Disilanyl‐amines — compounds comprising the structural unit SiSiN, as single‐source precursors for plasma‐enhanced chemical vapour deposition (PE‐CVD) of silicon nitride

Abstract

AbstractAs potential single‐source precursors for the plasma‐enhanced chemical vapour deposition of silicon nitride, a series of disilanyl‐amines has been prepared containing the structural unit SiSiN. Hexachlorodisilane reacts with Et2NH to yield (Et2N)Cl2SiSiCl2(NEt2), 1, and (Et2N)2ClSiSiCl(NEt2)2, 2, while with (i‐Pr)2NH the compounds [(i‐Pr)2N]Cl2SiSiCl3, 3, and [(i‐Pr)2N]Cl2SiSiCl2[N(i‐Pr)2]2, 4, are formed as colourless, stable liquids (1–3) or solids (4). The crystal structure of 4 has been determined. The molecule shows a staggered gauche conformation (dihedral angle NSiSiN 71°, SiSi 1.670 Å). Compounds 2–4 are converted into the corresponding hydrides 6–8 in good yields by reaction with LiAlH4 in monoglyme, while 1 is undergoing an isomerization to give 1,1‐bis(diethylamino)disilane (5) in this process. The disilanes 5–8 are colourless liquids, not spontaneously inflammable in air. 1,2‐Bis(di‐i‐propylamino)disilane (BIPADS), 8, was chosen for down‐stream mode PE‐CVD of silicon nitride. With substrate temperatures at 300°C, high quality thin films were obtained at high growth rates. These films show refraction indices of 1.631 – 1.814 and have low carbon and very low oxygen contents, but high (Si‐bound) hydrogen contents. Good insulating properties and good resistance to aqueous alkaline etching are further characteristics which could make BIPADS‐generated films an attractive alternative to conventional plasmanitride materials. BIPADS is easy to handle and reduces the hazards usually associated with standard silane precursors.