Semiconductor device and method of forming same
In an embodiment, a method of forming a semiconductor device includes: forming a first oxide layer over a semiconductor fin structure; performing a first nitridation process to convert the first oxide layer to an oxynitride layer; depositing a silicon-containing layer over the oxynitride layer; performing a first anneal on the silicon-containing layer, wherein after performing the first anneal, the oxynitride layer has a higher nitrogen atomic concentration at an interface with the semiconductor fin structure than in a bulk region of the oxynitride layer; and forming a dummy gate structure over the silicon-containing layer.
1 . A method of forming a semiconductor device, the method comprising:
forming a first oxide layer over a semiconductor fin structure;
performing a first nitridation process to convert the first oxide layer to an oxynitride layer;
depositing a germanium-containing layer over the oxynitride layer;
performing a first anneal on the germanium-containing layer, wherein after performing the first anneal, the oxynitride layer has a higher nitrogen atomic concentration at an interface with the semiconductor fin structure than in a bulk region of the oxynitride layer; and
forming a dummy gate structure over the germanium-containing layer.
2 . The method of claim 1 , wherein after performing the first anneal the oxynitride layer comprises germanium.
3 . The method of claim 1 , wherein performing the first nitridation process comprises a thermal nitridation performed at temperatures ranging from 700° C. to 1200° C. in an ambient of at least one of NH 3 , NO, N 2 O, or NO 2 .
4 . The method of claim 1 further comprising:
etching the semiconductor fin structure to form a first recess, a sidewall of the first recess exposing a semiconductor layer and a sacrificial layer of the semiconductor fin structure;
etching the sacrificial layer to form a second recess in the sidewall of the first recess; and
performing a second nitridation treatment to form a nitrogen-containing layer in the first recess and in the second recess.
5 . The method of claim 4 further comprising:
forming a dielectric layer over the nitrogen-containing layer in the first recess and in the second recess;
etching the nitrogen-containing layer and the dielectric layer, wherein after the etching the nitrogen-containing layer and the dielectric layer, remaining portions of the dielectric layer form an inner spacer in the second recess; and
epitaxially growing a source/drain region in the first recess.
6 . The method of claim 5 , wherein the source/drain region comprises germanium, and wherein after the epitaxially growing the source/drain region, the nitrogen-containing layer comprises germanium.
7 . The method of claim 6 , wherein the second nitridation treatment comprises a plasma nitridation performed at a temperature of 20° C. to 700° C. using precursors comprising at least one of N 2 , NH 3 , NO, N 2 O, and NO 2 .
8 . A method of forming a semiconductor device, the method comprising:
forming a fin structure over a substrate, the fin structure comprising a fin and nanostructures disposed over the fin, the nanostructures comprising a sacrificial layer disposed over the fin and a semiconductor layer over the sacrificial layer;
etching a first recess in the fin structure to expose a sidewall of the nanostructures;
forming a nitrogen-containing layer over a sidewall of the semiconductor layer, and a sidewall of the sacrificial layer;
forming a dielectric layer over the nitrogen-containing layer;
etching the dielectric layer and the nitrogen-containing layer to expose the sidewall of the semiconductor layer;
forming an epitaxial region in the first recess and directly adjacent to the semiconductor layer; and
performing a first anneal on the epitaxial region, wherein after the performing the first anneal, the dielectric layer comprises germanium.
9 . The method of claim 8 further comprising, prior to forming the nitrogen-containing layer, etching the sacrificial layer to form a second recess in the sidewall of the nanostructures, wherein a portion of the nitrogen-containing layer is formed in the second recess, and wherein a portion of the dielectric layer is formed in the second recess.
10 . The method of claim 8 further comprising:
removing the sacrificial layer to form a third recess interposed between the substrate and the semiconductor layer, wherein the removing the sacrificial layer comprises etching a portion of the nitrogen-containing layer; and
forming a gate electrode in the third recess.
11 . The method of claim 8 further comprising, before etching the first recess:
forming an additional nitrogen-containing layer over the fin structure;
forming a germanium-containing layer over the additional nitrogen-containing layer; and
forming a dummy gate structure over the fin structure.
12 . The method of claim 11 further comprising, after forming the germanium-containing layer and before etching the first recess in the fin, performing a second anneal, wherein after performing the second anneal the additional nitrogen-containing layer comprises germanium.
13 . The method of claim 11 further comprising:
removing the dummy gate structure;
removing the additional nitrogen-containing layer from the fin structure; and
forming a replacement gate.
14 . A method of forming a semiconductor device, the method comprising:
forming a first oxide layer over first sidewalls of a semiconductor fin structure;
performing a first nitridation process to convert the first oxide layer to an oxynitride layer;
depositing a germanium-containing layer over the oxynitride layer;
performing a first anneal on the germanium-containing layer, wherein after performing the first anneal, the oxynitride layer has a higher nitrogen atomic concentration at an interface with the semiconductor fin structure than in a bulk region of the oxynitride layer;
forming a dummy gate structure over the germanium-containing layer;
etching the semiconductor fin structure to form a source/drain recess; and
forming a source/drain region in the source/drain recess.
15 . The method of claim 14 , further comprising, before etching the semiconductor fin structure to form the source/drain recess:
depositing a first gate spacer layer over the oxynitride layer; and
etching the first gate spacer layer and the oxynitride layer to expose an upper surface of the semiconductor fin structure.
16 . The method of claim 14 , further comprising, before forming the source/drain region:
forming a first dielectric layer over second sidewalls of the semiconductor fin structure in the source/drain recess, an exposed surface of the first dielectric layer being a nitride;
forming a second dielectric layer over the first dielectric layer; and
etching the second dielectric layer and the first dielectric layer to expose a portion of the second sidewalls of the semiconductor fin structure.
17 . The method of claim 16 , wherein the first nitridation process comprises a thermal nitridation performed at temperatures ranging from 700° C. to 1200° C.
18 . The method of claim 17 , wherein the thermal nitridation comprises an ambient of at least one of NH 3 , NO, N 2 O, or NO 2 .
19 . The method of claim 16 , wherein forming the second dielectric layer comprises:
forming a second oxide layer; and
performing a second nitridation process on the second oxide layer.
20 . The method of claim 19 , wherein the second nitridation process comprises a plasma nitridation performed at temperatures ranging from room temperature to 700° C.