JPS6189553A - Integrated enzyme fet - Google Patents

Abstract

PURPOSE:To enable highly sensitive measurement, by forming a reference electrode and at least one kind of integrated enzyme FET on a substrate having a good insulating property. CONSTITUTION:In integrated enzyme FET for measuring an objective substance by the differential measurement of the change in phase boundary potential, for example, reference FET and at least one kind of enzyme FET are formed to a substrate having a good insulating property comprising saphire, tantalum oxide or rubby to eliminate the interference of the enzyme FET and the reference FET. Therefore, the lowering in threshold value voltage is prevented and highly sensitive measurement is enabled.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an integrated enzyme FET (field effect transistor)
It is related to.

(Prior art) Enzyme electrodes, which combine the high specificity of enzymes for substrates and inhibitors with the simplicity and rapidity of electrodes, are widely used in medical and medical applications due to their excellent performance as a means of measuring substances. It has been put into practical use in the chemical industry. Recently, in the fields of clinical testing and bioinstrumentation, enzyme electrodes have been required to be smaller, more sensitive, and more multifunctional. Integrating enzyme I of the present invention
FKT responds to these demands.

As an attempt to miniaturize enzyme electrodes, it is known that a semiconductor sensor is used as a measurement device. for example,
An enzyme FET, which is a combination of an ion-sensitive field effect transistor (FET) and an immobilized enzyme membrane, has been proposed as a semiconductor sensor, and attempts have been made to measure penicillin, urea, acetylcholine, etc. We also have a glucose measurement sensor that combines a Clark-type oxygen electrode and an immobilized enzyme membrane manufactured using silicon anisotropic etching technology, and a urea sensor that combines a palladium-MOSFET (metal oxide PET) and an immobilized enzyme membrane. Measurement sensors have also been proposed. Among these, the enzyme F11iT is attracting attention as a highly practical enzyme for the purpose of miniaturization, high sensitivity, and multifunctionality.

The use of semiconductor stacking technology is being considered as a method for manufacturing multifunctional enzyme PET at low cost. Usually, enzyme FETs have enzymes immobilized on them and FETs on which enzymes are not immobilized.
A method is adopted in which a differential circuit is formed by combining the two, and the target substance is detected. As a result of using this differential circuit, it is possible to automatically compensate for output fluctuations due to temperature changes or degree of closure of the sample solution during measurement.

(Node point to be solved by the invention) JILnata et al.
The penicillin concentration was measured by integrating T and a reference FET and taking the difference in drain current. However, this method is inconvenient because the slope of the closing characteristic does not directly correspond to the slope of the Nernst equation.

On the other hand, it is also conceivable to integrate the enzyme FET and the reference FET on the same substrate and take the difference in interfacial potential changes. In this case, a measurement system in which silicon is used as the substrate and is grounded has the drawback that the slope of the closing characteristic becomes small, resulting in poor sensitivity.

As a result of intensive investigation into the cause of this, the inventors of the present invention found that the cause of the decrease in the slope is due to a change in the threshold voltage◇ (Means for resolving the gap) And the cause was eliminated. In order to achieve this, it is necessary to eliminate the interference between the S-enzyme FET and the reference FET, and as a means for this purpose, we have found a method of using a substrate with good insulation. That is, the present invention is characterized in that an insulating material is used as the substrate in an integrated enzyme FET in which an enzyme FET and a reference FIICT are formed on the same substrate and a target substance is measured by differential measurement of changes in interfacial potential. Integrating enzyme IP1
! :It is T.

In the present invention, an ultra-small and highly sensitive multifunctional enzyme FET is fabricated as an integrated device on the same substrate as the reference electrode, and in a measurement method that takes the difference in interfacial potential changes, at least one By forming a type of enzyme FET on a substrate with good insulation, it has become possible to prevent a decrease in threshold voltage. As a result, the present invention has been completed by achieving the production of a device that is extremely inexpensive and highly uniform in a manner similar to the conventional C circuit production method.

Examples of substrates with good insulation used in the present invention include sapphire, tantalum oxide, and ruby.

Conventional semiconductor integrated processors can be used as they are for producing the integrated composite FET used in the present invention.

Furthermore, known methods can be applied to immobilize dyes, antigens, antibodies, etc. in a membrane.

