High-quality percussion drilling of silicon with a CW fiber laser

Yu, Joe; Webster, Paul J. L.; Leung, Benjamin; Fraser, James M.

doi:10.1117/12.842616

Cited by 5 publications

(2 citation statements)

References 4 publications

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“…With acquisition rates of even a few tens of kilohertz, M-mode images are not only able to directly measure etch rates 13,14 but also melt pool flow 11 and other dynamics of laser drilling processes. 15 Since sensing below the machining front is possible, M-mode data can also be used to guide blind hole cutting in a variety of semitransparent materials including biological tissue 16 even when the exact sample geometry is not known a priori.…”

Section: Introductionmentioning

confidence: 99%

Automatic real-time guidance of laser machining with inline coherent imaging

Webster

Wright

Mortimer

et al. 2011

Journal of Laser Applications

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Optical coherence imaging can measure hole depth in real-time ͑Ͼ20 kHz͒ during laser drilling without being blinded by intense machining light or incoherent plasma emissions. Rapid measurement of etch rate and stochastic melt relaxation makes these images useful for process development and quality control in a variety of materials including metals, semiconductors, and dielectrics. The ability to image through the ablation crater in materials transparent to imaging light allows the guidance of blind hole cutting even with limited a priori knowledge of the sample. Significant improvement in hole depth accuracy with the application of manual feedback from this imaging has been previously demonstrated ͓P. J. L. Webster et al., Opt. Lett. 35, 646 ͑2010͔͒. However, the large quantity of raw data and computing overhead are obstacles for the application of coherent imaging as a truly automatic feedback mechanism. Additionally, the high performance components of coherent imaging systems designed for their traditional application in biological imaging are costly and may be unnecessary for materials processing. In this work, we present a coherent imaging system design that costs less than a fifth of comparable commercial products. We also demonstrate streamlined image processing suited for automated feedback that increases processing speed by two orders of magnitude.

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Section: Introductionmentioning

confidence: 99%

Automatic real-time guidance of laser machining with inline coherent imaging

Webster

Wright

Mortimer

et al. 2011

Journal of Laser Applications

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“…The majority of laser drilling carried out in semiconductor materials uses short pulses [4,5], with ultra-violet [6] lasers being the most widely used. Some longer pulse work has been done Yu et al [7] used 6.6 µs 1070 nm pulses to drill silicon. Longer wavelength lasers have also been used: Li and O'Neill using 1 µm radiation to drill silicon [8]; polycrystalline alumina has previously been laser drilled with ms 1064 nm pulses [9], as well as µs 10.6 µm pulses [10].…”

Section: Introductionmentioning

confidence: 99%

Laser drilling of via micro-holes in single-crystal semiconductor substrates using a 1070nm fibre laser with millisecond pulse widths

2015

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. (2015) Laser drilling of via micro-holes in single-crystal semiconductor substrates using a 1070 nm fibre laser with millisecond pulse widths. Proceedings of SPIE. Industrial Laser Applications Symposium (ILAS 2015), 9657 (965701 A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. ABSTRACTMicro-machining of semiconductors is relevant to fabrication challenges within the semiconductor industry. For via holes for solar cells, laser drilling potentially avoids deep plasma etching which requires sophisticated equipment and corrosive, high purity gases. Other applications include backside loading of cold atoms into atom chips and ion traps for quantum physics research, for which holes through the semiconductor substrate are needed. Laser drilling, exploiting the melt ejection material removal mechanism, is used industrially for drilling hard to machine materials such as superalloys. Lasers of the kind used in this work typically form holes with diameters of 100's of microns and depths of a few millimetres in metals. Laser drilling of semiconductors typically uses short pulses of UV or long wavelength IR to achieve holes as small as 50 microns. A combination of material processes occurs including laser absorption, heating, melting, vaporization with vapour and dust particle ejection and resolidification. An investigation using materials with different fundamental material parameters allows the suitability of any given laser for the processing of semiconductors to be determined. We report results on the characterization of via holes drilled using a 2000 W maximum power 1070 nm fibre laser with 1-20 ms pulses using single crystal silicon, gallium arsenide and sapphire. Holes were characterised in cross-section and plan view. Significantly, relatively long pulses were effective even for wide bandgap substrates which are nominally transparent at 1070 nm. Examination of drilled samples revealed holes had been successfully generated in all materials via melt ejection.

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