Deposition of silicon dioxide and silicon nitride by remote plasma enhanced chemical vapor deposition

Abstract

We have developed a low temperature process for the deposition of thin films of silicon dioxide and silicon nitride. The process consists of four steps: (a) excitation of an oxygen or nitrogen-containing molecule in an RF plasma; (b) transport of the excited oxygen or nitrogen species out of the plasma region; (c) mixing of the transported excited species with silane (or disilane) out of the plasma region to form precursor species; and (d) a CVD reaction at a heated substrate to form the desired thin film. We call this process remote plasma enhanced CVD (RPECVD). Silicon rich oxide films have been grown at substrate temperatures (Ts) between 100 and 350 °C using an excited O2/He mixture. Two different ‘‘silicon nitrides’’ have been deposited depending on the excited gas, NH3 or an N2/He mixture, and Ts. Using either nitrogen source and Ts greater than 450 °C, we obtain near stoichiometric films of Si3N4. On the other hand, films grown from NH3 and deposited with Ts of about 50 to 100 °C are silicon diimide [Si(NH)2], which is isostructural with respect to SiO2 with bridging NH groups substituted for the bridging oxygen atoms. Films grown from the NH3 source and at Ts between 150 and 450 °C are solid solutions of silicon nitride and silicon diimide. We discuss the application of these dielectric films in device structures.