Patent Publication Number: US-2003234436-A1

Title: Semiconductor device with a spiral inductor and magnetic material

Description:
FIELD OF THE INVENTION  
       [0001] This invention relates generally to inductor structures, and more particularly to microelectronic or semiconductor devices including a planar spiral inductor with a core.  
       BACKGROUND OF THE INVENTION  
       [0002] An inductor is an impedance device typically including a coil, with or without a core, for introducing inductance and to an electronic circuit. Both transformers and inductive reactors are included within the meaning of “inductor.” Various inductors are shaped as coils wrapped on various core materials such as ferrites. The core multiplies the inductance of a given coil by the “permeability” of the core material. The core typically is in the shape of a rod or toroid.  
       [0003] To obtain very high inductance, the coil typically includes many turns. Winding the coil on a closed loop iron or ferrite core can further increase the inductance. To obtain as pure an inductance as possible the DC resistance of the winding should be reduced to a minimum. This can be accomplished by increasing the wire size, which increases the size of the choke. The size of the wire also determines the current handling capability of the choke, because the work done in forcing the current through a resistance is converted into heat and the resistance. Magnetic losses in an iron core also produce some heating which restricts any choke to a certain safe operating current. Coil windings must be insulated from the frame as well as from each other. Thicker insulation, which necessarily makes the choke more bulky, is typically used in applications where there&#39;s too high-voltage between the frame in the windings. These losses incurred in the iron core increases as the frequency increases. These inductors store energy in the magnetic field in the coil.  
       [0004] Microelectronic or semiconductor devices are typically fabricated from a semiconductor substrate over which patterned conductor layers are formed and separated by dielectric layers. As the microelectronic arts have advanced, integration levels and functionality levels have increased so that not only conventional microelectronic or semiconductor structures such as transistors, resistors, diodes, capacitors are fabricated in or for use with the semiconductor device, but less conventional structures such as inductors and have also been fabricated in or for use with the semiconductor or microelectronic device. In particular, in semiconductor or microelectronic devices that are intended to be employed with high frequency applications, such as mobile communications it is common to employing inductor structures within the semiconductor or microelectronic devices.  
       [0005] A variety of microelectronic conductor structures having desirable properties including enhanced Q values, have been disclosed in the prior art. For example, U.S. Pat. No. 6,002,161 discloses a semiconductor device including an inductor element which includes a first conductive film pattern of a spiral configuration formed on a major face of the semiconductor substrate. A second conductive film pattern of an insular configuration is electronically connected only to the first conductive film pattern through contact holes formed in the interlayer insulation film and extending in an overlapping relationship with the first conductive film pattern.  
       [0006] U.S. Pat. No. 5,977,854 discloses a LC filter including a substrate having a magnetic and dielectric material. The LC filter includes inductors having two three-dimensional spiral structures arranged so that the magnetic fluxes generated at the insides of the spiral structures are parallel and in mutually reversed directions. Plane plate capacitors are also provided between the two three-dimensional spiral structures.  
       [0007] U.S. Pat. No. 6,287,932 discloses a spiral inductor fabricated from a semiconductor substrate that provides a large inductance while occupying only a small surface area. A magnetic material is provided either above or below the inductor to increase the inductance of the inductor. Magnetic material also acts as a barrier that confines electronic noise generated in the spiral conductor to the area occupied by the spiral inductor. The inductance of a pair of stacked spiral inductors is increased by including a layer of magnetic material between the stacked spiral inductors.  
       [0008] U.S. Pat. No. 4,613,843 discloses a planar magnetic transducer that utilizes thin film technology to form a coil on a ceramic substrates. A relatively powerful magnetic reluctance is positioned adjacent the substrate so a changing magnetic reluctance adjacent to the coil can be detected by a voltage change at the coil. The present invention provides alternatives to an advantages over the prior art.  
       SUMMARY OF THE INVENTION  
       [0009] One embodiment that the invention includes a semiconductor device including an inductor having a planar coil portion forming an opening in the center thereof and a core received in the opening and extending above and below the planar coil portion.  
       [0010] Another embodiment of the invention includes a semiconductor device having an inductor, planar coil portion with an opening, and a core including a magnetic material.  
       [0011] Another embodiment of the invention includes a semiconductor device having an inductor with a planar coil portion and an opening therein, a core received in the opening, and wherein the core includes a ferromagnetic material.  
       [0012] Another embodiment of the invention includes a semiconductor device with an inductor having a planar coil portion forming an opening in the center thereof, a coil received in the opening, and wherein the planar coil portion includes an electrically conductive line that encircles the core 2.5 times.  
