Particle control challenges in process chemicals and ultra-pure water for sub-10nm technology nodes

Particle contamination in ultra-pure water (UPW) and chemicals will eventually end up on the surface of a wafer and may result in killer defects. To improve the semiconductor processing yield in sub-10 nm half pitch nodes, it is necessary to control particle defectivity. In a systematic study of all major techniques for particle detection, counting, and sizing in solutions, we have shown that there is a gap in the required particle metrology which needs to be addressed by the industry. To reduce particles in solutions and improve filter retention for sub-10 nm particles with very low densities (<10 particles/mL), liquid particle counters that are able to detect small particles at low densities are required. Non-volatile residues in chemicals and UPW can result in nanoparticles. Measuring absolute non-volatile residues in UPW with concentrations in the ppb range is a challenge. However, by using energy-dispersive spectroscopy (EDS) analysis through transmission electron microscopy (TEM) of non-volatile residues we found silica both in dissolved and colloidal particle form which is present in one of the cleanest UPW that we tested. A particle capture/release technique was developed at SEMATECH which is able to collect particles from UPW and release them in a controlled manner. Using this system we showed sub-10 nm particles are present in UPW. In addition to colloidal silica, agglomerated carbon containing particles were also found in UPW.