Study On Preparation And Dielectric Properties Of Ca(Mg_1/3Ta_2/3)O₃/CaTiO₃Heterogeneous Thin Films

Duo to outstanding insulating properties and dielectric properties, dielectric thinfilms are widely used in semiconductor integrated circuits、thin film hybrid integratedcircuits、some multi-functional devices design, and so on. The drastic decrease of thethickness lead to the great changes in aspect of physical and chemical properties ofthin films compared with bulk ceramics, at the same time the crystal structure、micromorphology、 dielectric properties are determined by the preparation technicalparameters and hetero structure composite of thin films. The study on influencesfactors of structure and dielectric properties have great practical significance andapplication value on functional devices design and enhancing dielectric properties.In this paper, Pechini method is employed to prepare Ca(Mg1/3Ta2/3)O3(CMTa)and CaTiO3(CT)precursor solutions, Ca(Mg1/3Ta2/3)O3-CaTiO3(CMTa-CT)homogeneous structure and hetero structure thin films were prepared by liquidspin-coating process on Pt(111)/Ti/SiO2/Si(100) substrates. The crucial techniqueparameters and pre-treatment technology of CMTa and CT precursor solutions arestudied. The results show that, Via adjusting the pH value. The chelation reactionbetween Ta5+and carboxylic acid can be occurred; after the heat treatment, metalbridge oxygen bonds (Ta-O、Ca-O、Mg-O) can be formed. Both CMTa and CT showa pure perovskite structure.The effects of pre-treatment time and thickness on structure、micro morphology、dielectric properties of CMTa、CT homogeneous thin films are studied. The resultsshow that, with longer pre-treatment time, the grains turn to be bigger;After thesubstitution of Mg2+and Ta5+, the CMTa need a longer pre-treatment time. with theincrease of thickness, micro morphology turn to be more dense and the RMS begin todecrease. With the increase of thickness, the negative effects of dead layer areweakened.. With the increase of pre-treatment times, many small grains begin to growand the proportion of grains boundary begin to increase,at the same time stress beginto increase; many defects are gathered around the grains boundary, as a result the lossbegin to grow. With the increase of pre-treatment times, the grains continual to grow, and he proportion of grains boundary begin to decrease; the stress begin to decrease,and the loss begin to decrease. The stress reflect the concentration of defects, anddecide the loss of CMTa thin films. In conclusin, dielectric loss and stress show thesame rule.In order to study the effects of first layer on CMTa-CT hetero thin films, twodifferent first layer with the single heterogeneous interface of CMTa-CT heterostructure thin films were fabricated. As CMTa have a bigger lattice parameters, thehetero interface exist tensile stress,as a result CT/CMTa show a smooth and densemicro morphology.Receding the inter diffusion between thin films and bottomelectrode and improving the contace between thin films and electrod can improve thedielectric properties.Then, different number of interfaces of CMTa/CT hetero thinfilms are fabricated. The effects of interfaces are studied in details. There exsit twokinds of interfaces: the heterogeneous interface and the dead layers, which willcontribute to dielectric properties at different extent. The results show that, twophases can exist indepedengly and the lattice mismatch can weaken the storage effectof RMS. With the increase of interfaces, dielectric constant continual to grow anddielectric loss continual to decrease. The defects usually gather around the heterointerface with big amount of free electrons and ions.Under the applied eletric field,those charged particles will show the elastic displacement, as a result a highpolarizability layer were formed. The electric field in the interface show the samedirection with the applied electric field, so the interface play a role in the dielectricenhancement.