Patent Publication Number: US-2017352458-A1

Title: Planar coil

Description:
The invention relates to coils, individual coils as well as two or more coils arranged one over the other or a coil in combination with a sensor, which may be integrated into planar semiconductor technology. 
     Spiral-shaped coils that are shown in U.S. Pat. No. 6,114,937, for example, are typically produced from two metal layers. Thus, a spiral-shaped metal line can be formed from a first metal layer. In order to contact the inner end of the metal line, underpass contacts, for example, that are arranged below the metal line can be used. Underpass contacts can be formed by a second metal layer and can be connected, for example, to the inner end of the metal line by means of vias filled with metal. 
     Taken from DE10 2012 018 013,  FIG. 3  is partially incorporated as prior art into the present description as  FIG. 1A . The planar coil  10  known from this prior art consists of a first metal layer and includes several turns  16  that are arranged to be spiral-shaped. As also shown in section in  FIG. 1B , the electric supply into the centre  10   a  of the coil  10  takes place by means of a via contact  12  that is arranged between the first metal layer  11  and a second metal layer  15 . In the embodiment of the prior art in  FIGS. 1A and 1B , the electric supply takes place via a supply line  14  that has been formed in the second metal layer  15 . The supply line  14  in the second metal layer  15  runs below the coil  10  to the centre  10   a  of the coil, wherein the supply line  14  partially crosses the coil  10 , or crosses some turns  16  of the coil  10 . 
     However, the inventors of the present application have recognised that the vias or via contacts contribute to the total resistance of the coil and may also limit the maximum current-carrying capacity of the coil. The second metal layers and the vias or via contacts also enlarge the vertical extension or the total thickness of an individual coil, which may become noticeable, in particular in an arrangement of several spiral-shaped coils above one another. 
     The inventors have also recognised that, in spiral-shaped coils, the individual turns of the coil are arranged in series. Thus, a total resistance of the coil results from the sum of the resistance per turn. An increase of inductivity of the coil due to an increase in the number of turns thus results in a higher total resistance of the coil. 
     Starting from the prior art, the object of the invention is to make it possible to produce an improved coil which can be integrated into planar semiconductor technology. 
     This and other problems may be solved, for example, by the features specified in claims  1 ,  14 ,  15  and  16 . 
     Advantages of certain exemplary embodiments of this invention include a reduction of the vertical extension of a coil, for example by forming the coil and the supply lines for supplying current to the coil from a metal layer. Thus, individual planar coils may be produced, for example from one metal layer. Furthermore, two or more coils may be arranged above one another, wherein the vertical extension or the total thickness of the individual coils may be reduced. The individual coils in this arrangement may, for example, be contacted by a single wiring plane per coil. 
     In certain exemplary embodiments, the coil may include a number of turns that are arranged in parallel, such as for example at least two turns arranged in parallel. As a result of the parallel arrangement of a number of turns, the total resistance of the coil may be decreased, whereby, with equally applied voltage, an increased current may flow through the coil. This increased current generates an increased magnetic flux density. By increasing the number of parallel arranged turns, the total resistance of the coil may be reduced. 
     In certain exemplary embodiments, instead of or in addition to increasing a number of turns, the width of a or each turn of the coil may be increased. The ratio between the thickness and the width of a or each turn may encompass a range of about 1:25 to 1:5. By increasing the width of one turn, the cross-sectional surface of the respective turn may be increased, which may lead to a reduction of the resistance of the respective turn. The turn of the coil may be formed by a conductor track. The thickness of a turn may correspond to the thickness of the conductor track and/or the width of the turn may correspond to the width of the conductor track. The width of the turn is therefore to be distinguished from the total diameter of the turn or the coil. 
     Further advantageous embodiments of the subject matter of claims  1 ,  14 ,  15  and  16  are specified in the s dependent claims. 
