Magnetic Thin-Film Inductors for Monolithic Integration with CMOS Noah Sturcken 1✚ , Ryan Davies 1 , Hao Wu 1 , Michael Lekas 1 , Kenneth Shepard 1,3 , K.W. Cheng 2 , C.C. Chen 2 , Y.S. Su 2 , C.Y. Tsai 2 , K.D. Wu 2 , J.Y. Wu 2 , Y.C. Wang 2 , K.C. Liu 2 , C.C. Hsu 2 , C.L. Chang 2 , W.C. Hua 2 , Alex Kalnitsky 2 1 Ferric, Inc. New York, NY, USA; ✚ 155 W. 121 st St., NY NY 10027, USA, nsturcken@ferricsemi.com , +1-646-599-0765; 2 Taiwan Semiconductor Manufacturing Company, Hsinchu, Taiwan; 3 Dept. of Electrical Eng., Columbia University, NY, NY Abstract This paper presents the fabrication, design and electrical performance of magnetic thin-film inductors for monolithic integration with CMOS for DC-DC power conversion. Magnetic core inductors were fabricated using conventional CMOS processes to achieve peak inductance density of 290nH/mm 2 , quality factor 15 at 150MHz, current density exceeding 11A/mm 2 and coupling coefficient of 0.89 for coupled inductors. Introduction The introduction of high permeability magnetic thin-films to CMOS manufacturing provides a new class of integrated inductor, enabling higher levels of integration and performance for applications that are currently relegated to using discrete inductors. Integrated magnetic thin-film inductors incorporate high permeability (µ Rel > 500), low coercivity (H C < 1 Oe) magnetic materials to provide a low reluctance path for the coil’s magnetic flux, generating a significant inductance enhancement [1-4] relative to air-core inductors. These inductors can be fabricated with standard CMOS manufacturing processes and have a low profile (< 30µm), which makes them compatible for monolithic integration with CMOS ICs as a back-end process option (Figs. 1,2). The inductors presented here exhibit high inductance for a broad frequency band (> 1 GHz), high current density and low DC resistance relative to existing on-chip inductor technologies. These inductors will enable a new set of IC applications such as monolithically integrated voltage regulation (MIVR), where all components of a switched inductor DC-DC power converter are integrated on-chip. Integrated voltage regulation allows power to be delivered to ICs at higher voltages and then efficiently down converted on-chip, reducing I 2 R loss in the power delivery network, and enabling improved power management with a larger number of independently scalable on-chip power supplies [5-8]. Fabrication of Magnetic Thin-Film Inductors Magnetic thin-film inductors were fabricated at TSMC on 300mm wafers in a pilot manufacturing line using standard CMOS manufacturing equipment and processes. Fig. 1 illustrates the cross section of the inductors integrated with a CMOS IC, Fig. 2 is an SEM cross section of the same. The inductor consists of three metal layers separated by insulators. The inductor coil is formed from copper interconnect layers CU1 and CU2. CU1 is planar while CU2 is non-planar and connects to CU1 through openings in insulating layers. The magnetic core layer is MAG. For characterization, inductors were fabricated on a test vehicle that includes only relevant inductor layers (CU1, MAG, CU2, insulators). Magnetic thin-film inductors have also been fabricated on 300mm CMOS wafers at TSMC. Passivation and wafer finishing steps necessary for commercial CMOS wafers were completed on the test vehicle wafers and consequently the performance demonstrated on the test vehicle will be consistent with inductors fabricated on commercial CMOS wafers. Fig.1 Illustrated cross section of magnetic thin-film inductors monolithically integrated with CMOS IC Fig.2 SEM cross section of magnetic thin-film inductors monolithically integrated with CMOS IC