We have measured pressures p and temperatures T corresponding to the maximum nucleation rate of argon in a cryogenic supersonic nozzle apparatus where the estimated nucleation rates are J=10(17+/-1) cm(-3) s(-1). As T increases from 34 to 53 K, p increases from 0.47 to 8 kPa. Under these conditions, classical nucleation theory predicts nucleation rates of 11-13 orders of magnitude lower than the observed rates while mean field kinetic nucleation theory predicts the observed rates within 1 order of magnitude. The current data set appears consistent with the measurements of Iland et al. [J. Chem. Phys. 127, 154506 (2007)] in the cryogenic nucleation pulse chamber. Combining the two data sets suggests that classical nucleation theory fails because it overestimates both the critical cluster size and the excess internal energy of the critical clusters.

We follow the freezing of heavy water (D2O) nanodroplets formed in a supersonic nozzle apparatus using position resolved pressure trace measurements, Fourier transform infrared spectroscopy, and small-angle X-ray scattering. For these 3-9 nm radii droplets, freezing starts between 223 and 225 K, at volume based ice nucleation rates Jice,V on the order of 10(23) cm(-3) s(-1) or surface based ice nucleation rates Jice,S on the order of 10(16) cm(-2) s(-1). The temperatures corresponding to the onset of D2O ice nucleation are higher than those reported for H2O by Manka et al. [Manka, A.; Pathak, H.; Tanimura, S.; Wölk, J.; Strey, R.; Wyslouzil, B. E. Phys. Chem. Chem. Phys.2012, 14, 4505]. Although the values of Jice,S scale somewhat better with droplet size than values of Jice,V, the data are not accurate enough to state that nucleation is surface initiated. Finally, using current estimates of the thermophysical properties of D2O and the theoretical framework presented by Murray et al. [Murray, B. J.; Broadley, S. L.; Wilson, T. W.; Bull, S. J.; Wills, R. H.; Christenson, H. K.; Murray, E. J. Phys. Chem. Chem. Phys.2010, 12, 10380], we find that the theoretical ice nucleation rates are within 3 orders of magnitude of the measured rates over an ∼15 K temperature range.

We follow the vapor-liquid phase transition of N(2) in a cryogenic supersonic nozzle apparatus using static pressure measurements. Under our operating conditions, condensation always occurs well below the triple point. Mean field kinetic nucleation theory (MKNT) does a better job of predicting the conditions corresponding to the estimated maximum nucleation rates, J(max) = 10(17±1) cm(-3) s(-1), than two variants of classical nucleation theory. Combining the current results with the nucleation pulse chamber measurements of Iland et al. [J. Chem. Phys. 130, 114508-1 (2009)], we use nucleation theorems to estimate the critical cluster properties. Both the theories overestimate the size of the critical cluster, but MKNT does a good job of estimating the excess internal energy of the clusters.

We follow the nucleation of n-alcohols, n-propanol through n-pentanol, in two sets of supersonic nozzles having differing linear expansion rates. Combining the data from static pressure trace measurements with small-angle X-ray scattering we report the experimental nucleation rates and critical cluster sizes. For n-propanol, position resolved measurements clearly confirm that coagulation of the 2-10 nm size (radius) droplets occurs on the time scale of the experiment but that the effect of coagulation on the results is minimal. Under the conditions of the current experiments, our results suggest that alcohols have critical clusters that range from the dimer (n-pentanol) to the hexamer (n-propanol). We then compare the experimental results with classical nucleation theory (CNT), the Girshick-Chiu variant of CNT (GC), and the mean field kinetic nucleation theory (MKNT). Both CNT and MKNT underestimate the nucleation rates by up to 5 and 7 orders of magnitude, respectively, while GC theory predicts rates within 2 orders of magnitude. Correspondingly, the critical cluster size for all alcohols is overpredicted by factors of 2-9 with agreement improving with increasing chain length. An interesting byproduct of our experiments is that we find that the coagulation rate is enhanced by a factor of 3 over the value one would calculate for the free molecule regime.

Metallic contamination is a major challenge in multiple semiconductor processes, including photolithography and wet etch and cleans (WEC). Though there are several contributors to metallic contamination, significant efforts have focused on improving the incoming quality of process chemicals, especially commodity chemicals. Another key contributor to on-wafer metallic contamination is water (H2O), which is used to dilute most aqueous chemicals. Single Particle Inductively Coupled Plasma Mass Spectroscopy (SP-ICP-MS), a technique relying on time-based resolution of pulses generated during a standard ICP-MS analysis, is used to aid the understanding of metal particle contamination in water and process chemicals.In this paper, we studied water and 30% Hydrogen Peroxide (H2O2), two of the most widely used chemicals across all WEC processes. We used a high purity grade of 30% H2O2, further diluted to a typical use concentration (5% by volume) using two grades of Deionized Water (unfiltered and filtered) where the concentration of metallic particles was the key variable. The metals studied included Iron (Fe), Chromium (Cr), Zinc (Zn), Titanium (Ti), Nickel (Ni) and Aluminum (Al), representing some of the most commonly observed metallic contaminants in H2O2 and water. After analyzing the distribution of contaminants in the chemicals, filters were introduced into the system to observe the impact of filtration on metal removal. The importance of filtration on the overall quality of the diluted process chemical was demonstrated by using a Polysulfone (PS) membrane to filter the lower grade Deionized Water (DIW).