Browsing by Author "YANG, FM"

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EVALUATION OF INSITU FORMED W-TI AND MOSI2 AS A DIFFUSION BARRIER TO AL FOR COSI2 SILICIDED CONTACT
(1993-05-01)
YANG, FM
;
CHEN, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A simple metallization process to form a shallow CoSi2 silicided contact and W-Ti diffusion barrier simultaneously has been developed. The process starts with depositions of a Co-Ti alloy layer and an overlying W layer on silicon wafers using a dual e-beam evaporation system; this is followed by a single-step annealing treatment in a normal flowing-nitrogen furnace. On the other hand, bilayer self-aligned shallow MoSi2/CoSi2/Si silicided contact can be derived from the W/Co-Mo/Si system by a two-step annealing treatment performed in the same environment. I-V characteristics for silicided p+n diodes with the diffusion barriers formed in situ were measured after they had been finished with Al deposition and post-Al annealing at temperatures from 350 to 600-degrees-C in N2. For comparison, Al/CoSi2/p+n and Al/p+n structures were also investigated. It turns out that the integrity of Al/W-Ti/CoSi2/P+n and Al/MoSi2/COSi2/P+ n silicided contacts can be preserved up to 5 50 and 500-degrees-C, respectively, for a 20 min annealing, while that of Al/CoSi2/P+n can be kept only up to 450-degrees-C.
FORMATION OF BILAYER SHALLOW MOSI2/COSI2 SALICIDE CONTACT USING W/CO-MO ALLOY METALLIZATION
(1992-04-01)
YANG, FM
;
CHEN, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A very simple process to form a bilayer shallow MoSi2/CoSi2/Si silicided contact using W/Co54Mo46/Si bilayer alloy metallization has been developed. Two-step annealing in a conventional flowing-nitrogen furnace is employed. The first annealing is performed at a temperature of 500-600-degrees-C, with the W film passivating the underlying Co-Mo alloy layer from being oxidized and consuming some Co. A shallow contact is feasible by selectively etching away the remaining outer layer of the Mo-dominant Mo-Co alloy (or W-Co alloy) phase to deduct the metal source which would finally be transformed into silicides. Silicide lateral growth which is observed during the silicidation of Co on Si does not occur in the present system. This is presumably because the formation of CoSi2 is not preceded by Co2Si or CoSi due to the nonrich Co source in the Co-Mo alloy system. The second annealing performed at a higher temperature of 700-950-degrees-C is to further transform the CoSi2 and mixed-silicide layers obtained after the first annealing into separate layers of MoSi2 and CoSi2.
FORMATION OF COBALT SILICIDE UNDER A PASSIVATING FILM OF MOLYBDENUM OR TUNGSTEN
(1991-05-01)
YANG, FM
;
CHEN, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A very simple and reproducible cobalt silicide process with Mo/Co or W/Co bilayer metallization to overcome the oxidizing liability of Co annealed in a normal flowing-nitrogen furnace has been developed. Cobalt is deposited on blank and patterned silicon wafers in an electron-beam evaporation system followed by Mo (or W) deposition without breaking the vacuum. The cobalt silicidation is carried out using a two-step annealing process. The first annealing is performed at a temperature ranging from 400 to 600-degrees-C, during which the role of the upper layer of Mo (or W) is to protect the underlying Co layer from being oxidized while not disturbing the cobalt's silicidation process. Perfect selective etching of Mo (or W) can be accomplished by a NH4OH + H2O2 + (2-3)H2O solution. The second annealing is performed at a higher temperature of 750-degrees-C to completely transform the CoSi obtained in the first annealing into CoSi2 and induce grain growth of CoSi2, thus lowering the resistivity. X-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and sheet resistance measurement are used to characterize the silicide phase and microstructure.
