Annular SCR device

Details Annular SCR device Annular SCR device

2000-02-11

2002-06-25

Jackson, Jr., Jerome (Department: 2815)

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

C257S162000

Reexamination Certificate

active

06410965

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an integrated circuit anti-electrostatic discharge technique, and more particularly to a Lateral Semiconductor Controlled Rectifier with annular structure. This annular structure has a smaller layout size and provides better protection against electrostatic discharge.
2. Description of the Related Art
Due to the improvement of semiconductor technology, the size of CMOS devices (or components) have decreased to the level of sub-micrometer, and even half-micrometer. Following this trend, the semiconductor devices generally comprise thinner gate oxide layers, smaller transistor channels, sources and the drains with shallower junctions, lightly doped drain (LDD) structures, and are fabricated via the silicided diffusion process. The smaller structures and the use of the silicided diffusion process decrease the robustness of the integrated circuit against the electrostatic discharge (ESD).
The prior art uses the Lateral Semiconductor Controlled Rectifier (LSCR) as an ESD protection circuit to protect the sub-micrometer CMOS integrated circuit from being damaged by ESD. Such an example is disclosed in the U.S. Pat. No. 5,012,317. The top view and the cross-sectional view of a conventional LSCR formed in a P-type semiconductor
10
are shown in FIG.
1
and FIG.
2
.
FIG.
1
and
FIG. 2
display an N-type well
11
formed on a P-type semiconductor substrate
10
, a P-type doping region
12
formed in the N-type well
11
, and an N-type doping region
13
formed in the P-type semiconductor substrate
10
. The P-type doping region
12
, the N-type well
11
, the P-type semiconductor substrate
10
, and the N-type doping region
13
constitute an LSCR, and serve respectively as the anode, the anode gate, the cathode gate, and the cathode of the LSCR.
Furthermore, the N-type doping region
14
and the P-type doping region
15
are formed in the N-type well
11
and the P-type semiconductor substrate
10
respectively, and serve as the ohmic contact regions of the N-type well
11
and the P-type semiconductor substrate
10
. Usually, the anode doping region
12
and the contact region
14
are connected to a pad of an integrated circuit, and the cathode doping region
13
and the contact region
15
are coupled to the V
SS
power source.
Briefly, the conventional structure of the LSCR has been designed with the layout of strip patterns, as shown in FIG.
2
. The anode doping region
12
, the cathode doping region
13
, the contact region
14
, and the contact region
15
have strip structures, and are disposed in parallel and set apart from each other. However, due to the trend of reducing the size of the integrated circuit, it is necessary to decrease the size of the LSCR structure. Therefore, it is an important issue in ESD protection circuit design to reduce the size of the LSCR structure while maintaining the protection of the integrated circuit from ESD.
SUMMARY OF THE INVENTION
The present invent provides an SCR device with a polygon structure, thereby economizing the size of the layout and the cost, and maintaining the protection of the integrated circuit from electrostatic discharge.
In order to achieve the above object, the present invention provides a SCR device. The SCR device has at least one annular unit formed on a first conductive type semiconductor substrate. The annular cell comprises a second conductivity type well, a first conductivity type doping region, a second conductivity type contact ring, and a second conductivity type doping ring. The second conductivity type well is in the first conductivity type semiconductor substrate, and the first conductivity type doping region is in the second conductivity type well. The second contact ring is in the second conductivity type well, which is surrounding the first conductivity type doping region. The second doping ring is in the first conductivity type semiconductor substrate, which is surrounding the second conductivity type well.
The size of the SCR component can be decreased when the structure formed in an annular shape. Furthermore, the symmetrical structure allows the current through the structure to be increased. The use of the SCR component as the electrostatic discharge protection circuit will therefore increase the protection of the integrated circuit from electrostatic discharge.
Furthermore, the present invent provides a SCR component, which has at least one annular cell formed on a first conductivity type semiconductor substrate and comprising: a second conductivity type floating well, a first conductivity type doping region, and a second conductivity type doping ring. The second conductivity type floating well is formed on the first conductivity type semiconductor substrate, the first conductivity type doping region is formed on the second conductivity type floating well, the second conductivity type doping ring is formed on the first conductivity type semiconductor substrate, which is surrounding the second conductivity type floating well.
Because there is no contact region set on the second type conductivity well, the present invent can decrease the trigger voltage of the SCR component.


REFERENCES:
patent: 5852315 (1998-12-01), Ker
patent: 5986290 (1999-11-01), Apfel
patent: 6097066 (2000-08-01), Lee
patent: 6236087 (2001-05-01), Daly

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