Technology for room temperature photoresist stripping has been established by using a neutral, environmentally friendly cleaning solution. The newly developed. cleaning solution is a mixture of ultrapure water and isopropyl alcohol (IPA) with a small amount of alkali metal halide salt injected. The new cleaning technology combines this mixture and megasonic cleaning at a frequency of millions of hertz. A 33 x 33 mm sample chip with a thermal oxide film 3000 Angstrom thick was entirely coated with positive-type photoresist. This sample chip went through postbaking at 130 degrees C, and was cleaned at megasonic frequencies with an IPA/potassium fluoride (KF) process, completely stripping the photoresist in 70 s. This process does not dissolve photoresist but physically strips photoresist off at its interface with the substrate, which is an ideal way of stripping photoresist. Hexamethyldisilazane (HMDS) has been used in a vapor treatment to form a trimethyl silyl group on a substrate, which has improved adhesion between photoresist and substrate. The HMDS is replaced with a 1,3 divinyltetramethyldisilazane (DVTMDS) treatment to form a vinyl dimethyl silyl group with a higher molecular weight than a trimethyl silyl group, which enhances photoresist stripping efficiency. Moreover IPA/KF solution does not deteriorate, as IPA and KF do not react with each other. This means IPA/KF solution can be reused by removing stripped photoresist by filtration.