Abstract:
The invention relates to an inductor comprising a plurality of interconnected conductive segments interwoven with a substrate. The inductance of the inductor is increased through the use of coatings and films of ferromagnetic materials such as magnetic metals, alloys, and oxides. The inductor is compatible with integrated circuit manufacturing techniques and eliminates the need in many systems and circuits for large off chip inductors. A sense and measurement coil, which is fabricated on the same substrate as the inductor, provides the capability to measure the magnetic field or flux produced by the inductor. This on chip measurement capability supplies information that permits circuit engineers to design and fabricate on chip inductors to very tight tolerances.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
   This application is a division of U.S. patent application Ser. No. 09/821,240, filed on Mar. 29, 2001 now U.S. Pat. No. 6,357,107, which is a division of U.S. patent application Ser. No. 09/350,601, filed on Jul. 9, 1999, now issued as U.S. Pat. No. 6,240,622, the specifications of which are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates to inductors, and more particularly, it relates to inductors used with integrated circuits. 
   BACKGROUND OF THE INVENTION 
   Inductors are used in a wide range of signal processing systems and circuits. For example, inductors are used in communication systems, radar systems, television systems, highpass filters, tank circuits, and butterworth filters. 
   As electronic signal processing systems have become more highly integrated and miniaturized, effectively signal processing systems on a chip, system engineers have sought to eliminate the use of large, auxiliary components, such as inductors. When unable to eliminate inductors in their designs, engineers have sought ways to reduce the size of the inductors that they do use. 
   Simulating inductors using active circuits, which are easily miniaturized, is one approach to eliminating the use of actual inductors in signal processing systems. Unfortunately, simulated inductor circuits tend to exhibit high parasitic effects, and often generate more noise than circuits constructed using actual inductors. 
   Inductors are miniaturized for use in compact communication systems, such as cell phones and modems, by fabricating spiral inductors on the same substrate as the integrated circuit to which they are coupled using integrated circuit manufacturing techniques. Unfortunately, spiral inductors take up a disproportionately large share of the available surface area on an integrated circuit substrate. 
   For these and other reasons there is a need for the present invention. 
   SUMMARY OF THE INVENTION 
   The above mentioned problems and other problems are addressed by the present invention and will be understood by one skilled in the art upon reading and studying the following specification. An integrated circuit inductor compatible with integrated circuit manufacturing techniques is disclosed. 
   In one embodiment, an inductor capable of being fabricated from a plurality of conductive segments and interwoven with a substrate is disclosed. In an alternate embodiment, a sense coil capable of measuring the magnetic field or flux produced by an inductor comprised of a plurality of conductive segments and fabricated on the same substrate as the inductor is disclosed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a cutaway view of some embodiments of an inductor of the present invention. 
       FIG. 1B  is a top view of some embodiments of the inductor of FIG.  1 A. 
       FIG. 1C  is a side view of some embodiments of the inductor of FIG.  1 A. 
       FIG. 2  is a cross-sectional side view of some embodiments of a highly conductive path including encapsulated magnetic material layers. 
       FIG. 3A  is a perspective view of some embodiments of an inductor and a spiral sense inductor of the present invention. 
       FIG. 3B  is a perspective view of some embodiments of an inductor and a non-spiral sense inductor of the present invention. 
       FIG. 4  is a cutaway perspective view of some embodiments of a triangular coil inductor of the present invention. 
       FIG. 5  is a top view of some embodiments of an inductor coupled circuit of the present invention. 
       FIG. 6  is diagram of a drill and a laser for perforating a substrate. 
       FIG. 7  is a block diagram of a computer system in which embodiments of the present invention can be practiced. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     FIG. 1A  is a cutaway view of some embodiments of inductor  100  of the present invention. Inductor  100  includes substrate  103 , a plurality of conductive segments  106 , a plurality of conductive segments  109 , and magnetic film layers  112  and  113 . The plurality of conductive segments  109  interconnect the plurality of conductive segments  106  to form highly conductive path  114  interwoven with substrate  103 . Magnetic film layers  112  and  113  are formed on substrate  103  in core area  115  of highly conductive path  114 . 
   Substrate  103  provides the structure in which highly conductive path  114  that constitutes an inductive coil is interwoven. Substrate  103 , in one embodiment, is fabricated from a crystalline material. In another embodiment, substrate  103  is fabricated from a single element doped or undoped semiconductor material, such as silicon or germanium. Alternatively, substrate  103  is fabricated from gallium arsenide, silicon carbide, or a partially magnetic material having a crystalline or amorphous structure. Substrate  103  is not limited to a single layer substrate. Multiple layer substrates, coated or partially coated substrates, and substrates having a plurality of coated surfaces are all suitable for use in connection with the present invention. The coatings include insulators, ferromagnetic materials, and magnetic oxides. Insulators protect the inductive coil and separate the electrically conductive inductive coil from other conductors, such as signal carrying circuit lines. Coatings and films of ferromagnetic materials, such as magnetic metals, alloys, and oxides, increase the inductance of the inductive coil. 
   Substrate  103  has a plurality of surfaces  118 . The plurality of surfaces  118  is not limited to oblique surfaces. In one embodiment, at least two of the plurality of surfaces  118  are parallel. In an alternate embodiment, a first pair of parallel surfaces are substantially perpendicular to a second pair of surfaces. In still another embodiment, the surfaces are planarized. Since most integrated circuit manufacturing processes are designed to work with substrates having a pair of relatively flat or planarized parallel surfaces, the use of parallel surfaces simplifies the manufacturing process for forming highly conductive path  114  of inductor  100 . 
   Substrate  103  has a plurality of holes, perforations, or other substrate subtending paths  121  that can be filled, plugged, partially filed, partially plugged, or lined with a conducting material. In  FIG. 1A , substrate subtending paths  121  are filled by the plurality of conducting segments  106 . The shape of the perforations, holes, or other substrate subtending paths  121  is not limited to a particular shape. Circular, square, rectangular, and triangular shapes are all suitable for use in connection with the present invention. The plurality of holes, perforations, or other substrate subtending paths  121 , in one embodiment, are substantially parallel to each other and substantially perpendicular to substantially parallel surfaces of the substrate. 
   Highly conductive path  114  is interwoven with a single layer substrate or a multilayer substrate, such as substrate  103  in combination with magnetic film layers  112  and  113 , to form an inductive element that is at least partially embedded in the substrate. If the surface of the substrate is coated, for example with magnetic film  112 , then conductive path  114  is located at least partially above the coating, pierces the coated substrate, and is interlaced with the coated substrate. 
   Highly conductive path  114  has an inductance value and is in the shape of a coil. The shape of each loop of the coil interlaced with the substrate is not limited to a particular geometric shape. For example, circular, square, rectangular, and triangular loops are suitable for use in connection with the present invention. 
   Highly conductive path  114 , in one embodiment, intersects a plurality of substantially parallel surfaces and fills a plurality of substantially parallel holes. Highly conductive path  114  is formed from a plurality of interconnected conductive segments. The conductive segments, in one embodiment, are a pair of substantially parallel rows of conductive columns interconnected by a plurality of conductive segments to form a plurality of loops. 
   Highly conductive path  114 , in one embodiment, is fabricated from a metal conductor, such as aluminum, copper, or gold or an alloy of a such a metal conductor. Aluminum, copper, or gold, or an alloy is used to fill or partially fill the holes, perforations, or other paths subtending the substrate to form a plurality of conductive segments. Alternatively, a conductive material may be used to plug the holes, perforations, or other paths subtending the substrate to form a plurality of conductive segments. In general, higher conductivity materials are preferred to lower conductivity materials. In one embodiment, conductive path  114  is partially diffused into the substrate or partially diffused into the crystalline structure. 
   For a conductive path comprised of segments, each segment, in one embodiment, is fabricated from a different conductive material. An advantage of interconnecting segments fabricated from different conductive materials to form a conductive path is that the properties of the conductive path are easily tuned through the choice of the conductive materials. For example, the internal resistance of a conductive path is increased by selecting a material having a higher resistance for a segment than the average resistance in the rest of the path. In an alternate embodiment, two different conductive materials are selected for fabricating a conductive path. In this embodiment, materials are selected based on their compatibility with the available integrated circuit manufacturing processes. For example, if it is difficult to create a barrier layer where the conductive path pierces the substrate, then the conductive segments that pierce the substrate are fabricated from aluminum. Similarly, if it is relatively easy to create a barrier layer for conductive segments that interconnect the segments that pierce the substrate, then copper is used for these segments. 
   Highly conductive path  114  is comprised of two types of conductive segments. The first type includes segments subtending the substrate, such as conductive segments  106 . The second type includes segments formed on a surface of the substrate, such as conductive segments  109 . The second type of segment interconnects segments of the first type to form highly conductive path  114 . The mid-segment cross-sectional profile  124  of the first type of segment is not limited to a particular shape. Circular, square, rectangular, and triangular are all shapes suitable for use in connection with the present invention. The mid-segment cross-sectional profile  127  of the second type of segment is not limited to a particular shape. In one embodiment, the mid-segment cross-sectional profile is rectangular. The coil that results from forming the highly conductive path from the conductive segments and interweaving the highly conductive path with the substrate is capable of producing a reinforcing magnetic field or flux in the substrate material occupying the core area of the coil and in any coating deposited on the surfaces of the substrate. 
     FIG. 1B  is a top view of  FIG. 1A  with magnetic film  112  formed on substrate  103  between conductive segments  109  and the surface of substrate  103 . Magnetic film  112  c(oats or partially coats the surface of substrate  103 . In one embodiment, magnetic film  112  is a magnetic oxide. In an alternate embodiment, magnetic film  112  is one or more layers of a magnetic material in a plurality of layers formed on the surface of substrate  103 . 
   Magnetic film  112  is formed on substrate  103  to increase the inductance of highly conductive path  114 . Methods of preparing magnetic film  112  include evaporation, sputtering, chemical vapor deposition, laser ablation, and electrochemical deposition. In one embodiment, high coercivity gamma iron oxide films are deposited using chemical vapor pyrolysis. When deposited at above 500 degrees centigrade these films are magnetic gamma oxide. In an alternate embodiment, amorphous iron oxide films are prepared by the deposition of iron metal in an oxygen atmosphere (10 −4  torr) by evaporation. In another alternate embodiment, an iron-oxide film is prepared by reactive sputtering of an Fe target in Ar+O 2  atmosphere at a deposition rate of ten times higher than the conventional method. The resulting alpha iron oxide films are then converted to magnetic gamma type by reducing them in a hydrogen atmosphere. 
     FIG. 1C  is a side view of some embodiments of the inductor of  FIG. 1A  including substrate  103 , the plurality of conductive segments  106 , the plurality of conductive segments  109  and magnetic films  112  and  113 . 
     FIG. 2  is a cross-sectional side view of some embodiments of highly conductive path  203  including encapsulated magnetic material layers  206  and  209 . Encapsulated magnetic material layers  206  and  209 , in one embodiment, are a nickel iron alloy deposited on a surface of substrate  212 . Formed on magnetic material layer layers  206  and  209  are insulating layers  215  and  218  and second insulating layers  221  and  224  which encapsulate highly conductive path  203  deposited on insulating layers  215  and  218 . Insulating layers  215 ,  218 ,  221  and  224 , in one embodiment are formed from an insulator, such as polyimide. In an alternate embodiment, insulating layers  215 ,  218 ,  221 , and  224  are an inorganic oxide, such as silicon dioxide or silicon nitride. The insulator may also partially line the holes, perforations, or other substrate subtending paths. The purpose of insulating layers  215  and  218 , which in one embodiment are dielectrics, is to electrically isolate the surface conducting segments of highly conductive path  203  from magnetic material layers  206  and  209 . The purpose of insulating layers  221  and  224  is to electrically isolate the highly conductive path  203  from any conducting layers deposited above the path  203  and to protect the path  203  from physical damage. 
   The field created by the conductive path is substantially parallel to the planarized surface and penetrates the coating. In one embodiment, the conductive path is operable for creating a magnetic field within the coating, but not above the coating. In an alternate embodiment, the conductive path is operable for creating a reinforcing magnetic field within the film and within the substrate. 
   FIG.  3 A and  FIG. 3B  are perspective views of some embodiments of inductor  301  and sense inductors  304  and  307  of the present invention. In one embodiment, sense inductor  304  is a spiral coil and sense inductor  307  is a test inductor or sense coil embedded in the substrate. Sense inductors  304  and  307  are capable of detecting and measuring reinforcing magnetic field or flux  309  generated by inductor  301 , and of assisting in the calibration of inductor  301 . In one embodiment, sense inductor  304  is fabricated on one of the surfaces substantially perpendicular to the surfaces of the substrate having the conducting segments, so magnetic field or flux  309  generated by inductor  301  is substantially perpendicular to sense inductor  304 . Detachable test leads  310  and  313  in FIG.  3 A and detachable test leads  316  and  319  in  FIG. 3B  are capable of coupling sense inductors  304  and  307  to sense or measurement circuits. When coupled to sense or measurement circuits, sense inductors  304  and  307  are decoupled from the sense or measurement circuits by severing test leads  310 ,  313 ,  316 , and  319 . In one embodiment, test leads  310 ,  313 ,  316 , and  316  are severed using a laser. 
   In accordance with the present invention, a current flows in inductor  301  and generates magnetic field or flux  309 . Magnetic field or flux  309  passes through sense inductor  304  or sense inductor  307  and induces a current in spiral sense inductor  304  or sense inductor  307 . The induced current can be detected, measured and used to deduce the inductance of inductor  301 . 
     FIG. 4  is a cutaway perspective view of some embodiments of triangular coil inductor  400  of the present invention. Triangular coil inductor  400  comprises substrate  403  and triangular coil  406 . An advantage of triangular coil inductor  400  is that it saves at least a process step over the previously described coil inductor. Triangular coil inductor  400  only requires the construction of three segments for each coil of inductor  400 , where the previously described inductor required the construction of four segments for each coil of the inductor. 
     FIG. 5  is a top view of some embodiments of an inductor coupled circuit  500  of the present invention. Inductor coupled circuit  500  comprises substrate  503 , coating  506 , coil  509 , and circuit or memory cells  512 . Coil  509  comprises a conductive path located at least partially above coating  506  and coupled to circuit or memory cells  512 . Coil  509  pierces substrate  503 , is interlaced with substrate  503 , and produces a magnetic field in coating  506 . In an alternate embodiment, coil  509  produces a magnetic field in coating  506 , but not above coating  506 . In one embodiment, substrate  503  is perforated with a plurality of substantially parallel perforations and is partially magnetic. In an alternate embodiment, substrate  503  is a substrate as described above in connection with FIG.  1 . In another alternate embodiment, coating  506  is a magnetic film as described above in connection with FIG.  1 . In another alternate embodiment, coil  509 , is a highly conductive path as described in connection with FIG.  1 . 
     FIG. 6  is a diagram of a drill  603  and a laser  606  for perforating a substrate  609 . Substrate  609  has holes, perforations, or other substrate  609  subtending paths. In preparing substrate  609 , in one embodiment, a diamond tipped carbide drill is used bore holes or create perforations in substrate  609 . In an alternate embodiment, laser  606  is used to bore a plurality of holes in substrate  609 . In a preferred embodiment, holes, perforations, or other substrate  609  subtending paths are fabricated using a dry etching process. 
     FIG. 7  is a block diagram of a system level embodiment of the present invention. System  700  comprises processor  705  and memory device  710 , which includes memory circuits and cells, electronic circuits, electronic devices, and power supply circuits coupled to inductors of one or more of the types described above in conjunction with  FIGS. 1A-5 . Memory device  710  comprises memory array  715 , address circuitry  720 , and read circuitry  730 , and is coupled to processor  705  by address bus  735 , data bus  740 , and control bus  745 . Processor  705 , through address bus  735 , data bus  740 , and control bus  745  communicates with memory device  710 . In a read operation initiated by processor  705 , address information, data information, and control information are provided to memory device  710  through busses  735 ,  740 , and  745 . This information is decoded by addressing circuitry  720 , including a row decoder and a column decoder, and read circuitry  730 . Successful completion of the read operation results in information from memory array  715  being communicated to processor  705  over data bus  740 . 
   Conclusion 
   Embodiments of inductors and methods of fabricating inductors suitable for use with integrated circuits have been described. In one embodiment, an inductor having a highly conductive path fabricated from a plurality of conductive segments, and including coatings and films of ferromagnetic materials, such as magnetic metals, alloys, and oxides has been described. In another embodiment, an inductor capable of being fabricated from a plurality of conductors having different resistances has been described. In an alternative embodiment, an integrated test or calibration coil capable of being fabricated on the same substrate as an inductor and capable of facilitating the measurement of the magnetic field or flux generated by the inductor and capable of facilitating the calibration the inductor has been described. 
   Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.