BACKGROUND ART AND TECHNICAL PROBLEMS Machines for polishing and cleaning workpieces in the electronics industry are generally well known. For example, semiconductor wafers, magnetic disks, and other workpieces often come in the form of flat, substantially planar, circular disks. In the manufacture of integrated circuits, semiconductor workpieces are sliced from a silicon ingot and prepared for further processing. After each workpiece is sliced from the ingot, it must be thoroughly polished, cleaned, rinsed, and dried to remove debris from the surface of the workpiece. Thereafter, a series of steps are performed on the workpiece to build the integrated circuits on the workpiece surface, including applying a layer of microelectronic structures and one or more layers of a dielectric material. Typically, after the layers are fabricated on the workpiece surfaces, the workpieces are planarized to remove excess material and imperfections. After each processing step, it is often desirable to thoroughly clean, rinse, and dry the workpiece to ensure that debris is removed from the workpiece.

Additionally, many workpiece processing systems contain processors into which workpiece processing information can be loaded and stored. Information loaded into these processors often includes user maps (locations of workpieces within the cassettes), the workpiece's queue or recipe (the processing each workpiece is to receive from the system), and other workpiece information. In prior art CMP systems, this information temporarily exists in the system's processor and is lost upon the catastrophic failure of the system.

The processing of a workpiece, from the initial formation of the silica surface to the final shipment of the product, encompasses multiple tasks on multiple workpiece processing systems.

A workpiece commonly will be processed on 5 workpiece processing systems before it is finished. The catastrophic failure of any of these systems can result in the scrapping of all the

workpieces on the system. When prior art CMP systems fail, most of the workpieces are removed from the affected systems and scrapped. Often some of the workpieces removed were not damaged during the catastrophic failure. Scrapping the Undamaged workpieces. especially those which have already completed most of the production stages, can significantly increase the unit cost of producing workpieces and disrupts production. When all the workpieces on a workpiece processing system are scrapped, the productive capacity of subsequent systems is also affected. Systems which would subsequently process the workpieces are unexpectedly idled.

Due to the associated start-up costs and time involved, many idled systems remain fully powered under continuous operator supervision. Additionally, these production delays often result in shipping delays. Thus, scrapping all the workpieces on a system can often result in idled systems, production delays, cost escalations, and late shipments.

The machinery used in these numerous processes require large quantities of power. Often, Uninterruptable Power Supplies (UPS) are utilized to prevent the catastrophic failure of similar production systems. When commercial power to a facility is interrupted, UPS systems commonly utilize batteries to provide the power necessary to continue operations while emergency generators come on-line. However, due to the extremely high power demands of workpiece processing systems, UPS systems which can supply these loads are not readily available or practical. Thus. workpiece processing systems are currently not protected by UPS systems and are extremely susceptible to power failures causing catastrophic equipment shutdowns.

To further complicate mattes, current systems do not provide for the tracking and mapping of workpieces throughout the multiple locations within a processing system. Many workpiece processing systems often include an area where packs of incoming and outgoing workpieces are contained in cassettes. To ease the transfer and storage of workpieces, 25 slot cassettes are commonly used, with one workpiece per slot. Present systems can not recall, upon a catastrophic system failure, which workpieces in a cassette have been processed and which are awaiting processing. Additionally. a workpiece can be"in transit"when it has been removed from a cassette and is either awaiting system processing, has been partially processed and is awaiting subsequent processing, or has finished processing and is awaiting return to a cassette. Other locations include the system's polishing, cleaning, and drying areas. Thus, at any given moment, workpiece may be located in any number of processing stations within a large system. Present systems can not recall the status and location of these workpieces.

Therefore. since current systems do not allow a system operator to determine which workpieces were awaiting processing, were processed, or were in the tool at the time the tool catastrophically failed, a system for monitoring the position and processing status of a plurality of workpieces within a single or multi-stage tool is needed.

SUMMARY OF THE INVENTION In accordance with the present invention, a non-volatile system for restoring the location and status of all the workpieces within a workpiece processing system is provided which overcomes the noted shortcomings of the prior art. Additionally, the present invention provides a scheme whereby the catastrophic effects of a power loss in a workpiece processing system are reduced.

One advantage of the present invention is to provide a system for recalling the status and location of a plurality of workpieces within a workpiece polishing, cleaning, and drying system upon the cessation of operations of the system for any reason. Recalling the status and location of these workpieces allows a system operator to precisely determine which workpieces can be salvaged and which must be scrapped.

Another advantage of the present invention is to provide a real-time system for recalling the status of a plurality of workpieces within an appropriate system at any time upon input by an operator. This feature allows an operator to determine the processing status of any given workpiece at any time without having to interrupt the operation of the system.

