Encapsulation of ISFET sensor chips

Testing the Honeywell Durafet® for seawater pH applications

“…The previous work with ISFETs in seawater has not addressed long-term drift, possibly because these studies were carried out with metal oxide insulator materials not ideally suited for sea- water media (Bergveld 2003), chip packaging that used resin coatings with limited lifetimes (Oelßner et al 2005), or simply that these studies focused mostly on short-term applications such as single profiles and detection of waters influenced by hydrothermal vents. Here, we explore the use of a Honeywell Durafet ISFET sensor for seawater pH measurements over sustained periods in situ.…”

Chemical and Biological Field‐Effect Sensors for Liquids—A Status Report

“…Early problems with ISFETs, that is, drift, temperature instability, light sensitivity, encapsulation, and packaging, can be considered as satisfactorily solved, at least by leading companies producing pH-ISFET sensors. 25 Today, commercially available ISFET sensors are exceptionally stable (practically drift free), fully temperature compensated, rugged, and reliable, and exhibit performances comparable to those of pH glass electrodes. 25 Moreover, different ISFET fabrication technologies with integrated readout interfaces (e.g., constant current-voltage driver, calibration circuitry, electronics for drift and temperature compensation) have been realized using complementary metal-oxide-semiconductor (CMOS) processes.…”

“…25 Today, commercially available ISFET sensors are exceptionally stable (practically drift free), fully temperature compensated, rugged, and reliable, and exhibit performances comparable to those of pH glass electrodes. 25 Moreover, different ISFET fabrication technologies with integrated readout interfaces (e.g., constant current-voltage driver, calibration circuitry, electronics for drift and temperature compensation) have been realized using complementary metal-oxide-semiconductor (CMOS) processes. 10,26,27 However, to our knowledge, up to now no ISFET with integrated readout interface has been commercialized.…”

“…Therefore, nowadays, in many in-line process-monitoring systems in biotechnology, food, pharmaceutical and cosmetic industries, the breakable pH glass electrode is gradually being replaced by nonglass, unbreakable pH sensors based on ISFETs. 25 However, the main problem with those applications is the required cleaning-in-place (CIP) suitability of ISFET devices. According to Ref.…”

“…Generally, the following basic mechanisms of potential generation can be considered: a pH or ion-concentration change, enzymatic reactions, adsorption of charged macromolecules (e.g., polyelectrolytes, deoxyribonucleic acid (DNA)), affinity binding of molecules (e.g., antigen-antibody affinity reaction, DNA hybridization), and potential changes that are coming from living biological systems as a result of more sophisticated (bio-)chemical processes (e.g., action potentials of nerve cells). [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] However, sometimes these results have been "rediscovered" from results that have already been obtained more than 10-30 years ago. At present, Si 3 N 4 , Al 2 O 3 , and Ta 2 O 5 serve as pH-sensitive gate insulator materials in commercial ISFETs.…”