Epitaxial Growth of Transition Metal Silicides on Silicon
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INTRODUCTION
Metal silicides have been widely used as ohmic contacts, Schottky barriers, gate electrodes and interconnects in microelectronic devices in recent years. [1,21 The miniaturization of integrated circuit devices necessiates modification of the present interconnect and contact technology. Epitaxial silicides possess several attractive characteristics to meet the demands. The impetuses for the study of epitaxial silicides were mainly stemmed from their high thermal stability [3], low stress at the interface [4], alleviation of grain boundary effects [3,5], low resistivity. [5,6] Regular atomic arrangement of the silicide/Si interface permits basic understanding of the origin and electronic properties associated with the interfaces. [71 The growth of epi-Si/epi-silicide/Si double heteroepitaxy structure facilitates the fabrication of novel classes of devices. [8,9] Channelled ion implantations are useful for shallow junction devices. [10] The performance of infrared detectors may be improved by the formation of silicide epitaxy. [11] For about fifteen years following the first discovery of the epitaxial PtSi, there were only four generally known epitaxial silicides i.e., PtSi, Pd2Si, NiSi2 and CoSi2. [12-15] FeSi2 was found to grow epitaxially on (lll)Si in 1983. [16-18] More recently, eight different refractory silicides, manganese silicide and platinum group silicides were grown epitaxially on silicon. [19-271 The growth of epitaxial near noble silicides on silicon have been reviewed in recent years. [5,6] Preliminary results of the growth of platinum group silicide epitaxy will be reported in this proceedings. [27] In this presentation, epitaxial growth of refractory metal silicides, FeSi2 and manganese silicides are reviewed. Almost all epitaxial refractory silicides were grown by the solid phase epitaxy method with the possible exceptions that MoSi 2 and WSi2 were also reported to grow preferentially on silicon by the chemical vapor deposition method or molecular beam epitaxy technique. [28-30] The crystal structures of the stable phase of epitaxial silicides are listed in Table I. II. *
SAMPLE PREPARATION AND CHARACTERIZATION Present Address:
Department of Electronics Engineering, National Chiao Tung University, Hsinchu, Taiwan, Republic of China.
Mat. Res. Soc. Symp. Proc. Vol. 54. c 1986 Materials Research Society
246
Table I TiSi
4
(C54) TiSi
2
(C49)VSi
2
(C40)
VI A Cr24 CrSi
2
(C40)
a=8. 253A
a=3.62A.
a=4.571A
a=4.428A
ib=4.783A
(b=13.76A
c=6.372A
c-6.363A
c=8.5404
c=3.60A
Zr
a=3.721A {b=14.689 c=3. 683A
P26
,8nSi
FeSi
.
1 7
a-5.531A c=65.311A
A2 7 Co
Ni28
(Tet)FeSi 2 (Al1)CoSi 2 (CI) NiSi 2 (Cl) a=2.684A a=9.863A a=5.365A a=5.406A C_5.128A {b=7.791A 2
c-7.833A
bSi
Tc4
Mo
qb41 (C49) 2
VIII
VII A Mn25
4
4 2
40
ZrSi
5
2
Crystal structures of epitaxial silicides
V A T•322
IV A
2
(C40)TIoSi
(C40) 'RoSi 2
a=3.203A
c=6.424A
c=7. 855A
73
TaSi
2
(C42(CRSa 2 (C40)
a=4.7821a4.614A c=6.5695A c-6.414A
44
1Rh45
Pd
46
Pd 2 Si(C22' a=6.494 "3.4
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