Diode biased ESD protection device and method
An ESD protection device includes an MOS transistor with a source region, drain region and gate region. A node designated for ESD protection is electrically coupled to the drain. A diode is coupled between the gate and source, wherein the diode would be reverse biased if the MOS transistor were in the active operating region.
1. An electrostatic discharge (ESD) protection device comprising:
an MOS transistor comprising a gate, a drain and a source disposed in a first semiconductor region;
a node designated for ESD protection electrically connected to the drain; and
a diode coupled between the gate and the source, the diode comprising a second semiconductor region disposed within the first semiconductor region, wherein
the second semiconductor region of the diode is directly connected only to the gate of the MOS transistor via a connection, and is isolated from other components in the ESD protection device besides the gate of the MOS transistor, the connection, and the first semiconductor region,
the diode would be reverse biased if the MOS transistor were in an active operating region,
the ESD protection device is configured to be triggered via an internal parasitic drain to gate capacitance of the MOS transistor and without a capacitor external to the MOS transistor, and
the gate of the MOS transistor is biased only by a reverse diode current of the diode after an ESD event.
2. The ESD protection device of claim 1 , wherein the diode is directly coupled between the gate and source.
3. The ESD protection device of claim 1 , wherein the gate comprises a metal gate.
4. The ESD protection device of claim 1 , wherein the diode comprises a bulk diode.
5. The ESD protection device of claim 1 , wherein the diode comprises a p+/n+ diode.
6. The ESD protection device of claim 1 , wherein the source is coupled to a reference potential.
7. The ESD protection device of claim 6 , wherein the reference potential comprises ground potential.
8. The ESD protection device of claim 1 , wherein the node to be protected is coupled to an external connection pad.
9. The ESD protection device of claim 1 , wherein no additional capacitor is placed between the gate and drain of the MOS transistor.
10. A semiconductor device comprising:
a semiconductor body of a first conductivity type;
a doped drain region of a second conductivity type disposed at a surface of the semiconductor body, the second conductivity type opposite to the first conductivity type;
a doped source region of the second conductivity type disposed at the surface of the semiconductor body and laterally spaced from the doped drain region by a region of the first conductivity type;
a gate region, at least a portion of which insulatively overlies the region of the first conductivity type;
a signal pad disposed on the semiconductor body, wherein the signal pad is coupled to the doped drain region; and
a diode comprising a first region and a second region, the first region having the first conductivity type and the second region having the second conductivity type, wherein
an interface between the first region and second region forms a semiconductor junction of the diode, and
the first region is coupled to the doped source region and the second region is directly connected only to the gate region via a connecting region,
the second region is isolated from other components in the ESD protection device besides the gate region, the connecting region, and the first region via the interface,
the doped drain region, the gate region, the doped source region and the diode form an ESD device that is configured to be triggered via an internal parasitic capacitance between the gate region and the doped drain region and without an additional capacitor besides the internal parasitic capacitance, and
the gate region biased only by a reverse diode current of the diode after an ESD event.
11. The semiconductor device of claim 10 , wherein the gate region comprises a metal gate region.
12. The semiconductor device of claim 10 , wherein the gate region is coupled to the source region only via the diode.
13. The semiconductor device of claim 10 , wherein:
the second region comprises a doped region of the second conductivity type disposed over the semiconductor body; and
the first region comprises a portion of the semiconductor body adjacent to the second region.
14. The semiconductor device of claim 10 , wherein:
the second region comprises a doped region of the second conductivity type disposed over the semiconductor body; and
the first region comprises a doped region of the first semiconductor type disposed next to the second region and disposed over the semiconductor body.
15. The semiconductor device of claim 14 , wherein the first and second regions comprise highly doped regions.
16. The semiconductor device of claim 10 , wherein the first conductivity type is p-type and the second conductivity type is n-type.
17. The semiconductor device of claim 10 , wherein the first conductivity type is n-type and the second conductivity type is p-type.