MIS capacitor

The MIS capacitor is in electrical engineering, a special condenser, which is constructed in the form of the eponymous metal - insulator-semiconductor structure. As in the MOS field effect transistor of this layer structure, for historical reasons, often referred to as a MOS capacitor. It is assumed to be an oxide insulator material ( dielectric) specifically.

The maximum capacity CMIS ( max ) is calculated analogously to the plate capacitor.

With:

• εr relative ... ( material-specific ) permittivity of the insulator
• ε0 permittivity of vacuum ...
• A surface ...
• D ... thickness of the insulator

The preparation is carried out depending on the material system ( it is also conceivable polymers as an insulator ) in different ways. To serve as an example on the basis of silicon and silicon dioxide at this point, a MOS capacitor. In this case, on the semiconductor substrate (substrate ) is a thin layer of oxide (silicon dioxide) is applied (such as thermal oxidation or CVD TEOS ), and then vapor deposited with a metal.

The structure and thus the capacitor is present in each of the MIS field effect transistor. For steady in microelectronics miniaturization of the following situation. From the formula above it follows that increases with increasingly thin insulator layer capacitance. This is important for all MIS components insulating layer should not fall below a layer thickness of 10 nm. Among occur with decreasing layer thickness reinforced tunnel currents through the insulator material. These leakage currents degrade, among other things, the electrical properties of MIS capacitors, of MIS field effect transistors.

The continued scaling of devices in microelectronics led to that in the commercially available integrated circuits of the 2000s, the insulating layer of silicon dioxide was only 1-2 nm and losses by tunneling currents were too high. For this reason, increased several leading manufacturers of mid-and late 2000s on so-called high-k materials for as insulation material.