High-mobility materials

Advanced materials for future CMOS generations


Compound semiconductor channels (GaAs, Ge, InGaAs) combined with ultra-thin high-κ dielectrics (HfO2) are a promising approach to fabricate devices offering high performance at lower power. A few key aspects should be mastered, however, in order to fully exploit the potential benefits related to their intrinsically higher carrier velocity. The density of electrically defects between the dielectric and the compound semiconductor channel must be low. The heterostructure used as the conducting channel should be of high quality and provide the optimum carrier velocity, carrier density and band gap. Finally, the complete device structure should be integrated on 200 mm silicon substrates.

The structural properties of the deposited layers are analyzed by reflection high-energy electron diffraction (RHEED), X-ray diffractometry (XRD), ellipsometry, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). The electrical properties of our films (effective oxide thickness, leakage, carrier mobility) are derived from MOS capacitors and FETs, which we fabricate in-house, using our own cleanroom facility. Current-voltage (I-V) and capacitance-voltage (C-V) measurements are performed using standard equipment. The trapped charges at the interface as well as in the bulk of the oxide are investigated by means of several techniques such as the conductance method on MOS and FET structures and the pulse based charge pumping method on MOSFETs.

Part of this work is done in the framework of the EU-funded project DualLogic.


[1] C. Marchiori, D. J. Webb, C. Rossel, M. Richter, M. Sousa, C. Gerl, R. Germann, C. Andersson, and J. Fompeyrine
“H plasma cleaning and a-Si passivation of GaAs for surface channel device applications”
to appear in J. Appl. Phys.

[2] C. Andersson, C. Rossel, M. Sousa, D.J. Webb, C. Marchiori, D. Caimi, H. Siegwart, Y. Panayiotatos, A. Dimoulas, and J. Fompeyrine,
“Lanthanum germanate as dielectric for scaled germanium metal-oxide-semiconductor devices”
Microelectronic Engineering 86, 1635 (2009).

[3] G. Mavrou, P. Tsipas, A. Sotiropoulos, S. Galata, Y. Panayiotatos, A. Dimoulas, C. Marchiori, and J. Fompeyrine
“Very high-κ ZrO2 with La2O3 (LaGeOx) passivating interfacial layers on germanium substrates”
Appl. Phys. Lett. 93, 212904 (2008).

[4] P. Tsipas, S. N. Volkos, A. Sotiropoulos, S. F. Galata, G. Mavrou, D. Tsoutsou, Y. Panayiotatos, A. Dimoulas, C. Marchiori, and J. Fompeyrine
“Germanium-induced stabilization of a very high-κ zirconia phase in ZrO2/GeO2 gate stacks”
Appl. Phys. Lett. 93, 082904 (2008).

[5] J. P. de Souza, E. Kiewra, Y. Sun, A. Callegari, D. K. Sadana, G. Shahidi, D. J. Webb, J. Fompeyrine, R. Germann, C. Rossel, and C. Marchiori,
“Inversion mode n-channel GaAs field effect transistor with high-κ/metal gate”
Appl. Phys. Lett. 92, 153508 (2008).

[6] D.J. Webb, J. Fompeyrine, S. Nakagawa, A. Dimoulas, C. Rossel, M. Sousa, R. Germann, S.F. Alvarado, J.P. Locquet, C. Marchiori, H. Siegwart, A. Callegari, E. Kiewra, Y. Sun, J. De Souza, and N. Hoffmann
“In-situ MBE Si as passivating interlayer on GaAs for HfO2 MOSCAPs: Effect of GaAs surface reconstruction”
Microelectronic Engineering Volume 84, Issues 9-10, 2007, pp. 2142-2145.

[7] Y. Sun, E. W. Kiewra, S. J. Koester, N. Ruiz, A. Callegari, K. E. Fogel, D. K. Sadana, J. Fompeyrine, D. J. Webb, and J.-P. Locquet
“Enhancement-mode buried-channel In0.7Ga0.3As/In0.52Al0.48As MOSFETs with high-κ gate dielectrics”
IEEE Electron Device Lett. 28, 473 (2007).

[8] S. J. Koester, E. W. Kiewra, Yanning Sun, D. A. Neumayer, J. A. Ott, M. Copel, D. K. Sadana, D. J. Webb, J. Fompeyrine, J.-P. Locquet, C. Marchiori, M. Sousa, and R. Germann
“Evidence of electron and hole inversion in GaAs metal-oxide-semiconductor capacitors with HfO2 gate dielectrics and alpha-Si/SiO2 interlayers”
Appl. Phys. Lett. 89, 042104 (2006).

[9] S. J. Koester, E. W. Kiewra, Yanning Sun, D. A. Neumayer, J. A. Ott, M. Copel,
D. K. Sadana, D. J. Webb, J. Fompeyrine, J.-P. Locquet, C. Marchiori, M. Sousa and R. Germann
“Demonstration of electron and hole inversion inversion in GaAs MOS capacitors with HfO2 gate dielectrics and amorphous Si/SiO2 interlayers”
Appl. Phys. Lett., 89, 042104 1-3 (2006).

[10] J. W. Seo, Ch. Dieker, J.-P. Locquet, G. Mavrou and A. Dimoulas,
“HfO2 high-κ dielectrics grown on Ge(100) with ultrathin passivation layers: A TEM study”
Appl. Phys. Lett., 87, 221906 1-3 (2005).