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Passivation and corrosion of microelectrode arrays
Author(s) -
Schmitt G.,
Faßbender F.,
Lüth H.,
Schöning M. J.,
Schultze J.W.,
Buß G.
Publication year - 2000
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/(sici)1521-4176(200001)51:1<20::aid-maco20>3.0.co;2-q
Subject(s) - passivation , materials science , corrosion , plasma enhanced chemical vapor deposition , silicon , layer (electronics) , blisters , monolayer , composite material , microstructure , optoelectronics , nanotechnology
The application of silicon based microsensors in aqueous environments is hindered by unsatisfactory barrier properties and poor corrosion resistance of common passivation layers which give insufficient protection to electronic microstructures. This paper reports on investigations of the protective effect of various types of layers (compatible to silicon planar technology) against 1 M NaCl at pH 2 to 10. Failures of the passivation layers were detected by leak current and conductivity measurements with subsequent investigations of failure mechanisms by scanning electron microscopy (SEM). Both organic and inorganic films were tested with chips which were completely covered with the passivation layer. Organic films had a time to failure of at best 500 h, achieved by Probimer® and plasma treated polyimide. The poor barrier properties of PECVD‐SiO 2 and Si 3 N 4 monolayers (only a few hours) were clearly surpassed by combining the monolayers to SiO 2 / Si 3 N 4 ‐ duplex and SiO 2 / Si 3 N 4 / SiO 2 triplex (ONO) layers. The most promising barrier properties were achieved by the triplex (ONO) layer which yielded a time to failure of 1200 h compared to 500 h for the duplex layer on non‐buried conducting tracks. Burying the conducting tracks into the thermal SiO 2 layer significantly improved the performance of the duplex (2000 h) and the SiC layer (1000 h compared to 700 h on non‐buried tracks) once again. In the case of open electrodes the Si 3 N 4 layer quickly failed, whereas the duplex and the SiC layer revealed better protective properties. Organic films failed due to swelling and the formation of blisters. Intrinsic mechanical stress with chemical interaction resulted in stress corrosion cracking (SCC) and finally lead to the failure of the inorganic PECVD layers.