Abstract: A semiconductor device (8) has a movable gate (20) over a semiconductor substrate (14) having a top surface (30). Source and drain regions (16-19) are in the substrate, and a channel region (24,25) is between the source and drain regions. The gate is suspended above the source and drain regions such that the gate is movable in a plane substantially parallel to the top surface of the substrate. In one embodiment the device is an accelerometer having the gate connected to a beam (10) with an aspect ratio between 2:1 and 10:1. Also, the gate can have first and second levels (22,23) corresponding to first and second threshold voltages of the channel region.

Abstract: A semiconductor device (15) having a sensor (11) and a transistor (10) formed on a monolithic semiconductor substrate (16). The sensor (11) has a source region (41), a drain region (42), and a microstructure (12) which is formed from a conductive layer (28). The microstructure (12) modulates a channel region between the source and drain regions (41,42). The transistor has a gate structure, a portion of which is formed from the same conductive layer (28) used to form the microstructure (12). Anneal steps are performed on the conductive layer (28) to remove stress prior to the formation of source and drain regions (34,36) of the transistor (10). A self-test structure (14) is formed adjacent to the microstructure (12) which is used to calibrate and verify the operation of the sensor (11).

Abstract: A method for forming a semiconductor sensor FET device (2) comprises the steps of forming spaced-apart doped source (6) and drain (8) regions in a semiconductor substrate (4) with electrically conductive paths (16, 18) to each region. The region between the source (6) and drain (8) regions defines a gate region (12). An insulating layer (14, 15) is formed on the substrate (4) and source and drain regions (8), and a cantilever gate structure is formed using a sacrificial layer (60), such that a gate electrode (26) is supported on a cantilever support (28) and a cavity (22) separates the gate electrode (26) from the gate region (12). A conductive layer (34) is formed overlying the gate electrode (26) to provide a heater for the gate electrode (26). The chemical species collect in the cavity (22) and react with the surface (27) of the gate electrode (26).

Abstract: A micromachined structure having at least one anchor that includes a supporting substrate with a first and a second foot fixedly positioned on the surface of the substrate and each foot has a supporting edge, which edges are positioned in parallel spaced apart relationship, an elongated tether positioned in spaced relation from the surface of the substrate and extending from the micromachined structure parallel to the parallel supporting edges of the first and the second foot, and first and second risers extending along the supporting edges of the first foot and the second foot, respectively, and rising upwardly to the edges of the tether. The first and the second foot, the first and second risers and the tether being formed integrally by surface micromachining.

Abstract: An enclosure (8) for an electronic device (26) such as, for example, an accelerometer. The enclosure (8) includes a conductive semiconductor substrate (12) underlying the electronic device (26), a conductive cap (16) overlying the electronic device (26), and a power supply (25) having one or more outputs (27, 29) each with a substantially fixed potential wherein one output is electrically coupled to the conductive semiconductor substrate (12) and another output to the conductive cap (16). In a preferred embodiment, substrate ( 12 ) and cap (16) are coupled to the same power supply output (27). This coupling substantially eliminates the adverse effects of parasitic capacitances of the substrate (12) and cap (16) to reduce measurement error and EMI when a capacitive accelerometer is used as the electronic device (26).

Abstract: A three axis accelerometer includes a semiconductor substrate with a plurality of layers of conductive material formed thereon by semiconductor manufacturing techniques, with each layer defining a plane and mounted in parallel spaced relation to each other. A first of the layers is fixedly mounted and a second layer is mounted for limited movement relative to the first layer with the first and second layers forming a first capacitance varying in accordance with acceleration of the accelerometer along a first axis defined by the first and second layers. A plurality of first surfaces and a plurality of electrically isolated plates are formed as a portion of the first and the second layers, respectively, and positioned in parallel juxtaposition, with the plates being moveable relative to the first layer.

Abstract: 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).

Abstract: 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).

Abstract: 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.

Abstract: A method of fabricating a surface micromachined structure is comprised of the steps of providing a semiconductor substrate having a dynamic element partially supported above the semiconductor substrate by a release layer and having a metal contact layer disposed on the dynamic element, forming a protection layer over the metal contact layer, and removing the release layer and the protection layer with an etchant that etches the protection layer at a slower rate than the release layer.

Abstract: A micro-mechanical sensor having a field effect transistor formed in a proof mass portion of a substrate is provided. The proof mass portion is attached to a support portion of the substrate by a means for flexing such as a diaphragm or cantilever beam. A gate electrode is formed over a channel region of the field effect transistor and separated from the channel region by a gap whereby force applied to the sensor causes the proof mass portion to move towards the gate electrode due to flexing of the flexing means. As the channel region moves closer to the gate electrode, current flows through the field effect transistor generating an output signal.

Abstract: An integrated circuit structure is provided in which component isolation is achieved after all diffused junction formation is complete. An anisotropically etched moat provides isolation. The surfaces of the moat are lined with oxide and a planar wafer surface is restored by filling the moat with metal. The subsurface metal region can then be used as a conductor for component interconnection.