Sextant Avionique

Isabelle Thomas

Pierre O Lefort

Christophe Legoux

Olivier Lefort

A micro-accelerometer having three micromachined conducting-silicon plates bonded in superposition with the interposition of insulating layers. The central plate includes a subassembly sensitive to acceleration, and a peripheral frame electrically insulated from the subassembly and surrounding the subassembly. The peripheral frame forms a spacer between a lower plate and an upper plate from which it is also electrically insulated. The subassembly includes a base fixed on the lower plate and a cantilevered proof mass suspended from the base, an electrical connection being made between the lower plate and the base of the subassembly. The suspension of the proof mass includes, on the one hand, a central vibrating beam which is connected to the proof mass and to the base and is placed substantially in the horizontal plane of an upper face of the proof mass and, on the other hand, two short side suspension arms which are connected to the base and are placed on either side of the central beam but in a horizontal plane passing substantially through the center of gravity of the proof mass. Such a micro-accelerometer may find application for an aircraft, in the context of assisting with inertial navigation.

Micro-accelerometer with capacitive resonator

A process for the production of microsensors machined in silicon, and in particular accelerometers for applications of assisting with navigation in aircraft, and pressure sensors. In order to improve the production of certain active parts of the sensor, and in particular of a beam forming a resonator, which needs to have well-controlled width and thickness characteristics, the following procedure is adopted. A beam having a thickness equal to the desired final thickness, and a width greater than the desired final width, is produced by micromachining the silicon on a first plate, the beam being covered on its upper face by a mask defining the desired final width. The plate is assembled with another plate. The two faces of the beam are oxidized in order to cover them with a thin protective layer. The thin protective layer on the upper face is removed, by vertical directional etching, without removing the mask already present. The silicon in the area exposed by the preceding operation is attacked by a vertical directional etch on the upper face, until the entire part of the beam not protected by the mask is eliminated, and the beam having the desired width is thus formed.

Method for making a machined silicon micro-sensor

A capacitive micro-sensor includes a sandwich of at least two silicon plates. A peripheral stripe of each side of one plate is assembled to a corresponding stripe of the opposing surface of an adjacent plate through an insulating layer. The lateral sides of the sandwich are provided with notches partially penetrating in each of the insulating layers, and are thicker than the thickness of the insulating layers.

Capacitive micro-sensor with a lateral protection and manufacturing

A capacitive micro-sensor includes a sandwich of three silicon wafers, a peripheral stripe of each surface of the central plate being assembled to a corresponding stripe of an opposing external plate through an insulating layer. At least one of the external plates forms a first electrode, the central plate forms a second electrode and at least one portion of the central plate forms a variable capacity with at least one of the external layers. At least one of the insulating layers is formed by a sandwich of a first insulating layer, a conductive layer and a second insulating layer, the conductive layer being associated with connection means.

Capacitive micro-sensor with a low stray capacity and manufacturing

A capacitive micro-sensor includes a sandwich of three silicon plates, each surface of the frame region of the central plate being assembled to the opposing surface of each external plate through a thin layer forming an insulating stripe. At least one of the external plates forms a first electrode, and at least one central portion of the central plate forms a variable capacity with at least one of the external plates. The frame region of the central plate is electrically disconnected from the central portion. First contact means are coupled to the frame portion. Second contact means are coupled to the central portion and form a second electrode of the variable capacity.

Capacitative micro-sensor with a low stray capacity and manufacturing

A pressure micro-sensor is formed by a sandwich of three silicon plates in contact by their periphery, with an interposed insulating layer in order to define an internal cavity. The lower plate (2) includes a thinner region (21) forming a diaphragm, on its internal side. The intermediate plate (1) includes a peripheral region (11) forming a frame coupled to the upper and lower plates by a silicon oxide layer (24, 25), a first stud (13) mounted onto the thinner region of the lower plate, a second stud (14) mounted onto a thick region of the lower plate, and a silicon beam (15) forming a resonator and disposed between the upper surfaces of the first and second studs in front of the upper plate (3). A first electrode (32) is connected to the upper plate, a second electrode (33) is connected to the frame and a third electrode (31) is connected to the second stud.

Pressure micro-sensor

A resonator micro-accelerometer sensitive to accelerations along a first direction comprises, between two supporting plates, an intermediate plate etched so as to include a rectangular frame, the sides of which extend along a first (x) and a second (y) direction perpendicular to the first one. The two directions are orthogonal to a third direction (z). A seismic mass is located inside the frame. Hanging rods extend between the frame and the mass along the second direction, on both sides of the mass. The rods have substantially the same thickness as the mass and the frame along the third direction and a small width along the first direction. Resonators extend between the frame and mass and have a small thickness along the third direction.

Resonator micro-accelerometer

A pressure microsensor comprises, between two plates in an insulating material: a bottom silicon plate (3) forming a base; a middle silicon plate (2) constituting a diaphragm (11) surrounded by a frame (12), a first part (15) of a stud being formed at a decentred location of the diaphragm; and a top silicon plate (1) comprising a frame (17) corresponding to that of the middle plate, a second parts (16) of said stud and a silicon blade (18) constituting a resonator connecting the top of the stud to a high area of the frame. A measuring interval (13) is provided between the diaphragm and the bottom plate, this interval comprising an access (14, 28), and the two insulating plates (4, 5) cooperate with the border of the three assembled silicon plates to form a closed cavity.

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Valence, France

Isabelle Thomas