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To achieve a package-level DC power grid for the next-generation power delivery to LSIs, multiple point-of-load (POL) buck DC-DC converters must be integrated into the package. We developed a 180 nm CMOS switch DC-DC buck converter for the POL DC power supply using a Zn-Fe ferrite core planar inductor embedded in an organic interposer. The embedded inductor had a 25 m thick copper spiral coil sandwiched by 10 m thick Zn-Fe ferrite thick film fabricated using the spin-spray method, which exhibited an inductance of 4.6 nH and a Q-factor of 11 at 50 MHz. A 180 nm CMOS switch was mounted using a flip-chip scheme on the organic interposer with the embedded inductor. The developed 50 MHz switching CMOS switch buck DC-DC converter exhibited a power conversion efficiency of about 68% when the input voltage was 2 V, the on-duty ratio was 0.5, the output voltage was 0.855 V, and the current was 1 A.

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A power inductor component is relatively very thick and large shape. Therefore, these components are not appropriate feature to be embedded into a LSI package and mounted nearby a LSI chip, it is challengeable to make the embedded application. However, LSI power delivery system is going for low voltage and large current, and losses between power supply and loads impacts on the power supply efficiency characteristic. In order to solve this problem, miniaturization for a power inductor is needed to realize the embedded applications. As one of approaches to realize the power delivery systems, the planar power inductor with Zn-Ferrite film has been studied for the next generations. A structure of planar power inductor was designed to be configured 2-turn inner copper spiral coil covered with top and bottom magnetic core. The Zn-Ferrite film used as a magnetic core has a high resonance frequency around 300MHz and high saturation magnetization of 0.6T or more, and this film can be formed in low temperature, which can be handled in parallel way to fabricate an organic package. We have developed the organic package with employing the power inductors covered with Zn-Ferrite as prototype of the embedded application, and evaluated the electrical and magnetic characterizations. The thickness of embedded planar power inductor covered with Zn-ferrite film is 50um, and the size is 850um squares. Q factor is 10 to 13 in 30MHz to 100MHz. The degradation of inductance caused by the superimposed current does not happen without changing until 3A.

H. FUKETA a) , Y. SHINOZUKA a) , K. ISHIDA a) , M. TAKAMIYA a) , T. FUJII b) , H. SHIMIZU b) , K. KOBAYASHI b) , T.SATO c) , and T. SAKURAI a)