JPS63243745A - Chemically response semiconductor sensor - Google Patents

Abstract

PURPOSE:To prevent the adsorption of impurities on the interface of laminated films, by forming a semiconductor film, an insulating film and a chemically response film on an electrode in a closed system. CONSTITUTION:Comb-shaped source and drain electrodes 2 and 3 are formed on a glass substrate 1. These electrodes are covered, for example, with a hydrogenated amorphous semiconductor film 4 and a hydrogen-ion-response insulating film 5 of a silicon nitride membrane which are laminated by a glow discharge method. An epoxy resin film 6 is formed on the film 5. Since the films 4, 5 are continuously formed in a closed system by vapor-phase reaction and no photoetching technique is used, no harmful impurity is present on the surfaces of the films. Therefore, it is possible to provide a sensor which is free from decrease in withstand voltage and has a decreased drift of drain current.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a chemically sensitive semiconductor sensor, and more particularly to a field effect type chemically sensitive semiconductor sensor using an amorphous semiconductor.

BACKGROUND OF THE INVENTION In recent years, chemically sensitive sensors that utilize the field effect of semiconductors have been used to detect ions in solutions. Such a sensor utilizes the fact that the conductivity near the semiconductor surface changes in response to changes in the electric field generated at the interface between the semiconductor surface and the solution, and is called an ion-sensitive field effect transistor (hereinafter referred to as rsFET). It is used as an element for measuring chemical components in solutions as an ion sensor or biosensor.

There are 15FETs using single crystal silicon and amorphous silicon, and 15FETs using single crystal silicon.
As shown in Fig. 5, the structure of the FET is to form a pair of source electrodes C and drain electrodes d with a channel layer in between by doping silicon single crystal a with various components, and then to form a pair of source electrodes C and drain electrodes d on the channel layer lbO. Insulator layers e and S
Insulator layers f such as ixNy and TazOs are sequentially provided,
Furthermore, an ion-sensitive membrane g, which is notorious for specific ions, is provided on top of this.

On the other hand, 15FETs using amorphous silicon are manufactured by forming a P-type or non-doped amorphous silicon film on the entire surface of an insulating film substrate made of polyamide or the like using a method such as plasma CVD, as shown in Figure 6. A pattern is formed using the photo-etching technique (a series of steps of photoresist film formation, mask installation, exposure, development, etching or doping, and resist film peeling), and this pattern is applied to an amorphous silicon semiconductor 79i.
shall be.

Next, an n-type amorphous silicon film made of an amorphous silicon film doped with phosphine is formed on the entire surface of the amorphous silicon semiconductor layer, and this is etched using the photoetching technique described above to form the source Nj.
3 After forming the drain Nk, metal is further deposited on the entire surface and the source electrode j is formed using the same photo-etching method as above.
゛, drain electrode k'' is formed. Then, plasma CV
D, Sing film 12 by means of sputtering etc.
, and insulating films of SixNy film m are sequentially formed. This Si
The xNy membrane m can be sensitive to hydrogen ions, and can be further coated with an ion-sensitive membrane n sensitive to other specific chemical components to make it sensitive to the corresponding chemical component.

The rsFET having such a configuration is immersed in a solution, and a voltage is applied between the source electrode and the drain electrode, and a gate voltage is further applied between the comparison electrode provided in the solution, and this gate voltage is applied between the source and drain electrodes. When the voltage is changed, the carrier concentration induced in the channel layer between the source and drain changes, and the current flowing between the source and drain, that is, the drain current changes.

Further, when the concentration of a chemical component in the solution that is sensitive to the ion-sensitive membrane changes while the voltage applied between the reference electrode and the reference electrode is kept constant, the effective gate potential changes and the drain current changes. An 15FET is used as an element that detects the concentration of chemical components in a solution by utilizing such a phenomenon, and is known as an ion sensor or a biosensor. This 15FET can also detect the concentration of specific chemical components such as enzymes and antigens by using an enzyme-immobilized membrane or an organic molecular membrane such as an antibody membrane instead of an ion-sensitive membrane.

