Optimized design and process for making a DC voltage reference based on MEMS
A micromechanical moving plate capacitor has been designed and fabricated for use as a dc voltage reference. The reference is based on the characteristic pull-in property of a capacitive microelectromechanical system (MEMS) component. The design is optimized for stability. A new silicon-on-insulator (SOI) process has been developed to manufacture the component. We also report on improved feedback electronics and the latest measurement results.
On-chip electrometer using MEMS parallel-plate pull-in sensing
Microelectromechanical Systems (MEMS) have been proposed as DC electrical metrology references. The design reported here is the first to enhance the qualities of a MEMS DC reference with potential tuning and sensing via an isolated and monolithically integrated MEMS technology and thereby, convert a stable parallel-plate voltage reference to a simple, sensitive, low-burden voltage sensor. This on-chip system reliably measures unknown potentials ranging from −60 to 60V with sampling times less than 10 ms. In the initial design, the system is used to measure atto-amp leakage current though 10 PΩ, suspended, MEMS isolation.
Effect of Temperature on Mechanical Properties of Polysilicon
Test techniques and procedures have been developed to measure the tensile stress-strain curves of thin-film polysilicon over the temperature range of 0°–250°C. These are described, and the variations in Young’s modulus, Poisson’s ratio, and strength of this brittle material are presented along with measurements of the coefficient of thermal expansion. Young’s modulus decreases ∼10 percent over the temperature range, while Poisson’s ratio remains unchanged. There is no significant change in fracture strength with temperature. Initial measurements of the coefficient of thermal expansion are higher than handbook values for bulk silicon.