Micropatterning of Quartz Substrates by Multi-WavelengthVacuum-Ultraviolet Laser Ablation

Sugioka, Koji; Wada, Satoshi; Tsunemi, Akira; Sakai, Toshiaki; Moriwaki, Hiroki; Nakamura, Akira; Tashiro, Hideo; Toyoda, K.

doi:10.1143/jjap.32.6185

Cited by 34 publications

(9 citation statements)

References 12 publications

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“…There have been studies reporting that the use of synthesized dual-color laser pulse pairs enables highly efficient laser ablation of transparent materials, compared to single-color irradiation [10][11][12][13][14][15][16][17][18][19]. In Ref.…”

Section: Introductionmentioning

confidence: 99%

Enhanced energy deposition and carrier generation in silicon induced by two-color intense femtosecond laser pulses

Tani¹,

Sasaki²,

Shinohara³

et al. 2022

Preprint

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We theoretically investigate the optical energy absorption of crystalline silicon subject to dualcolor femtosecond laser pulses, using the time-dependent density functional theory (TDDFT). We employ the modified Becke-Johnson (mBJ) exchange-correlation potential which reproduces the experimental direct band gap energy Eg. We consider situations where the one color is in the ultraviolet (UV) range above Eg and the other in the infrared (IR) range below it. The energy deposition is examined as a function of mixing ratio η of the two colors with the total pulse energy conserved. Energy transfer from the laser pulse to the electronic system in silicon is dramatically enhanced by simultaneous dual-color irradiation and maximized at η ∼ 0.5. Increased is the number of generated carriers, not the absorbed energy per carrier. The effect is more efficient for lower IR photon energy, or equivalently, larger vector-potential amplitude. As the underlying mechanism is identified the interplay between intraband electron motion in the valence band (before excitation) driven by the IR component and resonant valence-to-conduction interband excitation (carrier injection) induced by the UV component. The former increases excitable electrons which pass through the k points of resonant transitions. The effect of different multiphoton absorption paths or intraband motion of carriers generated in the conduction band play a minor role.

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Section: Introductionmentioning

confidence: 99%

Enhanced energy deposition and carrier generation in silicon induced by two-color intense femtosecond laser pulses

Tani¹,

Sasaki²,

Shinohara³

et al. 2022

Preprint

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show abstract

“…Sugioka et al reported a VUV-UV multiwavelength processing for micromachining silica glass. [37][38][39][40][41][42] They irradiated silica glass with vacuum ultraviolet (VUV) light, which generate transient absorption in ultraviolet region. They used a H 2 Ramman cell and a F 2 laser as VUV light sources.…”

Section: Introductionmentioning

confidence: 99%

Silica nano-ablation using laser plasma soft x-rays

et al. 2009

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We have investigated nano-ablation of silica glass and ablation process using focused laser plasma soft Xrays. Laser plasma soft X-rays were generated by irradiation of a Ta target with Nd:YAG laser light. The soft X-rays were focused on silica glass plates using an ellipsoidal mirror at fluences up to 1 J/cm 2 . In order to fabricate nano-trenches, a silica glass plate was irradiated with laser plasma soft X-rays through the windows of a line and space mask. We demonstrated fabrication of nano-trenches with a width of 50 nm. It should be noted that the feature size is more precise than that estimated from the thermal diffusion length for the 10-ns X-rays (i.e. 80 nm). Furthermore, the ablated area has a depth of 470 nm and a roughness of 1 nm after ten shots of irradiation. Thus, the X-ray irradiation technique have a significant feature of direct nanomachining. The ablation occurs at fluences F beyond a ablation threshould F th and ablation depth per pulse D obeys the law D = 1/α ln(F/F th ), where α is an effective absorption coefficient. These results suggest that absorbed energy is accumulated in the absorbed region without energy diffusion until ablation occurs. In addition, time-resolved mass spectroscopy revealed that silica glass is broken into atomic ions and atomic neutrals during ablation. Because Si + and O + ions have kinetic energies of 10-30 eV, non-thermal process such as Coulomb explosion may be driving force behind the ablation. Such non-thermal process enables us to fabricate nano-structures on silica glass.

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“…We have used the medium for producing strong absorption of the conventional laser beam by the materials, which is referred to as hybrid laser processing. Simultaneous irradiation of the VUV laser beam which possesses extremely small laser fluence induced strong absorption to the UV laser beam by the materials, resulting in the accurate ablation of hard materials such as fused silica, quartz, sapphire, SiC and GaN by the UV laser (VUV-UV multiwavelength excitation process) [3][4][5][6][7][8][9][10][11]. The VUV laser must be, however, still used in this process although this process has some advantages over the single-VUV laser processing due to its small laser fluence.…”

Section: Introductionmentioning

confidence: 99%

LIPAA technique and its possible impact on microelectronics (Invited Paper)

et al. 2005

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The laser-induced plasma-assisted ablation (LIPAA) process developed by our group, in which a single conventional pulsed laser is only used, makes it possible to perform high-quality and high-speed glass microfabrication. Up to the present, this process has been widely applied for micromachining of various transparent hard and soft materials. In this process, a laser beam is first directed to a glass substrate placed in vacuum or air. The laser beam passes through the substrate since the wavelength of the laser beam must have no absorption by the substrate for the LIPAA process. The transmitted laser beam is absorbed by a solid target (typically a metal), located behind the substrate. The target is then ablated, resulting in plasma generation. Due to the interaction of the laser beam and the laser-induced plasma, significant ablation takes place at the rear surface of the substrate. Recently, we have developed the proto-type LIPAA system using a second harmonic of diode pumped Q-switched Nd:YAG laser for the practical use. In this paper, we will demonstrate micromachining, crack-free marking, color marking and dicing of glass materials. Additionally, selective metallization of glass and polyimide by the LIPAA process followed by metal chemical-plating is investigated. The discussion includes mechanism and practical applications in micro-electronics industry of the LIPAA process.

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Micropatterning of Quartz Substrates by Multi-WavelengthVacuum-Ultraviolet Laser Ablation

Cited by 34 publications

References 12 publications

Enhanced energy deposition and carrier generation in silicon induced by two-color intense femtosecond laser pulses

Enhanced energy deposition and carrier generation in silicon induced by two-color intense femtosecond laser pulses

Silica nano-ablation using laser plasma soft x-rays

LIPAA technique and its possible impact on microelectronics (Invited Paper)

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