Symmetrical high frequency SCR structure
View Patent ↗In one embodiment, an SCR device ( 41 ) includes a p+ wafer ( 417 ), a p− layer ( 416 ), an n+ buried layer ( 413 ) and an n− layer ( 414 ). P− wells ( 411,421 ) are formed in the n− layer ( 414 ). N+ regions ( 412,422 ) and p+ regions ( 415,425 ) are formed in the p− wells ( 411,421 ). A first ohmic contact ( 431 ) couples one n+ regions ( 422 ) to one p+ region ( 425 ). A second ohmic contact ( 433 ) couples another n+ region ( 412 ) to another p+ region ( 415 ) to provide physically and electrically symmetrical low-voltage p-n-p-n silicon controlled rectifiers. A deep isolation trench ( 419 ) surrounding the SCR device ( 41 ) and dopant concentration profiles provide a low capacitance SCR design for protecting high frequency integrated circuits from electrostatic discharges.
1. A high frequency integrated circuit structure comprising:
a body of semiconductor material having a plurality of isolated active regions, and comprising a first conductivity type;
internal circuitry formed in a first active region;
a second active region comprising a buried layer of a second conductivity type formed over the body of semiconductor material and a first semiconductor layer of the second conductivity type formed over the buried layer, wherein the first semiconductor layer has a lower dopant concentration than the buried layer;
a first silicon controlled rectifier device formed in the second active region, the first silicon controlled rectifier device comprising a first well region of the first conductivity type formed in the first semiconductor layer, a first doped region of the first conductivity type formed in the first well region, the buried layer, a second well region of the first conductivity type formed in the first semiconductor layer and spaced apart from the first well region, and a second doped region of the second conductivity type formed in the second well region; and
a second silicon controlled rectifier device comprising the second well region, a third doped region of the first conductivity type formed in the second well region, the buried layer, the first well region, and a fourth doped region of the second conductivity type formed in the first well region, wherein the first and second silicon controlled rectifier devices are coupled to the internal circuitry and form an ESD structure for protecting the internal circuitry against positive and negative ESD stresses.
2. The high frequency integrated circuit structure of claim 1 wherein the body of semiconductor material comprises:
a semiconductor wafer having the first conductivity type; and
a second semiconductor layer formed over the semiconductor wafer, wherein the second semiconductor layer comprises the first conductivity type, and wherein the second semiconductor layer has a lower dopant concentration than the semiconductor wafer, and wherein the buried layer is formed adjacent the second semiconductor layer.
3. The high frequency integrated circuit device of claim 2 further comprising:
a first ohmic contact coupling the first and fourth doped regions; and
a second ohmic contact coupling the second and third doped regions.
4. The high frequency integrated circuit device of claim 2 further comprising a deep contact trench extending from a surface of the first semiconductor layer into the semiconductor wafer.
5. The high frequency integrated circuit device of claim 1 further comprising a field dielectric region formed on a surface of the first semiconductor layer between the first and second wells.
6. The high frequency integrated circuit structure of claim 2 , wherein the second semiconductor layer has a dopant concentration of approximately 1.0×10 13 atoms/cm 3 .
7. The high frequency integrated circuit structure of claim 2 , wherein the second semiconductor layer has a thickness from about 1.5 microns to about 3.0 microns.
8. The high frequency integrated circuit structure of claim 1 further comprising a deep isolation trench formed in the body of semiconductor material for isolating the ESD structure from the internal circuitry, wherein the deep isolation trench includes a dielectric layer.