Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Method of fabricating thin film transistor and method of fabricating liquid crystal display

Method of fabricating thin film transistor and method of fabricating liquid crystal display description/claims

This is a continuation application of patent application Ser. No. 11/357,812, filed on Feb. 16, 2006, which claims the priority benefit of Taiwan patent application serial no. 94104418 and 94139059, filed on Feb. 16, 2005, and Nov. 8, 2005. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

1. Field of the Invention

The present invention relates to a method of fabricating a thin film transistor of a thin film transistor liquid crystal display (TFT-LCD) and a method of fabricating a liquid crystal display. More particularly, the present invention relates to a method of fabricating a thin film transistor of a thin film transistor liquid crystal display (TFT-LCD) and a method of fabricating the liquid crystal display by damascene process.

2. Description of the Related Art

With the rapid progress in the fabrication of semiconductor devices and man-machine interfacing devices, multimedia technologies are deployed everywhere in our society. In the past, cathode ray tubes (CRT) were one of the most important display devices in the market due to their high display quality and moderate pricing. However, in an environment where a large number of desktop operated terminals/display devices are used, energy consumption is also a very important consideration. Because a CRT wastes a lot of power and has a poor spatial utilization, other types of display devices having higher display quality, greater spatial utilization, lower power consumption and capable of radiation-free operation such as the thin film transistor liquid crystal display (TFT-LCD) gradually take over. In fact, TFT-LCD has become one of the mainstream display devices in the market.

The conventional method of fabricating a thin film transistor includes forming a gate on a substrate and then forming an insulating layer and a semiconductor layer sequentially over the substrate to cover the gate. Thereafter, a source and a drain are formed on the semiconductor layer to form a thin film transistor.

In the conventional method of fabricating the thin film transistor, a photolithographic and etching process is used to pattern metallic layers for producing the gate, the source and the drain. Thus, the metallic layers must have a property that matches with the liquid etchant or gaseous etchant used in the etching operation. Therefore, a metal having an ideal etching property such as aluminum to form the metallic layer is selected in the prior art. However, when this type of material is used, the materials that can be used to form the electrodes of the thin film transistor are limited. In particular, because aluminum has a higher resistance relative to other metals, the increase in electrical resistance as the device miniaturization will directly affect the performance of the thin film transistors.

Accordingly, at least one objective of the present invention is to provide a method of fabricating a thin film transistor of a thin film transistor liquid crystal display that can increase the choice of material for forming the electrodes of the thin film transistor.

At least a second objective of the present invention is to provide a method of fabricating a thin film transistor of a thin film transistor liquid crystal display that can improve the electrical performance of the thin film transistor.

At least a third objective of the present invention is to provide a method of fabricating a liquid crystal display that can improve the electrical performance of the liquid crystal display.

To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method of fabricating a thin film transistor of a thin film transistor liquid crystal display. First, a first patterned dielectric layer is formed over a substrate and then a first metallic layer is formed over the substrate to cover the first patterned dielectric layer. Thereafter, the first metallic layer is planarized until the first patterned dielectric layer is exposed. The remaining first metallic layer serves as a gate. After that, a gate insulating layer is formed over the first patterned dielectric layer and the gate. A semiconductor layer is formed over the gate insulating layer above the gate. Finally, a source and a drain are formed over the semiconductor layer.

According to the preferred embodiment of the present invention, the step of planarizing the metallic layer includes performing a chemical-mechanical polishing operation.

According to the preferred embodiment of the present invention, the material constituting the first metallic layer is selected from the group consisting of copper, tungsten, chromium, aluminum and a combination thereof.

According to the preferred embodiment of the present invention, the method of forming the source and the drain includes forming a second patterned dielectric layer over the gate insulating layer and then forming a second metallic layer over the second patterned dielectric layer. Thereafter, a planarization process is performed to remove a portion of the second metallic layer and a portion of the second patterned dielectric layer so as to form the source and the drain. The planarization process includes a chemical-mechanical polishing operation. The material constituting the second metallic layer is selected from the group consisting of copper, tungsten, chromium, aluminum and a combination thereof. Furthermore, after forming the source and the drain, the second patterned dielectric layer is removed.

According to the preferred embodiment of the present invention, before forming the first patterned dielectric layer over the substrate, further comprises forming a stress-buffering layer over the substrate.

According to the preferred embodiment of the present invention, the stress-buffering layer is selected from the group consisting of a silicon oxide layer, a silicon nitride layer, a silicon oxynitride layer and a combination thereof.

According to the preferred embodiment of the present invention, the semiconductor layer comprises a channel layer and an ohmic contact layer.

The present invention also provides an alternative method of fabricating a thin film transistor of a thin film transistor liquid crystal display. First, a gate is formed over a substrate and then a gate insulating layer is formed over the substrate to cover the gate. Thereafter, a semiconductor layer is formed on the gate insulating layer above the gate. A patterned dielectric layer is formed over the gate insulating layer. After that, a metallic layer is formed over the patterned dielectric layer and then a planarization process is performed to remove a portion of the metallic layer and a portion of the patterned dielectric layer to form a source and a drain.

• Provisional Patent
• Utility Patent

• What Is a Patent?
• What Is a Trademark or Servicemark?
• What Is a Copyright?
• Patent Laws