pH sensor and pH measurement method employing the same

Details pH sensor and pH measurement method employing the same pH sensor and pH measurement method employing the same

2000-06-13

2002-10-15

Warden, Jill (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing liquid or solid sample

C204S433000, C204S416000, C204S422000, C205S789000, C205S787500, C422S068100

Reexamination Certificate

active

06464940

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to pH sensors and pH measurement methods, and in particular to pH sensors and pH measurement methods suitable for measuring the pHs of solutions of small amounts.
2. Description of the Background Art
A conventional sensor for measuring the pH of a solution employs an ion-sensitive field effect transistor (ISFET). This sensor includes an ISFET
201
and a reference electrode
202
, as shown in FIG.
10
. To measure the pH of a solution
203
, ISFET
201
and reference electrode
202
are placed in sample solution
203
. The gate potential of ISFET
201
varies with the pH of solution
203
, and such variation is used to measure the pH of the solution. In this conventional technique, however, an ISFET and a reference electrode both must be placed in a solution and for a small amount of solution its pH can hardly be measured.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a pH sensor capable of readily measuring the pH of a solution of a small amount.
Another object of the present invention is to provide a pH sensor having a simple structure applicable to biosensors and the like.
According to the present invention, a pH sensor is provided which includes a semiconductor substrate, an insulating film provided on the semiconductor substrate, a solution storage part provided to hold a solution on the insulating film, and a metal electrode provided to be in contact with the solution.
According to the present invention, the solution storage part may have a surrounding wall provided to hold a solution on the insulating film.
According to the present invention, a pH measurement method is provided in which a solution is introduced into the solution storage part of the pH sensor of the present invention as described above, and then a capacitance-voltage characteristic is determined between the metal electrode in contact with the solution and a surface of the substrate forming the sensor which is opposite to the substrate surface having the insulating film provided thereon. A flat band voltage is obtained based on the determination, and the pH of the solution is obtained based on the flat band voltage.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.


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