INTEGRATED INDUCTOR

BACKGROUND

[0001] Inductors are used in a wide variety of integrated circuit applications including voltage regulators such as switching power converters. An inductor is a conductor that is shaped in a manner to store energy in a magnetic field adjacent to the conductor. An inductor typically has one or more "turns" that concentrate the magnetic field flux induced by current flowing through each turn of the conductor in an "inductive" area defined within the inductor turns. In some cases the aspect ratio of the turn can be large so that the turn forms an ellipse or a rectangle. The aspect ratio may be so large that the inductor turn with its return path forms a transmission line. [0002] Inductors have been implemented in integrated circuit dies and circuit packages but they may have several drawbacks. They have typically been made by forming helical or spiral traces in conductive layers (such as in conductive semiconductor or package or printed circuit board substrate layers) to form inductor turns. In some cases, these traces may be coupled to traces in adjacent layers in order to achieve higher inductance and/or current capability. Unfortunately, they can consume excessive trace layer resources and may not provide sufficient current capacity or high enough quality factor without unreasonable scaling. In addition, because their inductive areas are substantially parallel with respect to other trace layers in the package substrate and circuit die, they can have unfavorable electromagnetic interference (EMI) effects on other components within the integrated circuit and/or their inductor characteristics can be adversely affected by adjacent conductors within the substrate or circuit die. Accordingly, a new inductor solution is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements.

[0004] Figure IA is a diagram of a conventional integrated circuit.

[0005] Figure IB is a sectional view of a portion of a substrate from the integrated circuit of Figure IA.

[0006] Figure 2 is a diagram of an integrated circuit with embedded substrate inductors in accordance with some embodiments.

[0007] Figure 3 is a schematic diagram of a power converter with inductors in accordance with some embodiments.

[0008] Figure 4A is a perspective view of an inductor in accordance with some embodiments.

[0009] Figure 4B is a perspective view of an inductor with a wider inductive loop area in accordance with some embodiments.

[0010] Figure 5 is a perspective view of an inductor with multiple coupling conductive layers in accordance with some embodiments.

[0011] Figure 6 is a perspective view of multiple inductors arranged in adjacent rows in accordance with some embodiments.

[0012] Figure 7 is a perspective view of the multiple inductors of Figure 6 with a terminal from each inductor coupled to a conductive layer portion to form a common terminal in accordance with some embodiments.

[0013] Figure 8 is a perspective view of multiple inductors arranged in a single row in accordance with some embodiments.

[0014] Figure 9 is a perspective view of the multiple inductors of Figure 8 with a terminal from each inductor coupled to a conductive layer portion to form a common terminal in accordance with some embodiments.

[0015] Figure 10 is a perspective view of multiple inductors arranged in a single row with staggered terminals in accordance with some embodiments.

[0016] Figure 11 is a perspective view of the multiple inductors of Figure 10 with a terminal from each inductor coupled to a conductive layer portion to form a common terminal in accordance with some embodiments.

[0017] Figure 12 is a block diagram of a computer system having a power converter with inductors in accordance with some embodiments.

DETAILED DESCRIPTION

[0018] Figure IA shows a conventional integrated circuit (IC) 100 generally comprising at least one semiconductor die 102 electrically coupled (e.g., through solder bumps) to a package substrate 104. The die 102 may be electrically coupled to the substrate throughout the majority of its undersurface (as is the case, for example, with a flip-chip type package) which allows for increased external connections with greater current capacity. Within the scope of this patent application, the term "substrate" refers to any substrate that die 102 is mounted on including a dedicated or shared package substrate, interposer substrate or printed circuit board. That is, in some embodiments, die 102 could be mounted on a printed circuit board or on an interposer substrate. [0019] Figure 1 B is a cross-sectional view of the substrate 104 from an IC of Figure IA. The substrate 104 comprises an insulative core (e.g., made from organic resin material, plastic, ceramic, or some other suitable material) 113 sandwiched

between conductive core layers 111, insulative (e.g., core) layers 109, and conductive build-up layers 107. The die 102 is typically electrically coupled through its contacts on a build-up layer 107 (e.g., "upper" layer) using solder bumps or some other suitable contacts. From there, vias (micro vias 115 and plated through holes 117) electrically couple the die contacts to desired portions (e.g., traces) of the different conductive layers 111, 107 to couple them, for example, to a socket or circuit board housing the substrate.

