Patent Publication Number: US-11651887-B2

Title: Stacked and interleaved transformer layout

Description:
BACKGROUND 
     Transformers and transformer-based components, such as power splitters, combiners, and the like, can be used in millimeter (mm) wave integrated circuit design. One important parameter in design of a transformer structure is insertion loss of a coil (e.g., a primary coil, a secondary coil), which has a direct impact on an output power of a transmitter and/or a noise figure of a receiver. One type of transform structure is a stacked transformer structure. A stacked transformer structure relies on vertical (i.e., transverse) coupling between coils located primarily in different planes. Another type of transformer structure is an interleaved transformer structure. An interleaved transformer structure (also referred to as a planar transformer structure) relies on lateral (i.e., side) coupling between coils located primarily in the same plane. 
     SUMMARY 
     According to some possible implementations, a transformer structure may include a first coil having one or more turns; and a second coil having one or more turns, wherein a turn of the one or more turns of the first coil overlaps a turn of the one or more turns of the second coil in a lateral direction substantially along the turn of the first coil and in a vertical direction substantially along the turn of the first coil. 
     According to some possible implementations, a method may include forming a first coil having at least one turn; and forming a second coil having at least one turn, wherein a first portion of a turn of the first coil is formed to overlap a turn of the second coil in a first direction substantially along the first portion of the turn of the first coil, and wherein a second portion of the turn of the first coil is formed to overlap the turn of the second coil in a second direction substantially along the second portion of the turn of the first coil, wherein the second direction is perpendicular to the first direction. 
     According to some possible implementations, a semiconductor device may include a transformer structure including a first coil having one or more turns; and a second coil having one or more turns, wherein a turn of the one or more turns of the first coil overlaps a turn of the one or more turns of the second coil in a lateral direction and in a vertical direction substantially along the turn of the first coil. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A- 1 H  are diagrams associated with a first example implementation of a transformer structure that includes a stacked and interleaved architecture, as described herein. 
         FIGS.  2 A- 2 D  are diagrams associated with a second example implementation of a transformer structure that includes a stacked and interleaved architecture, as described herein. 
         FIGS.  3 A- 3 J  are diagrams associated with a third example implementation of a transformer structure that includes a stacked and interleaved architecture, as described herein. 
         FIG.  4    a flow chart of an example process for providing a transformer structure having a stacked and interleaved architecture, as described herein. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description of example implementations refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. 
     One factor that determines an amount of insertion loss of a transformer structure is coupling between a primary coil of the transformer structure and a secondary coil of the transformer structure. As a frequency of operation in which a transformer structure is used increases (e.g., to mm-wave frequencies and higher), a size of the transformer structure becomes smaller, which makes achieving a high coupling coefficient, and therefore low insertion loss, more difficult. Prior techniques for reducing insertion loss in a transformer structure include using a stacked structure, or an interleaved structure (e.g., with at least a required minimum spacing between transformer turns). Other options may also be possible, such as the use of a specially designed layout (e.g., a quadrafilar combiner), or a design based on differently sized transformer structures. 
     Generally, a manufacturing technology that provides a metal stack with two thick metal layers (e.g., having thicknesses equal to or greater than approximately 1 micron (μm)) is used for fabricating mm-wave integrated circuits. However, in some cases, a manufacturing technology may provide a metal stack having only a single thick metal layer. In such a case, a stacked structure is not feasible (e.g., since the stacked structure requires at least two thick metal layers to form the primary and secondary coils), and so an interleaved structure (e.g., in which the primary and secondary coils are formed on the single thick metal layer) is the typical candidate for realizing a transformer structure. A quality (Q) factor and electro-migration aspects benefit from the use of an interleaved structure. However, due to minimum spacing requirements (e.g., for an amount of space between turns of the coils), a transformer structure with an interleaved design cannot achieve low insertion loss for a certain primary and secondary inductance because the required spacing limits an achievable coupling between coils of the transformer structure. 
