Chemical Vapor Deposition of Cobalt Silicide
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CHEMICAL VAPOR DEPOSITION OF COBALT SILICIDE GARY A. WEST AND KARL W. BEESON Allied-Signal, Inc., P. 0. Box 1021R,
Morristown,
NJ 07960
ABSTRACT Cobalt silicide films have been deposited by chemical vapor deposition using Co 2 (CO) 8 or HCo(CO) 4 as the Co source The Co:Si ratio of the and SiH4 or Si 2 H6 as the Si source. and CoSi 2 films increases with the deposition temperature, stoichiometry is obtained at 3000 C using SiH4 or at 2250 C Resistivities of films is the Si precursor . when Si 2 H6 deposited in the range CoSi 2 .0 to CoSi 3 .0 are typically 200 microohm-cm and drop to 30 - 40 microohm-cm upon annealing at 9000 C. INTRODUCTION gate, contact or can be used as Metal silicides interconnect metals for Si or GaAs discrete devices and Silicides such as CoSi 2 , WSi 2 , TaSi 2 , integrated circuits. MoSi? and TiSi 2 are noted for their high temperature thermal this group, [I] . In and low resistivity stability have the lowest measured CoSi? and TiSi 2 polycrystalline resistivity (-15-20 microohm-cm) at room t*IAperature [2]. there is a of CoSi 2 , the notable exception With vapor covering chemical of literature body considerable Metal halides such deposition (CVD) processes for silicides. as WF6 [31 TaCl 5 [4], TiCl 4 [5], MoF 6 [6] and MoCl 5 [7] are Cobalt halides, on the common gas sources for the metals. other hand, have relatively high melting points (CoC1 2 , m.p. ca. 1200 C) and low vapor pressures at 7240 C; CoF 2 , m.p. moderate temperatures which renders them poorly suited for CVD. Aylett et al. [8] have demonstrated cobalt silicide deposition from the precursor H3 SiCo(CO) 4 which contains both Co and Si. However, the resulting films have a Co:Si ratio of 1:1.3 and Metal depositions of W and this ratio cannot be easily varied. Mo have been done by CVD from their respective carbonyls [9]. incorporation of A common problem using metal carbonyls is A limited amount of CVD carbon and oxygen in the final films. work has been published on Co deposition from Co 2 (CO) 8 [10] which indicates that carbon and oxygen contamination is not a It is possible to indirectly form problem for this system. depositing Co metal on CoSi2 using the Co CVD process by first reacting the layered and then thermally a Si substrate In many cases, however, it may structure to form the silicide. not be possible or desirable to use the substrate as the Si source. One example is the use of cobalt silicide Schottky In this gates on GaAs [11] where a Si source is not present. case, CVD of the silicide, not just the metal, is required. We show that high quality stoichiometric CoSi 2 films can be produced by CVD using Co 2 (CO) 8 or HCo(CO) 4 as the cobalt We source and SiH4 or SiZH6 as the precursor for Si . characterize the depositlon -ates, film compositions, and film Carbon and over a wide range of conditions . resistivities oxygen contamination are low and the Co:Si film ratio is easily controlled by varying the deposition temperature. Mat. Res. Soc. Symp. Proc. Vol. 131. ©1989 Materials Research Society
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