Claims
- 1. A structure for the protection of functional circuitry from electrostatic discharge at a terminal, comprising:
a pump transistor disposed at a semiconducting surface of a substrate of a first conductivity type, comprising:
a drain region of a second conductivity type, connected to the terminal and disposed within a well region of the second conductivity type at the surface; a gate electrode, overlapping a portion of the well region within which the drain region is disposed, and insulated from a channel region by a gate dielectric, the channel region being of the first conductivity type; and a source region, disposed at the surface adjacent to the channel region; a protection transistor disposed at the surface of the substrate, comprising:
a drain region connected to the drain region of the pump transistor; a source region; and a gate electrode connected to the gate electrode of the pump transistor and insulatively disposed over a channel region of the substrate located between the source region and the drain region; and a guard ring of the first conductivity type surrounding the protection transistor, and connected to the source region of the pump transistor.
- 2. The structure of claim 1, wherein the drain region of the protection transistor is also disposed within a well region of the second conductivity type at the surface.
- 3. The structure of claim 1, wherein each of the source and drain regions of the pump and protection transistors are clad with a metal silicide film.
- 4. The structure of claim 1, further comprising:
a junction capacitor, having a first plate connected to the drain regions of the pump and protection transistors and to the terminal, and having a second plate connected to the gate electrodes of the pump and protection transistors.
- 5. The structure of claim 1, further comprising:
a junction diode, having an anode connected to the terminal and to the drain region of the pump transistor, and having a cathode connected to a power supply node.
- 6. The structure of claim 5, wherein the junction diode comprises:
a diffused anode region of the first conductivity type disposed within a well of the second conductivity type, and connected to the terminal and to the drain region of the pump transistor; a diffused cathode region of the second conductivity type disposed within the well of the second conductivity type, and connected to the power supply node.
- 7. The structure of claim 1, further comprising:
a control circuit, connected to the gates of the pump and protection transistors, and coupled to a power supply node, for biasing the gates of the pump and protection transistors to an off state responsive to the power supply node receiving a power supply voltage.
- 8. The structure of claim 1, wherein the protection transistor is arranged as a plurality of individual protection transistors connected in parallel;
wherein the pump transistor is arranged as a plurality of individual pump transistors connected in parallel; wherein the plurality of individual pump transistors and the plurality of individual protection transistors are arranged in a plurality of blocks; and wherein each of the plurality of blocks is surrounded by a portion of the guard ring.
- 9. The structure of claim 1, wherein the pump transistor has an effective channel length that is shorter than that of the protection transistor.
- 10. A method of conducting current applied to a terminal of an integrated circuit by an electrostatic discharge event, comprising:
conducting the current to a drain of a pump transistor; capacitively coupling the current from the drain of the pump transistor to a gate of the pump transistor, the gate overlapping a portion of a well within which the drain is disposed to define the capacitance, so that the pump transistor is turned on to conduct the current to a source of the pump transistor; conducting the current from the source of the pump transistor to a region of a substrate of the integrated circuit within which a protection transistor is disposed, the protection transistor having a channel region of the same conductivity type as the substrate disposed between drain and source regions; wherein the source, drain, and channel regions of the protection transistor correspond to the emitter, base, and collector of a parasitic bipolar transistor; wherein the drain of the protection transistor is connected to the terminal, the source of the protection transistor is connected to a reference voltage node, and a gate of the protection transistor is connected to the gate of the pump transistor; and wherein the step of conducting the current from the source of the pump transistor forward biases a junction between the channel and source regions of the protection transistor and causes bipolar conduction of current from the terminal to the reference voltage node.
- 11. The method of claim 10, further comprising:
capacitively coupling current from the terminal to the gates of the pump and protection transistors via a junction capacitor.
- 12. The method of claim 10, further comprising:
boosting the current conducted to the region of a substrate of the integrated circuit within which a protection transistor is disposed by conducting current from the terminal to an anode of a junction diode to turn on a parasitic bipolar transistor having an emitter corresponding to the anode of the junction diode, a collector corresponding to the substrate, and a base corresponding to a well within which the cathode of the junction diode is disposed.
- 13. An integrated circuit formed at a semiconducting surface of a substrate of a first conductivity type, comprising:
functional circuitry; a plurality of terminals coupled to the functional circuitry; at least one protection device connected to at least one of the plurality of terminals in parallel with the functional circuitry, and comprising:
a pump transistor disposed at the surface of the substrate, comprising:
a drain region of a second conductivity type, connected to the terminal and disposed within a well region of the second conductivity type at the surface; a gate electrode, overlapping a portion of the well region within which the drain region is disposed, and insulated from a channel region by a gate dielectric, the channel region being of the first conductivity type; and a source region, disposed at the surface adjacent to the channel region; a protection transistor disposed at the surface of the substrate, comprising:
a drain region connected to the drain region of the pump transistor; a source region; and a gate electrode connected to the gate electrode of the pump transistor and insulatively disposed over a channel region of the substrate located between the source region and the drain region; and a guard ring of the first conductivity type surrounding the protection transistor, and connected to the source region of the pump transistor.
- 14. The integrated circuit of claim 13, wherein the drain region of the protection transistor is also disposed within a well region of the second conductivity type at the surface.
- 15. The integrated circuit of claim 13, wherein the at least one protection device comprises:
a junction capacitor, having a first plate connected to the drain regions of the pump and protection transistors and to the terminal, and having a second plate connected to the gate electrodes of the pump and protection transistors.
- 16. The integrated circuit of claim 13, wherein the at least one protection device comprises:
a junction diode, having an anode connected to the terminal and to the drain region of the pump transistor, and having a cathode connected to a power supply node.
- 17. The integrated circuit of claim 16, wherein the junction diode comprises:
a diffused anode region of the first conductivity type disposed within a well of the second conductivity type, and connected to the terminal and to the drain region of the pump transistor; a diffused cathode region of the second conductivity type disposed within the well of the second conductivity type, and connected to the power supply node.
- 18. The integrated circuit of claim 13, wherein the at least one protection device comprises:
a control circuit, connected to the gates of the pump and protection transistors, and coupled to a power supply node, for biasing the gates of the pump and protection transistors to an off state responsive to the power supply node receiving a power supply voltage.
- 19. The integrated circuit of claim 13, wherein the protection transistor is arranged as a plurality of individual protection transistors connected in parallel;
wherein the pump transistor is arranged as a plurality of individual pump transistors connected in parallel; wherein the plurality of individual pump transistors and the plurality of individual protection transistors are arranged in a plurality of blocks; and wherein each of the plurality of blocks is surrounded by a portion of the guard ring.
- 20. The integrated circuit of claim 13, wherein a first one of the plurality of terminals corresponds to a power supply terminal;
and wherein the at least one protection device is connected to the first one of the plurality of terminals.
- 21. The integrated circuit of claim 13, wherein the pump transistor has an effective channel length that is shorter than that of the protection transistor.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority, under 35 U.S.C. §119(e), of Provisional Application No. 60/378,554, filed May 7, 2002.
Divisions (1)
|
Number |
Date |
Country |
Parent |
10163712 |
Jun 2002 |
US |
Child |
10618893 |
Jul 2003 |
US |