Micromotion amplifier

#This application claims the benefit of U.S. Provisional application Ser. No. 60/000,437, filed Jun. 23, 1995, the disclosure of which is hereby incorporated herein by reference.

#The present invention relates, in general, to microelectromechanical motion (MEM) amplifiers, and more particularly to microelectromechanical structures wherein a small driving motion in an axial direction applied to a structure produces a relatively large motion in a direction transverse to the axial drive motion, thereby amplifying the drive motion, the structure of the invention providing an amplification of about two orders of magnitude.

#In micromechanical systems, for example of the type illustrated in U.S. Pat. No. 5,506,175 to Zhang and MacDonald, motion of a rigid MEM body is typically obtained by attaching that body to an actuator which is then activated to generate the motion.

#The foregoing, and additional objects, features and advantages of the present invention will become apparent from a consideration of the following detailed description of preferred embodiments thereof, taken in conjunction with the accompanying drawing, in which:

#FIGS. 1, 2 and 3 illustrate in diagrammatic form the transverse buckling response of a long slender beam to an axial compressive force;

#FIGS. 4, 5 and 6 illustrate in diagrammatic form the transverse buckling response of two parallel beams supporting a stage in response to an axial compressive force;

#Turning now to a more detailed consideration of the present invention, there is illustrated in FIG. 1 a long slender, flexible beam 10 which is clamped at one of its ends 12 and 14 to at least one drive actuator. In the illustrated embodiment, end 14 is secured to a fixed reference such as a surface 16, while end 12 is secured to a drive actuator such as movable actuator element 18. The beam 10 preferably is an elongated, thin, flexible microelectromechanical (MEM) structure fabricated, for example, from single crystal silicon utilizing the SCREAM process described above. The beam 10 may have a length L of, for example, 3-5 millimeters, or more, may have a transverse width W of 1 or 2 micrometers and may have a depth, perpendicular to the plane of FIG. 1, of about 12 micrometers. This cross-sectional shape provides a beam that has a high aspect ratio so that it is transversely flexible, and is relatively inflexible in the perpendicular direction.

#The beam 10 may be fabricated in a cavity or trench 20 formed in a substrate or wafer 22, with the end 14 of the beam being unitary with surface 16 which may be, for example, a wall of the cavity 20 in which the beam is located. In similar manner, the end 12 of the beam 10 may be unitary with element 18 which preferably is part of an actuator fabricated simultaneously with the fabrication of beam 10, and which may be, for example, the movable part of a comb-type actuator 24 having interleaved movable and stationary fingers 26 and 28, respectively. As illustrated, the stationary fingers 28 may be fabricated as part of fixed supports 29 extending from the floor of cavity 20. The beam 10 originates at wall 16 at end 14, and is released for motion with respect to the substrate or wafer from which the device is fabricated, in the manner described, for example, in the aforesaid Pat. No. 5,198,390, with the end 12 being held by actuator 24. If desired, the movable element 18 may be supported by lateral spring arms 30 and 31 extending to the cavity wall.

#Energization of the actuator 24, as by application of a suitable voltage V across the opposed capacitor finger plates 26 and 28 of actuator 24 to cause the plates to tend to move closer together will apply a force P (FIG. 2) to the end 12 of beam 10, with the force being applied along the longitudinal axis 32 of the beam. This axial force tends to compress the beam, but as long as