Magnetic Core TSV-Inductor Design and Optimization for On-chip DC-DC Converter

Abstract

The conventional on-chip spiral inductor consumes a significant top-metal routing area, thereby preventing its popularity in many on-chip applications. Recently through-silicon-via (TSV) based inductor (also known as TSV-inductor) with a magnetic core has been proved to be a viable option for the on-chip DC-DC converter. The operating conditions of these inductors play a major role in maximizing the performance and efficiency of the DC-DC converter. However, there is a critical need to study the design and optimization details of magnetic core TSV-inductors with the unique 3D structure embedding magnetic core. This paper aims to provide a clear understanding of the modeling details of a magnetic core TSV-inductor and a design and optimization methodology to assist efficient inductor design. Moreover, a machine learning assisted model combining physical details and artificial neural network (ANN) is also proposed to extract the equivalent circuit to further facilitate DC-DC converter design. Experimental results show that the optimized TSV-inductor with the magnetic core and air-gap can achieve inductance density improvement of up to 7.7 × and quality factor improvements of up to 1.6 × for the same footprint compared with the TSV-inductor without a magnetic core. For on-chip DC-DC converter applications, the converter efficiency can be improved by up to 15.9% and 6.8% compared with the conventional spiral and TSV-inductor without magnetic core, respectively.

Modeling and Thermal Stress Coupling Optimization Design of TSV Inductors in On-Chip DC/DC Converters

“…Additionally, mutual inductance exists among the coils in the TSV array. Therefore, the approximate formula for calculating the inductance with the magnetic core can be written as equation (10).…”

“…Krishnamurthy from Intel Corporation reported the feasibility of TSV inductance and on-chip DC/DC converters, constructed under 14nm CMOS technology [9]. Chen and colleagues utilized machine learning methods to extract the circuit equivalent model of TSV inductance and developed an optimization algorithm for TSV inductors based on this [10].…”

Design, Analysis and Optimization of Magnetic-Core Solenoid Inductor for On-Chip Multi-Phase Buck Converter

“…This inductor occupies 19.2mm 2 area, which is almost the same size as the die. With technology shrinking, there will be a mismatch between the packaged inductor area with the die size [14,17]. Thus, on-chip inductors need to be investigated for implementing voltage regulators to address the scalability issue.…”

“…Recent works on on-chip magnetic inductors suggest that the inductance density can be increased significantly by using magnetic-core material, specifically CoZrTa material, which has a relative permeability of up to 700 [3,14,17,[25][26][27][28]. [25] studied the spiral magnetic inductor, where the magnetic-core is present around the interconnect, and the experimental results show that the inductance density is increased by up to 19× compared to the conventional planar inductor.…”

“…[25] studied the spiral magnetic inductor, where the magnetic-core is present around the interconnect, and the experimental results show that the inductance density is increased by up to 19× compared to the conventional planar inductor. [14,17] used a layered magnetic-core in a TSV inductor and has achieved a 7.7× improvement in inductance density compared with the TSV inductor without magnetic-core for DC-DC converter application. [26] has designed a 3D TSV on-die inductor with a backside planar magnetic core in 14nm tri-gate test chip and achieved an inductance density of 111nH/mm 2 .…”