Patent Application
20090022572
This invention relates to the field of wafer deposition and, in particular, to a sputtering system combining a cluster tool with linear sources.
Deposition systems are used to deposit a substance on a substrate. Several types of conventional deposition systems are currently implemented. One type of conventional deposition system implements magnetron sputtering. Sputtering, in general, is the process of ejecting atoms from a solid target material, the target or cathode, to deposit a thin film on a substrate. A magnetron enhances this operation by generating strong electric and magnetic fields to trap electrons and improve the formation of ions from gaseous neutrals such as argon. The ions impact the target and cause target material to eject and deposit on the substrate.
One exemplary deposition system is a cluster tool. Cluster tools include a central robot having several chambers radially extending from the centrally located robot. The deposition chambers include a stationary deposition source. In these cluster tools, a single wafer or, at most, two wafers, are moved among the chambers by the central robot, the wafer positioned under a stationary cathode.
Another exemplary deposition system is an in-line deposition system. In in-line deposition systems, several sources are arranged linearly. A pallet of wafers are passed under each of the sources in-line. The length of these in-line deposition systems is typically very large (on the order of 150 feet long).
The Kurt J. Lesker Company makes a combined multi-chamber cluster tool system (OCTOS® Cluster Tool Deposition System), which processes single substrates having a size of 6″×6″ or smaller.
Embodiments of the invention are described by way of example with reference to the accompanying drawings, wherein:
The following description sets forth numerous specific details such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of several embodiments of the present invention. It will be apparent to one skilled in the art, however, that at least some embodiments of the present invention may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram format in order to avoid unnecessarily obscuring the present invention. Thus, the specific details set forth are merely exemplary. Particular implementations may vary from these exemplary details and still be contemplated to be within the spirit and scope of the present invention.
Embodiments of the invention relate to a combined cluster tool and in-line deposition chamber. Embodiments of the invention also relate to a combined cluster tool and in-line deposition chamber having a redundant in-line deposition chamber. Embodiments of the invention also relate to a combined cluster tool and in-line deposition chamber configured to handle a pallet having wafers mounted thereon.
In one embodiment, the plurality of chambers 108-124 include a first deposition chamber 108, a second deposition chamber 112, a third deposition chamber 116, a fourth deposition chamber 120, a buffer chamber 124 and a combined rough and isolation chamber 128. In one embodiment, the buffer chamber 124 is configured to store a plurality of pallets. In one embodiment, one of the deposition chambers is a redundant chamber. Thus, a deposition process need not be shut down when one of the deposition chambers is cleaned. In one embodiment, the buffer chamber 124 includes elevators for storing the plurality of pallets. In one embodiment, the combined rough and isolation chamber 128 includes a rough chamber 128a and an isolation chamber 128b separated from one another with a valve 130 to maintain a vacuum. It will be appreciated that the actual number and type of chambers may vary from that illustrated and described. For example, fewer or greater than four deposition chambers may be provided. In another example, a buffer chamber need not be provided. In a further example, a heating chamber may be provided in addition to or in the alternative of the illustrated chambers.
In one particular embodiment, the first deposition chamber 108 is configured to deposit Al—Si, the second deposition chamber 112 is configured to deposit Ti—W, the third deposition chamber 116 is configured to deposit Cu, and the fourth deposition chamber 120 is a redundant chamber.
As will be described in further detail hereinafter, one or more of the deposition chambers 108-120 is an in-line deposition chamber.
The cluster chamber 104 includes a central robot 132. The central robot 132 is configured to move a pallet 136 among the chambers 108-128 through the cluster chamber 104. The central robot 132 is also configured to position the pallet 136 on a transport mechanism in one or more of the chambers 108-128 as described in further detail hereinafter. It will be appreciated that more than one robot may be provided in the cluster chamber and/or that the robot(s) may be configured to carry one or more pallets.
The pallet 136 is illustrated in the cluster chamber 104 in
In one embodiment, the pallet includes wafer pockets to receive wafers therein. In another embodiment, the wafers are positioned on a substantially flat pallet (e.g., without wafer pockets). In embodiments with a substantially flat pallet, the pallet may include pins or clips to hold the wafers in a predefined arrangement. In one embodiment, the pallet and wafers are electrically isolated. In one embodiment, the pallet and transport mechanism include an isolated anode. The anode serves as an anode to a deposition source in one or more of the chambers.
In one embodiment, the wafers are solar cell wafers or photovoltaic cell wafers. In one embodiment, the wafers are silicon. In one embodiment, the wafer has a substantially rectangular shape.
