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Design and Fabrication of an Integrated Ph, Oxygen Content and Temperature Sensor

IP.com Disclosure Number: IPCOM000121136D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 132K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+4]

Abstract

A device for the simultaneous measurement of the Ph, partial pressure of oxygen and temperature of a solution is described herein, together with a method for fabricating same. The device is fabricated using microelectronic technology and has a wide variety of applications. In particular, it is extremely valuable in biomedical applications. The fast and accurate measurement of the blood levels of the partial pressure of oxygen, the partial pressure of carbon dioxide and the concen tration of hydrogen ions (Ph) are vital in the diagnosis and treatment of many pathological conditions. These measurements are usually made on specimens of arterial blood using risky techniques and large sensor/instrument packages.

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Design and Fabrication of an Integrated Ph, Oxygen Content and Temperature
Sensor

      A device for the simultaneous measurement of the Ph,
partial pressure of oxygen and temperature of a solution is described
herein, together with a method for fabricating same.  The device is
fabricated using microelectronic technology and has a wide variety of
applications.  In particular, it is extremely valuable in biomedical
applications.  The fast and accurate measurement of the blood levels
of the partial pressure of oxygen, the partial pressure of carbon
dioxide and the concen tration of hydrogen ions (Ph) are vital in the
diagnosis and treatment of many pathological conditions.  These
measurements are usually made on specimens of arterial blood using
risky techniques and large sensor/instrument packages.

      The layout of the integrated sensor is shown in the figure.
Area A is the Ph sensor using a PdO layer.  Area B is the Ag/AgC1
reference electrode for the Ph sensor.  Area C is the oxygen sensor
using a counter and working electrode.  Area D is a temperature
sensor using a diode, thermocouple, or thermistor.  The unique
feature of the device lies in that, through the use of silicon
microelectronic technology, the various sensors have been integrated
into a single miniature package.

      The fabrication of the sensor device is described below.  The
first step is to deposit a blanket film of palladium oxide using RF
diode sputtering onto oxidized silicon substrates.  Next, using the
first photolithographic level, the pattern for the PdO sensor pads is
formed in resist on the wafer.  This pattern is transferred into the
underlying PdO layer using argon ion beam etching.  This resist layer
is removed and another resist layer is deposited and patterned for
use as a lift-off stencil.  A layer of chromium and then a layer of
gold are deposited by electron beam evaporation.  These layers form
the working electrode and counterelectrode for the oxygen sensor.
The undesired metal is removed by dissolving the resist layer in
acetone or some suitable solvent and lifting off the metal. Next, the
silver reference electrode is prepared in the same manner as the gold
electrode using evaporation and the lift-off technique.  The entire
device surface is covered with photoresist and openings in the resist
are formed in appropriate areas on the electrodes.  This resist layer
is used as a dielectric and the aspect ratio of the openings must be
greater t...