AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM2-TuM

Paper EM2-TuM7
Combined Electrical and Morphological Characterization of Al@sub 2@O@sub 3@ Films by Non-Contact AFM

Tuesday, November 1, 2005, 10:20 am, Room 312

Session: High-k Dielectric Characterization
Presenter: J.M. Sturm, University of Twente, The Netherlands
Authors: J.M. Sturm, University of Twente, The Netherlands
A.I. Zinine, University of Twente, The Netherlands
H. Wormeester, University of Twente, The Netherlands
R.G. Bankras, University of Twente, The Netherlands
J. Holleman, University of Twente, The Netherlands
J. Schmitz, University of Twente, The Netherlands
B. Poelsema, University of Twente, The Netherlands
Correspondent: Click to Email
High-K Al@sub 2@O@sub 3@ films deposited on Si(001) by Atomic Layer Deposition (ALD) were investigated with non-contact AFM in ultra-high vacuum. Oxide charges in the film appear in the AFM images through the attractive interaction between the charge and its image charge in the conducting tip. The image contrast of the charge was found to depend on the tip-sample bias voltage. A spherical tip model based on the oxide charge, its image in the tip and the image of the tip in the substrate allows a quantitative description of the influence of the bias voltage. Most charges in the oxide film were identified as negative with a homogeneous depth distribution. Lateral variations of the Contact Potential Difference (CPD) and differential capacitance were recorded during acquisition of the topographic image with the aid of bias modulation and lock-in detection of the electrostatic force gradient at the first and second harmonic. CPD fluctuations with a typical magnitude of 20 to 50 mV on a lateral scale of ~50 nm were found. The lateral resolution of the CPD is limited with respect to the topography. This is attributed to charge screening with a length scale set by the effective Debye length. Al@sub 2@O@sub 3@ deposition on hydrogen-terminated Si (Si-H) resulted in a strong negative correlation between the differential capacitance and the surface topography (i.e. a large height correlates to low capacitance). For deposition on thermal SiO@sub 2@, this correlation was significantly reduced, whereas almost no correlation was observed for a SiO@sub 2@ film. The high correlation for deposition on Si-H is attributed to thickness variations due to substrate-inhibited ALD growth.