Epitaxial features in semiconductor devices and manufacturing method thereof
A method includes forming a semiconductor fin protruding from a substrate, forming a dummy gate structure across the semiconductor fin, recessing the semiconductor fin in a region adjacent the dummy gate structure to form a recess, growing an epitaxial feature in the recess to fully covers an end of the semiconductor fin that is otherwise exposed in the recess, trimming the epitaxial feature to reduce a width of the epitaxial feature to expose again a portion of the end of the semiconductor fin in the recess, depositing a dielectric layer on the epitaxial feature and in physical contact with the exposed portion of the end of the semiconductor fin, and replacing the dummy gate structure with a metal gate structure.
1 . A method, comprising:
forming a semiconductor fin protruding from a substrate;
depositing an isolation feature on sidewalls of the semiconductor fin;
forming a dummy gate structure across the semiconductor fin;
recessing the semiconductor fin in a region adjacent the dummy gate structure to form a recess, wherein an end of the semiconductor fin under the dummy gate structure is exposed in the recess;
growing an epitaxial feature in the recess and in physical contact with the isolation feature, wherein the epitaxial feature covers the end of the semiconductor fin from being exposed in the recess, wherein after the growing of the epitaxial feature the epitaxial feature includes a first crystalline surface and a second crystalline surface below the first crystalline surface;
trimming the epitaxial feature to reduce a width of the epitaxial feature, such that a portion of the end of the semiconductor fin is exposed again in the recess, wherein a height of the epitaxial feature is larger than the reduced width of the epitaxial feature, wherein the trimming of the epitaxial feature reduces a size of the first crystalline surface and replaces the second crystalline surface with a non-crystalline surface;
depositing a dielectric layer on the epitaxial feature, wherein the dielectric layer is in physical contact with the exposed portion of the end of the semiconductor fin; and
replacing the dummy gate structure with a metal gate structure.
2 . The method of claim 1 , wherein the trimming of the epitaxial feature also reduces the height of the epitaxial feature.
3 . The method of claim 2 , wherein the epitaxial feature with the reduced height is still above a topmost portion of the semiconductor fin.
4 . The method of claim 1 , wherein the portion of the end of the semiconductor fin is a top portion of the semiconductor fin, and wherein after the trimming of the epitaxial feature, a bottom portion of the semiconductor fin remains fully covered by the epitaxial feature.
5 . The method of claim 1 , wherein the growing of the epitaxial feature includes:
growing a first epitaxial layer in the recess; and
growing a second epitaxial layer on the first epitaxial layer, wherein the second epitaxial layer fully covers a top surface of the first epitaxial layer.
6 . The method of claim 5 , wherein the trimming of the epitaxial feature exposes a portion of the top surface of the first epitaxial layer.
7 . The method of claim 1 , further comprising:
forming a spacer layer interposing the epitaxial feature and the dummy gate structure, wherein after the trimming of the epitaxial feature, a portion of the spacer layer is exposed in the recess.
8 . The method of claim 7 , wherein the dielectric layer also covers the exposed portion of the spacer layer.
9 . The method of claim 1 , wherein the trimming of the epitaxial feature recesses a top surface of the epitaxial feature.
10 . A method, comprising:
forming a first fin protruding from a first region of a substrate and a second fin protruding from a second region of the substrate;
forming a dummy gate structure on the first and second fins;
recessing the first and second fins in a source/drain region not covered by the dummy gate structure;
depositing a first mask layer covering the second region;
growing a first buffer epitaxial layer;
growing a first epitaxial layer covering a sidewall of the first fin facing the source/drain region, wherein the first buffer epitaxial layer is directly under the first epitaxial layer;
reshaping the first epitaxial layer to expose a portion of the sidewall of the first fin, wherein the first buffer epitaxial layer is below the exposed portion of the sidewall of the first fin, wherein during the reshaping of the first epitaxial layer, the first buffer epitaxial layer remains intact;
removing the first mask layer;
depositing a second mask layer covering the first region;
growing a second buffer epitaxial layer;
growing a second epitaxial layer covering a sidewall of the second fin facing the source/drain region, wherein the second buffer epitaxial layer is directly under the second epitaxial layer, wherein the first and second epitaxial layers include different material compositions;
reshaping the second epitaxial layer to expose a portion of the sidewall of the second fin, wherein the second buffer epitaxial layer is below the exposed portion of the sidewall of the second fin, wherein during the reshaping of the second epitaxial layer, the second buffer epitaxial layer remains intact;
removing the second mask layer;
depositing a dielectric layer over the first and second epitaxial layers, wherein the dielectric layer covers the exposed portions of the sidewalls of the first and second fins; and
replacing the dummy gate structure with a metal gate structure.
