Chemical sensors, in particular silicon-based biosensors

Details Chemical sensors, in particular silicon-based biosensors Chemical sensors, in particular silicon-based biosensors

1997-02-05

1999-02-23

Snay, Jeffrey

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing liquid or solid sample

422 8203, 422204, 422416, G01N 2726

Patent

active

058740473

DESCRIPTION:

BRIEF SUMMARY
SPECIFICATION



CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage of PCT/DE95/01056 filed Aug. 9, 1995 and based, in turn, on German National application P4427921.3 filed Aug. 6, 1994 under the International Convention.


FIELD OF THE INVENTION

The invention relates to chemical sensors, in particular biosensors, which are silicon-based with a sensor-active coating on a semiconductive substrate functioning as a transducer.


BACKGROUND OF THE INVENTION

Chemical sensors and, especially biosensors operating with bioactive components are known and are the subject of vigorous development.
Such sensors basically include a surface layer with a sensor-active material which is exposed to the medium to be tested, especially a liquid. This layer contains the sensor-active material which can be immobilized, for example, in a membrane composed of polyvinylchloride. The signals supplied by the sensor-active material under the effect of an analyte are transformed by a transducer element and are acquired in registrable form by electronic signal processing which can be provided by integrated electronics.
As transducers, particularly semiconductive electrodes, field-effect transistors, potentiometric and amperometric electrodes and the like are considered.
All known sensors have the common characteristic that they generally have insufficient adhesion of the sensor membrane on the respective base element, i.e. the measurement solution can wash it away or penetrate in a detrimental manner directly into the sensor membrane and damage it irreversibly. Connected therewith are stability problems and drift problems with respect to the sensor output signals. Furthermore, there is the need to establish the out-diffusion, i.e. the bleeding or washing out, of sensitive membrane components into the solution. Such sensors, as a consequence have only a limited life. It is also a drawback that the contacts and signal electronics are only separated by a thin passivation layer from the sensitive region and thus the sensor is highly prone to damage.
An attempt to solve this problem is described by Knoll in DE 41 15 414 A1. Here, anisotropic etch pits are incorporated in the substrate material as containments in which the sensor membrane can be anchored. The containments can be jacketed in a nonconductive material and additionally, conductive electrodes can be deposited. These vertical containments comprise openings converging toward the rear side of the chips which are in direct contact with the measurement solution. As a consequence, the above-described drawbacks are overcome. Especially so-called sensor arrays can be realized with this technique with different sensitivities to different substances or ion types.
With this kind of sensor, the containment formation affords a certain protection of the ion selective membrane to limit bleeding out and dissolution. This technology is however only apparently simple in that it can be realized only with expensive lithography techniques.


OBJECT OF THE INVENTION

It is an object of the invention, therefore, to provide a sensor of the initially described type, by which the sensor-active material can be deposited in different forms on a different types of transducer/electronic structures of the sensor with reduced tendency toward damage, with stability enhancement and sensitivity increase.


SUMMARY OF THE INVENTION

This object is achieved with a silicon-based biosensor with a sensor-active coating on a semiconductor substrate effective as a transducer. According to the invention the sensor-active material is received in the pores of a porous layer produced by an etching treatment of the substrate surface and whose opening widths are matched to the penetration characteristics of the sensor-active material. A nonconducting boundary layer can be provided on the pore walls. The boundary layer between the surfaces of the porous material and the sensor-active material of silicon dioxide and/or aluminum oxide, tantalum pentoxide or silicon nitride. The nonconducting boundary

REFERENCES:
patent: 5063164 (1991-11-01), Goldstein
patent: 5111221 (1992-05-01), Fare et al.
patent: 5393401 (1995-02-01), Knoll
patent: 5618493 (1997-04-01), Goldstein et al.

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