Akio Kita

Effect of Nitrogen Profile on Tunnel Oxynitride Degradation with Charge Injection Polarity.

The relationship between nitrogen profiles and polarity dependence of wearout and breakdown in oxynitride films was investigated. With positive bias stress, higher concentration of nitrogen atoms near an oxynitride/Si interface (∼2 at.%) and in the oxynitride bulk (∼0.3 at.%) reduce charge trap and interface state generation, and produce greater charge-to-breakdown (Q bd ). In contrast, with negative bias stress, nitrogen atoms near an interface decrease the number of charge traps, but, cannot reduce interface state generation, and thus give smaller Q bd . Furthermore, nitrogen atoms near an oxynitride surface (over 1.5 at.%) cause undesirable results for both bias stresses. Optimum nitrogen profile in an oxynitride film is discussed the viewpoint of reliability for both bias stresses.

Dopant Redistribution Effect on Post-Junction Silicide Scheme Shallow Junction and a Proposal of Novel Self-Aligned Silicide Scheme

It is concluded that in a shallow junction of post-junction silicide (PJS) scheme self-aligned silicide (SALICIDE) process, the decrease of impurity concentration at the TiSi2/Si interface significantly degrades performance of metal oxide semiconductor field effect transistor (MOSFET). It is verified for the first time that this degradation is due to dopant redistribution from Si to TiSi2 during post-silicidation annealing. Dopant redistribution is strongly confirmed by evaluation of the contact resistance at the TiSi2/Si interface and analysis of impurity concentration by improved secondary ion mass spectroscopy (SIMS) technique and a two-dimensional process simulation dealing with a SALICIDE process. In order to overcome the dopant redistribution-induced degradation, a novel SALICIDE scheme, doubly source/drain-ion-implanted SALICIDE (DIS), is proposed and concluded to be an alternative to PJS scheme.