Selected Publications - 2006:
1) Thermal Stability of Praseodymium silicate high-k layers on Si(100)
G. Lupina, T. Schroeder, Ch. Wenger, J. Dabrowski, and H.-J. Müssig
IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
Applied Physics Letters Vol. 89, 222909 (2006).
The thermal stability of amorphous Praseodymium (Pr) silicate high-k layers on Si(001) in view of CMOS processing requirements was evaluated by a combination of materials science and electric characterization techniques. XPS and XRd studies confirm that no crystallization, no phase separation into SiO2 and Pr2O3, and no Pr silicide formation at the interface occurs after 1 min rapid thermal annealing treatments in N2 over the temperature range from 600 to 900°C. C-V and J-V measurements confirm within this thermal budget well-behaved electrical characteristics with k-values between 11 and 13 and leakage currents ~ 3 orders of magnitude lower than in case of silicon oxynitride reference layers.
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2) Praseodymium silicate films on Si(100) for gate dielectric applications: physical and electrical characterization
G. Lupina, T. Schroeder, J. Dabrowski, Ch. Wenger, A.U. Mane, H.-J. Müssig, P. Hoffmann*, and D. Schmeißer*
IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
* BTU Cottbus, PF 101344, 03013 Cottbus, Germany
Journal of Applied Physics (October 2005).
Praseodymium (Pr) silicate dielectric layers were prepared by oxidation and subsequent N2 annealing of thin Pr metal layers on SiO2 / Si(100) substrates. Transmission electron microscopy studies reveal that the resulting dielectric has a bilayer structure. Nondestructive depth profiling by using synchrotron radiation x-ray photoelectron spectroscopy shows that, starting from the substrate, the dielectric stack is composed of a SiO2-rich and a SiO2-poor Pr silicate phase. Valence and conduction band offsets of about 2.9 and 1.6 eV, respectively, between the dielectric and the Si(100) substrate bands were deduced. Pr silicate films with an equivalent oxide thickness of 1.8 nm show approximately three orders of magnitude lower leakage currents than silicon oxynitride references. Capacitance versus voltage measurements of the Pr silicate / Si(100) system report a flat band voltage shift of 0.22 V, an effective dielectric constant of about 11 and a reasonably good interface quality with an interface state density on the order of 1011 cm-2. Experimental results are supplemented by ab initio considerations which review the most probable mechanisms of fixed charge formation in the Pr silicate layers.
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