CMOS integrated gas sensor chip using SAW technology
ABSTRACT The development of inexpensive and miniaturized SAW gas sensors that are highly selective and sensitive is introduced. These sensors are implemented with micro-electro-mechanical systems (MEMS) in CMOS technology. Since the sensors are fabricated on a silicon substrate, additional signal processing circuitry can easily be integrated into the chip thereby readily providing functions such as multiplexing and analog-to-digital conversion that are needed for integration into a network.
Conference Proceeding: Transient heating study of microhotplates by using a high-speed thermal imaging system[show abstract] [hide abstract]
ABSTRACT: A high-speed thermal imaging system is used to investigate the dynamic thermal behavior of MEMS (microelectromechanical systems) based microhotplate devices. These devices are suspended microstructures fabricated in CMOS technology and are used in various sensor applications. Measurements reveal delayed surface heating of the microhotplate and temperature redistribution during both the heating and cooling phases. Reflected infrared (IR) radiation from the hidden backside of the heater is used with a normalization technique to determine peak heater temperature. The measurements are shown to be useful in optimizing the design of microhotplate structures. It is found that the use of a heat-spreading layer improves the local temperature uniformity between the heater strips. It is also found that the use of the thinner layers of the 1.5 μm CMOS technology improve the global temperature uniformity over the top surface of the microhotplateSemiconductor Thermal Measurement and Management, 2002. Eighteenth Annual IEEE Symposium; 02/2002
Conference Proceeding: Laminated high-aspect-ratio microstructures in a conventional CMOSprocess[show abstract] [hide abstract]
ABSTRACT: Electrostatically actuated microstructures with high-aspect-ratio laminated-beam suspensions have been fabricated using conventional CMOS processing followed by a sequence of maskless dry-etching steps. Laminated structures are etched out of the CMOS silicon oxide, silicon nitride, and aluminum layers. The key to the process is use of the CMOS metallization as an etch-resistant mask to define the microstructures. A minimum beam width and gap of 1.2 μm and maximum beam thickness of 4.8 μm are fabricated in a 0.8 μm 3-metal CMOS process available through MOSIS. Structural features will scale in size as the CMOS technology improves. An effective Young's modulus of 63 GPa is extracted from resonant frequency measurements. Cantilevered structures slightly curl up with a radius of curvature of about 4.2 mm. Multi-conductor electrostatic micromechanisms, such as self-actuating springs and nested comb-drive lateral resonators, are successfully produced. Self-actuating springs are self-aligned multi-conductor electrostatic microactuators that are insensitive to curl. The resonance amplitude is 1 μm for an 107 μm-wide×109 μm-long spring with an applied 11 V ac signal. Finite-element simulation using the extracted value for Young's modulus predicts the resonant frequency of the springs to within 6% of the measured valuesMicro Electro Mechanical Systems, 1996, MEMS '96, Proceedings. 'An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems'. IEEE, The Ninth Annual International Workshop on; 03/1996
- [show abstract] [hide abstract]
ABSTRACT: A major limitation in the fabrication of microstructures as a postCMOS (complimentary metal oxide semiconductor) process has been overcome by the development of a hybrid processing technique, which combines both an isotropic and anisotropic etch step. Using this hybrid technique, microelectromechanical structures with sizes ranging from 0.05 to ~1 mm in width and up to 6 mm in length were fabricated in CMOS technology. The mechanical robustness of the microstructures determines the limit on their dimensions. Examples of an application of this hybrid technique to produce microwave coplanar transmission lines are presented. The performance of the micromachined microwave coplanar waveguides meets the design specifications of low loss, high phase velocity, and 50 Ω characteristic impedance. Various commonly used etchants were investigated for topside maskless postmicromachining of 〈100〉 silicon wafers to obtain the microstructures. The isotropic etchant used is gas-phase xenon difluoride (XeF<sub>2</sub>), while the wet anisotropic etchants are either ethylenediamine-pyrocatechol (EDP) or tetramethylammonium hydroxide (TMAH). The advantages and disadvantages of these etchants with respect to selectivity, reproducibility, handling, and process compatibility are also describedJournal of Microelectromechanical Systems 01/1998; · 2.13 Impact Factor