| Summary: | 博士 === 國立清華大學 === 材料科學與工程學研究所 === 85 === The formation of NiSi2 and CoSi2 on silicon inside 0.1-0.6 μm oxide openings prepared by electron beam lithography has been investigated by transmission electron microscopy, field emission scanning electron microscopy, auger electron spectroscope, thin films stress measurement, and sheet resistance measurement.
Two types of electron beam resists, positive type resist ZEP520 and negative type chemical amplified resist SAL601, were used in the electron beam direct writing lithography. The O.1 μm oxide openings pattern in the oxide layer can be achieved by the optimized control on the electron beam direct writing, resist, and reactive ion etching processes.
The optimum conditions for the mix-and-match technology combined with electron beam direct writing lithography and optical G-line stepper including alignment mark process, resist process and etching process have been investigated. The polysilicon gate was etched by electron cyclotron resonance with Si02 thin mask in HBr/O2 gas, for the appropriate anisotropy of etching and for the polysilicon-to- oxide selectivity of HBr/O2 gas plasma. The well defined profile of polysilicon gate with O.1 μm width has been obtained successfully.
For epitaxial growth of NiSi2 on (111)Si inside 0.1-0.6 μm oxide openings prepared by electron beam lithography, striking effects of size and shape of deep submicron oxide openings on the growth of NiSi2 epitaxy were observed. Epitaxial growth of NiSi2 of single orientation on (111)Si was found to occur at a temperature as low as 400 ℃ inside contact holes of 0.2 μm or smaller in size. Contact holes were found to be more effective in inducing the epitaxial growth of NiSi2 of single orientation than that of linear openings of the same size. The effects of size and shape of lateral confinement on the epitaxial growth of NiSi2 on (111)Si are correlated with the stress level inside oxide openings.
The self-aligned formation of CoSi2 was achieved on the selective epitaxial growth (SEG) silicon layer on (001)Si inside 0.1-0.6 μm oxide openings prepared by electron beam lithography. The uniform, high quality SEG Si layer was grown by ultrahigh vacuum chemical vapor deposition at 560℃ with Si2H6 Self-aligned CoSi2 film without lateral growth of silicide was grown on the SEG Si layer by rapid thermal annealing at 700℃ in N2 ambient. The successful integration of the self-aligned CoSi2 and SEG of Si processes promises to be a viable process technology for the future deep submicron devices.
The formation and growth of CoSi2 inside 0.2-2 μm linear oxide openings and contact holes prepared by electron beam lithography has been investigated. A thin, uniform epitaxial CoSi2 was grown inside 0.5 μm or smaller linear openings and 0.7 μm or smaller contact holes by both one-step and two-step rapid thermal annealing processes. On the other hand, both the epitaxial and polycrystalline CoSi2 were found to form inside 0.6μm or larger linear openings. The size effect of oxide openings is correlated to the distribution of local stress induced at the oxide edge. The formation of CoSi at low temperature was found to be retarded by the local compressive stress near the edge of linear oxide openings. The relative ease in the epitaxial growth of CoSi2 near the oxide edge of linear openings and of 0.7 μm and smaller contact holes is attributed to the thinness of the CoSi layer.
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