In the optical communication industry, requirements of optical components are getting more and more severe. The optical devices suppliers have to provide smaller while cheaper components to meet customer's requirements. By applying semiconductor manufacturing process and other machining processes, kinds of high-precision and high-quality micro mechanical elements can be made in a mass production scale.
Movable micro mirror chip is a kind of micro component applicable in optical communication or display modules. The micro mirror chip mainly includes a mirror layer and an actuation layer. The mirror layer is a suspended mirror actuated to swing or revolve by electrostatic force of the actuation layer. The micro mirror chip works as an attenuator in optical communication by steering the light beam direction. The biggest challenge in fabrication of a conventional movable micro mirror chip is the positioning alignment of the mirror layer and the actuation layer. The alignment process requires operations of hands or specific positioning machines that cause a high manufacturing cost very difficult to be reduced.
U.S. Pat. No. 6,442,307 discloses a micro mirror device, in which the mirror layer and the actuation layer are jointed together by solder joints. Though the construction solves conduction and jointing problem, the solder joint does not provide precise positioning. Therefore, a spacer is user for the positioning function. However, when the solder melts, it loses its form. In order to stabilize the jointing and to remove the spacer after soldering, special materials for the spacer is required that makes the material selection very difficult. Also, the height of the solder layers is hard to be controlled after the large temperature variation. Moreover, since the mirror layer and the actuation layer all require electrical circuit to operate, there are wire-bonding areas on the layers that are easy to be stained by re-flow solder because there is no protection manner. The melted solder may stain the bonding areas and make the afterward wire bonding impossible, or even ruin the whole chip and increase fabrication cost of the product.