Investigation of seal nitride process in 32nm beyond HK/MG technology

Seal nitride process of High-k/Metal Gate (HK/MG) technology is developed from offset nitride process of Poly/SiON technology which is widely used to define the source/drain extension area for overlap capacitor reduction and boron diffusion control of short channel effect improvement. In HK/MG technology era, the seal nitride process becomes more critical than Poly/SiON because the dummy poly will be removed in MG last process. The seal nitride process will not only be used to reduce overlap capacitance, short channel effect improvement, but also the seal nitride height impacts the metal gate electrode height for performance improvement which is retained after lightly doped drain, spacer formation process, etc. In this paper, the comparison between conventional nitride process and in-situ carbon doped seal nitride process is developed to prevent boron diffusion for better short channel effect control, also the process is developed to achieve lower wet etch rate for better critical dimension retention of lightly doped drain implantation control, metal height control after dummy poly removal. A different carbon concentration process is further developed after process tuning with the film characterization of wet etch rate, XPS measurement of impurity components, SIMS for carbon profile check and the electrical data is demonstrated to prove the performance gain.