FORMATION OF SELF-ALIGNED COBALT SILICIDE IN NORMAL FLOW NITROGEN FURNACE
(1992-01-30)
YANG, FM
;
CHEN, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Cobalt can be completely transformed into cobalt silicide during annealing in a normal flow nitrogen furnace above a certain temperature which depends on the thickness of the cobalt film deposited on the silicon substrate. For a 400 angstrom cobalt film this temperature is 500-degrees-C and for a 1500 angstrom cobalt film it is 650-degrees-C. Loading the wafer into furnace tube is a critical step to prevent the cobalt from oxidation before silicidation in the annealing process. Lateral growth of silicide is not observed using this silicidation scheme. The cobalt oxide together with the underlying cobalt over the silicon oxide can be removed by hot 3HCl + H2O2 + 3H2O solution if the annealing is performed at a temperature below 650 and 900-degrees-C for a cobalt film thickness of 400 and 1500 angstrom respectively. The optimum condition for practical silicide formation is defined. The products and microstructure over the silicon and silicon oxide are characterized by X-ray diffraction spectra, Auger electron spectroscopy depth profiles, sheet resistance measurements and scanning electron microscopy inspection.
METALLIZATION OF W/CO-TI/SI AND SIMULTANEOUS FORMATION OF DIFFUSION BARRIER AND SHALLOW COSI2 CONTACT IN NORMAL FLOWING-NITROGEN FURNACE
(1993-09-01)
YANG, FM
;
PENG, JG
;
HUANG, TS
;
HUANG, SL
;
CHEN, MC
A structure of W-Ti/CoSi2/Si can be formed from an appropriate metallization system of W(400 angstrom)/Co63Ti37(360 angstrom)/Si at temperatures from 620 to 760-degrees-C in a normal flowing-nitrogen ambient. The W-Ti alloy layer is only slightly oxidized on the shallow surface and can be used as a diffusion barrier between the aluminum and silicide. Furthermore, silicide lateral growth does not occur in this silicidation scheme. However, an additional intermediate Ti-silicide and/or Ti-oxide as well as a Ti-oxide layer on the surface will be formed if the content of Ti in the Co-Ti alloy exceeds that required to saturate in the overlying W film, e.g., W (400 angstrom)/Co63Ti37(840 angstrom)/Si. The Al/W-Ti/COSi2/p+ n diodes with metallization using this scheme are able to maintain the integrity of I-V characteristics with a post-Al annealing at 550-degrees-C for 20 min. In addition, epitaxy of CoSi2 occurs in this metallization system.
PHASE-TRANSFORMATION OF MO AND W OVER CO OR ITS ALLOY IN CONTACT WITH SI
(1994-01-15)
YANG, FM
;
CHEN, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Tungsten or molybdenum deposited on a cold silicon substrate (W/Si or Mo/Si) using an electron-beam gun at a base pressure of 10(-6) Torr, are unable to form a silicide, even when annealed at 900-degrees-C in either ambient N2 or H-2. We present an easy method by which Mo and W silicides can be formed under the same deposition and annealing conditions with the help of an intervened layer of cobalt or its alloy. Investigations were performed on various metallizations of Mo/Co/Si, W/Co/Si, W/Co-Mo/Si, Co-Mo/Si and Co/Mo/Si, annealed in a normal flowing-nitrogen furnace or in ambient H-2. In the Mo/Co/Si systems (or W/Co/Si), Mo (or W) silicide can be formed at 900-degrees-C over CoSi2 which is formed at a lower temperature and is in contact with Si. The residual silicon oxide on the silicon surface is thought to inhibit the silicide formation of W and Mo. The presence of cobalt, which is not impeded by the surface residual silicon oxide or other impurities for silicide formation, can induce silicidation of W and Mo. The reason for silicide formation at higher temperatures in preference to the metal oxide is based on the Ellingham diagram. In the W/Co-Mo/Si system, three silicides Of WSi2, MoSi2 and CoSi2 are formed at a high temperature of 900-degrees-C. A mechanism for phase array of the silicides is proposed. In the Co/Mo/Si system, where stable Co3Mo and Co7Mo6 compounds are formed in advance, no silicide can be formed even at 950-degrees-C.