Bipolar method and structure having improved BVCEO/RCS trade-off made with depletable collector columns
View Patent ↗In accordance with the invention, there are various methods of making an integrated circuit comprising a bipolar transistor. According to an embodiment of the invention, the bipolar transistor can comprise a substrate, a collector comprising a plurality of alternating doped regions, wherein the plurality of alternating doped regions alternate in a lateral direction from a net first conductivity to a net second conductivity, and a collector contact in electrical contact with the collector. The bipolar transistor can also comprise a heavily doped buried layer below the collector, a base in electrical contact with a base contact, wherein the base is doped to a net second conductivity type and wherein the base spans a portion of the plurality of alternating doped regions, and an emitter disposed within the base, the emitter doped to a net first conductivity, wherein a portion of the alternating doped region under the emitter is doped to a concentration of less than about 3×10 12 cm −2 .
1. A method of forming an integrated circuit comprising a bipolar transistor, the method comprising:
forming a device layer over a substrate;
forming a buried region in the device layer;
forming a first layer doped to a net first conductivity over the device layer;
forming at least one second conductivity type region using a dopant material of a second conductivity type in the first layer, wherein the at least one second conductivity type region is bounded on its sides by at least one region doped to the first conductivity type;
forming a base region in a portion of the first layer; and
forming an emitter in a portion of the base region.
2. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the emitter is formed over one of the at least one second conductivity type regions.
3. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the emitter is formed over one of the at least one first conductivity type regions.
4. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 further comprising:
forming a second buried region in the device layer, wherein the first buried region is doped to a net first conductivity, and wherein the second buried region is doped to a net second conductivity, and further wherein an NPN bipolar transistor is formed using the first buried region and a PNP bipolar transistor is formed using the second buried region.
5. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the region over which the emitter is formed comprises a width substantially the same as a width of the emitter.
6. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the region adjacent the region over which the emitter is formed does not totally deplete under reverse bias of the collector base junction.
7. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the region over which the emitter is formed totally depletes when an absolute value of V CB is less than an absolute value of BV CEO .
8. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the bipolar transistor is an NPN bipolar transistor comprising a BV CEO of at least 69 Volts.
9. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the bipolar transistor is an PNP bipolar transistor comprising a BV CEO of at least 82 Volts.
10. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the bipolar transistor is an NPN bipolar transistor, and wherein the first layer is doped with at least about 2×10 15 atoms/cm 3 .
11. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the bipolar transistor is an NPN bipolar transistor, and wherein the at least one second conductivity type regions formed by diffusing the portion of the dopant material of a second conductivity type from the first epitaxial layer into the first buried region has a length of about 4 μm to about 6 μm, and further wherein the region doped to the first conductivity type has a width of about 7 μm to about 9 μm.
12. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the bipolar transistor is a PNP bipolar transistor, and wherein the at least one second conductivity type region is doped with at least about 4×10 15 atoms/cm 3 .
13. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 , wherein the bipolar transistor is a PNP bipolar transistor, and wherein the at least one region doped to the first conductivity type has a length of about 3 μm to about 5 μm, and further wherein the at least one region doped to the first conductivity type has a width of about 3 μm to about 5 μm.
14. The method of forming an integrated circuit comprising a bipolar transistor according to claim 1 further comprising:
forming a second bipolar transistor, wherein the bipolar transistor has a breakdown voltage greater than the breakdown voltage of the second bipolar transistor.