Image sensor and method of manufacturing the same
In manufacturing an image sensor for FPD having an oxide semiconductor TFT as a switching element, a large amount of hydrogen contained in raw gas is diffused in the oxide semiconductor at the time of forming a-Si photo diode (PD) which is a photoelectric conversion element, causing significant variation in the characteristic of TFT which may thereby not operate. In an image sensor in which an oxide semiconductor TFT and a-Si PD are formed on a substrate in this order, a gas barrier film is disposed between the oxide semiconductor TFT and the PD, and the drain terminal (drain metal) of the oxide semiconductor TFT is connected to one terminal (lower electrode) of the PD via connection wiring (bridge wiring) formed on a protective film arranged over the PD.
1. An image sensor, comprising:
a substrate;
a gas barrier film;
a protective film; and
a plurality of pixels,
wherein each one of the pixels includes a switching element including an oxide semiconductor TFT, a photoelectric conversion element including a photodiode having amorphous silicon, and a connection wiring configured to electrically connect the switching element and the photoelectric conversion element, the gas barrier film disposed above the switching elements on the substrate,
the photoelectric conversion element disposed above the gas barrier film and including an upper electrode at an upper part in a layering direction and a lower electrode at a lower part in the layering direction,
the protective film covering the photoelectric conversion element, and
the connection wiring i) being made of a single material, ii) being arranged on the protective film covering the photoelectric conversion element, and iii) electrically connecting, via contact holes, the switching element and the photoelectric conversion element of a same pixel, said contact holes including a first contact hole penetrating the protective film and the gas barrier film, and a second contact hole penetrating the protective film, the connection wiring connected to the drain electrode of the switching element via the first contact hole, and connected to the lower electrode of the photoelectric conversion element via the second contact hole.
2. The image sensor according to claim 1 , wherein an opening area of a through hole of the first contact hole in the protective film is equal to or larger than an opening area of a through hole of the first contact hole in the gas barrier film.
3. The image sensor according to claim 1 , wherein an inner surface of the through hole of the first contact hole in the gas barrier film is in contact with a part of the connection wiring.
4. The image sensor according to claim 1 , wherein the oxide semiconductor TFT includes two gate electrodes arranged separately from each other in a layering direction.
5. The image sensor according to claim 1 , wherein the gas barrier film is an organic insulating film.
6. The image sensor according to claim 5 , wherein the organic insulating film is made of xylene polymer or a derivative of the xylene polymer, acrylic resin or epoxy resin.
7. The image sensor according to claim 1 , wherein the gas barrier film is an inorganic insulating film.
8. The image sensor according to claim 7 , wherein the inorganic insulating film is a film of silicon nitride or aluminum oxide.
9. The image sensor according to claim 1 , wherein the gas barrier film is an inorganic insulating film, and the lower electrode of the photoelectric conversion element is located to be in contact with the gas barrier film.
10. The image sensor according to claim 1 , wherein a thickness of the gas barrier film is equal to or larger than 1 μm.
11. A method of manufacturing an image sensor, comprising the steps of:
layering, on a substrate, a switching element formed of an oxide semiconductor TFT, a gas barrier film and a photoelectric conversion element including a photo diode having amorphous silicon in order of the switching element, the gas barrier film and the photoelectric conversion element, the photoelectric conversion element including an upper electrode at an upper part in a layering direction and a lower electrode at a lower part in the layering direction;
forming a protective film covering the photoelectric conversion element and forming contact holes in the protective film and the gas barrier film; and
forming a connection wiring, formed of a single conductive layer, on the protective film and electrically connecting a drain electrode of the switching element and one terminal of the photoelectric conversion element via the contact holes,
the contact holes including a first contact hole penetrating the protective film and the gas barrier film, and a second contact hole penetrating the protective film, the connection wiring connected to the drain electrode of the switching element via the first contact hole, and connected to the lower electrode of the photoelectric conversion element via the second contact hole.
12. The image sensor according to claim 1 , wherein the connection wiring connects a drain electrode of the switching element and one terminal of the photoelectric conversion element in the same pixel, the oxide semiconductor TFT configured to switch a current from the terminal of the photoelectric conversion element.