| 摘要 |
<p>PURPOSE:To obviate the generation of a damage in an object to be cleaned and to prevent the generation of unequal cleaning by gradually increasing ultrasonic output, thereby cleaning the object. CONSTITUTION:The object to be cleaned, such as glass substrate for a photomask blank, is cleaned by 5 stages consisting of, for example, a 1st cleaning using an alkali, 2nd and 3rd cleaning using pure water, 4th cleaning using alcohol, and drying using alcohol. The object is immersed into an ultrasonic cleaning cell and the ultrasonic output is linearly increased from zero at the time of the starting of the cleaning. The specified output is maintained after the prescribed time and further, the output is linearly decreased until the output decreases zero at the end of the respective stages. The object is successively cleaned in the respective cells in such a manner. The stepwise increase and decrease of the ultrasonic output and the exponential functional execution thereof are possible as well.</p> |
