• PDF / 910,669 Bytes
• 6 Pages / 612 x 792 pts (letter) Page_size
• 23 Downloads / 303 Views

DOWNLOAD

REPORT

---

Polycrystalline Silicon Thin Films For Microelectronic Applications Elena A. Guliants, Young J. Song and Wayne A. Anderson Department of Electrical Engineering, State University of New York at Buffalo, Buffalo, NY14260 ABSTRACT Polycrystalline silicon thin films with a thickness of 0.5-2µm were grown on 25nm thick Ni prelayers by d.c. magnetron sputtering from a Si target. In contrast to the conventional sputtering, the use of a thin Ni film allows the production of high crystallinity silicon at a temperature of 475°C and higher. The Ni disilicide grains formed at the Ni – growing Si film interface provide sufficient sites for the epitaxial growth of Si. The Si films with resistivity of 102-103Ω-cm possess a carrier lifetime of up to 11µs and a diffusion length of up to 3.4 µm, which makes them applicable to various microelectronic devices. As an example, Schottky diodes fabricated on 0.5µm thick Si films exhibit a forward-to-reverse current ratio of 107. The technique is easily implemented on a variety of substrates. INTRODUCTION The formation of high-quality polysilicon on inexpensive, low-melting point substrates, such as glass, plastic and polymers, offers the opportunity to actualize both high device performance and low cost. As a consequence, there is currently a significant effort in research directed at reducing the thermal budget for Si crystallization. Most of the existing methods deal with the low-temperature crystallization of pre-deposited amorphous Si thin films using timeconsuming furnace annealing or high-cost laser annealing. At the previous MRS conference, we introduced the low temperature enhanced Si crystal growth on a Ni silicide prelayer [1]. Briefly, the technique involves the silicon deposition directly onto thin Ni films. The Si atoms arriving at the growing front immediately interact with the Ni atoms to form the Ni-rich NiXSiY phase. An increase in the concentration of the Si atoms available for the silicide formation results in a transition to a more Si-rich silicide phase. The Ni silicide phase formation and transformation is controlled by the Ni-Si interdiffusion kinetics. When Ni is consumed completely, the most favorable phase, NiSi2 forms, and the continued Si deposition leads to the nucleation of the Si grains on the surface of the Ni disilicide. This phenomenon relies on the Si heteroepitaxy on NiSi2 due to only 0.4% lattice mismatch between these two materials possessing a cubic structure [2]. In the recent work [1,3], we reported some of the structural properties of the nickel-induced grown polysilicon, emphasizing the strong influence of the Ni prelayer thickness on the Si grain size. The grain size was observed to have a maximum corresponding to the Ni thickness of 25nm, when the latter was varied from 5nm to 100nm. It was suggested that below this value, the impurities hinder the nucleation of the silicide crystals, while the thicker Ni films provide a greater number of the nucleation sites which lead to a decrease in the grain size of both NiSi2 and Si. The resulting Si film e