Nanosecond laser silicon micromachining

Abstract

We present theoretical calculations and experimental measurements of silicon micromachining rates, efficiency of laser pulse utilization, and morphology changes under UV nanosecond pulses with intensities ranging from 0.5 GW/cm 2 to 150 GW/cm 2 . Three distinct irradiance regimes are identified based on laser intensity. At low intensity, proper gas dynamics and ablation vapor plume kinetics are taken into account in our theoretical modeling. At medium high intensity, we incorporate the proper plasma dynamics, and predict the effects of the laser generated vapor plasma and the electron hole plasma on the laser-matter interaction. At even higher intensity, we attribute the observed increased ablation rate to energy re-radiation from the laser heated hot plasma, the strong shock wave, and the accompanied strong shock wave heating effects. Experimentally measured data in these regimes agree well with our calculations, without changing parameters in the calculations used for the three regimes. Our results can be applied toward quantitatively characterize the behavior of ablation results under different laser parameters to achieve optimal results for micromachining of slots and vias on silicon wafers.

Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review

“…In zone 3, ablation rate dramatically increases with the increase of laser fluence and may get saturated, while the processing quality degrades significantly and the dimensions of the ablation generated defects is less controllable. Ren et al 152 found that for UV nanosecond laser pulses with intensities ranging from 0.5-150 GW/cm 2 , at low ablation intensity, silicon removal is characterized by surface evaporation and the ablation morphology is clean. At medium ablation intensity, the increment of ablation rate with laser intensity slows down and saturates due to a strong plasma shielding effect and the quality of laser ablation is degraded.…”

Surface morphology created by nanosecond laser annealing of amorphised Si layer—Investigations by complementary methods

“…Many types of surface structures develop spontaneously on silicon surfaces after repeated nanosecond laser irradiation pulses. A different morphology is observed at the bottom of the craters formed by a few high-power pulses (Craciun et al, 2002;Ren et al, 2004). Sharp conical microstructures separated by 20-30 mm are created on silicon surfaces with nanosecond laser irradiation generated in multi-pulsed regime (Crouch et al, 2004).…”

Microprocesos láser para la mejora de dispositivos fotovoltaicos basados en silicio cristalino

“…Por lo tanto se decidió fijar la frecuencia de repetición, que por motivos de estabilidad de los equipos fueron 20 kHz, para el caso de radiación UV y VIS, y de 4 kHz para el caso de radiación IR. A modo de recapitulación se representan Los datos obtenidos de fluencias umbrales son un poco menores que los obtenidos en c-Si puro por otros autores [Ren04,kamakis06,Tao09,Colina08A]. Poder comparar resultados es difícil dado el carácter exclusivo de nuestra muestra y el hecho de que la elección del área que define la fluencia puede no ser única.…”