Rapid Thermal Annealing of Ni/Al/Si and Ni/Si Systems
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RAPID THERMAL ANNEALING OF Ni/Al/Si AND Ni/Si SYSTEMS A. KATZ AND Y. KOMEM4 Dept. of Materials Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel ABSTRACT The effect of Rapid Thermal Annealing on phase formation and diffusion processes in the Ni(30 nm) /Al(10 nm)/Si system was studied and coxpared to a Ni(30 nm)/Si reference system. Heat treatments were carried out at temperatures between 400 °C and 900 °C for 2 seconds. The results obtained by means of TEM, AES and XRD indicated that the Ni/Al/Si system underwent a local melting in the intermediate Al layer at the Al/Si eutectic temperature (577°C). This reaction, due to the rapid melting process, resulted in formation of a unique layered-structure composed of a columnar polycrystalline layer (60 nm thick) of Ni 2 Si and NiSi adjacent to the Si substrate with relatively smooth interface and an outer layer of two separate polycrystalline films (both about 10 m thick) of AI 3Ni (inside) and Ni(Alo.sSio. 5 ) (outside). Under the same rapid thermal processing conditions the Ni/Si reference system underwent a solid state reaction which resulted in the formation of a polycrystalline layer (60 m thick) composed of Ni 2 Si and NiSi as well as NiSi=. INTRODUCTION The utilization of Rapid Thermal Annealing (RTA) or processing (RTP) as a method for short time annealing (STA) has recently become very attractive in VLSI circuit fabrication [1]. These STA processes are mostly used in order to get fast crystallization and electrical activation of amorphyzed substrates and formation of metal silicides such as of Nickel [2,31. However, formation of metal-silicon contacts induced by melting reactions were obtained only by applying techniques such as ion beam irradiation and pulsed laser [4]. Recently, the authors have demonstrated that Rapid Thermal Melting (RTM) [5] can be used in a controlled manner and results in the formation of a new contact structure in the Ni/Al/Si system. In this article the morphology and structure of this contact are reported and compared to the structure of the contact formed in the Ni/Si system under the same STA conditions. EXPERIMENTAL PROCEDURE Two wafers of N-type [100] Si, having resistivity of 10-12 Qcm, were cleaned in a standard cleaning procedure [61 and put in an evaporating system. Al (10 rm thick) and Ni (30 mm thick) films were deposited on one of the wafers while on the other one only Ni (30 mmthick) was deposited, so both the primary (Ni/Al/Si) and reference (Ni/Si) systems were deposited simultaneously. The depositions were performed by means of an electron beam gun at a rate of 0.2-1.0 nm/sec and under an initial pressure of 5.10-' Torr. Subsequently, two pieces (1 x I am square), one of Ni/Al/Si and the other of Ni/Si were placed nearly on a special temperature sensor [5] inside the chamber of a Heatpulse~ annealer and were rapid thermally processed simultaneously under N2 atmosphere.
Mat. Res. Soc. Symp. Proc. Vol. 74. c 1987 Materials Research Society
648
The structure, morphology and composition of the r
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