Material or article handling – Apparatus for moving material between zones having different...
Reexamination Certificate
1998-05-20
2001-04-10
Keenan, James W. (Department: 3652)
Material or article handling
Apparatus for moving material between zones having different...
C414S805000, C414S939000
Reexamination Certificate
active
06213704
ABSTRACT:
BACKGROUND
The invention relates to substrate processing, and more particularly to transferring substrates to and from processing chambers.
Glass substrates are being used for applications such as active matrix televisions and computer displays, among others. A large glass substrate can form multiple display monitors, each of which may contain more than a million thin film transistors.
The processing of large glass substrates often involves the performance of multiple sequential steps, including, for example, the performance of chemical vapor deposition (CVD) processes, physical vapor deposition (PVD) processes, or etch processes. Systems for processing glass substrates can include one or more process chambers for performing those processes.
The glass substrates can have dimensions, for example, of 550 mm by 650 mm. The trend is toward even larger substrate sizes, such as 650 mm by 830 mm and larger, to allow more displays to be formed on the substrate or to allow larger displays to be produced. The larger sizes place even greater demands on the capabilities of the processing systems.
Some of the basic processing techniques for depositing thin films on the large glass substrates are generally similar to those used, for example, in the processing of semiconductor wafers. Despite some of the similarities, however, a number of difficulties have been encountered in the processing of large glass substrates that cannot be overcome in a practical way and cost effectively by using techniques currently employed for semiconductor wafers and smaller glass substrates.
For example, efficient production line processing requires rapid movement of the glass substrates from one work station to another, and between vacuum environments and atmospheric environments. The large size and shape of the glass substrates makes it difficult to transfer them from one position in the processing system to another. As a result, cluster tools suitable for vacuum processing of semiconductor wafers and smaller glass substrates, such as substrates up to 550 mm by 650 mm, are not well suited for the similar processing of larger glass substrates, such as 650 mm by 830 mm and above. Moreover, cluster tools require a relatively large floor space.
One way to improve such processing tools is disclosed in U.S. patent application Ser. No. 08/946,922, entitled “MODULAR CLUSTER PROCESSING SYSTEM,” assigned to Applied Komatsu Technologies, Inc. of Santa Clara, Calif., and incorporated above by reference. The use of a modular processing system is disclosed, with substrate movement exterior of processing islands performed by conveyors or robots on tracks. Substrate movement interior of processing islands is performed by a substrate transporter. In this type of system, the transporter may move a substrate into or out of a processing chamber, after which the transporter may stay resident in either load lock.
Similarly, chamber configurations designed for the processing of relatively small semiconductor wafers are not particularly suited for the processing of these larger glass substrates. The chambers must include apertures of sufficient size to permit the large substrates to enter or exit the chamber. Moreover, processing substrates in the process chambers typically must be performed in a vacuum or under low pressure. Movement of glass substrates between processing chambers, thus, requires the use of valve mechanisms which are capable of closing the especially wide apertures to provide vacuum-tight seals and which also must minimize contamination.
Furthermore, relatively few defects can cause an entire monitor formed on the substrate to be rejected. Therefore, reducing the occurrence of defects in the glass substrate when it is transferred from one position to another is critical. Similarly, misalignment of the substrate as it is transferred and positioned within the processing system can cause the process uniformity to be compromised to the extent that one edge of the glass substrate is electrically non-functional once the glass has been formed into a display. If the misalignment is severe enough, it even may cause the substrate to strike structures and break inside the vacuum chamber.
Other problems associated with the processing of large glass substrates arise due to their unique thermal properties. For example, the relatively low thermal conductivity of glass makes it more difficult to heat or cool the substrate uniformly. In particular, thermal losses near the edges of any large-area, thin substrate tend to be greater than near the center of the substrate, resulting in a non-uniform temperature gradient across the substrate. The thermal properties of the glass substrate combined with its size, therefore, makes it more difficult to obtain uniform characteristics for the electronic components formed on different portions of the surface of a processed substrate. Moreover, heating or cooling the substrates quickly and uniformly is more difficult as a consequence of its poor thermal conductivity, thereby reducing the ability of the system to achieve a high throughput.
As noted above, efficient production line processing requires rapid movement of the glass substrates from one work station or processing island to another. Large glass substrates are particularly cumbersome and fragile, further complicating this process.
SUMMARY
The present invention allows large glass substrates to be rapidly moved within a processing station or from one processing station to another. Such movement occurs such that drives in different chambers are synchronized to move the glass substrates on shuttles at appropriate times. In systems according to one embodiment of the invention, at least a first and second chamber are provided. Typically, the first chamber is a load lock and the second chamber is a processing chamber. The processing chamber may include an inspection station, a CVD chamber, a PECVD chamber, a PVD chamber, a post-anneal chamber, a cleaning chamber, a descumming chamber, an etch chamber, or a combination of such chambers. The load lock may be employed to heat or cool the substrate. Two load locks may be employed, one to perform heating and the other to perform cooling. The load locks each include a platen for supporting the substrate.
A substrate transfer shuttle is used to move a substrate along a guide path defined by, e.g., guide rollers. Drive mechanisms are employed, often between chambers, to drive the shuttle along associated portions of the path. A control system is provided which powers the drive mechanism adjacent the first chamber to drive the substrate transfer shuttle from a first position toward a second position and through an intermediate position. At the intermediate position, the substrate transfer shuttle begins to engage and induce movement of the drive mechanism adjacent the second chamber. The control system receives an input caused by the induced movement of the drive mechanism adjacent the second chamber, this input indicative of the substrate transfer shuttle having moved a predetermined distance beyond the intermediate position. The input may then be used to synchronize movement of the substrate transfer shuttle from the first chamber to the second chamber. Such synchronization may include reducing power to the drive mechanism adjacent the first chamber and/or powering the drive mechanism adjacent the second chamber.
Implementations of the invention may include one or more of the following. Several process chambers may be employed, and the movement of the shuttle into each may be synchronized in the manner above. The synchronization may occur such that the shuttle moves in a forward direction and in a reverse direction. More than one shuttle may be employed, and the multiple shuttles may operate independently.
Sensors may be advantageously employed to detect the shuttle position and thereby to provide a feedback to the drive mechanisms directing the same to change, e.g, drive movement if an error in positioning is detected. In this way, an error correction scheme may be implemented which is distributed ov
Blonigan Wendell T.
Kurita Shinichi
Tiner Robin L.
White John M.
Applied Komatsu Technology Inc.
Fish & Richardson PC
Keenan James W.
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