ISFET Microsensors HfO2 Based for Biomedical Applications

The sensor presented in the paper is based on ion selective field effect transistors to detect chemical quantities from biological media (Arshak Poghossian, 2004). The micromachining techniques used for realisation of the chemical sensors dedicated to pH, Na⁺, K ⁺, H⁺ detection using silicon micromachined transducers and sensitive layers as HfO₂ are presented. The silicon transducers are realised by micromachining techniques (both surface and bulk) and the sensitive layer (in the area of nm thickness) is deposited on top of the wafers allowing the sensors HfO₂ based realisation. HfO₂ is a material characterised by high dielectric constant and its characteristics in terms of gate material for ISFET sensors are presented. The electrical and functional characterisation of sensors are presented. The major achievements of the work are: manufacturing a CMOS compatible ISFET based on chemical sensitive layers for biological and medical applications; integration of the ISFET sensors on the tip of a microprobe that can be used for measurements of different chemical species (pH, Na⁺, K⁺ , H⁺) in vivo and in vitro and the development of a new sensing material (HfO₂2); compatibility of all technological process with CMOS technologies and development of new packaging methods