Bonding constraint-induced defect formation at Si-dielectric interfaces and internal interfaces in dual-layer gate dielectrics

As aggressive scaling of integrated circuits continues into the next centur y, insulators with dielectric constants higher than SiO2 with different loc al bonding arrangements will be required to increase gate dielectric capaci tance in field effect transistor devices. An important issue in semiconduct or device physics is determining whether differences between the bonding at (i) Si-SiO2 interfaces and (ii) interfaces between crystalline Si and alte rnative gate dielectric materials will result in increased densities of ele ctrically active defects at the alternative dielectric interfaces, thereby limiting targeted levels of performance and reliability. In particular, it is important to understand from a chemical bonding perspective why Si-SiO2 interfaces display both low defect densities and high reliability, while ot her interfaces such as Si-Si3N4 with similar bending chemistry, display def ect densities that are at least two orders of magnitude higher. Building on previously established criteria for formation of low defect density glasse s and thin films, constraint theory is extended to crystalline Si-dielectri c interfaces that go beyond Si-SiO2 through development of a model that is based on the average bonding coordination at these interfaces. This approac h identifies quantitative bonding criteria that distinguish between device- quality and highly defective interfaces. This extension of constraint theor y is validated by its application to interfaces between Si and stacked sili con oxide/nitride dielectrics which demonstrates that as in bulk glasses an d thin films an average coordination, N-av>3 yields increasingly defective interfaces. Finally, the universality of this application of constraint the ory is demonstrated by showing that defect densities scale with overcoordin ation in the same way in thin films and at interfaces. (C) 1999 American Va cuum Society. [S0734-211X(99)03904-9].