Abstract: A MEMS device (40) includes a base structure (42) and a microstructure (44) suspended above the structure (42). The base structure (42) includes an oxide layer (50) formed on a substrate (48), a structural layer (54) formed on the oxide layer (50), and an insulating layer (56) formed over the structural layer (54). A sacrificial layer (112) is formed overlying the base structure (42), and the microstructure (44) is formed in another structural layer (116) over the sacrificial layer (112). Methodology (90) entails removing the sacrificial layer (112) and a portion of the oxide layer (50) to release the microstructure (44) and to expose a top surface (52) of the substrate (48). Following removal, a width (86) of a gap (80) produced between the microstructure (44) and the top surface (52) is greater than a width (88) of a gap (84) produced between the microstructure (44) and the structural layer (54).

Abstract: Methods for fabricating crack resistant Microelectromechanical (MEMS) devices are provided, as are MEMS devices produced pursuant to such methods. In one embodiment, the method includes forming a sacrificial body over a substrate, producing a multi-layer membrane structure on the substrate, and removing at least a portion of the sacrificial body to form an inner cavity within the multi-layer membrane structure. The multi-layer membrane structure is produced by first forming a base membrane layer over and around the sacrificial body such that the base membrane layer has a non-planar upper surface. A predetermined thickness of the base membrane layer is then removed to impart the base membrane layer with a planar upper surface. A cap membrane layer is formed over the planar upper surface of the base membrane layer. The cap membrane layer is composed of a material having a substantially parallel grain orientation.

Abstract: A microelectromechanical systems (MEMS) device includes at least two rate sensors (20, 50) suspended above a substrate (30), and configured to oscillate parallel to a surface (40) of the substrate (30). Drive elements (156, 158) in communication with at least one of the rate sensors (20, 50) provide a drive signal (168) exhibiting a drive frequency. One or more coupling spring structures (80, 92, 104, 120) interconnect the rate sensors (20, 50). The coupling spring structures enable oscillation of the rate sensors (20, 50) in a drive direction dictated by the coupling spring structures. The drive direction for the rate sensors (20) is a rotational drive direction (43) associated with a first axis (28), and the drive direction for the rate sensors (50) is a translational drive direction (64) associated with a second axis (24, 26) that is perpendicular to the first axis (28).

Abstract: A MEMS device (40) includes a base structure (42) and a microstructure (44) suspended above the structure (42). The base structure (42) includes an oxide layer (50) formed on a substrate (48), a structural layer (54) formed on the oxide layer (50), and an insulating layer (56) formed over the structural layer (54). A sacrificial layer (112) is formed overlying the base structure (42), and the microstructure (44) is formed in another structural layer (116) over the sacrificial layer (112). Methodology (90) entails removing the sacrificial layer (112) and a portion of the oxide layer (50) to release the microstructure (44) and to expose a top surface (52) of the substrate (48). Following removal, a width (86) of a gap (80) produced between the microstructure (44) and the top surface (52) is greater than a width (88) of a gap (84) produced between the microstructure (44) and the structural layer (54).

Abstract: A spring system (74) links a pair of drive masses (30, 32) of a MEMS device (72). The spring system (74) includes stiff beams (76, 78, 80, 82) oriented to form a parallelogram arrangement (84). The beams are oriented diagonal to a drive direction (56) of the masses (30, 32). Diagonally opposing corners (86, 88) of the parallelogram arrangement (84) are coupled to the drive masses (30, 32). A spring (90) is coupled to a corner (94) and a spring (92) is coupled to a diagonally opposing corner (96) of the parallelogram arrangement. The springs (90, 92) are interconnected with a sense frame (34) surrounding the drive masses. The beams and side springs are stiff to substantially prevent in-phase motion (66) of the drive masses. However, rotationally compliant flexures (102, 104, 106, 108), allow the arrangement (84) to collapse and expand to enable anti-phase motion (60) of the drive masses.

Abstract: A MEMS device (20) includes a movable element (20) suspended above a substrate (22) by a spring member (34) having a spring constant (104). A spring softening voltage (58) is applied to electrodes (24, 26) facing the movable element (20) during a powered mode (100) to decrease the stiffness of the spring member (34) and thereby increase the sensitivity of the movable element (32) to an input stimulus (46). Upon detection of a stiction condition (112), the spring softening voltage (58) is effectively removed to enable recovery of the movable element (32) from the stiction condition (112). A higher mechanical spring constant (104) yields a stiffer spring (34) having a larger restoring force (122) in the unpowered mode (96) in order to enable recovery from the stiction condition (112). A feedback voltage (56) can be applied to feedback electrodes (28, 30) facing the movable element (32) to provide electrical damping.

