ESD protection device with improved bipolar gain using cutout in the body well

Patent metadata

Field	Value
Publication number	US-9754930-B2
Application number	US-201615292409-A
Country	US
Kind code	B2
Filing date	Oct 13, 2016
Priority date	Aug 24, 2012
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

An integrated circuit includes an NMOS SCR in which a p-type body well of the NMOS transistor provides a base layer for a vertical NPN layer stack. The base layer is formed by implanting p-type dopants using an implant mask which has a cutout mask element over the base area, so as to block the p-type dopants from the base area. The base layer is implanted concurrently with p-type body wells under NMOS transistors in logic components in the integrated circuit. Subsequent anneals cause the p-type dopants to diffuse into the base area, forming a base with a lower doping density that adjacent regions of the body well of the NMOS transistor in the NMOS SCR. The NMOS SCR may have a symmetric transistor, a drain extended transistor, or may be a bidirectional NMOS SCR with a symmetric transistor integrated with a drain extended transistor.

First claim

What is claimed is:

1. An integrated circuit, comprising:
a substrate comprising a p-type semiconductor;
a symmetric p-channel metal oxide semiconductor (PMOS) transistor disposed in said substrate;
a p-type n-channel metal oxide semiconductor (NMOS) body well disposed in said substrate;
a symmetric NMOS transistor disposed in said p-type NMOS body well; and
an NMOS silicon controlled rectifier (SCR), including:
a p-type body well disposed in said substrate, said p-type body well having a cutout with a lower doping density;
an n-type source region disposed in said p-type body well over said cutout;
an n-type region disposed in said substrate under said cutout, said n-type region being connected to an n-type drain region; and
a p-type body contact region, disposed in said p-type body well over said cutout;

wherein said NMOS SCR is a drain extended NMOS SCR, and wherein:
said p-type body well is a p-type drain extended body well;
a deep n-type well is disposed in said substrate, extending laterally to abut said p-type drain extended body well, so that said deep n-type well provides an extended drain of said drain extended transistor; and
a p-type SCR contact region is disposed in said deep n-type well.

2. The integrated circuit of claim 1 , in which said n-type region disposed under said cutout is an n-type buried layer; so that said deep n-type well contacts a top of said n-type buried layer.

3. An integrated circuit, comprising:
a substrate comprising a p-type semiconductor;
a symmetric p-channel metal oxide semiconductor (PMOS) transistor disposed in said substrate;
a p-type n-channel metal oxide semiconductor (NMOS) body well disposed in said substrate;
a symmetric NMOS transistor disposed in said p-type NMOS body well; and
an NMOS silicon controlled rectifier (SCR), including:
a p-type body well disposed in said substrate, said p-type body well having a cutout with a lower doping density;
an n-type source region disposed in said p-type body well over said cutout;
an n-type region disposed in said substrate under said cutout, said n-type region being connected to an n-type drain region; and

a p-type body contact region, disposed in said p-type body well over said cutout, in which said NMOS SCR is a symmetric NMOS SCR, wherein:
said p-type body well is an isolated p-type body well;
a deep n-type well is disposed in said substrate, electrically isolating said isolated p-type body well from said substrate; and
a p-type SCR contact region is disposed in said deep n-type well.

Assignees

• Texas Instruments Inc

Inventors

• Edwards Henry Litzmann
• Salman Akram A

Classifications

• H10P30/204

  into Group IV semiconductors · CPC title

• H10P30/22

  using masks · CPC title

• H10P30/21

  of electrically active species · CPC title

• H10W20/435

  Cross-sectional shapes or dispositions of interconnections · CPC title

• H10D84/836

  comprising EDMOS · CPC title