JPS6270749A - Fet sensor and its preparation - Google Patents

Abstract

PURPOSE:To attain to prolong the life of the titled FET sensor, by supporting the responsive substance of the responsive layer of the FET sensor by an inorg. porous body. CONSTITUTION:A responsive layer 5 such as an ion responsive layer, an immobilized enzyme layer, a gas permeable layer, an immobilized bacteria layer, an ion non-resposive layer or an electrolyte layer is arranged on the insulating layer 4 of the gate part of FET to constitute a chemical sensor. At this time, by constituting the responsive layer 3 of a layer wherein a responsive substance is supported by an inorg. porous body, the adhesiveness with the insulating layer 4 is enhanced and the release of the responsive layer 5 is prevented and long life and stable characteristics are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a %FET sensor, and particularly to a FET sensor suitable for stable operation over a long period of time, and a method for manufacturing the same.

[Technical background of the invention and its problems]

A chemical sensor using a field effect transistor (hereinafter abbreviated as FET), that is, a FET chemical sensor, was introduced in 1970 by J.
Many studies have been conducted since the proposal by Anata et al.

For example, as an ion-sensitive layer for an F'ET chemical sensor, a layer with good selectivity can be created by applying a layer-wide casting method in which ions and sensitive substances are dispersed together with a plasticizer in a polyvinyl chloride matrix. However, FET
The disadvantage is that the adhesion between the insulating film and the ion-sensitive layer is poor, making it difficult to withstand long-term use (a, D, Mo5s, J
, Janata C, C, Johnson, Anal
, Chem, , 47, 2238-2243 (19
75) ZP, T, Mc Br1de et al.
Anal, Chem, Acta,,l Ql, 2
39-245 (1978), U.Oesch, S.C.
aras and J, Janata.

Anal, Chcm, 11, 1938-1986.
(1981)).

In addition, enzymes or microorganisms are used as sensitive substances in FET chemical sensors, and these are immobilized and a fixed enzyme layer or immobilized microorganism layer is installed on the gate surface to detect substances that the enzymes or microorganisms specifically react to. do. In so-called biosensors, bovine serum albumin is used for the immobilization layer.

In this case as well, the immobilization layer will peel off from the insulating film if used for a long period of time.

FET like this? Poor adhesion between R@ and the sensitive layer.

This is thought to be because water needs to penetrate into the sensitive layer to some extent, and swelling of the layer is unavoidable as a result.

[Object of the Invention] The present invention aims to improve the above-mentioned drawbacks and provide an FET sensor having a long life and stable characteristics.

[Summary of the invention]

The first invention provides an FET sensor comprising a sensitive layer such as an ion sensitive layer, an immobilized enzyme layer, an immobilized microorganism layer, an electrolyte layer, etc. on an insulating layer of a gate portion of a field effect transistor. This is an FET sensor characterized in that a sensitive substance is supported on an inorganic porous body.

In other words, the ion-sensitive layer that is directly connected to the insulating film of the FET,
As a sensitive layer such as an immobilized enzyme layer, an immobilized microorganism layer, or an electrolyte retention layer, by using a layer in which a sensitive substance is supported on an inorganic porous material, it is possible to achieve a long life with improved adhesion with an insulating film. It is a FET chemical sensor with all stable characteristics.

The inorganic porous material in the present invention may be any non-organic material as long as it has porosity, and is not particularly limited, but preferably porous glass,
and porous ceramics such as Azgo3. TiO2,
5i02-At203. ZrO2 is mentioned, especially 8i0
2 and ht2o3 are optimal.

Furthermore, an FET chemical sensor with excellent alkali resistance can be produced by adding Zr to 5i02 or coating it with Z r O2.

The sensitive substances in the sensitive layer include glucose oxidase (for glucose) and urease (for urea).

Enzymes such as enzymes for penicillin (for penicillin), microorganisms such as butyric acid bacteria (for butyric acid), lactic acid bacteria (for lactic acid), and any enzyme that causes a change in state that can be detected by basena may be used.

Among the sensitive substances mentioned above, palinomycin.

An ion-sensitive layer is created by supporting an ion-sensitive substance such as methyltridodecylammonium salt on an inorganic porous material.
An immobilized enzyme layer can be formed by supporting an enzyme, an immobilized microorganism layer can be formed by supporting a microorganism, or an electrolyte layer can be formed by supporting a % electrolyte solution or an electrolyte gel.

Please note that these sensitive substances may be dispersed in a layer containing an inorganic porous material by a method such as adsorption, or may be dibonded by chemical bonds such as silane coupling, azo bonds, etc., or may be bonded by chemical bonds. in case of.

-S It is possible to have a long life.

The second invention is an invention of a method for forming an FET chemical sensor on a layer containing porous glass of any composition or porous ceramics of any composition as an inorganic porous body using a thermal decomposition method of organic raw materials. .

First, the metal alcoholate solution is immersed using the dipping method.

The dipping method is most often used as a single layer forming method for forming a layer of metal alcoholate on the insulating layer of the digate portion by spin casting or the like, and the layer can be formed over a wide area. In this method, the material to be coated is pulled up from the entire solution to form a layer.

