Method for the formation of a boron-doped silicon gate layer underlying a cobalt silicide layer

Abstract

Process for forming a boron-doped silicon gate layer underlying a cobalt silicide layer that reduces the risk of grooving and agglomeration of cobalt silicide layer, as well as boron penetration into a gate oxide layer. The process includes providing a PMOS transistor structure that includes an N-well on a P-type silicon substrate, a gate oxide layer and a silicon gate layer. Next, a cobalt layer is deposited on the PMOS transistor structure, which is then subjected to a first thermal treatment to form a bilayer CoSi/silicon stack structure. After removing unreacted cobalt, boron dopant (BF,or B,) and nitrogen ions (N,) are implanted into the bilayer CoSi/silicon stack structure. The bilayer CoSi/silicon stack structure, implanted boron and implanted nitrogen are then subjected to second thermal treatment to form a CoSi,layer on the silicon gate layer and to thermally activate the implanted boron. Also included is a process where a PMOS transistor structure that includes an N-well on a P-type silicon substrate, a gate oxide layer and a silicon gate layer is first provided, followed by the implantation of nitrogen into the silicon gate layer. Next, a cobalt layer is deposited on the PMOS transistor structure, which is then subjected to a first thermal treatment to form a bilayer CoSi/silicon stack structure. After removing unreacted cobalt, boron is implanted into the bilayer CoSi/silicon stack structure. The bilayer CoSi/silicon stack structure and implanted boron and implanted nitrogen are then subjected to second thermal treatment to form a CoSi,layer and to thermally activate the implanted boron.