FET electrode with carbon gate

Details FET electrode with carbon gate FET electrode with carbon gate

1991-04-19

1991-10-29

Mintel, William

Chemistry: electrical and wave energy

Apparatus

Coating, forming or etching by sputtering

357 2315, 357 8, 204418, 204416, H01L 2966

Patent

active

050619764

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a FET electrode and, more particularly, to an ion-sensitive FET electrode.


BACKGROUND ART

FET electrodes, long known in the art, utilize the principle of a field-effect transistor (FET). With regard to the structure and operation of a FET electrode, an impurity is diffused in a p-type substrate, which comprises a substrate of a metal oxide/semiconductor insulative membrane (p-type SiO.sub.2 /Si.sub.3 N.sub.4), on the gate portion thereof, thereby forming an n-type source and a drain electrode. When a positive voltage is applied to the electrode at the gate portion, the potential of the p-type semiconductor in the vicinity of a redox membrane drops to induce electrons within the p-type semiconductor. A layer of these electrons forms a channel along which electrons flow from the source to the drain to produce a drain current. The amount of this drain current is controlled by the gate voltage. Since the voltage at the gate is proportional to the H.sup.+ ion activity, the FET electrode can be used as a pH-MOSFET
However, a FET electrode of this type responds to light, besides exhibiting a large amount of drift and poor stability.


DISCLOSURE OF THE INVENTION

An object of the present invention is to solve the foregoing problems of the prior art and provide a FET electrode exhibiting little drift, high stability and little response to light.
As means for solving the foregoing problems, the FET electrode of the present invention comprises a FET, a carbon thin membrane coating a gate insulator of the FET, and an organic thin membrane coating the carbon thin membrane.
In the arrangement of the invention, the FET measures the concentration of H.sup.+ ion based on a potential, which corresponds to the activity of the H.sup.+ ion, produced on the gate portion by the organic thin membrane. Meanwhile, the carbon thin membrane reduces drift, stabilizes the adhesion between the gate insulator of the FET and the organic thin membrane and shuts out light.
Thus, in accordance with the invention, there is provided a FET electrode exhibiting little drift, high stability and little response to light.
Moreover, since the membrane covering the gate produces a potential which corresponds to the H.sup.+ ion, there can be provided a FET electrode which operates on the principle of the field effect, namely a FET electrode having the following structural arrangement, which is characteristic of the field effect: amplifying action of the device, the output resistance of the electrode can be kept to a low several thousand kilohms and electrical disturbances can be reduced.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating an integrated-type FET electrode of the present embodiment;
FIG. 2 is a view for describing an apparatus for measuring the FET electrode of the present embodiment;
FIG. 3 is a view illustrating the results obtained by measuring the FET electrode of the present embodiment; and
FIG. 4 is a perspective view of an isolated-type FET electrode.


BEST MODE FOR CARRYING OUT THE INVENTION

First, examples of forming a carbon thin membrane will be illustrated.


Formation Example 1

By using carbon (high-purity graphite carbon G161AS, manufactured by Tokai Carbon K.K.) as a target, a carbon thin membrane was deposited on the surface of sapphire (on silicon) by a sputtering process.
The conditions for sputtering were 100 W, 8.times.10.sup.-2 Torr, 20 hrs, a substrate temperature of less than 150.degree. C. and an argon atmosphere.
As a result, there was obtained a carbon-coated sapphire substrate having a carbon thin membrane thickness of about 1.0 .mu.m.


Formation Example 2

The sputtering conditions were the same as those in Experiment 1 except for the fact that a methane gas atmosphere was used.
As a result, there was obtained a carbon-coated sapphire substrate having a carbon thin membrane thickness of about 1.2 .mu.m. A strong membrane could be produced, and the specific resistance was 1.times.10.sup.-3 .OMEGA.cm.


