Low-temperature adsorption and decomposition of borazine on the Si(100)-(2 × 1) surface

Abstract

Borazine adsorption at a surface temperature (Ts) of - 120°C and the thermal decomposition of borazine have been investigated on the Si(100)-(2 × 1) surface using temperature-programmed desorption (TPD) and static secondary ion mass spectrometry (SSIMS). The initial reactive sticking coefficient (S0) at this temperature was measured as 0.08. Borazine dissociates by breaking BH and/or NH bonds to form silicon monohydride species, SiH, even at -120°C because of the highly reactive silicon dangling bonds. The monohydride then decomposes at 550°C to desorb H2. After the initial decomposition stage, subsequent borazine molecules (α1-borazine) can coadsorb intact with the partially decomposed borazine (β-borazine). α1-borazine eventually desorbs molecularly with a peak temperature of 110°C. Taking into account the coexistence of both α1- and β-borazine, the saturation coverage of borazine (θBZ) was estimated as 1.2 molecules per surface Si atom. After borazine adsorption and subsequent high-temperature annealing (900°C), the surface contains boron and nitrogen originating from decomposed borazine. This surface is less reactive ("poisoned") towards borazine adsorption. Above 900°C, the nitrogen- and boron-containing Si surface further decomposes to evolve SiN or Si2N. © 1992.