PASiC Ammonia Sensor Design

Abstract

Capacitive, interdigital sensors in proximity of a PASiC thin film have been proposed as a cheap, robust alternative to existing ammonia sensing technologies. However, although prototype sensors have been manufactured, investigation into the working principles of this class of ammonia sensors is limited. This work aims to analyse the electrode and PASiC layer configuration to gain more insight into how design parameters influence the sensing capabilities of these devices.
To this end, finite element simulations and analytical simulations have been carried out to model the behaviour of the sensor configuration. The PASiC layer is modelled as a stack of layers with different permittivities, with the response to ammonia modelled as a change in the permittivity of the layers.
Using the simulation data, a lithography mask for a test-bench with varying electrode dimensions is designed to allow fabrication of devices for measuring the effects of different manufacturing parameters.
A series of prototypes created using this mask is then used to devise an etching setup to allow electrochemical etching of single chips to create the porous layer.
The results of the manufacturing process are analysed and discussed.