Semiconductor device with dielectric layer and method of forming the same
A method of forming a semiconductor device includes forming a first layer over a semiconductor fin and forming a second layer over the first layer. The first layer is a first material and the second layer is a second material different from the first layer. The second layer is thicker on a top of the semiconductor fin than along a sidewall of the semiconductor fin. The method further includes performing an oxidation process, the oxidation process oxidizing at least a portion of the second layer, and patterning the second layer and the first layer.
1 . A method of forming a semiconductor device, the method comprising:
forming a first layer over a semiconductor fin, the first layer being a first material;
forming a second layer over the first layer, the second layer being thicker on a first portion of the first layer that is on a top surface of the semiconductor fin than a second portion of the first layer that is along a sidewall of the semiconductor fin, the second layer being a second material;
performing an oxidation process applied to an exposed top surface of the second layer that is on the first portion of the first layer, and exposed sidewall surfaces of the second layer that are on the second portion of the first layer, the oxidation process fully oxidizing the second layer, wherein before the oxidation process, the second material of the second layer comprises carbon or nitrogen, and wherein the oxidation process removes carbon or nitrogen atoms from the second material of the second layer;
forming a dummy gate layer over the second layer; and
patterning the dummy gate layer, the second layer, and the first layer, wherein patterning the dummy gate layer, the second layer, and the first layer exposes the top surface of the semiconductor fin.
2 . The method of claim 1 , wherein the first material comprises silicon oxide.
3 . The method of claim 1 , wherein the second layer is formed with physical vapor deposition using a target, the target comprising silicon.
4 . The method of claim 1 , wherein the oxidation process converts the second material to silicon oxide.
5 . The method of claim 1 , wherein the first layer has a thickness in a range of 15 Å to 40 Å.
6 . The method of claim 1 , wherein the second layer has a thickness measured on top surfaces of the first layer over the semiconductor fin in a range of 5 Å to 25 Å.
7 . The method of claim 1 , wherein the first layer and the second layer have a first combined thickness measured between the top surface of the semiconductor fin and the exposed top surface of the second layer, the first and the second layer have a second combined thickness measured on the sidewall of the semiconductor fin, and a ratio of the first combined thickness to the second combined thickness is in a range of 2:1 to 5:1.
8 . A method of forming a semiconductor device, the method comprising:
forming a dummy dielectric layer over a first fin and a second fin, wherein the first fin is in a first region of a die and the second fin is in a second region of the die, wherein forming the dummy dielectric layer comprises:
forming a first layer over the first fin and the second fin;
depositing a second layer over the first layer, wherein the second layer covers a first top surface of the first layer over the first fin and the second layer covers a second top surface of the first layer over the second fin, a thickness of the second layer tapering along sidewalls of the first layer that are on first sidewalls of the first fin and second sidewalls of the second fin; and
applying an oxidation process to first exposed surfaces of the second layer that are over the first top surface and the second top surface of the first layer, and second exposed surfaces of the second layer that are on the sidewalls of the first layer, wherein before oxidizing the second layer, the second layer is silicon carbide, silicon nitride, or silicon carbonitride, and wherein the oxidizing process oxidizes the second layer and removes carbon or nitrogen atoms from the second layer;
removing a first portion of the dummy dielectric layer over the first fin, wherein a second portion of the dummy dielectric layer remains on the second fin; and
forming a first gate electrode over the first fin and forming a second gate electrode over the second portion of the dummy dielectric layer, wherein a region between the first gate electrode and the first fin is free of the dummy dielectric layer.
9 . The method of claim 8 , wherein the first layer is silicon dioxide.
10 . The method of claim 8 , wherein after oxidizing the second layer, the second layer is silicon dioxide.
11 . The method of claim 8 , wherein the dummy dielectric layer has a first thickness measured between the first top surface of the first fin and a top surface of the second layer in a range of 40 Å to 80 Å.
12 . The method of claim 11 , wherein the dummy dielectric layer has a second thickness measured on the sidewalls of the first fin in a range of 20 Å to 60 Å.
13 . The method of claim 12 , wherein a ratio of the first thickness to the second thickness is in a range of 2:1 to 5:1.
14 . The method of claim 8 , further comprising forming a gate dielectric layer over the first fin and over the second portion of the dummy dielectric layer.
15 . The method of claim 14 , wherein the gate dielectric layer has a third thickness measured between a top surface of the first fin and a top surface of the gate dielectric layer and, wherein the gate dielectric layer and the second portion of the dummy dielectric layer have a fourth thickness measured between a top surface of the second fin and the top surface of the gate dielectric layer, and wherein the fourth thickness is greater than the third thickness.
16 . A method of forming a semiconductor device, the method comprising:
forming a first layer over a semiconductor fin, the first layer being a first material;
forming a second layer of a second material over the first layer, the second layer being formed by a physical vapor deposition process, wherein the second layer is thicker on a first portion of the first layer that is on a top surface of the semiconductor fin than a second portion of the first layer that is along a sidewall of the semiconductor fin;
converting at least a portion of the second material of the second layer to an oxide with an oxidation process, the oxidation process being directly applied to a first top surface of the second layer that is on the first portion of the first layer, and a second sidewall surface of the second layer that is on the second portion of the first layer, wherein in a cross-sectional view, an entirety of the first top surface and an entirety of the second sidewall surface is exposed during the oxidation process, wherein the second material of the second layer is a dielectric material comprising carbon or nitrogen prior to the oxidation process, and wherein the oxidation process fully coverts the second material of the second layer to the oxide;
forming a dummy gate layer over the second layer; and
patterning the dummy gate layer, the second layer, and the first layer, wherein patterning the dummy gate layer, the second layer, and the first layer exposes the top surface of the semiconductor fin.
17 . The method of claim 16 , wherein the oxidation process comprises O 2 gas, ozone, oxygen plasma or a combination thereof.
18 . The method of claim 16 , wherein the oxidation process comprises plasma oxidation at a temperature ranging from 400° C. to 500° C.
19 . The method of claim 16 , wherein the oxidation process removes carbon or nitrogen from the second material of the second layer.