Abstract: First of all, a semiconductor substrate is provided. Then a photoresist layer is formed on the semiconductor substrate, and the photoresist layer is defined to form a pre-region. Afterward, an ion-implanting process is performed by using the photoresist layer as an ion-implanting mask to form an ion-implanting region in the semiconductor substrate of the pre-region. Because the surface of the photoresist layer is bombarded with ions, a hard mask is formed on the photoresist layer. Subsequently, an etching process with fluorine-based plasma is performed to strip the hard mask. An ashing process with the temperature about, but more than 250° C. is performed by way of an oxide plasma process to remove the photoresist layer. Finally, a soak process with a sulfuric acid and a cleaning process with the RAC are performed to remove the remainder of the photoresist layer.