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Norström, Hans
Publications (10 of 25) Show all publications
Hu, Q., Chen, X., Norström, H., Zeng, S., Yifei, L., Fredrik, G., . . . Zhang, Z. (2018). Current gain and low-frequency noise of symmetriclateral bipolar junction transistors on SOI. In: : . Paper presented at 48th European Solid-State Device Research Conference, September 3 - 6, 2018, Dresden, Germany.
Open this publication in new window or tab >>Current gain and low-frequency noise of symmetriclateral bipolar junction transistors on SOI
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2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents a comprehensive study ofsymmetric lateral bipolar junction transistors (LBJTs) fabricatedon SOI substrate using a CMOS-compatible process; LBJTs findmany applications including being a local signal amplifier forsilicon-nanowire sensors. Our LBJTs are characterized by a peakgain (β) over 50 and low-frequency noise two orders ofmagnitude lower than what typically is of the SiO2/Si interfacefor a MOSFET. β is found to decrease at low base current due torecombination in the space charge region at the emitter-basejunction and at the surrounding SiO2/Si interfaces. This decreasecan be mitigated by properly biasing the substrate.

Keywords
symmetric lateral bipolar junction transitor; current amplification; low frequency noise; silicon nanowire field-effect transitor
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-364155 (URN)
Conference
48th European Solid-State Device Research Conference, September 3 - 6, 2018, Dresden, Germany
Note

Qitao Hu and Xi Chen contribute equally to the work.

Available from: 2018-10-24 Created: 2018-10-24 Last updated: 2019-04-03Bibliographically approved
Zetterling, C.-M., Hallen, A., Hedayati, R., Kargarrazi, S., Lanni, L., Malm, B. G., . . . Ostling, M. (2017). Bipolar integrated circuits in SiC for extreme environment operation. Semiconductor Science and Technology, 32(3), Article ID 034002.
Open this publication in new window or tab >>Bipolar integrated circuits in SiC for extreme environment operation
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2017 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, no 3, article id 034002Article in journal (Refereed) Published
Abstract [en]

Silicon carbide (SiC) integrated circuits have been suggested for extreme environment operation. The challenge of a new technology is to develop process flow, circuit models and circuit designs for a wide temperature range. A bipolar technology was chosen to avoid the gate dielectric weakness and low mobility drawback of SiC MOSFETs. Higher operation temperatures and better radiation hardness have been demonstrated for bipolar integrated circuits. Both digital and analog circuits have been demonstrated in the range from room temperature to 500 degrees C. Future steps are to demonstrate some mixed signal circuits of greater complexity. There are remaining challenges in contacting, metallization, packaging and reliability.

Keywords
SiC, integrated circuit, high temperature, radiation hardness, bipolar technology
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-340169 (URN)10.1088/1361-6641/aa59a7 (DOI)000413488700001 ()
Funder
Swedish Foundation for Strategic Research
Available from: 2018-01-31 Created: 2018-01-31 Last updated: 2018-01-31Bibliographically approved
Mardani, S., Norström, H., Smith, U., Gustavsson, F., Olsson, J. & Zhan, S.-L. (2016). Electromigration behavior of Cu metallization interfacing with Ta versus TaN at high temperatures. Journal of Vacuum Science & Technology B, 34(6), Article ID 060603.
Open this publication in new window or tab >>Electromigration behavior of Cu metallization interfacing with Ta versus TaN at high temperatures
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2016 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 34, no 6, article id 060603Article in journal (Refereed) Published
Abstract [en]

High-temperature stability of Cu-based interconnects is of technological importance for electronic circuits based on wide band gap semiconductors. In this study, different metal stack combinations using Ta or TaN as capping- and/or barrier-layer, in the configuration cap/Cu/barrier, are evaluated electrically and morphologically prior to and after high-temperature treatments. The symmetric combinations Ta/Cu/Ta and TaN/Cu/TaN are characterized by a low and stable sheet resistance after annealing up to 700 °C. Asymmetric combinations of Ta/Cu/TaN and TaN/Cu/Ta, however, display an increase in sheet resistance values after annealing at 500 °C and above. This increase in sheet resistance is considered to result from Ta diffusion into the grain boundaries of the Cu film. The preliminary electromigration studies on the TaN/Cu/Ta and TaN/Cu/TaN structures show a twofold higher activation energy and a tenfold longer lifetime for the former, thus suggesting an important role of the interface between Cu and the cap and/or barrier.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-300795 (URN)10.1116/1.4967372 (DOI)000389530000054 ()
Funder
Swedish Foundation for Strategic Research , RE10-0011Swedish Foundation for Strategic Research , RIF-14-0053
Available from: 2016-08-13 Created: 2016-08-13 Last updated: 2017-11-28Bibliographically approved
Mardani, S., Norström, H., Smith, U. & Zhang, S.-L. (2016). High-temperature Ta diffusion in the grain boundary of thin Cu films. Journal of Vacuum Science & Technology B, 34, Article ID 040606.
Open this publication in new window or tab >>High-temperature Ta diffusion in the grain boundary of thin Cu films
2016 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 34, article id 040606Article in journal (Refereed) Published
Abstract [en]

