Study on Laser-Crystallization Process of Semiconductors

1. 利用递归方法和半无限多层结构中导出的格林函数解，可以对含温度相关导热系数、扩散系数和熔解能的非线性热方程进行数值求解。本文提出了一种求解复杂复合材料的二维边界元法。为了提高拐角处的数值计算精度，尝试了几种方法。提出了一种新的中间节点法，该方法精度高，易于编程和单元划分。用光学显微镜直接观察了聚焦连续氩离子激光束照射下硅薄膜的熔化过程。随着激光束功率的增大，出现固液共存的混合区，然后在混合区中间形成均匀的熔池。结果表明，这种情况受激光束的模式和功率，即激光强度分布的影响很大。TEM00模式适用于结晶质量好的SOI再结晶。利用振镜构建了高速激光直接拉伸系统。该系统能够产生伪线光束。采用梯形波形产生伪线波束效果较好。

1. By using a recursive manner and Green's function solutions derived in a semi-infinite multilayer structure, a nonlinear heat equation including temperature-dependent thermal conductivity and diffusivity and fusion energy for melting has been able to be solved numerically.2. A two-dimensional boundary element method has been developed to solve in a complex composite material. In order to improve the numerical calculation accuracy at a corner, several methods were tried. A newly-developed mid-node method is found to give a good accuracy and an easiness in programming and dividing into elements.3. Thin silicon film during its melting by irradiation of a focused cw argon ion laser beam has been directly observed by using an optical microscope. As the power of laser beam is increased, a mixture region where the solid and liquid coexist appears and then a uniform molten pool is formed in the middle of the mixture region. It is demonstrated that this situation is strongly influenced by the mode and power of laser beam that is, the laser intensity profile. TEM00 mode is suitable to recrystallize SOI of good crystalline quality.4. A high-speed laser direct-drawing system has been constructed by using a galvanometer. This system was able to generate a pseudo-line beam. A trapezoid waveform is found to be good in generating the pseudo-line beam.