Thermoelectric infrared sensors in CMOS technology

Thermal CMOS Sensors―an Overview

“…Such microstructures include CMOS polysilicon or aluminum layers sandwiched between the CMOS dielectric layers, ie, the thermal silicon dioxide, the silicon dioxides produced by chemical vapor deposition (CVD), and the silicon dioxide-nitride passivation. The preferred etchant is EDP (ethylenediamine pyrocatechol) optimized with respect to the removal of substrate silicon while conserving the passivation and the metal pads of the CMOS process [5,6]. By design, the passivation layer serves as an etching mask and no further mask is required.…”

“…By design, the passivation layer serves as an etching mask and no further mask is required. Dielectric beams supporting thermal sensor elements [5,6], circuits [7], or radiation sources [8] are made in this way. Alternative etchants based on QAH (quaternary ammonium hydroxides) are currently being investigated [9].…”

“…The front of the wafer is protected from KOH by a mechanical cover. Industrial production of membrane-type sensors based on a CMOS 1C process with 150 mm wafers has been demonstrated recently [6,9]. A photograph of such a wafer with dielectric membranes supporting infrared sensors and thermal converters, after completion of the post-processing etching step, is shown in Figure 3-1.…”

“…CMOS infrared sensors on a closed oxide-nitride membrane optimized for an intrusion alarm system have been demonstrated recently [6,9]. Figure 3-4 shows their schematic structure with an absorption area consisting of the silicon oxide-nitride passivation on top of an aluminum mirror on top of the CVD and thermal oxide layers.…”

Progress in Microsensor Interfaces

“…Unfortunately, they are not compatible with standard 1C technologies. By contrast, thermoelectric infrared sensors can be made CMOS compatible [5] and, therefore, can be batch fabricated and co-integrated with the analog interface on the same chip. However, since they are less sensitive, they require more demanding specifications for the circuitry.…”