Material or article handling – Apparatus for moving material between zones having different...
Reexamination Certificate
1998-12-02
2001-05-29
Hess, Douglas (Department: 2167)
Material or article handling
Apparatus for moving material between zones having different...
C414S749200, C414S935000, C414S941000, C029S025010
Reexamination Certificate
active
06238160
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to methods and techniques for processing semiconductor devices, such as semiconductor wafers, and deals more particularly with a method for transporting and electrostatically chucking the wafer for processing within a processing chamber.
BACKGROUND OF THE INVENTION
Semiconductor wafers used to fabricate integrated circuits are processed in vacuum chambers using common semiconductor processing techniques, such as CVD, sputtering and etching. The wafer must be securely held in a fixed position within the chamber, and means must be provided to carefully control the temperature of the wafer. In many cases, a cooling gas, such as helium is supplied to the backside of the wafer which serves as a heat transfer medium to assist in controlling wafer temperature.
Various techniques have been used in the past to hold the wafer in a desired position within the chamber. Early techniques involved mechanically clamping the topside of the wafer while providing cooling gasses to the backside; this approach is sometimes referred to as “top side clamping”, but has not proved particularly effective, in large part because it suffers from the disadvantage of causing non-uniformity and particle inconsistencies at the extreme edge of the wafer.
More recently, electrostatic clamping has found increasing use. This technique makes use of the electrostatic attraction between objects of different electrical potentials, and commonly employs an electrostatic chuck as the device for providing electrostatic clamping forces. Electrostatic chucking is based on the forces of attraction between the charged plates of a capacitor. As in other types of wafer clamping and chucking, cooling gasses to control wafer temperature are supplied to the backside of the wafer, consequently the clamping force resulting from electrostatic forces must be sufficient to overcome the backside pressure on the wafer resulting from application of the heat transfer medium. The electrostatic chuck can be thought of as a capacitor with a conductive plate (a lower electrode fixed within the processing chamber), an insulating layer (a coating on the electrode), and another conductive plate (the wafer). In effect, the chuck is a parallel plate capacitor with a dielectric spacer. In its simplest form, this type of electrostatic chuck is referred to as a unipolar or monopolar electrostatic chuck. A unipolar electrostatic chuck is simply a conducting electrode with the wafer being employed as one of the conducting plates. In order to establish a complete circuit, an electrical connection to the wafer is required.
Currently, electrostatic chucking methods use the gas plasma within the chamber as a conductor which completes the electrical circuit necessary to provide the electrostatic clamping force. A significant drawback of this method is the fact that the actual clamping force is not applied to the wafer until the wafer has been charged and the plasma has been generated in the chamber, the combination of which results in “chucking” the wafer on the electrode. Although an electrical conductor could be used to contact the wafer in lieu of the electrically conductive plasma, such contact could have serious consequences in terms of process reliability and reproducibility. After the wafer is electrostatically “chucked”, the desired process is carried out in the chamber, following which it is necessary to unclamp the wafer. Wafer unclamping is achieved by removing the plasma from the chamber and bleeding off the electrical charge existing in the wafer; this step is commonly referred to as “de-chucking” the wafer. The speed and effectiveness of de-chucking are highly dependent upon the particular processes that have been previously carried out in the chamber. Simply turning off the voltage source to the chuck electrode with the plasma still present will not always result in instantaneous de-chucking since some residual charge may remain in the wafer. In any event, in addition to less than optimal process repeatability, the time required for chucking and de-chucking the wafer necessarily increases the overall time required to process a particular wafer, and thus reduces wafer throughput to the system.
It would therefore be desirable to provide an electrostatic chucking method which is capable of chucking and de-chucking the wafer without the need for using the plasma within the chamber to complete the circuit necessary for creating the electrostatic chucking force. The present invention is directed to satisfying this requirement.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a method is provided for transporting and electrostatically chucking an electrically conductive workpiece such as a semiconductor wafer for processing in a chamber. The method includes loading the wafer onto an arm or carrier using a first electrostatic force to attract the wafer to the carrier; transporting the wafer from a staging area to the processing chamber using the carrier; removing the first electrostatic force whereby to release the wafer from the carrier; depositing the wafer onto an electrically conductive substrate; creating a second electrostatic force between the substrate and the wafer which causes the wafer to be electrostatically chucked onto the substrate; then, following processing of the wafer in the chamber, removing the second electrostatic force and loading the wafer onto the carrier using the first electrostatic force to attract the wafer to the carrier; and, transporting the wafer from the chamber back to the staging area using the carrier.
According to another aspect of the invention, a method is provided for transporting and electrostatically chucking an electrically conductive workpiece such as a semiconductor wafer for processing in a chamber, comprising the steps of: loading a wafer onto a carrier; charging the wafer with a first electrical polarity; transporting the wafer from a staging area to a processing chamber using the carrier; charging an electrically conductive substrate within the chamber with a second polarity opposite of the first polarity; loading the charged wafer onto the oppositely charged substrate; holding the wafer on the substrate using an electrostatic force; then, following processing in a chamber, reversing the polarity of the electrical charge on the substrate, thereby creating an electrostatic repulsion force between the wafer and the substrate; loading the wafer onto the carrier; and, transporting the wafer from the processing chamber area back to the staging area using the carrier.
Accordingly it is the primary object of the present invention to provide a method for transporting and an electrostatically clamping a wafer within a semiconductor processing chamber which eliminates the need for utilizing gas plasma within the chamber as a conducting medium for creating electrostatic clamping forces.
Another object of the invention is to provide a method of the type mentioned above which is substantially decreases the time required for chucking and de-chucking the wafer within the processing chamber.
A further object of the invention is to provide a method as described above which allows transport of the wafer without the need for applying mechanical clamping forces to the wafer.
A still further object of the present invention is to provide a method of the type described above which provides highly repeatable and consistent results.
These, and further objects and advantages of the present invention will be made clear or will become apparent during the course of the following description of a preferred embodiment of the present invention.
REFERENCES:
patent: 4645218 (1987-02-01), Ooshio et al.
patent: 5258047 (1993-11-01), Tokisue et al.
patent: 5315473 (1994-05-01), Collins et al.
patent: 5444597 (1995-08-01), Blake et al.
patent: 5485644 (1996-01-01), Shinbara et al.
patent: 5792304 (1998-08-01), Tamura et al.
patent: 5818682 (1998-10-01), Loo
patent: 5932014 (1999-08-01), Hayashi et al.
patent: 6032083 (2000-02-01), Oosawa
patent: 6048434 (
Hsieh Tsung-Chi
Hwang Yuan-Ko
Fischetti Joseph A.
Hess Douglas
Taiwan Semiconductor Manufacturing Company, Ltd'
Tung & Associates
LandOfFree
Method for transporting and electrostatically chucking a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for transporting and electrostatically chucking a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for transporting and electrostatically chucking a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2559081