DISSOLVED NITROGEN CONCENTRATION MONITORING METHOD AND SUBSTRATE CLEANING METHOD

摘要

There is provided a dissolved nitrogen concentration monitoring method that enables real-time accurate monitoring of the dissolved nitrogen concentration of a cleaning liquid without complicated operations as well as cost reduction. A dissolved oxygen concentration DO2 during ultrasonic wave irradiation is measured by a dissolved oxygen concentration meter 43. An increase amount of dissolved oxygen concentration ?DO2 is calculated by subtracting an initial dissolved oxygen concentration D0 from the measured dissolved oxygen concentration DO2. Subsequently, an approximation equation corresponding to a specific overflow rate or ultrasonic output power level is read out from a storage section 46, and the approximation equation read out from the storage section 46 is used to calculate a dissolved nitrogen concentration DN2 of mixed ultrapure water from the increase amount of dissolved oxygen concentration ?DO2.