Fiber lasers trump DPSS for thin-wafer slicing
In 2008, Mobius Photonics (Mountain View, CA) introduced UV laser sources based on the harmonic-wavelength conversion of the output of a seeded optical fiber amplifier (technology obtained by entering into an exclusive licensing agreement with Harvard University). Today, Mobius has publicly announced that its UV laser sources are performing better than diode-pumped solid-state (DPSS) lasers for thin-wafer dicing, as well as for other material and microelectronics processing applications, including thin-film solar-cell scribing and for use as the depletion beam in stimulated-emission-depletion (STED) microscopy studies.
Today, 50 µm thick wafers diced with DPSS UV lasers produce dies with significantly lower break strength compared to conventional mechanical methods. But Mobius' all-fiber-amplifier, master-oscillator-power-amplifier architecture nanosecond UV source technology, thanks to its multiple wavelengths and variable pulse-repetition frequencies (200 kHz to 20 MHz) and pulsewidths, produces dies with strength comparable to mechanical methods. For 50 µm thick wafers, the Mobius laser produces dies with average die-strength values of 657 MPa, compared to 367 MPa for DPSS Q-switched UV lasers. Mobius fiber lasers also produce smooth, continuous scribe lines in glass substrates (without chipping) and generate 1 µm diameter uniform through-holes in 25 µm thick polyimide. For wafer-dicing applications, actual die-strength data and a minimum/maximum value can be disclosed under a nondisclosure agreement. Contact Kiyomi Monro at [email protected].
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