超音波輔助鑽石線鋸應用於藍寶石加工之研究

Abstract

單晶藍寶石(Sapphire)是一種高透光性、耐高溫且具有高硬度的化合物半導體材料，也因其具備之化學穩定性及高硬度，故目前在LED產業中多以藍寶石作為主要基板材料，而此晶圓基板生產大多以固定磨料線鋸為主要鋸片製程，因線鋸製程為利用鑽石線上之鑽石磨料與工件產生相對運動進而移除材料之製程，故鑽石磨料之使用壽命於線鋸製程中佔非常大的成本，並影響的整個基圓基板生產的品質與價格。 本研究欲藉由超音波振動，使鑽石線材產生強迫式振動，利用使超音波振動下改善其鑽石磨料之磨耗，本篇論文使用實驗室自行開發之超音波導輪，藉由FEM模擬得到超音波導輪之徑向模態，利用耦合(Coupling)特性將其振動能量傳遞至鑽石線材上，使鑽石線材在進行切削時，因超音波振動與工件產生非連續式接觸，經由量測可知線材上具有無衰退並可強迫振動之運動型態優勢，可使切削後之表面因線鋸之振動可獲得均勻且較淺之線痕(Saw mark)，表面粗糙度可降低約44%，並於實際鋸切時觀察發現超音波振動可成功地減少鑽石磨料之磨耗，透過弓角減少的情況下進而使整體的切削力降低，法向切削力可降低約59%，切線切削力可降低約54%，故於超音波振動輔助下可延長線材切削壽命並提高切片表面品質。

Single crystal sapphire is a brittle semiconductor material with high transmittance, temperature resistance, and hardness. Wire sawing is a main slicing process in wafer substrate manufacturing. The process is to remove the material from the workpiece by using diamond abrasive, and it is high-cost due to diamond abrasive’s service life, which may be up to 30% of the total cost of sliced wafer production. In doing so, wire sawing makes a great influence on the quality and price of the entire wafer substrates. The study aims to use ultrasonic vibration on the diamond wire to create forced vibration, and improve the diamond abrasive wear. This research tends to use the ultrasonic wheel developed by the laboratory, and the radial mode of the supersonic ultrasonic wheel obtained by FEM simulation. By means of coupling, the wear transfers its vibration energy to diamond wire. When the diamond wire is in progress, it creates ultrasonic vibration, making discontinuous contact with the workpiece. By measuring the wire, the result shows that the vibration on the wire has the advantages of non-decay and forced vibration, making the surface with uniform and flatter saw marks. Surface roughness can be reduced by 44%. In the experiment, it is observed that ultrasonic vibration can successfully reduce the abrasive wear of diamonds when the bow angle is reduced. And the overall cutting force is reduced. Normal cutting force can be reduced by 59%, tangential cutting force can be reduced by 54%. The measurement of cutting force indicates that the cutting life of wire is extended and the surface quality of the slice is improved by ultrasonic vibration.