JPH02223855A - Ion sensor - Google Patents

Abstract

PURPOSE:To improve insulation sealability and workability by fixing a sensor chip and a leader electrode substrate by interlayer insulating layers in the directions where the respective leader electrodes of the chip and the substrate face each other and connecting the same by anisotropic conductive resins in the apertures provided to the interlayer insulating layers. CONSTITUTION:The sensor chip 1 is formed with the plural leader electrodes 3 of two pieces of ion sensitive electric field effect transistors (ISFET) 2 by using a silicon on sapphire substrate and with an insulating protective film 4 covering the parts thereof exclusive of the front end part by a semiconductor integrating technique. One FET of the ISFET 2 is provided with an oxidation- fixed film 5 and the other FET is provided with a reference film 6 consisting of a deactivated oxygen film. The leader electrode substrate 7 has the plural leader electrodes 8 which correspond, one to one, to the electrodes 3 and the surface thereof exclusive of the front end part is coated with the insulating film 9. The sensor chip 1 and the leader electrode substrate 7 are provided with the interlayer insulating layers 10 having the apertures 11 to surround the electrodes 3, 8. The anisotropic conductive resins 12 are embedded in the apertures 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion sensor using an ion-sensitive field effect transistor, and particularly to its assembly structure.

[Conventional technology]

A glass electrode type ion sensor is a method for measuring ion concentration in a solution. It uses the fact that the potential difference between the solution and the glass electrode changes depending on the ion concentration, and measures the ion concentration from the voltage change measured with a high input impedance voltmeter. I'm looking for it. Instead of this glass electrode type ion sensor, Yuji Miyahara et al.
A biosensor described in the paper "Biosensor J Using Semiconductor Technology", published in 1981, page 61, has been developed. This is an 15FET ion sensor that uses a fixed ion-sensitive field effect transistor (hereinafter referred to as 15FET) to cause the voltage generated between the 15FET and a solution to act as a gate voltage, and detects the ion concentration from changes in the current flowing through the 15FET. .

This 15FET ion sensor has a fast response speed, so it can measure the ion concentration of a solution in real time and continuously.
Semiconductor integration technology allows for easy mass production, resulting in low cost, and its small size makes it easy to store and handle.

Conventionally, the structure of the 15FET ion sensor developed by the present inventors is composed of a source, drain, and gate insulating film using, for example, an SO3 (silicon on sapphire) substrate, as shown in FIG. two independent l's
The sensor chip 1, in which the enzyme immobilized membrane 5 is immobilized on one 1SFET 21 of the 5FET, and the reference membrane 6 is immobilized on the other 15FET 22 by an inactivated enzyme membrane, is mounted, for example, on a flexible For example, a room temperature curing epoxy adhesive 6 is applied to the tip of a lead electrode board made of a printed circuit board (hereinafter referred to as an FPC board).
1, and after connecting the sensor chip 1 and the lead electrodes 3 and 8 of the lead electrode substrate 7 with a bonding wire 62, the area around the connection part is insulated and sealed with, for example, an epoxy adhesive 63 that hardens at room temperature. It has stopped. Enzyme immobilization membrane 5
The l5FET 21 on which the reference membrane 6 is immobilized detects the ion concentration of the measurement solution, and the TSFET 22 on which the reference membrane 6 is immobilized does not react with the measurement solution, but by measuring the output difference between the two l5FETs, it is possible to detect the ion concentration due to temperature changes etc. Drifters are canceled out and stable measurements are possible.

[Problem to be solved by the invention]

Since the conventional 15FET ion sensor as described above is used in a solution, it is required to have an insulating seal with excellent water resistance. Therefore, in this assembly, it is especially important to insulate and seal the area around the connection between the sensor chip and the extraction electrode of the lead electrode board.Furthermore, since we are dealing with a device that already has an enzyme membrane attached, we need to use adhesives and insulating sealing materials. The selection and working conditions are limited. In general, enzyme membranes are sensitive to temperature, and lose their functionality if exposed to temperatures of 60°C for about 10 minutes. Conventionally, epoxy adhesives that harden at room temperature have been used as adhesives and insulating sealing materials. agent is used.

This adhesive may not have sufficient adhesive strength and leak into the solution, causing it to not work.Also, such adhesives have a high viscosity and may deform the bonding wire during the sealing process, causing wire breakage or short circuits between wires. It had the drawback of becoming defective.

An object of the present invention is to solve such problems and provide an ion sensor that has excellent insulation sealing properties, is easy to assemble, and is inexpensive to manufacture.

