Abstract
There are several challenges about gate dielectric thickness scaling in MOSFET, such as increased equivalent oxide thickness(EOT) value due to the growth of interfacial layer(IL)、reliability, and oxygen vacancies induced threshold voltage(Vt) variation. This thesis consists of three parts to discuss the impacts on characteristics of gate stack process of 16 nm FinFET, which are interfacial layer desorption by high temperature annealing to reduce IL thickness and defects、reducing Vt variation by passivaMetal nitrideg oxygen vacancy at interface and reducing EOT by incorporating few oxygen vacancy into high-K with modulating oxygen content in atomic layer deposition(ALD), and scavenging IL by increasing oxygen diffusion with a post metal annealing(PMA) and effects of PMA temperature and nitrogen gas flow ratio on metal cap. In the first parts, desorption of IL was carried out at high temperature for different annealing periods in N2 ambient. The desorption of IL in I/O FinFET can be obtained, which in confirmed by the reduced EOT. With increasing annealing time the on current and transconductance of devices increase. Reduced off current、enhanced mobility and reliability for PFinFET are achieved. The improvement may be attributed to the densification of IL after annealing. However, off current、subthreshold swing(S.S.), and mobility in NFinFET degrade after annealing. Which may be due to more diffusion in source draun junctions and defect generation at interface caused by a high temperature annealing. In the second part, high-K deposition is formed with different Oxygen precursor and Metal precursor cycle time in ALD to tune the oxygen vacancy distribution. Results of Core FinFET show that the EOT decreases, but S.S.、mobility and reliability degrade for sample with oxygen vacancy rich at both interface and bulk. Sample with oxygen vacancy deficiency at interface shows improved Vt variance 、off current and reliability, but increased EOT induced degraded S.S. and on current. Sample oxygen vacancy rich at interface shows the reduced Vt roll off、reduced Vt variation and S.S., and improved reliability. The on current also increases due to reduced EOT. In the third part, PMA on metal nitride cap were performed at varies temperatures and gas ambients. EOT slightly increases with increasing anneal temperature and decreasing flow ratio of nitrogen gas, which induced S.S. and DIBL degradation. It may be attributed to interfacial layer regrowth with increasing the annealing temperature. IL regroeth caused by oxygen diffusion from metal nitride cap is more by decreasing nitrogen gas flow ratio in ambient.