(Invited) Advanced Materials for Integrated on-Chip Power Converter

We describe electrolessly plated magnetic materials required for the demonstration of a monolithically integrated on-chip inductors. Miniaturization of magnetic inductors and integration on semiconductor chips requires the choice of high performance magnetic materials. The requirements are soft magnetic properties with low coercive force (Hc < 1.0) and high saturation magnetization, high resistivity (r >=110 mohm cm) to reduce inductor losses at high frequencies from eddy currents, and excellent thermal stability to a processing temperature that is dictated by the integration process on-chip (>200~250^oC).  This work demonstrates that a Co₈₅W₅P₁₀ thin film deposited using electroless chemistry on a Pd activated Ni₈₀Fe₂₀ seed layer meets all the materials requirements for a low process temperature integrated inductor.  A 1.2 mm thick CoWP layer deposited on a 60nm Ni₈₀Fe₂₀ seed layer has a resistivity of 110 mohm cm and its moment and anisotropy are stable after 200^oC thermal cycling.  The work also shows that the initial stages of growth, starting from the magnetic Ni₈₀Fe₂₀ seed layer surface, affect greatly the growth and thermal stability of the CoWP film.  As far as maintaining a higher ~250°C thermal processing limit, we obtained encouraging data for CoWP and NiFeBP films thinner than 300nm grown by electroless deposition. We will also discuss approaches to achieving laminated films incorporating these materials.