Modeling of CW laser diode irradiation of amorphous silicon films

Thermal damages on the surface of a silicon wafer induced by a near-infrared laser

“…The temperature-dependent physical and optical properties of the silicon, including density, thermal conductivity, heat capacity, thermal expansion coefficient, Young's modulus, Poisson's ratio, absorption coefficient and reflectivity, are given in Table 2. 12,17,24 A time-dependent solver was used, and the solid-liquid phase change in the silicon was considered in terms of the specific heat capacity. 20 The calculation duration time was 20 s in 0.01 s intervals, and the initial temperature of the silicon wafer was 20°C.…”

“…In the simulation, the thermal stress and temperature variations induced by the NIR CW laser were calculated based on the heat transfer and thermoelasticity model. [19][20][21] The cracking damage was predicted by comparing the calculated thermal stress with the fracture strength of silicon, and the melting damage was predicted by comparing the calculated temperature with the melting point of silicon.…”

Study of a-Si crystallization dependence on power and irradiation time using a CW green laser

“…The specific heat of a-Si, C p (T), is replaced by (C p (T) + δL m ) in the heat transfer equation, where L m is the latent heat of melting and δ is a Gaussian function given in Table I. The additional term δL m takes into account the phase change effect within the temperature range of this study [16]. Analogous treatment is made in case of liquid-vapor phase change at the corresponding temperature T v .…”

“…Depending on the time duration of the phase-change process several models are used [6,9,10,15,16].Although some experimentally identified mechanisms are represented well in computational modelling, even advanced models cannot describe all experimental data. In this study a simple thermal model is presented.…”

“…However, the traditionally used excimer laser crystallization (ELC) has some disadvantages, mainly the narrow process window of laser energy density and the maximum crystallization depth achievable with this method. In recent works other lasers have been studied, like pulsed Nd:YAG lasers (1064 nm, 532 nm and 355 nm) [9][10], CW green laser [11][12][13][14][15], and CW diode lasers (808 nm) [16][17]. Laser silicon crystallization using these wavelengths and pulse times allows a large variety of grains structure depending on the laser power and the scanning speed, leading to a very wide processing window [18], in opposite to the conventional excimer laser crystallization (ELC) process where the super lateral growth (SLG) regime is very difficult to determine [5].…”