     Some implementations described herein provide a transformer structure having a stacked and interleaved design. In some implementations, a transformer structure with the stacked and interleaved design (herein referred to as stacked/interleaved transformer structure) may have a first coil and a second coil, where a turn of the first coil overlaps a turn of the second coil in both a lateral direction substantially along the turn of the first coil (e.g., to provide lateral coupling substantially along the turn of the first coil) and in a vertical direction substantially along the turn of the first coil (e.g., to provide vertical coupling substantially along the turn of the first coil). 
     In some implementations, the stacked/interleaved transformer structure reduces insertion loss and increases coupling coefficient between the primary coil and the secondary coil (e.g., as compared to a stacked structure alone, as compared to an interleaved structure alone). That is, by employing a combination of interleaved and stacked architectures, the stacked/interleaved transformer structure may gain advantages of both the stacked approach and the interleaved approach. Additionally, the stacked/interleaved transformer structure design described herein does not impact a size or a general structure of the primary or secondary coils, meaning that the stacked/interleaved transformer structure can be readily integrated into current integrated circuit designs. In some implementations, when used in a radar transceiver system, the stacked/interleaved transformer structure described herein may increase an output power of a transmitter and decrease a noise figure of a low noise amplifier, both of which impact a signal-to-noise ratio (SNR) of the radar transceiver system, meaning that the stacked/interleaved transformer structure can improve quality of a radar image. 
     In some implementations, the stacked/interleaved transformer structure includes an interleaved structure in which both the primary and secondary coils are formed on a thick metal layer. Further the stacked/interleaved transformer structure includes a stacked structure using an additional winding geometry, connected to either the primary coil or the secondary coil, that is formed on a thin (e.g., having a thickness that is less than approximately 1 μm) metal layer below the thick metal layer. Here, the combination of the stacked and interleaved architectures increases coupling between the primary and secondary coils. 
     Notably, the stacked/interleaved transformer structure may be particularly useful when a manufacturing technology provides a metal stack having a single thick metal layer. However, the stacked/interleaved transformer structure can be used in other scenarios, such as when a manufacturing technology provides a metal stack with two thick metal layers, and still provide the benefits described above. For example, when the manufacturing technology provides a metal stack with two thick metal layers, a coupling coefficient of the transformer structure can be increased by including a lateral winding in parallel to an upper turn to realize a stacked/interleaved transformer structure. 
       FIGS.  1 A- 1 H  are diagrams associated with a first example implementation of a transformer structure  100  that includes a stacked and interleaved architecture. In some implementations, the transformer structure  100  is integrated in a semiconductor device. In some implementations, the transformer structure  100  can be used for realization of coils in a combiner, a splitter, or the like, included in a power amplifier or another type of circuit (e.g., a low noise amplifier) in which low insertion loss and/or high magnetic coupling is desired. 
       FIG.  1 A  illustrates a two-dimensional (2D) plan view of the first example implementation of transformer structure  100 ,  FIG.  1 B  illustrates a three-dimensional (3D) view of the first example implementation of transformer structure  100 ,  FIG.  1 C  illustrates a 3D cross-section of the first example implementation of transformer structure  100 , and  FIG.  1 D  illustrates a 3D exploded view of the first example implementation of transformer structure  100 . 
     In some implementations, transformer structure  100  may include a first coil  102  having one or more turns and a second coil  104  having one or more turns. For example, as shown in  FIGS.  1 A- 1 D , the transformer structure  100  may include a first coil  102  and a second coil  104 , each with a single turn. Notably, in other implementations, the first coil  102  and/or the second coil  104  can have multiple turns, and the number of turns of the first coil  102  need not match the number of turns of the second coil  104 . In some implementations, the first coil  102  is a primary coil of the transformer structure  100  and the second coil  104  is a secondary coil of the transformer structure  100 . Alternatively, in some implementations, the first coil  102  is a secondary coil of the transformer structure  100  and the second coil  104  is a primary coil of the transformer structure  100 . 
     In some implementations, to provide the stacked and interleaved structure, a turn of the first coil  102  overlaps a turn of the second coil  104  in a lateral direction substantially along the turn of the first coil  102  and in a vertical direction substantially along the turn of the first coil  102 . For example, in some implementations, a turn of the first coil  102  overlaps a turn of the second coil  104  in the lateral direction along more than a quarter of the turn (i.e., 25% of a length of the turn) of the first coil  102  and overlaps the turn of the second coil  104  in the vertical direction along more than a quarter of the turn of the first coil  102 . In some implementations, as indicated in the cross-section of  FIG.  1 C , the overlap in the lateral direction is provided by a first portion  102   a  of the first coil  102 , while the overlap in the vertical direction is provided by a second portion  102   b  of the first coil  102 . 
