1. Field of the Invention
The present invention relates to a thin film transistor (TFT) and a method of manufacturing the same.
2. Description of the Related Art
A thin film transistor (TFT) is a transistor that uses a semiconductor material as an active layer. Recently, research is being conducted on TFTs that are included in a pixel area of a flat display device, such as an organic light emitting display device, so that light can pass through a TFT and be output to the outside.
Conventionally, the electrical contact between a source electrode and a semiconductor layer of a TFT, or between a drain electrode and the semiconductor layer of the TFT is an important factor for defining the characteristics of the TFT. Accordingly, in a conventional silicon TFT using a silicon semiconductor layer as an active layer, the silicon semiconductor layer is doped to increase the electrical contact (e.g., to decrease a resistance ohmic contact) between the source electrode and the silicon semiconductor layer, or between the drain electrode and the silicon semiconductor layer, thereby improving the characteristics of the conventional silicon TFT.
However, as discussed above, research is being conducted on a TFT using a semiconductor material as an active layer that can be applied to a structure in which light can pass through the TFT that is included in a display unit so that the light is output to the outside. In such TFT, the electrical contact between the source electrode and the active layer or between the drain electrode and an active layer should be further increased.
In a TFT, an oxide semiconductor can provide a relatively low resistance ohmic contact (of 10−5 Ωcm2 or less) that is formed between the oxide semiconductor and the source and drain electrodes. To this end, a dopant such as Ga or Al may be applied through an ion injection process such as silicon doping; however, the temperature of the activation process in this case is 500° C. or higher. Thus, due to this high temperature, the oxide semiconductor cannot be applied to a plastic substrate in order to realize a flexible flat display device.