具串連結構CMOS-MEMS靜電梳狀致動器之實現

Abstract

本論文提出具有串連結構的CMOS-MEMS靜電梳狀致動器（Cascade electrostatic comb-drive actuator）。由於靜電式梳狀致動器（Electrostatic comb-drive actuator）在致動時會發生側向不穩定（Side-instability）的現象，所以致動器的行距會受此一現象大大限制；本論文所提出一種新型的串連式靜電梳狀致動器，利用此串連結構不僅可以有效的增加靜電梳狀致動器的行距，而且與傳統的靜電梳狀致動器相比，此種串連結構在增加致動行距時，並不需要增加額外的驅動電壓。為了使致動器的各級驅動訊號可以達到良好的電性分離，此種串連式的靜電梳狀致動器必須具有多層結構的特性。因此，元件的製作必須結合標準CMOS製程與CMOS微加工後製程（Post-CMOS micromachining steps），經由此一整合性的製程，致動器會具有多層結構的特性，使各級驅動訊號將可達到良好的分離，並可使致動器具有垂直致動的能力。實驗結果顯示，水平式的串連靜電梳狀致動器（Lateral cascade electrostatic comb-drive actuator）可以增加 200％ 的致動行距，而垂直式的串連靜電梳狀致動器（Vertical cascade electrostatic comb-drive actuator）可以增加 188％ 的致動行距。實驗結果證明，此種串連式結構的設計確實具有非常好的能力能將致動器的致動行距增大。

Electrostatic comb-drive actuators have been developed and employed for many applications. However, side instability (side pull-in) limits the actuator stroke constraining its applications. Hence, extending actuation stroke is an important issue for designing electrostatic comb-drive actuators. In this dissertation, two cascade electrostatic comb-drive actuators, namely cascade lateral electrostatic comb-drive actuator and cascade vertical electrostatic comb-drive actuator are developed for improving the stroke of electrostatic comb-drive actuators. With the cascade configuration, the actuation stroke can be improved greatly. To implement the cascade electrostatic comb-drive actuators, the Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 μm two polysilicon layers and four metal layers (2p4m) complementary metal-oxide-semiconductor (CMOS) and post-CMOS micromachining steps are employed to fabricate the device. Due to the multilayer characteristic of the microstructure, the electric signal isolation and vertical motion can be achieved. Experimental results indicated that the stroke of the lateral and vertical cascade electrostatic comb-drive actuators can be improved 200% and 188% respectively without adding extra driving voltage. These results demonstrated that the proposed cascade configurations have the capability to improve the actuation stroke of electrostatic actuators.