Patent ID: 7824945
Filing Date: 2010-11-02
Classification: B81B,B81C,H01L

Abstract:
1. A method for making micro-electromechanical system devices, comprising: (a) forming a sacrificial layer on a front side of a device wafer which has a plurality of active units, the device wafer including an active layer, a suspender layer, and an insulator layer sandwiched between the active layer and the suspender layer, the suspender layer and the active layer defining the front and back sides of the device wafer, respectively, the sacrificial layer being formed on the suspender layer, and the suspender layer patterned to form a plurality of through-holes therein at each of the active units prior to the formation of the sacrificial layer thereon; (b) forming a plurality of loop-shaped through-holes in the sacrificial layer so as to form the sacrificial layer into a plurality of enclosed portions, each of which is surrounded by a loop-shaped route of a respective one of the loop-shaped through-holes and each of which is aligned with a respective one of the active units of the device wafer, sacrificial layer extending into the through-holes in the suspender layer in step (a); (c) forming a plurality of cover caps on the sacrificial layer such that each of the cover caps is aligned with a respective one of the active units of the device wafer and extends into a respective one of the loop-shaped through-holes in the sacrificial layer to contact the front side of the device wafer so as to cooperate with a respective one of the active units of the device wafer to enclose a respective one of the enclosed portions of the sacrificial layer, the cover caps formed on the sacrificial layer by forming a cap-forming layer on the sacrificial layer such that the cap-forming layer extends into the through-holes, followed by patterning the cap-forming layer through photolithographic techniques; (d) forming a device through-hole in each of the active units of the device wafer so as to form an active part suspended in each of the active units of the device wafer and so as to expose a respective one of the enclosed portions of the sacrificial layer from a back side of the device wafer, the device through-hole in each of the active units (i) extending at least through the active layer and the insulator layer, and (ii) being in spatial communication with the through-holes in the suspender layer at the respective one of the active units, the device through-hole in each of the active units formed by forming a first hole in the active layer, followed by forming a second hole in the insulator layer that is in spatial communication with the first hole in the active layer and the through-holes in the suspender layer at the respective one of the active units; and (e) removing the enclosed portions of the sacrificial layer through the device through-holes in the active units of the device wafer.