Structure and method for hyper-abrupt junction varactors
AssigneeInternational Business Machines Corporation
InventorsDouglas D. Coolbaugh, Stephen S. Furkay, Jeffrey B. Johnson, Robert M. Rassel, David C. Sheridan
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Abstract
A method and device providing a HA junction varactor which may be fabricated with a reduced variation in C-V tuning curve from one varactor to the next. The process produces a varactor with an active region formed substantially by doping an Si substrate with various dopants at various energy levels. Accordingly, unit-to-unit device variation is reduced because etching, growing, and deposition processes to make the active portion of the varactor are reduced or eliminated. The resulting HA junction has a more uniform thickness, and a more uniform doping profile.
Claims13
A method of fabricating a varactor, comprising:
- providing a semiconductor substrate;
- doping a lower region of the semiconductor substrate with a first dopant at a first energy level;
- doping a middle region of the semiconductor substrate with a second dopant at a second energy level lower than the first energy level, so as to form a hyper-abrupt junction in the middle region;
- and
- doping an upper region of the semiconductor substrate with a third dopant at a third energy level lower than the second energy level, so as to form an anode in the upper region,
- wherein the lower region includes a collector region and a cathode of the varactor, and the cathode is extended to a top surface of the semiconductor substrate through a reach-through implant region.
A method of fabricating a varaptor, comprising:
- doping a lower region of a substrate layer with a first dopant having a dopant profile such that atoms having a first energy (“A”) penetrate to a first depth (“A′”) in the substrate layer forming a cathode and atoms having a second energy (“B”) penetrate to a second depth (“B′”) in the substrate layer forming a collector region above the cathode, wherein A>B and A′>B′;
- doping a middle region of the substrate layer with a second dopant, so as to form a hyper-abrupt junction in the middle region, the middle region being tailored for an implant profile that forms an anode, the second dopant overlapping the collector region;
- and
- doping an upper region of the substrate layer with a source/drain type implant to form the anode,
- wherein the doping of the middle region has approximately less energy than the doping of the lower region and the doping of the upper region has approximately less energy than the doping of the middle region;
- and
- wherein the cathode is extended to a top surface of the semiconductor substrate through a reach-through implant region.
A method of fabricating a varactor, comprising:
- forming a semiconductor substrate;
- doping a lower region of the semiconductor substrate with a first dopant at a first energy level;
- doping a middle region of the semiconductor substrate with a second dopant at a second energy level lower than the first energy level, so as to form a hyper-abrupt junction in the middle region;
- and
- doping an upper region of the semiconductor substrate with a third dopant at a third energy level lower than the second energy level, so as to form an anode,
- wherein the lower region includes a collector region and a cathode that are formed in a single doping step via energy distribution of a single dopant type;
- and
- wherein the cathode is extended to a top surface of the semiconductor substrate through a reach-through implant region.
Dependencies are inferred from the claim text.