Dielectric layers suitable for high voltage integrated trench capacitors

In this work, two different dielectric stacks consisting of silicon dioxide (SiO2) and silicon nitride (Si3N4) are analyzed regarding their suitability as dielectrics in a high voltage trench capacitor. The processing of the dielectric layers and the resulting edge-coverage in the trench holes are described. Voltage and temperature dependence of the trench capacitance are analyzed and compared with planar capacitors for reference. The leakage currents are measured and the current transport mechanisms are analyzed. The outstanding properties of the devices are a high capacitance per area (1.25 nF/mm2 for SiO2 and 1.5 nF/mm2 for Si3N4), a low temperature coefficient (SiO2: 18 ppm/K; Si3N4: 85 ppm/K from 25100 °C), and a low leakage current (<1x10−6 A) for voltages up to 400 V for Si3N 4.