Patent DE 10 2024 130 098

ISFETs are ion-sensitive sensors that can be manufactured in CMOS using standard MOSFETs. pH-sensitive CMOS ISFETs with specific H⁺ ion-sensitive layers require additional process steps outside the standard CMOS process flows, which are usually complex and expensive. CMOS ISFETs in standard or unmodified CMOS processes, on the other hand, can be produced cost-effectively and are compatible with mass production, making them accessible for a large number of different applications.

According to the current state of the art, the ion-sensitive layer of CMOS ISFETs consists of stacked oxide and nitride passivation layers. However, the sensitivity and signal resolution of these known CMOS ISFETs may be too low for some applications, and the hydration of the silicon nitride layer may lead to drifts and reduce the lifetime of the ISFET.

The idea of the invention is to add an "anti-reflective coating (ARC)" layer at the interface to a medium under test. The deposition of this layer is part of the standard CMOS process, in particular of our partner X-FAB, and is therefore cost-effective. By adding the ARC layer, the performance of a CMOS ISFET sensor can be significantly improved in terms of sensitivity, resolution and drift.