Stability Study of an Electrothermally-Actuated MEMS Mirror with Al/SiO₂ Bimorphs

• Main Authors: Peng Wang, YaBing Liu, Donglin Wang, Huan Liu, Weiguo Liu, HuiKai Xie
• Format: Article
• Language: English
• Published: MDPI AG 2019-10-01
• Series: Micromachines
• Subjects: electrothermal actuation; electrothermal mems mirror; electrothermal bimorph; stability; temporal drift
• Online Access: https://www.mdpi.com/2072-666X/10/10/693

Electrothermal actuation is one of the main actuation mechanisms and has been employed to make scanning microelectromechanical systems (MEMS) mirrors with large scan range, high fill factor, and low driving voltage, but there exist long-term drifting issues in electrothermal bimorph actuators whose causes are not well understood. In this paper, the stability of an <inline-formula> <math display="inline"> <semantics> <mrow> <mi>Al</mi> <mo>/</mo> <msub> <mi>SiO</mi> <mn>2</mn> </msub> </mrow> </semantics> </math> </inline-formula> bimorph electrothermal MEMS mirror operated in both static and dynamic scan mode has been studied. Particularly, the angular drifts of the MEMS mirror plate were measured over 90 h at different temperatures in the range of <inline-formula> <math display="inline"> <semantics> <mrow> <mn>50</mn> </mrow> </semantics> </math> </inline-formula>&#8722;<inline-formula> <math display="inline"> <semantics> <mrow> <mn>150</mn> </mrow> </semantics> </math> </inline-formula> &#176;C. The experiments show that the temporal drift of the mirror plate orientation largely depends on the temperature of the electrothermal bimorph actuators. Interestingly, it is found that the angular drift changes from falling to rising as the temperature increases. An optimal operating temperature between <inline-formula> <math display="inline"> <semantics> <mrow> <mn>75</mn> </mrow> </semantics> </math> </inline-formula> &#176;C to <inline-formula> <math display="inline"> <semantics> <mrow> <mn>100</mn> </mrow> </semantics> </math> </inline-formula> &#176;C for the MEMS mirror is identified. At this temperature, the MEMS mirror exhibited stable scanning with an angular drift of less than <inline-formula> <math display="inline"> <semantics> <mrow> <mn>0.0001</mn> </mrow> </semantics> </math> </inline-formula>&#176;/h.