The Interaction and the Surface Crack of Single-Crystal Silicon
Induced by a Millisecond Laser¹

X. Wang*, Y. Qin, Z. W. Li, H. C. Zhang, Z. H. Shen, and X. W. Ni

School of Science, Nanjing University of Science &Technology, Nanjing 210094, China

*e-mail: wangxi.njust@gmail.com

Received March 28, 2012; in final form, May 23, 2012; published online September 3, 2012

Abstract—When the silicon material is irradiated by laser, it absorbs the laser energy leading to the tempera-
ture rise and the thermal stress. The damage effect includes melting, vaporation and thermal stress damage.
Once the thermal stress exceeds the stress strength the crack will initiate. The silicon surface cracks induced by
a millisecond laser are investigated. The experimental results show that three types of cracks are generated
including cleavage crack, radial crack and circumferential crack. The cleavage crack is located within the laser
spot. The radial crack and circumferential crack are located outside the laser spot. A two-dimensional spatial
axisymmetric model of silicon irradiated by a 1064 nm millisecond laser is established. To assess what stresses
generate and explain the generation mechanism of the different cracks, the thermal stress fields during laser irra-
diation and the cooling process are obtained using finite element method. The radial stress and hoop stress
within the laser spot are tensile stress after the laser irradiation. The temperature in the center is the highest but
the thermal stress in the center is not always highest during the laser irradiation. The cleavage cracks are
induced by the tensile stress after the laser irradiation. The radial crack and the circumferential crack are gen-
erated during the laser irradiation.

DOI: 10.1134/S1054660X12100234

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