Vertical transistor device structure with cylindrically-shaped regions

Patent metadata

Field	Value
Publication number	US-9543396-B2
Application number	US-201414520527-A
Country	US
Kind code	B2
Filing date	Oct 22, 2014
Priority date	Dec 13, 2013
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A vertical power transistor device includes a semiconductor layer of a first conductivity type, with a plurality of cylindrically-shaped dielectric regions disposed in the semiconductor layer. The cylindrically-shaped dielectric regions extend in a vertical direction from a top surface of the semiconductor layer downward. Adjacent ones of the cylindrically-shaped dielectric regions being laterally separated along a common diametrical axis by a narrow region of the semiconductor layer having a first width. Each dielectric region has a cylindrically-shaped, conductive field plate member centrally disposed therein. The cylindrically-shaped, conductive field plate member extends in the vertical direction from the top surface downward to near a bottom of the dielectric region. The dielectric region laterally separates the cylindrically-shaped, conductive field plate member from the narrow region. A source region is disposed at the top surface, and a drain region is disposed at the bottom, of the semiconductor layer.

First claim

We claim:

1. A vertical power transistor device comprising:
a semiconductor layer of a first conductivity type;
a plurality of cylindrically-shaped dielectric regions disposed in the semiconductor layer, each cylindrically-shaped dielectric region having an outer side that extends in a vertical direction from a top surface of the semiconductor layer downward, each cylindrically-shaped dielectric region having a circular cross-section in a horizontal plane perpendicular to the vertical direction, adjacent ones of the cylindrically-shaped dielectric regions being laterally separated along a common diametrical axis by a narrow region of the semiconductor layer having a first width;
each cylindrically-shaped dielectric region having a cylindrical field plate member centrally disposed therein, the cylindrical field plate member having a circular cross-section in the horizontal plane and comprising a conductive material that fully extends laterally across a diameter of the circular cross-section of the cylindrical field plate member, the conductive material extending in the vertical direction from the top surface downward to near a bottom of the cylindrically-shaped dielectric region, the cylindrically-shaped dielectric region laterally separating the cylindrical field plate member from the narrow region;
a source region of the first conductivity type disposed at the top surface of the narrow region;
a body region of a second conductivity type, the body region separating the source from a lower portion of the narrow region, the lower portion comprising a drift region;
a drain region of the first conductivity type disposed beneath the semiconductor layer; and
a ring-shaped gate member disposed in each cylindrically-shaped dielectric region between the narrow region and the cylindrical field plate member.

2. The vertical power transistor device according to claim 1 wherein a lateral width of the cylindrically-shaped dielectric region separates the cylindrical field plate member from the narrow drift region, the lateral width being substantially the same at all points along a side surface of the cylindrical field plate member.

3. The vertical power transistor device according to claim 1 wherein the ring-shaped gate member is a planar gate member.

4. The vertical power transistor device according to claim 1 wherein the cylindrical field plate members each comprise polysilicon.

5. The vertical power transistor device according to claim 1 wherein a cell of the vertical power transistor device comprises a triad of the cylindrically-shaped dielectric regions in an equilateral triangular arrangement.

6. The vertical power transistor device according to claim 1 further comprising a substrate, the semiconductor layer comprising an epitaxial layer disposed on the substrate.

7. The vertical power transistor device according to claim 1 wherein the substrate is the first conductivity type.

8. The vertical power transistor device according to claim 1 wherein the substrate is a second conductivity type.

9. The vertical power transistor device according to claim 1 wherein the first conductivity type comprises n-type.

10. The vertical power transistor device according to claim 1 wherein each of the cylindrically-shaped dielectric regions extends downward into the drain region.

11. The vertical power transistor device according to claim 1 wherein the drift region has a doping concentration that varies from near the body region down to near the bottom of the drift region.

12. The vertical power transistor device according to claim 1 wherein the drift region comprises an epitaxial layer having a graded doping profile.

13. The vertical power transistor device according to claim 11 wherein the doping concentration is highest near the bottom of the drift region.

14. A high-voltage transistor comprising:
a substrate;
an array of cylindrically-shaped dielectric regions disposed in the substrate and arranged in an equilateral triangular layout, each of the cylindrically-shaped dielectric regions having an outer side that extends in a vertical direction from a top surface of the substrate downward, the cylindrically-shaped dielectric regions having a circular cross-section in a horizontal plane perpendicular to the vertical direction, adjacent ones of the cylindrically-shaped dielectric regions being laterally separated along a common diametrical axis by a narrow region of the substrate having a first width;
each cylindrically-shaped dielectric region having a cylindrical field plate member centrally disposed therein, the cylindrical field plate member having a circular cross-section in the horizontal plane and comprising a conductive material that fully extends laterally across a diameter of the circular cross-section of the cylindrical field plate member, the conductive material extending in the vertical direction from the top surface downward to near a bottom of the cylindrically-shaped dielectric region, the cylindrically-shaped dielectric region laterally separating the cylindrical field plate member from the narrow region;
a source disposed at the top surface of the narrow region;
a body region that separates the source from a lower portion of the narrow region, the lower portion comprising a drift region;
a drain disposed at the bottom of the substrate; and
a ring-shaped gate member disposed in each cylindrically-shaped dielectric region between the narrow region and the cylindrical field plate member.

15. The high-voltage transistor according to claim 14 wherein the gate member is a planar gate member.

16. The high-voltage transistor according to claim 14 wherein the cylindrically-shaped dielectric regions each comprises an oxide.

17. The high-voltage transistor according to claim 14 wherein the first width is in a range of approximately 1-2 microns wide.

18. The high-voltage transistor according to claim 14 wherein the narrow region has a doping concentration in a range of about 1×10 15 /cm 3 to about 1×10 17 /cm 3 .

19. The high-voltage transistor according to claim 14 wherein each of the cylindrically-shaped dielectric regions extends downward into the drain.

Assignees

• Power Integrations Inc

Inventors

• Georgescu Sorin Stefan
• Grabowski Wayne Byran
• Varadarajan Kamal Raj
• Zhu Lin
• Yang Kuo-Chang Robert

Classifications

• H10D30/66

  Vertical DMOS [VDMOS] FETs · CPC title

• H01L29/7813

  Electricity · mapped topic

• H01L29/7827

  Electricity · mapped topic

• H01L29/407 Primary

  Electricity · mapped topic

• H01L29/7397

  Electricity · mapped topic