在激光诱导扩散等激光微细加工技术中,需要用聚焦激光束照射基片表面,以形成局部高温区。为使局部高温区的温度分布满足实验要求,对10.6 μm聚焦连续波CO2激光束照射下半导体基片的温度上升进行了数值计算。计算中考虑了基片材料对10.6 μm激光的吸收系数随温度的变化。计算得到了温度上升与基片预热温度、入射激光束功率及曝光面积等参数的关系。结果表明,基片初始温度为室温及激光焦斑直径小于100 μm时,激光照射形成稳定高温区的最高温度不超过600 K。增加基片初始温度,可以在建立满足要求的温度上升的同时,减小基片上高温区分布的面积。在同一初始温度下,在基片高温区分布的面积符合实验要求的前提下,应尽量使用较大的光斑尺寸和激光功率,从而使基片表面热斑的温度分布更易控制。

In laser assisted microprocesing, such as laser induced diffusion, the substrate is irradiated by a focused laser beam. And a high temperature region is formed on the substrate surface. To acquire the desired temperature distribution, the temperature rise in a semiconductor substrate induced by 10.6 μm focused continuous wave (CW) CO2 laser beam has been investigated numerically. The temperature-dependent absorption coefficients of the substrate material are incorporated in the calculation model. The relations between the temperature rise and parameters such as the preheating temperature, the power of the laser beam and the beam width have been obtained. It is shown that when the substrate is in room temperature before the irradiation and the diameter of the focused laser beam is smaller than 100 μm, the highest stable temperature on the substrate can not exceed 600 K. It is also shown that increasing the preheating temperature can reduce the size of high temperature region, when the induced temperature rise is kept to meet the requirement. Under the condition that the temperature distribution meets the experimental requirement, the laser spot size and the power of the incident laser beam should be adopted as large as possible in order to make the control of the temperature distribution easier.