在本研究中使用奈秒脈衝雷射結合聚焦鏡對單晶的n-type 4H-SiC進行雷射鑽孔，目的為實現10 μm以下並且深寬比大於10的孔徑。使用聚焦鏡的原因為達到更小的光斑尺寸，小的光斑尺寸不僅能讓雷射能量密度更大使雷射能量更集中，也更容易達到較小的孔徑。奈秒雷射在目前工業界已經行之有年，和皮秒以及飛秒雷射相比之下，飛秒和皮秒雷射可以大大的減少熱影響區以及提高材料的加工精度，但相對其設備的維護和保養成本也比較高，若能使用奈秒雷射達到高精度的鑽孔效果，可以大幅的降低成本。本研究透過參數優化的方式降低頻率、增加脈充數(鑽孔時間)以及峰值功率，最後以0.03 mJ的脈衝能量，頻率2 kHz，脈衝寬度30 ns，鑽孔時間2 s鑽出深度小於10 μm深寬比大約13的孔，並且使用氬氣輔助鑽孔降低了孔中的氧含量至9 %。
另外本研究使用光譜儀在雷射鑽孔時進行監測，發現大部分為矽的發射譜峰，因此決定以矽離子來做Saha Boltzmann plot，將偵測到的譜峰對比了NIST LIBS Database以及Atomic spectra database來確定那些發射譜峰屬於矽離子的哪種型態，以及那些矽離子對應的相關參數Aki(1/s)、Ek(ev)、g。最終在0.14 mJ頻率2 kHz脈衝寬度30 ns情況下偵測到的等離子體溫度約170000 K，這歸因於雷射的極小光斑以及短脈衝低頻率，和文獻比較本研究的峰值功率密度和能量密度都高出許多，並且在訊號光譜中發現了Si III的離子，這顯少出現在文獻LIBS實驗中，說明本研究的溫度確實能達到170000 K。
本研究也發現在使用相同脈衝能量下提高頻率的過程中，發現等離子體的溫度也會逐漸下降，在脈衝寬度30和50 ns中，頻率在大約9和3 kHZ開始下降，這歸因於過高的頻率會導致下一發脈衝會被上一發脈衝產生的等離子體或熔融微粒及蒸汽屏蔽導致能量消散無法有效傳入至孔洞內部。而相同頻率脈衝能量下降低脈衝寬度提高峰值功率會使溫度提高，但在提升功率使不同脈寬達到相同峰值功率時，只有30和50 ns的溫度接近，120和200 ns的還是低了許多，這說明這兩個脈衝寬度的最佳頻率遠低於2 kHz。

In this study, nanosecond pulsed laser drilling combined with a focusing objective was applied to single crystal n type 4H-SiC to fabricate holes with diameters below 10 µm and aspect ratios greater than 10. The focusing lens produced a smaller spot size, increasing laser fluence and facilitating smaller apertures. Picosecond and femtosecond lasers can lessen the heat affected zone and improve machining precision, but their equipment and maintenance costs are relatively high; demonstrating high precision drilling with a nanosecond laser therefore offers a cost effective alternative. By lowering the repetition rate, extending the drilling time, and increasing the peak power could achieved holes less than 10µm deep with an aspect ratio of about 13 using a pulse energy of 0.03 mJ, a repetition rate of 2 kHz, a pulse width of 30 ns, and a drilling duration of 2 s. Argon assist further reduced the oxygen content inside the holes to 9 %.
Spectroscopic monitoring during drilling showed that most emission lines originated from silicon, so a Saha Boltzmann plot based on silicon ions was constructed. High resolution spectrometers collected spectra in two calibrated wavelength bands, which were matched to the NIST LIBS Database and the Atomic Spectra Database to identify ionic species and their parameters Aki, Ek, and g. With a pulse energy of 0.14 mJ, a repetition rate of 2 kHz, and a pulse width of 30 ns, the plasma temperature reached about 170000 K. This very high temperature is attributed to the extremely small spot and high peak fluence, and is supported by the appearance of Si III lines, rarely reported in LIBS experiments.
Raising the repetition rate at constant pulse energy caused a gradual decrease in plasma temperature. For pulse widths of 30 ns and 5 ns, the temperature began to drop at roughly 9 kHz and 3 kHz, respectively, due to plasma, molten droplets, and vapor from earlier pulses shielding later pulses and dissipating energy before it reached the hole interior. Reducing the pulse width at a fixed repetition rate increased the temperature by raising the peak power, but equalizing the peak power across different pulse widths yielded similar temperatures only for 30 ns and 50 ns; temperatures for 120 ns and 200 ns remained much lower, indicating that their optimal repetition rates are well below 2 kHz.

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