       [0013] Another embodiment of the invention includes a semiconductor device including an inductor having a planar coil portion forming an opening in the center thereof and a coil received in the opening, and further including first and second inter-metal dielectric layers. The inductor further includes a first connecting leg of an electrically conductive material. The first connecting leg is connected to the planar coil portion. The planar coil portion being formed in the first inter-metal dielectric layer and the first connecting leg being in the second inter-metal dielectric layer.  
       [0014] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening, and a first connecting leg connected to the planar coil portion, and a second connecting leg connected to the planar coil portion.  
       [0015] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening, and a first connecting leg connected to the planar portion, and a second connecting leg connected to the planar portion, and an electrically conductive bump connected to the second connecting leg.  
       [0016] Another embodiment of the invention includes a semiconductor device including an inductor having a planar coil portion forming an opening in the center thereof and a core received in the opening, and further including first and second inter-metal dielectric layers. The inductor further includes a first connecting leg of an electrically conductive material. The first connecting leg is connected to the planar coil portion. The planar coil portion is in the first inter-metal dielectric layer and the first connecting leg being in the second inter-metal dielectric layer, and an electrically conductive plug extending from the first connecting leg to the planar coil portion.  
       [0017] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening, and a first connecting leg connected to the planar portion, and a second connecting leg connected to the planar portion, and an electrically conductive line connected to the second connecting leg.  
       [0018] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening, and a first inter-metal dielectric layer adjacent a second inter-metal dielectric layer adjacent a third inter-metal dielectric layer, and wherein the core extends through the first, second and third inter-metal dielectric layers.  
       [0019] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening and extending above and below the planar coil portion, and a inter-metal dielectric layer and at least a portion of the core being received in the inter-metal dielectric layer.  
       [0020] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening and extending above and below the coil portion, a first and second inter-metal dielectric layer, and the inductor further including a first connecting leg including an electrically conductive material, and wherein the first connecting leg is connected to the planar coil portion, and wherein the planar coil portion is in the first inter-metal dielectric layer and the first connecting leg is in the second inter-metal dielectric layer, and the inductor further including a second connecting leg connected to the planar coil portion, an electrically conductive bump connected to the second connecting leg, and further including an upper dielectric layer, and wherein the planar coil portion is positioned in the upper dielectric layer, the electrically conductive bump positioned over the upper dielectric layer, the core having an upper surface above the upper dielectric layer, and the electrically conductive bump having an upper surface above the upper surface of the core.  
       [0021] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening and extending above and below the planar coil portion, and wherein the core has a substantially square cross-section.  
       [0022] Another embodiment of the invention includes a semiconductor device having an inductor including a planar coil portion forming an opening in the center thereof and a core received in the opening and extending above and below the planar coil portion, and the core having a substantially square cross-section, and the planar coil portion including a plurality of straight segments connected together to encircle the core.  
       [0023] These and other objects, features and advantages of the present invention will become apparent from the following brief description of the drawings, detailed description of the preferred embodiments, and appended claims and drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0024]FIG. 1 is a plan view of a semiconductor device including an inductor and magnetic core according to one embodiment of the present invention; and  
     [0025]FIG. 2 is a sectional view of a semiconductor device including an inductor and magnetic core according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0026]FIG. 1 is plan view of a semiconductor device  10  having a body portion  12  and an inductor  11  formed therein. The inductor  11  includes a planar coil portion  14  forming a central opening (or window)  15  in the center of the coil. The inductor  11  also includes a core  16  positioned in the opening  15  in the planar coil portion  14 . In a preferred embodiment the core  16  is a magnetic material, preferably a ferromagnetic material. The core  16  may have a variety of configurations, but preferably as shown in FIG. 1, has a square or rectangular shaped cross-section. The core  16  includes first, second, third, and fourth sides  30 ,  32 ,  34 ,  36 . The inductor  11  includes a first connecting leg  18  that is connected to the planar coil portion  14  at the start of a first coil segment  24   a  that is closest to the first side  30  of the core  16 . The first coil segment  24   a  starts about midway along the first side  30  of the core  16 . The first coil segment  24   a  connects to a second coil segment  24   b  that runs closest to and along the length of the second side  32  of the core  16 . The second coil segment  24   b  is connected to an a third coil segment  24   c  that runs closest to and along the third side  34  of the core  16 . The third coil segment  24   c  is connected to a fourth coil segment  24   d  that runs closest to and along the fourth side  36  of the core  16 .  
     [0027] The fourth coil segment  24   d  is connected to a fifth coil segment  26   a  that runs nearest the first coil segment  24   a  and along in the first side  30  of a core  16 . The fifth coil segment  26   a  is connected to a sixth coil segment  26   b  that runs nearest and along the second coil segment  24   b . The sixth coil segment  26   b  is connected to a seventh coil segment  26   c  that runs nearest and along in the third coil segment  24   c . The seventh coil segment  26   c  is connected to an eighth coil segment  26   d  that runs nearest and along the fourth coil segment  24   d.    
