Abstract:
A process of making inductors for integrated circuit packages may involve forming an inductor upon a magnetic film on a package substrate. Conductors coupled either to a die or a voltage converter extend perpendicularly through the film to conductive plates, defining current paths through and across the film.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/217,293, filed on Jul. 2, 2008 now U.S. Pat. No. 7,911,313. 
    
    
     BACKGROUND 
     This relates generally to integrated circuits, packages for integrated circuits, and inductors for use with integrated circuits. 
     Inductors and transformers may be used in microelectronic circuits as part of voltage converters and for electromagnetic interference noise reduction. Conventionally, transformers have cores and wire windings wrapped around those cores. 
     In order to form an inductor for use in a voltage regulator that supplies current to an integrated circuit, it would be desirable to have a way to make such transformers using conventional integrated circuit techniques. As a result, such devices could be made inexpensively, for example, while also making integrated electronic components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an enlarged, bottom view of a substrate in accordance with one embodiment of the present invention; 
         FIG. 2  is a partial, enlarged, cross-sectional view taken generally along the line  2 - 2  in  FIG. 1 ; 
         FIG. 3  is a partial, cross-sectional view taken generally along the line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken generally along the line  4 - 4  in  FIG. 2 ; and 
         FIG. 5  is a perspective, exploded view of one embodiment of the magnetic film used in the embodiment shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an integrated circuit package  10  may include a substrate  14 . The substrate  14  is generally an insulating material with conductive paths for conveying signals between different components mounted on the substrate  14 . For example, the substrate  14  may be a printed circuit board. 
     In accordance with some embodiments, the substrate  14  is enclosed to form a circuit package that provides for connections to various internal, packaged components. The package encloses the substrate  10  and the substrate  10  mounts an integrated circuit die  24  on the opposite substrate side to the side depicted in  FIG. 1 . 
     On the substrate  14  side depicted in  FIG. 1 , an integrated inductor  30  may be mounted. The integrated inductor  30 , in one embodiment, may actually be part of a transformer. The integrated inductor  30  extends through the substrate  14 , in one embodiment, to a voltage converter  26  on the opposite side of the board  14 . Conventionally, the voltage converter may be coupled to a power supply (not shown). 
     Thus, the inductor  30  may be part of a transformer utilized in connection with the voltage converter  26  to supply power to the die  24 , which may be a controller or processor, as examples. In some embodiments, the inductor  30  may be effectively mounted directly on the substrate  14  of an integrated package, enabling a smaller size and reducing the distance between the voltage converter  26 , the integrated inductor  30 , and the die  24 . 
     Referring to  FIG. 2 , the integrated inductor  30  may include a planar film  16  of magnetic material. In some embodiments, the film  16  may be made up of a number of layers of magnetic material. The use of a number of laminations or layers, instead of one solid material, may be useful in reducing eddy currents in some embodiments. Suitable magnetic materials for film  16  include CoZrTa, CoFeHfO, CoPRe, CoPFeRe, or NiFe. 
     A plurality of conductors  18   a - 18   d  extend vertically and perpendicularly through the horizontal magnetic film  16 . The conductors  18  may be tubular and, in some embodiments, for example, may be formed as plated through holes. The conductors  18  may, in some embodiments, be hollow copper cylinders with an insulating material in the center. In some cases, the ends of the conductors  18  may be closed by a conductive end cap that may be formed by suitable plating operations. As one example, the tubular conductors  18  may be formed of copper. 
     The conductors  18   a  and  18   d , in the form of vertically extending vias, do not contact the magnetic film  16 , but, instead, a gap  25  is formed between the conductors  18   a  and  18   d  and the proximate magnetic film  16 . However, the conductors  18   a  and  18   d  make electrical contact to the substrate  14  and to the horizontal conductors  22   a  and  22   b . In some embodiments, the conductors  22  may be planar and parallel to the film  16 . 
     In contrast, the conductors  18   b  and  18   c  make electrical and physical contact only with the voltage converter  26  and the horizontal conductors  22   a  and  22   b.    
     Thus, current can flow through the voltage converter  26  and into a horizontal conductor  22   a  or  22   b , as the case may be, from conductors  18   b  and  18   c . The conductors  18   a  and  18   d  may be coupled to the die  24  in one embodiment. Thus, the inductor structure is between the voltage converter  26  and the die  24 . 
     A polyimide (not shown) may be used, in one embodiment, between the magnetic film  16  and the horizontal conductors  22   a  and  22   b . An insulator  32  may be provided between the substrate  14  and the magnetic material  16 , in one embodiment. 
     Referring to  FIG. 3 , the conductors  18   a  and  18   b  do not contact the magnetic film  16 , but pass through the magnetic material without touching or making electrical contact. As a result of current flowing through the conductors  18   a  and  18   c  by way of the horizontal plate  22   a  and current flowing through the conductors  18   b  and  18   d  by way of the horizontal plate  22   b , magnetic fields revolve around the conductors  18 . 
     The field strength of the magnetic field is relatively low in the regions at the corners A and intermediately, as indicated at B. Thus, in some embodiments, the magnetic material may be effectively eliminated from these areas, reducing the eddy currents. 