Formation Example 3

The sputteri

REFERENCES:
patent: 3598713 (1971-08-01), Baum et al.
patent: 3926764 (1975-12-01), Ruzicka et al.
patent: 3932233 (1976-01-01), Ruzicka et al.
patent: 3957612 (1976-05-01), Niedrach et al.
patent: 3957613 (1976-05-01), Macur
patent: 4052285 (1977-10-01), Dobson
patent: 4115209 (1978-09-01), Fraiser et al.
patent: 4198851 (1980-04-01), Janata
patent: 4214968 (1980-07-01), Battaglia et al.
patent: 4280889 (1981-07-01), Szonntagh
patent: 4282079 (1981-08-01), Chang et al.
patent: 4305802 (1981-12-01), Koshiishi
patent: 4454007 (1984-06-01), Pace
patent: 4512870 (1985-04-01), Kohara et al.
patent: 4549951 (1985-10-01), Knudson et al.
patent: 4561962 (1985-12-01), Kankare et al.
patent: 4563263 (1986-01-01), Oyama et al.
patent: 4615954 (1986-10-01), Solomon et al.
patent: 4632732 (1986-12-01), Fog et al.
patent: 4753719 (1988-06-01), Yamaguchi et al.
patent: 4798664 (1989-01-01), Yamaguchi et al.
patent: 4816118 (1989-03-01), Oyama et al.
patent: 4839020 (1989-06-01), Yamaguchi et al.
patent: 4861454 (1989-08-01), Ushizawa et al.
patent: 4981570 (1991-01-01), Yamaguchi et al.
patent: 5001531 (1991-03-01), Yamaguchi
Oyama et al., "Ion Selective Microelectrode Prepared by Modifying an Electrode with Polymers", International Electroanalytical Symposium, May 27-29, 1987, Schaumberg, Ill., pp. 122-124.
Oyama et al., "A New Type of Ion-Selective Microelectrodes Using Electropolymerized Thin Films", The Electrochemical Society Symposium, Honolulu, Hawaii, Oct. 18-23, 1987, pp. 1-2.
Esashi et al., "Biomedical Cation Sensor Using Field Effect of Semiconductor", Proceedings of the 6th Conference on Solid State Devices, Tokyo, 1974, Supplement to the Journal of the Japan Society of Applied Physics, vol. 44, 1975, pp. 339-343.
Patent Abstracts of Japan, vol. 9, No. 122, May 28, 1985, Japanese Kokai No. 60-7357.
Patent Abstracts of Japan, vol. 8, No. 159, Jul. 24, 1984, Japanese Kokai No. 59-57156 (Apr. 2, 1984).
Oyama et al., "Electrochemical Properties of Electropolymerized Poly (1-Pyrinamin) Films", Bull. Chem. Soc., Japan 59-2071-2080 (1986).
Ma et al., "Organic Analysis Using Ion-Sensitive Electrodes", Academic Press, 1982, pp. 62 and 70.
Ryan, "Electrochemical Detectors Fundamental Aspects and Analytical Application" Plenum Press, (Apr. 26, 1985), p. 7.
Ammann, "Ion Selective Microelectrodes", Springer-Verlang, N.Y., pp. 5-7.
Tamura et al., "Coated Wire Sodium- and Potassium-Electrodes Based on Bis(Crown Ether) Compounds", Analytical Chem., vol. 54, No. 7, Jun. 1982, p. 1224.
Wuthier et al., "Tin Organic Compounds as Neutral Carriers for Anion Selective Electrodes"Analytical Chemistry, vol. 56, No. 3, Mar. 1984, pp. 535-538.
Norov et al., "Calcium-Selective Electrode Without an Internal Reference Soluting", Journal of Analytical Chemistry, vol. 34, No. 8, Part 1, Aug. 1979, pp. 1139-1162.
Oyama et al., "Hydrogen Ion Selective Microelectrode Prepared by Modifying an Electrode with Polymers", Analytical Chemistry 1987, vol. 59, pp. 258-262, Jan. 1987.
Oyama et al., "Ion Selective Electrode Prep. by Mod. an Electrode with Polymers", Tokyo Seminar on Macromolecular Complexes, Tokyo Univ., Oct. 14, 1987.
Snell et al., "Surface Modified Electrodes", Chem. Soc. Rev., 1979, 8, 259-282.
Faulkner, "Chemical Microstructures on Electrodes", Chem. Eng. News, 1984, 27, pp. 28-45.

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