Using an ultrashort pulse laser, photon energy of which is smaller than the band gap energy of silicon, machining of substances located at back of a silicon plate should be achievable. To realize this possibility, machining of a silicon substrate as well as machining of gold film on it was carried out using femtosecond laser pulses, wavelength of which lay between 1.5 to 2.5 μm. It is demonstrated that the rare surface of the silicon substrate and the gold film placed at the back of the silicon substrate can be machined with no detectable change on its front surface. Frequency adjustment of crystal oscillator sealed in a silicon package is tried and up-conversion of the frequency is achieved by removing small amount of thin gold film on the crystal with irradiation of 1.5 μm laser pulses through the silicon lid.

Date Published: 17 February 2010
PDF: 9 pages
Proc. SPIE 7584, Laser Applications in Microelectronic and Optoelectronic Manufacturing XV, 75840M (17 February 2010); doi: 10.1117/12.845475

Published in SPIE Proceedings Vol. 7584:
Laser Applications in Microelectronic and Optoelectronic Manufacturing XV
Hiroyuki Niino; Michel Meunier; Bo Gu; Guido Hennig; Jan J. Dubowski, Editor(s)