US 12,270,782 B2
Ion sensing device
Kazushige Takechi, Kanagawa (JP); Shinnosuke Iwamatsu, Yamagata (JP); Hiroki Murayama, Yamagata (JP); and Yoshiyuki Watanabe, Yamagata (JP)
Assigned to TIANMA JAPAN, LTD., Kanagawa (JP)
Filed by TIANMA JAPAN, LTD., Kanagawa (JP)
Filed on Nov. 23, 2021, as Appl. No. 17/533,239.
Claims priority of application No. 2020-208837 (JP), filed on Dec. 16, 2020.
Prior Publication US 2022/0187238 A1, Jun. 16, 2022
Int. Cl. G01N 27/414 (2006.01)
CPC G01N 27/4145 (2013.01) 9 Claims
OG exemplary drawing
 
1. An ion sensing device comprising:
a first field-effect transistor;
a second field-effect transistor;
a reference electrode configured to directly contact a sample solution;
a first ion-sensitive film; and
a second ion-sensitive film,
wherein each of the first field-effect transistor and the second field-effect transistor includes:
a semiconductor film;
a bottom gate electrode;
a bottom gate insulating film located between the bottom gate electrode and the semiconductor film; and
a top gate insulating film,
wherein the first ion-sensitive film is configured to generate a top gate potential with respect to the semiconductor film of the first field-effect transistor in accordance with an ion concentration of the sample solution when being in direct contact with a sample solution,
wherein the second ion-sensitive film is configured to generate a top gate potential with respect to the semiconductor film of the second field-effect transistor in accordance with the ion concentration of the sample solution when being in direct contact with the sample solution,
wherein a potential of the reference electrode is supplied to a source/drain of the semiconductor film of each of the first field-effect transistor and the second field-effect transistor,
wherein surface materials in contact with the sample solution for the first ion-sensitive film and the second ion-sensitive films are the same,
wherein a sensitivity of the combination of the first field-effect transistor and the first ion-sensitive film is higher than a sensitivity of the combination of the second field-effect transistor and the second ion-sensitive film and,
wherein a value of a ratio of an electrostatic capacity per unit area of the top gate insulating film to an electrostatic capacity per unit area of the bottom gate insulating film about the first field-effect transistor is larger than a value of a ratio of an electrostatic capacity per unit area of the top gate insulating film to an electrostatic capacity per unit area of the bottom gate insulating film about the second field-effect transistor.