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INTEGRATED MEDIA ISOLATED CAPACITATIVE PRESSURE SENSOR

IP.com Disclosure Number: IPCOM000006787D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2002-Feb-01
Document File: 2 page(s) / 92K

Publishing Venue

Motorola

Related People

Anita Brandes: AUTHOR [+5]

Abstract

Automotive and industrial customers require smaller packaged pressure sensors that will not be affected by their working environment. This invention integrates the electronics on one surface of a capacitative pressure sen- sor while isolating this surface from the environment. Potential applications where pressure sensing can be improved by immersing the diaphragm of a capacitive. pressure sensor in the media of interest include monitoring oil, gasoline and hydraulic fluid. Silicon and glass are the only materials directly exposed to the envi- ronment that is being monitored.

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INC. Technical Developments Volume 18 March 1993

INTEGRATED MEDIA ISOLATED CAPACITATIVE PRESSURE SENSOR

by Anita Brandes, Steven Chen, Carl Ross, Roseann Tomasello and Ruta Venclovas

  Automotive and industrial customers require smaller packaged pressure sensors that will not be affected by their working environment. This invention integrates the electronics on one surface of a capacitative pressure sen- sor while isolating this surface from the environment. Potential applications where pressure sensing can be improved by immersing the diaphragm of a capacitive. pressure sensor in the media of interest include monitoring oil, gasoline and hydraulic fluid. Silicon and glass are the only materials directly exposed to the envi- ronment that is being monitored.

  A Silicon Capacitive Absolute Pressure Sensor uti- lizes a metallized glass plate and a conductive silicon diaphragm as two plates of the pressure sensor. To build the sensors, two conductive feed throughs are needed through the glass. Ultrasonic drilling can be used to make two holes in the glass. Conductive glass frit is then used to fill both feed through holes. The top and bottom sur- faces of the glass are finely ground and polished to the desired thickness and finish.

  Next the glass can be metal&d and patterned. Sput- ter deposited thin film metal, such as chromium-nickel- gold, can be deposited on the top and bottom surfaces of the glass. Metal patterned on the bottom surface of the glass forms 1) an electrode which will be one plate of the capacitor and 2) a contact pad to the silicon dia- phragm. The electrode is patterned around one conduc- tive feed through in the glass and the contact pad to the silicon is patterned around the second conductive feed through.

  Thin film metals, deposited on the top surface of the glass, arc patterned to form a trimmable resistor net- work wi...