Problems to be Solved by the Invention However, in such a sensor, since the interface between the semiconductor layer and the insulating film has a large effect on the electrical characteristics of the sensor, a photoresist film is formed on the semiconductor surface using the etching technique described above. formation, IJ separation and vapor deposition of gold and metal films,
When these layers are peeled off, they will be exposed to the etching solution, and even if this work is done carefully, foreign matter will be adsorbed to the interface between the semiconductor layer and the insulating film formed on it, resulting in contamination. It may be done. In addition, since the work is carried out in the atmosphere, there is also contamination due to oxidation. Due to these causes, interface levels are formed, which not only lowers the withstand voltage of the 15FET in a solution, but also increases the drift of the drain current, resulting in deterioration of electrical characteristics.

An object of the present invention is to provide a chemically sensitive semiconductor sensor that does not have a low withstand voltage when used in a solution and can suppress current drift.

Means for Solving the Problems In order to solve the above problems, the present invention provides at least a pair of conductive electrodes on an insulating substrate, and provides an amorphous semiconductor film on the surface of the conductive electrodes. In a semiconductor sensor having a structure in which a chemically sensitive film is provided on the amorphous semiconductor film via an insulating film or a chemically sensitive film that also serves as an insulating film, the semiconductor film, the insulating film, and the chemically sensitive film are The present invention provides a chemically sensitive semiconductor sensor characterized in that a chemically sensitive film serving as both a film and an insulating film is formed by vapor phase processing of raw material gases that produce each in a closed system.

In the present invention, a source electrode and a drain electrode are formed on a substrate, and examples of this substrate include glass, ceramic, etc., and electrode materials include Cr, Al, and Pt.
, Au, Ag, Ni, and alloys containing these metals as components are used. These metals are formed into a film by conventionally known means such as electron beam evaporation, and the thickness thereof is exemplified as 500 to 1000.

In addition, examples of semiconductor films include amorphous silicon films, including hydrogenated amorphous silicon films,
Examples include a fluorine-doped amorphous silicon film. These include various silane compounds (e.g. SiH4, etc.) mixed with hydrogen, silicon fluoride compounds (e.g. SiF4, etc.)
Claw discharge, plasma CVD of gas mixed with hydrogen, etc.
It can be obtained by vapor phase treatment using conventionally known film forming methods such as CVD, sputtering, and ion blating. The appropriate thickness of these amorphous silicon films is 700 to 2,500.

In addition, the ion-sensitive film can also be used as an insulating film.
This includes, for example, SixNy, SiOxNy, A
Films such as E 201 and TazOs can be mentioned. For example, in the case of SixNy, these can be formed by forming a film by vapor phase treatment using a glow discharge or the like using a mixed gas of 5iHa and N2, and the thickness is 2000 to 4000 people. be done. These react to hydrogen ions, and a 15FET using these can detect the pH in a solution.

Furthermore, by using an 15FET in which a film of the substance shown on the left side below is formed on these films, it is possible to detect the concentration of the corresponding specific chemical component on the right side.

Apply the paint of the substance and let it dry.

The active semiconductor film, the insulating film provided thereon, and the chemically sensitive film are formed in a closed system, that is, by vapor phase processing of the raw material gases that generate them without breaking the reduced pressure or vacuum. Unlike the photo-etching method, the formed film is not peeled off or immersed in an etching solution, so there is no risk of contamination due to adsorption of impurities that adversely affect properties at the interface of the stacked films. This can be avoided.

Embodiment Next, an embodiment of the present invention will be explained based on FIGS. 1 to 3.

