Abstraet-Long-term reliability for a p+ poly gate MOS structure was tested under low electric field bias temperature (BT) stress in comparison with an n+ poly gate. A significant increase in interface state density was observed for the pf poly gate MOS structure under positive bias conditions. This phenomenon was not observed in the n + poly gate case. The mechanism for this interface state increase was investigated in detail. Several possible causes, such as mobile ions, excess boron concentration in the gate oxide, electron injection from the substrate, impact ionization in the gate oxide, and bole injection from the gate electrode, were considered. All of the causes, except hole injection, were obviated by experiments. Although hole injection current was too small to be detected, hole injection from the p+ poly gate is a possible cause, which could explain the interface state generation under positive-bias temperature test. For applying a p+ poly gate to CMOS structures, care should be taken when positive bias is applied to the gate electrode.
Tungsten-filled via hole structure reliability was studied. It was experimentally determined that the electromigration reliability for conventional non-filled via holes reduces with via hole diameter reduction. On the contrary, tungsten-filled via hole reliability was independent from the via hole diameter and improved significantly, compared with the non-filled via hole structure. The electromigration failure mechanism for the tungsten-filled via hole structures was investigated by two-dimensional numerical simulation. Current crowding points were found near the via hole edge in the aluminum part. Via hole resistance change during the electromigration test was also evaluated. When aluminum-silicon was used for the metal lines, via hole resistance increase phenomenon was found, due to the migration of silicon in the aluminum line. However, it was estimated as being negligibly small for usual operating conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.