Solution-derived electrodes and dielectrics for low-cost and high-capacitance trench and Through-Silicon-Via (TSV) capacitors

This paper explores and demonstrates a novel technique to conformally coat solution-derived electrodes and dielectric films over Through-Silicon-Via (TSV) or Through-Silicon Trench (TST) structures. In this technique, precursor solution for electrode or dielectric coatings is dispensed on the top of a TSV wafer and infiltrated through the via by creating a pressure gradient. Two material systems used in capacitors, Lanthanum Nickel Oxide (LNO) as electrode and Lead Zirconate Titanate (PZT) as dielectric, were deposited on the TSV surfaces using this technique. SEM cross-section analysis showed that the vacuum-infiltration can be extended to conformally coat on trenches with aspect ratios of greater than 5. A planar capacitor with density of 3 μF/cm2 and low leakage was fabricated to demonstrate the material compatibility. Using this technique, a trench capacitor device can be fabricated with an all-solution coating process, without involving any expensive deposition tools. This can thus eliminate costly platinum electrodes that are frequently required to yield high permittivity PZT films. This technique can also address the through-put limitations of today's conformal deposition technologies such as sputtering, Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD). The tool and process can also be applied to other 3D silicon structures where conformal ceramic coatings are needed.