Defocus-resolved construction of process windows in nanosecond laser irradiation of oxidized silicon

We present a defocus-dependent, quantitatively validated framework for nanosecond fiber-laser irradiation of thermally oxidized silicon. By systematically varying the beam defocus, the on-axis peak power density i and spot diameter d are correlated with distinct surface morphologies on SiO₂ (150 nm)/Si (111). Controlled scanning experiments made with nanosecond fiber laser (IRE-Polyus ILI-1-50, wave length λ = 1062 nm, pulse width τ ≈ 120 ns, Pulse Repetition Frequency 50 kHz, and scan velocity v = 100 mm·s^–1) reveal a continuous morphological sequence — wrinkling, blistering, and premelting — governed by thermo-mechanical stress and interfacial adhesion. Surface features were quantified using two-dimensional Fourier analysis for wrinkle wavelength (λ ≈ 8–10 µm) and automated image segmentation for blister size distributions (1–3 µm). Point-exposure measurements yield a blister-onset energy of 0.09 J, corresponding to a per-pulse fluence of 0.17 J·cm^–2. Logistic regression with 95 % bootstrap confidence intervals with bootstrap replications B = 2000 defines the wrinkle-to-premelting transition, producing a statistically bounded (I, d) phase diagram. Control experiments confirm that both dynamic scanning and the oxide cap are indispensable: point irradiation on SiO₂/Si produces only shallow ⟨110⟩ slip lines from substrate relaxation, while bare Si remains featureless under identical conditions. Hydrofluoric (HF) etching verifies that the observed blisters are true interfacial delaminations. This framework extends classical buckling–delamination mechanics to cyclic nanosecond heating and provides predictive guidelines for precision, sub-melting laser microfabrication of dielectric–semiconductor systems.

1. Otobe T., Gushiken E. Influence of point defects on laser-induced excitation in silicon // Physical Review Applied. 2024. V. 22. N 6. P. 064096. https://doi.org/10.1103/physrevapplied.22.064096

2. Kim W.J., Park K.-R., Ryu S.O., Kim B.S., Kwon J., Kim W.-B. Fundamental origin of Si surface defects caused by laser irradiation and prevention of suboxide formation through high density ultrathin SiO2 // Applied Surface Science. 2024. V. 662. P. 159997. https://doi.org/10.1016/j.apsusc.2024.159997

3. Zhou J.K., Su X.L., Zhang B.K., Zeng Y.H., Liu W., Ye J.C., et al. Ultrafast laser-annealing of hydrogenated amorphous silicon in tunnel oxide passivated contacts for high-efficiency n-type silicon solar cells // Materials Today Energy. 2024. V. 42. P. 101559. https://doi.org/10.1016/j.mtener.2024.101559

4. Bonse J., Höhm S., Kirner S.V., Rosenfeld A., Krüger J. Laser-induced periodic surface structures — a scientific evergreen // IEEE Journal of Selected Topics in Quantum Electronics. 2017. V. 23. N 3. P. 9000615. https://doi.org/10.1109/JSTQE.2016.2614183

5. Namdari N., Mohammadian B., Jafari P., Mohammadi R., Sojoudi H., Ghasemi H., Rizvi R. Advanced functional surfaces through controlled damage and instabilities // Materials Horizons. 2020. V. 7. N. 2. P. 366–396. https://doi.org/10.1039/C9MH01516G

6. Wu Y., Xiang X., Yu J., Yuan X., Shen H., Zheng W., Zu X. Review: Research progress on nanosecond laser irradiation damage of optical films // Nuclear Analysis. 2022. V. 1. N 4. P. 100045. https://doi.org/10.1016/j.nucana.2022.100045

7. Grigoriev F.V., Sulimov V.B., Tikhonravov A.V. Laser-induced thermal stresses in dense and porous Silicon Dioxide films // Coatings. 2021. V. 11. N 4. P. 394. https://doi.org/10.3390/coatings11040394

8. Flores-Johnson E.A., Shen L., Annabattula R.K., Onck P.R., Shen Y.G., Chen Z. The effect of interface adhesion on buckling and cracking of hard thin films // Applied Physics Letters. 2014. V. 105. N 16. P. 161912. https://doi.org/10.1063/1.4900443

9. McDonald J.P., Mistry V.R., Ray K.E., Yalisove S.M., Nees J.A., Moody N.R. Femtosecond-laser-induced delamination and blister formation in thermal oxide films on silicon (100) // Applied Physics Letters. 2006. V. 88. N 15. P. 153121, https://doi.org/10.1063/1.2193777

