飛秒雷射導致氫化非晶矽的相變，脫附，再結晶及剝蝕現象: 與矽晶片之對照研究

Femtosecond-Laser-Induced Phase Change, Desorption, Recrystallization and Ablation of Hydrogenated Amorphous Silicon: a Comparative Study with Bulk Silicon

高士軒(Shih-Hsuan Kao)

指導教授 ： 潘犀靈 ； 李明昌

國立清華大學/電機資訊學院/光電工程研究所/碩士(2021年)

摘要

本論文中我們利用鈦藍寶石超快雷射對氫化非晶矽以及矽晶片進行一連串的單發雷射加工研究。由於超短脈衝雷射導致材料的非線性吸收效應，使得氫化非晶矽在不同照射光通量閥值下發生相變，脫附，再結晶，剝蝕等現象。我們也利用泵-探顯微術進行氫化非晶矽剝蝕過程中的時空動態演化研究，初步結果顯示其表面熔化過程發生在5.4 ps以內。在剝蝕的研究當中，氫化非晶矽在受到雷射能量密度為56.2 mJ/cm^2的照射下，可以將其中的氫去除，進而使得材料變為純的非晶矽，且當雷射能量密度來到91.7 mJ/cm^2，即會發生剝蝕現象，表層材料被雷射挖掘。而對於矽晶圓我們進行對照的研究，當雷射能量密度由低到高，我們首先可以看到激光誘導週期表面結構的現象，而後剝蝕現象發生。根據剝蝕造成的蝕坑深度與能量密度作圖，可以看出三個斜率表示三種不同的態。當雷射能量密度達6.31×10^2 mJ/cm^2時，可以看到剝蝕現象的發生，此時的斜率與光學穿透深度相關。而後當雷射能量密度達1.66×10^3 mJ/cm^2，此時的斜率主要受到電子熱傳導影響。最後當雷射能量密度達3.35×10^3 mJ/cm^2，此時為流體動力運動狀態，矽會熔化成液態。

關鍵字

超快雷射 ； 飛秒雷射 ； 雷射剝蝕 ； 材料相變 ； 氫化非晶矽 ； 矽晶片

並列摘要

In this thesis, we studied single-shot femtosecond laser processing of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon wafers. Due to the nonlinear absorption effect of the material caused by the ultrashort pulses, hydrogenated amorphous silicon undergoes phase change, desorption, recrystallization, and ablation under different laser fluences. We also use pump-probe microscopy to study the temporal and spatial dynamic evolution of the hydrogenated amorphous silicon ablation process. We determined that the surface melting process is within 5.4 ps. In the study of laser ablation of a-Si:H, hydrogen desorption was observed when the fluence reaches 56.2 mJ/cm^2, then the material becomes pure amorphous silicon. When the laser fluence reaches 91.7 mJ/cm^2, ablation will occur, surface material will be excavated by the laser. For bulk silicon, the figure of ablated crater depths as a function of fluence exhibits three slopes, representing three different regimes. When the fluence reaches 6.31×10^2 mJ/cm^2, the phenomenon of ablation can be seen, and the slope is related to the optical penetration depth. When the fluence reaches 1.66×10^3 mJ/cm^2, the slope is mainly affected by the thermal conduction of electrons. Finally, when the fluence reaches 3.35×10^3 mJ/cm^2, it is in a state of hydrodynamic motion, and silicon will melt into a liquid state.

並列關鍵字

Ultrafast laser ； Femtosecond laser ； Laser ablation ； Material phase change ； Hydrogenated amorphous silicon ； Bulk silicon

參考文獻

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