     Notably, in the first example implementation, the first coil  102  is an outer coil of the transformer structure  100  and the second coil  104  is an inner coil of the transformer structure  100 . However, in another implementation, the first coil  102  may be the inner coil of the transformer structure  100  and the second coil  104  may be the inner coil of the transformer structure  100 . In such a case, the second portion  102   b  extends outward (e.g., from the inner coil toward the outer coil) rather than inward (e.g., from the outer coil toward the inner coil) as shown in the first example implementation of the transformer structure  100 . 
     In some implementations, the first portion  102   a  is formed from a first metal layer (e.g., a thick metal layer) of a metal stack and the second portion  102   b  is formed from a second metal layer (e.g., a thin metal layer, a metal layer that is second from the top) of the metal stack. Here, as illustrated in  FIG.  1 C , the first portion  102   a  can be connected to the second portion  102   b  substantially along the turn of the first coil  102  through a via structure  102   c  between the first metal layer and the second metal layer. In some implementations, the second coil  104  is formed from the first metal layer. In the first example implementation of transformer structure  100 , the first coil  102  is realized in the first metal layer and in the second metal layer (e.g., such that the first coil  102  extends below the second coil  104 ), while the second coil  104  is realized in the first metal layer. As a result of this stacked and interleaved structure, there will be lateral coupling and vertical coupling between the first coil  102  and the second coil  104  substantially along the turn of the first coil  102 . Furthermore, extension of the first coil  102  below the second coil  104  improves isolation of the second coil  104  from a substrate, while causing increasing coupling between the first coil  102  and the substrate. 
     Notably, addition of the parallel metal path on the first coil  102  (i.e., the second portion  102   b ) may cause a difference between a Q factor of the first coil  102  and the second coil  104 . However, in many applications, having equal Q factor on both the primary and secondary coils is not required. Furthermore, due to underpasses that are needed by the layout of the coil, the Q factor of a primary coil and a secondary coil in a conventional transformer structure layout are different in many cases. In some cases, the stacked/interleaved architecture of transformer structure  100  may not only not increase this difference in the Q factor, but may help to restore balance between the Q factors of the first coil  102  and the second coil  104 . Further, the stacked/interleaved transformer structure may have an increased parasitic capacitance that shifts a self-resonance frequency (SRF) by a small amount (e.g., on the order of a few gigahertz). However, the SRF is typically far beyond a frequency of operation of the transformer structure  100  and, therefore, such a shift in does not significantly impact performance of the transformer structure  100 . 
       FIGS.  1 E- 1 H  are diagrams illustrating examples of simulated improvements in transformer performance parameters provided by the first example implementation of the transformer structure  100  (e.g., in which the first coil  102  is the outer coil and the second coil  104  is the inner coil). In the examples associated with  FIGS.  1 E- 1 H , the first coil  102  is the secondary coil and the second coil  104  is the primary coil. In  FIGS.  1 E- 1 H , lines corresponding to performance parameters of the first example implementation of the transformer structure  100  are labeled with “TS 100 ,” and lines corresponding to performance parameters of a conventional transformer structure (a transformer structure having an interleaved structure only) are labeled with “ILTS.” 
       FIG.  1 E  illustrates an improvement in insertion loss provided by the first example implementation of transformer structure  100 . As shown in  FIG.  1 E , in a possible range of operation of transformer structure (e.g., between approximately 60 gigahertz (GHz) and approximately 100 GHz), the first example implementation of the transformer structure  100  may reduce insertion loss by approximately 0.18 decibels (dB) as compared to the conventional transformer structure. 
       FIG.  1 F  illustrates an improvement in a coupling coefficient (K) provided by the first example implementation of transformer structure  100 . As shown in  FIG.  1 F , the first example implementation of the transformer structure  100  may increase the coupling coefficient by approximately 0.06 (i.e., by approximately 9%) as compared to the conventional transformer structure. 
