The Preparation And Electrical Properties Of MEMS Electrostatic Supercapacitors Based On High Dielectric Constant Film

MEMS supercapacitors are the advanced areas of energy storage,playing an increasingly important role in the development of MEMS sensors,medical and transportation.According to the different of working principle,MEMS supercapacitors can be divided into electrochemical supercapacitors and electrostatic supercapacitors.Electrochemical supercapacitors have the advantages of high energy density and long cycle life.However,compared to electrochemical supercapacitors,electrostatic supercapacitors have higher power density and reliability,but the energy density is low.In order to solve this problem,we can study from two aspects:（1）increase the specific surface area of the electrode;（2）improve the dielectric constant of the dielectric.This topic was studied in this paper from the above two aspects,and designed the technology of MEMS electrostatic supercapacitors.The main contents of this paper include the following three parts:1.In order to increase the electrode specific surface area of the MEMS electrostatic supercapacitors,a three-dimensional groove array was prepared on the silicon substrate by wet etching and dry etching.For the wet etching,theinfluence of the mask size and the ratio of the etching solution on the etching morphology was studied in this paper,the optimum process parameters were designed and the morphology of grooves were characterized by scanning electron microscopy（SEM）.Finally the specific surface of the best groove array is increased about 76.9%.For the dry etching,the morphology and reliability of etched surface was characterized by SEM,and the perpendicularity and roughness of grooves sidewalls under different mask size were analyzed,end up with the surface area of the groove array increasing up to 14 times approximately.2.In this paper,the high dielectric-constant CaCu₃Ti₄O₁₂（CCTO）film has been investigated to the MEMS electrostatic supercapacitors to improve its energy density.In the experiments,CCTO films were firstly synthesized under different sintering temperature（700℃,800℃,900℃）through a sol-gel method on silicon substrate.The morphology,phase identification and crystalline of CCTO films were respectively characterized with emission scanning electron microscope（SEM）,X-ray diffraction（XRD）and energy disperse spectroscopy（EDS）.It is found that the CCTO film has the best quality at the sintering temperature of 800℃.Then,the current-voltage（I-V）and capacitance-voltage（C-V）measurements of the CCTO films has been performed on a metal-insulators-semiconductor capacitor structure,the value of largest threshold voltage and energy density are found to be 47 V and 3.2J /cm³.Meanwhile,the phenomenon of dielectric charging in the highdielectric-constant CCTO films has been observed and investigated firstly,and the influence of dielectric charging on the performance of electrostatic supercapacitors have been also analyzed.3.The preparation process of MEMS electrostatic supercapacitors was designed.The electrode preparation,dielectric preparation,reliability and other aspects were discussed respectively.A method for preparing dielectric thin films by anodic oxidation was proposed,meanwhile preliminary experiments and analysis of electrical characteristics were conducted.Optimization and validation of experiment for enhancing the performance of capacitors will be conducted next.