自19世紀末期居禮兄弟發現單晶石英具壓電效應以來，石英因其優異的物理穩定性、化學惰性與高Q值特性，被廣泛應用於頻率控制與震盪元件。現今多以高壓水熱法於高壓釜中利用種子晶體生長出高純度之合成石英(Synthetic Quartz)，並採用具優良頻率及溫度特性的AT-cut取向作為震盪基板。隨著電子元件朝高頻、高速與微型化方向發展，石英震盪器結構設計亦趨於精密化，其中微鑽孔技術成為實現微米級導通孔與腔體結構製作的關鍵步驟，使上下電極層可導通並形成特定的聲學共振路徑，以提升震盪器的電性能與尺寸整合度。然而，石英屬於典型的硬脆材料，傳統接觸式機械鑽孔於微尺度加工時易產生裂縫、崩邊與孔壁損傷，進而影響元件之可靠度與頻率穩定性。為克服此問題並滿足高精度與高良率的製程需求，非接觸式超快雷射微鑽孔技術逐漸成為主流，其利用超短脈衝時間有效抑制熱影響區(Heat Affected Zone， HAZ)，可在維持孔壁品質的同時實現高效率與高精準度的加工，成為推動石英震盪器微型化與高性能化的重要技術途徑。 本研究採用波長為515 nm之飛秒振鏡雷射加工系統，搭配20 wt.%氫氧化鉀(KOH)水溶液作為輔助介質，針對單晶石英晶圓進行背向微鑽孔特性之研究。研究目的在於改善傳統以去離子水輔助雷射加工時孔壁表面品質不佳、孔內雷射燒蝕(Ablation)產物再沉積以及熱影響區擴散等問題。KOH水溶液可在加工過程中協助移除熔融或再凝固的石英碎屑，並藉由其對石英表面的化學蝕刻協同作用促進孔壁平整化，進而提升孔壁品質與減少表面附著物。實驗結果顯示，相較於以去離子水輔助鑽孔，KOH水溶液輔助加工，可有效減少雷射燒蝕產物的再沉積、降低孔壁表面粗糙度。同時，該製程能省去以去離子水輔助鑽孔後所需之6小時的35 wt.% KOH水溶液蝕刻，大幅簡化整體製程步驟並提升製程效率。;Since the discovery of the piezoelectric effect in single-crystal quartz by the Curie brothers in the late 19th century， quartz has been widely used in frequency control and oscillator components due to its excellent physical stability， chemical inertness， and high Q-factor. Today， high-purity synthetic quartz is primarily grown using seed crystals in autoclaves via the hydrothermal method， and the AT-cut orientation， known for its excellent frequency and temperature characteristics， is frequently adopted for oscillator substrates. As electronic components continually evolve towards high frequency， high speed， and miniaturization， the structural design of quartz oscillators has become increasingly precise. Among these advancements， micro-drilling technology has emerged as a crucial step for fabricating micrometer-scale through-holes and cavity structures， enabling the electrical connection between upper and lower electrode layers and the formation of specific acoustic resonance paths to enhance the electrical performance and dimensional integration of the oscillators. However， quartz is a typical hard and brittle material. Traditional contact-based mechanical drilling is prone to inducing micro-cracks， edge chipping， and hole-wall damage during micro-scale processing， which subsequently compromises the reliability and frequency stability of the components. To overcome these issues and meet the manufacturing demands for high precision and high yield， non-contact ultrafast laser micro-drilling technology has gradually become the mainstream. By utilizing ultrashort pulse durations to effectively suppress the heat-affected zone (HAZ)， this technology enables highly efficient and precise processing while maintaining excellent hole-wall quality， serving as an important technical approach to drive the miniaturization and high performance of quartz oscillators. This study employs a 515 nm femtosecond galvanometer laser processing system， assisted by a 20 wt.% potassium hydroxide (KOH) aqueous solution as the auxiliary medium， to investigate the characteristics of backside micro-drilling on single-crystal quartz wafers. The objective is to address the issues associated with traditional deionized water-assisted laser processing， such as poor hole-wall surface quality， the redeposition of laser ablation products within the hole， and the expansion of the heat-affected zone. The KOH aqueous solution facilitates the removal of molten or resolidified quartz debris during the process and， through its synergistic chemical etching effect on the quartz surface， promotes hole-wall planarization， thereby improving hole-wall quality and reducing surface adhesions. Experimental results indicate that， compared to DI water-assisted drilling， KOH aqueous solution-assisted processing effectively reduces the redeposition of laser ablation debris and lowers the surface roughness of the hole wall. Concurrently， this process eliminates the need for the subsequent 6-hour wet etching using a 35 wt.% KOH aqueous solution， which is typically required after DI water-assisted drilling， thereby drastically simplifying the overall manufacturing workflow and enhancing process efficiency.
