Becton Dickinson and Company Limited

Becton, Dickinson Electronics Company

Herbert V Wong

L Bruce Wilner

The invention relates to a process for producing silicon diaphragm pressure transducers, and to pressure transducers so produced, which will operate in high temperature applications above 150.degree. C. by properly insulating the strain gauges from the diaphragm. This is achieved by utilizing two properly oriented silicon wafers which are joined together by a two-step diffusion technique, which includes the diffusion bonding of one boron doped wafer surface into the other wafer surface previously oxide coated, at greatly reduced pressures and temperatures than heretofore used. This simultaneous diffusion takes place because of prior contouring or the forming of relief channels into one of the bonded surfaces, and because only one joined surface is oxide coated, thus reducing process times substantially. That is, there is a continuous diffusion of boron into the boron oxide coated surface resulting in a boron rich layer of great uniformity. The process includes a mechanical lapping and selective etching which leaves the extraordinarily level boron rich surface which is very uniform and ready for processing and connection into other transducer parts. The invention is particularly advantageous in the ease of fabrication which reduces the cost of the final transducer.

High temperature layered silicon structures

Process for producing high temperature pressure transducers and

An electromechanical transducer is provided which employs a piezoresistive substrate support body of semiconductive material of which a first type N or P and a lineal resistor composed of material of a second type (P or N) formed on one surface thereof. The support body has a reduced neck intermediate two pads. The lineal resistor extends between the pads and across the neck on one side of the support body. The lineal resistor is formed by diffusing semiconductive material of the second type of conductivity into the substrate material. Strain is detected by measuring the change in resistance of the lineal resistor. When the transducer is subjected to strain, the resistance changes by an amount depending on the strain. While the electrical current flows through the resistor, heat developed in the resistors flows into the neck and then is conducted through the flaring portions of the neck to the pads and then to an object under test.

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San Francisco, CA, United States of America

Herbert V Wong