    
    
     
       The invention will now be described by means of different exemplary embodiments of the invention with reference to the accompanying drawings, which show: 
         FIG. 1A  as prior art, a planar, spiral-shaped coil made of a first metal layer, in which the supply into the centre of the coil takes place via a second metal layer and a via contact, 
         FIG. 1B  a cross-section of the coil of  FIG. 1A  along the dotted line A-A, 
         FIG. 2  a planar coil formed of a metal layer, in which a number of turns having the same width are concentrically arranged and electrically arranged in parallel by supply lines for supplying current to the coil, 
         FIG. 3  a planar coil formed of a metal layer, in which a number of turns having different widths are concentrically arranged and electrically arranged in parallel by supply lines for supplying current to the coil, 
         FIG. 4A  a planar coil having one turn, in which the supply lines are connected to the ends of the turn and the turn and the supply lines are formed from a metal layer, 
         FIG. 4B  a cross-section of the turn of the coil of  FIG. 4A  along the dotted line C-C, 
         FIG. 5  a front view of the coil of  FIG. 2 ,  FIG. 3  or  FIG. 4A , 
         FIG. 6A  an arrangement of two planar coils above one another, 
         FIG. 6B  an arrangement of two planar coils above one another and offset relative to each other, 
         FIG. 6C  an arrangement of a planar coil and a sensor. 
     
    
    
       FIG. 2  shows a first exemplary embodiment of a planar coil  20  that can be integrated into planar semiconductor technology, such as silicon semiconductor technology or CMOS silicon semiconductor technology, for example. The planar coil  20  in  FIG. 2  includes a number of turns  22 . Each turn  22  of the coil  20  is formed by a respective curved conductor track  23 . In the exemplary embodiment in  FIG. 2 , the coil  20  has four turns  22 , wherein the coil  20  may have more than four or less than four turns in other exemplary embodiments. For example, in other exemplary embodiments, the coil  20  may have only a single turn. 
     In the coil  20  shown in  FIG. 2 , the turns  22  are arranged to be concentric relative to one another. A first end of each turn  22  is connected to a first supply line  24   a  and a second end of each turn  22  is connected to a second supply line  24   b . By connecting the first and second ends of the turns  22  to respective first and second supply lines  24   a ,  24   b , the turns  22  are electrically arranged in parallel. The total resistance of the coil  20  decreases as a result of the parallel arrangement of the turns  22  and thus, the current that can flow through the coil  20 , with the same voltage being applied, is increased, wherein the current generates an increased magnetic flux density. As a result of an increase in the number of parallel arranged turns  22 , the total resistance of the coil may be further reduced. 
     In the coil  20  shown in  FIG. 2 , the first and second supply lines  24   a ,  24   b  of the turns  22  are arranged to extend outwardly. In this exemplary embodiment, the first and second supply lines  24   a ,  24   b  extend parallel to each other from the ends of the turns  22  to a region outside of the footprint of the turns  22 . 
     In  FIG. 2 , the width B of the conductor track  23  of each turn  22  is the same, wherein in other exemplary embodiments, the width of the conductor track  23  of the individual turns may be different. 