[0020] A plated through hole (PTH) is a type of via. As used herein, the term "via" refers to a conductive member in a substrate that can be used to electrically couple two or more spaced apart conductive layers in a substrate. Plated through holes are normally used to couple traces separated by farther distances, while micro vias 115 are typically used to couple extreme outer (upper and lower) trace layers to adjacent layers. Typically, vias are formed from a hole lined and/or filled with a conducting material (e.g., copper), they are usually disposed perpendicularly to the plane of the substrate but can be angled, so long as they have a perpendicular component thereby allowing them to span two or more layers. Depending on the size of the substrate and number of needed electrical connections, a substrate may have hundreds or thousands of vias and in many cases, have capacity for even more, which is exploited by some embodiments disclosed herein.

[0021] Figure 2 shows an IC 200 in accordance with some embodiments of the invention. It generally comprises at least one IC die 102 electrically coupled to a substrate 204 having a region 206 with one or more embedded inductors in accordance with embodiments disclosed herein. While IC 200 shows only a single die 202, it could comprise a number of additional dies and may perform a variety of functions. For

example, in some embodiments, it comprises one or more power converter circuits, such as the circuit described below, using one or more inductors from the embedded inductor region 206.

[0022] Figure 3 shows a multi-phase "buck" type switching power converter with novel inductors 304, configured in accordance with some embodiments. The depicted converter generally comprises a controller (also sometimes referred to as a pulse width modulator) 302 coupled to driver switches (or switches) Si to S _N , which in turn are coupled to inductors, Li to L _N , and capacitor C to generate a regulated DC output voltage V ₀ Ut. Typically, the depicted converter is used to "step down" a DC voltage, V _1n , supplied to switches Si to SN, to a smaller, regulated DC voltage V _ou t- [0023] Controller 302 generates trigger signals applied to the switches. Each switch produces a pulse train voltage signal ranging between the applied input value (V _1n ) and the low- side reference (Vss)- The pulse train signal produced from each switch is applied to an input of an associated inductor. The duty cycle of an applied pulse train signal generally determines the magnitude of the voltage generated at the output of the inductor (V _out ).

[0024] The converter could operate as a single phase converter with a single driven inductor or as a multi-phase converter with multiple inductors. With a multi-phase converter, the trigger signals for the switches (Si to S _N ) are skewed in time (phase shifted) so that switching noise from each inductor is distributed in time. This multiphase approach serves to reduce the voltage ripple at the output. The capacitor C filters ripple, along with AC noise, from the output DC voltage (V _out ). [0025] Ripple is one characteristic for qualifying a power converter (or converter).

The smaller the ripple the better. In general, to achieve a given ripple constraint,

smaller inductors can be used in a multi-phase design than could otherwise be used in an analogous single phase implementation because the interleaved phase portions serve to "smooth" the output signal. Another factor is transient response. Transient response time is essentially the time required for the output voltage V _ou t to respond to a change from the controller or to a change in the load current. In sizing the inductors, a tradeoff typically exists between ripple and transient response. With larger inductors, ripple reduction improves but transient response time increases. Another factor is converter efficiency, which is the percentage of total power consumed by the converter that goes to the output load (not shown). With the quality (Q) factor defined as the ratio of an inductor's imaginary (inductive) impedance to its real (resistive) impedance, efficiency increases with a higher inductor Q factor. With all of this in mind, the inductor structures disclosed herein and described in the following sections provide a flexible solution for implementing single and multiple inductors with desired inductor characteristics.

[0026] Figures 4 A and 4B show inductors in accordance with some embodiments. They comprise spaced apart vias 404 coupled together at common ends with a portion 406 of a conductive layer. At their other ends, they are coupled to conductive layer portions 402, which serve as first and second inductor terminals. [0027] The spaced apart vias 404 and coupling conductive layer portion 406 make up a single inductor "turn" (notwithstanding the fact that the turn is left open between the terminals, although this is not required). Together, the vias and coupling layer portion define a rectangular shaped cross-sectional core area (or inductor area). It is worth pointing out that with the depicted configuration, the inductor areas (loop cross- sections) are substantially perpendicular to the conductor layers within the substrate,

which reduces the adverse effect they may have on inductor performance, as well as the negative impact the inductor may have on signals within conductor layer traces. [0028] With its wider coupling portion 406, the inductor of Figure 4B has a larger inductor loop area than that of the inductor of Figure 4 A and thus, with everything else substantially being the same, has a larger associated inductance. However, depending upon the amount to which its resistance is also larger, its quality factor may or may not be higher.

