Transistor structures with reduced source/drain leakage through backside treatment of subfin semiconductor material
Integrated circuitry comprising transistor structures having a channel portion over a base portion of fin. The base portion of the fin is an insulative amorphous oxide, or a counter-doped crystalline material. Transistor structures, such as channel portions of a fin and source and drain materials may be first formed with epitaxial processes seeded by a front side of a crystalline substrate. Following front side processing, a backside of the transistor structures may be exposed and the base portion of the fin modified from the crystalline substrate composition into the amorphous oxide or counter-doped crystalline material using backside processes and low temperatures that avoid degradation to the channel material while reducing transistor off-state leakage.
1 . An integrated circuit (IC) structure, comprising:
one or more levels of metallization on a frontside of a transistor structure, wherein the transistor structure further comprises:
a channel portion of a fin;
a source material and a drain material at opposite ends of channel portion, wherein the source and drain materials are crystalline; and
a gate stack adjacent to the channel portion; and
a base portion of the fin on a backside of the transistor structure, wherein:
the gate stack is between, and in direct contact with, a center length of the base portion and the channel portion of the fin;
a first end length of the base portion is in direct contact with the source material;
a second end length of the base portion is in direct contact with the drain material; and
the base portion is an amorphous material comprising oxygen, and Si or Ge and a metal impurity associated with a catalytic oxidation of the Si or Ge within the base portion; and
an isolation dielectric adjacent to a sidewall of the base portion.
2 . The IC structure of claim 1 , wherein the metal impurity is Al.
3 . The IC structure of claim 1 , wherein:
the source material and the drain material comprise Si and Ge;
the base portion comprises Si and is substantially free of Ge; and
the channel portion is under compressive strain associated with lattice mismatch between a lattice constant of monocrystalline Si and a lattice constant associated with the source and drain material.
4 . The IC structure of claim 1 , wherein the isolation dielectric has a composition distinct from that of the base portion of the fin.
5 . An integrated circuit (IC) structure, comprising:
one or more levels of metallization on a frontside of a transistor structure, wherein the transistor structure further comprises:
a channel portion of a fin;
a source material and a drain material at opposite ends of channel portion, wherein the source and drain materials are crystalline, and comprise Si, and a donor impurity; and
a gate stack adjacent to the channel portion; and
a base portion of the fin on a backside of the transistor structure, wherein:
the gate stack is between, and in direct contact with, a center length of the base portion and the channel portion of the fin;
a first end length of the base portion is in direct contact with the source material;
a second end length of the base portion is in direct contact with the drain material; and
the base portion comprises oxygen, Al, and Si or Ge; and
a dielectric material adjacent to a sidewall of the base portion.
6 . A computer system, comprising:
a power supply; and
an IC die coupled to the power supply, wherein the IC die comprises the IC structure of claim 1 .