There is a need for semiconductor devices that can operate at high temperatures (300 - 600 °C), e.g. as sensors in hot gases. We have fabricated metal - oxide - silicon carbide structures to characterize the different interfaces:

1. the structure and surface chemistry of the gate metal
2. the gas dependent electrical potentials and the adhesion between the gate and the insulator
3. the electronic properties between the insulator and the silicon carbide

The figures show the schematics and a photo of one of the studied devices, a 1x1 cm2 SiC sample. The electrical gate contact is made by a thin gold wire to prevent damage to the gate due to differential thermal expansion during heating.

Even very low impurity levels influence the electronic properties of the insulator - silicon carbide interface. It is therefore important to process the samples in a clean environment. Before critical steps, like the deposition of the gate metal, we clean our samples with the RCA clean (hot H2O2 / NH3 and hot H2O2 / HCl). This has resulted also in better adhesion between the metal and the insulator.

SEM photo of a smooth, 100 nm thick platinum gate. The metal has been deposited by e-beam evaporation at 500 °C.