Nondestructive Study of Metal-Silicon Interfaces using Soft X-Ray Emission Spectroscopy
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Kadoma, Osaka 571, Japan + Research Laboratory for Surface Science, Faculty of Science, Okayama University, Okayama 700, Japan ** Osaka Electro-Communication University, Hatsu, Neyagawa, Osaka 572, Japan ++ Department of Mechanical Engineering, Tohoku Gakuin University, 1-13-1 Chuoh Tagajyo, Miyagi 985, Japan ABSTRACT Si L2 ,1~ valence band soft x-ray emission spectrum (SXES) due to an e ectron excitation for silicides shows a clear modiUsing this fact in fication from that for Si single crystal. combination with the incident angle variation(IAV) device, a non-destructive in-depth analysis of a Au(thin film)-Si(lll) contact is successfully carried out. Also, the SXES method has clarified the fact that a fair amount of the Si-s valence band density of state (yB-DOS) is included in the upper part of the yB-DOS for a Au-Si alloy, or Au-silicide, due to the Au-Si bond formation, which is a clear contrast to proposals given so far. 1. INTRODUCTION metal(M)-semiconductor(S) contacts have been playing imporBasic physics for the M-S tant roles in semiconductor devices. contacts, however, are still open for discussion, e.g. the Fermi level(EF) pinning[1J, the room temperature alloy formation at In order to have highly reliable the interface[2], and so on. and reproducible devices, it is necessary to have knowledge on physical properties of a M-S contact. There have been, therefore, quite a lot of fundamental works on M-S contacts, still leaving problems to be solved. A soft x-ray emission spectroscopy (SXES) has been carried out to have structural and electronic information on a metalCharacteristics of the SXES method are as Si(1ll) contact. follows: (1) the method is especially suitable for the determination of VB-DOS, because a core level involved in the soft xray emission has little wave number dependence[3]. (2) It can provide information corresponding to different electronic states, e.g. s-, p- and/or d-electronic DOS, separately due to the selection rule in a photon-emitting electron transition. In the present study, we have tried to elucidate the interface structure of a M-Si contact using an interesting application of the SXES method for a non-destructive in-depth analysis of a thin film-substrate contact system in a different way with the previous report[4], and also have intended to clarify the VB-DOS of a silicide.
255 Mat. Res. Soc. Symp. Proc. Vol. 320. @1994 Materials Research Society
2. EXPERIMENTAL
Metal(thin film)-Si(substrate) contacts were prepared by a conventional vacuum deposition of a metal film on Si(lll) substrate. A solid phase reaction[5] was adopted to have a M-Si alloy, or compound, where a metal film with thicknesses of
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