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The Micronas mySENS gas sensing technology represents a new versatile integrated sensor technology based on a CCFET Sensor (CCFET = Capacitive Coupled Field Effect Transistor). This sensor technology aims at detection of concentration changes of selected gases in ambient environments in a broad variety of different applications. Its fabrication process is embedded into Micronas’ CMOS manufacturing technology. Thus, the sensor can be integrated together with control and evaluation electronics into one single chip, profiting from both miniaturisation as well as design experience of current advanced semiconductor technology.
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Measurement principle
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Fig. 1: Schematic setup of a CCFET
gas sensor |
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The sensor is based on a conventional MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) with its floating gate connected to a large sensing electrode. The electrode is capacitively coupled to a gas sensitive layer on a suspended gate that is mounted on top of the chip,
with an air gap in between. Any gas induced change of the sensitive layer’s surface potential induces a modulation of the readout transistor (see Fig. 1), that is detected by the integrated readout electronics. |
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Fig. 2: View of CCFET gas sensor with
mounted suspended gate |
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The CCFET sensor can be individually tailored to a specific sensing task by choosing the appropriate sensitive layer for the suspended gate. A variety of different materials is available, including noble metals, metal oxides or organic layers, depending on the application. The interaction between sensitive layer and ambient gas molecules is a dynamic process that reacts directly to gas concentration changes. As these processes already take place at room temperature, an unheated low-power operation is possible for certain gas species.
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Fig. 3: Micronas CCFET gas sensor
in prototype package |
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Micronas has developed a patented sensor setup for drift reduction and temperature compensation. The current sensor demonstrator generation includes 2 individual CCFET modules, a temperature sensor and electronic components such as voltage and power regulators, A/D and D/A devices and a digital control interface. For prototype evaluation the sensor is mounted in a standard small form factor package, sealed against dust by a diffusion membrane. Different package options are possible. |
