Palladium Activated Self-Assembled Monolayer For Magnetics On Silicon Applications

Magnetic thin films such as Permalloy (Py) have been extensively used as core material in integrated power magnetic components (micro-inductors and transformers) for their excellent soft magnetic properties. Existing core electrodeposition technology requires sputtered permalloy seed layer. This seed layer etches slowly compared to the electroplated core during magnetic core patterning. In this work, a new electroless deposition process has been developed where samples are activated by palladium to realize a thin catalytic layer on SiO2. Up to 1 mu m thick permalloy (similar to 22% +/- 3% Fe and similar to 78% +/- 3% Ni) is deposited from an in-house developed borane based bath to achieve similar to 30-35 mu Ohm-cm resistivities. The magnetic properties of permalloy deposits reveal distinct hysteresis loop with coercivity (similar to 4.5 Oe). The electroless permalloy over-etch (12 mu m) compared with sputtered permalloy seed is found to be negligible (2 mu m). This demonstrates the applicability of permalloy electroless deposition as a seed for high yield batch fabrication of magnetics on silicon devices.