Interpretation of scanning capacitance microscopy for thin oxides characterization

• Published in: Thin solid films Vol. 517; no. 24; pp. 6721 - 6725
• Main Authors: Ligor, O., Gautier, B., Descamps-Mandine, A., Albertini, D., Baboux, N., Militaru, L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30.10.2009; Elsevier
• Subjects: Applied sciences; Atomic force microscopy; Capacitors; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; Materials science; Metal-oxide interface; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physics; Scanning capacitance microscopy; Silicon oxide; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Silicon oxide; 73.61 Ng; Atomic force microscopy; Metal-oxide interface; Scanning capacitance microscopy; Capacitors; Microscope tips; Electric contacts; Oxide layer; Nanostructures; CV characteristic; Interfaces; Nanometer scale; Silicon oxides; Capacitance; Reliability
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2009.05.026

In this paper, the reliability of the characterization of thin oxides at the nanoscale using Scanning Capacitance Spectroscopy (SCS) is addressed. 5 nm thick thermal silicon dioxide layers are probed by SCS and compared to capacitance versus voltage ( C– V)curves obtained with a classical (“macroscopic”) bench using large (e.g. 100 μm × 100 μm) electrodes. The detrimental influence of the laser used for the measurement of the deflection of the AFM cantilever is pointed out. It is shown that SCS is not able to provide the correct shape of the d C/d V versus voltage curve, compared to macroscopic C– V curves. In particular, a hysteretic behaviour and an increase of the signal in the inversion region are measured by SCS whereas they are not present in macroscopic C– V curves. We show that this can be explained by a bad electrical contact (presence of contaminants and/or charges) between the Atomic Force Microscope's tip and the oxide. Macroscopic C– V curves obtained directly with a large metallic tip positioned on the oxide layer show the same features as SCS, while SCS operated on an electrode cut from an electrode of macroscopic size used for macroscopic C– V curves leads to the correct shape. This shows that SCS won't be fully comparable to macroscopic measurements unless the influence of the contact between the AFM tip and the sample is taken into account.