The number of enzyme FETs integrated on the same substrate is not limited to one, but rather a number of different enzymes depending on the type of substance to be measured. It is preferable to integrate the EiT. Additionally, a standard electrode is used to improve measurement accuracy, and it may be advantageous to form this standard electrode on the same substrate as the enzyme FET and the reference FET.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

Example: A sapphire (Al□0.) substrate was formed with a 0.61 tm silicon roughy. Next, the remaining silicone layer was heated to 450 OA at 1000°C.
A silicon dioxide (S1O2) layer was formed by wet oxidation to a thickness of . The sources and drains were created by diffusing phosphorus into the source and drain parts. The gate part was made into silicon dioxide by wet fermentation (900℃, 1000A), and then hydrogen plasma treatment was performed to activate the activated surface.
Silicon nitride (Si3N4) was grown in D.

Using photolithography, Si and N4 were etched by plasma etching (AY, gas), and S1%2 was etched using fluoride-hydrogen-hydrogen acid to form hole-touch holes. Next, aluminum was vacuum-deposited on the source and drain portions to form electrodes.

The size of the obtained integrated 5FET is chip: 2.5
X2.5mj*channel length=20μm, channel width 2500μm, and three 5FETs were formed on the same chip.

After wiring the fabricated IFEiT and mounting it with silicone rubber,
No4～. /-HP Kochogu\ to 田１翫いμ- し3
N, the surface was chemically modified to introduce amino groups onto the surface. Treatment conditions were 90% ethanol, 5% 1-APTES, 5% water.
% solution for 30 minutes at room temperature. Next, cellulose triacetate 250"F, dichloromethane 10+d, 50% glutaraldehyde aqueous solution 100μ
! , 4-aminomethyl-1,8-octanediamine 50
A uniform solution consisting of 0 μl was dropped onto the gate portion to form an organic film. Phosphate buffer (pH 7, o, 0.0:
After thorough washing with LM), add urease solution (Urease 2600U, 0.01M phosphate buffer, p
A full amount of H-17,O) was added and reacted at 4°C for 10 hours to immobilize urease on the organic membrane.

Among the multiple (3) engineered 5FETs formed on the same substrate as described above, one urease-immobilized XFET and one engineered 5FI with no other enzyme immobilized.
CT (reference FET) was connected as shown in FIG. 1 to assemble a urea measurement system.

The measurement was performed using complex oxygen FIICT-reference IPET of 0.0
Immerse in 1M, 7.0 phosphate buffer solution 1-,
It was carried out by adding urea solutions 1- at various concentrations. The measurement temperature was maintained at 36°C using a constant temperature bath. Urea in the solution was decomposed by urease on the organic membrane surface of the enzyme FET, producing ammonia and causing the solution to rise. Changes in solution S i,N and interfacial potential were measured as the output of the differential circuit. Since the potential of the solution is kept constant by the Ag-190:L electrode, the solution-3i,N resulting from the dilution of the solution by ammonia production (occurs only on the enzyme FET).

The potential change at the interface was proportional to the urea concentration. The interfacial potential changes appearing at the A and B terminals were input to a differential amplifier, and the difference was recorded as a time change on a recorder.

An example of the measurement results is shown in Figure 2. As is clear from FIG. 2, urea can be measured over a urea concentration range of 10-4 g/- to 10-1 g/-. Measurement response time is approximately 3
It was 0 seconds.

(Effects of the Invention) The present invention provides a method for measuring a target substance by differential measurement of interfacial potential changes using an integrated enzyme IPET in which a reference FET and at least one enzyme FET are formed on the same substrate. By using an insulating material as a substrate,
This enables highly sensitive measurements that could not be achieved with the conventional integrated enzyme FF1T using silicone as a substrate.

Furthermore, it has become possible to perform simpler measurements and calculations than conventional differential measurements of drain currents.

The present invention can be applied directly to a normal semiconductor integration process, is suitable for manufacturing a large number of devices at low cost, and can achieve ultra-miniaturization. It is effective for measurements such as

[Brief explanation of the drawing]

FIG. 1 shows a circuit for a urea measurement system using an integrated enzyme FET. FIG. 2 shows the relationship between 0 degrees urea and output voltage. Patent Applicant: Toyobo Co., Ltd. E10 1 Wire ring electrode 2 Washer 1 hard angle 1 PET 3 Reference FE 4 Sha'17) Tank 5 Shiko 71

Claims (1)

[Claims] An integrated enzyme FET in which an enzyme FET and a reference FET are formed on the same substrate and a target substance is measured by differential measurement of changes in interfacial potential, characterized in that an insulating material is used as the substrate.