Frequency compensated oscillator design for process tolerances

Abstract

A continuous or distributed resonator geometry is defined such that the fabrication process used to form a spring mechanism also forms an effective mass of the resonator structure. Proportional design of the spring mechanism and/or mass element geometries in relation to the fabrication process allows for compensation of process-tolerance-induced fabrication variances. As a result, a resonator having increased frequency accuracy is achieved.

Description

BACKGROUND The present invention relates generally to the design and fabrication of resonators. Resonators formed in accordance with the present invention find application, for example, within oscillators. Within the field of micro-electro-mechanical systems (MEMS), oscillators are critical components. The functionality of many micro-mechanical structures, including oscillators, is based on the reaction (e.g., oscillation, deflection, or torsion) of a spring mechanism to an applied force. Such “spring mechanisms” are typically formed from one or more beam structures having, or modeled to have, a rectangular cross section of predetermined width. The physical structure of a spring mechanism is typically formed using a sequence of planar or surface micro-machining fabrication processes. The degree to which a spring mechanism actually takes the form intended by its design is a function of the precision with which the one or more fabrication processes are applied to a layer or segment o...

AI Technical Summary

Benefits of technology

The present invention provides a resonator structure having increased immunity to process-tolerance-induced variations in geometry. That is, resonators designed and formed in accordance with the present invention may be produced with greater manufacturing yield since the ratio of effective spring stiffness to effective mass of the resonator is well maintained in relation to the fabrication process forming the resonator.

Problems solved by technology

However, MEMS components are so small and their functionality so demanding that even relatively minor variations from specification will adversely influence performance.

Process-tolerance-induced variations can result in spring mechanisms having actual widths that differ greatly from their intended design.

Since a spring mechanism's width defines its stiffness, and since the ratio of resonator stiffness to resonator mass defines a resonator's frequency response to an external stimulus, significant variations in spring width are unacceptable.

However, trimming for silicon based resonators is not a fabrication solution readily adapted to the reliable mass manufacture of resonator components.

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