In one embodiment, the deposition system 100 is configured to make thin film solar cells. For example, the central robot 132 may be configured to transfer a glass sheet among the chambers 108-128 through the cluster chamber 104.
In use, wafers 140 are mounted on the pallet 136. In one embodiment, the wafers 140 are mounted on the pallet 136 in the cluster chamber 104. In another embodiment, the wafers 140 are mounted on the pallet 136 external the deposition system 100, and the pallet 136 enters the deposition system 136 through, for example, the isolation chamber 128b. The central robot 132 moves the pallet 136 from the cluster chamber 104 to the first deposition chamber 108. After processing is complete in the first deposition chamber 108, the central robot 132 retrieves the pallet 136 and moves the pallet 136 to the second deposition chamber 112 through the cluster chamber 104. Similarly, after processing is complete in the second deposition chamber 112, the central robot 132 retrieves the pallet 136 from the second deposition chamber 112 and moves the pallet 136 to the third deposition chamber 116 through the cluster chamber. The central robot 132 similarly transfers the pallet from the third deposition chamber 116 to the fourth deposition chamber 120, buffer chamber 124 and rough and isolation chamber 128. It will be appreciated that the process may vary from the process described above. It will also be appreciated that more than one pallet may be processed in the deposition system 100 simultaneously.
In general, one of the deposition chambers is redundant such that the system is not entirely shut down during servicing. In the above example, the fourth deposition is the redundant chamber. However, it will be appreciated that the fourth chamber may also be used as a deposition chamber (i.e., to deposit four layers on the substrate). It will also be appreciated that the first, second or third deposition chambers may instead be the redundant chamber and that the material deposited in each deposition chamber may vary depending on the servicing schedule.
The deposition chamber 200 includes a housing 204, a gate valve 208, a linear deposition source 212, transport rails 216 and a carrier 220. The housing 204 of the deposition chamber 200 is connected to the cluster chamber 104 of
In
The carrier 220 is movably mounted on the transport rails 216. The carrier 220 is configured to receive the pallet 136 and move the pallet under the linear source 212 via the transport rails 216. It will be appreciated that methods other than illustrated in
In one embodiment, a plurality of carriers may be provided to move one or more pallets. Similarly, the carrier 220 may be configured to move a plurality of pallets relative to the linear source. In one embodiment, the pallets pass over or under each other in the deposition chamber. For example, one pallet may pass over the transport rails and under the linear source at one level, while another pallet passes under the transport rails at another level. Similarly, the deposition chamber may include multiple deposition levels.
In use, the pallet 136 is positioned on the carrier 220 by the central robot 132 of
In one embodiment, the first deposition chamber 108 includes a linear source to deposit Al and Si; the second deposition chamber 112 includes a linear source to deposit Ti and W; the third deposition chamber 116 includes a linear source to deposit Cu; and the fourth deposition chamber 120 is a redundant chamber. The fourth deposition chamber 120 allows for continuous operation of the deposition system 100. In one embodiment, multiple sources may be provided in each chamber to allow for matching of deposition rates or PM cycles to compensate for different layer thicknesses, consumption rates and/or target thicknesses. It will be appreciated that the actual number of chambers, deposition materials, and number and type of sources, etc., may vary from that described above.
A typical cluster tool is a precision deposition tool designed for improved uniformity and process control by using a stationary source and isolated chambers, high overall equipment efficiency (OEE) by using redundant chambers, small footprint and low particle generation. A typical in-line tool is a mass deposition tool designed for high throughput (by multiple orders compared with cluster tools) operation with significantly higher downtime interval lengths, a large footprint, and moderately high particle generation. Combining advantages of the two systems provides, for example, high throughput, moderate uniformity precision, process isolation and high OEE with limited downtime interval lengths.
Advantages of the embodiments described above also include, for example, multiple wafers can be mounted on a pallet and processed under an in-line source without using a conventional in-line tool. When using pallets, the combined deposition system allows a higher OEE than a conventional in-line tool because the individual deposition chambers can be vented without stopping the process or venting the other chambers. The moving pallet allows use of a linear deposition source that is smaller in area than the pallet as opposed to a stationary source which must be the same size as the pallet. In addition, the coating uniformity on the pallet from the linear source is easier to control than a stationary deposition source covering the same pallet area. The functioning of the pallet to carry wafers can be separated from the functions of the pallet as a transport mechanism by itself or in combination with the carrier or transport mechanism. The deposition conditions within each deposition chamber can be easily varied compared to a conventional in-line tool. With open carriers and pallet trays, deposition can occur on both sides of the substrate. The combined system reduces facilities servicing compared to a conventional in-line tool because the overall footprint of the deposition system is reduced.
In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.
