Use of contacts to create differential stresses on devices
View Patent ↗Disclosed herein are various methods and structures using contacts to create differential stresses on devices in an integrated circuit (IC) chip. An IC chip is disclosed having a p-type field effect transistor (PFET) and an n-type field effect transistor (NFET), a PFET contact to a source/drain region of the PFET and an NFET contact to a source/drain region of the NFET. In a first embodiment, a silicon germanium (SiGe) layer is included only under the PFET contact, between the PFET contact and the source/drain region of the PFET. In a second embodiment, either the PFET contact extends into the source/drain region of the PFET or the NFET contact extends into the source/drain region of the NFET.
1. A method of creating differential stress in a plurality of contacts in an integrated circuit (IC) chip, the method comprising:
providing a substrate including a p-type field effect transistor (PFET) and an n-type field effect transistor (NFET), the PFET and NFET each including a source/drain region;
forming a silicide layer over the PFET and the NFET;
depositing at least one nitride layer over the substrate;
depositing a dielectric layer over the at least one nitride layer;
etching a PFET contact trench through the dielectric layer down to the at least one nitride layer on the PFET;
etching an NFET contact trench through the dielectric layer down to the at least one nitride layer on the NFET;
opening the at least one nitride layer in the PFET contact trench;
further etching the PFET contact trench through the silicide layer into the source/drain region of the PFET;
depositing a layer of silicon germanium (SiGe) into the PFET contact trench, wherein an upper surface of the SiGe layer is coplanar with an upper surface of the silicide layer;
filling the PFET contact trench to form a PFET contact; and
filling the NFET contact trench to form a NFET contact.
2. The method of claim 1 , wherein the PFET contact trench is etched approximately 50 to approximately 3000 angstroms into the source/drain region of the PFET.
3. The method of claim 1 , wherein the PFET contact imparts a compressive stress on the PFET.