A resonator is a device that is indispensable in modern electronics products such as computers, digital appliances and telecommunications devices. Currently, resonators that use quartz crystals are mainly used due to their light weight as well as highly precise and stable frequency properties. Research for new silicon based resonators shows that further miniaturization and reduction in cost may be possible through the use of MEMS processes to fabricate with silicon material.
High temperature dependency of the resonant frequency of silicon-based resonators poses a major challenge. More specifically, due to factors like thermal expansion and Young's modulus temperature dependence, its resonant frequency fluctuates when there is a change in temperature and generally has a temperature coefficient of - 40ppm/°C. This means that for its operating temperature limit (-40°C~80°C), the resonant frequency will fluctuate in the 5000ppm range, making it very difficult to ensure precise output frequency in the resonator.
In order to ensure precise output frequency, an electrical circuit has to be used to compensate for the change in resonant frequency as a result of temperature fluctuations. This creates a problem in the design for low power consumption and miniaturization. Furthermore, the use of the electrical circuit to substantially compensate for temperature fluctuations also leads to the occurrence of noise in the output.
Now, Seiko Instruments is claiming to have successfully developed manufacturing technology that can improve the problem of temperature dependence of the resonant frequency in silicon based MEMS resonators by adding a layer of silicon dioxide film to the MEMS resonator fabricated on the SOI (silicon on insulator) substrate, and employing a structure that would produce residual stress within the resonator.
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