The dopant (B, P, and As) redistribution in a silicide on polycrystalline silicon structure after annealing at 800 and loOO ·C was studied. The distribution of boron was found to be quite different from these of phosphorus and arsenic. At 1000 ·C, the distribution coefficient for boron at the WSi 2 /polycrystalline silicon interface was found to be 2.7. The solubilities of phosphorus and arsenic in WSi 2 at 1000·C were estimated to be 6X lO19 and 1.6X 10 19 atoms/cm 3 , respectively. At 800 ·C, the diffusion coefficient for the dopants was found to be equal to, or greater than 3.3 X lO-12 cm 2 /s, which is at least three orders of magnitude larger than in silicon.
The nature of residual ion-implantation damage responsible for gettering deleterious impurities from active semiconductor device regions in Si has been studied. A propensity for dislocations of the type b=1/2 〈110〉 to gather metallic contaminant (e.g., Cu), as compared to Frank partials b=1/3 〈111〉, is established. Transmission electron microscopy and pulsed leakage measurements are used to demonstrate that the density of 1/2 〈110〉 dislocations introduced by Xe implantation greatly influences gettering efficiency.
To obtain the advantages of refractory metal silicide composite structures (i.e., silicide/polysilicon/gate oxide) for VLSI applications, these structures have to be defined with little impact on ground rules or subsequent wafer processing. This paper studies film definition using both parallel plate and barrel plasma reactors. The parallel plate system meets all criteria. Etch rates for polysilicon, WSi2, and SiO~ were studied using CFJO~ plasmas. The edge profile of the defined composite structure is dependent on the etch rate ratios of the constituent layers, and these results agree with the classical model for isotropic etching. A process is defined with acceptable edge profiles. Operational IGFET devices with 1-2 ~m dimensions have been produced.
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