本研究以分子動力學觀察奈米金屬薄膜經雷射加工時，雷射與材料間互相作用後，對薄膜產生燒蝕及原子冷卻後的排列情形等的物理機制，所探討的製程參數是針對雷射參數，其中包含雷射能量及脈衝時間寬度。在模擬中是以脈衝時間寬度為 2 ps 及 500 fs、波長為 248 nm的脈衝雷射探討在不同的雷射能量下對金屬薄膜的刻除率，以及材料在雷射燒蝕後產生熱衝擊波以及應力波的動態過程、暫態的表面溫度，並且觀察暫態原子的相變化過程。由雷射加工模擬的結果可知，雷射能量低時只會造成材料的熱膨脹及震盪並無刻除的現象，而雷射能量較高時即會有刻除的現象且雷射能量越高材料的刻除率會愈高，且材料結構產生應力集中導致破裂現象；而在熱衝擊波及應力波傳播的振幅和速度會隨著時間增加而降低，並傳播到材料內部，且當應波傳播接近固體狀態時其傳播速度比銅的聲速稍大。最後我們提出分子動力學方法的瓶頸及改進方法，作為今後努力的目標。

This study is focused on the investigation of the physical mechanisms about the excimer laser ablation of copper thin film using molecular dynamics. After laser material interacting, the physical mechanisms of ablating thin film and arrangement of cooling atoms, the process parameters in the simulation are aimed at laser parameters, including laser energy and pulse duration. The pulse duration is 2 picosecond and 500 femtosecond, and wavelength is 248 nanometer in the parameters of pulse laser in simulation. We discuss the ablation rate of metal thin film in differential laser energy, and after ablating, the material produces the dynamic process of thermal shock wave and stress wave and transient surface temperature and an observation of transient phase change process of atoms after laser heating. From the simulated results about the laser ablation, the material produces thermal expansion and vibration when laser energy lower, ablating phenomenon produce when laser energy higher and the ablation rate increases when the laser energy rises and the structure of material produce concentration of stress to procure phenomenon of crack. The velocity of wave and amplitude decrease with the time rise. The velocity of the stress wave in two difference laser pulses both were larger than the sound velocity in Cu. Finally, the bottlenecks of the molecular dynamics simulation will be carried out, and the state-of-the-art ways overcoming these bottlenecks are also shown to be our future works.

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