Formation of Epitaxial NiSi 2 and CoSi 2 On Laterally Confined (111)Si
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FORMATION OF EPITAXIAL NiSi2 AND CoSi
2
ON LATERALLY CONFINED (lll)Si
C.S. CHANG, C.W. NIEH AND L.J. CHEN Department of Materials Science and Engineering, University, Hsinchu, Taiwan, Republic of China
National Tsing Hua
ABSTRACT Epitaxial NiSi 2 of single orientation was grown on laterally confined (1ll)Si. Striking oxide opening size effects on the growth of NiSi2 epitaxy were observed. The formation temperature of NiSi2 on (111)Si was found to be as low as 550 °C inside oxide openings 1.8 urmor smaller in size. Epitaxial NiSi 2 of single orientation which is identical to that of (lll)Si substrate was formed inside oxide openings of or smaller than 1.8, 1, and 0.8 um in size in samples annealed at 550-750, 800, and 850-900 °C, respectively. Preliminary results on the epitaxial growth of CoSi2 are also reported. I.
INTRODUCTION
Epitaxial silicides have received much attention in recent years for their key role in gaining fundamental understanding of the electronic properties of the silicide/Si interfaces and potential applications in novel devices. [1-5] In comparison to the large number of investigations performed on unconfined silicide layers, the number of studies on confined layer is small. However, in applications, silicide films are always laterally confined. [6] In this presentation, we report the results of a study on the size effects on the formation of NiSi2 and CoSi2 epitaxy on silicon. For non-ultrahigh vacuum (non-UHV) treatment conditions, two types of epitaxial NiSi 2 and CoSi2 were found to form on (lll)Si simultaneously at about 800 °C. The orientations of type A and type B epitaxial films grown on (lll)Si are identical to and rotated by 1800 with respect to the substrate normal, respectively. [7-9] NiSi 2 or CoSi2 was formed on (lll)Si with either one of the two epitaxial orientations and NiSi 2 was grown on (O01)Si with type A orientation under UHV deposition and annealing conditions. [10] Almost single crystalline NiSi2 and CoSi 2 grown on silicon with a complicated preannealing-laser annealing-postannealing process was also reported. [11] A recent report showed that singlecrystalline CoSi 2 can be grown on (lll)Si by rapid thermal annealing under non-UHV condition. [12] II.
EXPERIMENTAL PROCEDURES
Patterned wafers were provided by Xerox Palo Alto Research Center. (111) silicon wafers, 15-25 0-cm and boron doped, were first cleaned by standard RCA process followed by a plasma enhanced chemical vapor deposition to form 400 nm in thickness oxide at 380 °C. Standard lithographic process and plasma etching were used to open windows of Si0 2. The pattern consists of square- and circular-shaped openings, 0.6-10 pm in size. A scanning electron micrograph of part of the pattern is shown in Fig. 1. Patterned wafers were chemically cleaned by trichloroethylene and acetone followed by etching in a dilute HF solution (HF:H 2 0 = 1:50). The passivation SiO2 films were reduced to about 150 nm in thickness after chemical etching. The samples were then dipped in the dilute HF solution for 2 min immedi
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