Wafer arrangement for gas sensor
A gas sensor includes a multi-wafer stack of a plurality of layers and a measurement chamber. The plurality of layers includes a first layer comprising a sensor element that has a microelectromechanical system (MEMS) membrane; and a second layer comprising an emitter element configured to emit electromagnetic radiation. The measurement chamber is interposed between the first layer and the second layer. The measurement chamber is configured to receive a measurement gas and further receive the electromagnetic radiation emitted by the emitter element as the electromagnetic radiation travels along a radiation path from a first end of the measurement chamber to a second end of the measurement chamber that is opposite to the first end.
1. A gas sensor, comprising:
a wafer arrangement comprising:
a first substrate comprising:
a first portion that includes a sensor element that includes a microelectromechanical system (MEMS) membrane; and
a second portion laterally arranged with respect to the first portion, wherein the second portion includes an emitter element configured to emit electromagnetic radiation toward the MEMS membrane on a radiation path;
a measurement chamber configured to contain a measurement gas, wherein the measurement chamber is in the radiation path between the emitter element and the MEMS membrane; and
a housing arranged over the first portion and the second portion of the first substrate and defines the measurement chamber, wherein the housing is configured to receive the electromagnetic radiation from the emitter element and redirect the electromagnetic radiation towards the sensor element.
2. The gas sensor of claim 1 , wherein the wafer arrangement comprises:
a second substrate comprising:
a third portion arranged adjacent to the first portion of the first substrate, wherein the first portion comprises a first cavity and the third portion comprises a second cavity that is conjoined with the first cavity to form a pressure equalizing chamber, wherein the MEMS membrane is interposed between the measurement chamber and the pressure equalizing chamber; and
a fourth portion laterally arranged with respect to the third portion, wherein the second portion comprises a third cavity and the fourth portion comprises a fourth cavity that is conjoined with the third cavity to form an enclosed hollow space.
3. The gas sensor of claim 2 , wherein the emitter element is interposed between the measurement chamber and the enclosed hollow space.
4. The gas sensor of claim 2 , wherein the pressure equalizing chamber is sealed from the measurement chamber by the MEMS membrane.
5. The gas sensor of claim 2 , wherein the MEMS membrane includes an opening that connects the measurement chamber to the pressure equalizing chamber.
6. The gas sensor of claim 1 , wherein the measurement gas converts the electromagnetic radiation into a photoacoustic signal, and the sensor element is configured to measure the photoacoustic signal by detecting deflections of the MEMS membrane.
7. The gas sensor of claim 1 , further comprising:
a perforated counter electrode arranged between the MEMS membrane and at least a portion of the measurement chamber, wherein the perforated counter electrode is configured to reflect infrared radiation.
8. The gas sensor of claim 7 , wherein the perforated counter electrode is capacitively coupled to the MEMS membrane.
9. The gas sensor of claim 1 , wherein the MEMS membrane is configured to have a deflection which is dependent on an energy of the electromagnetic radiation.
10. The gas sensor of claim 1 , wherein the emitter element is configured to emit the electromagnetic radiation in a pulsating manner with a frequency that is greater than 0.1 Hz.