Research On The Fabrication Of High-k Dielectric Films And The Discussion Of Integrated Thin Film Capacitor

With the rapid development of wireless communication,the advancement of electronic devices is heading more and more in the directions of miniaturization, thin-film based and integration,against this background,thin-film capacitors have attracted widespread interest in the scientific and technological circles.The research in this thesis is thin-film capacitors related,and it is performed in this two fields:a.research of High-k dielectric films for MOS gate dielectric applications;b. research of integrated thin films capacitors based on MIM structure and coplanar electrodes structure.The first part of this thesis focus on the deposition of SiO_xN_y,TiO₂ dielectric films.The influences of sputtering technologies on the films' composition and structures are studied,and the films' electrical properties are analyzed with the background of MOS gate dielectric applications.The main results of first part are listed as follows:1.Reactive sputtering of SiO_xN_y films in the O₂/N₂/Ar mixed atmosphere was studied.By studying the theoretical model for double reactive gases sputtering process,the influences of reactive gases supply on the sputtering rates and films' compositions are characterized.According to the condition of sputtering system, the final selected sputtering atmosphere for SiO_xN_y is the mixture of a fixed N₂ flow of 1sccm and an Ar flow of 9.5 sccm,while a variable O₂ flow is used for the control of films' composition.The average sputtering rate was 15nm/min,which is a leading level comparing to other reports.Furthermore,the dielectric constant of the deposited SiO_xN_y can be effectively controlled between 4.3～6.7 and the ratio of oxygen atoms can be controlled between 0.3～0.8,suggesting a trade-off between deposition rate and films composition control has been attained.2.Systematic studies have been made as to the influences of fabrication conditions on the structures of TiO₂ films.Substrate temperature influences the films' structure through affecting nucleation sites energies.It is showed that the TiO₂ films can easily transform from the anatase structure into the more stable ruffle phase with the increase of substrate temperature.Sputtering pressures and power influence the films' structure through affecting the substrate bombardment energy during deposition.The increase of bombardment energy can also lead to increased proportion of ruffle phase.But the influence of bombardment energy seems to be nonlinear.After the sputtering power or pressure was increased to an excessive value,the growth of ruffle phase will become suppressed.The influence of annealing was also studied.Both the investigation as to the sputtering and annealing conditions suggested that with the promotion of rutile growth,a higher dielectric constant can be expected.And the adopted fabrication conditions have effectively controlled the dielectric constant between 30～80.3.The electrical properties of TiO₂,TiO₂/SiO₂,TiO₂/SiO_xN_y dielectric films are comparatively studied with the background of MOS gate dielectric applications. Compared to TiO2,TiO₂/SiO₂ and TiO₂/SiO_xN_y exhibit 50%and 70%lower leakage current,and the gate dielectric charges related offsets have been reduced by larger than 1V,suggesting the effects of SiO₂,SiO_xN_y interfacial layer for the improvement of electrical properties.Furthermore,SiO_xN_y interfacial layer can lead to lower dielectric charge density than SiO₂ does(the offset is reduced by about 0.2 V),and 17%higher capacitor value at accumulation state.But the SiO₂ layer is better as to the interfacial electrical properties.These differences may have been resulted from the different diffusion extents of TiO₂.The presence of nitrogen component in SiO_xN_y film can effectively restrain the diffusion of TiO₂.As a result, the corresponding dielectric charges density is lower.But the nitrogen related over-constrained state at the interface also resulted in the lower interfacial electrical properties.This difference can also affect the mechanism of leakage current in the dielectric films.The mechanism in TiO₂/SiO₂ lean towards the bulk defect states related Poole-Frankel mechanism,while the mechanism in TiO₂/SiO_xN_y lean towards the interfacial defect states related Schottkey Emission mechanism.On the whole,TiO₂/SiO_xN_y structure dielectric films have exhibit better combination properties and encouraging prospect for future development. This systematic study is important for the dissemination of TiO₂ dielectric films application.The second part of this thesis studied the integrated thin film capacitor based on MIM structure and coplanar electrodes structure,the corresponding results are listed as follows.1.MIM Structure integrated thin film capacitors were fabricated on the ceramic substrate and the influences of post deposition annealing and bias voltage sputtering on the capacitor property were studied.Post deposition annealing can reduce the voids,defects and un-continual states resulted from the coarse substrate and the deposition technologies used.Thereby increase the insulating strength and decrease the conductance related loss factor.But excessive annealing can also destroy the dielectric films and lead to the deterioration of electrical properties. After annealing,the breakdown field of annealed capacitors can be larger than 10⁷v/m,and loss factor at 5MHz is less than 0.01.The Bias-Voltage sputtering can improve the films' compactness via energetic bombardment,thereby enhance the capacitors' properties.But energetic bombardment also increase the density of defects,which then lead to the loss mechanism related with both conductance and dispersive response.Furthermore,excessive bias sputtering can also bring destructive bombardment and re-sputtering on the substrate,which then lead to the deterioration of insulating properties.Bias-voltage sputtering possesses the advantage of real time enhancement.After the enhancement of bias-voltage sputtering,the breakdown field of obtained thin film capacitors reached 10⁷v/m, and loss factor at 5MHz is about 0.015.2.Interdigital capacitors and fractal capacitors are newly developed capacitor structures.Theoretical and Experimental studies are both performed on these capacitors.Conformal mapping based analytical solution was used to study the extrication of static capacitor values.It is showed that the main factor influencing static interdigital capacitor value are the length of interdigital electrode,and the capacitor density will also increase at a larger ratio of electrode width to gap.As to the fractal capacitor,in order to achieve higher capacitor value,concordance between electrode length and the ratio of width to gap is also required; Electromagnetic simulation and decoupling measurements are both adopted to analyze the high-frequency properties of planar capacitors.It is showed that the main factor influencing high-frequency properties is the ratio of width to gap,as the ratio is increased,the electrodes gap will decrease,and a larger inductance parameter will be expected.After all,Fractal structure is beneficial for the improvement of high-frequency properties;Laser technology was adopted to fabricate fractal structure planar capacitors on the 20mm*30mm ceramic substrate, the obtained capacitor value is between 1～7pF,and capacitor like impedance can last to a frequency lager than 2.5GHz,suggesting its good adjustability and high-frequency performance.These results have provided a new technology for the development of high frequency and high Q capacitors.