| 摘要: | CNC 加工機在現今工業中已是不可或缺的重要設備。然而，隨著高頻、高功率與微型化元件製作需求的提升，傳統 CNC 加工機所存在的微小誤差，常導致工件良率與性能無法達到預期目標。當 CNC 搭配雷射加工系統使用時，其工作平台的位置誤差更會直接限制加工精度。
藍寶石晶圓是 μ‑LED 長晶的關鍵基板，亦廣泛應用於高功率光電元件、高頻收發器及極端環境感測器。隨著應用向高頻、高功率及微型化持續推進，藍寶石晶圓的高精度加工需求日益迫切。然而，由於藍寶石具高硬脆特性，傳統接觸式機械微加工法已面臨瓶頸，雷射加工結合高精度平台控制遂成為重要發展趨勢。
本研究針對本實驗室既有超快雷射系統搭配的六軸（Stewart）平台，提出一套適用於六軸平台的誤差補償與迭代優化方法，以突破微加工精度的限制。方法上，透過在電流環注入多個電流脈衝以補償平台在速度為零處的定位誤差，並利用迭代程式自動計算最佳電流補償值。三種不同平台移動路徑的實驗證明此補償策略具備有效性與強健性，能使平台快速脫離死區、加速至參考速度並平滑轉入穩態區，且無需額外硬體即可應用於既有加工系統。
以六軸平台實際位置為評估變數，實驗結果顯示，本方法可將雷射晶圓切割路徑的最大位置誤差降低 70% 以上，並可在不同加工參數下維持路徑誤差小於 2.5 μm。為驗證其對實際加工品質的提升效果，本研究在厚度 160 μm 的藍寶石晶圓上進行啞鈴形（dumbbell‑shape）微鑽孔試驗。該形狀不同於一般微鑽孔，需要針對不同角度的傾斜面進行補償。本研究利用所開發的迭代程式進行傾斜角補償，使最大位置誤差從 9.5 μm 降至 2 μm 以下。
實際加工結果顯示，補償後可有效消除因位置誤差造成的雷射熱影響區，顯著提升孔壁品質。最後，經由硫酸與磷酸混合蝕刻液去除孔壁內殘渣與再鑄層後，本研究首次在藍寶石晶圓上成功製作出無微裂紋、深寬比 2:1的啞鈴形通孔。此成果證明，本研究提出的誤差補償方法能大幅提升六軸平台搭配雷射微加工的精度與品質，並具備廣泛的應用潛力。
;Computer numerical control (CNC) machine tools have become indispensable in modern manufacturing. However, with the growing demand for high-frequency, high-power, and min-iaturized devices, even minor positioning errors in conventional CNC systems can significantly compromise product yield and performance. When integrated with laser processing systems, the motion stage’s positioning accuracy becomes a critical limiting factor for overall machining pre-cision.
Sapphire wafers serve as the key substrates for μ‑LED epitaxy and are widely used in high‑power optoelectronic devices, high‑frequency transceivers, and extreme‑environment sen-sors. As these applications advance toward higher frequencies, higher power densities, and smaller form factors, the need for high‑precision sapphire micromachining has become increas-ingly urgent. Due to the hard‑brittle nature of sapphire, conventional contact‑based microm-achining methods have reached their performance limits, making laser processing combined with high‑precision stage control the preferred development path.
This study addresses the positioning accuracy bottleneck of an existing ultrafast laser sys-tem equipped with a six‑axis Stewart platform by developing a dedicated error compensation and iterative optimization method. The proposed approach injects multiple current pulses into the servo current loop to compensate for zero‑velocity positioning errors, while an automated iterative algorithm determines the optimal current compensation values. Experimental verifica-tion on three distinct motion trajectories demonstrates the effectiveness and robustness of the method. It enables rapid dead‑zone departure, smooth acceleration to the reference velocity, and seamless steady‑state transition—all without requiring additional hardware modifications, thus making it directly applicable to existing micromachining systems.
Using the actual stage position as the evaluation metric, experimental results show that the proposed method reduces the maximum trajectory error during laser wafer cutting by over 70%, maintaining the cutting path error within 2.5 μm under various machining conditions. To vali-date its impact on practical fabrication, a dumbbell‑shaped micro‑drilling test was conducted on 160 μm‑thick sapphire wafers. Unlike conventional micro‑holes achievable with a three‑axis stage or galvanometer scanner, this geometry required compensation for multiple tilted surfaces at varying angles. The developed iterative algorithm reduced the maximum trajectory error from 9.5 μm down to below 2 μm.
The fabricated features showed that the compensated process effectively eliminated la-ser‑induced heat‑affected zones caused by positioning errors, significantly improving hole‑wall quality. Finally, after removing redeposition and recast layers using a mixed sulfuric‑phosphoric acid etchant, this study successfully demonstrated—for the first time—the fabrication of mi-cro‑crack‑free dumbbell‑shaped through‑holes in sapphire wafers with an aspect ratio of 2:1. These results confirm that the proposed error compensation strategy substantially enhances the precision and quality of ultrafast laser micromachining using six‑axis stages, offering broad po-tential for advanced microfabrication applications. |
