TY  - JOUR
AU  - Aslam, N.
AU  - Longo, V.
AU  - Keuning, W.
AU  - Roozeboom, F.
AU  - Kessels, W. M. M.
AU  - Waser, R.
AU  - Hoffmann-Eifert, S.
TI  - Influence of stoichiometry on the performance of MIM capacitors from plasma-assisted ALD Sr x Ti y O z films
JO  - Physica status solidi / A
VL  - 211
IS  - 2
SN  - 1862-6300
CY  - Weinheim
PB  - Wiley-VCH
M1  - FZJ-2014-03495
SP  - 389 - 396
PY  - 2014
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000332000500020
DO  - DOI:10.1002/pssa.201330101
UR  - https://juser.fz-juelich.de/record/154093
ER  -