Formation of NiSi-Silicided p + n Shallow Junctions Using Implant Through Silicide and Low Temperature Furnace Annealing
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Formation of NiSi-silicided p+n shallow junctions using implant through silicide and low temperature furnace annealing Chao-Chun Wang, Chiao-Ju Lin, and Mao-Chieh Chen Department of Electronics Engineering, National Chiao-Tung University 1001 Ta Hsueh Road, Hsinchu 300, Taiwan ABSTRACT NiSi-silicided p+n shallow junctions are fabricated using BF2+ implantation into/through thin NiSi silicide layer (ITS technology) followed by low temperature furnace annealing (from 550 to 800oC). The NiSi film agglomerates following a thermal annealing at 600oC, and may result in the formation of discontinuous islands at a higher temperature. The incorporation of fluorine atoms in the NiSi film can retard the formation of film agglomeration and thus improve the film’s thermal stability. A forward ideality factor of about 1.02 and a reverse current density of about 1nA/cm2 can be attained for the NiSi(310Å)/p+n junctions fabricated by BF2+ implantation at 35 keV to a dose of 5×1015cm-2 followed by a 650oC thermal annealing; the junction formed is about 60nm measured from the NiSi/Si interface. Activation energy measurements show that the reverse bias junction currents are dominated by the diffusion current, indicating that most of the implanted damages can be recovered after annealing at a temperature as low as 650oC.
INTRODUCTION Metal silicides have been widely used in microelectronic applications because of their low and metal-like resistivies and high temperature stability; in addition, they reduce the sheet and contact resistances of gate and diffusion regions. Among various metal silicides, nickel monosilicide (NiSi) has been recognized as a promising candidate for contact metal in deep sub-micron device applications [1-14]. NiSi has a low electrical resistivity (14~20µΩ-cm), low formation temperature (350oC), and wide process temperature window (350 to 750oC); it also consumes less Si material than TiSi2 and CoSi2. These peculiarities make NiSi suitable for usage in the low-temperature process for sub-100nm CMOS technology [11,12]. In this work, we investigate the thermal stability of the NiSi film and the fabrication and characterization of the NiSi contacted p+n shallow junction formed by BF2+ implantation into/through nickel silicide (ITS) followed by low temperature furnace annealing.
EXPERIMENTAL The NiSi/p+n junction diodes were fabricated on n-type, (100)-oriented silicon wafers with 2.7~4.0-cm nominal resistivity. After standard RCA cleaning, 5500Å thick SiO2 was thermally grown by pyrogenic oxidation at 1050oC. Active regions with areas of 1100×1100, 580×580, 270×270, and 120×120µm2 were defined by the method of photolithography followed by the chemical wet etching technique. A nickel (Ni) film of 150 Å thickness was sputter deposited in a
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dc sputtering system
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