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IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 54, NO. 11, NOVEMBER 2007 3071 A Low-Power Robust Humidity Sensor in a
 

Summary: IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 54, NO. 11, NOVEMBER 2007 3071
A Low-Power Robust Humidity Sensor in a
Standard CMOS Process
Burak Okcan and Tayfun Akin, Member, IEEE
Abstract--This paper presents a low-cost thermal-conductivity-
based humidity sensor implemented using a 0.6-Ám CMOS
process, where suspended p-n junction diodes are used as the
humidity-sensitive elements. The measurement method uses the
difference between the thermal conductivities of air and water
vapor at high temperatures by comparing the output voltages of
two heated and thermally isolated diodes; one of which is ex-
posed to the environment and has a humidity-dependent thermal
conductance, while the other is sealed and has a fixed thermal
conductance. Thermal isolation is obtained by a simple front-end
bulk silicon etching process in a TMAH solution, while the diodes
are protected by the electrochemical etch-stop technique. The sus-
pended diodes are connected to an on-chip circuit using polysilicon
interconnect layers in order to increase their thermal resistance to
be able to heat them with less power. Due to the high electrical
resistance and positive temperature coefficient of resistance of the

  

Source: Akin, Tayfun - Department of Electrical and Electronics Engineering, Middle East Technical University

 

Collections: Engineering