octagon-shaped pillars of alternating conductivity type, at least a first portion of the concentric octagon-shaped pillars being disposed in the active region and at least a second portion of the concentric octagon-shaped pillars being disposed in the termination region,

each of the plurality of concentric octagon-shaped pillars having a first four legs of a first length and a second four legs of a second length, the second length being different length than the first length, and

sidewalls of trenches defining the first four legs and the second four legs of each of the plurality of concentric octagon-shaped pillars having a (tan 22.5)10>

crystallographic plane direction.

17. The power device of claim 16, wherein the epitaxial layer of the second conductivity type includes:

a first epitaxial layer of the second conductivity type having a first doping concentration; and

a second epitaxial layer of the second conductivity type disposed on the first epitaxial layer of the second conductivity type, the second epitaxial layer of the second conductivity type having a second doping concentration, the second doping concentration being different than the first doping concentration.

18. The power device of claim 17, wherein the epitaxial layer of the second conductivity type further includes a third epitaxial layer of the second conductivity type disposed on the second epitaxial layer of the second conductivity type, the third epitaxial layer of the second conductivity type having a third doping concentration, the third doping concentration being different than at least the second doping concentration.

19. The power device of claim 18, wherein the third doping concentration is substantially equal to the first doping concentration.

20. The power device of claim 17, wherein the first doping concentration is less than the second doping concentration.