T. P. Chow

Refractory metal silicides: Thin-film properties and processing technology

The thin-film properties of refractory metal silicides are reviewed along with related VLSI process technology. Material considerations, including thin-film deposition techniques, film structure, electrical properties, are covered. Single-level and composite gate structures implemented with these silicides are described. Thin-film processing-plasma etching, thermal oxidation, ion-beam-enhanced silicide formation, dopant implantation-of these materials is discussed from the perspective of VLSI compatibility. Characteristics of MOS devices and circuits using these silicides are reviewed.

Modification of Schottky barriers in silicon by reactive ion etching with NF3

Reactive ion etching of silicon with NF3 gas has been found to alter the silicon surface such that the Schottky barrier height is systematically changed with ion energy. The energetic ions introduce a net positive surface charge which increases the barrier height on u2009p‐Si and decreases it on n‐Si. The Schottky barrier modification is found to be a function of ion energy as well as gas plasma used.

Thermal Oxidation of Sputtered Silicon Carbide Thin Films

Proprietes physiques et oxydation des couches minces de carbure de silicium. Les techniques employees sont: lellipsometrie, la spectrometrie SIMS, diffraction RX, la retrodiffusion Rutherford

Plasma Etching of Refractory Gates for VLSI Applications

Etat actuel de la gravure par plasma dans le cas des schemas a haute resolution. Gravure des metaux refractaires (Mo, W) et de leurs siliciures (MoSi 2 , WSi 2 , TaSi 2 ): vitesse et anisotropie dattaque, selectivite relativement a SiO 2 , aux resists, et autres materiaux en couches minces. Les options sont le reactif (CF 4 , NF 3 , CCl 4 ), le gaz additionnel (O 2 , Ar, He) et la configuration du reacteur (plasma planaire, gravure ionique reactive, diode flexible, triode). Description des facteurs influencant le controle des profils des bords des structures a niveau unique et grille composee. Detection du point final. Discussion de processus fondamentaux, desorption des produits de reaction, effets sur les caracteristiques dattaque

Titanium silicide formation on BF+2‐implanted silicon

Thin‐film interaction between titanium and BF+2 ‐implanted silicon substrates at 650–900u2009°C was investigated. At 650u2009°C, the incomplete Ti/Si reaction led to formation of a surface layer (∼600 A thick) of titanium‐rich silicide (Si/Ti ∼1.6) on top of a near‐stoichiometric silicide layer. Annealing at 700u2009°C or higher resulted in conversion of the titanium film into predominantly TiSi2 and a lower sheet resistance. After annealing, boron was found to redistribute into the silicide layer and fluorine was segregated onto the silicide/silicon interface, but neither species apparently affected the overall sheet resistance for BF+2 dosages up to 6×1015 cm−2. A sheet resistance of ∼0.7 Ω/⧠ was obtained after annealing between 700 and 900u2009°C for 30 min.

The effect of phosphorus ion implantation on molybdenum/silicon contacts

Formation of Mo/Si contacts by implantation of phosphorus ions was studied. The implantation was carried out at temperatures of −196, 25, and 150u2009°C and a fluence ranging between 1015 and 1017 ionsu2009cm−2. The morphological and structural characterizations were done with scanning electron microscopy, transmission electron microscopy, and x‐ray diffraction. Hexagonal MoSi2 phase was identified in samples implanted with more than 1016 ionsu2009cm−2 at all three implantation temperatures. Traces of MoP were found in the sample implanted with 1017 ionsu2009cm−2 at 150u2009°C. Measured effective contact resistance showed ohmic behavior in as‐implanted samples except for samples implanted with 1015 ionsu2009cm−2 at 150u2009°C. Smooth surfaces of implanted MoSi2 structures remained after post‐implant annealing at 850u2009°C for 1/2 h in H2 ambient. The effect of post‐implant annealing is also discussed in terms of doping, microstucture, and contact resistance.

Thermal oxidation of niobium silicide thin films

Thermal oxidation of niobium silicide thin films on oxidized silicon substrates has been investigated. The silicide films were rf sputtered from a hot‐pressed alloy target of stoichiometric composition (Si/Nb∼2) onto heated (350u2009°C) substrates. Oxidation was carried out in dry and wet oxygen between 550 and 850u2009°C. From Rutherford Backscattering Spectroscopy (RBS) measurements, it was determined that the oxide films exhibited the same Si/Nb ratio as the initial silicide layer. While only Nb2O5 has been cleary identified, density considerations and experimental values of oxide thickness suggest that niobium and silicon oxides coexist. The composition of the remaining silicide layer did not change significantly during oxidation. The oxide growth was found to follow a (tox)nα (time) relationship, with n∼1.1 for dry oxygen and 1.4 for wet oxygen. Activation energies of 1.9 and 1.6 eV were determined for the dry and wet oxidation processes.

Titanium Silicide Formation on Boron‐Implanted Silicon

Thin film interaction between Ti and boron-implanted silicon substrates at 650/sup 0/-900/sup 0/ C was investigated. The compositional properties were examined with Rutherford backscattering spectrometry and secondary ion mass spectrometry, the structural properties with x-ray diffraction, and the electrical properties with sheet resistance measurements. At 650/sup 0/ C, incomplete Ti/Si reaction led to significant amounts of intermediate silicide phases (Ti/sub 5/Si/sub 3/ and TiSi) and hence higher sheet resistance. Annealing at 700/sup 0/ C or higher resulted in conversion of the titanium film into predominantly TiSi/sub 2/ and a lower sheet resistance. Boron was found to redistribute into the silicide layer during annealing, leading to an accumulation on the surface and a depletion at the silicide/silicon interface. The diffusion kinetics of boron through titanium silicide are compared with those of other p- and n-type dopants.

New high voltage IC technology

This paper describes a new 500 volt junction isolated BIMOS technology developed by and recently brought into production at the General Electric Company. It differs from previously reported junction isolated (J.I.) high voltage IC (HVIC) technologies in the versatility and ruggedness is provides. As such, it not only addresses the display driver markets, but also those dealing with power conditioning and control.

Silane silicidation of Mo thin films

Silicidation of molybdenum thin films has been obtained for the first time from the reaction of molybdenum with silane (SiH4). Auger electron spectroscopy measurements indicate a uniform MoSi2 film has been grown. X‐ray diffraction data show that films silicidized at relatively high flow rates have a dominant Mo component along with a significant hexagonal MoSi2 phase. Post‐reaction annealing in H2 results in the complete disappearance of Mo with the concurrent increase of various silicide phases (MoSi2, Mo3Si). The growth kinetics were investigated as a function of reaction time and temperature and reactant flow rate. The sheet resistance of the reacted films can be controllably varied between that of Mo and of MoSi2. Post‐silicidation annealing behavior was found to be strongly ambient dependent. Oxidation of the reacted films resulted in a uniform SiO2 overlayer.