Structure and method for fabricating self-aligned metal contacts
View Patent ↗A semiconductor structure including at least one transistor is provided which has a stressed channel region that is a result of having a stressed layer present atop a gate conductor that includes a stack comprising a bottom polysilicon (polySi) layer and a top metal semiconductor alloy (i.e., metal silicide) layer. The stressed layer is self-aligned to the gate conductor. The inventive structure also has a reduced external parasitic S/D resistance as a result of having a metallic contact located atop source/drain regions that include a surface region comprised of a metal semiconductor alloy. The metallic contact is self-aligned to the gate conductor.
1. A method of forming a semiconductor structure comprising:
providing a patterned material stack comprising a lower layer of polysilicon and an upper layer of polysilicon germanium on a surface of a semiconductor substrate, said patterned material stack having sidewalls that are covered by at least one spacer;
removing said upper layer of polysilicon germanium from said patterned material stack;
forming a first metal semiconductor alloy layer within said polysilicon layer and forming a second metal semiconductor alloy layer within said semiconductor substrate at a footprint of said at least one spacer;
forming an etch stop liner and a stressed layer on said first semiconductor alloy layer, wherein said etch stop liner is present on a bottom surface and sidewall surfaces of said stressed layer; and
forming a metallic contact comprising a metal from Group VIII or IB of the Periodic Table of Elements and at least one of W, B, P, Mo and Re on said second metal semiconductor alloy layer.
2. The method of claim 1 wherein said forming said metallic contact comprises a non-epitaxial raised/source drain approach comprising an electroless deposition of at least one metal from Group VIII or IB of the Periodic Table and at least one of B, P, Mo and Re.
3. The method of claim 1 wherein said forming the etch stop liner and the stressed layer comprises depositing said etch stop liner and said stressed layer over the semiconductor substrate and said first semiconductor alloy layer located within said lower layer of polysilicon, providing a patterned photoresist that has at least one opening that is perpendicular to said lower layer of polysilicon, said at least one opening is located within an active area of said substrate and outside said active area, performing a first etch that removes said stressed layer not protected by said patterned phororesist, and performing a second etch that removes said etch stop liner not protected by said patterned photoresist.
4. The method of claim 1 wherein said forming the etch stop liner and the stressed layer comprises depositing said etch stop liner and said stressed layer over the semiconductor substrate and said first semiconductor alloy layer located within said lower layer of polysilicon, providing a patterned photoresist that has at least one opening that is perpendicular to said lower layer of polysilicon, said least one opening located only within an active area of said substrate, performing a first etch that removes said stressed layer not protected by said patterned phororesist, and performing a second etch that removes said etch stop liner not protected by said patterned photoresist.
5. The method of claim 4 wherein a stack of another etch stop layer and another stressed layer is formed on a trench isolation region located within said semiconductor substrate and a portion of said second semiconductor metal alloy layer abutting said trench isolation region.