[Means to solve the problem]

The configuration of the ion sensor according to the present invention is such that a sensor chip including an ion-sensitive field effect transistor having at least an enzyme-immobilized membrane and a lead electrode substrate are arranged such that the lead electrodes of the sensor chip and the lead electrode substrate face each other. The electrodes are fixed by an interlayer insulating layer in the same direction, and the extraction electrodes are connected to each other by an anisotropic conductive resin at an opening provided in the interlayer insulating layer.

[Effect]

By adopting the configuration of the present invention, the periphery of the electrical connection between the sensor chip and the lead electrode substrate is completely surrounded by the interlayer insulating layer, achieving good insulation sealing. Also,
In its production, the formation of the interlayer insulating layer can be carried out separately from the immobilization of the enzyme immobilization film, so there is no temperature limit, so it is possible to select and use insulating materials with excellent insulation and adhesion. can. Furthermore, the interlayer insulating films of the sensor chip and lead electrode substrate, and the anisotropic conductive resin for electrical connection can all be welded simultaneously by ultrasonic welding, simplifying the assembly process and achieving low costs. Ru. Since this ultrasonic welding can be carried out in a short time of several milliseconds, there is no effect on the deterioration of the enzyme membrane due to temperature rise during welding.

〔Example〕

The present invention will be explained below based on the drawings.

FIG. 1 is a schematic perspective view illustrating an embodiment of the ion sensor of the present invention. In the figure, 1 is the sensor chip and S
Using an O8 substrate, a plurality of lead-out electrodes 3 drawn out from both the source and drain electrodes of two 15FET2 consisting of a source electrode, a drain electrode, and a gate insulating film (not shown), and insulation protection covering the parts other than their tips are provided. The film 4 is formed by semiconductor integration technology. 2 l5FETs
One I5FET 21 of 2 has an enzyme immobilized membrane 5, and the other I5FET 22 has a reference membrane 6 made of an inactivated enzyme membrane.
is formed. Reference numeral 7 denotes a lead electrode substrate made of, for example, an FPC board, which has a plurality of lead electrodes 8 in one-to-one correspondence with the lead electrodes 3 of the 15FET, and its surface except for its tip is covered with an insulating film 9 made of polyimide film. Although not shown, the extended end of the lead electrode board 7 is processed into a card connector shape. An interlayer insulating layer 10 made of, for example, polyimide resin and having an opening 11 is provided on the sensor chip 1 and the lead electrode substrate 7 so as to surround the plurality of lead-out electrodes 3 and 8 at the tip thereof. This opening 11 is filled with an anisotropic conductive resin 12 containing, for example, Ni particles, and is electrically connected to a plurality of extraction electrodes 3.8.

2 to 5 are perspective views for explaining the manufacturing method of the embodiment shown in FIG. 1. FIG.

FIG. 2 is a perspective view showing a state in which an interlayer insulating layer is formed on the wafer on which the 15FET is formed in the first step.

The 15FET is manufactured by etching an island-like silicon layer using semiconductor integration technology on a 2-inch diameter SO8 substrate 20 on which non-doped silicon is epitaxially grown to a thickness of 0.6 μm on a 350 μm thick sapphire. , dope with borium by ion implantation to form a p layer, further dope with phosphorus to form an n+ source region and train region, then form a silicon oxide layer with a thickness of 100 OA by thermal oxidation, and then cover the entire surface. A silicon nitride layer is formed to a thickness of about 100 OA using the CVD method. This I 5F
Leading electrodes 3 are drawn out from the source and drain regions of ET2, which are formed by, for example, vapor-depositing aluminum and photo-etching.

A wafer on which a plurality of 15FETs are formed is first coated with an insulating resin (for example, DuPont's P I 255
5 polyimide resin) was applied to the entire surface of the wafer by spin coating, and prebaked at 150°C for 30 minutes to a thickness of approximately 10%.
An interlayer insulating layer 10 having a thickness of .mu.m is formed, and an open pattern is formed using photoresist in a portion of the interlayer insulating film corresponding to the extraction electrode, and an opening 11 is formed by a commonly used dry etching method.

