Frank Holsteyns

Experimental and theoretical evidence for vacancy-clustering-induced large voids in Czochralski-grown germanium crystals

Optical inspection of polished Czochralski-grown Ge wafers typically reveals the presence of surface pits similar to the Crystal Originated Particles (COP’s) observed in silicon but in a wider variety of sizes and shapes. Computer simulation of vacancyclustering during the Cz germaniumcrystal growth suggests that the surface pits originate from large voids formed by the diffusion-limited clustering of an excess of vacancies.

In-situ ATR-FTIR for dynamic analysis of superhydrophobic breakdown on nanostructured silicon surfaces

Superhydrophobic surfaces are highly promising for self-cleaning, anti-fouling and anti-corrosion applications. However, accurate assessment of the lifetime and sustainability of super-hydrophobic materials is hindered by the lack of large area characterization of superhydrophobic breakdown. In this work, attenuated total reflectance−Fourier transform infrared spectroscopy (ATR-FTIR) is explored for a dynamic study of wetting transitions on immersed superhydrophobic arrays of silicon nanopillars. Spontaneous breakdown of the superhydrophobic state is triggered by in-situ modulation of the liquid surface tension. The high surface sensitivity of ATR-FTIR allows for accurate detection of local liquid infiltration. Experimentally determined wetting transition criteria show significant deviations from predictions by classical wetting models. Breakdown kinetics is found to slow down dramatically when the liquid surface tension approaches the transition criterion, which clearly underlines the importance of more accurate wetting analysis on large-area surfaces. Precise actuation of the superhydrophobic breakdown process is demonstrated for the first time through careful modulation of the liquid surface tension around the transition criterion. The developed ATR-FTIR method can be a promising technique to study wetting transitions and associated dynamics on various types of superhydrophobic surfaces.

A detailed study of semiconductor wafer drying

Publisher Summary In this chapter, the performance of several drying techniques commonly used in the semiconductor manufacturing industry is evaluated. This is done by measuring the residues on a wafer onto which a solution containing metal salts acting as tracer elements has been dispensed and dried. To correctly interpret the experimental data, the results are compared with predictions from a theoretical model. This model assumes two distinct mechanisms for deposition: adsorption and evaporative deposition. The first mechanism is a result of attractive interactions between the contaminant and the wafer surface, while the second mechanism is due to liquid evaporation during drying. For the latter case, the evaporated film thickness is introduced as a figure of merit for the drying process under study. In the tests, tests, spin drying was compared with two types of Marangoni based drying: on a vertically moving wafer and on a horizontally rotating wafer. The results show that for spin drying two consecutive phases occur: during the first seconds of spinning convective removal of liquid is the dominant mechanism, followed by a phase where evaporation takes over. This behavior is confirmed by models reported in the literature describing photo-resist coating. The amount of liquid evaporating during spin drying is inversely proportional to the square root of the rotation speed. This suggests that entrainment of liquid by the gas flow over the wafer surface is the dominant mechanism for evaporation. This finding is in agreement with fluid dynamics models describing the flow of gas entrained with a rotating substrate.

Chapter 19 – A Detailed Study of Semiconductor Wafer Drying

In this chapter, the performance of several drying techniques commonly used in the semiconductor manufacturing industry is evaluated. This is done by measuring the residues on a wafer onto which a solution containing metal salts acting as tracer elements has been dispensed and dried. To correctly interpret the experimental data, the results are compared with predictions from a theoretical model. This model assumes two distinct mechanisms for deposition: adsorption and evaporative deposition. The first mechanism is a result of attractive interactions between the contaminant and the wafer surface, while the second mechanism is due to liquid evaporation during drying. For the latter case, the evaporated film thickness is introduced as a figure of merit for the drying process under study. In the tests, spin drying was compared with two types of Marangoni based drying: on a vertically moving wafer and on a horizontally rotating wafer. The results show that for spin drying two consecutive phases occur: during the first seconds of spinning convective removal of liquid is the dominant mechanism, followed by a phase where evaporation takes over. This behavior is confirmed by models reported in the literature describing photo-resist coating. The amount of liquid evaporating during spin drying is inversely proportional to the square root of the rotation speed. This suggests that entrainment of liquid by the gas flow over the wafer surface is the dominant mechanism for evaporation. This finding is in agreement with fluid dynamics models describing the flow of gas entrained with a rotating substrate.