Eliminating field oxide loss prior to finfet source/drain epitaxial growth

Abstract

Method for forming FinFET source/drain regions with reduced field oxide loss and the resulting devices are disclosed. Embodiments include forming silicon fins separated by a field oxide on a silicon substrate; recessing the field oxide to reveal an upper portion of the silicon fins; forming a spacer layer conformally over the upper portion of the fins and over the field oxide; filling spaces between the fins with a material having high selectivity with the spacer layer; recessing the material; removing the spacer layer above an upper surface of the material; removing the material; recessing the upper portion of the fins; and epitaxially growing source/drain regions on the recessed fins.

What is claimed is: 
     
         1 . A device comprising
 a silicon substrate;   silicon fins on the silicon substrate;   a field oxide between the silicon fins at a lower portion of the silicon fins;   epitaxially grown source/drain regions on the silicon fins; and   a conformal spacer layer having a horizontal portion over the field oxide and vertical portions at opposite edges of each horizontal portion.   
     
     
         2 . The device according to  claim 1 , wherein the field oxide is coplanar with an upper surface of the silicon fins and the source/drain regions are grown between the vertical portions of the spacer layer. 
     
     
         3 . The device according to  claim 2 , wherein the spacer layer comprises silicon nitride (SiN), silicon carbon nitride (SiCN), silicon oxycarbon nitride (SiOCN), or silicon boron carbon nitride (SiBCN). 
     
     
         4 . The device according to  claim 1 , wherein the silicon fins extend to an upper surface of the vertical portions of the spacer layer, and the spacer layer comprises an etch stop layer. 
     
     
         5 . The device according to  claim 4 , wherein the etch stop layer comprises SiCN or hafnium oxide (HfO 2 ). 
     
     
         6 . The device according to  claim 1 , wherein the silicon fins extend to an upper surface of the vertical portions of the spacer layer, and the spacer layer comprises a self-aligned contact (SAC) oxide layer and an etch stop layer over the SAC layer. 
     
     
         7 . The device according to  claim 1 , wherein the vertical portions have a length of 5 nm to 20 nm. 
     
     
         8 . A device comprising:
 a silicon substrate;   recessed silicon fins separated by a field oxide on the silicon substrate;   a spacer layer over an upper portion of the silicon fins and over the field oxide; and   epitaxially grown source/drain regions on the recessed silicon fins.   
     
     
         9 . The device according to  claim 8 , wherein the spacer layer comprises silicon nitride (SiN), silicon carbon nitride (SiCN), silicon oxycarbon nitride (SiOCN), or silicon boron carbon nitride (SiBCN). 
     
     
         10 . The device according to  claim 9 , wherein the spacer layer has a thickness of 8 nm to 15 nm. 
     
     
         11 . The device according to  claim 8 , wherein the spacer layer comprises an etch stop layer. 
     
     
         12 . The device according to  claim 11 , wherein the etch stop layer comprises SiCN or hafnium oxide (HfO 2 ). 
     
     
         13 . The device according to  claim 12 , wherein the etch stop layer has a thickness of 2 nm to 6 nm. 
     
     
         14 . The device according to  claim 8 , wherein the spacer layer comprises a self-aligned contact oxide layer and an etch stop layer. 
     
     
         15 . A device comprising:
 a silicon substrate;   silicon fins on the silicon substrate, such that an upper portion of the silicon fins is exposed and recessed;   a field oxide between the silicon fins at a lower portion of the silicon fins;   a spacer layer of silicon nitride (SiN), silicon carbon nitride (SiCN), silicon oxycarbon nitride (SiOCN), silicon boron carbon nitride (SiBCN), SiCN, or hafnium oxide (HfO 2 ) having a horizontal portion over the field oxide and vertical portions at opposite edges of each horizontal portion; and   epitaxially grown source/drain regions on the recessed silicon fins.   
     
     
         16 . The device according to  claim 15 , wherein the field oxide is coplanar with an upper surface of the silicon fins and the source/drain regions are grown between the vertical portions of the spacer layer. 
     
     
         17 . The device according to  claim 15 , wherein the silicon fins extend to an upper surface of the vertical portions of the spacer layer, and the spacer layer comprises an etch stop layer. 
     
     
         18 . The device according to  claim 17 , wherein the etch stop layer comprises SiCN or hafnium oxide (HfO 2 ). 
     
     
         19 . The device according to  claim 15 , wherein the silicon fins extend to an upper surface of the vertical portions of the spacer layer, and the spacer layer comprises a self-aligned contact (SAC) oxide layer and an etch stop layer over the SAC layer. 
     
     
         20 . The device according to  claim 15 , wherein the vertical portions have a length of 5 nm to 20 nm.