Metal alcoholates are easily hydrolyzed and converted into gel-like oxides. The process in which a single metal alcoholate repeatedly undergoes hydrolysis and double polymerization to become an oxide is expressed as follows.

M(OR) x+H20→ M(OH)(OR)x
1+ROMM(OH)(OR)x-t+M(C1su,
→(OIt)x-1・M・0・lν1(OR), <-!
-Jubon OH → M, O□Jukan OH By heat-treating the obtained gelled oxide lΔ, a p-inorganic porous layer is formed. A ion-sensitive layer is created by adsorbing or chemically bonding a sensitive substance to this layer.

An immobilized enzyme layer, an immobilized microorganism layer, or an electrolyte layer is formed.

Furthermore, by utilizing the phase separation phenomenon of glass, the F according to the present invention
Porous glass can also be formed as the inorganic porous body of the ET chemical sensor.

For example, a solution is prepared by mixing two or more metal alcoholates with different acid resistance or alkali resistance when converted into oxides in an appropriate ratio. This solution can be applied by immersion method, descent method,
A layer of m K metal alcoholate is formed on the insulating layer surface of the sensor gate portion by a spray method, a spin casting method, or the like. The metal alkolate is hydrolyzed and turns into a gel-like oxide. This gel-like oxide layer becomes a glass layer by heat treatment.
When heated at a temperature of about 0°C, a phase-separated glass layer with two phases is formed. This phase-separated glass layer has a structure in which two or more types of phases with different resistances to acids or alkalis are intertwined as a network. When immersed in a strong alkaline solution such as potassium hydroxide, the parts that are easily soluble in acids or alkalis will dissolve.
Some parts that are resistant to acids or alkalis remain. The result is a porous glass layer with countless continuous pores.

[Embodiments of the invention]

The following five embodiments of the present invention include a Si-prepared probe type ion-sensitive field effect transistor (ISFET) according to the present invention;
We will explain the case where it is implemented using . In this example, the entire layer containing 8i02 glass porous material as the inorganic porous material was manufactured by the method of the invention of Kintetsu 2.

(Example 1) Fig. 1 is a plan view showing a gate portion at the tip of a glove of a FET chemical centimeter according to the present invention, and Fig. 2 is a plan view showing a gate portion at the tip of a glove of an FET chemical centimeter according to the present invention, in which an insulating layer, a sensitive layer, etc. are provided in the gate portion. FIG. 2 is a cross-sectional view of a FET chemical sensor. A drain 1 is formed by completely diffusing impurities into a silicon substrate 6, an oxide layer 3 made of 2*8sO2, and an insulating layer 4 made of 5i3N4 are formed.

The insulating layer was formed using silicon tetraethoxide (
Sakur (OC2H5)4. ) The gate part of the sensor is immersed in the solution to form a metal alcoholate layer on the surface.

By hydrolyzing and polymerizing this layer, gel-like 5i02
It becomes a film. Furthermore, water and organic components were removed by heat-treating this at 500°C.

A porous Si02 layer in an amorphous state as an inorganic porous body is obtained. The layer thus obtained was treated with γ-aminopropylethoxysilane to give -8i-0-8i
It was made into an alkylamino glass derivative having - bond. Next, this was converted into an allylamino-glass derivative, and after further diazotization, glucose oxidase was added as a sensitive substance through an azo bond.

It was bonded to an inorganic porous body.

When the glucose concentration of an aqueous solution was measured using this sensor, a sufficiently stable output was obtained as shown in FIG.

In contrast, in the case of the above-mentioned Example 1, stable characteristics as shown in curve A in FIG. In the conventional case, it was confirmed that the output decreased rapidly as shown by curve B.

〔Effect of the invention〕

As explained above, according to the present invention, when configuring the ion-sensitive layer and the immobilized enzyme on the insulating layer of the gate part of the FET,
It is extremely effective in preventing peeling of the sensitive layer and can significantly extend its service life.

[Brief explanation of drawings]

FIG. 1 is a plan view of a gate portion according to an embodiment of the present invention, and FIG. 2 is a sectional view of the FET chemical sensor according to the present invention. FIG. 3 is a diagram explaining the present invention in detail. 1...Dray/2...Source 4...Insulating layer 5...Sensitive layer

Claims (5)

[Claims] (1) An FET sensor comprising an insulating layer of a gate portion of a field effect transistor, characterized in that the sensitive layer includes a layer in which a sensitive substance is supported on an inorganic porous body. (2) The FET sensor according to claim 1, wherein the sensitive layer is selected from at least one of an ion sensitive layer, an immobilized enzyme layer, an immobilized microorganism layer, and an electrolyte layer. (3) The FET according to claim 1, which uses porous glass or porous ceramics as the inorganic porous body.
sensor. (4) The FET sensor according to claim 1, wherein SiO_2 is used as the inorganic porous material. (5) A FET characterized in that a metal alcoholate layer is provided on the insulating layer of the gate portion of the field effect transistor, and a sensitive material is supported on the inorganic porous layer obtained by heat-treating the layer to form a sensitive layer. How to manufacture the sensor.