SAN FRANCISCO -- A new method for layering magnetic components atop CMOS wafers is showing promise for improved power management in life sciences devices, integrated navigation systems and portable consumer electronics.
Enpirion (Hampton, N.J.), which makes integrated power circuits, announced the commercialization of a manufacturing process that layers wafer level magnetics (WLM) as a two-dimensional thin film. Enpiron said the film can be deposited on top of 6 to 8 inch CMOS wafers to increase power performance and device life.
Enpirion's process uses an iron-cobalt alloy (Fe-Co) that the company is branding as FCA (not to be confused with free carrier absorption in silicon or the IEEE's formal concept analysis). This miniaturization of passive magnetic components and their assimilation with ICs at the wafer level can also help shrink CMOS wafers from their 3-D discrete shape to a thinner package, the company claimed in its announcement this week (Nov. 27).
"Increasing the switching frequency allows the use of smaller inductors utilizing electroplated WLM materials that can be post-CMOS processed," Enpirion co-founder Dr. Trifon Liakopoulos said in a statement.
The high magnetic saturation of the Fe-Co alloy makes it a good fit for use in single or multiple layers in power circuits. This would make it compatible with flip chip, wire bonding and solder re-flow packaging methods. Enpirion said its alloy maintains high resistivity, low coercivity and maintains high effective permeability at frequencies higher than 20 MHz. Using the 2-D alloy allows for signal isolation, micro-electromagnets for life sciences, integrated magnetic sensors for navigation and power management circuits for portable consumer devices.
Enpirion’s wafer level magnetics inductor with 4 µm FCA thick core (FCA core is 100 times thinner than discrete inductor core) Source: Enpirion
Previous work has been done on processing Fe-Co alloys for computation, most notably by S. Lesz at the Silesian University of Technology in Poland. Wafer-level assembly using global magnetic lifting and localized induction welding has been broadly used in the industry since 2005 as a paper published by researchers at Tsinghua University in Taiwan illustrates.
The picture above is a comparison of the "big" discrete inductors and the wafer level micro-inductors they sit on.
The announcement is about the capability to incorporate magnetic alloy with wafer processing to make such MEMS inductors possible.
Well, yes, but the passive being put on chip here is ferrite core inductors, which is a big deal, as it allows very large inductors needed for reasonably low frequency switching power supplies to be integrated.