Abstract:

Metal-Insulator-Semiconductor micro-capacitors for on-chip energy storage were fabricated and characterized. The capacitors were based on Si nanowires fabricated by Metal Assisted Chemical Etching. 1.2μm long nanowires with 100nm average diameter were created leading to an effective area increase of 6.28, as compared to a flat surface. Nanowires were chemically treated to reduce surface roughness and electronic states and were coated by a HfO2 layer, deposited by Atomic Layer Deposition, to act as the dielectric. Al and Cu were deposited as two possible top metal electrodes. The use of Al as the top electrode was shown to create a parasitic interface oxide between the metal and the dielectric, reducing the measured capacitance. The use of Cu was shown to significantly reduce this problem, leading to more efficient devices. Capacitors with 5.4μF/cm2 capacitance and 8.9x10-7A/cm2 leakage current at -2.5V were demonstrated along with a cutoff frequency of 104Hz. These values make the demonstrated capacitors very attractive for on-chip energy storage applications.

Website