       FIG. 3  shows a further exemplary embodiment of a planar coil  30 , which is similar to the exemplary embodiment shown in  FIG. 2 . In the exemplary embodiment of  FIG. 3 , the conductor tracks  33  of the turns  32  have different widths B, wherein the width B of the conductor track  33  of the turn  32  that is arranged in the centre of the coil  30  is the smallest and the width B of the conductor track  33  of the turn  32  that is arranged on the outermost edge of the coil  30  is the greatest. In this exemplary embodiment, the width of the conductor track  33  of the turn  32  that is arranged on the outermost edge of the coil  30  corresponds to three times the width of the conductor track  33  of the turn  32  that is arranged in the centre of the coil  30 . For example, the conductor track  33  of the turn  32  that is arranged in the centre of the coil  30  may have a width of about 1 m and the conductor track  33  of the turn  32  that is arranged on the outermost edge of the coil  30  may have a width of about 3 μm. However, in other exemplary embodiments, the width B of the conductor track  33  of the turn that is arranged in the centre of the coil may encompass a range of 0.5 to 2 μm and the width B of the conductor track of the coil  32  that is arranged on the outermost edge of the coil  30  may encompass a range of 1.5 to 6 μm. In this exemplary embodiment, the width of the conductor tracks  33  of the individual turns  32  thus increases with the diameter of the turns  32 . However, in other exemplary embodiments, the width of the conductor tracks  33  of the turns  32  may decrease with the diameter of the turns. In the arrangement of the turns  32  of the coil  30  shown in  FIG. 3 , the turns  32  have different lengths. The different widths B of the conductor tracks  33  of the turns  32  may be used to compensate for the different lengths of the turns and to vary and/or adjust the resistance of each turn  32 . The current supply again takes place by means of supply lines  34   a ,  34   b  that are common for all turns  32  and are arranged to extend outwardly from the turns  32  in this exemplary embodiment. The first and second supply lines  34   a ,  34   b  also extend in parallel to each other from the ends of the turns  32  to a region outside the footprint of the turns  32 . 
     A further exemplary embodiment of a planar coil  40  is shown in  FIG. 4A . The coil  40  shown in  FIG. 4A  is similar to the coils  20 ,  30  shown in  FIG. 2  and  FIG. 3 . In contrast to the coils  20 ,  30  shown in the exemplary embodiment above, the coil  40  in this exemplary embodiment only has one turn  42 . As in the exemplary embodiments above, the single turn  42  is formed by a curved conductor track  43 . In comparison, for example, to the turns  22  of the coil  20  shown in  FIG. 2 , the width of the conductor track  43  in this exemplary embodiment is greater. The current supply to the coil  40  takes place by means of supply lines  44   a ,  44   b , wherein the first and second supply lines  44   a ,  44   b  are in turn arranged to extend outwardly from the turn  43 . 
     In this exemplary embodiment, the width of the conductor track  43  is greater than the width of the conductor tracks  23 ,  33  of the coils  20 ,  30  shown in  FIG. 2  and  FIG. 3 . In the exemplary embodiment of  FIG. 4A , the width B of the conductor track  43  is greater than a distance F between the first and second supply lines  44   a ,  44   b . For example, the width of the conductor track  43  of the coil  40  shown in  FIG. 4A  can correspond to about 25% of the total diameter E of the coil  40 . In other exemplary embodiments, the width of the conductor track may correspond, for example, to between 20′% and 35% of the total diameter of the coil. 
       FIG. 4B  shows a cross-section of the conductor track  43  of the turn  42  in this exemplary embodiment. As a result of the greater width B of the conductor track  43  in  FIG. 4A  and  FIG. 4B , the resistance of the single turn  42  is smaller than the resistance of an individual turn  22  in the coil  20  shown in  FIG. 2 , provided that the thickness D of the conductor tracks  23 ,  43  is the same. This means that, instead of or in addition to an increase in the number of turns, the width B of a or each turn of a coil may be increased in order to reduce the resistance of the coil. The ratio between the thickness D and the width B of the conductor track  43  in this exemplary embodiment may encompass, for example, a range of about 1:25 to 1:5. For example, the width B of the conductor track  43  of the coil  40  in  FIG. 4A  may encompass a range of about 5 to 100 μm, wherein the thickness D may encompass a range of about 0.2 to 20 μm. 
     In the exemplary embodiments of  FIG. 2 ,  FIG. 3  and  FIG. 4A , the or each turn  22 ,  32 ,  42  defines an angle of about 300° to 320°. The angle may be defined by means of the extent of the or each turn  22 ,  32 ,  42  from the first supply line  24   a ,  34   a ,  44   a  to the second supply line  24   b ,  34 ,  44   b . In other exemplary embodiments, the or each turn may define an angle of at least 270° and/or an angle of 350° at most. 
