Silicon Integrated Inductor With Ferromagnetic Core for Higher Inductance
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Solution Overview
Problem
Conventional substrate- or silicon-based air core inductor designs and ferromagnetic-based thin film inductor solutions face limitations in inductance values and material constraints, hindering the development of high-performance switched-inductor integrated voltage regulators (IVRs).
Innovation Solution
The fabrication of ferromagnetic core inductors in silicon substrates involves depositing ferromagnetic material into bulk silicon at early stages of IC manufacturing, using interposer processing to create inductor structures with through-silicon vias and metal pads, allowing for larger coil diameters and fine-tuning of inductor properties, while maintaining compatibility with conventional silicon interposer processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional substrate- or silicon-based air core inductor designs are used, then manufacturing simplicity is maintained, but inductance values are limited
Solution Approach 1:
The patent combines ferromagnetic material with silicon substrate to create a composite core structure. The ferromagnetic material is deposited into cavities formed in the silicon substrate, creating a hybrid inductor that achieves high inductance values while maintaining compatibility with standard silicon manufacturing processes. This composite approach resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The invention introduces ferromagnetic material only in specific localized regions (cavities) within the silicon substrate rather than throughout the entire structure. This localized application of ferromagnetic material concentrates the magnetic flux where needed, achieving high inductance values in a targeted area while maintaining the overall simplicity of silicon-based manufacturing.
2Quantity of substance
If ferromagnetic-based thin film inductor solutions are integrated in active silicon backend layers, then inductance values are improved, but material and process constraints are introduced
Solution Approach 1:
The patent performs ferromagnetic material deposition at early stages of IC manufacturing, before the silicon substrate is thinned and before backend processing begins. This preliminary action allows the use of bulk silicon and enables a wider range of ferromagnetic materials and deposition methods that would be incompatible with backend integration, thereby resolving the material and process flexibility constraints.
Solution Approach 2:
Instead of integrating ferromagnetic material in the planar backend layers, the invention moves the ferromagnetic core to the bulk silicon dimension, utilizing the vertical depth of the substrate. This dimensional shift allows for larger coil diameters and more flexible inductor geometries, expanding material and process options while achieving high inductance values.
3Use of energy by moving object
If inductors are integrated on-die with power-consuming devices, then current reduction is achieved, but inductance density must be maximized
Solution Approach 1:
The patent embeds ferromagnetic material within cavities formed in the silicon substrate, creating a nested structure where the ferromagnetic core is contained within the silicon matrix. This nesting allows for compact inductor designs with high inductance density, enabling on-die integration without excessive area occupation while maintaining the current reduction benefits of switched-inductor IVRs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the creation of integrated inductors with substantial inductance values within a small area, enhancing the performance of IVRs by expanding the range of ferromagnetic materials and deposition methods, and improving dynamic voltage and frequency scaling capabilities.
Implementation Method 1
Ferromagnetic material is deposited into a bulk silicon substrate
Implementation Method 2
Ferromagnetic material is deposited into a bulk silicon substrate... creating inductor structures with through-silicon vias and metal pads, allowing for larger coil diameters and fine-tuning of inductor properties
Data Source
AI summary
A process for manufacturing inductors for use in integrated circuits includes embedding ferromagnetic material in a bulk silicon substrate, forming a plurality of vias in the bulk silicon substrate such that the vias bracket a volume of the bulk silicon substrate that includes the ferromagnetic material, slicing the bulk silicon substrate to form a silicon wafer, and configuring traces between top metal pads of the vias and between bottom metal pads of the vias to form a continuous path for current to flow circumferentially from a first end of the volume to a second end of the volume.