Method for forming oxide semiconductor film and method for manufacturing semiconductor device

Abstract

An oxide semiconductor film is formed over a substrate. A sacrifice film is formed to such a thickness that the local maximum of the concentration distribution of an injected substance injected into the oxide semiconductor film in the depth direction of the oxide semiconductor film is located in a region from an interface between the substrate and the oxide semiconductor film to a surface of the oxide semiconductor film. Oxygen ions are injected as the injected substance into the oxide semiconductor film through the sacrifice film at such an acceleration voltage that the local maximum of the concentration distribution of the injected substance in the depth direction of the oxide semiconductor film is located in the region, and then the sacrifice film is removed. Further, a semiconductor device is manufactured using the oxide semiconductor film.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method for forming an oxide semiconductor film or an insulating film, and to a method for manufacturing a semiconductor device with the use of the oxide semiconductor film or the insulating film.[0003]Note that a semiconductor device in this specification refers to general devices which can function by utilizing semiconductor characteristics; for example, a semiconductor element such as a transistor, a semiconductor circuit including a semiconductor element, an electro-optical device such as a display device, and an electronic device are all semiconductor devices.[0004]2. Description of the Related Art[0005]Transistors used for most flat panel displays typified by a liquid crystal display device and a light-emitting display device are formed using silicon semiconductors such as amorphous silicon, single crystal silicon, and polycrystalline silicon provided over glass substrates. Furthe...

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Benefits of technology

[0029]In the above embodiment, the sacrifice film can be formed using a material that is the same as or different from that for the film formed under the sacrifice film. By forming the sacrifice film with the use of a material that is different from that for the film formed under the sacrifice film, the sacrifice film can be easily removed by utilizing etching selectivity at the removal of the sacrifice film. By forming the sacrifice film with the use of the same material as the film formed under the sacrifice film, the time taken to form the film of one embodiment of the present invention can be shortened, and impurities which might be attached to the film formed under the sacrifice film in the case where the sacrifice film is formed using a material that is different from that for the film formed under the sacrifice film can be reduced.

[0034]Further, when the local maximum of the oxygen ion concentration distribution is located in the vicinity of the surface of the base insulating film, the distance which the oxygen ion travels to the oxide semiconductor film formed over the base insulating film can be shortened; thus, oxygen vacancies in the oxide semiconductor film can be effectively filled. Accordingly, a transistor having favorable electrical characteristics can be manufactured.

[0035]When oxygen ions are injected into an injection target such as an oxide semiconductor film or an insulating film by an ion implantation method or an ion doping method, not only the injected oxygen ions but also impurities attached to the injection target are put into the injection target owing to a knock-on effect. If a transistor is manufactured using such an injection target including impurities, the transistor might have unfavorable electrical characteristics. In contrast, by forming a sacrifice film, and then injecting oxygen ions and removing the sacrifice film as in one embodiment of the present invention, impurities included in an injection target can be reduced, and thus, a transistor having favorable electrical characteristics can be manufactured.

[0036]According to one embodiment of the present invention, a method for forming an oxide semiconductor film into which oxygen ions are uniformly injected can be provided. Furthermore, according to one embodiment of the present invention, a method for manufacturing a semiconductor device having favorable electrical characteristics with the use of the oxide semiconductor film can be provided.

Problems solved by technology

However, in an oxide semiconductor, charge is generated owing to an oxygen vacancy caused therein.

Consequently, the lowering of the acceleration voltage for oxygen ion injection leads to a non-uniform concentration of the injected oxygen ions in the depth direction of the oxide semiconductor, and thus, oxygen vacancies might not be sufficiently filled.

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