Measurement of the Mechanical Stability of Semiconductor Line Structures in Relevant Media

Abstract

Enhanced particle removal processes in wet cleaning of semiconductor wafers can cause significant lateral forces on surface structures. These forces have to be limited to below the stability of the (nano) structures on the surface to prevent damage. A mechanical fracture test based on atomic force microscope manipulation was used in liquid media (deionized water, isopropanol, and propylene carbonate) to measure the lateral stability of polysilicon line structures. The results are compared to previously reported results in air. All liquid media investigated here showed a stabilizing effect. Maximum stability was found for immersion in isopropanol. The size of the damage generated was mainly influenced by the viscosity of the liquids. The results do not support a stress corrosion cracking process.

Collapse Mechanisms for High Aspect Ratio Structures with Application to Clean Processing

“…The AFM induced damage method generates a very uniform damage in the shape of a round rupture line as shown in Figure 3 (4,5). Also, its size is constant with a length of the broken piece L (Figure 3) of around 550 nm in air with a point loading.…”

“…The lateral signal is recorded during this process and converted subsequently into the corresponding force value by using a calibration technique (9,10). For more detailed information about the AFM induced collapse method the reader is referred to our previous publications (4,5) and similar techniques in the literature (6,7,8). The structures of interest are polysilicon line structures, which resemble gate stacks.…”

“…In this paper, mechanical fracture tests were performed with an atomic force microscope (AFM) on polysilicon line structures to gain experimental data about its mechanical stability (similiar to 4,5,6,7,8). The lateral forces on three different line widths and the corresponding damages have been studied and compared to simulations of a lateral load on a beam.…”

Measurement of the mechanical stability of semiconductor line structures in drying liquids with application to pattern collapse

“…The viscosity dependence indicates in the first place hydrodynamic drag forces. However, no dependence on the speed of the AFM tip was found [20].…”

“…A significant variation in collapse force was observed when using IPA instead of water [20]. The collapse force increased by a factor of 1.4 compared to the force in pure DI water (figure 4).…”