Abstract: Methods for fabricating crack resistant Microelectromechanical (MEMS) devices are provided, as are MEMS devices produced pursuant to such methods. In one embodiment, the method includes forming a sacrificial body over a substrate, producing a multi-layer membrane structure on the substrate, and removing at least a portion of the sacrificial body to form an inner cavity within the multi-layer membrane structure. The multi-layer membrane structure is produced by first forming a base membrane layer over and around the sacrificial body such that the base membrane layer has a non-planar upper surface. A predetermined thickness of the base membrane layer is then removed to impart the base membrane layer with a planar upper surface. A cap membrane layer is formed over the planar upper surface of the base membrane layer. The cap membrane layer is composed of a material having a substantially parallel grain orientation.

Abstract: An inertial sensor (20) includes a drive mass (30) configured to undergo oscillatory motion and a sense mass (32) linked to the drive mass (30). On-axis torsion springs (58) are coupled to the sense mass (32), the on-axis torsion springs (58) being co-located with an axis of rotation (22). The inertial sensor (20) further includes an off-axis spring system (60). The off-axis spring system (60) includes off-axis springs (68, 70, 72, 74), each having a connection interface (76) coupled to the sense mass (32) at a location on the sense mass (32) that is displaced away from the axis of rotation (22). Together, the on-axis torsion springs (58) and the off-axis spring system (60) enable the sense mass (32) to oscillate out of plane about the axis of rotation (22) at a sense frequency that substantially matches a drive frequency of the drive mass (30).

Abstract: A calibration system (20) configured for communication with an inertial sensor (22) includes a signal generator (24) and processing system (26). A calibration process (60) performed using the calibration system (20) includes applying (90) an electrical stimulus (44) to the inertial sensor (22), receiving an output signal (46) from the sensor (22) produced in response to the electrical stimulus (44) and determining a sensitivity (108) of the inertial sensor (22) to the electrical stimulus (44) in response to the output signal (46) and an applied voltage of the electrical stimulus (44). A sensitivity (112) of the inertial sensor (22) to an inertial stimulus is calculated using the sensitivity (108) and a measured resonant sensitivity (114) of the inertial sensor (22), and the calculated sensitivity (112) is utilized to adjust a gain value (56) for the inertial sensor (22) to calibrate the sensor (22).

Abstract: A MEMS pressure sensor device is provided that can provide both a linear output with regard to external pressure, and a differential capacitance output so as to improve the signal amplitude level. These benefits are provided through use of a rotating proof mass that generates capacitive output from electrodes configured at both ends of the rotating proof mass. Sensor output can then be generated using a difference between the capacitances generated from the ends of the rotating proof mass. An additional benefit of such a configuration is that the differential capacitance output changes in a more linear fashion with respect to external pressure changes than does a capacitive output from traditional MEMS pressure sensors.

Abstract: A MEMS device (20) includes a proof mass (32) coupled to and surrounding an immovable structure (30). The immovable structure (30) includes fixed fingers (36, 38) extending outwardly from a body (34) of the structure (30). The proof mass (32) includes movable fingers (60), each of which is disposed between a pair (62) of the fixed fingers (36, 38). A central area (42) of the body (34) is coupled to an underlying substrate (24), with the remainder of the immovable structure (30) and the proof mass (32) being suspended above the substrate (24) to largely isolate the MEMS device (20) from package stress, Additionally, the MEMS device (20) includes isolation trenches (80) and interconnects (46, 50, 64) so that the fixed fingers (36), the fixed fingers (38), and the movable fingers (60) are electrically isolated from one another to yield a differential device configuration.

Abstract: A MEMS sensor (20, 86) includes a support structure (26) suspended above a surface (28) of a substrate (24) and connected to the substrate (24) via spring elements (30, 32, 34). A proof mass (36) is suspended above the substrate (24) and is connected to the support structure (26) via torsional elements (38). Electrodes (42, 44), spaced apart from the proof mass (36), are connected to the support structure (26) and are suspended above the substrate (24). Suspension of the electrodes (42, 44) and proof mass (36) above the surface (28) of the substrate (24) via the support structure (26) substantially physically isolates the elements from deformation of the underlying substrate (24). Additionally, connection via the spring elements (30, 32, 34) result in the MEMS sensor (22, 86) being less susceptible to movement of the support structure (26) due to this deformation.

Abstract: A microelectromechanical systems (MEMS) sensor (40) includes a substrate (46) and a suspension anchor (54) formed on a planar surface (48) of the substrate (46). A first folded torsion spring (58) and a second folded torsion spring (60) interconnect the movable element (56) with the suspension anchor (54) to suspend the movable element (56) above the substrate (46). The folded torsion springs (58, 60) are each formed from multiple segments (76) that are linked together by bar elements (78) in a serpentine fashion. The folded torsion springs (58, 60) have an equivalent shape and are oriented relative to one another in rotational symmetry about a centroid (84) of the suspension anchor (54).