10. Tsibidis G.D., Stratakis E., Aifantis K.E. Thermoplastic deformation of silicon surfaces induced by ultrashort pulsed lasers in submelting conditions // Journal of Applied Physics. 2012. V. 111. N 5. P. 053502. https://doi.org/10.1063/1.3688020

11. Sopeña P., Wang A., Mouskeftaras A., Grojo D. Transmission laser welding of similar and dissimilar semiconductor materials // Laser and Photonics Reviews. 2022. V. 16. N 11. P. 2200208. https://doi.org/10.1002/lpor.202200208

12. Huang C., Luo Z.A., Zhou H.Y., Yang J.S., Zhang Z.C., Fan M.R., et al. Effect of laser defocus on microstructural and mechanical properties of 316L stainless steel manufactured by laser powder bed fusion // Journal of Materials Research and Technology. 2025. V. 38. P. 3114–3130. https://doi.org/10.1016/j.jmrt.2025.08.099

13. Zhurba D.V., Zhurba V.M., Veiko V.P., Pankin D.V., Zhukov M.V., Puisha A.E. Investigation of phase transformations of carbon steel scale during laser purification by nanosecond pulses in the evaporation mode. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2025, vol. 25, no. 2, pp. 179–189. (in Russian). https://doi.org/10.17586/2226-1494-2025-25-2-179-189

14. Matei A.T., Visan A.I., Negut I. Laser-fabricated micro/ nanostructures: mechanisms, fabrication techniques, and applications // Micromachines. 2025. V. 16. N 5. P. 573. https://doi.org/10.3390/mi16050573

15. Martan J., Cibulka O., Semmar N. Nanosecond pulse laser melting investigation by IR radiometry and reflection-based methods // Applied Surface Science. 2006. V. 253. N 3. P. 1170–1177. https://doi.org/10.1016/j.apsusc.2006.01.077

16. Skvortsov A.M., Huynh Cong Tu, Khaletsky R. Mechanism of microstructuring in the SiO2/Si system under scanning pulsed fiber laser irradiation. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2013, no. 3 (85), pp. 137–143. (in Russian)

17. Otsu N. A threshold selection method from gray-level histograms // IEEE Transactions on Systems, Man, and Cybernetics. 1979. V. 9. N 1. P. 62–66. https://doi.org/10.1109/tsmc.1979.4310076

18. Born M., Wolf E. Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light. Cambridge University Press, 1999. 985 p.

19. Sasaki S., Izumi T., Hara T. Delamination of Si by high dose H-ion implantation through thin SiO2 film (ESR characterization) // Materials Science and Engineering: B. 2002. V. 91-92. P. 160–163. https://doi.org/10.1016/s0921-5107(01)00984-9

20. Song J., Jiang H., Liu Z.J., Khang D.Y., Huang Y., Rogers J.A., et al. Buckling of a stiff thin film on a compliant substrate in large deformation // International Journal of Solids and Structures. 2008. V. 45. N 10. P. 3107–3121. https://doi.org/10.1016/j.ijsolstr.2008.01.023

21. Sakurai H., Konishi K., Tamaru H., Yumoto J., Kuwata-Gonokami M. Direct correlation of local fluence to single-pulse ultrashort laser ablated morphology // Communications Materials. 2021. V. 2. N 1. P. 38. https://doi.org/10.1038/s43246-021-00138-x

22. Velli M.-C., Tsibidis G.D., Mimidis A., Skoulas E., Pantazis Y., Stratakis E. Predictive modeling approaches in laser-based material processing // Journal of Applied Physics. 2020. V. 128. N 18. P. 183102. https://doi.org/10.1063/5.0018235

23. De Baere D., Van Cauwenbergh P., Bayat M., Mohanty S., Thorborg J., Thijs L., et al. Thermo-mechanical modelling of stress relief heat treatments after laser-based powder bed fusion // Additive Manufacturing. 2021. V. 38. P. 101818. https://doi.org/10.1016/j.addma.2020.101818

24. Yu H.-H., Hutchinson J.W. Influence of substrate compliance on buckling delamination of thin films // International Journal of Fracture. 2002. V. 113. N 1. P. 39–55. https://doi.org/10.1023/A:1013790232359

25. Son Y.-I., Shin J. Numerical study on the laser annealing of silicon used in advanced V-NAND device // Materials. 2022. V. 15. N 12. P. 4201. https://doi.org/10.3390/ma15124201

26. Kan Z., Zhu Q., Ren H., Shen M. Femtosecond laser-induced thermal transport in silicon with liquid cooling bath // Materials. 2019. V. 12. N 13. P. 2043. https://doi.org/10.3390/ma12132043