Laser treatment of silicon at nitrogen ambient: Thermal stress analysis

Abstract

Laser control melting of silicon surface is carried out at nitrogen gas environment and temperature rise as well as thermal stress developed in the irradiated region is simulated using the finite element method. The residual stress developed in the surface region after the laser treatment is measured using the XRD technique and the measurement results are compared with the predictions. The fracture toughness of the laser treated surface is also measured using the indentation tests. The structural and morphological changes in the laser irradiated region are examined using the scanning electron microscope. It is found that b phase silicon nitride was formed in the surface region of the laser treated workpiece. The temperature gradient close to the laser beam spot attains significantly high values due to the high heating and cooling rates. This, in turn, results in high stress levels in this region during the laser treatment process. The laser treated surface was free from the defects including microcracks, voids and cavitations.

Characteristics of laser textured silicon surface and effect of mud adhesion on hydrophobicity

“…The frequency of the laser pulses was 1500 Hz, which resulted in 72% overlapping ratio of the irradiated spots at the workpiece surface. The laser treatment tests were repeated several times by incorporating different laser parameters; in which case, laser parameters resulting in the minimum surface defects, such as very small cavities and no crack Page 6 of 33 A c c e p t e d M a n u s c r i p t 6 networks, are selected in the light of the previous study [9]. Increasing laser power at the workpiece by 10%, while keeping the laser scanning speed same as selected, caused cavity formation at the surface, which in turned increase the surface roughness considerably.…”

“…Although laser texturing of silicon surface was studied previously [9], the main emphases was to examine the surface morphology and microstructure. The surface characteristics including hydrophobicity and laser treated surface exposed to a mud, which is formed from the dust due to vapor condensation, were left for the future study.…”

“…One of the effective techniques to produce silicon nitride at silicon wafer surface is to use a high temperature gas-assisted nitriding process. Since the laser beam can be used effectively to generate a high temperature environment at the surface, gas assisted processing together with a laser beam heating can produce nitride species at the irradiated surface [9]. The combination of control evaporation and melting results in textures consisting of micro/nano poles at the laser treated surface while further improving surface hydrophobicity [10].…”

3D-MID Technology for Surface Modification of Polymer-Based Composites: A Comprehensive Review

“…In addition, the surface layer properties of polymeric materials also related to the laser ablation. Basically, the laser ablation is based on physicochemical changes induced by the laser radiation and resulted in tearing off fragments of the irradiated surface layer in the ablation process [ 227 , 228 , 229 , 230 , 231 ]. In the laser ablation of polymeric materials, there are two main process, photochemical and photothermal that may proceed simultaneously.…”

A predictive thermal dynamic model for parameter generation in the laser assisted direct write process

“…In the former case, 4 node linear tetrahedrons are usually used as elements to generate a 3D mesh, with finer size around the laser processed region, growing into coarser elements away from the process region [176][177][178][179][180][181][182][183]. The latter situation is usually more complicated.…”