Phase equilibria for evaluating thermal stability of VLSI metallization schemes

Phase diagrams have been a recognized and important tool in the development of science and technology for more than hundred years. Owing to their lack of availability, their use in microelectronics has been limited. Continued device miniaturization has led to increased concerns regarding the compatibility of material phases and the chemical stability of interfaces at elevated processing temperatures. As the layers used in VLSI metallization result in interfaces involving typically three to four elements, it is imperative that the appropriate ternary and quaternary phase diagrams be considered.;An existing methodology for calculation of condensed portions of ternary phase diagrams has been extended to quaternary systems. Diagrams for Ti-Si-N-O, Al-Si-N-O, Ti-Al-Si-N, and Ti-Al-Si-O have been calculated from existing and estimated Gibbs free energy data. The stability of different layers comprising a typical metal-oxide-semiconductor (MOS) circuit has thus been addressed. Thin-film reactions involving four elements have also been studied.;The stability of TiWN--with Ti/W ratio varying from 0 (WN) to ;The Cu-Ti-W-N quaternary phase diagram has been calculated, indicating fundamental differences in the stability of Cu (compared to Al) with TiWN. The applicability of the proposed method to other areas of materials science is illustrated for a SiC-Ni...