Direct Al-Imprinting Method for Increased Effective Electrode Area in MIM Capacitors

Abstract

A method for enhancing the capacitance density of metal–insulator–metal (MIM) capacitor by directly imprinting an Al thin film on a Si wafer using a Si stamp is presented. Micrometer-sized features with a depth of up to $1.8~\mu \text{m}$ are demonstrated, showing an increase in the effective Al film area of up to 58%. MIM capacitors with an anodic barrier-type alumina dielectric were fabricated using both imprinted electrodes and flat electrodes. An increase of the capacitance density of the MIM capacitors with the increase of the effective surface area was achieved without increasing the nonlinearity coefficient $\alpha $ . This is not the case when the capacitance density increase is achieved by decreasing the dielectric thickness. We showed that for a capacitance density of $\sim 10$ fF/ $\mu \text{m}^{2}$ , the value of $\alpha $ was 45% lower in the case of the imprinted electrodes compared with that of flat electrodes. The obtained results represent a novel method for creating high-density MIM capacitors without very large values of $\alpha $ . The leakage current is shown to remain low in spite of the surface area increase. This is attributed to the reduction of surface roughness of the electrodes, caused by the imprinting process.