11 . The method of claim 10 , wherein the reshaping of the first epitaxial layer increases an aspect ratio of the first epitaxial layer, and wherein the reshaping of the second epitaxial layer increases an aspect ratio of the second epitaxial layer.
12 . The method of claim 10 , wherein the reshaping of the first epitaxial layer and the reshaping of the second epitaxial layer are performed simultaneously.
13 . The method of claim 10 , wherein the reshaping of the first epitaxial layer partially exposes a top surface of the first buffer epitaxial layer, and wherein the reshaping of the second epitaxial layer exposes a top surface of the second epitaxial layer.
14 . The method of claim 10 , wherein the growing of the first buffer epitaxial layer and the growing of the second buffer epitaxial layer are performed simultaneously.
15 . The method of claim 10 , wherein the reshaping of the first and second epitaxial layers recesses top surfaces of the first and second epitaxial layers.
16 . A method, comprising:
forming a fin-shaped structure protruding from a substrate;
depositing an isolation feature on sidewalls of the fin-shaped structure;
forming a dummy gate structure across the fin-shaped structure;
depositing a gate spacer on a sidewall of the dummy gate structure;
recessing the fin-shaped structure in a region adjacent the gate spacer to form a recess, wherein the recess exposes a sidewall the fin-shaped structure under the gate spacer;
growing a buffer epitaxial layer in the recess;
growing an epitaxial feature in the recess and over the buffer epitaxial layer, the epitaxial feature covering the sidewall of the fin-shaped structure from being exposed;
trimming the epitaxial feature to reduce a width of the epitaxial feature to expose a portion of the sidewall of the fin-shaped structure, wherein a height of the epitaxial feature is larger than the reduced width of the epitaxial feature, wherein during the trimming of the epitaxial feature the buffer epitaxial layer remains intact;
depositing an etch stop layer on the epitaxial feature, wherein the etch stop layer interfaces with the exposed portion of the sidewall of the fin-shaped structure; and
replacing the dummy gate structure with a metal gate structure.
17 . The method of claim 16 , wherein the fin-shaped structure incudes a plurality of channel layers interleaved by a plurality of sacrificial layers, the method further comprising:
laterally recessing the sacrificial layers;
forming inner spacers abutting the sacrificial layers; and
removing the sacrificial layers to release the channel layers,
wherein the metal gate structure wraps around at least one of the channel layers, and wherein the etch stop layer interfaces with at least a topmost one of the inner spacers.
18 . The method of claim 16 , wherein prior to the trimming the epitaxial feature includes a crystalline facet, and wherein the trimming reduces a size of the crystalline facet.
19 . The method of claim 16 , wherein prior to the trimming the epitaxial feature includes a crystalline facet, and wherein the trimming replaces the crystalline facet with a non-crystalline surface.
20 . The method of claim 16 , wherein the fin-shaped structure includes a plurality of channel layers interleaved by a plurality of sacrificial layers, the method further comprising:
removing the sacrificial layers to release the channel layers,
wherein the metal gate structure wraps around at least one of the channel layers, wherein the exposed portion of the sidewall of the fin-shaped structure includes a sidewall of a topmost one of the channel layer, and wherein the etch stop layer interfaces with the exposed sidewall of the topmost one of the channel layers.