Evaluation of Three Sample Introduction Systems for Impurity Analysis of an Ultrapure Reagent Using a Scanning Mobility Particle Sizer

Abstract

The semiconductor industry continues to shrink the device sizes while applying more complex shapes and using diverse materials, which requires parallel improvements in the quality of ultrapure reagents. The need for ultrapure reagents has led to ever-higher demands for the performance of analytical instruments used to detect ultratrace impurities. In this study, nonvolatile impurities in ultrapure reagents were quantified using a scanning mobility particle sizer (SMPS). The performances of three different sample introduction systems, i.e., an electrospray (ES), an aerosol generator with a heating chamber and a Nafion desolvation membrane (NB-II), and a MicroMist nebulizer with a heated cyclonic spray chamber and a three-stage Peltier-cooled desolvation system (MM-APEX), were evaluated for the lower limit of detection of a SMPS. The MM-APEX equipped with the SMPS was able to detect NaCl additives at a concentration of 100 parts per trillion (ppt, ng/L) in ultrapure water, which was approximately 10 4 - and 10 2 -fold lower than those of ES and NB-II, respectively. The practical application of MM-APEX with the SMPS for commercial isopropanol samples was also studied. The results clearly demonstrate that the impurity concentrations presented by the NaCl-equivalent concentrations among different sources of isopropanol were at the ppt to parts-to-billion (ppb) scale. The SMPS system equipped with MM-APEX is capable of recognizing impurities with concentrations ranging from tens ppt to thousands of parts per million (ppm), which is beneficial for an ultratrace analysis of nonvolatile impurities in semiconductor process chemicals.

Investigation of Effects of Sulfuric Acid in Single Wafer Cleaning Process Using Isopropyl Alcohol

“…The type of particle is a non-volatile residue (NVR). NVR means consisting of dissolved inorganic materials, particles, and high-boiling-point organics [6]. Total impurity concentration is 9.72 x 10 6 in 0 ppm, 14.83 x 10 6 in 0.05 ppm, 16.41x 10 6 in 0.1 ppm, 20.15x 10 6 in 0.5 ppm, and 55.04x 10 6 in 5 ppm.…”

Application of Hydrosol to Aerosol Based Metrology to Predict Wafer Defects from Process Chemical Contamination

“…The formation of liquid-borne surface contamination can be mimicked by dispersing the liquid into small droplets suspended in air (nebulization) and then evaporating the liquid from the droplets to form particles suspended in the gas (aerosolization). These aerosol particles can then be characterized using well-established methods for size classification and detection [5,6]. To correlate the aerosol particle concentration with the surface particle concentration, the Spin-Drying process can be mimicked using a low-cost wafer coating device and test wafers.…”