Precision drilling of fused silica with 157-nm excimer laser radiation

Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian; Meyer, K.

doi:10.1117/12.479557

Cited by 3 publications

(2 citation statements)

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“…Despite these advantages, the associated cost, complexity and comparably low throughput have resulted in limited commercial success. [13][14][15] CO 2 lasers, operating in the mid-IR with wavelengths in the 9.3 to 10.6 µm range, have direct absorption through excitation of vibrational modes within the material. Glass drilling with CO 2 lasers benefits from the combination of high power, reasonable cost and linear absorption in glass.…”

Section: Laser-based Methods For Forming Tgvsmentioning

confidence: 99%

Rapid and high throughput formation of through glass vias

Schrauben,

Matsumoto,

Lin

et al. 2024

Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXIX

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Interest in glass for integrated circuit (IC) packaging and interposer applications has accelerated in recent years, due to its favorable mechanical and electrical properties compared to current advanced materials. This report describes our recent results on through glass via (TGV) drilling, utilizing a novel process employing a single laser source with an engineered pulse duration, pulse repetition frequency, and average power to rapidly form TGVs in 50 and 100 µm thick glass. The process forms TGVs with a ∼10 µm diameter with zero taper, smooth sidewalls and minimal splash; the dimensions of these TGVs meet the requirements for next-generation interposers to replace through silicon vias. Unlike Bessel beam based processes, this process is compatible with high bandwidth beam steering technologies (galvanometers and acousto-optic deflectors (AODs)), enabling an industrially viable throughput in high-density drill patterns of more than 10000 vias per second. The formation dynamics of the TGVs are elucidated using multiphase simulations and in-situ spectroscopic methods. Stress mitigation in the fully-formed TGVs is explored through annealing studies; an alternate approach utilizes heating of the glass substrate during the laser processing to minimize stress formation during the drilling process. Both methods are shown to mitigate embedded stress and avoid cracking.

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Section: Laser-based Methods For Forming Tgvsmentioning

confidence: 99%

Rapid and high throughput formation of through glass vias

Schrauben,

Matsumoto,

Lin

et al. 2024

Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXIX

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“…In order to efficiently couple energy into glass substrates, the laser wavelengths need to be either in the deep UV range to span the bandgap of the material, or in the mid-infrared range to excite vibrational modes in the material. Many demonstrations of TGV formation have been carried out in the deep UV with excimer lasers 2,3 and in the mid-IR with CO 2 lasers. [4][5][6] Laser wavelengths at which the glass substrate is transparent require a high intensity to induce multiphoton absorption, which is usually achieved, when using a single laser source, through short pulse duration.…”

Section: Introductionmentioning

confidence: 99%

Analysis and mitigation of stress induced by rapid formation of through glass vias in thin substrates

Matsumoto¹,

Lin

Schrauben

et al. 2023

Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXVIII

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As communication networks move toward higher frequency bands, thin glass substrates are advancing toward industrial production in packaging and interconnect applications as high-frequency, low-loss materials. While current techniques for the formation of through glass vias (TGVs) allow for efficient drilling of <40 μm diameter holes, there are currently limited commercially viable options for smaller TGVs. Presented herein is a unique approach to forming high aspect ratio TGVs in 10-20 μs for 50 and 100 μm thick glass. This is accomplished by using a high-power quasi-continuous wave (QCW) laser with a simple Gaussian beam profile focusing scheme. Crucially, this approach is compatible with high bandwidth beam steering technologies, i.e., the combination of galvanometers and acousto-optic deflectors (AODs), allowing for simple scaling to industrially viable throughputs of tens of thousands of vias per second for high-density drill patterns. The TGVs have straight, smooth sidewalls, and high uniformity. Birefringence image microscopy is used to further assess the finer quality aspects of the TGVs formed; considerable residual stress embedded around the TGVs was found after laser drilling, which could cause cracking in subsequent process steps. It is demonstrated that the stress can be significantly reduced by either annealing the glass substrate after drilling or drilling at elevated temperatures to mitigate the embedded stress.

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