Single-chip systems

The central topic of the book was the integration of microhotplate-based metal-oxide gas sensors with the associated circuitry to arrive at single-chip systems. Innovative microhotplate designs, dedicated post-CMOS micromachining steps, and novel system architectures have been developed to reach this goal. The book includes a multitude of building blocks for an application-specific sensor system design based on a modular approach. 

Kikutani, Y., Hisamoto, H., Tokeshi, M., Kitamori, T, Fabrication of a glass microchip with three-dimensional channel network and its application to a single-chip combinatorial synthetic reactor, in Ramsey, J. M., VAN den Berg, A. (Eds.), Micro Total Analysis Systems, pp. 161-162, Kluwer Academic Publishers, Dordrecht (2001). 

In a monolithic system, electronics and sensor part are integrated on a single chip. Separate circuitry and microsensor chips are characteristic for hybrid systems, as it is indicated by the dashed separation line in Fig. 2.1. The advantages and issues with hybrid and monolithic systems are extensively discussed in literature [14], so that only a few key points are mentioned here. The main disadvantage of monolithic systems is the limitation with respect to available materials and microtechnological process... 

The limit for the operating temperature of CMOS-microhotplates can be extended by using the microhotplate that was presented in Sect. 4.3. We now detail high-temperature microhotplates with Pt-resistors that have been realized as a single-chip device with integrated circuitry. While the aluminum-based devices presented in Sect. 4.1 were limited to 350 °C, these improved microhotplates can be heated to temperatures up to 500 °C. As the typical resistance value of the Pt-resistor is between 50 and 100 Q, a chip architecture adapted to the low temperature sensor resistance was developed. The system performance was assessed, and chemical measurements have been performed that demonstrate the full functionality of the chip. 

D. Barrettino, M. Graf, M. Zimmermann, A. Hierlemann, and H. Baltes. A Smart Single-chip Microhotplate-based Chemical Sensor System in CMOS Technology , Proc. IEEE International Symposium on Circuits and Systems (ISCAS), Phoenix, AZ, USA (2002) Vol. 2, 157-160. 

Conventional single-chip packages have limited packing density on printed wiring boards (PWBs) and limit the system speed due to the large delay time for signals propagated between chips. 

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