Coating apparatus – Gas or vapor deposition – Multizone chamber
Reexamination Certificate
2000-11-20
2002-10-08
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
Multizone chamber
C118S715000, C156S345110, C156S345220, C156S345310, C156S345320, C156S345500, C156S345550, C156S345210, C414S217100, C414S935000, C414S937000, C414S939000, C414S940000
Reexamination Certificate
active
06461437
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to apparatuses used for fabricating liquid crystal devices and methods of fabricating the same and particularly to driver circuit integrated liquid crystal display devices and methods of fabricating the same.
2. Description of the Background Art
In a driver circuit integrated liquid crystal display device with a thin film transistor (TFT), a TFT in a pixel region only serves to charge a pixel electrode and switch to hold electric charge. As such, it does not require a precisely controlled threshold voltage, as is required for typical semiconductor devices. As such, it can operate satisfactorily with its thin film semiconductor formed of amorphous silicon.
In recent years, there has been developed a technology using a polycrystalline silicon TFT fabricated by laser-annealing amorphous silicon and there have been increasingly fabricated liquid crystal devices using this polycrystalline silicon TFT. Advantageously, the liquid crystal display device of this type has a driver circuit region and a pixel region integrally formed to reduce its fabrication cost and provide the display pixels with high definition. This polycrystalline silicon TFT is required to have a characteristic required for an element of the driver circuit and it is thus required to have a threshold voltage held with high precision. In this situation, a new issue to be overcome has arisen.
A process using amorphous silicon to fabricate a conventional liquid crystal display device normally includes;prior to the amorphous silicon deposition step, a cleaning step to remove foreign matter and provide an amorphous silicon film with an enhanced contact performance.
FIG. 12
shows the environment of a conventional route from a cleaning step to a deposition step. The cleaning step includes a physical cleaning step
110
and a chemical cleaning step
120
. A substrate
111
mounted in a cassette
106
is input by an automatic guided vehicle (AGV)
140
into a loader
143
and input by a transport robot
104
into a physical cleaning chamber and thus physically washed. The term “substrate” herein refers to a substrate per se such as a quartz substrate as well as a processed substrate. Initially, the substrate is irradiated with ultraviolet light output from a UV lamp
151
and thus has organic matter removed therefrom. Then the substrate is sent to a physical cleaning unit
152
and therein cleaned with a brush, megasonically, or in a similar manner. Then the substrate is passed through a water-washing unit
154
and a drying unit
155
and thus delivered into an unloader
145
. Chemical cleaning step
120
, having a chemical cleaning unit
153
using a chemical for cleaning a substrate, has an inlet and an outlet respectively inputting and outputting the substrate in the same manner as the physical cleaning step. The substrate physically and chemically cleaned is accommodated in cassette
106
open to the atmosphere of a clean room and thus transported to a film deposition chamber
102
by the AGV and input to a loader/unloader
146
thereof, in which substrate
111
is ejected by transport robot
104
from cassette
106
and introduced into the film deposition chamber and subjected to the amorphous silicon deposition step. Then, substrate
111
is again exposed to the atmosphere of the clean room and thus transported to a laser annealing chamber and therein it is laser-annealed to crystallize the deposited amorphous silicon. Waiting until the film deposition chamber is available, such substrates can be disadvantageously forced to be reserved in an inventory
130
and an underlying film thereof can be disadvantageously exposed to the atmosphere internal to the clean room over a long period of time. Conventionally, substrates being transported and reserved have been strictly controlled to prevent particles from adhering thereto.
However, the above substrate, exposed to the atmosphere of the clean room, has a surface insufficiently controlled and thus chemically contaminated. Such chemical contamination does not at all affect an amorphous silicon TFT used only in a pixel region. For a polycrystalline silicon TFT configuring a driver circuit, however, the doping effect of metal contamination or the like and the influence of organic contamination, for example upon the grain growth of polycrystalline silicon appear. Thus, the transistor's threshold voltage varies, an in-substrate variance occurs and the driver circuit erroneously operates, disadvantageously resulting in a reduced yield.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus manufacturing a liquid crystal display device capable of preventing a chemical contamination attributed to being exposed to an atmosphere internal to a clean room, to prevent a threshold voltage from having a variance or the like, and a method of manufacturing the same.
The present invention provides an apparatus manufacturing a liquid crystal display device, including a cleaning chamber cleaning a substrate of a liquid crystal display device, a film deposition chamber depositing a film on the substrate cleaned in the cleaning chamber, and means for transporting the substrate from the cleaning chamber to the film deposition chamber while preventing the substrate from being exposed to an external atmosphere.
As such, the substrate after it is cleaned is not exposed to the atmosphere of the clean room and it is thus prevented from chemical contamination. This can prevent metal contamination resulting in a doping effect and also prevent organic contamination resulting in the crystal grain size having a variance. As such, a threshold voltage does not vary. Furthermore, the substrate after it is cleaned can be free of particles adhering thereto. As a result, the driver circuit does not erroneously operate and the production yield is thus not reduced. It should be noted that the above substrate is that as previously defined.
In the above present apparatus the means for transporting includes a path blocking an external atmosphere and transporting the substrate from the cleaning chamber to the film deposition chamber, and a transporter transporting the substrate through the path.
As such, the substrate can be readily, automatically transported while it is not exposed to the external atmosphere. Since the substrate can be automatically transported, the substrate does not need to wait for a long period of time and it can also be transported in a reduced period of time. Thus, the device can be manufactured efficiently.
In the above present apparatus the means for transporting includes means for inputting into a sealed cassette isolatable from an external atmosphere the substrate cleaned in the cleaning chamber, while preventing the substrate from being exposed to the atmosphere, and means for outputting in the film deposition chamber the substrate from the sealed cassette.
As such, the substrate is not exposed to the external atmosphere and can thus be accommodated in the sealed cassette and thus transported from the cleaning chamber to the film deposition chamber. Thus, the substrate can be free of chemical contamination and particles adhering thereto after it is cleaned. The sealed cassette may be transported from the cleaning chamber's unloading portion to the film deposition chamber's loading portion by means of a transporting machine such as an AGV or manually.
The above present apparatus further includes a cassette load chamber and a transport robot chamber having a transport robot, wherein the cassette load chamber, the cleaning chamber and the film deposition chamber are arranged to surround the transport robot and connected to the transport robot chamber to allow the transport robot to input and output the substrate.
As such, from the cassette load chamber through the cleaning chamber to the film deposition chamber the transport robot can transport the substrate sequentially without exposing the substrate to the external atmosphere. As such, the substrat
Komatsu Norikazu
Kubota Takeshi
Lund Jeffrie R.
Mitsubishi Denki & Kabushiki Kaisha
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