Three-dimensional silicon-integrated capacitor with unprecedented areal capacitance for on-chip energy storage

Capacitors are the most critical passive components of future in-package and on-chip electronic systems with augmented energy-storage capabilities for consumer and wearable applications. Although an impressive increase of both capacitance and energy densities has been achieved over the last years for supercapacitors (SCs), electronic applications of SCs have been hindered by their intrinsic low operation voltage (a few Volts), poor frequency range (a few Hz to hundreds of Hertz), and difficult integration with integrated circuit (IC) processes. On the other hand, integrated dielectric capacitors (DCs) able to operate at higher voltage (tens of Volts) and higher frequencies (hundreds of kHz to MHz) suffer from significantly lower capacitance and energy densities. Here, we leverage the unique atomic layer deposition of conductive (TiN) and dielectric (Al2O3 and HfAlOx) nanocoatings (20 and 40 nm) into trenches etched in silicon with ultra-high aspect-ratio (up to 100) to integrate 3D microcapacitors with areal capacitance up to 1 μF/mm2. This sets the new record for silicon capacitors, both integrated and discrete, and paves the way to on-chip energy storage. The 3D microcapacitors feature excellent power and energy densities, namely, 566 W/cm2 and 1.7 μWh/cm2, respectively, which exceed those of most DCs and SCs. Further, the 3D microcapacitors show excellent stability with voltage (up to 16 V) and temperature (up to 100 °C), over 100 h of continuous operation.