Conductor design for integrated magnetic devices

Abstract

An inductor conductor design which minimizes the impact of skin effect in the conductors at high frequencies in integrated circuits and the method of manufacture thereof is described herein.

What is claimed is: 
     
         1 . An integrated magnetic device, comprising:
 a conventionally formed silicon wafer, having a substrate, an active region comprising transistors, diodes, capacitors and resistors coupled by a conductive interconnect layer, to form an active circuit, wherein the active region touches the top surface of the silicon wafer substrate and includes a first plurality of bond contacts;   wherein the conductive interconnect layer is comprised of multiple layers of conductive material with insulating layers therebetween, the multiple layers of conductive material coupled together by a first plurality of vias piercing their associated insulating layer, wherein the top of the conductive interconnect layer is an insulating layer, having openings to expose a first plurality of bond contacts;   also wherein the insulating layer on top of the conductive interconnect layer is covered by a Silicon Nitride layer, having openings to expose the first plurality of bond contacts;   a first layer of polymer, having a first plurality of openings extending from the top surface of the first polymer layer down to the plurality of bond contacts, wherein the first plurality of openings are filled with a high conductance material forming a second plurality of vias coupled to the first plurality of bond contacts;   a first layer of high conductance material filling the first plurality of openings and the overlaying and touching the surface of the first polymer layer, wherein the first layer of high conductance material is defined and configured to include a plurality of rectangular bottom coil members and a coupling means to connect to the second plurality of vias and coupling to the first plurality of bond contacts;   the plurality of rectangular bottom coil members, composed of the first layer of high conductance material, overlaying and touching the first layer of polymer, each bottom coil member including, a second plurality of bond contacts at the ends of each of the bottom coil members, one of each of a plurality of bottom slots therein, wherein each of the bottom slots pierces its respective bottom coil member;   a second layer of polymer, touching the first layer of polymer and the first layer high conductance material wherein the top surface of the second layer of polymer is planar, the second layer of polymer including a second plurality of openings extending from the top surface of the second layer of polymer down to the second plurality of contacts, wherein the openings in the second layer of polymer are filled with a third plurality of vias;   a layer of titanium touching the second layer of polymer and the tops of the third plurality of vias;   a magnetic core selected from a single layer of magnetic core material or a laminated magnetic core material deposited and defined on the top surface of second layer of polymer, wherein the magnetic core, as defined, does not touch the third plurality of vias exposed on the top surface of the second layer of polymer;   a third layer of polymer touching the second layer of polymer and the top of the magnetic core material, wherein the third layer of polymer includes a third plurality of openings extending from the top surface of the third layer of polymer down to the top surfaces of the third plurality of vias, wherein the openings in the third layer of polymer are filled with a fourth plurality of vias;   a second layer of high conductance material filling the third plurality of openings and overlaying and touching the surface of the third polymer layer, wherein the second layer of high conductance material is defined and configured to include a plurality of rectangular top coil members and coupling to the third plurality of vias;   the plurality of rectangular top coil members, composed of the second layer of high conductance material, overlaying and touching the third layer of polymer, each top coil member including, a third plurality of bond contacts at the ends of each of the top coil members, wherein each one of the third plurality of bond contacts touching and coupling to one each of the fourth plurality of vias, and of a plurality of top slots therein, wherein each of the top slots pierces its respective top coil member; and   a fourth layer of polymer touching the third layer of polymer and the top of the second layer high conductance material, wherein the fourth layer of polymer includes a fourth plurality of openings extending from the top surface of the fourth lay of polymer down to the top surfaces second layer high conductance material, the openings in the fourth layer of polymer are filled with solder balls, wherein the solder balls provide connection to outside circuitry.   
     
     
         2 . The integrated magnetic device of  claim 1 , wherein each of the bottom slots is rectangular and longitudinally aligned and spaced apart from the outside edges of its respective bottom coil member. 
     
     
         3 . The integrated magnetic device of  claim 1 , wherein the single layer magnetic core is sputtered and has a total thickness of 3-15 μm. 
     
     
         4 . The integrated magnetic device of  claim 1 , wherein the laminated magnetic core material is comprised of multiple layers of alternating magnetic material and insulating material, wherein each magnetic film layer thickness ranges from 0.1 μm to 3 μm with a 10 nm AlN dielectric in between. 
     
     
         5 . The integrated magnetic device of  claim 1 , wherein each of top slots is rectangular and longitudinally aligned and spaced apart from the outside edges of its respective top coil member. 
     
