The Al <sub> 2 </ Sub> O <sub> 3 </ Sub>, Gaas, And Zno Thin Films Atomic Layer Deposition Study

With the rapid growth of IC industry,CMOS technology has become the most widely used technology.With the scaling down trend the traditional process technology can not satisfy the requirements of the development of IC industry when the feature size is reduced down to 45nm where the EOT of gate dielectric layer should be less than 1nm,in which condition the tunneling current is becoming significant.At the same time,the aspect ratio of DRAM capacitor is increasing,which need perfect thin film step coverage urgently.Facing these challenges,the conventional thin film deposition techniques can hardly fulfill these demands,at the same time a new technique—Atomic Layer Deposition was introduced in modern CMOS technology.Due to many outstanding characters of ALD,it has been widely used in many fields within Microelectronics.This thesis firstly focused on the Al₂O₃ thin film atomic-layer-deposited on Si substrates of different orientations(Si(100),Si(110) and Si(111)).It turned out that in the experiment the thin film grow speed is about 4%～10%slower on Si(110) than on Si(100) and Si(111) substrates,it is probably due to the surface atom density on Si(110) is higher than the other two,which cast certain influence on the film deposition;it is also found that the samples of Si(110) and Si(111) with 900s TMA pretreatment barely has apparent oxidized silicon XPS peak in the film or interface, while they can be obviously observed in XPS spectres of those samples without TMA pretreatment;at the same time,no obvious silicon oxide XPS peak was found in those Si(100) samples.We also found that the C-V curves shifted positively for those samples with TMA pretreatment,the reason to this might be reduction of oxygen vacancy near the interface or introduction of negative charges during deposition process.Secondly this thesis studied the initial reaction mechanism of ALD GaAs on hydroxylated SiO₂ surface with precursors TMGa and AsH₃.The results show that both half reactions are exothermic and energetically favorable.The energy barrier is 14.22 and 40.94kcal/mol for TMGa and AsH₃ half reactions respectively,which means AsH₃ half reaction is comparatively harder to proceed,thus longer AsH₃ pulse time maybe preferred in the latter half reaction.Although small energy barriers are to be overcome to get to the desorption states in both half reactions,this could be easily achieved by elongating inert gas pulse time in the experiment.Finally ALD nitrogen doped ZnO initial reaction on Si(100) surface is discussed using DFT method.All three half reactions in the deposition as well as their procedure, reaction pathway and representative chemical bonds length are provided.All three half reactions are energetic favorable.The results show that transition state barrier of the diethyl Zinc half reaction is 32.951 kcal/mol,while the product energy is 16.506 kcal/mol lower compared to the reactants.The two half reaction in the second part are parallel,the NH₃ half reaction and the H₂O half reaction are exothermic by 15.641 and 24.966 kcal/mol comparing to the reactants structure respectively,and the transition state energy barrier of them are 33.916 and 22.489 kcal/mol.It is apparent that H2O half reaction is easier to proceed,which could leave -ZnOH^* sites on the surface for further ALD deposition,less -ZnNH₂^* surface sites are in accordance with dopants nitrogen atoms.The two half reaction in the second part require more energy thus longer pulse time for diethyl Zinc is suggested in the experiment in order to get better-ZnCH₂CH₃^* surface group coverage.