Measuring Particles and Bubbles in Process Chemicals at Controlled Temperatures

Microbubbles in semiconductor manufacturing process chemicals can be produced by mechanical disturbance to the chemicals or by changing the temperature and pressure. Bubbles suspended in liquid are easily miscounted as particles when an optical particle counter is used for measuring particles. A new technique, controlling sample temperature, has been developed. Samples for measuring particles are refrigerated to a temperature that eliminates bubbles and then introduced into a particle counter for measurement. The results from these experiments indicate that sample temperature strongly affects the particle counts due to the bubbles in the liquids. Effective temperatures for bubble suppression in several process chemicals have been selected based on the experiments. To better understand bubble suppression by controlling temperature, theoretical simulations for the microbubbles in the chemicals were conducted at various temperature conditions. The results from the experiments and the theoretical simulations are compared.