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|Inter-Wafer Inductors with 3D Hyper-Integration for Power Delivery Applications|
|Keywords: Inter-Wafer Inductors , 3D Hyper-Integration , Power Delivery|
|Power delivery is becoming a major issue in deep sub-micron VLSI designs due to the rapid increase in power density and frequency. Today’s micro-processors can consume as much as 100W with operating voltages on the order of 1V and clock frequency of several GHz, leading to a total current in the order of one hundred amperes with large di/dt noises. Conventional power delivery methods have fundamental limitations in meeting the power requirements of future IC technologies. Increasing input voltage, moving the power regulator closer to the microprocessor by integrating it on chip, or using on-chip inductors operating at higher frequency can alleviate the conventional power delivery problems. However, on-chip inductor integration typically results in increased area, lower yield, and higher expenses in active dice. Moreover, on-chip inductor performance suffers from substrate losses due to the close proximity of the devices to a conductive silicon substrate. Three Dimensional (3D) hyper-integration provides a potential solution for power delivery systems by integrating inter-wafer inductor between two bonding wafers. In such a 3D power delivery architecture, a voltage regulator module (VRM) cellular array on a thinned substrate is vertically integrated with the processor using wafer-to-wafer bonding and through silicon vias, with inter-wafer inductor in between. In this work, inter-wafer inductor design with magnetic material is investigated with 3D hyper-integration technology. The inductance and L/R ratio of inter-wafer inductors are evaluated based on the requirements of a prototype dc-dc converter. A two-leg coupled 3D inductor is designed and simulated using Maxwell 3D electric-magnetic simulator to determine its quality factor and L/R ratio. The influence of L/R ratio of inter-wafer inductor on the efficiency of the dc-dc converter is analyzed. The feasibility to realize the inter-wafer inductor is also investigated.|
Rensselaer Polytechnic Institute