       FIG.  1 G  illustrates an improvement in Q factor matching of the primary and secondary coils provided by the first example implementation of transformer structure  100 . In  FIG.  1 G , the Q factor of the primary coil of the first example implementation of transformer structure  100  is identified as “TS 100   P ,” the Q factor of the secondary coil of the first example implementation of transformer structure  100  is identified as “TS 100   S ,” the Q factor of the primary coil of the conventional transformer structure is identified as “ILTS P ,” and the Q factor of the secondary coil of the conventional transformer structure is identified as “ILTS S .” As shown in  FIG.  1 G , in the first example implementation of the transformer structure  100 , the Q factors of the primary and secondary coils of the first example implementation of transformer structure  100  are more closely matched than the Q factors of the primary and secondary coils of the conventional transformer structure. 
       FIG.  1 H  illustrates an impact on inductance of the first example implementation of transformer structure  100 . In  FIG.  1 H , the inductance of the primary coil of the first example implementation of transformer structure  100  is identified as “TS 100   P ,” the inductance of the secondary coil of the first example implementation of transformer structure  100  is identified as “TS 100   S ,” the inductance of the primary coil of the conventional transformer structure is identified as “ILTS P ,” and the inductance of the secondary coil of the conventional transformer structure is identified as “ILTS S .” As shown in  FIG.  1 H , in the first example implementation of the transformer structure  100 , the inductance of the secondary coil of the first example implementation of the transformer structure  100  may be lower than the inductance of the secondary coil of the conventional transformer structure. Further, as shown, the primary and secondary coils of the first example implementation of transformer structure  100  are more closely matched than the inductance of the primary and secondary coils of the conventional transformer structure. 
     As indicated above,  FIGS.  1 A- 1 H  are provided as examples. Other examples may differ from what is described with regard to  FIGS.  1 A- 1 H . The number and arrangement of coils, turns, and layers shown in  FIGS.  1 A- 1 H  are provided as an example. In practice, there may be additional turns, additional layers, fewer turns, fewer layers, different coils, different turns, different layers, differently shaped coils, differently shaped turns, differently shaped layers, differently arranged coils, differently arranged turns, or differently arranged layers than those shown in  FIGS.  1 A- 1 H . Further, the dimensions of coils, turns, and layers shown in  FIGS.  1 A- 1 H  are provided as an example. In practice, the coils, turns, and/or layers may have different dimensions or different relative dimensions than those shown in  FIGS.  1 A- 1 H . 
       FIGS.  2 A- 2 D  are diagrams illustrating improvements in transformer performance parameters provided by a second example implementation of the transformer structure  100 . In the second example implementation of the transformer structure  100 , the first coil  102  is the inner coil and the second coil  104  is the outer coil (e.g., such that the second portion  102   b  of the first coil  102  extends outward beneath the second coil  104 ). In the examples associated with  FIGS.  2 A- 2 D  the first coil  102  is the primary coil and the second coil  104  is the secondary coil. In  FIGS.  2 A- 2 D , lines corresponding to performance parameters of the second example implementation of the transformer structure  100  are labeled with “TS 100 ,” and lines corresponding to performance parameters of a conventional transformer structure (a transformer structure having an interleaved structure only) are labeled with “ILTS.” 
       FIG.  2 A  illustrates an improvement in insertion loss provided by the second example implementation of transformer structure  100 . As shown in  FIG.  2 A , in a possible range of operation of transformer structure (e.g., between approximately 60 GHz and approximately 100 GHz), the second example implementation of the transformer structure  100  may reduce insertion loss by approximately 0.30 dB as compared to the conventional transformer structure. 
       FIG.  2 B  illustrates an improvement in a coupling coefficient provided by the second example implementation of transformer structure  100 . As shown in  FIG.  2 B , the second example implementation of the transformer structure  100  may increase the coupling coefficient by approximately 0.07 (i.e., by approximately 10%) as compared to the conventional transformer structure. 
       FIG.  2 C  illustrates a change in Q factor of the primary and secondary coils provided by the second example implementation of transformer structure  100 . In  FIG.  2 C , the Q factor of the primary coil of the second example implementation of transformer structure  100  is identified as “TS 100   P ,” the Q factor of the secondary coil of the second example implementation of transformer structure  100  is identified as “TS 100   S ,” the Q factor of the primary coil of the conventional transformer structure is identified as “ILTS P ,” and the Q factor of the secondary coil of the conventional transformer structure is identified as “ILTS S .” As shown in  FIG.  2 C , in the second implementation of the transformer structure  100 , a difference in the Q factors of the primary and secondary coils of the second example implementation of transformer structure  100  may, at most frequencies, be larger than a difference between the Q factors of the primary and secondary coils of the conventional transformer structure. In some implementations, the difference between the Q factors associated with the second example implementation of the transformer structure  100  may be designed so as to provide a desired difference in Q factors. 
       FIG.  2 D  illustrates an impact on inductance of the second example implementation of transformer structure  100 . In  FIG.  2 D , the inductance of the primary coil of the second example implementation of transformer structure  100  is identified as “TS 100   P ,” the inductance of the secondary coil of the second example implementation of transformer structure  100  is identified as “TS 100   S ,” the inductance of the primary coil of the conventional transformer structure is identified as “ILTS P ,” and the inductance of the secondary coil of the conventional transformer structure is identified as “ILTS S .” As shown in  FIG.  2 D , in the second example implementation of the transformer structure  100 , the inductance of the primary coil of the second example implementation of the transformer structure may be lower than that of the primary coil of the conventional transformer structure across a range of operation, and the inductance of the secondary coil of the second example implementation of the transformer structure  100  may be lower than the inductance of the secondary coil of the conventional transformer structure across a majority of the range of operation. 
     As indicated above,  FIGS.  2 A- 2 D  are provided as examples. Other examples may differ from what is described with regard to  FIGS.  2 A- 2 D . 
       FIGS.  3 A- 3 J  are diagrams associated with a third example implementation of the transformer structure  100 . The third example implementation of the transformer structure  100  is a  2 : 1  transformer.  FIG.  3 A  illustrates a 2D plan view of the third example implementation of transformer structure  100 ,  FIG.  3 B  illustrates a 3D view of the third example implementation of transformer structure  100 ,  FIG.  3 C  illustrates a 3D cross-section of the third example implementation of transformer structure  100 , and FIG. 3D illustrates a 3D exploded view of the third example implementation of transformer structure  100 . Notably,  FIGS.  3 A -3D show half of a 1:2 power combiner. 
     In some implementations, transformer structure  100  may include a first coil  102  having one or more turns and a second coil  104  having one or more turns, as described above. For example, as shown in  FIGS.  3 A- 3 D , the transformer structure  100  may include a first coil  102  having one turn, and a second coil  104  having two turns. 
     In some implementations, as described above, to provide the stacked and interleaved structure, a turn of the first coil  102  overlaps a turn of the second coil  104  in a lateral direction substantially along the turn of the first coil  102  and in a vertical direction substantially along the turn of the first coil  102 . In some implementations, as indicated in the cross-section of  FIG.  3 C , the overlap in the lateral direction is provided by a first portion  102   a  of the first coil  102 , while the overlap in the vertical direction is provided by a second portion  102   b  of the first coil  102 . 
     Notably, in the third example implementation, the first coil  102  is a middle coil of the transformer structure  100  and the second coil  104  comprises an inner coil (forming a first turn) and an outer coil (forming a second turn) of the transformer structure  100 . As shown, the second portion  102   b  extends outward toward the outer coil of the second coil  104  in the third example implementation. However, in another implementation, the second portion  102   b  of the first coil  102  may extends inward (e.g., beneath the inner coil of the second coil  104 ). 
       FIGS.  3 E- 3 J  are diagrams illustrating examples of simulated improvements in transformer performance parameters provided by the third example implementation of the transformer structure  100  (e.g., a combiner). In the examples associated with  FIGS.  3 E- 3 J , the first coil  102  is the secondary coil and the second coil  104  is the primary coil. In  FIGS.  3 E- 3 J , lines corresponding to performance parameters of the third example implementation of the transformer structure  100  are labeled with “TS 100 ,” and lines corresponding to performance parameters of a conventional combiner transformer structure (a transformer structure having an interleaved structure only) are labeled with “ILTS.” 
       FIG.  3 E  illustrates an improvement in insertion loss provided by the third example implementation of transformer structure  100 . As shown in  FIG.  3 E , in a possible range of operation of transformer structure (e.g., between approximately 60 GHz and approximately 100 GHz), the third example implementation of the transformer structure  100  may reduce insertion loss by approximately 0.14 dB as compared to the conventional combiner transformer structure. 
       FIG.  3 F  illustrates an improvement in a coupling coefficient provided by the third example implementation of transformer structure  100 . As shown in  FIG.  3 F , the third example implementation of the transformer structure  100  may increase the coupling coefficient by approximately 8% as compared to the conventional combiner transformer structure. 
       FIG.  3 G  illustrates an improvement in Q factor matching of the primary and secondary coils provided by the third example implementation of transformer structure  100 . In  FIG.  3 G , the Q factor of the primary coil of the third example implementation of transformer structure  100  is identified as “TS 100   P ,” the Q factor of the secondary coil of the third example implementation of transformer structure  100  is identified as “TS 100   S ,” the Q factor of the primary coil of the conventional combiner transformer structure is identified as “ILTS P ,” and the Q factor of the secondary coil of the conventional combiner transformer structure is identified as “ILTS S .” As shown in  FIG.  3 G , in the third example implementation of the transformer structure  100 , the Q factors of the primary and secondary coils of the third example implementation of transformer structure  100  are more closely matched than the Q factors of the primary and secondary coils of the conventional combiner transformer structure. 
       FIG.  3 H  illustrates an impact on inductance of the third example implementation of transformer structure  100 . In  FIG.  3 H , the inductance of the primary coil of the third example implementation of transformer structure  100  is identified as “TS 100   P ,” the inductance of the secondary coil of the third example implementation of transformer structure  100  is identified as “TS 100   S ,” the inductance of the primary coil of the conventional combiner transformer structure is identified as “ILTS P ,” and the inductance of the secondary coil of the conventional combiner transformer structure is identified as “ILTS S .” As shown in  FIG.  3 H , in the third example implementation of the transformer structure  100 , the inductance of the secondary coil of the third example implementation of the transformer structure  100  may be lower than the inductance of the secondary coil of the conventional combiner transformer structure. 
       FIG.  3 I  illustrates an impact on scattering parameters a power amplifier that uses the third example implementation of transformer structure  100 . In  FIG.  3 I , scattering parameters S 21 , S 11 , and S 22  of the power amplifier that uses the third example implementation of transformer structure  100  are dashed lines labeled with “TS 100 ,” while scattering parameters S 21 , S 11 , and S 22  of a power amplifier that uses the conventional combiner transformer structure are solid lines labeled with “ILTS.” As shown in  FIG.  3 I , in the scattering parameters of the power amplifier that uses the third example implementation of transformer structure  100  do not differ significantly from the scattering parameters of the power amplifier that uses the conventional combiner transformer structure. 
       FIG.  3 J  illustrates an improvement in output power and power-added efficiency (PAE) of a power amplifier that uses the third example implementation of transformer structure  100 . In  FIG.  3 J , the output power of the power amplifier that uses the third example implementation of transformer structure  100  is identified as “TS 100   Pout ,” the PAE of the power amplifier that uses the third example implementation of transformer structure  100  is identified as “TS 100   PAE ,” the output power of a power amplifier that uses the conventional combiner transformer structure is identified as “ILTS Pout ,” and the PAE of the power amplifier that uses the conventional combiner transformer structure is identified as “ILTS SAE .” As shown in  FIG.  3 J , in the power amplifier that uses the third example implementation of the transformer structure  100 , both the output power and the PAE are higher than those of the power amplifier that uses the conventional combiner transformer structure. Thus, without changing the frequency centering of the power amplifier (as illustrated by the scattering parameters in  FIG.  3 I ) both output power and PAE are improved in the power amplifier that uses the third example implementation of transformer structure  100  as illustrated in  FIG.  3 J ). 
