| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for removing a porous region for stably preventing occurrence of missing of SOI layer even when the SOI layer is thin, maintaining high quality, and also maintaining productivity without increase in the etching time. SOLUTION: The method for removing porous region comprises the steps of enlarging interior of porous pores with the etching process by allowing an etchant 203 to penetrate into the pores while the ultrasonic wave is guided to the etchant 203 in a first intensity of the ultrasonic wave, and removing porous region remaining in a base material through destruction thereof while the ultrasonic wave is guided to the etchant 203 in a second intensity of the ultrasonic wave. In above steps, the second intensity of ultrasonic wave is set lower than the first intensity of the ultrasonic wave. COPYRIGHT: (C)2007,JPO&INPIT
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