In order to ascertain the applicability of the technologically well-established Cu metallization in high-temperature circuits, the authors have investigated layered metal stacks having one Ta/Cu interface at temperatures from 400 to 700 degrees C. The authors have found that Ta releases from the Ta layer and moves through the Cu film to the opposite interface via the grain boundaries. In the simplest bilayer stack with Cu on top of Ta, the up-diffused Ta on the surface spreads out over the Cu grains so as to cover the Cu grains completely at 650 degrees C. The activation energy for the grain boundary diffusion is found to be 1.060.3 eV. The Ta diffusion in the grain boundaries leads to stabilization of the Cu grain size at 360 nm and an increase in sheet resistance of the metal stack. The latter is in fact observed for all metal stacks having Cu in contact with Ta on one side and TaN or nothing at all on the other. The implication is that the Cu metallization with one Ta/Cu interface has to be stabilized by a preanneal at the highest anticipated operating temperature before use.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-294767 (URN)10.1116/1.4950744 (DOI)000382207700006 ()
Funder
Swedish Foundation for Strategic Research , RE10-0011
Available from: 2016-05-27 Created: 2016-05-27 Last updated: 2017-11-30Bibliographically approved
Mardani, S., Norström, H., Gustavsson, F., Nyberg, T., Primetzhofer, D., Leifer, K., . . . Zhang, S.-L. (2016). Massive Ta diffusion observed in Cu thin films but not in Ag counterparts. Journal of Vacuum Science & Technology B, 34(6), Article ID 060604.
Open this publication in new window or tab >>Massive Ta diffusion observed in Cu thin films but not in Ag counterparts
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2016 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 34, no 6, article id 060604Article in journal (Refereed) Published
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-307813 (URN)10.1116/1.4968418 (DOI)000389530000055 ()
Funder
Swedish Foundation for Strategic Research , RE10-0011Swedish Foundation for Strategic Research , RIF-14-0053Swedish Research Council, VR-RFI C0514401Swedish Foundation for Strategic Research , RIF14-0053
Available from: 2016-11-21 Created: 2016-11-21 Last updated: 2019-04-24Bibliographically approved
Mardani, S., Norström, H., Smith, U., Olsson, J. & Zhang, S.-L. (2015). Influence of tantalum/tantalum nitride barriers and caps on the high-temperature properties of copper metallization for wide-band gap applications. Microelectronic Engineering, 137, 37-42
Open this publication in new window or tab >>Influence of tantalum/tantalum nitride barriers and caps on the high-temperature properties of copper metallization for wide-band gap applications
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2015 (English)In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 137, p. 37-42Article in journal (Refereed) Published
Abstract [en]

Electronic devices and circuits based on wide-band gap (WBG) semiconductors and intended for operation at temperatures significantly exceeding 300 degrees C are currently being developed. It is important that the adjunct metallization matches the high-temperature properties of the devices. In the case of the technologically important Cu metallization, the most frequently used cap and barrier layer materials are Ta, TaN and combinations of these. They stabilize the interconnects and prevent Cu from diffusing into the surrounding material. In this study, different combinations of Ta and TaN layers are evaluated electrically and morphologically after high-temperature treatments. The cap/Cu/barrier stack shows an appreciable increase in sheet resistance above 600 degrees C for the asymmetric combinations Ta/Cu/TaN and TaN/Cu/Ta. This degradation is shown to be closely related to a substantial diffusion of Ta across the Cu film and on to the TaN layer, where Ta1+xN forms. The symmetrical combinations Ta/Cu/Ta and TaN/Cu/TaN show only small changes in sheet resistance on even after anneals at 800 degrees C. A less pronounced Ta diffusion into the Cu film is found for the Ta/Cu/Ta combination. The experimental observations are interpreted in terms of Cu grain growth, Ta segregation in the Cu grain boundaries and morphological degradation of the Cu film.

Keywords
Wide band gap application, Copper metallization, High-temperature, Tantalum, Tantalum nitride
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-256858 (URN)10.1016/j.mee.2015.01.023 (DOI)000355047500008 ()
Funder
Swedish Research Council, 2010-4460
Available from: 2015-06-26 Created: 2015-06-26 Last updated: 2017-12-04Bibliographically approved
Mardani, S., Primetzhofer, D., Liljeholm, L., Vallin, Ö., Norström, H. & Olsson, J. (2014). Electrical properties of Ag/Ta and Ag/TaN thin-films. Paper presented at MAM 2013 - Materials for Advanced Metallization; 10-13 March 2013; Leuven, Belgium. Microelectronic Engineering, 120, 257-261
Open this publication in new window or tab >>Electrical properties of Ag/Ta and Ag/TaN thin-films
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2014 (English)In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 120, p. 257-261Article in journal (Refereed) Published
Abstract [en]

Although wide band gap devices (WBG, e.g. GaN and SiC) are eminently suitable for high temperatures and harsh environments, these properties cannot be fully taken advantage of without an appropriate interconnect metallization. In this context, silver shows promise for interconnections at high temperatures. In this work, the thermal stability of Ag with two barrier metals – Ta and TaN – was therefore investigated. Metal stacks, consisting of 100 nm of silver on 45 nm of either Ta or TaN were sputter-deposited on the substrate. Each metal system was annealed in vacuum for one hour at temperatures up to 800 °C. Both systems showed stable performance up to 600 °C. The system with Ta as a barrier metal was found to be more stable than the TaN system. Above 700 °C, silver agglomeration led to degradation of electrical performance.

Keywords
Interconnect, Silver, Thermal stability, Ta and TaN diffusion barrier
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-215831 (URN)10.1016/j.mee.2013.06.002 (DOI)000336697300045 ()
Conference
MAM 2013 - Materials for Advanced Metallization; 10-13 March 2013; Leuven, Belgium
Funder
Swedish Foundation for Strategic Research
Available from: 2014-01-17 Created: 2014-01-17 Last updated: 2017-12-06Bibliographically approved
Mardani, S., Norström, H., Olsson, J., Vallin, Ö. & Zhang, S. (2014). High-temperature behaviour of capped Ag/Ta and Ag/TaN metal stacks. In: : . Paper presented at MAM 2014 - Materials for Advanced Metallization, 2-5 March 2014, Chemnitz, Germany (pp. 137-138).
Open this publication in new window or tab >>High-temperature behaviour of capped Ag/Ta and Ag/TaN metal stacks
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2014 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-197278 (URN)
Conference
MAM 2014 - Materials for Advanced Metallization, 2-5 March 2014, Chemnitz, Germany
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Available from: 2014-03-31 Created: 2013-03-21 Last updated: 2014-07-18Bibliographically approved
Mardani, S., Vallin, Ö., Wätjen, J. T., Norström, H., Olsson, J. & Zhang, S. (2014). Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer. Applied Physics Letters, 105, 071604
Open this publication in new window or tab >>Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer
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2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, p. 071604-Article in journal (Refereed) Published
Abstract [en]

Wide-bandgap (WBG) semiconductor technologies are maturing and may provide increased deviceperformance in many fields of applications, such as high-temperature electronics. However, thereare still issues regarding the stability and reliability of WBG devices. Of particular importance isthe high-temperature stability of interconnects for electronic systems based on WBG-semiconductors. For metallization without proper encapsulation, morphological degradation canoccur at elevated temperatures. Sandwiching Ag films between Ta and/or TaN layers in this studyis found to be electrically and morphologically stabilize the Ag metallization up to 800C, com-pared to 600C for uncapped films. However, the barrier layer plays a key role and TaN is found tobe superior to Ta, resulting in the best achieved stability, whereas the difference between Ta andTaN caps is negligible. The b-to-a phase transition in the underlying Ta barrier layer is identifiedas the major cause responsible for the morphological instability observed above 600C. It isshown that this phase transition can be avoided using a stacked Ta/TaN barrier.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-230204 (URN)10.1063/1.4893768 (DOI)000341189800016 ()
Funder
Swedish Research Council, 2010-4460Swedish Foundation for Strategic Research , RE10-0011
Available from: 2014-08-20 Created: 2014-08-20 Last updated: 2017-12-05Bibliographically approved
Johansson, T., Bengtsson, O., Lotfi, S., Vestling, L., Norström, H., Olsson, J. & Nyström, C. (2013). A +32.8 dBm LDMOS power amplifier for WLAN in 65 nm CMOS technology. In: 2013 8th European Microwave Integrated Circuits Conference Proceedings: . Paper presented at European Microwave Integrated Circuits Conference (EuMIC) (pp. 53-56).
Open this publication in new window or tab >>A +32.8 dBm LDMOS power amplifier for WLAN in 65 nm CMOS technology
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2013 (English)In: 2013 8th European Microwave Integrated Circuits Conference Proceedings, 2013, p. 53-56Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Generating high output power at radio frequencies in CMOS becomes more challenging as technology is scaled. Limitations mainly come from device design. We demonstrate the feasibility of an 10 V LDMOS device fabricated in 65 nm foundry CMOS technology with no added process steps or mask. DC, RF, and power characterization are presented which show the feasibility of the device. The LDMOS device is used in an integrated WLAN-PA design and 32.8 dBm linear output power in the 2.45 GHz band is achieved. Load-pull data also shows high output power capability at 5.8 GHz. The concept can also be used at 45 nm and 28 nm nodes in most foundry CMOS processes.

National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-209603 (URN)978-2-87487-032-3 (ISBN)
Conference
European Microwave Integrated Circuits Conference (EuMIC)
Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2014-02-10Bibliographically approved
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