Delco Electronics Corporation

Dan Wesley Chilcott

Steven E Staller

Douglas Ray Sparks

Mark Billings Kearney

Han-Sheng Lee

William J Baney

James Werstler Siekkinen

Su-Chee Simon Wang

James H Logsdon

Peter J Schubert

George Qin Jiang

Johnna Lee Haller

Joseph Keith Folsom

An all-silicon monolithic capacitive absolute pressure-sensing device and method for making the same. The device employs a single-crystal silicon diaphragm that serves at a flexible capacitor plate of a variable capacitor. The diaphragm is bonded to a single-crystal silicon wafer to overlie a cavity etched into the wafer. A fixed capacitor plate of the variable capacitor is formed by a heavily-doped region at the bottom of the cavity. A thin dielectric layer is grown on the fixed capacitor plate to complete the capacitor. The cavity has a minimal depth such that the fixed capacitor plate provides overpressure protection for the diaphragm. At least a portion of the operating range of the pressure sensor occurs while the diaphragm is contacting the doped region. As a result, the capacitive output signal of the pressure sensor is produced by changes in contact area between the diaphragm and a thin dielectric situated on the doped region in response to pressure applied to the diaphragm.

All-silicon capacitive pressure sensor

A process for bulk micromachining a silicon wafer to form a silicon micromachined structure. The process involves the application of a protective film on one or more surfaces of the silicon wafer to protect metallization and circuitry on the wafer during the bulk micromachining process, during which a wet chemical etchant is employed to remove bulk silicon from a surface of the silicon wafer. The protective film is divinylsiloxane bisbenzocyclobutene (BCB), which has been found to be highly resistant to a wide variety of wet chemical etchants, and retains such resistant at elevated temperatures commonly preferred for bulk silicon etching. The degree to which this material is cured prior to etching is advantageously tailored to promote its resistance to the etchant and promote its adhesion to the silicon wafer.

Method of protecting silicon wafers during wet chemical etching

A method for making and vacuum packaging a silicon micromachined motion sensor, such as a gyroscope, at the chip level. The method involves micromachining a trench-isolated sensing element in a sensing chip, and then attaching a circuit chip to enclose the sensing element. Solder bumps serve to attach the circuit chip to the sensing chip, form a hermetic seal to enable vacuum-packaging of the sensor, and electrically interconnect the sensing chip with the circuit chip. Conductive runners formed on the enclosed surface of the circuit chip serve to electrically interconnect the sensing element with its associated sensing structures.

Silicon micromachined motion sensor and method of making

A motion sensor including a sensing wafer with a bulk micromachined sensing element, and a capping wafer on which is formed the conditioning circuitry for the sensor. The sensing and capping wafers are configured such that, when bonded together, the capping wafer encloses the sensing element to form a monolithic sensor. The capping wafer is further configured to expose bond pads on the sensing wafer, and to enable singulation of the two-wafer stack into individual dies. Wire bonds can be made to both wafers, such that the sensor can be packaged in essentially any way desired.

All-silicon monolithic motion sensor with integrated conditioning circuit

Method for making an all-silicon capacitive pressure sensor

A process for silicon wafer-to-wafer bonding at temperatures lower than 500.degree. C. has been developed. It consists of (1) treating the cleaned surfaces to make them smooth and hydrophilic, (2) initiating the bond by making intimate contact between wafers and (3) enhancing the bond strength at elevated temperatures. This bonding process can be applied to sensor packaging.

Method of bonding silicon wafers at temperatures below 500 degrees

Generally, the invention includes a method of wet electrochemical etching of a substrate with an anisotropic etchant using a silver/silver oxide (Ag/Ag.sub.2 O) reference electrode. The silver/silver oxide reference electrode can be used with electrochemical etch-stop techniques to fabricate a variety of semiconductor devices including microsensors and microactuator in a variety of anisotropic etchants. The silver/silver oxide reference electrode eliminates the need to use glass or plastic tubes.

Method of etching using a silver/silver oxide reference electrode

This invention generally relates to the provision of a vent path during the bonding of silicon wafers and the subsequent encapsulation of the individual devices. A double-sided polished silicon wafer is used for the device wafer. The device wafer includes circuitry, thin membranes and metal interconnections. When bonding a bottom wafer to the device wafer, a vented path exists between the wafers. The venting path includes serpentine shape channel formed by interdigitated fingers and cavities. The cavity and the interdigitated patterns can be etched either together or separately into either wafer. A top wafer has a cavity formed therein. When the top device and bottom wafers are bonded together, the venting path is sealed by dipping the device in a sealing liquid. The serpentine path prevents the sealing liquid from reaching the cavity.

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Sharpsville, IN, United States of America

Dan Wesley Chilcott