Example 1 As shown in FIG. 1(A), a film of Cr (chromium) was formed to a thickness of about 1000 nm on the whole surface of an insulating glass substrate (manufactured by Corning Inc.) 1 by an electron beam thin deposition method.
Next, a comb-shaped source electrode 2 and a drain electrode 3 with a line spacing of 10 crm and a length of 1 fl are formed so as to penetrate into each other by a conventionally used photo-etching technique, and further, these lead lines 2a and 3a are formed. External contact portions 2b and 3b are formed at the ends thereof, respectively.

Next, as shown in FIG.
An amorphous semiconductor film N4 made of a hydrogenated amorphous film having a thickness of 1500 nm is formed by a glow discharge method using a gas containing a mixture of 4 and N2 at a volume ratio of 1:1.

Next, the amorphous semiconductor film layer 4 is overlaid with SiH.
, is used to form an insulating and hydrogen ion sensitive film 5 made of a silicon nitride film with a thickness of 3,000 wafers by a glow discharge method using N2 gas containing 3% by volume of .

As shown in FIG. 1(c), the source electrode 2,
The central part of the drain electrode 3 and the external contact parts 2b, 3b
Apply epoxy resin paint except for and cover with resin film 6,
A sample contact window 7 is formed in the central portion.

In this way, the 15FET 8 is completed, and since it has the hydrogen ion-sensitive membrane 5 which also serves as an insulating film, it is used as a so-called pH-sensitive 15FET that is sensitive to hydrogen ions in a solution. Specifically, as shown in FIG. 3, for example, a reference electrode 11 and the above-obtained 15FET 8 are provided facing each other in a sample solution 10 housed in a water tank 9, and the 15FET 8 is provided with an external contact as shown in FIG. Part 2b, 3
A power supply 12 is connected to b, and a current is passed through the amorphous silicon semiconductor film layer 4, while the reference electrode 11 and the rsF
A power supply 13 is connected to the ET 8 so that a gate voltage can be applied. Note that 14 is a picoammeter.

With such a circuit configuration, when the voltage of the power supply 13 is changed, the drain current flowing through the amorphous semiconductor film layer 4 changes, but at this time, the hydrogen ion concentration of the sample solution, that is, pl+
Since the electric field of the gate voltage is affected by , and there is a correlation between the effective gate voltage and the drain current that take this into account, by keeping the voltage applied from the power supply 13 constant, pt +
A correlation between the current value and the above current value is obtained, and thereby an arbitrary pH of the sample solution can be measured.

At this time, in the 15FET of this example, both the amorphous semiconductor film layer and the insulating film/ion control film formed thereon are formed in a closed system, that is, by a gas phase reaction without breaking the reduced pressure or vacuum, and impurities are removed. is not mixed, the semiconductor properties of the channel layer and the insulating properties of the ion-sensitive film that also serves as an insulating film are well exhibited, the drift of the drain current is suppressed, and the decrease in the withstand voltage of the gate voltage is also suppressed. In order to measure this withstand voltage, in Fig. 3, the sample solution is diluted with phosphate buffer (p!! 6.8), and the voltage of the power supply 13 is V+ =
The current flowing through the picoammeter 14 was measured by setting the voltage v z =O of the power supply 12 to 4 volts. When this current value of 10-S amperes flows, it is determined that the voltage withstand voltage is defective.The number of defective withstand voltages is determined for 100 15FETs obtained in the same manner as above, and the defect rate is shown in the table.

Also, in order to measure the drift of the drain current, v+
= 4 volts, the drain current immediately after setting v2 = 4 volts and the drain current after 1 hour were measured to determine the rate of change, and this was obtained in the same manner as above.
The average rate of change (%) is shown in the table.

Example 2 In Example 1, instead of using hydrogenated amorphous silicon to form an amorphous silicon semiconductor film layer, a gas containing SiF and H2 mixed at a volume ratio of 1:1 was used to form a 1,500-layer film using a glow discharge method. An 15FET was fabricated in the same manner as in Example 1, except that the fluorine-doped amorphous silicon film was used, and the withstand voltage failure rate and drain current change rate were determined in the same manner as in Example 1. The results are shown in the table.

