Design and fabrication of a 20 MHz pn-diode silicon ring resonator with in-plane vibration mode

Abstract

In this paper, we report a new microelectromechanical system (MEMS) resonator based on the pn-diode principle. The pn-diode-based resonator can eliminate the narrow gap that conventional electrostatic MEMS resonators need between driving electrodes. This is expected to solve several serious problems related to fabrication, packaging, and lifetime. However, the resonators previously reported had pn-diodes formed in the vertical direction. Because the resonant frequency is determined by the thickness of the resonator plate, the resonant frequency in formed resonators cannot be changed in the same chip. To solve this problem, we newly design a pn-diode resonator with a lateral vibration. Because the resonant frequency is determined by plate width, this new resonator can provide various resonators with different frequencies in a chip, which is most suitable for the integration of MEMS resonators with electronic circuits. Our research objective at present is related to design and fabrication. By using a simulator, we design a ring resonator of 20 MHz. In the fabrication, we develop a technique of using ion implantation to form a 3-µm-thick pn-diode. The results shown here are very useful for improving the MEMS resonators.