The Effects of Processing Ambient on the Reaction Rate of Ti and Si Using Rapid Thermal Processing
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THE EFFECTS OF PROCESSING AMBIENT ON THE REACTION RATE OF Ti AND Si USING RAPID THERMAL PROCESSING A. KERMANI*, K. FARNAM**, AND T. STULTZ* 94538 * Peak Systems, inc., Fremont, CA ** Advanced Micro Devices, Sunnyvale, CA
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ABSTRACT The reaction rate of sputter deposited Ti films on c-Si as a function Sintering temperatures ranging from 600 to of process ambient was studied. 0 The 1100 C, under pure ammonia, forming gas, nitrogen and argon were used. additional effect of a reactively sputtered TiN cap on the reaction rate Processed films were then analyzed using AES, RBS was also investigated. It was found that for and four point probe resistivity mapping. 0 temperatures below 700 C, an ammonia ambient has the most pronounced effect on reducing the rate of formation of titanium silicide, followed by forming Additionally, the presence of the gas (N 2 /H2 10% vol), nitrogen and argon. TiN cap further reduced the reaction rate while exhibiting significant For the samples annealed in diffusion of nitrogen into the silicide film. ambients containing nitrogen, a thin layer of The thickness Ti N was simultaneously formed on top of the silicide film. an6 9toichiometry of this titanium nitride films were then correlated with The details of these findings and the sintering temperature and ambient. their impact on the formation of the self-aligned titanium silicide (salicide) will be presented.
INTRODUCTION The continuing demand for faster devices with higher degree of reliability and lower power consumption has resulted in the need for The benefit of increased speed narrower gates with very shallow junctions. however, will not be realized if higher conductivity materials are not substituted for polysilicon gates, and control over these small dimensions Metal silicides, for instance, can effectively cannot be accomplished. compensate for higher RC delay times induced by smaller geometries [1-31. The application of refractory metal silicides as contacts and interconnects in VLSI fabrication for CMOS, NMOS and Bipolar technologies have been Extensive research has demonstrated by a number of investigators [2,4-7]. been done on the reaction kinetics, microstructure, film thermal stability and resistivity of tungsten [2,4], molybdenum [8], tantalum [9-13] and Among the refractory metals, titanium is titanium silicide [5,8,13,14]. found to be of particular interest because of its lower resistivity, thermal stability, oxide reducing ability and ease of selectively etching the unreacted metal. Although titanium has a high affinity for oxygen, a well controlled reaction environment would eliminate the formation of the And finally, co-formation of titanium undesirable titanium oxide film. nitride layer in nitrogen containing ambients has potential application as a good barrier to silicon migration into aluminum metallization in MOS devices. One of the primary applications of the titanium is in formation ?f ýhe self-aligned silicides (salicides), which reduces the resistance of n /p A thorough regions used as source/drain, and pol
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