Research On Process Optimization And Electrical Properties Of Silicon-based MEMS Capacitors With High Aspect Ratio

As the demand of portable electronics is increasing, more requirements have been putforward to the electronic devices, in terms of volume, sensitivity, energy consumption andintegration, etc., energy supply has been an important technical bottleneck limiting theminiaturization of devices. With the development of “miniaturization, integration andintelligence for power supply”, MEMS capacitors, which have wider operating temperaturerange, lower power dissipation, lower noise, long life, higher energy density andinstantaneous power than conventional ones, are attracting the attention of researchers athome and abroad. In this paper, research on MEMS capacitors with large surface area, highcapacity and reliability based on MEMS technology has been launched, which could lay afoundation for the future design and application of micro-energy system.In my work, the relationship between capacity and puncture voltage of MEMS capacitorswere systematically analyzed, mask structure and fabrication process were also optimized.Furthermore, ANSYS was used to analyze the stress on the5μm×15μm×150μm trenchesto ensure the design was reasonable. In this thesis, Through Silicon Via （TSV） and AtomicLayer Deposition （ALD） were used to improve the surface area of MEMS capacitor; Thereality of MEMS capacitors was improved by micro-pore filling process of deep trenches;Finally, MEMS capacitors with large capacity volume ratio, high reliability and strongenvironmental adaptability were successfully fabricated by PCB package. In addition, theimpact of manufacturing technology on the structure and property of MEMS capacitors wasinvestigated. Semiconductor parameter measurement system was utilized to test thebreakdown characteristic of HfO₂dielectric layer. Also, the impedance, C-V, I-V, and C-f ofMEMS capacitors were tested. Then, temperature adaptability of MEMS capacitors was tested by HP4284A coupled with a temperature console.In this paper, the single5μm×15μm structure was designed to solve the loading effectcaused by large duty cycle during the etching process. ANSYS simulation results showed thatthe deep trenches could satisfy the requirements of MEMS capacitors. Then, the etchingverticality of highly conductive silicon with different doping elements was analyzed, andhighly conductive silicon doped with B exhibited excellent etching results and high verticality.The effect of metal filling on trench was investigated, and the results were not ideal, due tothe inherent limits of sputtering process and low mass of aluminum. Afterwards, differentmetal materials were chosen as the electrodes of MEMS capacitors to discuss the property,and W deposited by ALD indicated outstanding stable performance. Furthermore, thebreakdown characteristic of HfO₂dielectric layer was tested. The results showed that thebreakdown field strength of HfO₂dielectric layer is （3.9⁴.5） MV/cm, the leakage currentof that is nA; And the leakage current and breakdown field strength of dielectric layerdecreased with the increasing thickness. Next, the C-V measurements of MEMS capacitorswas analyzed and the results indicated that the energy densities of MEMS capacitors werebetween （0.56⁰.88） μF/mm³, and the capacitors displayed typical MOS characteristic. TheC-f characteristic of MEMS capacitors was tested at0¹MHz, and the capacity reduced asthe frequency increased. Finally, the MEMS capacitors showed understanding temperatureresponse characteristics within a temperature range of （20⁶5）℃.