[0029] Figure 5 shows another embodiment of an inductor. As with the inductors of Figures 4A and 4B, it has spaced apart vias 504, but instead of a single conductive layer coupling them together, it uses multiple, conductive layer portions 506 to couple the vias together at a common end of the vias. It also uses multiple, conductive layer portions 502 coupled at the other ends for its first and second inductor terminals. Multiple conductive layer portions will typically provide for less inductor resistance, resulting in a higher quality factor and greater current capacity. This can be valuable for power converter applications to achieve increased efficiency and to be able to service larger load demands.

[0030] Figure 6 shows multiple inductors arranged in two adjacent rows, each having four inductors. Each inductor may be configured as an inductor from Figures 4A, 4B, or 5, although in the depicted embodiment, the terminal portions and layer portions coupling the vias together are made from a single layer. [0031] Figure 7 shows the inductors of Figure 6 but with a terminal from each inductor coupled together by a conductive layer portion 702 to form a common terminal. Such a configuration could be used, for example, to implement inductors in a voltage regulator such as the power converter of Figure 3.

[0032] Figure 8 shows another embodiment of multiple inductors (eight in the depicted embodiment) arranged in a single row. Not only may this allow for larger inductor areas for each inductor, but also, it may provide easier routing access to all of the terminals.

[0033] Figure 9 shows the multiple inductors of Figure 8 with a terminal from each inductor coupled to a conductive layer portion 902. This set of commonly connected terminals could provide a common output, e.g., for a multi-phase power converter. [0034] Figure 10 shows multiple inductors configured in accordance with other embodiments. It comprises interleavably staggered (or skewed) inductors. As depicted, this allows them to be placed closer to one another with their terminal layer portions for adjacent inductors not being disposed along a common line. Figure 11 shows the inductors with a terminal from each inductor coupled to a common layer portion 1102 to provide a common terminal for all of the inductors. [0035] It should be appreciated that other embodiments not specifically presented are within the scope of the invention. For example, while the disclosed inductors have inductor areas that are substantially vertical relative to a substrate, it is contemplated that they could also have a horizontal component (i.e., be angled), depending upon design concerns and/or manufacturing preferences. In addition, while the depicted inductors are implemented with plated through hole vias, any other type of via could also be used, depending upon available materials and/or manufacturing processes. They could be formed from layered, deposited, and/or filled holes (e.g., formed from mechanical and laser drilling, milling, sacrificial formations), or they could be made from some other process. Moreover, while the use of magnetic materials is not specifically disclosed, they are not discounted from the scope of the invention and may

be used in some embodiments. For example, a magnetic material layer could be disposed "beneath" the inductors to enhance their inductances. However, the use of such a material may not be desired due to process limitations or other detriments. It is anticipated that the inductors disclosed herein may be used in high frequency (e.g., in excess of 10 MHz.) switching applications, which may make it unfeasible to use a magnetic material.

[0036] With reference to Figure 12, one example of a computer system is shown. The depicted system generally comprises a processor 1202 that is coupled to a power converter 1204, a wireless interface 1206, and memory 1208. It is coupled to the converter 1204 to receive from it power when in operation. The wireless interface 1206 is coupled to an antenna 1210 to communicatively link the processor through the wireless interface chip 1206 to a wireless network (not shown). The power converter 1204 comprises a substrate 1205 that includes inductors in accordance with some embodiments disclosed herein.

[0037] It should be noted that the depicted system could be implemented in different forms. That is, it could be implemented in a single chip module, a circuit board, or a chassis having multiple circuit boards. Similarly, it could constitute one or more complete computers or alternatively, it could constitute a component useful within a computing system.

[0038] The invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. For example, it should be appreciated that the present invention is applicable for use with all types of semiconductor integrated circuit ("IC") chips. Examples of these IC chips include but are not limited to processors, controllers, chipset

components, programmable logic arrays (PLA), memory chips, network chips, and the like.

[0039] Moreover, it should be appreciated that example sizes/models/values/ranges may have been given, although the present invention is not limited to the same. As manufacturing techniques (e.g., photolithography) mature over time, it is expected that devices of smaller size could be manufactured. In addition, well known power/ground connections to IC chips and other components may or may not be shown within the FIGS, for simplicity of illustration and discussion, and so as not to obscure the invention. Further, arrangements may be shown in block diagram form in order to avoid obscuring the invention, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements are highly dependent upon the platform within which the present invention is to be implemented, i.e., such specifics should be well within purview of one skilled in the art. Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the invention, it should be apparent to one skilled in the art that the invention can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting.