CN-122002865-A - Oxide semiconductor thin film transistor

CN122002865ACN 122002865 ACN122002865 ACN 122002865ACN-122002865-A

Abstract

The present invention relates to an oxide semiconductor thin film transistor. The oxide semiconductor thin film transistor includes a gate electrode, a source electrode, a drain electrode, an oxide semiconductor layer connected to the source electrode and the drain electrode, and a gate insulating film between the gate electrode and the oxide semiconductor layer in a stacking direction. The oxide semiconductor layer includes a channel region. The gate insulating film includes a metal oxide film and a first insulating film made of silicon nitride and/or silicon oxynitride. A portion of the first insulating film is provided between the metal oxide film and the oxide semiconductor layer. At least a portion of the first end of the metal oxide film is located on the channel region and faces any one of the source electrode and the drain electrode in a plan view.

Inventors

Hasone Hiroyuki
Mu Cunmao

Assignees

天马日本株式会社

Dates

Publication Date: 20260508
Application Date: 20251103
Priority Date: 20241106

Claims (8)

1. An oxide semiconductor thin film transistor, comprising: A gate electrode; A source electrode; A drain electrode; An oxide semiconductor layer connected to the source electrode and the drain electrode, and A gate insulating film located between the gate electrode and the oxide semiconductor layer in a stacking direction; wherein the oxide semiconductor layer includes a channel region, Wherein the gate insulating film includes: metal oxide film, and A first insulating film made of silicon nitride and/or silicon oxynitride, Wherein a part of the first insulating film is provided between the metal oxide film and the oxide semiconductor layer, and Wherein at least a portion of the first end of the metal oxide film is located on the channel region and faces any one of the source electrode and the drain electrode in a plan view.
2. The oxide semiconductor thin film transistor according to claim 1, wherein a minimum distance between the first end and the source electrode is shorter than a minimum distance between the first end and the drain electrode.
3. The oxide semiconductor thin film transistor according to claim 2, Wherein, in a plan view, the first end faces the source electrode, Wherein, in plan view, the metal oxide film includes a second end facing the drain electrode, and Wherein at least a portion of the second end is located on the channel region in plan view.
4. The oxide semiconductor thin film transistor according to claim 1, Wherein the metal oxide film has an island-like shape, Wherein the metal oxide film has an area smaller than that of the channel region in plan view, an Wherein, in a plan view, the entire metal oxide film is located on the channel region.
5. The oxide semiconductor thin film transistor according to claim 1 or 4, wherein an entire surface of the metal oxide film is surrounded by the first insulating film.
6. The oxide semiconductor thin film transistor according to claim 5, wherein a minimum distance between a centroid of the metal oxide film and the source electrode in a plan view is shorter than a minimum distance between a centroid of the metal oxide film and the drain electrode in a plan view.
7. The oxide semiconductor thin film transistor according to claim 1, wherein the metal oxide film has an interface with the gate electrode.
8. The oxide semiconductor thin film transistor according to claim 1, wherein the metal oxide film is made of silicon oxide, and wherein the first insulating film is made of silicon nitride.

Description

Oxide semiconductor thin film transistor Technical Field The present invention relates to an oxide semiconductor thin film transistor. Background Thin Film Transistors (TFTs) are used in various fields such as display devices and radiation sensors. A TFT having an active layer made of an oxide semiconductor typified by InGaZnO (IGZO) can realize high mobility although having an amorphous structure. However, controlling its threshold voltage is difficult because the added donor and acceptor make it difficult to control fermi energy. Disclosure of Invention There is a need for a technique of controlling the threshold voltage of an oxide semiconductor TFT. An oxide semiconductor thin film transistor according to one aspect of the present invention includes a gate electrode, a source electrode, a drain electrode, an oxide semiconductor layer connected to the source electrode and the drain electrode, and a gate insulating film between the gate electrode and the oxide semiconductor layer in a stacking direction. The oxide semiconductor layer includes a channel region. The gate insulating film includes a metal oxide film and a first insulating film made of silicon nitride and/or silicon oxynitride. A portion of the first insulating film is provided between the metal oxide film and the oxide semiconductor layer. At least a portion of the first end of the metal oxide film is located on the channel region and faces any one of the source electrode and the drain electrode in a plan view. One aspect of the present invention can control the threshold voltage of an oxide semiconductor TFT. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. Drawings Fig. 1 shows an X-ray sensor. Fig. 2 shows a cross-sectional structure of a pixel of the X-ray sensor. Fig. 3 is a sectional view schematically showing a configuration example of an oxide semiconductor TFT having a gate insulating film made of a SiNx/SiOx/SiNx laminated film. Fig. 4A is a band diagram for explaining movement of carriers when the oxide semiconductor TFT is irradiated with X-rays. Fig. 4B is another energy band diagram for explaining movement of carriers when the oxide semiconductor TFT is irradiated with X-rays. Fig. 5 is a sectional view schematically showing the configuration of an oxide semiconductor TFT in an embodiment of the present invention. Fig. 6 is a plan view schematically showing a positional relationship among a silicon oxide film, a channel region, and some other components in an oxide semiconductor TFT. Fig. 7A schematically illustrates a state of charge that occurs when the oxide semiconductor TFT in the embodiment illustrated in fig. 5 and 6 is supplied with a gate bias and irradiated with radioactive rays. Fig. 7B is a diagram schematically showing negative shift of the threshold voltage. Fig. 8A schematically illustrates another charge state that occurs when the oxide semiconductor TFT in the embodiment illustrated in fig. 5 and 6 is supplied with a gate bias and irradiated with radioactive rays. Fig. 8B is a diagram schematically showing a positive shift of the threshold voltage. Fig. 9 provides a graph showing the relationship between the intensity of an electric field generated by plane charges having different areas and the distance from the plane charges. Fig. 10 is a sectional view schematically showing the configuration of an oxide semiconductor TFT in another embodiment of the present invention. Fig. 11 is a plan view schematically showing a positional relationship among a silicon oxide film, a channel region, and some other components in the oxide semiconductor TFT shown in fig. 10. Fig. 12 is a cross-sectional view schematically showing the configuration of an oxide semiconductor TFT in still another embodiment of the present invention. Fig. 13 is a plan view schematically showing a positional relationship among a silicon oxide film, a channel region, and some other components in the oxide semiconductor TFT shown in fig. 12. Fig. 14A shows planar charges infinitely extending in both positive and negative directions along the Y axis and in the positive direction along the X axis. Fig. 14B shows the intensities of the Z-axis components of the electric field generated by the plane charges in fig. 14A at different coordinates (x, Z). Fig. 15 is a cross-sectional view schematically showing the configuration of an oxide semiconductor TFT in still another embodiment of the present invention. Fig. 16 is a plan view schematically showing a positional relationship among a silicon oxide film, a channel region, and some other members in the oxide semiconductor TFT shown in fig. 15. Fig. 17 is a plan view schematically showing the configuration of an oxide semiconductor TFT in still another embodiment of the present invention. Fig. 18 is a sectional view schematically showing the configuration of an oxide