Yongki Min

High-frequency responses of granular CoFeHfO and amorphous CoZrTa magnetic materials

High-resistivity soft magnetic materials are receiving much attention as they have relatively low core loss at high frequencies. We developed magnetically soft granular CoFeHfO material by pulsed-dc reactive magnetron sputtering and compared its electrical and magnetic properties, especially permeability spectra, with those of amorphous CoZrTa material. We also investigated the permeability spectra of patterned CoFeHfO films with different thicknesses and observed their magnetic domain structures by Kerr imaging microscopy. The granular CoFeHfO material has a better high-frequency response than the amorphous CoZrTa at thicknesses beyond ∼0.5μm, if the ratio of the real/imaginary parts of the permeability is the principal figure of merit, and is an excellent candidate for high-frequency applications such as integrated magnetic inductors.

Small-Resistance and High-Quality-Factor Magnetic Integrated Inductors on PCB

We have designed and fabricated both single-coil and parallel-coil magnetic integrated inductors with extremely small resistances and high quality factors on an 8-in-round printed circuit board (PCB) substrate for microprocessor power delivery applications. The dc resistances of these inductors are less than 12 mOmega. Soft magnetic material CoFeHfO was successfully integrated into the inductor fabrication to increase the inductance. The quality factors are more than 80 in a frequency range of 1.5-2 GHz for air-core inductors and more than 23 in a range of 200-300 MHz for magnetic inductors. The net inductance improvement of the magnetic inductor over air-core inductor is about 12%, which could be further enhanced with a thicker magnetic core, according to our theoretic calculation and HFSS simulation. We also characterized the permeability spectra of CoFeHfO material on the PCB substrate, simulated the high-frequency performance of the magnetic integrated inductor by HFSS, and, for the first time, reached a good agreement with the experimental data. The experimental and simulation results of the magnetic inductors as compared to those of the air-core inductors point out the future direction to further optimize magnetic integrated inductors.

Tensor Nature of Permeability and Its Effects in Inductive Magnetic Devices

The tensor nature of the permeability of soft magnetic materials with an in-plane anisotropy was investigated. Using tensor transformation, the measured permeability was proportional to cos2 alpha, where alpha is the angle between the external exciting magnetic field and hard axis of magnetic material, which was proven by experimental data for thin-film materials CoFeHfO and CoTaZrTb. A new type of inductor was designed and simulated by Ansoft Maxwell 3-D to study the effects of the tensor nature of the permeability in the simulation of inductors. It is important to appropriately account for the tensor nature of the permeability of soft magnetic materials in inductive device simulation to establish realistic device models. A magnetic integrated inductor with extremely low DC resistance (<9mOmega) was fabricated. Its high-frequency performance was measured and compared to HFSS simulation using appropriate tensor permeability

Embedded capacitors in the next generation processor

Embedded passives technology has been of interest to electronic package designers for performance improvement and package size reduction. With the explosion of mobile phones, tablets and other hand held devices, the need for smaller form factor products with equivalent or better electrical performance makes a very compelling case for embedding passives. The benefits of embedded passives are not limited to small form factor devices. Larger die and server products requiring high performance power delivery solutions can also benefit substantially from embedded capacitors. Intel in collaboration with its suppliers has developed and commercialized a disruptive embedded capacitor technology that provides significant power delivery benefits for high performance computer applications. This is the first commercialized embedded capacitor technology used by Intel.

Package compatibility and substrate dependence of granular soft magnetic material CoFeHfO developed by reactive sputtering

Integration of magnetic passive components into package has been attracting more interests recently, but efficient package-compatible magnetic materials are needed. We have developed a package-compatible granular material, CoFeHfO, on a printed circuit board by reactive sputtering and investigated the substrate dependence of its soft magnetic property. Atomic force microscopy and grazing incidence x-ray-scattering-diffraction spectra show that a rough substrate surface degrades the magnetic property of CoFeHfO thin films with almost the same crystal microstructure. With surface planarization by chemical-mechanical polishing, soft magnetic material CoFeHfO can be realized on the package substrate. This material is promising for future applications in package.

Mechanical Reliability of Embedded Array Capacitors in Ultrahigh-Performance Microprocessors

Increasing power delivery and performance requirements for next-generation Intel microprocessors has led to the need for a high-capacitance low-inductance decoupling option very close to the die. An embedded array capacitor (EAC) is a large array capacitor embedded in the high-density interconnect (HDI) substrate core and provides a low-inductance path to the die. This paper describes technology development challenges encountered while enabling EACs on Intels advanced microprocessors. Various package interfaces resulting from the EAC embedding showed very high stress and propensity to delaminate. These defects were addressed by tailoring suitable materials and process modifications during the manufacturing process. Expansion of the embedding material in the HDI substrate resulted in high C4 area warpage. This led to issues such as solder bump bridging, underfill voids, and reliability fails. The technology development challenges and the solution paths described in this paper are very useful to industry in understanding the integration of advanced decoupling options in ultrahigh-performance microprocessor packages.

On-package magnetic materials for embedded inductor applications

Emerging applications in microwave communication, RFIC, and power delivery system are driving the need for the miniaturization, cost-reduction and quality optimization of inductors. In our prior work, high-quality-factor and low-resistance embedded inductors were fabricated on low-cost printed circuit board (PCB) for system-on-package applications. The inductor with a CoFeHfO magnetic core patterned by sand-blasting experimentally produced an inductance gain of ~12% over the air-core inductor. In order to further improve the inductance gain, we looked at alternative processes and materials to use in the fabrication of magnetic cores. In this paper, we investigated and compared the magnetic properties of CoFeHfO magnetic cores on the PCB substrate patterned by both wet-etching and sandblasting. The magnetic domain images by Kerr microscopy, hysteresis loops and permeability spectra clearly showed that the CoFeHfO core patterned by wet-etching had a 3× larger permeability value and softer magnetic properties than the core patterned by sand-blasting. With the implementation of the CoFeHfO core by wet-etching, the theoretic calculation predicted an inductance gain of 32% for our embedded inductor. Besides CoFeHfO, we also explored the magnetic properties of CoTaZr film deposited on the same PCB substrate and measured its permeability value to be ~600, which theoretically indicated a gain of 128% for the inductor we designed.

High Frequency Responses of Granular Magnetic Material CoFeHfO and Amorphous Material CoZrTa

This paper compares the permeability spectra of granular CFHO and amorphous CoZrTa (CZT) thin films with different thickness and laminated structures, and show that granular CFHO has much better high-frequency response and can be an excellent candidate for high-frequency applications.

Integration of RF Inductors and Baluns in Multilayer Organic Substrates

This paper discusses the design, modeling and characterization of RF inductors and baluns in a multilayer organic substrate. In the first part of the paper, we systematically look at two types of spiral inductors for RF applications. More than 40 multi-turn spiral inductors covering inductance values from a few nH to 20 nH have been fabricated and fully characterized. Single turn inductors suitable for high-frequency applications with inductance values in the sub-nH range have also been fabricated and evaluated. In the second part of the paper, we discuss the design of a Marchand-type balun for 2.4 GHz Bluetooth and WLAN application. This 50:100-Ohm balun design employs staggered trace arrangement which results in improved insertion loss and robust performance. Both measurement and simulation data are presented to validate the package-embedded components.Copyright