Imaging breakdown spots in SiO/sub 2/ films and MOS devices with a conductive atomic force microscope

Abstract

Conductive atomic force microscopy (C-AFM) was used to study the dielectric breakdown of SiO 2 layers at a nanometric scale. First, bare oxide regions were stressed and broken down using the tip as the metal electrode of a MOS structure. The results show that the initial breakdown is electrically propagated to neighbor regions, affecting their dielectric strength. Moreover, the area affected by the initial breakdown depends on the breakdown hardness. In particular, it is shown that this area is smaller when the current through the structure is limited during the experiments. The effect of the current limitation is analyzed in detail. Based on the results, a qualitative picture of the breakdown process is presented, which accounts for this effect. Finally, for the first time, the breakdown spots in standard MOS devices (with poly-Si gate) are electrically imaged with C-AFM. The areas of the observed spots are in agreement with those obtained on bare oxides.Index Terms-Atomic force microscopy, current limitation, dielectric breakdown, MOS structure, SiO 2 films.

HfO2high-ksolid-state incandescent devices: performance improvement using a Ti-embedded layer and observation of conductive paths as light-emitting sources

“…Moreover, although there are larger regions of shallow pits around the deep pit, breakdown is thought to be an extremely local phenomenon [22]. The formation of shallow pits is probably due to the electrical propagation to neighboring areas [23]. Our light-emission photo, SEM and CAFM results clearly demonstrate that the bright dots shown in figures 3(b) to (e) and the black pits shown in figure 4 are similar, and both are conductive paths in HfO 2 films.…”

Observation of Localized Breakdown Spots in Thin SiO[sub 2] Films Using Scanning Capacitance Microscopy

“…This implies that using SCM to image OBD spots is a more stable and reliable method as compared to the use of conductive-AFM. [10][11][12] Finally, as seen in Fig. 4a, the sizes of the spots are different.…”

Influence of vacuum environment on conductive atomic force microscopy measurements of advanced metal-oxide-semiconductor gate dielectrics

“…14 Figure 3 shows the consecutive current images obtained during −5 V scans measured in vacuum on the same region of a high-k sample annealed at 1000°C. To do so, consecutive current maps ͑substrate injection͒ on the same area have been registered to study the electrical degradation of the layer due to the electrical stress ͑induced by the high-field scan͒.…”