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Lateral growth and three-dimensional effects in contacts between NiSi0.82Ge0.18 and p(+)-Si0.82Ge0.18
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
Uppsala University, Ångström Laboratory, Materials Science.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
2005 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 489, no 1-2, 159-163 p.Article in journal (Refereed) Published
Abstract [en]

Electrical contacts of NiSi0.82Ge0.18 to P+-Si0.82Ge0.18 were fabricated and characterised. Lateral growth of the NiSi0.82Ge0.18 under SiO2 isolation was observed. A three-dimensional model was employed to extract the contact resistivity by considering both the lateral growth and the presence of a recessed NiSi0.82Ge0.18 step into the Si0.82Ge0.18. The contact resistivity extracted was 5.0 x 10(-8) and 1.4 x 10(-7) Omega cm(2) for small contacts of circular geometry and large contacts of square shape, respectively. Possible causes responsible for this 3-fold difference in contact resistivity were discussed. An underestimate of the contact resistivity by 35% was found if a two-dimensional model was used without taking into account the complex interface morphology.

Place, publisher, year, edition, pages
2005. Vol. 489, no 1-2, 159-163 p.
Keyword [en]
nickel silicides, silicon-germanium, contacts, interfaces
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9105DOI: 10.1016/j.tsf.2005.04.090ISI: 000231435400025Scopus ID: 2-s2.0-23144447233OAI: oai:DiVA.org:kth-9105DiVA: diva2:14961
Note
QC 20101028. Uppdaterad från accepted till published (20101028).Available from: 2005-02-02 Created: 2005-02-02 Last updated: 2010-10-28Bibliographically approved
In thesis
1. Source and drain engineering in SiGe-based pMOS transistors
Open this publication in new window or tab >>Source and drain engineering in SiGe-based pMOS transistors
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

A new shallow junction formation process, based on selective silicon etching followed by selective growth of in situ B-doped SiGe, is presented. The approach is advantageous compared to conventional ion implantation followed by thermal activation, because perfectly abrupt, low resistivity junctions of arbitrary depth can be obtained. In B-doped SiGe layers, the active doping concentration can exceed the solid solubility in silicon because of strain compensation. In addition, the compressive strain induced in the Si channel can improve drivability through increased hole mobility. The process is integrated by performing the selective etching and the selective SiGe growth in the same reactor. The main advantage of this is that the delicate gate oxide is preserved. The silicon etching process (based on HCl) is shown to be highly selective over SiO2 and anisotropic, exhibiting the densely packed (100), (311) and (111) surfaces. It was found that the process temperature should be confined between 800 ºC, where etch pits occur, and 1000 ºC, where the masking oxide is attacked. B-doped SiGe layers with a resistivity of 5×10-4 Ωcm were obtained. Well-behaved pMOS transistors are presented, yet with low layer quality. Therefore integration issues related to the epitaxial growth, such as selectivity, loading effect, pile-up and defect generation, were investigated. Surface damage originating from reactive-ion etching of the sidewall spacer and nitride residues from LOCOS formation were found to degrade the quality of the SiGe layer. Various remedies are discussed. Nevertheless, high-quality selective epitaxial growth could not be achieved with a doping concentration in the 1021 cm-3 range. The maximum doping level resulting in a high-quality layer, with the loading effect taken into account, was 6×1020 cm-3. After this careful process optimization, a high-quality layer was obtained in the recessed areas. Finally, Ni mono-germanosilicide was investigated as a material for contact formation to the epitaxial SiGe layers in the recessed source and drain areas. The formation temperature is 550 ºC and it is stable up to 700 ºC. The observation of a recessed step and lateral growth of the silicide led to a detailed treatment of the contact resistivity of the NiSi0.8Ge0.2/Si0.8Ge0.2 interface using 2-D as well as 3-D modeling. Different values were obtained for square shaped and rounded contacts, 5.0x10-8 Ωcm2 and 1.4x10-7 Ωcm2, respectively.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xii, 54 p.
Series
Trita-EKT, ISSN 1650-8599 ; 2005:1
Keyword
Electronics, SiGe, source/drain, shallow junctions, pMOS, process integration, CVD, epitaxy, etching, Ni silicide, contact resistivity, Elektronik
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-96 (URN)
Public defence
2005-01-14, C1, Electrum, Isafjordsgatan 22, Kista, 10:15
Opponent
Supervisors
Note
QC 20101028Available from: 2005-02-02 Created: 2005-02-02 Last updated: 2010-10-28Bibliographically approved

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