     Further, as indicated in the regions E and F, the magnetic material may be effectively eliminated between adjacent conductors, such as the conductors  18   a  and  18   b  and  18   c  and  18   d , in some embodiments. This will help decrease the eddy currents in some embodiments. 
     Referring to  FIG. 4 , the conductors  18   a - 18   d  are effectively aligned or collinear, in one embodiment. Thus, current passing through a horizontal plate  22   a , via conductors  18   a  and  18   b , bypasses the other conductors and vice versa. The plates  22   a  and  22   b  may be coplanar in one embodiment. In some cases, the transformer may be made up of a large number of such horizontal plates  22   a  and  22   b , coupled through a larger number of conductors  18 . 
     In accordance with one embodiment of the present invention, the magnetic film  16  may be formed by first forming a seed layer  28  on the insulator  32 . Then, the first layer  16   a  of magnetic material may be deposited while exposed to a magnetic field which creates a hard axis, indicated at D. Then, a layer of insulator  20  may be deposited. Thereafter, another layer  16   b  of magnetic material may be deposited while being exposed to an orthogonal oriented magnetic field to create a hard axis C perpendicular to the axis D. This may be followed by any number of additional layers of the type, indicated at  16   a ,  20 , and  16   b , to build up a desired thickness. 
     In one embodiment, if the XY plane is the plane of the substrate  14 , alternately depositing the magnetic material laminations with orthogonal hard axes of magnetization in the direction of the X axis, then the Y axis creates a microstructure with two hard axes in the plane of the substrate. 
     Advantageously, the directions of the major axes D and C alternate from magnetic lamination to the next. Thus, in combination, the overall film  16  has good magnetic properties in both the C and D directions. 
     Alternatively, in some embodiments, the magnetic material may be formed and annealed with a perpendicular magnetic field such that both hard axes are in each plane. Thus, referring to  FIG. 5 , this would result in the hard axes of magnetization H being provided in addition to the axes D in the layer  16   a  and the hard axes of magnetization G, in addition to the axes C, in the layer  16   b.    
     A variety of adhesion layers may be used if necessary. For example, thin titanium or tantalum adhesion layers may be utilized with CoZrTa magnetic material. Electroplating may be used to form the layers in some embodiments. However, in other embodiments, electroless plating techniques may be utilized. 
     In one embodiment, twenty nanometers of titanium layer deposition may be followed by an 0.1 to 0.2 micron thick copper seed layer or an 0.3 micron thick cobalt seed layer, followed by filling of the conductors  18  with an insulator or other material, including conductive materials. In some embodiments, it is advantageous to use a tubular conductor since the conductivity is largely a function of the outside diameter. 
     Suitable materials for the insulator  20  include silicon dioxide, aluminum oxide, cobalt oxide, polyimide, silicon nitride, or any other insulator. Advantageously, the insulator  20  is made as thin as possible and, advantageously, may be less than the thickness of any layer of the magnetic film  16 . 
     The layers  16   a  and  16   b  may be on the order of one-half micron in thickness in one embodiment. Four to ten lamination layers may be formed to create the desired thickness. For example, films  16  of from two to twenty microns thick may use from four to twenty lamination layers, as examples. 
     In some embodiments, shape anisotropy may be used to provide a preferred direction in each lamination, thereby making the overall combined film  16  thick enough to have good magnetic properties in the C and D directions. 
     In some embodiments, the film  16  may be shaped using conventional photolithography techniques. Generally, the sizes of the components may be relatively small and, in some embodiments, voltages of one to two volts may be utilized. 
     In some embodiments, it is advantageous that the magnetic film  16  is formed in a plane, while the current flow through the conductors  18  is perpendicular to the plane of the magnetic film  16 . This may reduce eddy currents in some embodiments. In some embodiments, it is desirable to have only one composite magnetic material film  16  to avoid using magnetic vias that can exacerbate eddy currents. In some embodiments, a quality factor at 30 MHz of twenty to fifty is possible using four to eight laminations, respectively. 
     By eliminating magnetic material from regions, such as the regions A and B of low magnetic field, eddy currents may be reduced in some embodiments. Using a magnetic film  16  that is thick enough to reduce shape anisotropy (i.e. one greater than 1.5 microns) allows for an easy axis of magnetization in the vertical direction. 
     Inductors and magnetic materials may, in accordance with embodiments of the present invention, be utilized for radio frequency and wireless circuits, as well as for voltage converters and for electromagnetic interference noise reduction. Integrated on die DC-DC converters control the power consumption in multi-core processor applications and are important to controlling the power delivery in mobile and ultra-mobile central processing units. Microgranular control of individual cores can be achieved to save on-power by reducing the power to individual cores as needed. An integrated DC-DC converter at high power levels of 100 watts or more can be used to supply power to a processor, graphic chips, chipsets, or other circuits. 
     References throughout this specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present invention. Thus, appearances of the phrase “one embodiment” or “in an embodiment” are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be instituted in other suitable forms other than the particular embodiment illustrated and all such forms may be encompassed within the claims of the present application. 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.