BACKGROUND

Field

Embodiments described herein relate to semiconductor packages. More specifically, the described embodiments are directed to inductors for semiconductor packages.

Background Information

An inductor is a passive electronic component that is typically included in a semiconductor package comprising a package substrate and one or more semiconductor dies on the package substrate. One or more inductors can be used to form a functional or fully integrated voltage regulator (IVR). The IVR can provide one or more voltage regulators for semiconductor die(s) within a semiconductor package.

Inductors used in semiconductor packages can take multiple forms. Examples include, but are not be limited to, discrete inductors and air core inductors (ACIs).

Discrete inductors are generally prepackaged inductor devices (e.g., off-chip, off-package devices comprising one or more inductors, etc.). Discrete inductors typically include at least one magnetic core inductor (MCI). An MCI is an inductor comprising an insulated wire wound into a coil around a magnetic core made of a ferromagnetic or ferrimagnetic material (e.g., iron, ferrite, etc.). A magnetic core can increase the inductance of a coil by increasing the magnetic field. This increase is due to the magnetic core's higher magnetic permeability (as opposed to the relatively lower magnetic permeability of the coil itself or of a non-magnetic core such as air, glass, mica, plastic, ceramic, or any other dielectric material). Most discrete inductors are proprietary to and outsourced from third party vendors. These inductors are embedded in or surface mounted on a package substrate during semiconductor package fabrication. As used herein, a “package substrate” includes one or more of: (i) a package substrate core formed from any suitable material; and (ii) one or more layers (e.g., a metal layer, a interlayer dielectric layer, a build-up layer, a seed layer, any other layer known in the art of semiconductor manufacturing and/or packaging, etc.).

There are some drawbacks associated with discrete inductors. Discrete inductors can be costly (when compared to ACIs). Also, the embedding processes used to incorporate discrete packages into semiconductor packages can be complicated. Additionally, the surface mounting processes used to incorporate discrete packages into semiconductor packages can add an undesired thickness (e.g., z-height, etc.) to the overall thickness of the resulting semiconductor package. Discrete inductors might also require extra space outside a semiconductor package, which can be difficult to achieve in high-density microelectronic devices. Additionally, because discrete inductors are usually prepackaged devices that are proprietary to third party vendors, package design may be limited.

ACIs are typically embedded in semiconductor packages. Conventional ACI formation involves forming one or more features, portions, or constituent parts of an inductor (“inductor features”) on or in one or more layers of a package substrate. For example, conductive lines may be patterned on a layer to form one or more inductor features. Examples of inductor features include, but are not limited to, a coil having any shape (e.g., a loop, a square, a circle, a spiral, etc.) formed from conductive lines and one or more pads. Generally, an ACI formed in a semiconductor package does not include a magnetic core. As a result, an ACI's magnetic permeability can be lower than an MCI's magnetic permeability. For example, the magnetic permeability of an ACI may be approximately equal or equal to the magnetic permeability of air. Examples of conductive lines are copper lines, aluminum lines, lines formed from any other metal or metal alloy as is known in the art of semiconductor packaging and/or manufacturing, etc.

ACIs have some drawbacks even though they can be less expensive than discrete inductors. One drawback is that ACIs may not generate inductance as effectively or as efficiently as discrete inductors. Another drawback is that ACIs can take up valuable real estate in a package substrate in order to generate a target inductance, which can in turn reduce the achievable input/output (I/O) density per mm per layer (IO/mm/layer) in a semiconductor package.

Several proposals for inductors that lack the drawbacks described above are in existence. One proposal is to fabricate an ACI comprising a magnetic film (e.g., a film having one or more magnetic fillers embedded therein, etc.). The magnetic film can increase the ACI's magnetic permeability, which can in turn enhance the ACI's performance. The magnetic film, however, is not easily integrated into current semiconductor fabrication processes that comply with current industry standards. One drawback associated with the magnetic film is that laser drilling of vias through the magnetic film may be difficult, costly, or complicated. For a first example, after laser drilling of a magnetic film to form vias is performed, some of the film's magnetic fillers are not ablated away, which in turn leaves residue in the resulting vias creating unwanted “dirty vias.” Another drawback associated with the magnetic film is that there is a risk of contamination of bath chemistries associated with wet plating processes and/or a risk of contamination of etch tools. For one example, magnetic fillers in the magnetic film may have negative, undesirable, or unexpected interactions with bath chemistries, materials, and/or tools used in, for example, desmearing processes, electroless plating processes, flash etching processes, soft etching processes, seed etching processes, and processes involving roughening baths. For another example, introduction of the magnetic film to certain bath chemistries may result in corrosion, destruction, dissolution, or degradation of the magnetic fillers in the magnetic film. For this example, corrosion of the magnetic fillers may cause the magnetic fillers to leach into bath chemistries, which can in turn contaminate the baths and reduce the life cycle of the baths. Consequently, and for this example, a semiconductor package formed using the contaminated baths and the magnetic film may exhibit suboptimal properties (e.g., suboptimal electrical performance, etc.)

One proposal to minimize or eliminate the drawbacks described above is to tailor the magnetic film described above to current semiconductor fabrication processes that comply with current industry standards. Another proposal to minimize or eliminate the drawbacks described above is to tailor bath chemistries associated with wet processes and/or tools or materials used in etching techniques to work with the magnetic film described above. These tailoring process can be a time-consuming and expensive endeavor, which can in turn increase costs associated with semiconductor manufacturing and/or packaging. Furthermore, these tailoring processes may run a risk of over-engineering—that is, the magnetic film, the bath chemistries associated with wet processes, and/or the tools or materials used in etching techniques may be suboptimally designed due to restrictions placed on the types or amount of magnetic fillers that can be used to form the magnetic film. For example, a specific type of magnetic filler with suboptimal magnetic permeability properties (when compared to other types of magnetic fillers) may be used to form the magnetic film. For this example, the chosen magnetic filler is used despite the existence of other magnetic fillers with more optimal magnetic permeability properties in order to minimize or eliminate one or more of the drawbacks described above in connection with magnetic material(s).

