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A Novel Strained Si0.7Ge0.3 Surface-Channel pMOSFET with an ALD TiN/Al2O3/HfAlOx/Al2O3 Gate Stack
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
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2003 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 24, no 3, 171-173 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2003. Vol. 24, no 3, 171-173 p.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:uu:diva-94808OAI: oai:DiVA.org:uu-94808DiVA: diva2:168795
Available from: 2006-09-08 Created: 2006-09-08 Last updated: 2013-11-21
In thesis
1. Metal Gate Technology for Advanced CMOS Devices
Open this publication in new window or tab >>Metal Gate Technology for Advanced CMOS Devices
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development and implementation of a metal gate technology (alloy, compound, or silicide) into metal-oxide-semiconductor field effect transistors (MOSFETs) is necessary to extend the life of planar CMOS devices and enable further downscaling. This thesis examines possible metal gate materials for improving the performance of the gate stack and discusses process integration as well as improved electrical and physical measurement methodologies, tested on capacitor structures and transistors.

By using reactive PVD and gradually increasing the N2/Ar flow ratio, it was found that the work function (on SiO2) of the TiNx and ZrNx metal systems could be modulated ~0.7 eV from low near nMOS work functions to high pMOS work functions. After high-temperature anneals corresponding to junction activation, both metals systems reached mid-gap work function values. The mechanisms behind the work function changes are explained with XPS data and discussed in terms of metal gradients and Fermi level pinning due to extrinsic interface states.

A modified scheme for improved Fowler-Nordheim tunnelling is also shown, using degenerately doped silicon substrates. In that case, the work functions of ALD/PVD TaN were accurately determined on both SiO2 and HfO2 and benchmarked against IPE (Internal Photoemission) results. KFM (Kelvin Force Microscopy) was also used to physically measure the work functions of PVD TiN and Mo deposited on SiO2; the results agreed well with C-V and I-V data.

Finally, an appealing combination of novel materials is demonstrated with ALD TiN/Al2O3/HfAlOx/Al2O3/strained-SiGe surface channel pMOS devices. The drive current and transconductance were measured to be 30% higher than the Si reference, clearly demonstrating increased mobility and the absence of polydepletion. Finally, using similarly processed transistors with Al2O3 dielectric instead, low-temperature water vapour annealing was shown to improve the device characteristics by reducing the negative charge within the ALD Al2O3.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 55 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 213
Electronics, metal gate, high-k dielectrics, titanium nitride, zirconium nitride, MOSFET, thin film, work function, XPS, Elektronik
urn:nbn:se:uu:diva-7120 (URN)91-554-6640-0 (ISBN)
Public defence
2006-09-29, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30
Available from: 2006-09-08 Created: 2006-09-08Bibliographically approved

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