Sensor fabrication chemical vapor deposition

Other techniques have been used for the fabrication of thin-film metal-oxide gas sensors. At NIST in the USA, Cavicchi et al. (1995) and Semancik et al. (2001) produced gas sensors by chemical vapor deposition (CVD). By applying a current and thus heating the hotplate, sensing films could be deposited locally (i.e. only on heated active areas) using an adequate organ-ometaUic precursor. SnOj and ZnO films were obtained with tetramethyltin and diethylzinc in an oxygen atmosphere. They were deposited onto different seed layers, which played a significant role in terms of gas selectivity. 

MEMS (microelectromechanical systems) are systems with small device sizes of 1-100 pm. They are typically driven by electrical signals. To fabricate such systems materials like semiconductors, metals, and polymers are commonly used. MEMS technology fabrication is very cost-efficient. The structures are transferred by processes, which are applied to many systems on one substrate or even many of them simultaneously. The most important fabrication processes are physical vapor deposition (PVD), chemical vapor deposition (CVD), lithography, wet chemical etching, and dry etching. Typical examples for MEMS are pressure, acceleration, and gyro sensors [28,29], DLPs [30], ink jets [31], compasses [32], and also (bio)medical devices. 

Liu, Y. Koep, E. Liu, M., A highly sensitive and fast-responding Sn02 sensor fabricated by combustion chemical vapor deposition, Chem. Mater. 2005,17, 3997-4000... 

Microfabrication has been the topic of a recent review in which thin-film (<1 pm, based on vacuum evaporation, sputtering or chemical vapor deposition) and thick-film (>10pm, based on screen printing or lamination) technologies are described for the mass production of potentiometric sensors and sensor arrays [80]. Current challenges include the cost of fabrication, especially for thin-film devices, the control of physical dimensions of the sensing elements, the incorporation of liquid reservoirs, and the stability of the integrated reference electrodes. 

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