Packaged CMOS?MEMS free?free beam oscillator

In this paper a self-oscillator based on a polysilicon free?free beam resonator monolithically integrated and packaged in a 0.35??m complementary metal?oxide?semiconductor (CMOS) technology is presented. The oscillator is capable of providing a 350?mVPP?sinusoidal signal at 25.6?MHz, with a bias polarization voltage of 7?V. The microelectromechanical systems (MEMS) resonator is packaged using only the back-end-of-line metal layers of the CMOS technology, providing a complete low-cost CMOS?MEMS processing for on-chip frequency references.