Example 3 The same procedure as in Example 1 was carried out except that a paint was applied to the sample contact core 7 and a coating film containing palinomycin dispersed in polyvinyl chloride resin was formed on the ion-sensitive film 5 that also served as an insulating film. A 15FET was prepared using the same method as in Example 1, and the withstand voltage failure rate and drain current change rate were determined, and the results are shown in the table.

In this example, a potassium-sensitive film sensitive to potassium ions is provided on a hydrogen ion-sensitive film, and the ion-sensitive film that also serves as an insulating film functions only as a thread-colored border film.

Comparative Example An amorphous silicon layer containing hydrogen is formed in the same manner as in Example 1 on a glass substrate similar to that used in Example 1, and a pattern is formed by a conventional photoetching technique as shown in FIG. 6 below. . After forming an amorphous semiconductor film layer doped with phosphine on this layer, a source layer j and a drain layer k are formed using a photo-etching technique, and then metal is deposited on the entire surface and a source electrode j and a drain electrode are formed using a photo-etching technique. Finally, an rsFET was fabricated by forming a SiO Shown below.

Defective rate and drain current change rate are each 2.5% or less,
It can be seen that while it is 4.5% or less, that of the comparative example is two digits and several times larger.

Example 4 In the above case, there was one sample contact window, but as shown in FIG. 4, a plurality of sample contact windows 7a, 7b, 7c, etc. A pH-sensitive membrane as in Example 1, a membrane 5a in which bis-12-crown-4 is further dispersed in polyvinyl chloride is provided in the sample contact window 7b, and a glucose oxidase membrane 5b is provided in the sample contact window 7c. Similarly, membranes sensitive to specific substances may be provided so that pH, sodium ion, glucose, and other specific substance concentrations can be measured. Note that the same reference numerals as those on the map indicate the same components.

Effects of the Invention According to the present invention, semiconductor films, insulating films, and chemically sensitive films are formed by vapor phase reaction in a closed system, that is, without breaking pressure or vacuum. can be formed continuously, without using the conventional photo-notig technique, and the film once formed can be used as it is without peeling, so the finished semiconductor film of, for example, 15FET Impurities are not mixed into the interface with the film provided above or between other films, and it is possible not only to suppress a decrease in withstand voltage but also to suppress the drift of drain current.

This enables stable operation as a sensor such as an ion sensor or biosensor, and enables accurate measurement of specific chemical components of a sample.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are diagrams showing the manufacturing process of an example of a TSFET that is an embodiment of the chemically sensitive semiconductor sensor of the present invention, and FIG. c)I
tn sectional view, FIG. 3 is an explanatory diagram of the usage state of this 15FET, FIG. 4 is a sectional view showing a part of the 15FET of another embodiment corresponding to FIG. 2, and FIG. 5 is a conventional Single crystal l5F
FIG. 6 is a sectional view showing an example of a conventional amorphous 15FET. In the figure, 1 is a glass plate as an insulating substrate, 2 is a source electrode, 3 is a drain electrode, 4 is an amorphous semiconductor film layer,
Reference numeral 5 is a hydrogen ion permeable membrane that also serves as an insulating film, and 5a and 5b are a membrane in which bis-12-crown-4 is dispersed in polyvinyl chloride as a chemically sensitive membrane, and a glucose oxidase membrane, respectively. March 31, 1985

Claims (1)

[Claims] (1) At least one pair of conductive electrodes is provided on an insulating substrate, an amorphous semiconductor film is provided on the surface of the conductive electrode, and chemical sensitivity is applied to the amorphous semiconductor film via the insulating film. In a semiconductor sensor having a structure provided with a film or a chemically sensitive film that also serves as an insulating film, each of the semiconductor film, insulating film, chemically sensitive film, and chemically sensitive film that also serves as an insulating film is produced in a closed system. A chemically sensitive semiconductor sensor characterized in that it is formed by forming a film by vapor phase processing of a raw material gas.