       FIG. 5  shows a schematic front view of the coil  20 ,  30 ,  40  shown in  FIG. 2 ,  FIG. 3  or  FIG. 4A . In the exemplary embodiments above, the turns  22 ,  32 ,  42  of the coils  20 ,  30 ,  40  and the first and second supply lines  24   a ,  24   b ,  34   a ,  34   b ,  44   a ,  44   b  are formed by a metal layer  26 ,  36 ,  46 . In  FIG. 5 , the turns  22 ,  32 ,  42  of the coil  20 ,  30 ,  40  and the first and second supply lines  24   a ,  24   b ,  34   a ,  34   b ,  44   a ,  44   b  substantially have a thickness D of the metal layer  26 ,  36 ,  46 . Thus, the vertical extension of the respective coil  20 ,  30 ,  40  or of the turn(s)  22 ,  32 ,  42  and the first and second supply lines  24   a ,  24   b ,  34   a ,  34   b ,  44   a ,  44   b  substantially correspond to the thickness D of the respective metal layer  26 ,  36 ,  46 . The thickness D of the metal layer  26 ,  36 ,  46  also determines a thickness D of the conductor track  23 ,  33 ,  43  of the or each of the turns  22 ,  32 ,  42 . 
     By forming the coils  20 ,  30 ,  40  and the corresponding first and second supply lines  24   a ,  24   b ,  34   a ,  34   b ,  44   a ,  44   b  by means of a metal layer  26 ,  36 ,  46 , no via contacts are necessary and the individual coils may be contacted, for example, on an outer region of each coil. Since the coils  20 ,  30 ,  40  in the exemplary embodiments above do not require any via contacts, the resistance of each coil  20 ,  30 ,  40  may be reduced. 
     The formation of the coils  20 ,  30 ,  40  and the first and second supply lines  24   a ,  24   b ,  34   a ,  34   b ,  44   a ,  44   b  by means of a metal layer  26 ,  36 ,  46  also allows for an arrangement of several planar coils above one another. 
       FIG. 6A  shows an exemplary embodiment of an arrangement  50  in which two coils  40  are shown as being arranged above one another, wherein in other exemplary embodiments more than two coils may be arranged above one another. 
     The coils  40  in  FIG. 6A  and  FIG. 6B  correspond to the coil  40  shown in  FIG. 4A . In other exemplary embodiments, the arrangement  50  can include, for example, the coils  20 ,  30  shown in  FIG. 2  and/or  FIG. 3 .  FIG. 6A  shows that the individual coils  40  are formed by a respective metal layer  46  and are arranged in or on an insulator layer  52 , wherein the insulator layer  52  of the upper coil  40  is arranged between the two coils  40  and, as a result, the two coils  40  are electrically insulated from each other. For example, the insulator layer  52  can be formed by an ILD (Inter Layer Dielectric) or via oxide. 
     In the exemplary embodiment shown in  FIG. 6B , the upper coil  40  is arranged to be offset by 90° relative to the lower coil  40 . As a result of this arrangement, the supply lines  44   a ,  44   b  of the upper coil  40  extend in a direction offset by 90° relative to the supply lines of the lower coil  40 . In other exemplary embodiments, other arrangements of the upper and lower coils could be provided. For example, the two coils may be arranged to be offset relative to one another by 180° or 270°. 
     The coils  40  shown in  FIG. 6A  and  FIG. 6B  can be the same or different. 
     Since each individual coil  40  in the exemplary embodiments of  FIG. 6A  and  FIG. 6B  are formed by a corresponding metal layer  46 , a wiring plane, for example, per coil  40  may be used in order to contact the individual coils  40 . By omitting the via contacts in such an arrangement, the number of necessary metal layers and thus, the vertical extension or total thickness of the arrangement and/or of each individual coil may be reduced. An arrangement of several planar coils  40  above one another may be used, for example, in semiconductor components, such as for example in semiconductor transformers. When the coils are used in semiconductor transformers, the respective coils  40  may be provided, for example, with a ferrite core that is integrated into the respective coils in order to increase the magnetic field produced by the coil. 
