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Spin Torque Oscillator Modeling, CMOS Design and STO-CMOS Integration
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.ORCID iD: 0000-0002-1686-7923
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Spin torque oscillators (STOs) are microwave oscillators with an attractive blend of features, including a more-than-octave tunability, GHz operating frequencies, nanoscale size, nanosecond switching speed and full compatibility with CMOS technology. Over the past decade, STOs' physical phenomena have been explored to a greater extent, their performance has been further improved, and STOs have already shown great potential for a wide range of applications, from microwave sources and detectors to neuromorphic computing. This thesis is devoted to promoting the STO technology towards its applications, by means of implementing the STO's electrical model, dedicated CMOS integrated circuits (ICs), and STO-CMOS IC integration.

An electrical model, which can capture magnetic tunnel junction (MTJ) STO's characteristics, while enabling system- and circuit-level designs and performance evaluations, is of great importance for the development of MTJ STO-based applications. A comprehensive and compact analytical model, which is based on macrospin approximations and can fulfill the aforementioned requirements, is proposed. This model is fully implemented in Verilog-A, and can be used for efficient simulations of various MTJ STOs. Moreover, an accurate phase noise generation approach, which ensures a reliable model, is proposed and successfully used in the Verilog-A model implementation. The model is experimentally validated by three different MTJ STOs under different bias conditions.

CMOS circuits, which can enhance the limited output power of MTJ STOs to levels that are required in different applications, are proposed, implemented and tested. A novel balun-low noise amplifier (LNA), which can offer sufficient gain, bandwidth and linearity for MTJ STO-based magnetic field sensing applications, is proposed. Additionally, a wideband amplifier, which can be connected to an MTJ STO to form a highly-tunable microwave oscillator in a phase-locked loop (PLL), is also proposed. The measurement results demonstrate that the proposed circuits can be used to develop MTJ STO-based magnetic field sensing and microwave source applications.

The investigation of possible STO-CMOS IC integration approaches demonstrates that the wire-bonding-based integration is the most suitable approach. Therefore, a giant magnetoresistance (GMR) STO is integrated with its dedicated CMOS IC, which provides the necessary functions, using the wire-bonding-based approach. The RF characterization of the integrated GMR STO-CMOS IC system under different magnetic fields and DC currents shows that such an integration can eliminate wave reflections. These findings open the possibility of using GMR STOs in magnetic field sensing and microwave source applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xxvi, 81 p.
Series
TRITA-ICT, 2015:19
Keyword [en]
STO technology, microwave oscillator, analytical model, macrospin approximation, Verilog-A model, high frequency CMOS circuits, balun-LNA, STO-IC integration
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Information and Communication Technology
Identifiers
URN: urn:nbn:se:kth:diva-176890ISBN: 978-91-7595-750-0 (print)OAI: oai:DiVA.org:kth-176890DiVA: diva2:868790
Public defence
2015-12-07, Sal C, Isafjordsgatan 22, Kista, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note

QC 20151112

Available from: 2015-11-12 Created: 2015-11-11 Last updated: 2015-11-12Bibliographically approved
List of papers
1. A 2 GHz - 8.7 GHz Wideband Balun-LNA with Noise Cancellation and Gain Boosting
Open this publication in new window or tab >>A 2 GHz - 8.7 GHz Wideband Balun-LNA with Noise Cancellation and Gain Boosting
2012 (English)In: PRIME 2012: Proceedings of the 8th Coference on Ph.D. Research in Microelectronics and Electronics, 2012, IEEE conference proceedings, 2012, 59-62 p.Conference paper, Oral presentation only (Refereed)
Abstract [en]

A wideband Balun-LNA covering the operation frequency range of magnetic tunnel junction Spin Torque Oscillator is presented. The LNA is a combination of common-source and cross-coupled common-gate stages, which provides wideband matching and noise cancellation, as well as gain boosting. The internal feedback introduced by the cross-coupling allows an additional degree of freedom to select transistor sizes and bias by decoupling the impedance matching, noise, and gain imbalance trade-offs which are present in similar topologies. Two LNAs using the proposed technique are designed in 65nm CMOS. The LNAs have a simulated bandwidth of  2 GHz - 8.7 GHz, gain of 16 dB, IIP3 of -3.5 dBm,  and NF < 3.8 dB while consuming 3.72 mW from a 1.2 V power supply.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2012
Keyword
Decision support systems, Hafnium, Inductors, MOS devices, Noise measurement, Radio frequency
National Category
Engineering and Technology Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-116464 (URN)2-s2.0-85007301689 (Scopus ID)978-3-8007-3442-9 (ISBN)
Conference
8th Coference on Ph.D. Research in Microelectronics and Electronics (PRIME), Aachen, June 12-15, 2012
Funder
Swedish Research Council
Note

QC 20130114

Available from: 2013-02-04 Created: 2013-01-18 Last updated: 2015-11-12Bibliographically approved
2. A highly tunable microwave oscillator based on MTJ STO technology
Open this publication in new window or tab >>A highly tunable microwave oscillator based on MTJ STO technology
Show others...
2014 (English)In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 56, no 9, 2092-2095 p.Article in journal (Refereed) Published
Abstract [en]

This article presents a fully ESD-protected, highly tunable microwave oscillator based on magnetic tunnel junction (MTJ) spin torque oscillator (STO) technology. The oscillator consists of a compact MTJ STO and a 65 nm CMOS wideband amplifier, which amplifies the RF signal of the MTJ STO to a level that can be used to drive a PLL. The (MTJ STO+amplifier IC) pair shows a measured quality factor (Q) of 170 and a wide tunability range from 3 to 7 GHz, which demonstrate its potential to be used as a microwave oscillator in multiband, multistandard radios.

Keyword
spin torque oscillator, CMOS, microwave, wideband, highly tunable
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-149496 (URN)10.1002/mop.28511 (DOI)000339439000033 ()2-s2.0-84903286907 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20140822

Available from: 2014-08-22 Created: 2014-08-22 Last updated: 2017-12-05Bibliographically approved
3. An Inductorless Wideband Balun-LNA for Spin Torque Oscillator-based Field Sensing
Open this publication in new window or tab >>An Inductorless Wideband Balun-LNA for Spin Torque Oscillator-based Field Sensing
2014 (English)In: Electronics, Circuits and Systems (ICECS), 2014 21st IEEE International Conference on, IEEE conference proceedings, 2014, 36-39 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents a wideband inductorless Balun-LNA targeting spin torque oscillator-based magnetic field sensing applications. The LNA consistsof a CS stage combined with a cross-coupled CG stage, which offers wideband matching, noise/distortion cancellation and gain boosting, simultaneously. The Balun-LNA is implemented in a 65 nm CMOS technology, and it is fully ESD-protected and packaged. Measurement results show a bandwidth of 2 GHz - 7 GHz, a voltage gain of 20 dB, an IIP3 of +2 dBm, and a maximum NF of 5 dB. The LNA consumes 3.84 mW from a 1.2 V power supply and occupies a total silicon area of 0.0044 mm2. The measurement results demonstrate that the proposed Balun-LNA is highly suitable for the STO-based field sensing applications.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2014
Keyword
Gain, Impedance matching, Magnetic tunneling, Noise measurement, Sensors, Wideband
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-157778 (URN)10.1109/ICECS.2014.7049915 (DOI)2-s2.0-84925447228 (Scopus ID)978-1-4799-4243-5 (ISBN)
Conference
The 21st IEEE International Conference on Electronics, Circuits and Systems (ICECS),December 7-10, 2014 Marseille, France
Note

QC 20150210

Available from: 2014-12-15 Created: 2014-12-15 Last updated: 2015-11-12Bibliographically approved
4. Comprehensive and Macrospin-Based Magnetic Tunnel Junction Spin Torque Oscillator Model-Part I: Analytical Model of the MTJ STO
Open this publication in new window or tab >>Comprehensive and Macrospin-Based Magnetic Tunnel Junction Spin Torque Oscillator Model-Part I: Analytical Model of the MTJ STO
Show others...
2015 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 62, no 3, 1037-1044 p.Article in journal (Refereed) Published
Abstract [en]

Magnetic tunnel junction (MTJ) spin torque oscillators (STOs) have shown the potential to be used in a wide range of microwave and sensing applications. To evaluate the potential uses of MTJ STO technology in various applications, an analytical model that can capture MTJ STO's characteristics, while enabling system-and circuit-level designs, is of great importance. An analytical model based on macrospin approximation is necessary for these designs since it allows implementation in hardware description languages. This paper presents a new macrospin-based, comprehensive, and compact MTJ STO model, which can be used for various MTJ STOs to estimate the performance of MTJ STOs together with their application-specific integrated circuits. To adequately present the complete model, this paper is divided into two parts. In Part I, the analytical model is introduced and verified by comparing it against measured data of three different MTJ STOs, varying the angle and magnitude of the magnetic field, as well as the DC biasing current. The proposed analytical model is suitable for being implemented in Verilog-A and used for efficient simulations at device, circuit, and system levels. In Part II, the full Verilog-A implementation of the analytical model with accurate phase noise generation is presented and verified by simulations.

Keyword
Analytical model, macrospin, magnetic tunnel junction (MTJ), spin torque oscillator (STO)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-163459 (URN)10.1109/TED.2015.2390411 (DOI)000350332000051 ()2-s2.0-84923687907 (Scopus ID)
Funder
Swedish Research Council, 2009-4190
Note

QC 20150408

Available from: 2015-04-08 Created: 2015-04-07 Last updated: 2017-12-04Bibliographically approved
5. Comprehensive and Macrospin-Based Magnetic Tunnel Junction Spin Torque Oscillator Model-Part II: Verilog-A Model Implementation
Open this publication in new window or tab >>Comprehensive and Macrospin-Based Magnetic Tunnel Junction Spin Torque Oscillator Model-Part II: Verilog-A Model Implementation
Show others...
2015 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 62, no 3, 1045-1051 p.Article in journal (Refereed) Published
Abstract [en]

The rapid development of the magnetic tunnel junction (MTJ) spin torque oscillator (STO) technology demands an analytical model to enable building MTJ STO-based circuits and systems so as to evaluate and utilize MTJ STOs in various applications. In Part I of this paper, an analytical model based on the macrospin approximation has been introduced and verified by comparing it with the measurements of three different MTJ STOs. In Part II, the full Verilog-A implementation of the proposed model is presented. To achieve a reliable model, an approach to reproducing the phase noise generated by the MTJ STO has been proposed and successfully employed. The implemented model yields a time domain signal, which retains the characteristics of operating frequency, linewidth, oscillation amplitude, and DC operating point, with respect to the magnetic field and applied DC current. The Verilog-A implementation is verified against the analytical model, providing equivalent device characteristics for the full range of biasing conditions. Furthermore, a system that includes an MTJ STO and CMOS RF circuits is simulated to validate the proposed model for system-and circuit-level designs. The simulation results demonstrate that the proposed model opens the possibility to explore STO technology in a wide range of applications.

Keyword
Analytical model, macrospin, magnetic tunnel junction (MTJ), spin torque oscillator (STO)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-163460 (URN)10.1109/TED.2015.2390676 (DOI)000350332000052 ()2-s2.0-84923688220 (Scopus ID)
Funder
Swedish Research Council, 2009-4190
Note

QC 20150408

Available from: 2015-04-08 Created: 2015-04-07 Last updated: 2017-12-04Bibliographically approved
6. Integration of GMR-based spin torque oscillators and CMOS circuitry
Open this publication in new window or tab >>Integration of GMR-based spin torque oscillators and CMOS circuitry
Show others...
2015 (English)In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 111, 91-99 p.Article in journal (Refereed) Published
Abstract [en]

This paper demonstrates the integration of giant magnetoresistance (GMR) spin torque oscillators (STO) with dedicated high frequency CMOS circuits. The wire-bonding-based integration approach is employed in this work, since it allows easy implementation, measurement and replacement. A GMR STO is wire-bonded to the dedicated CMOS integrated circuit (IC) mounted on a PCB, forming a (GMR STO + CMOS IC) pair. The GMR STO has a lateral size of 70 nm and more than an octave of tunability in the microwave frequency range. The proposed CMOS IC provides the necessary bias-tee for the GMR STO, as well as electrostatic discharge (ESD) protection and wideband amplification targeting high frequency GMR STO-based applications. It is implemented in a 65 nm CMOS process, offers a measured gain of 12 dB, while consuming only 14.3 mW and taking a total silicon area of 0.329 mm2. The measurement results show that the (GMR STO + CMOS IC) pair has a wide tunability range from 8 GHz to 16.5 GHz and improves the output power of the GMR STO by about 10 dB. This GMR STO-CMOS integration eliminates wave reflections during the signal transmission and therefore exhibits good potential for developing high frequency GMR STO-based applications, which combine the features of CMOS and STO technologies.

Keyword
CMOS, Giant magnetoresistance, Integration, On-chip bias-tee, Spin torque oscillator, Wire bonding
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-170209 (URN)10.1016/j.sse.2015.05.037 (DOI)000358294500016 ()2-s2.0-84930627106 (Scopus ID)
Note

QC 20150629

Available from: 2015-06-29 Created: 2015-06-29 Last updated: 2017-12-04Bibliographically approved
7. Spin-Torque and Spin-Hall Nano-Oscillators
Open this publication in new window or tab >>Spin-Torque and Spin-Hall Nano-Oscillators
Show others...
(English)In: Proceedings of the IEEE, ISSN 0018-9219, E-ISSN 1558-2256Article in journal (Refereed) Submitted
Abstract [en]

This paper reviews the state of the art in spin-torque and spin Hall effect driven nano-oscillators. After a brief introduction to the underlying physics, the authors discuss different implementations of these oscillators, their functional properties in terms of frequency range, output power, phase noise, and modulation rates, and their inherent propensity for mutual synchronization. Finally, the potential for these oscillators in a wide range of applications, from microwave signal sources and detectors to neuromorphic computation elements, is discussed together with the specific electronic circuitry that has so far been designed to harness this potential.

Keyword
Spintronics, Microwaves, Spin transfer torque, Spin Hall effect
National Category
Nano Technology Electrical Engineering, Electronic Engineering, Information Engineering Materials Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-176889 (URN)
Note

QS 2016

Available from: 2015-11-11 Created: 2015-11-11 Last updated: 2017-12-01Bibliographically approved

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