Research On High Overload Silicon-based MEMS Capacitors

Focusing on the urgent need of high-performance energy storage device for fuse system,the MEMS capacitor with anti-high overload, high hematocrit value, small size and low firingvoltage was mainly researched. Theoretical foundation and technical support of design andapplication for fuse firing capacitor were established.In this paper, the mechanical properties of MEMS capacitor was simulated by usingANYSYS software, and the simulation results confirmed the reliability of the high aspectration deep trench structure. The etching process was simulated to determine the feasibility ofdry etching through TCAD simulation software. High aspect ratio deep trench structure wasfabricated by photolithography, developing, stripping, deep reactive ion etching (DRIE) and aseries of MEMS process. The verticality and roughness of the deep trench were analyzed. Theverticality of the deep trench has been improved significantly by adjusting theetch/passivation period from the original5/3s to5/4s and the roughness of the deep trenchsidewalls surface has deceased through several alternating cycles of dry oxidation-corrosion-dry oxidation-corrosion. The functional film layers of MEMS MIM capacitor weredeposited through atomic layer deposition techniques. The upper and lower electrodes bothwere TiN(10nm)+W (100nm), and the dielectric layer was Al2O355nm (or35nm). Theelectrical characteristics of the MEMS MIM capacitor was tested, and the results showed thatwhen the Al2O3dielectric thickness was55nm, the breakdown voltage of the capacitorreached32.5V; when the Al2O3dielectric thickness was35nm, the average breakdownvoltage reached26V, showing a good resistance characteristic to high voltage. The leakagecurrent was in the microampere or less in both cases, and the average capacitance of singleMEMS MIM capacitor was4.88×10-6F. The functional film layers of MEMS MOS capacitorwere fabricated by using atomic layer deposition techniques. The upper and lower electrodeswere TiN(10nm)+W (350nm) and P++(100) highly doped Si,respectively. The electrical characteristics of the MEMS MIM capacitor was tested. The accumulation zone capacityfor different samples of the MOS capacitor were30μF~65μF, while the inversion regionhaving a capacitance of25μF~50μF. The leakage current of the MOS capacitor was up to8μA. The capacitance fuze firing circuit diagram was designed. The thick film ignition circuitand PCB ignition circuit prototype were completed. The reliability of the firing circuit boardswere tested through freedom Hopkinson Bar and air guns. The results showed that thedesigned ignition circuit prototypes were intact at56000g shock. The temperatureperformance were tested by using high and low temperature impact test chamber andTemperature Controller. The results showed that the circuit boards had no failure occurs andmaintained excellent ignition detonation ability.