Formation of PtSi Using Polycrystalline Si and Different Annealing Sequences
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Formation of PtSi Using Polycrystalline Si and Different Annealing Sequences Chin-An Chang and Armin Segmuiller IBM T. J. Watson Research Center, Yorktown Heights, N. Y. 10598
Abstract Formation of PtSi on As-doped polycrystalline Si is studied using different annealing sequences. An incomplete reaction between the Pt and Si is observed using a one-temperature anneal at 550 0 C, with unreacted Pt remaining in the film which is undesirable for the device processing. Using a three-temperature annealing sequence at 200-300-550 0 C in a N 2-H 2 mixture, a complete reaction is observed between Pt and Si, with no unreacted Pt detected. The results are similar to that using single crystal Si, except for the less-oriented PtSi formed. The three-temperature annealing process described has thus been shown useful to the fabrication of PtSi contacts at device areas containing either single crystalline or polycrystalline Si. Advances in device design and performance have demanded the successful fabrication of the structures using proper processes, as devices are scaled down in dimension and thickness. For the contact and interconnect materials silicides have been widely used due to several advantages: low resistivity, easiness of deposition and formation, and capability of selfalignment (1-3). Recently we have studied the effects of processing conditions on the formation of PtSi contact metallurgy using single crystal Si wafers. The annealing sequence, annealing ambient and the deposition techniques of Pt have been explored to compare the different PtSi films formed. A threetemperature annealing sequence using forming gas (N 2-H 2 ) mixture has been shown to provide the needed complete reaction between Pt and Si, an essential requirement for the formation of high quality PtSi and the protective surface oxide layer for the PtSi during etching in aqua regia (4). Comparison among the PtSi formed using different annealing sequences or ambients has shown the importance of achieving a complete reaction between Pt and Si (5-9). In this work, the effect of similar annealing conditions on the PtSi formation using polycrystalline Si is studied. Polycrystalline Si has been used as a gate material, used for high doping of the emitter region, used for achieving a shorter doping diffusion profile for reduced leakage, and used for trench fill (10, 11). The formation of both ohmic and high barrier Schottky contacts on polycrystalline Si using PtSi, therefore, becomes an important process for
Mat. Res. Soc. Symp. Proc. Vol. 106. @19B8Materials Research Society
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the device fabrication. It is, therefore, important to understand the effect of processing conditions on the PtSi formation using polycrystalline Si. A polycrystalline Si layer, 1800X thick, was deposited on single crystal Si wafers, n-type, (100) oriented, by chemical vapor deposition. The Si film was doped with As by ion implantation with a fluence of 2 x 1016. The implanted film was annealed at 8800C to drive in the dopant. A Pt film, 450A' thick, was deposited on the doped po
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