微機械微波開關之製程研究

Abstract

本研究利用面型微加工技術將一垂直靜電驅動之微波開關製作於矽晶圓基板上。以電鑄鎳薄膜的技術製作懸浮金屬桿與金屬平板，以電子槍蒸鍍系統沈積金薄膜作為下電極與導線層，上下電極間的絕緣層則採用氮化矽薄膜。經由對不同犧牲層材質的實驗測試，發現以銅當犧牲層搭配電鑄鎳薄膜為結構是較佳的組合，並可成功製作微機械開關結構。 本研究製作了兩種不同的微機械開關結構，分別是懸臂樑平板、懸臂樑平板搭配扭轉橫樑，其驅動電壓分別是2.3 ~ 7.6V和16.5 ~ 20.5V。當採用shunt的連結方式時，利用靜電力將此開關致動器作上與下的驅動，則可對微波訊號作ON與OFF的切換。此微機械微波開關的插入損失(insertion loss)為-3.0 ~ -4.0dB (2~20GHz)。當兩個微機械微波開關同時在一CPW上為OFF狀態時，量測到的隔絕(isolation)低於-45dB(0.1~20GHz)。

A surface micromachined microwave switch has been made on silicon substrate, which is vertically actuated by electrostatic mechanism. The suspended arm and plate are constructed by electroplated nickel layer, the gold film patterned by lift-off method forms the lower electrode and signal line, and the Si3N4 is deposited as dielectric layer. Different sacrificial layer materials are tested, and the use of Cu as sacrificial layer and Ni as structure layer performs the successful fabrication process. Two different configurations of microwave switch, cantilever plate and cantilever plate with torsion beam, are designed and fabricated, which have actuation voltage 2.3 ~ 7.6V and 16.5 ~ 20.5V, respectively. By the shunt-mounted, a microwave signal is switched ON and OFF when the suspended signal switching plate is actuated up and down. The insertion loss of -3.0 ~ -4.0dB from 2GHz to 20GHz is obtained. The isolation below -45dB between 0.1GHz and 20GHz for two switches mounted on one CPW is measured.