AMORPHOUS SI-B FILMS - MICROSTRUCTURE AND ELECTRICAL-PROPERTIES

The properties of and potential uses for thin films of amorphous Si:B alloys are summarized. The films were deposited by low-pressure chemic al vapor deposition of silane and diborane. The boron content of the s amples was controlled by regulating the reaction of diborane and silan e gases during the deposition. The alloy and its oxides possess many d esirable properties for microelectronic applications, including high m icrohardness, resistance to chemical etching, high and tailorable cond uctivity, ease of oxidation, and (for die oxide) high resistivity and dielectric strength. The microstructural stability of the films is exc ellent. The volume fraction of crystallinity of the as-deposited films was reduced dramatically by increasing the boron content, as was crys tallization upon annealing. Transport at low temperatures is seen to b e dominated by hopping. The linear oxidation rate was observed to be r adically enhanced by the presence of large amounts of boron. The elect rical properties of die oxides were seen to be comparable to SiO2. Usi ng a simple model relating the physical mode of boron incorporation in the amorphous network, mechanisms for the crystallization inhibition, the oxidation enhancement, and the electrical properties are discusse d. These are consistent with stoichiometric and spectroscopic properti es of the alloy and its oxides.