Atomic Layer Deposition Of Ultra-thin Tin And Al <sub> 2 </ Sub> O <sub> 3 </ Sub> Film Theory And Based On The Mos Device Of Selenium Nanowires

Since the first integrated circuit coming up in 1958,micro-electronics technology is developing very quickly.The goal of microelectronic technology development is to continuously improve the performance of the system integration and cost-effective, and to improve the integration on chips,which is the power source for shrinking the feature size of semiconductor devices.In order to improve performance and reduce costs,the development of integrated circuits has followed the famous Moore's Law for more than 40 years.With the feature size reduction of integrated circuit device, new materials,new devices and new techniques are emerging.Atomic layer deposition(ALD) is one of new technologies.It can be used to prepare the ultra-thin high-k gate dielectric,and also can be used to prepare the ultra-thin diffusion barrier for the advanced copper interconnection.At the same time,ALD is often used to prepare high-density dielectric capacitors in DRAM device.In this paper,we carry out a systematic theoretical research about the atomic layer deposition of TiN and Al₂O₃ films;In addition,we also studied the preparation and electrical properties of Se nanowire-MOSFET.The results from this paper have an important guiding significance for ALD technique in the application of nanometer integrated circuits.First of all,we research the initial growth mechanism of SiOC as the low-k interconnect dielectric ALD on the TiN barrier layer.The study found the reaction mechanism of TiCl₄ adsorption on Si-OH group.Firstly,as the polarity of-OH, Cl-Ti-Cl bond angle of TiCl₄ molecules gradually become larger and near to-OH. And then a Cl atom of TiCl₄ combines with the H atoms of -OH and desorb from the surface,which need to overcome a small reaction barrier.And the energy of the reaction product must be less than 8.71 kcal/mol,which shows that the reaction is easy towards to the reaction products.For the adsorption reaction of TiCl₄ on the Si-CH3 group,the study found that as a result of the weak polarity -CH3,Cl-Ti-Cl bond angle of TiCl₄ molecules slightly become larger,and the relative position will remain basically unchanged with-CH₃,which is not easy close to the surface.So, TiCl₄ is hard to carry on the absorption reaction on the surface of Si-CH₃.Using density functional theory,we investigate the adsorption of water and trimethyl aluminum(TMA) on single-walled carbon nanotubes(SWCNTs) during the initial stage of Al₂O₃ atomic layer deposition.our calculations show it is difficult for water to dissociatively adsorb on SWCNT from weakly molecular physisorbed state because of the high activation energy of 1.94 eV.The energy of water dissociation state is 0.20 eV higher than the reactants,which suggests that the reaction product is unstable.For the final state,hydrogen and hydroxyl group of water molecule are dissociatively adsorbed on C(1) and C(2) atoms,forming the C-H(dC-H=1.10 A) and C-0(dC-O=1.48 A) bonds.We find that the vibrational frequencies for C-H bend and C-0 stretch are at 1280 cm^-1 and 998 cm^-1 respectively,which is in good agreement with earlier Fourier transform(FT) IR spectra data.The next study shows that TMA tends to adsorb on the hydroxyl surface site of the SWCNT through the interaction between Al atom and O atom with adsorption energy of 0.80 eV.One CH₄ molecule is released through the combination of the hydrogen atom of surface hydroxyl site and the-CH₃ group of TMA.The activation barrier is calculated to be 0.65 eV.The resulting product is stable according to the calculation,with relative energy of -1.70 eV compared to the reactants.Our calculations suggest that OH functional group on SWCNT can assist molecular adsorption procedures.Moreover,we find the adsorptions of water and TMA do not have much effect on the electronic structure of the SWCNT.Using focused ion beam(FIB) method,we produced a Se nanowire MOSFET for the first time,and study its electrical properties.The study found that when exposed to light,the channel currents have significantly improved at different Vds,which indicate the photosensitive properties of Se nanowires make the device have the characteristics of optical switch.Through the study of the transfer characteristic curve, the device shows that p-channel depletion mode of MOSFET characteristics.When Vds changed from 2.5v to 5v,the current channel is improved up about 10 times,and the threshold voltage shift to the positive direction.This is because when Vds larger, the channel currents is larger at the same gate voltage;and for the P-channel depletion-type devices,it need greater positive voltage to cut off the conductive channel.At the same time,when Vds changes greater,it will also result in large reverse current.Analysis shows that whether or not there is light,I_on/I_off is basically the same,about 10²,the threshold voltage Vth is about -2 V.By calculating,the resistivity of this device is basically the same as the actual materials - Se,about 10²Ω·cm.