Abstract:
An object is to provide an oxide semiconductor having stable electric characteristics and a semiconductor device including the oxide semiconductor. A manufacturing method of a semiconductor film by a sputtering method includes the steps of holding a substrate in a treatment chamber which is kept in a reduced-pressure state; heating the substrate at lower than 400° C.; introducing a sputtering gas from which hydrogen and moisture are removed in the state where remaining moisture in the treatment chamber is removed; and forming an oxide semiconductor film over the substrate with use of a metal oxide which is provided in the treatment chamber as a target. When the oxide semiconductor film is formed, remaining moisture in a reaction atmosphere is removed; thus, the concentration of hydrogen and the concentration of hydride in the oxide semiconductor film can be reduced. Thus, the oxide semiconductor film can be stabilized.
Abstract:
There have been cases where transistors formed using oxide semiconductors are inferior in reliability to transistors formed using amorphous silicon. Thus, in the present invention, a semiconductor device including a highly reliable transistor formed using an oxide semiconductor is manufactured. An oxide semiconductor film is deposited by a sputtering method, using a sputtering target including an oxide semiconductor having crystallinity, and in which the direction of the c-axis of a crystal is parallel to a normal vector of the top surface of the oxide semiconductor. The target is formed by mixing raw materials so that its composition ratio can obtain a crystal structure.
Abstract:
Many of the physical properties of a silicon semiconductor have already been understood, whereas many of the physical properties of an oxide semiconductor have been still unclear. In particular, an adverse effect of an impurity on an oxide semiconductor has been still unclear. In view of the above, a structure is disclosed in which an impurity that influences electrical characteristics of a semiconductor device including an oxide semiconductor layer is prevented or is eliminated. A semiconductor device which includes a gate electrode, an oxide semiconductor layer, and a gate insulating layer provided between the gate electrode and the oxide semiconductor layer and in which the nitrogen concentration in the oxide semiconductor layer is 1×1020 atoms/cm3 or less is provided.
Abstract:
To provide a highly reliable semiconductor device manufactured by giving stable electric characteristics to a semiconductor device including an oxide semiconductor. In a manufacturing process of a transistor, an oxide semiconductor layer, a source electrode layer, a drain electrode layer, a gate insulating film, a gate electrode layer, and an aluminum oxide film are formed in this order, and then heat treatment is performed on the oxide semiconductor layer and the aluminum oxide film, whereby an oxide semiconductor layer from which an impurity containing a hydrogen atom is removed and which includes a region containing oxygen more than the stoichiometric proportion is formed. In addition, when the aluminum oxide film is formed, entry and diffusion of water or hydrogen into the oxide semiconductor layer from the air due to heat treatment in a manufacturing process of a semiconductor device or an electronic appliance including the transistor can be prevented.
Abstract:
The silicon nitride layer 910 formed by plasma CVD using a gas containing a hydrogen compound such as silane (SiH4) and ammonia (NH3) is provided on and in direct contact with the oxide semiconductor layer 905 used for the resistor 354, and the silicon nitride layer 910 is provided over the oxide semiconductor layer 906 used for the thin film transistor 355 with the silicon oxide layer 909 serving as a barrier layer interposed therebetween. Therefore, a higher concentration of hydrogen is introduced into the oxide semiconductor layer 905 than into the oxide semiconductor layer 906. As a result, the resistance of the oxide semiconductor layer 905 used for the resistor 354 is made lower than that of the oxide semiconductor layer 906 used for the thin film transistor 355.
Abstract:
The silicon nitride layer 910 formed by plasma CVD using a gas containing a hydrogen compound such as silane (SiH4) and ammonia (NH3) is provided on and in direct contact with the oxide semiconductor layer 905 used for the resistor 354, and the silicon nitride layer 910 is provided over the oxide semiconductor layer 906 used for the thin film transistor 355 with the silicon oxide layer 909 serving as a barrier layer interposed therebetween. Therefore, a higher concentration of hydrogen is introduced into the oxide semiconductor layer 905 than into the oxide semiconductor layer 906. As a result, the resistance of the oxide semiconductor layer 905 used for the resistor 354 is made lower than that of the oxide semiconductor layer 906 used for the thin film transistor 355.
Abstract:
A highly reliable semiconductor device is manufactured by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. An oxide semiconductor film which can have a first crystal structure by heat treatment and an oxide semiconductor film which can have a second crystal structure by heat treatment are formed so as to be stacked, and then heat treatment is performed; accordingly, crystal growth occurs with the use of an oxide semiconductor film having the second crystal structure as a seed, so that an oxide semiconductor film having the first crystal structure is formed. An oxide semiconductor film formed in this manner is used for an active layer of the transistor.
Abstract:
An object is to provide a thin film transistor and a method for manufacturing the thin film transistor including an oxide semiconductor with a controlled threshold voltage, high operation speed, a relatively easy manufacturing process, and sufficient reliability. An impurity having influence on carrier concentration in the oxide semiconductor layer, such as a hydrogen atom or a compound containing a hydrogen atom such as H2O, may be eliminated. An oxide insulating layer containing a large number of defects such as dangling bonds may be formed in contact with the oxide semiconductor layer, such that the impurity diffuses into the oxide insulating layer and the impurity concentration in the oxide semiconductor layer is reduced. The oxide semiconductor layer or the oxide insulating layer in contact with the oxide semiconductor layer may be formed in a deposition chamber which is evacuated with use of a cryopump whereby the impurity concentration is reduced.
Abstract:
In a thin film transistor which uses an oxide semiconductor, buffer layers containing indium, gallium, zinc, oxygen, and nitrogen are provided between the oxide semiconductor layer and the source and drain electrode layers.