An accelerometer is fabricated by forming a proofmass and at least one associated hinge in a silicon substrate through a variety of a etching and bonding processes is disclosed. The processes entail ion implantation and formation of an oxide support layer below the proofmass, integrally bonding two complementary proofmass and substrate structures together, and then removing the oxide support layer to leave the proofmass supported by the hinge within the body of silicon material. The proofmass may be electrically connected to a lead extending through an etched recess in one of the substrates, and the proofmass may be electrically isolated or separated from the substrates by an oxide layer and by a change in conductivity type of the semiconductor material wherein the hinge is structurally mounted to the substrates. In a bond and etch back process, the wafer is processed, sawed in half, and then bonded together again wherein the complementary halves are joined to obtain the finished accelerometer. As part of the bond and etch-back process, an anchor for bridging the silicon substrate to an oxide support substrate includes using a selective epitaxy or non-selective epitaxy process to grow the polysilicon anchors.
This is a continuation-in-part application of a co-pending parent application Ser. No. 08/097,084 filed Jul. 26, 1993 by the same inventor, entitled "Electrostatically Force Balanced Silicon Accelerometer."
Substrate removal from a semiconductor chip having silicon-on-oxide (SOI) structure is enhanced via a method and system that provide a control for the removal process. According to an example embodiment of the present invention, a portion of substrate is removed from the back side of a semiconductor chip having a SOI structure and a backside opposite a circuit side. As the substrate is removed, secondary ions are sputtered from the back side. The sputtered ions are detected, and the substrate removal is controlled as a function of detected ions. In this manner, the portion of the substrate being removed can be detected and used to enhance the control of the substrate removal process, such as by detecting sputtered ions from the insulating portion of the SOI and using the insulating portion as an endpoint of the substrate removal process.
A semiconductor device has a flexible structure bonded to a semiconductor substructure to form a cavity. The flexible structure is bonded over a conducting feed-through without the feed-through interfering with a hermetic seal formed by bonding. One embodiment of the device includes depressions that contain edges of a diffused feed-through so that imperfections at the edge of the diffusion do not interfere with bonding. The flexible structure is bonded to elevated areas thus hiding the imperfections. In one embodiment, a first elevated region is surrounded by a second elevated region, and diffusion for the feed-through extends from an active region in the cavity across the first elevated region with edges of the diffusion being between the first and second elevated regions. The flexible structure can thus bond to the first and second elevated regions without interference from the edge of the diffused feed-through. A via through the flexible structure to the first elevated region provides electrical contact with the active region. Another embodiment has either a surface or buried well in a semiconductor structure and extending from an active region in the cavity to a point outside the perimeter of the flexible structure. The well provides a conductive feed-through structure without creating imperfections that would interfere with the bonding that seals the cavity.
A SOI (silicon on insulator) single crystalline chip structure is provided. The SOI chip structure has a first silicon layer for at least one SOI device to be placed thereon, at least one buried oxide area with a predetermined depth placed at a predetermined position of the first silicon layer in order to enable the first silicon layer to have at least two different silicon layer thicknesses. The buried oxide area is filled with a silicon oxide material serving as an insulating area, and a second silicon layer is located below the first silicon layer and the buried oxide area.
A monolithic substrate for acceleration and angular rate sensing. The substrate comprises a support frame, and a first accelerometer formed in the substrate. The first accelerometer has a proof mass including first and second opposite edges. A flexure connects the first edge of the proof mass to the support frame. The flexure defines a hinge axis for the proof mass. The first accelerometer further includes a torsion stabilizing strut coupling a portion of the proof mass to the frame.
A semiconductor device has a flexible structure bonded to a semiconductor substructure to form a cavity. The flexible structure is bonded over a conducting feed-through without the feed-through interfering with a hermetic seal formed by bonding. One embodiment of the device includes depressions that contain edges of a diffused feed-through so that imperfections at the edge of the diffusion do not interfere with bonding. The flexible structure is bonded to elevated areas thus hiding the imperfections. In one embodiment, a first elevated region is surrounded by a second elevated region, and diffusion for the feed-through extends from an active region in the cavity across the first elevated region with edges of the diffusion being between the first and second elevated regions. The flexible structure can thus bond to the first and second elevated regions without interference from the edge of the diffused feed-through. A via through the flexible structure to the first elevated region provides electrical contact with the active region. Another embodiment has either a surface or buried well in a semiconductor structure and extending from an active region in the cavity to a point outside the perimeter of the flexible structure. The well provides a conductive feed-through structure without creating imperfections that would interfere with the bonding that seals the cavity.
