THIN FILM TRANSISTOR, ACTIVE MATRIX SUBSTRATE, AND IMAGE PICKUP DEVICE

• US 20100044711A1
• Filed: 08/11/2009
• Published: 02/25/2010
• Est. Priority Date: 08/19/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: IMAI, Shinji
• Granted Patent: US 8,134,151 B2
• Time in Patent Office: Days
• US Class Current: 257/59
• CPC Class Codes: H01L 27/14676 X-ray, gamma-ray or corpuscular radiation imagers measuring X-, gamma- or corpuscular radiation G01T1/00
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/78636 with supplementary region or layer for improving the flatness of the device
• CPC Class Codes: H01L 29/78648 arranged on opposing sides of the channel
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

A thin film transistor including: source and drain electrodes, an active layer that contacts the source and drain electrodes and contains an oxide semiconductor, a gate electrode that controls current flowing between the source and drain electrodes via the active layer, a first insulating film that separates the gate electrode from the source and drain electrodes and the active layer, a bias electrode that is arranged at the opposite side of the active layer from the gate electrode, and has an electric potential fixed independently from the gate electrode, and a second insulating film that separates the bias electrode from the source and drain electrodes and the active layer.

Claims

1. A thin film transistor comprising:

source and drain electrodes,

an active layer that contacts the source and drain electrodes and contains an oxide semiconductor,

a gate electrode that controls current flowing between the source and drain electrodes via the active layer,

a first insulating film that separates the gate electrode from the source and drain electrodes and the active layer,

a bias electrode that is arranged at the opposite side of the active layer from the gate electrode, and has an electric potential fixed independently from the gate electrode, and

a second insulating film that separates the bias electrode from the source and drain electrodes and the active layer.

2. The thin film transistor according to claim 1, wherein the second insulating film is a gallium oxide film.

3. The thin film transistor according to claim 1, wherein the carrier concentration in the active layer is 3×

10¹⁷ cm<sup>−

3</sup> or more.

4. The thin film transistor according to claim 1, wherein the electric potential of the bias electrode is fixed within the range of −

2 to +0.5 V.

5. An active matrix substrate comprising thin film transistors as described in claim 1 arranged on a support substrate.

6. The active matrix substrate according to claim 5, wherein the bias electrodes of the thin film transistors arranged on the support substrate are connected with one another to be electrically common with one another.

7. An image pickup device comprising:

a common electrode,

a charge generating film that generates a charge responding to an electromagnetic wave that is an object to be detected, to which charge generating film voltage is applied by the common electrode,

a charge collecting electrode that collects the charge generated by the charge generating film,

a charge detecting capacitor that accumulates the charge collected by the charge collecting electrode,

a charge detecting thin film transistor that detects the amount of the charge accumulated in the charge detecting capacitor,

a resetting thin film transistor that leaks the charge accumulated in the charge detecting capacitor to reset the charge detecting capacitor, and

a support substrate supporting the charge generating film, the charge collecting electrode, the charge detecting capacitor, the charge detecting thin film transistor, and the resetting thin film transistor,

wherein the thin film transistor as described in claim 1 is provided as the charge detecting thin film transistor.

8. The image pickup device according to claim 7, wherein a part of the charge collecting electrode overhangs above the charge detecting thin film transistor in an insulated state, and serves also as the gate electrode of the charge detecting thin film transistor.

9. The image pickup device according to claim 7, wherein a part of the charge collecting electrode overhangs above the resetting thin film transistor in an insulated state.

10. The image pickup device according to claim 7, wherein the charge generating film generates a charge responding to X-rays.