The present disclosure relates to inductors, and more specifically, to inductors with fill elements.
Inductors are devices that sometimes have a two-terminal conductor (within an insulator) that is shaped in windings or coils (that are sometimes referred to as loops or turns). The conductor is shaped to increase the magnetic flux of the inductor, and the number of windings of the conductor increases the number of times the magnetic flux lines link, increasing the field and thus the inductance.
In multi-layer integrated circuits, the inductor can be a conductor within a portion of one of the layers and can be bordered by other insulator layers. Additionally, fill elements can be positioned in one or more surrounding layers. Such fill elements add structural stability to the integrated circuit and are usually formed of materials that have structural strength, such as metals, etc. However, such fill elements can influence the magnetic fields around the inductor, decreasing performance of the inductor.
According to one embodiment herein, a structure includes (among other components) a first layer having inductor windings. An inner area of the first layer is at least partially enclosed by the inductor windings and an outer area of the first layer is separated from the inner area by at least one winding. This structure further includes a second layer having structural fill elements. The first layer and the second layer are parallel, and the second layer is relatively below the first layer in a direction perpendicular to the first layer. The density of the structural fill elements aligned below the inner area is less than the density of the structural fill elements aligned below the outer area.
In another structure herein, a first layer has inductor windings. An inner area of the first layer is at least partially enclosed by the inductor windings and an outer area of the first layer is separated from the inner area by at least one winding. This structure further includes a second layer having groups of structural fill elements. The first layer and the second layer are parallel, and the second layer is relatively below the first layer in a direction perpendicular to the first layer. The number of structural fill elements in the groups of structural fill elements increases as distances increase from the location in the second layer that is aligned below the center of the inner area.
An additional structure herein includes a first layer having inductor windings. An inner area of the first layer is at least partially enclosed by the inductor windings and an outer area of the first layer is separated from the inner area by at least one winding. This structure also includes a second layer having structural fill elements. The first layer and the second layer are parallel, and the second layer is relatively below the first layer in a direction perpendicular to the first layer. The number of structural fill elements in the structural fill elements increases as distances increase from the location in the second layer that is aligned below the center of the inner area. Additionally, the distance between the first layer and the structural fill elements decreases as distances increase from the location in the second layer that is aligned below the center of the inner area.
The embodiments herein will be better understood from the following detailed description with reference to the drawings, which are not necessarily drawn to scale and in which:
As mentioned above, metallic fill elements in a layer that is adjacent to and insulated from an inductor’s coil can add structural stability. However, the presence of such fill elements can influence the magnetic fields around the inductor, which increases parasitic capacitance and decreases performance of the inductor. It is especially challenging to get higher Q (quality factor) with low resistivity substrate technologies and such fill elements underneath the inductor further degrades the quality factor.
In view of such issues, with the structures disclosed below the density of the adjacent fill elements increases in locations moving radially outwards from the inner region of the coil to the outer region. In some structures the increasing density of the fill elements can be based on a voltage profile within the spiral of the coil, such as where the fill elements are only located underneath the spaces between the spiral metal strips. Additionally, the increasing density not only occurs parallel to the integrated structure’s layers (e.g., not just parallel to the X-Y direction of the inductor fill material layers) but also perpendicular thereto (e.g., in the Z direction also).
Thus, with structures herein relatively more of the fill elements are positioned adjacent the outer region of the coil and the number of such structures per unit area tapers as locations move closer to the center of the coil, which reduces parasitic capacitance and improves the quality factor.
As shown in
As can be seen most clearly in the view in
As shown in
As can be seen most clearly in
Therefore, the inner area 132 of the first layer 148 is at least partially enclosed by the inductor windings 110 and the outer area 136 of the first layer 148 is separated from the inner area 132 by at least one middle winding 117 of the inductor windings 110. As used herein the “inner” and “outer” terms simply refer to relative positions. Therefore, many windings of the inductor windings 110 are considered inner or outer windings relative to other windings (except the most inner winding 116 and the most outer winding 118 which are the extreme position windings).
The structural fill elements 120 in the second layer 144 can be any material that adds rigidity/stiffness to the insulator material that makes up the remainder insulator material in the second layer 144. Thus, the structural fill elements 120 can be metal, silicon, polymer, ceramic, etc., or any other convenient material that has a lower flexibility (greater stiffness) than the remaining insulator material of the second layer 144. In some embodiments, the structural fill elements 120 are generally all formed of the same material in any given structure to provide manufacturing convenience.
Further, the structural fill elements 120 can be any convenient shape (including, rectangular blocks, cylinders, spheres, cones, etc.) and are electrically insulated from each other and all other structures by the remaining insulator material of the second layer 144. The additional rigidity provided by the structural fill elements 120 adds structural support to the entire laminated, multi-layer inductor integrated structure 100; however, as noted above, the presence of such fill elements can influence the magnetic fields around the inductor, which can increase parasitic capacitance and decrease performance of the inductor.
In order to avoid performance consequences of using the structural fill elements 120, in structures herein the density (meaning the number of elements per unit area) of the structural fill elements 120 decreases as distances from the inner area 132 increase. In some embodiments, the structural fill elements 120 are generally all formed to have the same size and shape in any given structure to provide manufacturing convenience.
Therefore, the density of the structural fill elements 120 that are aligned below the inner area 132 of the first layer 148 is less than the density of the structural fill elements 120 in the second layer 144 that are aligned below the outer area 136. Stated differently, the density of the structural fill elements 120 increases as distances increase from the center location in the second layer 144 (that is aligned below the center of the inner area 132).
Further, in the inductor structure 100 shown in
A layout view of the inductor structure 102 shown in
While the inductor structures 100, 102 shown in
Thus, in the inductor structure 104 in
Grouping the structural fill elements allows the groups of structural fill elements 162, 164, 166 to be located in areas of the second layer 144 that are not aligned below (in the first direction) the inductor windings 110. Instead, as shown in
As with the inductor structure 104 shown in
As mentioned above, the second layer 144 can actually be a multi-layer structure and the same is shown in
As can be seen in
As noted above, the structural fill elements 120 are sometimes formed from conductive materials (e.g., metals, etc.) because such materials are used in existing processing steps, and because they provide good structural rigidity. However, such conductors in combination with the surrounding insulator layers can act as capacitors, which increases parasitic capacitance and reduces the output of the inductor structure. This decreases the effectiveness of the inductor structure and lowers its quality factor (Q).
Working to reduce such unwanted parasitic capacitance while still promoting structural rigidity, it was found that the voltage is highest at the center of the inductor and that voltage decreases in the outer areas of the inductor. This information was used to modify traditional structures to move conductive elements away from the center to the outer regions of the structure (in both horizontal and vertical directions). Doing so dramatically reduces or eliminates parasitic capacitance where voltage is highest (at the inductor center), gaining the most in performance. The higher density of the structural fill elements in the outer areas of the inductor structure has minimal effect on device performance because those outer regions output lower energies. This effect can be seen in
More specifically,
In reverse excitation of the structure shown in
For purposes herein, an “insulator” is a relative term that means a material or structure that allows substantially less (<95%) electrical current to flow than does a “conductor.” The dielectrics (insulators) mentioned herein can, for example, be grown from either a dry oxygen ambient or steam and then patterned. Alternatively, the dielectrics herein may be formed (grown or deposited) from any of the many candidate low dielectric constant materials (low-K (where K corresponds to the dielectric constant of silicon dioxide) materials such as fluorine or carbon-doped silicon dioxide, porous silicon dioxide, porous carbon-doped silicon dioxide, spin-on silicon or organic polymeric dielectrics, etc.) or high dielectric constant (high-K) materials, including but not limited to silicon nitride, silicon oxynitride, a gate dielectric stack of SiO2 and Si3N4, hafnium oxide (HfO2), hafnium zirconium oxide (HfZrO2), zirconium dioxide (ZrO2), hafnium silicon oxynitride (HfSiON), hafnium aluminum oxide compounds (HfAlOx), other metal oxides like tantalum oxide, etc. The thickness of dielectrics herein may vary contingent upon the required device performance.
The conductors mentioned herein can be formed of any conductive material, such as polycrystalline silicon (polysilicon), amorphous silicon, a combination of amorphous silicon and polysilicon, and polysilicon-germanium, rendered conductive by the presence of a suitable dopant. Alternatively, the conductors herein may be one or more metals, such as tungsten, hafnium, tantalum, molybdenum, titanium, or nickel, or a metal silicide, any alloys of such metals, and may be deposited using physical vapor deposition, chemical vapor deposition, or any other technique known in the art.
While only one or a limited number of inductors are illustrated in the drawings, those ordinarily skilled in the art would understand that many different types inductors could be simultaneously formed with the embodiment herein and the drawings are intended to show simultaneous formation of multiple different types of transistors; however, the drawings have been simplified to only show a limited number of inductors for clarity and to allow the reader to more easily recognize the different features illustrated. This is not intended to limit this disclosure because, as would be understood by those ordinarily skilled in the art, this disclosure is applicable to structures that include many of each type of inductor shown in the drawings.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the foregoing. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, as used herein, terms such as “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “upper”, “lower”, “under”, “below”, “underlying”, “over”, “overlying”, “parallel”, “perpendicular”, etc., are intended to describe relative locations as they are oriented and illustrated in the drawings (unless otherwise indicated) and terms such as “touching”, “in direct contact”, “abutting”, “directly adjacent to”, “immediately adjacent to”, etc., are intended to indicate that at least one element physically contacts another element (without other elements separating the described elements).
Embodiments herein may be used in a variety of electronic applications, including but not limited to advanced sensors, memory/data storage, semiconductors, microprocessors and other applications. A resulting device and structure, such as an integrated circuit (IC) chip can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product that includes integrated circuit chips, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard or other input device, and a central processor.
While the foregoing has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the embodiments herein are not limited to such disclosure. Rather, the elements herein can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope herein. Additionally, while various embodiments have been described, it is to be understood that aspects herein may be included by only some of the described embodiments. Accordingly, the claims below are not to be seen as limited by the foregoing description. A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” All structural and functional equivalents to the elements of the various embodiments described throughout this disclosure that are known or later, come to be known, to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by this disclosure. It is therefore to be understood that changes may be made in the particular embodiments disclosed which are within the scope of the foregoing as outlined by the appended claims.