In the course of increasing automation and digitalization, the demand for sensors for process and environmental monitoring is constantly growing. A particularly strong growth can be observed in gas sensor technology, e.g. for monitoring and control of ventilation systems or in the analysis of process gases. The majority of these gases show characteristic absorption bands in the near and mid infrared range, which is why a large number of sensors are based on the absorption principle.
One way to significantly reduce manufacturing costs is to use miniaturized components and simplified processes for separating the chips from the wafer compound. With the development of a new plasma-assisted etching process, a thin functional membrane as well as a break trench for the later separation of the chips by breaking them out can be created simultaneously. In the course of the miniaturization by more than factor 4 smaller areas compared to the state of the art and the resulting reduction of the thermal mass, the dynamics of the IR emitters also increases by factor 2, which provides further technical advantages in the application in NDIR gas sensors.
Not only the requirements for packaging and interconnection technology of these MEMS IR emitters have been adapted and further developed. An additional rear side mirror increases the optical yield.
Starting from established processes for components with chip edge lengths of several millimeters, a drastic miniaturization to a chip size of 1 x 1 mm² and smaller was achieved. With the transition from wet chemical processes to plasma etching processes, significantly larger aspect ratios and higher dynamics were achieved. In addition, the space required for the functional sensor areas is reduced. Manufacturers in the field of gas sensor technology in particular benefit from the miniaturized emitters, as this enables further miniaturization of the overall system for gas measurement.
Gas sensors are active in many market segments, for example in process measurement technology for monitoring industrial processes, medical technology and environmental sensor technology, for example in building monitoring and/or automation. In consumer products such as home appliances and smartphones, gas sensors measure the air quality in buildings, vehicles or safety-relevant applications.
REM image of the membrane structure of individual chips in the wafer composite