Spatially resolved electrical measurements of SiO2 gate oxides using atomic force microscopy

Abstract

Using a modified atomic force microscope (AFM) with a conducting cantilever, we have investigated the dielectric strength of SiO2 gate oxide films. This has been achieved by spatially resolving the prebreakdown tunneling current flowing between the silicon substrate and tip. During AFM imaging a voltage ramp was applied to the tip at each image point so as to determine the local threshold voltage required to generate a small tunneling current in the oxide, without causing an irreversible electrical breakdown. For an oxide 12-nm thick this voltage was found to vary by more than a factor of 2.7 over an area of 0.14 μm2, with a maximum value of 40.5 V. This suggests that the breakdown strength of conventional metal-oxide-silicon capacitors may not be limited by the intrinsic dielectric strength of the oxide, but by imperfections or nonuniformities in the Si/SiO2 structure. By preventing irreversible oxide breakdown during scanning, we can image the dielectric properties of oxide films with a lateral resolution better than 20 nm.

Microscopic investigations of switching phenomenon in memristive systems: a mini review

“…Using this technique, information about a sample's surface topography and electrical response of its lms can be gathered simultaneously. [18][19][20] Because of the complexity of RS process, three types of methods in CAFM have been adopted by scientic community, to investigate the RS phenomenon and each of them have some pros and cons.…”

Scanning Thermal Microscopy (SThM)

“…• Electrostatic force microscopy (EFM), enabling the recording of the surface charge or potential variations based on changes in the forces acting on the tip (Terris, Stern, Rugar, & Mamin, 1989;Girard, 2001); • Kelvin probe force microscopy (KPFM), enabling the tracking of the surface potential, maintaining a constant distance between the tip and the surface (Nonnenmacher, O'Boyle, & Wickramasinghe, 1991;Bhushan & Goldade, 2000;Moczała, Sosa, Topol, & Gotszalk, 2014) • Conductive(Àprobe) atomic force microscopy (C-AFM), in which the current flowing through the tip is recorded while the surface is scanned in static (contact) mode (Murrell et al, 1993;Wielgoszewski, Gotszalk, Woszczyna, Zawierucha, & Zschech, 2008;Gajewski et al, 2015) • Piezoresponse force microscopy (PFM), in which the tip acts as an electrode to excite deformation of a piezoelectric sample (G€ uthner & Dransfeld, 1992;Huey et al, 2004) • Scanning capacitance microscopy (SCM), which enables the recording of variations in tip-surface capacitance (Abraham, Williams, Slinkman, & Wickramasinghe, 1991;Lányi, 2008) • Scanning spreading resistance microscopy (SSRM), similar to C-AFM but usually with a higher current range, enabling investigations of doping levels in semiconductors (De Wolf, Snauwaert, Clarysse, Vandervorst, & Hellemans, 1995), among other uses • Magnetic force microscopy (MFM), which uses a microprobe with a tip made of magnetic material (Sáenz et al, 1987). • SThM, which adds the capability of imaging thermal properties of the sample This list cannot be considered complete: there are a large variety of specialized scanning-based AFM modes, including those involving more than one cantilever being used at once (Sulzbach & Rangelow, 2010;Ivanova et al, 2008).…”

Effect of Silane Coupling Agent Chemistry on Electrical Breakdown Across Hybrid Organic–Inorganic Insulating Films

“…[11][12] As smaller insulator volumes are probed, fewer defects are encountered, which tends to increase the breakdown strength towards an ultimate intrinsic limit. 13 C-AFM was originally used in the 1990's as a technique to investigate electrical breakdown of nanoscale materials, [14][15] with significant effort concentrated on evaluating the breakdown of silica and hafnia inorganic insulating layers for transistor gate applications. [16][17][18][19][20][21] More recently, C-AFM breakdown measurements have been performed on nanoscale organic insulator systems.…”