A micromachined capacitor structure having integral travel stops (19, 22, 22') within an active region of the capacitor is provided. The capacitor structure is formed on a substrate (11) and includes a moving capacitor plate (15) supported by one or more flexing arms (17) mechanically anchored to the substrate (11). The moving capacitor plate (15) has an active region (15) substantially parallel to the substrate (11) and separated from the substrate (11) by a first spacing. A corrugation (19) is formed in the moving capacitor plate (15) over the substrate (11) and separated from the substrate (11) by a second spacing, wherein the second spacing is smaller than the first spacing.
A double pinned micromachined sensor (11) which utilizes a laminated film (27) having overall tensile strength formed on top of a silicon substrate (16). The laminated film (27) comprises a layer of silicon nitride (18) encapsulated by two layers of polysilicon (19, 21), the silicon nitride (18) providing overall tension for the laminated film. The laminated film (27) is supported above the silicon substrate by support posts (17) and is selectively etched to form a sensor (11, 13).
A micromachined capacitor structure having a first anchor (12) attached to the substrate (24), a tether (13) coupled to the anchor (12) and having a portion free to move in a lateral direction over the substrate (24) in response to acceleration. A tie-bar (14) is coupled to the movable portion of the tether (13), and at least one movable capacitor plate (16) is coupled to the tie bar (13). A first fixed capacitor plate (16) is attached to the substrate (24) laterally overlapping and vertically spaced from the at least one movable capacitor plate (16).
A sensor (11) has a movable plate (16) that moves in response to an external acceleration. The movable plate (16) has a finger (17) that is capacitively coupled to fingers (13,14) that are attached to a substrate (12). A travel stop (19) is used to stop the movable plate (16) before the finger (17) on the movable plate (16) collides into the fingers (13,14) on the substrate (12).
An acceleration sensor and a method of making an acceleration sensor is described in which a movable sensor element is located in a hollow space formed in the middle of three silicon plates. During production, air can be removed from the hollow space through a hole in one of the two outer plates. The hole is then closed by an additional plate, which allows for a defined pressure to be set in the hollow space.
A sensor has an electrode (120) that is movable along three mutually perpendicular axes (10, 11, 12). The sensor also has stationary over-travel limiting structures that restrict the movement of the electrode (120) along the three axes (10, 11, 12).
