Fabrication of a shallow trench isolation by plasma oxidation

Claim 1

A method of fabricating an STI, the method comprising: providing a silicon substrate; for lifting a patterned hardmask on the silicon substrate, wherein the patterned hard mask is a laminated layer comprising a pad oxide and a silicon nitride layer, and exposes a portion of the surface of the silicon substrate; etching the exposed surface of the silicon substrate not covered by the hardmask to form a trench in the silicon substrate; wet etching a portion of the pad oxide layer around the STI edge to expose a portion of the top surface of the silicon substrate located beneath the silicon nitride layer surrounding the periphery of the trench; synchronously oxidizing both the interior surface of the trench and the exposed portion of the top surface of the silicon substrate surrounding the periphery of the trench by a high-density oxygen plasma oxidation process at both a low temperature and a low pressure, to form a liner oxide layer having a first thickness on the interior surface of the trench and a thicker oxide layer having a second thickness, greater than the first thickness, on the STI edge; and filling in the trench by a dielectric layer; wherein an electrical field is applied to the oxygen plasma so that ions created by the plasma has a low ion bombardment energy; wherein the high-density oxygen plasma oxidation process is independent of the surface orientation of silicon.

Claim 2

A method of fabricating an STI, the method comprising: providing a silicon substrate; for lifting a patterned hardmask on the silicon substrate, wherein the patterned hard mask is a laminated layer comprising a pad oxide and a silicon nitride layer, and exposes a portion of the surface of the silicon substrate; etching the exposed surface of the silicon substrate not covered by the hardmask to form a trench in the silicon substrate; wet etching a portion of the pad oxide layer around the STI edge to expose a portion of the top surface of the silicon substrate located beneath the silicon nitride layer surrounding the periphery of the trench; synchronously oxidizing both the interior surface of the trench and the exposed portion of the top surface of the silicon substrate surrounding the periphery of the trench by a high-density oxygen plasma oxidation process at both a low temperature and a low pressure, to form a liner oxide layer having a first thickness on the interior surface of the trench and a thicker oxide layer having a second thickness, greater than the first thickness, on the STI edge; and filling in the trench by a dielectric layer; wherein an electrical field is applied to the oxygen plasma so that ions created by the plasma has a low ion bombardment energy; wherein the high-density oxygen plasma oxidation process is independent of the surface orientation of silicon.

Claim 10

A method of fabricating an STI, the method comprising: providing a silicon substrate; sequentially forming a pad oxide layer and a stop layer on the silicon substrate; performing a lithography and an etching process to define and pattern a trench pattern in the pad oxide layer and the stop layer; performing an RIE process to etch the silicon substrate not covered by the pad oxide layer and the stop layer to form a trench in the silicon substrate, the trench having two <111> oriented silicon sidewalls and one <100> oriented bottom; wet etching a portion of the pad oxide layer around the STI edge to expose a portion of the top surface of the silicon substrate located beneath the silicon nitride layer surrounding the periphery of the trench; synchronously oxidizing both the two <111> oriented silicon sidewalls and the <100> oriented bottom of the trench and the exposed portion of the top surface of the silicon substrate surrounding the periphery of the trench using a high-density Kr/O 2 plasma oxidation process, at both a low temperature and a low pressure to form a liner oxide layer having a first thickness on both the <111> oriented silicon sidewalls and the <100> oriented bottom of the trench, and a thicker oxide layer having a second thickness, greater than the first thickness, on the STI edge; and filling in the trench with a dielectric layer; wherein the oxidation rates on both the <111> oriented silicon sidewalls and the <100> oriented bottom of the trench are the same during the high-density Kr/O 2 plasma oxidation process, while the oxidation rate at the STI edge is greater than the oxidation rate on the interior surface of the trench.

Claim 11

A method of fabricating an STI, the method comprising: providing a silicon substrate; sequentially forming a pad oxide layer and a stop layer on the silicon substrate; performing a lithography and an etching process to define and pattern a trench pattern in the pad oxide layer and the stop layer; performing an RIE process to etch the silicon substrate not covered by the pad oxide layer and the stop layer to form a trench in the silicon substrate, the trench having two <111> oriented silicon sidewalls and one <100> oriented bottom; wet etching a portion of the pad oxide layer around the STI edge to expose a portion of the top surface of the silicon substrate located beneath the silicon nitride layer surrounding the periphery of the trench; synchronously oxidizing both the two <111> oriented silicon sidewalls and the <100> oriented bottom of the trench and the exposed portion of the top surface of the silicon substrate surrounding the periphery of the trench using a high-density Kr/O 2 plasma oxidation process, at both a low temperature and a low pressure to form a liner oxide layer having a first thickness on both the <111> oriented silicon sidewalls and the <100> oriented bottom of the trench, and a thicker oxide layer having a second thickness, greater than the first thickness, on the STI edge; and filling in the trench with a dielectric layer; wherein the oxidation rates on both the <111> oriented silicon sidewalls and the <100> oriented bottom of the trench are the same during the high-density Kr/O 2 plasma oxidation process, while the oxidation rate at the STI edge is greater than the oxidation rate on the interior surface of the trench.