Delco Electronics Corporation

Purdue Research Foundation

Steven E Staller

Dan Wesley Chilcott

James H Logsdon

Douglas Ray Sparks

Han-Sheng Lee

William J Baney

James Werstler Siekkinen

David W De Roo

Mark Billings Kearney

Gerold W Neudeck

Peter J Schubert

David W DeRoo

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 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

This invention includes a method of making a bridge-supported accelerometer structure. A first wafer is worked, preferably by bulk micromachining, to provide a proof mass supported by a thin membrane on all sides. The thin membrane has the same thickness as the bridges to be defined therein. The first wafer is bonded to a second wafer having a cavity formed therein. The first wafer is then worked, preferably by plasma etching, to delineate bridges in the thin membrane. The cavity in the second wafer provides damping of the proof mass which reduced bridge breakage as portions of the thin membrane are removed leaving the final bridge-supported accelerometer structure. Combining the two wafers together prior to delineating the bridge provides for handling and processing of a much less fragile structure than the first wafer alone with bridges delineated therein.

Method of making a bridge-supported accelerometer structure

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

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.

Method of making and sealing a semiconductor device having an air path

A microaccelerometer is provided which has a silicon substrate bonded to a silicon capping plate and silicon back plate, wherein the bonds between the three silicon wafers are characterized by a relatively low residual stress level over a wide temperature range. The bonds are formed by means of an appropriate adhesive at a relatively low temperature without degradation to the microaccelerometer. The bonds between the silicon wafers also provide stress relief during use and packaging of the microaccelerometer. With this invention, the damping distance for the proof mass of the microaccelerometer is accurately controllable and stop means are provided for preventing excessive deflection of the proof mass in a direction perpendicular to the plane of the microaccelerometer.

Microaccelerometer having low stress bonds and means for preventing

Method of making a microaccelerometer having low stress bonds and means

A method is disclosed for forming thin, suspended membranes of epitaxial silicon material. Silicon oxide strips having a predetermined thickness are first formed on a silicon substrate. The gap, or spacing, between adjaceant beams is preferably less than or equal to about 1.4 times the thickness of the silicon oxide strip. The underlying silicon substrate is exposed within these gaps in the silicon oxide layer, thereby the gaps provide a seed hole for subsequent epitaxial growth from the silicon substrate. Epitaxial silicon is grown through the seed holes and then allowed to grow laterally over the silicon oxide strips to form a continuous layer of epitaxial silicon over the silicon oxide strips. The backside of the silicon substrate, or surface opposite the surface having the silicon oxide strips, is then masked to delineate the desired diaphragm and microbridge pattern. The silicon is etched conventionally from the backside. Etching is substantially terminated automatically by the presence of the silicon oxide strips. The thin, single crystal silicon membranes are suitable for use as diaphragms and microbridges in a microaccelerometers or pressure sensor.

Growing community of inventors

Kokomo, IN, United States of America

Steven E Staller