     
         6 . A method of forming an integrated magnetic device, comprising:
 providing a conventionally formed integrated circuit wafer, wherein bond contacts of each of the integrated circuits are exposed through openings in an insulating layer at the top of a conductive interconnect layer;   depositing a layer of silicon nitride over the integrated circuit wafer, the layer of silicon nitride touching the insulating layer at the top of the conductive interconnect layer, exposing the bond contacts exposed through the openings in the insulating layer at the top of the conductive interconnect layer by using a pattern and etch process to expose the bond contacts through openings in the silicon nitride layer;   depositing a first layer of polymer, having a first plurality of openings extending from the top surface of the first polymer layer down to the plurality of bond contacts, wherein the first plurality of openings are filled with a high conductance material forming a second plurality of vias coupled to the first plurality of bond contacts;   depositing and patterning a photoresist mold and electroplating a first layer of high conductance material on the surface of the first polymer layer, filling the openings in the first polymer layer, and removing the photoresist mold, thereby coupling the first layer of high conductance material to the first plurality of bond contacts, the first layer of high conductance material is then patterned and etched to form a coupling means to the first plurality of bond contacts and a plurality of bottom coil members which are configured to include either slots or no slots and also include a second plurality of bond contacts at the ends of the bottom coil members;   depositing a second layer of polymer, touching the first layer of polymer and the first layer high conductance material wherein the top surface of the second layer of polymer is planar, the second layer of polymer including a second plurality of openings extending from the top surface of the second layer of polymer down through the second layer of polymer to the second plurality of bond contacts;   filling the second plurality of openings in the second layer of polymer with a third plurality of vias, thereby coupling the second plurality of vias to the first plurality of bond contacts, wherein the third plurality of vias are copper electroplated on the surface of the second polymer layer using a mold mask to define their pattern, filling the openings in the second polymer layer;   sputtering a layer of titanium on the top surface of the second layer of polymer touching the second layer of polymer and the tops of the second plurality of vias;   depositing a magnetic core selected from a single layer of magnetic core material or a laminated magnetic core material on the top surface of second layer of polymer;   patterning and etching using a standard photo resist process the laminated magnetic core, wherein the Multiple layers of alternating magnetic material and insulating material and the Ti adhesion layer are then etched;   stripping the photoresist using standard techniques;   subjecting the magnetic materials to a first anneal to reinforce the magnetic alignment imposed during deposition;   depositing a third layer of polymer, touching the second layer of polymer, the third plurality of vias and the top of the magnetic core, the third layer of polymer including a third plurality of openings extending from the top surface of the third layer of polymer down through the third layer of polymer to the third plurality of vias, wherein the third plurality of openings in the third layer of polymer are filled with a fourth plurality of vias;   electroplating a second layer of high conductance material through a photoresist mold mask, on the surface of the third polymer layer, filling the third plurality of openings in the third polymer layer thereby coupling the second layer of high conductance material to the first plurality of bond contacts, wherein the second layer of high conductance material is defined and configured to include a plurality of rectangular top coil members therein coupling to the third plurality of vias, the second layer of high conductance material is selectively configured to include slots or the absence of slots;   depositing a fourth layer of polymer, touching the third layer of polymer and the second layer of high conductance material, the fourth layer of polymer including openings extending from the top surface of the fourth layer of polymer down through the fourth layer of polymer to the second layer of high conductance material;   subjecting the magnetic layers to a second anneal (300-500° C.) in the presence of a magnetic field (0.1-1 T), wherein the second anneal further defines the easy/hard axes; and   forming solder bumps in the openings formed in the fourth layer of polymer touching the third layer of high conductance material.   
     
     
         7 . The method of forming an integrated magnetic device of  claim 6 , wherein each of the bottom slots is rectangular, longitudinally aligned and spaced apart from the outside edges of its respective bottom coil member. 
     
     
         8 . The method of forming an integrated magnetic device of  claim 6 , wherein the second layer of polymer is chosen from the group of polymers SU8 3000 or PI-2622, wherein if PI-2622 is used, a CMP process must be used to planarize the surface and if SU8 3000 is used instead of PI-2622 for the second Polymer layer, CMP is not required because SU8 3000 is largely self-planarizing to the required tolerance. 
     
     
         9 . The method of forming an integrated magnetic device of  claim 6 , wherein the single layer magnetic core is sputtered and the total thickness is between 3-15 μm, the magnetic layer is selected from the group of Ni80Fe20, Co90Ta5Zr5 or FeAlN and the magnetic layers are subjected to an anneal (300-500 C) in the presence of a magnetic field after sputtering. 
     
     
         10 . The method of forming an integrated magnetic device of  claim 6 , wherein the laminated magnetic core is comprised of multiple layers of alternating magnetic film material and insulating material be deposited using a Veeco Nexus PVDi Tool in a magnetic field on the top surface of second layer of polymer, multiple layers of alternating magnetic material and insulating material are defined to not touch the second plurality of vias exposed on the top surface of the second layer of polymer; 
     
     
         11 . The method of forming an integrated magnetic device of  claim 10 , wherein each magnetic film layer is sputtered, with thickness ranges from 0.1 μm to 3 μm with a 10 nm AlN dielectric therebetween, sputtering is accomplished in the presence of a magnetic field to determine the easy axis of the magnetic material, wherein the orientation in the multiple layers of alternating magnetic material and insulating material  111  due to the imposed B-field during the sputtering process is in the direction of the easy axis and the easy axis is perpendicular to the hard axis, wherein the hard axis is the axis along which the magnetic field, created by the final inductor in normal operation, will flow through the core. 
     
     
         12 . The method of forming an integrated magnetic device of  claim 6 , wherein the laminated magnetic core total thickness is between 5-15 μm and the magnetic layers are selected from the group of Ni80Fe20, Co90Ta5Zr5 or FeAlN and the magnetic layers are subjected to an anneal (300-500 C) in the presence of a magnetic field after sputtering. 
     
     
         13 . The method of forming an integrated magnetic device of  claim 6 , wherein the first and second layers of high conductance material are composed of 20 μm of copper.