DISILANYL-AMINES - COMPOUNDS COMPRISING THE STRUCTURAL UNIT SI-SI-N, AS SINGLE-SOURCE PRECURSORS FOR PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION (PE-CVD) OF SILICON-NITRIDE

As 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-degrees, Si-Si 1.670 angstrom). Compounds 2 - 4 are converted into the corresponding hydrides 6 - 8 in good yields by reaction with LiAlH, 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 downstream mode PE-CVD of silicon nitride. With substrate temperatures at 300-degrees-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.