Integrated ambient sensing devices and methods of manufacture

DETAILED DESCRIPTION We have devised a method for forming multi-element probes on a single monolithic substrate such as a silicon planar device using photolithographic techniques to pattern the multiplicity of chemically sensitive layers taking into account the wide range of plastic, gelatinous and ceramic material to be patterned and the problems of their cross-contamination when in contact.
In accordance with one aspect of our invention, two inorganic membranes sensitive to different chemical species may be deposited in vacuum on the same silicon substrate.
In this technique, a photoresist is first formed on the silicon substrate.
A window is then made in the photoresist for the formation of the first chemical sensitive layer.
The substrate is then dipped in solvent to cause surface expansion of the photoresist and a first sensitive layer is then vacuum deposited on the substrate.
The photoresist is then removed by a resist stripper, leaving bare the surface of the substrate except for the region on which the first sensitive layer was deposited.
A second photoresist layer is then deposited and this layer is exposed and treated to form a window in the photoresist where a second sensitive layer can be formed.
The photoresist is then dipped in solvent to expand its surface and the second sensitive layer is then applied by vacuum deposition.
By treating the resist in a resist stripper, the second sensitive layer can be removed from all portions of the device except that portion that was deposited in the window in the photoresist.
This process can be repeated indefinitely to form still additional sensitive layers on the surface of the substrate.
In a second embodiment of the invention, a PVC film containing valinomycin and a plasticizer is spin-coated on the substrate and is then overcoated with a thin inorganic material.
This inorganic material serves to isolate the organic material from the photoresist that is subsequently used.
A layer of photoresist is then deposited on the inorganic material and a pattern is defined photolithographically in the photoresist above a first region of the substrate