JPS58111751A - Ph measuring electrode apparatus - Google Patents

Abstract

PURPOSE:To obtain a small uniform apparatus with a high measuring accuracy by forming a pH electrode with a Ta2O5 film serving as a sensitive section and a Ta2O5 electrode for correcting errors of the pH electrode due to a photovoltaic effect separately on a semiconductor substrate while a waterproof and insulating transparent cover is applied on the entire surface except for the pH detecting surface. CONSTITUTION:A channel stopper 12 is formed entirely widthwise in the center of the surface of a P type Si substrate 2 (possibly N type) by diffusing B and separate Ta2O5 films 3 and 4 are provided on the top thereof at the right and left of the stopper by vacuum evaporation or the like. An electrode 5 is made of Ni, Au or the like at the rim of the film 4 and connected with a conductor 6. Electrodes 7 and 8 are made of Rh, Al or the like separately at right and left parts of the back of the substrate 2 and connected with respective conductors 9 and 11. Then, a waterproof and insulating transparent cover 14 made of polyethylene or the like is formad on the entire surface of the substrate leaving the pH detection surface 13 on the left part thereof and the right electrode is used as correction electrode 10. The pH electrode 1 thus obtained is put into a liquid to be inspected in a measuring cell to be emmersed thereinto with the comparison electrode so that errors due to the photovaltaic effect of light infiltrating from the perimeter is removed wit the electrode 10 eliminating an internal liquid or the like in the pH measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring electrode device for measuring the voice value of a test liquid.

Conventionally, a glass electrode has been used as the electrode in a PH measuring device that measures voice value using an electrode. This glass electrode has a thin glass electrode sphere made of sensitive glass that is sensitive to hydrogen ions, and inside this glass electrode is placed an internal liquid with a known value and a silver-silver chloride electrode as a non-polarizable electrode. It is something.

However, since this conventional glass electrode is made of glass,
It has the disadvantage of being easily damaged. Furthermore, since it is difficult to make the thickness of the glass electrode bulb constant, variations occur from product to product. Furthermore, for example, if the thickness of the glass film becomes too thick, the predetermined potential may not correspond to the actual voice value. Furthermore, since an internal liquid is required, it is difficult to miniaturize the product, and the liquid also needs to be replenished, making maintenance management troublesome.

Furthermore, since an internal liquid is used, there are also drawbacks such as the orientation of the liquid when used is specified.

The present invention has been made in view of the above circumstances, and its object is to provide a PH measuring electrode device in which a tantalum pentoxide film is formed on a semiconductor substrate and used as a PH electrode.

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 6.

FIG. 1 shows one electrode 1 in the pH measuring electrode device. This pH electrode 1 has Ta205 films 3 and 4 on the upper surface of each left and right portion of a P-type silicon substrate 2 as a semiconductor substrate.
form. These Ta205 films 3 and 4 are formed by vacuum evaporation, sputtering, CVD (Chemical Vapor
110 using film technology such as r Deposition) method.
It is formed to have a thickness of about 0 nm. As shown in FIG. 2, the edge of the Ta205 film 4 on the right side is coated with Ni.

An electrode 5 made of Au, Au-Ag alloy, etc. is attached. This electrode 5 is attached by, for example, chemical plating, electroplating, vapor deposition, or the like.

Further, a conductive wire 6 for outputting to the outside is connected to the electrode 5 by a method such as soldering.

Further, as shown in FIG. 3, Rh and At are applied to the left and right portions of the back surface of the Pt electrode substrate 1, respectively.

N1. Electrodes 7, 8 made of Au-Ag alloy or the like are attached in the same manner as described above, and conductive wires 9, 11 are connected to each electrode 7, 8 by a method such as soldering.

Furthermore, the P-type silicon substrate 2 is coated with zolon (B) in a portion that traverses the entire width of the intermediate portion equally divided into left and right halves.
The channel stopper 12 is formed by diffusing the
This prevents electrical continuity between the stain electrodes 7 and 8.

As shown in FIG. 2, this twisted voice electrode 1 is made of a transparent coating 14 that is waterproof and insulating, except for the central part of the surface of the left side of the P-type silicon substrate 2, which is covered with a waterproof and insulating transparent coating 14. covered by.

This transparent coating is made of polystyrene, for example. Thus, the pH electrode 1 constitutes the correction electrode 10 on the right side of the P-type silicon substrate 2. Note that the detection surface 13 of the PH electrode 1 may be covered with a protective film made of a transparent hydrophilic semipermeable film.

The electrode 1 thus constructed is connected to the amplifier 18 at 6.11 shown in FIG. 4, and the conductor 9 on the P)It electrode side and the comparison electrode 17 are connected to another amplifier 19. Each output terminal of each of the amplifiers 18 and 19 is connected to a differential amplifier 20.

Therefore, when the test liquid 16 is supplied to the measurement cell 15 and brought into contact with one electrode 1 and the comparison electrode 17, there is a gap between the Ta205 film 3 of the negative electrode 1 and the comparison electrode 17. As shown in FIG. 7, a potential corresponding to the voice value of the test liquid 16 is generated.

