Epitaxial region for embedded source/drain region having uniform thickness
A semiconductor structure including a source/drain region is disclosed. The source/drain region may include a first epitaxial region along at least one sidewall of the source/drain region having a substantially uniform sidewall thickness. The semiconductor structure may further include a gate structure adjacent and above the source/drain region wherein at least a portion of the first epitaxial region is positioned below a sidewall spacer of the gate structure. A method of forming a source/drain region including a first epitaxial region having a substantially uniform sidewall thickness is disclosed. The method may include forming a trench in a substrate adjacent to a gate structure, forming the first epitaxial region in the trench, forming a spacer material layer on the gate structure and on a portion of the first epitaxial region, and removing a portion of the first epitaxial region using the spacer material layer as a mask.
1. A method of forming an embedded source/drain region in a substrate, the method comprising:
forming a trench in the substrate adjacent to a gate structure positioned thereon, the trench having a first sidewall, a second sidewall opposite the first sidewall, and a bottommost surface extending between the first sidewall and the second sidewall;
forming a first epitaxial region at least partially in the trench;
forming a first spacer layer on the gate structure and on a portion of an uppermost surface of the first epitaxial region adjacent to the gate structure;
removing a first portion of the first epitaxial region using the first spacer layer as a mask by exposing a portion of the substrate at the bottommost surface of the trench, wherein after the removing the first portion of the epitaxial region a thickness of a remaining portion of the epitaxial region has a substantially uniform sidewall thickness; and
forming a second epitaxial region in the trench abutting the remaining portion of the first epitaxial region, and on the portion of the substrate exposed at the bottommost surface of the trench, to form the embedded source/drain region.
2. The method of claim 1 , wherein forming the first epitaxial region includes epitaxially growing a low dopant concentration silicon monophosphide (SiP), and forming the second epitaxial region includes epitaxially growing a high dopant concentration silicon monophosphide (SiP).
3. The method of claim 1 , wherein removing the first portion of the first epitaxial region includes leaving a portion of the first epitaxial region along the bottommost surface of the trench, the portion having a substantially uniform thickness.
4. The method of claim 1 , wherein the substantially uniform sidewall thickness of the remaining epitaxial region is controlled by a thickness of the first spacer layer.
5. The method of claim 1 , wherein a depth of the second epitaxial region within the trench is controlled by an amount of the first portion of the first epitaxial region removed before forming the second epitaxial region.
6. The method of claim 1 , further comprising after forming the second epitaxial region, forming a second spacer layer on the first spacer layer and a portion of an uppermost surface of the second epitaxial region to form a final spacer structure on the gate structure.
7. The method of claim 1 , wherein forming the first epitaxial region includes completely filling the trench.
8. The method of claim 1 , wherein forming the first epitaxial region includes partially filling the trench.
9. A method of forming a source/drain region comprising:
forming a first spacer material layer on a P-type field effect transistor (PFET) region of a substrate and an N-type field effect transistor (NFET) region of the substrate, the NFET region including a gate structure positioned on the substrate;
forming a mask above the first spacer material layer in the PFET region;
forming an opening in the first spacer material layer and the substrate adjacent to the gate structure in the NFET region;
removing the mask;
forming a first epitaxial region in at least a portion of the opening;
forming a second spacer material layer on the first spacer material layer and on a portion of an uppermost surface of the first epitaxial region adjacent to the gate structure;
removing a first portion of the first epitaxial region using the second spacer material layer as a mask, wherein after removing the first portion a remaining portion of the first epitaxial region includes a substantially uniform sidewall thickness; and
forming a second epitaxial region abutting the remaining portion of the first epitaxial region in the opening to form the source/drain region.
10. The method of claim 9 , wherein the first spacer material layer is configured to protect the PFET from physical and electrical damage during the removing the first portion of the first epitaxial region.