Advanced processing for high efficiency inductors for 2.5D/3D Power Supply in Package

Realizing an integrated Power Supply in Package solution using a 2.5D or 3D integration technology requires significant advancement in manufacturing processes of magnetic components such as inductors, transformer. Development of these integrated structures involves fabrication of high aspect ratio integrated windings and 3D core topology. These process improvements are required to reduce the losses i.e, copper conduction loss and enhance inductance density through a multilayer closed magnetic core. This work reports development of resist processing techniques to achieve thick copper windings with resist aspect ratio of 5.5. Integrated inductors and transformers require closed magnetic cores such as (Ni
₄₅
Fe
₅₅
) to maximize the stored flux. At higher operational frequencies, the lower device footprint requires stacked multi-layer magnetic cores with 3D topologies to close the flux path. This work also presents new processing technique using temporary resist to pattern magnetic core deposited in a cavity of over 70 μm depth while minimizing the over-etch of the magnetic core. A 75 μm single spin process is developed with negative tone THB-151N as replacement for existing permanent SU-8 resist process. This process has significant advantage in terms of easy removal, resolution and adhesion to metals for electroplating applications. Core over-etch were reduced by 44% on using THB 151N and excellent adhesion was achieved.