Abstract: A method of stripping a nitride layer from a wafer includes the steps of putting the wafer into a process bath containing a stripping solution, passing the stripping solution from the process bath through a filter to remove the nitride particles contained therein, heating the filtered stripping solution through an in-line electrical heater with two heating parts connected in parallel to allow the stripping solution to quickly return to the proper etching temperature, and returning the temperature recovered stripping solution to the process bath. The filtered stripping solution is branched through the parallel heating parts to enable it to be quickly heated. The stripping solution may be a phosphoric acid solution, whose proper etching temperature is about 163.degree. C. The in-line heater consists of at least two heating parts connected in parallel, each with an electrical capacity of 6 KW.