Journal Article

FZJ-2014-03495

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Influence of stoichiometry on the performance of MIM capacitors from plasma-assisted ALD Sr x Ti y O z films

Aslam, N. (Corresponding Author)FZJ* ; Longo, V. ; Keuning, W. ; Roozeboom, F. ; Kessels, W. M. M. ; Waser, R.FZJ* ; Hoffmann-Eifert, S.FZJ*

2014
Wiley-VCH Weinheim

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Please use a persistent id in citations: doi:10.1002/pssa.201330101

Abstract: Strontium titanate, SrxTiyOz (STO), thin films with various cation stoichiometries were deposited by plasma-assisted atomic layer deposition (ALD) using cyclopentadienyl-based metal precursors and oxygen plasma as counter-reactant. [Sr]/([Sr] + [Ti]) compositions ranging from 0.46 to 0.57 were obtained by changing the (SrO)/(TiO2) ALD cycle ratios. As-deposited 15–30 nm thick SrxTiyOz films prepared at 350 °C on Pt-coated silicon substrates were amorphous. Post-annealing at 600/650 °C for 10 min under N2 gas resulted in a crystallization into the perovskite phase. Stoichiometric STO and Sr-rich STO films exhibited a certain degree of (111) texture while the Ti-rich STO films showed a lower degree of crystallization. Crystallized layers exhibited a smaller band gap Eg than amorphous ones, while within the stoichiometry series the value of Eg increased with increasing Sr-content. Within the stoichiometry series Pt/STO/Pt structures with Sr-rich STO films showed the lowest leakage current densities. At 1.0 V values of about 2 × 10−8 and 5 × 10−6 A cm−2 were obtained for the as-deposited and the annealed films, respectively. Highest capacitance density was obtained for 15 nm polycrystalline stoichiometric SrTiO3 films resulting in a capacitor equivalent thickness CET of about 0.7 nm. Pt/SrxTiyOz/Pt capacitors with the STO being in amorphous state exhibited a positive voltage nonlinearity factor α of about 400 ppm V−2, while the negative α-values for crystallized films showed a systematic variation with the stoichiometry, the degree of crystallization and the thickness of the STO layer. This demonstrates that a broad performance range of MIM capacitors is accessible by controlling the stoichiometry and the degree of crystallization of plasma-assisted ALD SrxTiyOz thin films.

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Contributing Institute(s):

1. Elektronische Materialien (PGI-7)

Research Program(s):

1. 424 - Exploratory materials and phenomena (POF2-424) (POF2-424)

Appears in the scientific report 2014

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Database coverage:
; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection ; Zoological Record

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