Forming JFET and LDMOS transistor in monolithic power integrated circuit using deep diffusion regions

Patent metadata

Field	Value
Publication number	US-9460926-B2
Application number	US-201414320434-A
Country	US
Kind code	B2
Filing date	Jun 30, 2014
Priority date	Jun 30, 2014
Publication date	Oct 4, 2016
Grant date	Oct 4, 2016

Abstract

A power integrated circuit includes a junction field effect transistor (JFET) device formed in a first portion of a semiconductor layer with a gate region being formed using a first body region, and a double-diffused metal-oxide-semiconductor (LDMOS) transistor formed in a second portion of the semiconductor layer with a channel being formed in a second body region. The power integrated circuit includes a first deep diffusion region formed under the first body region and in electrical contact with the first body region where the first deep diffusion region together with the firs body region establish a pinch off voltage of the JFET device; and a second deep diffusion region formed under the second body region and in electrical contact with the second body region where the second deep diffusion region forms a reduced surface field (RESURF) structure in the LDMOS transistor.

First claim

What is claimed is:

1. A power integrated circuit, comprising:
a semiconductor layer of a first conductivity type and being lightly doped;
a junction field effect transistor (JFET) device formed in a first portion of the semiconductor layer and being formed in a first deep well of a second conductivity type, the JFET device comprising a gate region formed using a first body region of the first conductivity type, source and drain regions of the second conductivity type formed on opposite sides of the gate region, the first body region, the source and drain regions of the JFET device being formed on a first surface of the semiconductor layer, a channel of the JFET device being formed in an area of the first deep well between the source region and the drain region outside of the gate region;
a double-diffused metal-oxide-semiconductor (LDMOS) transistor formed in a second portion of the semiconductor layer and being formed in a second deep well of the second conductivity type, the LDMOS transistor comprising a second body region of the first conductivity type formed in the second deep well, a gate electrode, a source region, and a drain drift region in electrical contact with a drain region, the source region, the drain drift region and the drain region being of the second conductivity type, the second body region, the source region the drain drift region, and the drain region being formed on the first surface of the semiconductor layer, a channel of the LDMOS transistor being formed in the second body region between the source region and the drain drift region, wherein the second body region is formed to optimize a threshold voltage and a breakdown voltage of the LDMOS transistor and the first and second body regions have the same doping concentration and the same doping depth;
a first deep diffusion region formed in the first deep well under the first body region and in electrical contact with the first body region, the first deep diffusion region together with the first body region establishing a pinch off voltage of the JFET device; and
a second deep diffusion region formed in the second deep well under the second body region and in electrical contact with the second body region, the second deep diffusion region forming a reduced surface field (RESURF) structure in the LDMOS transistor.

2. The power integrated circuit of claim 1 , wherein the LDMOS transistor further comprises:
the gate electrode being formed partially overlapping the body region and insulated from the semiconductor body by a gate dielectric layer;
the source region of the second conductivity type being formed in the second body region on a first side of the gate electrode; and
the drain drift region of the second conductivity type being formed in the second deep well; and
a drain region being formed in the drain drift region, the drain region comprising a first well of the second conductivity type.

3. The power integrated circuit of claim 1 , wherein the semiconductor layer comprises:
a semiconductor substrate of the first conductivity type; and
an epitaxial layer of the first conductivity type formed on the semiconductor substrate.

4. The power integrated circuit of claim 1 , wherein the first and second body regions are formed using the same processing steps including using the same implant dose and the same implant energy, the implant dose and the implant energy being selected to optimize a threshold voltage and a breakdown voltage of the LDMOS transistor.

5. The power integrated circuit of claim 1 , wherein the first and second deep diffusion regions are formed using the same processing steps and have the same doping concentration and depth, the first and second deep diffusion regions being more heavily doped than the first and second body regions.

6. The power integrated circuit of claim 5 , wherein the first and second deep diffusion regions have a graded doping profile, the doping concentration decreasing from a first edge of the first or second deep diffusion region near the respective body region to a second edge away from the respective body region.

7. The power integrated circuit of claim 1 , wherein the first deep diffusion region has a width that is coincidence with the first body region or extends beyond the first body region on both sides of the first body region.

8. The power integrated circuit of claim 7 , wherein the first deep diffusion region is spaced apart from the drain region by a first distance and is spaced apart from the source region by a second distance, the first distance being greater than the second distance.

9. The power integrated circuit of claim 1 , wherein the second deep diffusion region has a width that is coincidence with the second body region or extends beyond the second body region towards the drain drift region or extends under the drain drift region.

10. The power integrated circuit of claim 1 , wherein the first conductivity type is P-type and the second conductivity type is N-type.

11. The power integrated circuit of claim 3 , further comprising:
a first buried layer of the first conductivity type formed in the first portion of the semiconductor layer between the epitaxial layer and the semiconductor substrate; and
a second buried layer of the second conductivity type formed in the second portion of the semiconductor layer between the epitaxial layer and the semiconductor substrate.

12. A method for forming a power integrated circuit, comprising:
providing a semiconductor layer of a first conductivity type and being lightly doped;
forming a first deep well of a second conductivity type in a first portion of the semiconductor layer;
forming a second deep well of the second conductivity type in a second portion of the semiconductor layer;
forming a first body region of the first conductivity type in the first deep well and on a first surface of the semiconductor laver, the first body region being a gate region of a junction field effect transistor (JFET) device;
forming a second body region of the first conductivity type in the second deep well and on the first surface of the semiconductor laver, the second body region forming a channel of a double-diffused metal-oxide-semiconductor (LDMOS) transistor, wherein the second body region is formed to optimize a threshold voltage and a breakdown voltage of the LDMOS transistor and the first and second body regions have the same doping concentration and the same doping depth;
forming a gate electrode, a source region, a drain drift region and a drain region in the second portion of the semiconductor layer, the source region, the drain drift region and the drain region being of the second conductivity type and being formed in the second deep well, a channel of the LDMOS transistor being formed in the second body region between the source region and the drain drift region;
forming a first deep diffusion region in the first deep well under the first body region and in electrical contact with the first body region, the first deep diffusion region together with the first body region establishing a pinch off voltage of the JFET device; and
forming a second deep diffusion region in the second deep well under the second body region and in electrical contact with the second body region, the second deep diffusion region forming a reduced surface field (RESURF) structure in the LDMOS transistor.

13. The method of claim 12 , further comprising:
forming source and drain regions of the second conductivity type on opposite sides of the gate region in the first portion of the semiconductor layer, a channel of the JFET device being formed in an area of the first deep well between the source region and

Assignees

• Alpha & Omega Semiconductor

Inventors

• Mallikarjunaswamy Shekar

Classifications

• H10P30/204

  into Group IV semiconductors · CPC title

• H10P30/21

  of electrically active species · CPC title

• H10D64/516

  the thicknesses being non-uniform · CPC title

• H10D84/151

  LDMOS having built-in components · CPC title

• H10D84/0126

  the components including insulated gates, e.g. IGFETs · CPC title