AVS 60th International Symposium and Exhibition
    Electronic Materials and Processing Monday Sessions
       Session EM+TF-MoM

Paper EM+TF-MoM6
Monitoring the HfO2-InAs Interface during the ALD Process using Ambient Pressure X-ray Photoemission Spectroscopy

Monday, October 28, 2013, 10:00 am, Room 101 B

Session: High-k Gate Oxides for High Mobility Semiconductors I
Presenter: R. Timm, Lund University, Sweden
Authors: R. Timm, Lund University, Sweden
S. Yngman, Lund University, Sweden
A. Head, Lund University, Sweden
J. Knutsson, Lund University, Sweden
M. Hjort, Lund University, Sweden
J. Knudsen, Lund University, Sweden
J. Schnadt, Lund University, Sweden
L.-E. Wernersson, Lund University, Sweden
A. Mikkelsen, Lund University, Sweden
Correspondent: Click to Email
MOS structures based on III-V semiconductors with high-k oxide layers formed by atomic layer deposition (ALD) are highly promising. In order to achieve superior device performance, a precise control and profound knowledge of the semiconductor-oxide interface is crucial, but not fully reached yet. One of the great challenges is to characterize the chemical reactions taking place at the interface between the III-V semiconductor, its native oxide, and the high-k dielectric material during the ALD process. X-ray photoemission spectroscopy (XPS) has successfully been used to investigate this interface before and after individual steps of the ALD reaction [1,2], but was until now limited to ultrahigh vacuum conditions.

Here we present ambient pressure XPS studies of the atomic layer deposition of HfO2 on InAs: By performing subsequent half-cycle steps of the ALD process within the reaction cell of an ambient pressure XPS system, we were able to monitor the slowed down ALD reaction by XPS and thus obtain fully in-situ and real-time XPS measurements of the high-k deposition on III-V semiconductors for the first time. The experiments were performed at the HP-XPS endstation of synchrotron beamline I511 at the MAX IV Laboratory [3]. Tetrakis(dimethylamino)hafnium (TDMA-Hf) and water were used as precursors, deposited at pressures between 10-3 and 10-2 mbar.

After an activation time of up to several minutes, a complete reduction of the As-oxides within about 20 s could be seen in the real-time As 3d spectra during exposure to TDMA-Hf. Hf 4f spectra show a significant amount of hafnium to be present on the surface only when the As-oxide reduction sets in, indicating that the reaction occurs immediately as soon as hafnium precursors are adsorbed on the surface. During the second half-cycle, surface hydroxylation occurs within about a minute as seen in O 1s spectra during water exposure. N 1s and C 1s spectra taken under vacuum conditions between subsequent ALD half-cycles change reversibly between different N- and C-based components. If the substrate temperature is reduced from 220°C to 160°C, an incomplete As-oxide reduction together with significant adsorption of non-reacting hafnium precursor material on the surface is observed. We will discuss the dependence of the chemical reactions on further ALD conditions and the relevance of such ambient pressure XPS studies for an improved understanding and control of the semiconductor-oxide interface.

[1] Hinkle et al., Curr. Opin. Solid St. M. 15, 188 (2011)

[2] Timm et al., Appl. Phys. Lett. 97, 132904 (2010)

[3] Schnadt et al., J. Synchrotron Radiat. 19, 701 (2012)