Epitaxial Growth and Thermal Stability of CoSi 2 Layer on (100) Si from Co-C Films without Capping Layer
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he growth interface above 500'C using an inter-mediated layer[2]. Indeed, the formation of epitaxial CoSi, on (100) Si has been observed in titanium-interlayer mediated epitaxy (TIME)[3] and oxide mediated epitaxy (OME)[4]. Recently. we reported the epitaxial growth of (100) CoSi, layers from cobalt-carbon (Co-C) films deposited on (100) Si using an metallorganic source with a Ti capping layer[5.6]. The method can grow an epitaxial CoSi, layer on (100) Si substrate without employing an interlayer between Co and Si because the supply of Co by diffusion in Co-C film is suppressed as in the interlayer-mediated epitaxy. An amorphous Co-C alloy film was deposited on a Si substrate by metallorganic chemical vapor deposition (MOCVD) of cyclopentadienyl dicarbonyl cobalt. Co(1r5-CHJ(CO),. The CVD method for the metal deposition using metallorganic precursors often does not produce pure metal films at low temperature due to incomplete decomposition of the metal-carbon bond. The MOCVD of Co(ir'-CH.)(CO), causes Co-C films because the cobalt-carbon bond strength in cyclopentadienyl dicarbonyl compound is stronger than that in other cobalt organometallic compounds[7-9]. The epitaxial growth of CoSi, layer on Si (100) substrate without capping layer was investigated in this work to simplify the SALICIDE process. The growth behavior of epitaxial CoSi, layers on Si (100) substrate was observed by TEM. In addition, the electrical characteristics of the p-n junction diode and the thermal stabilities of CoSi, film and diodes were investigated for their practical application to deep submicron devices.
145 Mat. Res. Soc. Symp. Proc. Vol. 564 ©1999 Materials Research Society
EXPERIMENTAL P-type (100) oriented Si substrates with a resistivity of 5-8 Qcm were cleaned in a HS0 4/H,O, solution, rinsed in de-ionized water, dipped in HF(I%), rinsed in de-ionized water, and then loaded into an MOCVD reactor. Co-C films with 20nm thicknesses were deposited from Co(ri 5-C5 Hs)(CO)2 at 480 mTorr with 50 sccm H, carrier gas. The temperatures of the bubbler and substrate were 35'C and 350°C, respectively. No capping layer was deposited on the Co film. The capping-layer deposition process was omitted to simplify the SALICIDE process, expecting that Co is less oxidized in cobalt-carbon film during annealing than pure cobalt film. Subsequent ex-situ rapid thermal annealing (RTA) was carried out in N, ambient at temperatures between 500 and 800'C for 1-5 min. To investigate the electrical characteristics, p'n junction device structures were fabricated. The active area of the square type diode was defined by patterning SiO,. The process flow of the
p'n junction was as follows: well ion implantation, oxide deposition (400 nm), patterning, BF,' implantation (30 KeV, 3 x 1015 cm2), patterning. P implantation (30 KeV, 5 x 10'5 cm2 and 60 KeV, 5 x 1015 cm 2), and drive-in (1000°C, 10 s by RTA). After cleaning the as-fabricated p'n diode substrates using the diluted HF dipping, a 20 nm thick Co-C layer was deposited on the junctions in a MOCVD reactor. The
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