Thin-film formation and properties of tungsten silicide and epitaxial yttrium silicide

This thesis is an experimental study of the formation and resulting properties of two different silicides: WSi{dollar}sb2{dollar} and YSi{dollar}sb{lcub}rm 2-x{rcub}{dollar}. Thin films of WSi{dollar}sb2{dollar} are grown by sputter depositing W metal onto p-type Si(100) wafers. The samples were fast radiatively processed at 1100{dollar}spcirc{dollar}C and 1150{dollar}spcirc{dollar}C in a rapid thermal processing (RTP) system under vacuum (P {dollar}sim{dollar} 10{dollar}sp{lcub}-6{rcub}{dollar} Torr). The resistivities measured (30-40 {dollar}muOmega cdot{dollar} cm) are among the lowest reported for thin film WSi{dollar}sb2{dollar}. Dopand and impurity redistributions are studied as functions of RTP conditions. Oxygen is the major impurity in these systems and is gettered at the W-Si interface from the vacuum ambient to form an oxide diffusion barrier which prevents silicide formation at temperatures below 1100{dollar}spcirc{dollar}C. Above 1100{dollar}spcirc{dollar}C, the interface oxide barrier is reduced by reaction with silicon from the substrate to allow silicide formation. This is confirmed by simulating RTP in an ultra-high vacuum (UHV) ambient where the W-Si interaction is shown to proceed at lower temperatures. This is possible due to the lack of oxygen in UHV for the creation of an effective interfacial oxide diffusion barrier.; Epitaxial YSi{dollar}sb{lcub}rm 2-x{rcub}{dollar}(0001)/Si(111) structures are grown completely in-situ UHV, first from the deposition of yttrium only. The results are epitaxial films with chi-minima from RBS channeling yields {dollar}sim{dollar}3% and low resistivities ({dollar}sim{dollar} 50 {dollar}muOmega cdot{dollar} cm), but with highly defected structures in the form of large areal coverages of pinholes exposing the Si(111) substrate to the surface. Reactive deposition of yttrium onto heated Si(111) improves film quality, as does the use of thin templates. Pinhole-free epitaxial YSi{dollar}sb{lcub}rm 2-x{rcub}{dollar} films can be grown by depositing both yttrium and silicon in the appropriate atomic ratio. This prevents nucleation with the substrate and maintains a relatively low interface free energy, as compared to that from the highly defected interface intrinsic to nucleation type growth. Since atomic silicon from an evaporation source appears to react with yttrium at lower temperatures than does solid silicon, YSi{dollar}sb{lcub}rm 2-x{rcub}{dollar} growth can proceed layer-by-layer without nucleating a reaction with Si(111), yielding pinhole-free films.