Abstract: A microelectromechanical systems (MEMS) sensor (20) includes a substrate (26) and suspension anchors (34, 36) formed on a planar surface (28) of the substrate (26). The MEMS sensor (20) further includes a first movable element (38) and a second movable element (40) suspended above the substrate (26). Compliant members (42, 44) interconnect the first movable element (38) with the suspension anchor 34 and compliant members (46, 48) interconnect the second movable element (40) with the suspension anchor (36). The movable elements (38, 40) have an equivalent shape. The movable elements may be generally rectangular movable elements (38, 40) or L-shaped movable elements (108, 110) in a nested configuration. The movable elements (38, 40) are oriented relative to one another in rotational symmetry about a point location (94) on the substrate (26).

Abstract: A resonant accelerometer (24) includes a single anchor (28) fixed to a substrate (32). A proof mass (34) is positioned above a surface (30) of the substrate (32) and is positioned symmetrically about the anchor (28). The proof mass (34) has a central opening (38). Each of a number of suspension beams (42, 44, 46, 48) resides in the central opening (38) and has one end (50) affixed to the anchor (28) and another end (52) attached to an inner peripheral wall (40) of the proof mass (34). A resonant frequency of the beams (42, 44) in a direction (64) aligned with a common axis (58) of the beams (42, 44) changes according to acceleration in the direction (64). A resonant frequency of the beams (46, 48) in a direction (66) aligned with a common axis (62) of the beams (46, 48) changes according to acceleration in the direction (66).

Abstract: An inertial sensor (20) includes a drive mass (30) configured to undergo oscillatory motion and a sense mass (32) linked to the drive mass (30). On-axis torsion springs (58) are coupled to the sense mass (32), the on-axis torsion springs (58) being co-located with an axis of rotation (22). The inertial sensor (20) further includes an off-axis spring system (60). The off-axis spring system (60) includes off-axis springs (68, 70, 72, 74), each having a connection interface (76) coupled to the sense mass (32) at a location on the sense mass (32) that is displaced away from the axis of rotation (22). Together, the on-axis torsion springs (58) and the off-axis spring system (60) enable the sense mass (32) to oscillate out of plane about the axis of rotation (22) at a sense frequency that substantially matches a drive frequency of the drive mass (30).

Abstract: A microelectromechanical systems (MEMS) sensor device (20) includes a substrate (22) having sensors (24, 26) disposed on the same side (28) of the substrate (22) and laterally spaced apart from one another. The sensor (26) includes a sense element (56), and the substrate (22) includes a cavity (58) extending through the substrate (22) from the backside (30) of the substrate (22) to expose the sense element (56) to an external environment (54). The sense element (56) is movable in response to a stimulus (52) from the environment (54) due to its exposure to the environment (54) via the cavity (58). Fabrication methodology (66) entails concurrently forming the sensors (24, 26) on substrate (22) by implementing MEMS process flow, followed by creating the cavity (58) through the substrate (22) to expose the sense element (56) to the environment (54).

Abstract: An angular rate sensor (20) includes conductive plates (24, 26, 28, 30) mounted on a substrate (22), and a structure (34) coupled to the substrate (22). The structure (34) includes a drive mass (36) and a sense mass (40) suspended above the plates (24, 26, 28, 30). The sense mass (40) includes regions (50, 52) separated by a sense axis of rotation (48). Each of the regions (50, 52) has an outer surface (56) and an inner surface (54). An inner gap (68) exists between the inner surface (54) and plates (24, 26, 28). An outer gap (70) exists between the outer surface (56) and the plate (30). The outer gap (70) is larger than the inner gap (68). Plates (24, 26, 28) may be electrodes for force feedback, frequency tuning, and/or quadrature compensation. Plates (30) may be electrodes for sensing angular velocity.

Abstract: A MEMS device (20) includes a proof mass (32) coupled to and surrounding an immovable structure (30). The immovable structure (30) includes fixed fingers (36, 38) extending outwardly from a body (34) of the structure (30). The proof mass (32) includes movable fingers (60), each of which is disposed between a pair (62) of the fixed fingers (36, 38). A central area (42) of the body (34) is coupled to an underlying substrate (24), with the remainder of the immovable structure (30) and the proof mass (32) being suspended above the substrate (24) to largely isolate the MEMS device (20) from package stress, Additionally, the MEMS device (20) includes isolation trenches (80) and interconnects (46, 50, 64) so that the fixed fingers (36), the fixed fingers (38), and the movable fingers (60) are electrically isolated from one another to yield a differential device configuration.

Abstract: A MEMS device (40) includes a base structure (42) and a microstructure (44) suspended above the structure (42). The base structure (42) includes an oxide layer (50) formed on a substrate (48), a structural layer (54) formed on the oxide layer (50), and an insulating layer (56) formed over the structural layer (54). A sacrificial layer (112) is formed overlying the base structure (42), and the microstructure (44) is formed in another structural layer (116) over the sacrificial layer (112). Methodology (90) entails removing the sacrificial layer (112) and a portion of the oxide layer (50) to release the microstructure (44) and to expose a top surface (52) of the substrate (48). Following removal, a width (86) of a gap (80) produced between the microstructure (44) and the top surface (52) is greater than a width (88) of a gap (84) produced between the microstructure (44) and the structural layer (54).