面型微加工技術製作金屬微致動器

Abstract

本研究的目的在於發展一種以金屬材料為基礎的表面微加工技術，此技術結合了微影、犧牲層和電鍍製程。並且利用此技術來實現兩種微型致動器，一為長行程之微致動器，另一為垂直梳狀致動器。 長行程微致動器（LSMD）只佔有小巧的尺寸，經由製作與測試後，在很小的輸入電壓下，即可提供很大的位移。此致動器是由平行配置的串連結構所構成，利用電熱方式驅動，且以鎳電鍍製程製作，尺寸約在2000 µm X 300 µm。實驗結果顯示，在3伏特輸入電壓下，最大位移可以達到202µm，相對的功率消耗約為300mW。動態量測顯示此致動器在110-120 Hz的操作頻率之前仍然可以保持它的最大位移，當頻率高至3.8-4k Hz時，則進入了直流操作模式（DC mode）。最後，此致動器在超過2 x 107次以上的操作後，並無發現任何損壞。 至於垂直梳狀致動器，它是藉由兩個相互交錯的梳狀結構以靜電原理驅動，一個固定在基板表面，另一個則由扭臂懸浮著。與傳統的平行電極板致動器相比，垂直梳狀致動器預期可擁有更大的位移。利用論文中所發展之表面微型加工技術製作此種致動器，不需任何的組裝程序。再者，經由電鍍製程，下固定電極與上懸浮電極之間的間距可輕易做出相同的厚度，因此可以避免對不準狀態。然而，於最後蝕刻起始層時，下梳狀電極遭受蝕刻液攻擊，故無法垂直站立於基板上。

Here, a metal-based surface micromachining technology is developed to realize two micro actuators, long-stretch micro drives and vertical comb drives, which includes lithography, sacrificial layer, and electroplating technique. Long-stretch micro drives with compact size are fabricated and tested to provide large displacements at low input voltage. The micro drives are electro-thermally driven, and fabricated through Ni electroplating process. The fabricated LSMDs have connected cascaded structures in parallel arrangement. The typical dimension is about 2000 µm x 300 µm in area. Experimental data show that the maximum displacement can reach about 202 µm at 3 volts, and the corresponding power consumption is 300 mW. The dynamic measurement shows that the LSMD can maintain its maximum displacement until 110-120Hz, and reaches the DC mode with frequency up to 3.8-4k Hz. Finally, the LSMD is proven to operate over 2 x 107 times without damage. The vertical comb drives is electrostatically driven by means of two interdigitated-comb structures, one fixed at the surface of the substrate, the other suspended by torsion beams. It is expected to have larger displacements than that of conventional parallel-plate actuators. Metal-based surface micromachining technology can fabricate VCDs without any assembly process. The gap thickness between upper and lower fingers can be simply made identical by electroplating. Thus the misalignment can be avoided. However, in final removal of seed layer, the lower fingers are attacked by acids, thus cannot stand over the substrate.