FIG. 3 shows a state in which an enzyme-immobilized film 5 and a reference film 6 are formed on each 15FET in the wafer after the first step is completed in the second step. Here, a protein solution containing an enzyme and a crosslinking agent is formed. As an example, a case where urea is detected will be described. First, a photoresist (for example, Shipley AZI450J) was applied by spin coating, and after drying at 60°C,
The photoresist of the 15FET portion where the reference film is provided is removed by exposure and development using a photomask. Next, 0.2 mol containing 15% bovine serum albumin without enzymes,
500 μη of Tris-HCl buffer with pH 8.5 and 0.7
After stirring and mixing the wafer with 500 μi of a 5% glutaraldehyde aqueous solution, the wafer was immersed in an acetone solution to dissolve the photoresist film, and the immobilization film coated on the photoresist was removed to create a reference 15FET. is formed. Next, the photoresist process similar to the above was repeated again to remove the photoresist from the 15FET section where the enzyme immobilization membrane was provided, and then
．． 2M PH8.5 Tris-HCl buffer 250 μj
to 100 mg/dρ prepared with the same buffer.
Urea "ze" (manufactured by Boehringer Mannheim, approx. 50
Add 250 μρ of solution (U/m g), 0.75
%0 glutaraldehyde aqueous solution with 500 µl of aqueous solution was spin-coated, left to dry at room temperature for 30 minutes, the wafer was immersed in an acetone solution to dissolve the photoresist film, and the solution was coated on the photoresist. By removing the immobilized membrane, a 15FET with an immobilized enzyme membrane is formed.

In this example, the case of detecting urea was exemplified, but it is possible to use various enzyme-immobilized membranes in this Jima-like method. Although the enzyme-immobilized film had good adhesion to the silicon nitride film in this example, it is also possible to perform primer treatment before applying the enzyme-immobilized film to further improve the adhesion. be. By cutting and scribing the wafer after the above-mentioned steps with a dicing saw, a single sensor chip 1 is obtained.

The chip size obtained in this example was 0.6 mm in width and 4 mm in length.

FIG. 4 is a diagram showing a lead electrode substrate created in the third step. 6 For example, using an FPC board based on polyimide resin, a predetermined lead-out electrode 8 and an insulating film 9 are formed on the portion excluding the tip thereof. An insulating resin (for example, PI25 manufactured by DuPont) is applied to the lead voltage board 7 on which the
55 polyimide resin) was applied to the entire surface of the lead electrode substrate by spin coating, and prebaked at 150° C. for 30 minutes to form an interlayer insulating layer 10 with a thickness of approximately 10 μm. Then, an open pattern is provided using photoresist, and an opening 11 is formed by a commonly used dry etching method. This process is
Although it is possible to process individual lead electrode substrates, for mass production and uniformity of finish, it is better to perform the above processing on a sheet containing multiple pieces and then cut them individually after completion of the process. is good. FIG. 5 is a diagram showing the fourth step, and shows the state in which the sensor chip 1 and the lead electrode substrate 7, each having an interlayer insulating film and an opening 11 formed therein, are ultrasonically welded. The openings 11 of the sensor chip 1 and the lead electrode substrate 7 are stacked so as to face each other, and placed on a metal mount 50 with the sensor chip 1 facing down, and the openings 11 of the sensor chip 1 and the lead electrode substrate 7 are slightly smaller than the openings. The anisotropic conductive resin 12 is put into the opening 11, and the ultrasonic oscillator 52 is operated while pressing the ultrasonic horn 51 from above to separate the interlayer insulating film 10 of the sensor chip 1 and the lead electrode substrate 7, and the extraction electrode 3. 8 with anisotropic conductive resin 12
to be welded through.

In this example, an ultrasonic oscillator 52 with an oscillation frequency of 28 KHz and an output of 150 W was used, and transverse vibration with an amplitude of 10 μm was applied for 1 second while pressing the ultrasonic horn 51.

When the ion sensor assembled as described above was placed in a 0.9% sodium chloride aqueous solution and the leakage current between the lead electrode of the lead electrode substrate and the aqueous solution was examined, no leakage that would pose a functional problem was found.

〔Effect of the invention〕

As detailed above, in the ion sensor according to the present invention, the area around the electrical connection between the sensor chip and the lead electrode substrate is surrounded by an interlayer insulating layer made of a material with excellent insulation properties, so that complete insulation sealing is achieved. In addition, the insulating seal and the electrical connection using the anisotropic conductive resin can be assembled simultaneously by ultrasonic welding and in a short time, making it possible to realize low manufacturing costs.

Interlayer insulating film, 11... Opening, 12... Anisotropic conductive resin, 50... Mounting table, 51... Ultrasonic horn, 5
2... Ultrasonic oscillator, 61.63... Adhesive, 62
...bonding wire.

Claims (1)

[Claims] A sensor chip including at least an ion-sensitive field effect transistor equipped with an enzyme-immobilized membrane and a lead electrode substrate,
The extraction electrodes of each of the sensor chip and the lead electrode board are fixed by an interlayer insulating layer so as to face each other, and the extraction electrodes are connected to each other by an anisotropic conductive resin at an opening provided in the interlayer insulating layer. An ion sensor characterized by: