Study On Microstructure And Characteristics Of Ni-Mo Doped Cr-Si Thin Films

Si-rich high-ohmic Cr-Si thin film,as a high performance semiconducting transition-metal silicides,has been widely used in microelectronics fields.For precise thin-film resistors,the most important technical feature is the low temperature coefficient of resistance?TCR?.So,it is necessary to improve the TCR of intrinsic CrSi₂ films by doping modification of CrSi2 films.In this work,based on the research about Cr-Si high resistance film of the research group,high-resistance Cr-Si-Ni,Cr-Si-Mo and Cr-Si-Ni-Mo thin film resistors were prepared and studied.Two kinds of resistance film whose micro-structure differ greatly,were deposited by the magnetron sputtering method at a small current and ion beam sputtering method.And then XRD and SEM were performed to explore the differentiation between the microstructure of different doping Cr-Si films.Based on the above research,this paper revealed that the TCR of Cr-Si thin film resistors were closely related to the doping elements and microstructure.And the resistive thin films were prepared successfully,which had low temperature coefficient of resistance and smooth surface without observable defects.At the same time,the heat and humid experiment was performed to analyze the resistance to heat and humidity.Then,the analysis on the process of thin film growth was performed.Nano-thin film growth model about the different thickness were built using the Monte Carlo method.Using this model,the kinetic equations about the growth inhibition of the nanocrystals were established.And then,the growth process of Cr-Si-Ni-Mo targets on the surface of resistance was simulated by MATLAB.The simulation results show that it has an obvious inhibition on the growth of thin film when the thickness effect worked on the upper and lower surfaces of thin film.First principles are classic calculation methods for semiconductor materials study.The innovation of this paper is that the first principles were applied into the film experiment firstly.The electron charge density difference distributions,energy band structures and density of states of pure CrSi₂ and doped CrSi₂ have been calculated using the plane-wave-based pseudo-potential method based on the density functional theory?DFT?with the generalized gradient approximation?GGA?.The calculated band structure of intrinsic CrSi₂ showed that the indirect band gap is 0.35 eV.These results were in good agreement with the previous experiment and theoretical calculation.The band gap of CrSi₂ narrows and the energy levels increase within per unit of energy after CrSi₂ was doped.The impurity energy levels appear at the bottom of the band conduction and the top of valence band after substituting a Ni atom for a Cr atom.The reason is that Ni is the deep level impurities in the CrSi₂.Due to Mo and Cr belonging to the same group,isoelectronic traps were produced.Compared to single element doped,Ni-Mo co-doping CrSi₂ took advantages of both.And the electrical structure of co-doping CrSi₂ had shown a stable tendency.Based on the above calculations,these optical parameters of CrSi₂ were properly calculated and researched.And it turns out that optical properties were well improved by doping.These results also verified changes of electronic structure from another perspective.The calculated results of the first principles are consistent with the experimental results.It proves that the Ni-Mo co-doping makes the high-resistance Cr-Si based film more stable.So this paper successfully illuminates the mechanism of the lower TCR of Ni-Mo doping CrSi₂.