posted on 2020-03-06, 17:33authored byAgin Vyas, Kejian Wang, Alec Anderson, Andres Velasco, Ruben Van den Eeckhoudt, Mohammad Mazharul Haque, Qi Li, Anderson Smith, Per Lundgren, Peter Enoksson
On-chip micro-supercapacitors (MSCs),
integrated with energy harvesters,
hold substantial promise for developing self-powered wireless sensor
systems. However, MSCs have conventionally been manufactured through
techniques incompatible with semiconductor fabrication technology,
the most significant bottleneck being the electrode deposition technique.
Utilization of spin-coating for electrode deposition has shown potential
to deliver several complementary metal–oxide–semiconductor
(CMOS)-compatible MSCs on a silicon substrate. Yet, their limited
electrochemical performance and yield over the substrate have remained
challenges obstructing their subsequent integration. We report a facile
surface roughening technique for improving the wafer yield and the
electrochemical performance of CMOS-compatible MSCs, specifically
for reduced graphene oxide as an electrode material. A 4 nm iron layer
is deposited and annealed on the wafer substrate to increase the roughness
of the surface. In comparison to standard nonroughened MSCs, the increase
in surface roughness leads to a 78% increased electrode thickness,
21% improvement in mass retention, 57% improvement in the uniformity
of the spin-coated electrodes, and a high yield of 87% working devices
on a 2″ silicon substrate. Furthermore, these improvements
directly translate to higher capacitive performance with enhanced
rate capability, energy, and power density. This technique brings
us one step closer to fully integrable CMOS-compatible MSCs in self-powered
systems for on-chip wireless sensor electronics.