Field controlled diode with positively biased gate
An integrated circuit containing a field controlled diode which includes a p-type channel region between an upper gate and a lower n-type depletion gate, a p-type anode in a p-type anode well abutting the channel region, and an n-type cathode in a p-type anode well abutting the channel region opposite from the anode well. An n-type lower gate link connects the lower gate to the surface of the substrate. A surface control element is located at the surface of the channel region between the cathode and the upper gate. A process of forming the integrated circuit containing the field controlled diode is described.
1. An integrated circuit, comprising:
a monolithic p-type semiconductor substrate; and
a first field controlled diode, including:
a p-type channel region located in said substrate;
an n-type lower depletion gate located in said substrate under said channel region;
an n-type lower gate link located in said substrate and contacting a top surface of said bottom depletion gate;
an upper gate located in said substrate over said channel region;
a p-type anode well located in said substrate abutting said channel region and contacting said top surface of said bottom depletion gate;
a p-type anode located in said anode well;
a p-type cathode well located in said substrate abutting said channel region opposite from said anode well and contacting said lower depletion gate;
an n-type cathode located in said cathode well; and
a surface control element at a top surface of said substrate in said channel region between said top gate and said cathode.
2. The integrated circuit of claim 1 , in which said anode is electrically connected to an input/out (I/O) pad of said integrated circuit.
3. The integrated circuit of claim 1 , in which said upper gate includes an upper gate dielectric layer located on said top surface of said substrate and an upper MOS gate located on said upper gate dielectric layer.
4. The integrated circuit of claim 1 , in which said upper gate includes an n-type upper depletion gate.
5. The integrated circuit of claim 1 , in which said surface control element includes a field plate dielectric layer located on said top surface of said substrate and a field plate located on said field plate dielectric layer.
6. The integrated circuit of claim 1 , in which said surface control element includes a silicide block dielectric layer located on said top surface of said substrate.
7. The integrated circuit of claim 1 , in which said surface control element includes an element of field oxide located at said top surface of said substrate.
8. The integrated circuit of claim 1 , in which:
said upper gate is between 0.9 and 1.1 microns long; and
a break-over voltage of said field controlled diode is between 5 and 7 volts.
9. The integrated circuit of claim 1 , further including an n-channel passgate transistor located adjacent to said field controlled diode, in which one of a pair of source/drain regions of said passgate is located in said lower gate link.
10. The integrated circuit of claim 1 , further including a second field controlled diode, in which:
a length of an upper gate in said second field controlled diode is shorter than a length of said upper gate in said first field controlled diode; and
a break-over voltage of said second field controlled diode is at least 2 volts less than a break-over voltage of said first field controlled diode.