"Drilling of crystalline silicon with a laser beam emerged from an as-cut glass optical fiber in wet etchant has been investigated in this report. This method enables deeper drilling than conventional laser drilling methods such as focusing a beam with a lens, because the beam can be delivered to the bottom of the hole by inserting the fiber in the hole. KOH based solution was used for the etchant and H_2O_2 was added to it in order to prevent the etching of the non-irradiated area. A CW Ar laser and a frequency doubled pulsed Nd:YLF laser were compared. Through-hole drilling of the wafer (0.5mm thickness) was investigated using different types of laser source. The average powers of the lasers were 10W. With the Ar ion laser 40 min. irradiation was needed to perforate the wafer and the hole was cone-shaped. On the other hand, with the Nd:YLF laser, through holes were drilled in less than 1 min. of irradiation and the hole had a smoother and sharper wall than with the Ar laser. No damage was observed on the optical fiber. Through holes were also drilled on 3mm-thick wafers."
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