At this time, since the - electrode 1 is entirely covered with a transparent film 14 except for the detection surface 13, the Ta20 corresponding to the detection surface 13 contacts the test liquid 16 and becomes sensitive.
5 membrane 3 only. However, the other Ta205 film 4 is more sensitive to the u+yc of the test liquid 16 and does not generate a potential.

At the same time, the P-type silicon substrate 2 and each Ta205
A photovoltaic force is generated between the films 3 and 4 by light incident from the surroundings, and a potential is generated as shown in FIG. Therefore, the electric potential Et generated between the comparison electrode 17 and the Ta205 film 3 on the left side becomes 5-Et''Et+Ep. E is the potential difference between the Ta205 film 3 and the left side (pH electrode 1) due to the photovoltaic force.
This is the potential difference between the Ta205 film 3 and the P-type silicon substrate 2. The potential difference Ep due to the photovoltaic force is included as an error.

Furthermore, since the Ta205 film 4 on the right side (correction electrode 10) does not come into contact with the test liquid 16, only a potential difference Ep' due to photovoltaic force appears between the Ta205 film 4 and the P-type silicon substrate 2. This E, / is approximately equal to the above E. Therefore, by taking the difference between this potential difference E, / and the potential difference Et as shown in the following formula, the desired potential difference E1 can be obtained.

Ei =li:t-Ep Et-E,' This can be obtained as the output of the differential amplifier 20 of the electric circuit described above. Note that the amplifier 18 has a potential difference Ep'
, the amplifier 19 amplifies the potential difference Et, and the respective keys are adjusted so that l Ep Ep 'l = n+i n6-.

By the way, if we have obtained the potential difference E1 due to H+ ions in the test solution, we can further calculate the potential difference E2 due to the test solution with a known H ion concentration C2 using the Nernst O equation: R: gas constant, T: absolute temperature, F: Faraday constant. The H ion concentration C of the test liquid is H ion concentration C, and the H ion concentration C becomes H=-1ogc1.

In the above embodiment, P is formed on a single P-type silicon substrate 2.
I (At the same time as the Ta205 film 3 for measurement was formed, the Ta203 for photovoltaic force correction was formed to be 4', and the -electrode 1 of 1 and the correction electrode 1.0 were combined into one chip. However, the present invention is not limited to this, and the step 21 of the voice electrode 1 and the step 22 of the photovoltaic force correction electrode may be separated and each configured in the same manner as described above. 7 to 9 show the tip 2) of the fitted electrode 1, and FIGS. 10 to 12 show the Tera f22 of the photovoltaic force correction electrode. each chip 21
．． 22 is separately immersed in the test liquid 16 of the measurement cell 15, as shown in FIG. However, the tip 22 of the photovoltaic force correction electrode does not necessarily need to be brought into contact with the test liquid 16.

Further, the semiconductor substrate in the present invention is not limited to the P-type silicon substrate 2 as in the above embodiment, but may be other P-type substrates (
For example, it may be a GaAs (GaAs) or N-type substrate.

As explained above, the present invention uses a Ta2O film formed on a semiconductor substrate by sputtering, etc. as a PH electrode.
Efforts will be made to improve the i-1t's size, make it smaller, make the product more uniform, and strengthen the membrane. In addition, conventional single electrodes require an internal solution, but when using this electrode, no internal solution is required, and repairs can be made by simply calibrating with a sample solution of a known voice value before measurement. It's easy. Further TIL 20
By providing a correction electrode for correcting the photovoltaic force generated in the S film and by making the product uniform, the measurement accuracy can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of one electrode in an embodiment of the present invention, FIG. 2 is a front view of the voice electrode, FIG. 3 is a back view of the same electrode, and FIG. 4 is a back view of the same electrode. A schematic configuration diagram of the voice measuring electrode device used, FIG. 5 is a diagram showing the relationship between electrode potential and ion concentration, FIG. 6 is a diagram also showing the relationship between photovoltaic force and illuminance, and FIG. is a perspective view of a chip for measurement in another embodiment of the present invention, FIG. 8 is a front view of the chip, FIG. 9 is a back view of the chip, and FIG. 10 is a chip for photovoltaic force correction. FIG. 11 is a front view of the chip, FIG. 12 is a back view of the chip, and FIG. 13 is a schematic diagram of a pH measuring electrode device using each of the above chips. be. 1...PH electrode, 2...P-type silicon substrate, 3...
・Ta205 film (left), 4'' Ta205 film (right)
, 10... Correction electrode, 13... Sensing surface, 14
... Transparent film, 16... Test liquid, 17... Reference electrode, 21... Tip, 22... Chip. Applicant's agent Patent attorney Takehiko Suzue ``l'' Figure 2 Figure 3 Figure 6

Claims (1)

[Claims] (1) A tantalum pentoxide film is formed on a semiconductor substrate, and this tantalum pentoxide film is used as a hydrogen ion sensitive part. A patent claim characterized in that an integrated substrate is provided with a tantalum pentoxide film formed on a semiconductor substrate and a correction electrode entirely covered with a waterproof and insulating transparent film. PI″I measurement electrode device according to scope 1.