     [0028] The eighth coil segment  26   d  is connected to a ninth coil segment  28   a  that is nearest and runs along the fifth coil segment  26   a . The ninth coil segment  28   a  is connected to a tenth coil segment  28   b  that is nearest and runs along the sixth coil segment  26   b . The tenth coil segment  28   c  is connected to an eleventh coil segment that is nearest and runs along the seventh coil segment  26   c  and terminates at about the midway point of the seventh coil segment  26   c . A second connecting leg  20  may be attached to the eleventh coil segment  28   c . The first through eleventh coil segments of the planar coil portion  14  are formed all in the same plane and provide 2.5 turns around the core  16 . An electrically conductive bump (preferably a solder bump) or an electrically conductive line (not shown) may be attached to the second connecting leg  20  as will be described hereafter in FIG. 2. Other electrically conductive bumps or electrically conductive lines  38  may be provided on the body portion  12  of the semiconductor device  10 .  
     [0029]FIG. 2 is a sectional view of one embodiment of the present invention which includes a semiconductor device  10  having an inductor  11 . The semiconductor device  10  includes a body portion  12  which may include a silicon based substrate  46  into which a N or P-well is formed as well as a shallow trench isolation region  50 . A discrete device  52  may be formed in portions of the silicon based substrate  46 . An interlayer dielectric  58  may be formed over the discrete devices  52  and electrically conductive plugs  60  may be formed through the interlayer dielectric  58  connecting to active regions  54 ,  56  of the discrete device  52 . A first layer metallization  62  may be formed over the interlayer dielectric  58 . A first inter-metal dielectric  64  may be formed over the first metallization layer  62  and electrically conductive plugs  66  may be formed through the first inter-metal dielectric layer  64  down to the first metallization layer  62 . A second inter-metal dielectric  68  may be formed over the first inter-metal dielectric  64 . A second inter-metal dielectric  70  may be formed over the second metallization  68  and a plug  72  formed through the second inter-metal dielectric  70  down to a second metallization layer  68 . A third metallization layer  74  may be formed over the second inter-metal dielectric layer  70 . A third inter-metal dielectric  76  may be formed over the third metallization  76  and a plug  78  formed through the third inter-metal dielectric  76  down to the third metallization  74 . A fourth metallization  18  may be formed over the third inter-metal dielectric layer  76 . A fourth inter-metal dielectric layer  80  may be formed over the third metallization layer  18  and plugs  82 ,  44  may be formed through the fourth inter-metal dielectric layer  80  down to the fourth metallization layer  18 . A fifth metallization layer  84  may be provided over the fourth inter-metal dielectric layer  80 . A fifth inter-metal dielectric layer  86  may be formed over the fifth metallization  84  and a plug  88  formed through the fifth inter-metal dielectric layer  86  down to the fifth metallization layer  84 . The plug  88  may be connected to electrically conductive bump or electrically conductive layer  38  on top of the fifth inter-metal dielectric layer  86 .  
     [0030] The inductor  11  includes the fourth metallization layer  18  that is connected through plug  44  to the first coil segment  24   a  of the planar coil portion  14 . The first through eleventh coil segments of the coil portion  14  are formed in the fifth inter-metal dielectric layer  86 . The planar coil portion  14  may be formed by any of a variety of methods known to those skilled in the art including electroplating or screen printing an electrically conductive material such as copper into openings formed in an inter-metal dielectric layer or on top of an inter-metal dielectric layer or passivation layer. Preferably the core  16  extends above the planar coil portion  14  and has an upper surface  42  which rises above the upper surfaces of each of the coil segments of the planar coil portion  14 . The core  16  may also extend substantially below the planar coil portion  14 , preferably extending through the fifth, fourth, and third inter-metal dielectric layers  86 ,  80  and  76  and includes a lower surface  90  that rest over the second inter-metal dielectric layer  70 . The core  16  may be formed by a electroplated magnetically soft alloys such as permalloy (Ni 8 OFe 2 O), orthnol (Ni 5 OFe 5 O), amorphous CoFeCu, supermalloy (NiFeMo), and polymer ferite materials into openings formed in each of the inter-metal dielectric layers as desired. Polyimide filled NiZn and MnZn ferrites may be screen printed into openings formed in each of the inter-metal dielectric layers as desired. Preferably the electrically conductive bumps or electrically conductive lines  38  include an upper surface  40  that is above the upper surface  42  of the core  16 .  
     [0031] The inductance increase due to the ferromagnetic core  16  will provide a substantial increase in the Q factor. The die size of the semiconductor device may be deceased due to the replacement of oxide with the ferromagnetic core  16 .