       FIG. 6C  shows a further exemplary embodiment of a coil arrangement  60 . The coil arrangement  60  in  FIG. 6C  is similar to the coil arrangement  50  in  FIG. 6A . The arrangement in  FIG. 6C  includes a coil  40  in combination with a sensor  64 , such as for example a Hall sensor  64 , wherein, in this exemplary embodiment, the coil  40  is arranged above the Hall sensor. In this exemplary arrangement  60 , the coil  40  may be used to generate the magnetic field and the Hall sensor  64  for detecting the magnetic field generated by the coil  40 . In other exemplary embodiments, the arrangement  60  may include, for example, the coil  20 ,  30  shown in  FIG. 2  or  FIG. 3 . In certain exemplary embodiments, the Hall sensor  64  may also be formed by a metal layer. 
     The coils  20 ,  30 ,  40  in the exemplary embodiments above may be formed, for example, from metal and/or metal alloys, which may include aluminium, tin, gold, silver, aluminium silicon, aluminium copper, aluminium silicon copper and/or copper. The metal layer of the coil  20 ,  30 ,  40  may be arranged, for example, in or on a non-conductor layer or insulator layer that is formed on a semiconductor substrate or wafer, such as for example germanium (Ge), silicon (Si), SOI (silicon on a non-conductor or “silicon-on-insulator”) or SOS (“silicon on sapphire”). In other exemplary embodiments, the semiconductor substrate may include, for example, silicon germanium (SiGe), gallium arsenide (GaAs), indium phosphide (InP), indium arsenide (InAs) or other III-V semiconductors. 
     An exemplary method for producing the coils  20 ,  30 ,  40  may include, for example, depositing the metal layer, photochemistry, etching of the semiconductor substrate, the Damascene process and/or photochemistry in combination with electroplating. 
     Although in the exemplary embodiments above the turns of the coils  20 ,  30 ,  40  are shown in a substantially square or rectangular shape, the turns of the coils may comprise other shapes in other exemplary embodiments, such as for example circular, elliptical or oval. 
     Although in the exemplary embodiments above the turns  22 ,  32  are arranged concentrically, the turns may also be arranged relative to one another in a different manner. For example, the turns may be arranged to be eccentrical relative to one another. 
     In the exemplary embodiments above, the supply lines  24   a ,  24   b ,  34   a ,  34   b ,  44   a ,  44   b  may be comprised in the respective coils  20 ,  30 ,  40 . In other exemplary embodiments, the supply lines may be provided separately from the coils. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               20  Coil according to a first exemplary embodiment 
               22  Turns of the coil  20   
               23  Conductor track of the turns  22   
               24   a  First supply line of the coil  20   
               24   b  Second supply line of the coil  20   
               26  Metal layer of the coil  20   
               30  Coil according to a second exemplary embodiment 
               32  Turns of the coil  30   
               33  Conductor track of the turns  32   
               34   a  First supply line of the coil  30   
               34   b  Second supply line of the coil  30   
               36  Metal layer of the coil  30   
               40  Coil according to a third exemplary embodiment 
               42  Turn of the coil  40   
               43  Conductor track of the turn  42   
               44   a  First supply line of the coil  40   
               44   b  Second supply line of the coil  40   
               46  Metal layer of the coil  40   
               50  Coil according to a fourth exemplary embodiment 
               52  Insulator layer of a fourth exemplary embodiment 
               60  Coil according to a fifth exemplary embodiment 
               62  Insulator layer of a fifth exemplary embodiment 
               64  Sensor 
             B Width of the conductor track  42  of the turn  42  or of the turns  22 ,  32   
             D Thickness of the metal layer  26 ,  36 ,  46  and/or the conductor track of the turn  42  or the turns  22 , 
             E Total diameter of the turn  42   
             F Distance between the first and second supply lines  44   a ,  44   b  of the coil  40