Integrated MEMS Microsensors

Abstract

Many Micro-Electro-Mechanical Systems (MEMS) products have been commercialized at a fraction of the cost and size of conventional devices. Low cost, small sizes and multi-function are the ultimate objectives of commodity MEMS devices. An intelligent micro-system requires that the processing circuitry, sensors, and actuators be integrated on the same chip. Integrated MEMS can improve performance of the overall product in several applications. In this work integrated MEMS devices are investigated through semiconducting Yttrium Barium Copper Oxide (YBaCuO) microbolometer arrays on complementary metal oxide semiconductor (CMOS) substrates, a novel tunable infrared microspectrometer, and a novel device-level packaging technique for MEMS resonators. YBaCuO microbolometers are integrated with CMOS readout circuits using CTIA (Capacitive Transimpedance Amplifier) design technique in AMI 1.5µm double-poly-double-metal n-well 2.5V CMOS technology. The thermal isolation of the self-supporting micromachined YBaCuO microbolometers is varied by designing two different electrode arm geometries. The first geometry is designed to obtain a relatively fast 200 Hz frame rate while maintaining moderate detectivity. The second arm geometry is designed to achieve a traditional 30 Hz frame rate with high detectivity microbolometers. The design of a novel tunable, microspectrometer, based upon Bragg diffraction grating structure, capable of operating in the infrared region (1 µm to 10 µm) of the optical spectrum is also presented. The tunability of the microspectrometer is achieved by changing the position of the perfect conductor placed below the dielectric waveguide grating structure. Many MEMS devices require expensive vacuum packaging. MEMS resonator is one example where the Q-factor of the resonator depends upon the pressure of the vacuum; such a device, therefore, serves as a good test-bed for "growing your own package". At present, the packaging cost of these MEMS resonators is 70-80% of the total cost of the final MEMS product. A ground-breaking device-level packaging technique for these MEMS resonators that would satisfy all the standards set by International Technology Roadmap for Semiconductors (ITRS) 2005 and cut down the cost of the overall MEMS product drastically has also been presented.