LOW-TEMPERATURE BEAM-INDUCED DEPOSITION OF THIN TIN FILMS

Ion and electron beam-induced deposition (BID) of thin (1-4-mu-m), conductive films is accomplished by dissociating and removing the nonmetallic components of an adsorbed, metal-based, molecular gas [SnCl4 and (CH3)4Sn]. Previous research has focused primarily on room-temperature (monolayer adsorption) BID using electrons and slow, heavy ions. This study investigates low-temperature (120 K) BID in which the condensation rate of the precursor gas is well controlled. The residual metallic films are produced by using as incident beams either 2-keV electrons, 25-keV H2+, or 50-keV H2+, all of which provide predominantly electronic energy deposition, or 30-keV Ar+, which provides predominantly nuclear energy deposition. Residual films are analyzed ex situ by scanning electron microscopy, mechanical thickness measurements, resistivity measurements, Rutherford backscattering spectroscopy, and infrared spectrometry. A model is developed that considers bulk and surface dissociation mechanisms and sputtering to describe the BID process. The derived cross sections for the formation of a residue from condensed (CH3)4Sn are nonlinearly related to the total deposited energy approximately to the 1.4 power. The lowest electrical resistivity values of the residues (650-mu-OMEGA cm) are obtained only by significant loss of carbon, which is strongly dependent on the nuclear stopping power.