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Chemical vapor deposition of aluminum films using tri-isobutyl aluminum on Si(lll) wafers has been studied from the viewpoint of structural and electrical properties of Al films as a function of substrate temperature (Ts). The epitaxial relation of Al on Si is found to be very sensitive to 7^, thus changing from Al(100)//Si(lll) with Al[llO]//Si[112] to Al(lll)//Si(lll) with Al[llO]//Si[liO] around 410 °C in the course of increasing Ts. The epitaxial relation is mainly determined at the initial stage of the deposition, but in some cases the relation changes with increasing film thickness. Above 420 °C, single-crystalline Al(lll) is grown on Si(lll), which has resistivity as low as the bulk value, high reflectivity, and a very flat surface.

I. INTRODUCTION

In recent years, the chemical vapor deposition of aluminum has been investigated because of its capabilities of conformable step coverage,1 selective deposition onto Si,2"5 and single crystal growth on the Si wafer.4'67 It is interesting that single-crystalline Al can be grown on Si in spite of the presence of a large lattice mismatch (25%) in this combination of materials. Kobayashi et al. have studied the epitaxial growth of Al on a Si(lll) surface by chemical vapor deposition with tri-isobutyl aluminum (TIBA) using a gas temperature controlled method, where gases were heated up to 230 °C.6 They have found that Al(lll) films are deposited on Si(lll) at a substrate temperature (Ts) of 400 °C, and that below 400 °C Al(lll) and Al(100) mixed structures are formed. They also studied the case of Al deposition on Si(100) and reported that around Ts of 400 °C the epitaxial relation changes from Al(100)//Si(100) to Al(110)//Si(100) in the course of increasing Ts.7 On the other hand, Tsubouchi et al. have reported that single-crystalline Al(100) on Si(lll) and single-crystalline Al(lll) on Si(100) are deposited by CVD with dimethylaluminum hydride (DMAH) at Ts of 270 °C in both selective and nonselective depositions of Al on Si.4 d'Heurle et al. have studied the epitaxial growth of Al on heated Si(lll) wafer and found that on films deposited at a Ts of 200 °C the epitaxial relation is Al(100)//Si(lll) with Al[liO]//Si[112]; on films deposited at 300 °C, Al(lll)//Si(lll) with AlfliO]// Si[110].8 These films have a polycrystalline structure. Yamada et al. have shown, using an ion cluster beam deposition (ICB) apparatus, the epitaxial relation as Al(lll)//Si(lll) with Al[ll0]//Si[ll0] on a Si(lll) 9 substrate cleaned by thermal desorption of J. Mater. Res., Vol. 7, No. 2, Feb 1992 http://journals.cambridge.org

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The above results can be summarized by saying that there are two types of epitaxial relations of Al on Si(lll), that is, Al(lll)//Si(lll) and Al(100)//Si(lll), depending on Ts. It is of interest how the epitaxial relation of Al on Si is determined in the case of CVD. In this paper, Al film properties, especially the epitaxial relations of Al on Si(lll), will be discussed as a function of Ts in a chemical vapor deposition with TIBA. II. EXPE