     As indicated above,  FIGS.  3 A- 3 J  are provided as examples. Other examples may differ from what is described with regard to  FIGS.  3 A- 3 J . The number and arrangement of coils, turns, and layers shown in  FIGS.  3 A- 3 J  are provided as an example. In practice, there may be additional turns, additional layers, fewer turns, fewer layers, different coils, different turns, different layers, differently shaped coils, differently shaped turns, differently shaped layers, differently arranged coils, differently arranged turns, or differently arranged layers than those shown in  FIGS.  3 A- 3 J . Further, the dimensions of coils, turns, and layers shown in  FIGS.  3 A- 3 J  are provided as an example. In practice, the coils, turns, and/or layers may have different dimensions or different relative dimensions than those shown in  FIGS.  3 A- 3 J . 
       FIG.  4    is a flow chart of an example process  400  for providing a stacked/interleaved transformer structure, as described herein. 
     As shown in  FIG.  4   , process  400  may include forming a first coil having at least one turn (block  410 ). For example, a first coil having at least one turn may be formed, as described above. 
     As further shown in  FIG.  4   , process  400  may include forming a second coil having at least one turn, where a first portion of a turn of the first coil is formed to overlap a turn of the second coil in a first direction substantially along the first portion of the turn of the first coil, and a second portion of the turn of the first coil is formed to overlap the turn of the second coil in a second direction substantially along the second portion of the turn of the first coil (block  420 ). For example, a second coil having at least one turn may be formed, as described above. In some implementations, a first portion of a turn of the first coil is formed to overlap a turn of the second coil in a first direction substantially along the first portion of the turn of the first coil. In some implementations, a second portion of the turn of the first coil is formed to overlap the turn of the second coil in a second direction substantially along the second portion of the turn of the first coil. In some implementations, the second direction is perpendicular to the first direction. 
     Process  400  may include additional implementations, such as any single implementation or any combination of implementations described below and/or in connection with one or more other processes described elsewhere herein. 
     In a first implementation, the first coil and the second coil are integrated in a semiconductor device. 
     In a second implementation, alone or in combination with the first implementation, the first portion of the turn of the first coil is formed to overlap the turn of the second coil in the first direction along at least a quarter of the turn of the first coil and the second portion of the turn of the first coil is formed to overlap the turn of the second coil in the second direction along the at least the quarter of the turn of the first coil. 
     In a third implementation, alone or in combination with one or more of the first and second implementations, the first coil is a primary coil of a transformer structure and the second coil is a secondary coil of the transformer structure. 
     In a fourth implementation, alone or in combination with one or more of the first through third implementations, the first coil is a secondary coil of a transformer structure and the second coil is a primary coil of the transformer structure. 
     In a fifth implementation, alone or in combination with one or more of the first through fourth implementations, the first portion of the turn of the first coil is formed from a first metal layer of a metal stack and the second portion of the turn of the first coil is formed from a second metal layer of the metal stack, the first portion of the turn of the first coil being connected to the second portion of the turn of the first coil substantially along the turn of the first coil. 
     In a sixth implementation, alone or in combination with one or more of the first through fifth implementations, the second coil is formed from the first metal layer. 
     Although  FIG.  4    shows example blocks of process  400 , in some implementations, process  400  may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in  FIG.  4   . Additionally, or alternatively, two or more of the blocks of process  400  may be performed in parallel. 
     The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the implementations. 
     As used herein, the term “component” is intended to be broadly construed as hardware, firmware, and/or a combination of hardware and software. 
     It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the implementations. Thus, the operation and behavior of the systems and/or methods are described herein without reference to specific software code—it being understood that software and hardware can be designed to implement the systems and/or methods based on the description herein. 
     Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of various implementations includes each dependent claim in combination with every other claim in the claim set. 
     No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Further, as used herein, the article “the” is intended to include one or more items referenced in connection with the article “the” and may be used interchangeably with “the one or more.” Furthermore, as used herein, the term “set” is intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, etc.), and may be used interchangeably with “one or more.” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Also, as used herein, the term “or” is intended to be inclusive when used in a series and may be used interchangeably with “and/or,” unless explicitly stated otherwise (e.g., if used in combination with “either” or “only one of”). Further, spatially relative terms, such as “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the apparatus, device, and/or element in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated  90  degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.