THE ADSORPTION OF SILANE, DISILANE AND TRISILANE ON POLYCRYSTALLINE SILICON - A TRANSIENT KINETIC-STUDY

The adsorption of silane, disilane and trisilane on polycrystalline si licon was investigated using temporal analysis of products (TAP) follo wing on admission of a reactant pulse in the temperature range 300-100 0 K and at pressures typical for low-pressure chemical vapour depositi on. Up to 650 K a slow adsorption process is operative for the three s ilanes. A quantitative description of the adsorption in this temperatu re range is possible with a mechanism based on an insertion reaction o f the silanes into surface hydrogen bonds. Above 650 K a much faster m ode of adsorption is observed, which for the higher silanes is accompa nied by silane formation. Homogeneous gas-phase reactions can be exclu ded. Silane adsorption above 820 K can be described quantitatively wit h a dual-site adsorption mechanism.