Source/drain engineering for sub 100-nm technology node
ITRS2001 indicates 25-nm physical gate length and 10-17-nm extension depth are required in 65-nm technology node for high performance application. It means resultant requirement of precisely controlled conventional process and new material and process introduction. Though ion implantation and spike RTA are still base line technology for doping, it should be carefully optimized in process integration avoiding implantation-induced damage and transient enhanced diffusion. Careless process sequence might cause undesired enlargement of junction depth even in LPCVD temperature annealing. Sidewall scaling is also necessary to reduce source and drain parasitic resistance and it relates to the contact junctions and silicidation process. Cobalt salicide is widely used in recent technology node. However, its silicon consumption in silicidation process requires relatively deep contact junctions and tends to cause the interference of the contact junction to the channel region. Therefore, lower silicon consumption silicide material such as nickel SALICIDE is one of the solutions. NiSi silicidation can be performed at low temperature and silicon consumption is about 80% of CoSi2 silicide under the same silicide thickness condition. Additionally, more structural approach like elevated source/drain using selective silicon or silicon-germanium will be introduced to solve severer constraints.