The present invention also provides a system for storing and reconstructing user maps for workpiece runs still within cassettes. Storing and recovering the user maps allows the operator to quickly resume the processing of salvageable workpieces without having to reload the workpiece information into the system. The user maps may contain detailed information about which runs are remaining for each workpiece within a plurality of cassettes.

Another aspect of the present invention is the storage and reconstruction of the workpiece queue. This information contains the recipes which were programmed to be run on each of a plurality of workpieces. Storing and reconstructing this information drastically reduces the restoral time of the system following a catastrophic error.

Another advantage of the invention is that it provides a technique for monitoring and tracking the status of a plurality of workpieces as they are processed by the individual stations within a workpiece processing system.

The ability to perform real-time updates of the recovered information is an additional feature of this invention. Real-time updating by the operator of the tool ensures the tracking system is synchronized with the activities and decisions of the operator. Should an operator, for any reason, decide to remove an additional workpiece or continue processing upon workpieces, this feature allows the operator to update the status information retained by the present invention to reflect the current state of the tool and the workpieces therein.

The present invention may also incorporate an operator interface such as a flat panel touch screen. The touch screen preferably presents status information of virtually every relevant aspect of the system and the workpieces therein to facilitate operation, maintenance, trouble-shooting, and the like.

The above and other advantages may be carried out by a catastrophic error recovery system which stores, updates, and restores information for a plurality of workpieces within a workpiece processing system having a workpiece processing tool, a suitable processor for controlling the tool, and a non-volatile, real-time workpiece information storage and retrieval device which receives, updates, and restores workpiece information upon query.

BRIEF DESCRIPTION OF THE DRAWING FIGURES The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like numerals generally denote like elements, and: Figure 1 is a top schematic plan view of an exemplary embodiment of an integrated machine for polishing, washing, rinsing, spin-drying, and unloading workpieces for which the present invention stores and retrieves workpiece status information ; Figure 2 is a block diagram showing the interface of a workpiece processing system with a suitable processor within which catastrophic error recovery is stored, processed, and retrieved ; and Figure 3 is a flow diagram of an exemplary error recovery process that may be implemented by the present invention.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS Referring now to Figure 1, an exemplary tool for which the present invention stores and retrieves status information is a tool 10 suitably configured to perform Chemical Mechanical Polishing (CMP), cleaning, rinsing, and drying of semiconductor workpieces. For a more detailed discussion of an exemplary tool configured to perform such processing of semiconductor

workpieces. see. for example U. S. Patent Application Serial No. 08/926, 700, entitled"Combined CMP and Workpiece Cleaning Apparatus and Associated Methods", filed September 10,1997 in the name of Gonzales-Martin, et. al. It should be noted that the present invention may be applied in the context of any number of workpiece processing systems and that the embodiment shown and described herein is not intended to limit the scope of the present invention in any manner.

The tool 10 includes a load and unload station 12 configured to accommodate a plurality of workpiece cassettes 13 to permit substantially continuous operation of the tool 10. A sensor assembly or workpiece mapping system is suitably configured throughout the tool 10. The workpiece mapping system includes a plurality of sensors and the associated hardware necessary to track the location and status of multiple workpieces within the tool 10. Upon the loading of a cassette into the tool 10 at the load and unload station 12, the workpiece mapping system initially determines which locations within a cassette 13 contain workpieces. The operator is then presented with this information on a suitable display. The operator then loads workpiece processing information into the tool by an appropriate data entry device such as a touch screen display, alphanumeric keyboard, or the like.

After the processing information is loaded into the tool 10, workpiece processing begins.

A robot arm 14 individually selects workpieces contained within a cassette 13. The robot arm 14 removes a workpiece from a cassette 13 and inserts the selected workpiece through an air knife 16 into the index station 18. Within the index station 18, the workpiece is placed upon one of a plurality of load cups 20 residing on index table 22. Upon the loading of a workpiece on a load cup 20. the index table 22 rotates so that an empty load cup 20 is aligned with the air knife 16. Once all the load cups 20 contain workpieces. the workpieces are transported by a transport assembly (not shown) to the polishing station 24. The workpieces are positioned above and in contact with a polishing table 26. The workpieces are polished and planarized according to preset recipes. Upon completion of the polishing cycle, the transport assembly returns the workpieces to the index station 18 where the workpieces are placed in unload cups 28. Once placed in unload cups 28, a flipper arm 30 removes the polished workpieces from the index station 18 and transfers them to a track in the cleaning station 32. After the workpieces are cleaned, they are then stacked by the robot arm 14 into a cassette 13. A plurality of sensors are suitably situated within the tool 10 to track the processing status and location of each workpiece throughout the workpiece processing system. These sensors are preferably located at the robot arm. the load cups. the rinse stages, and the like. For a more detailed discussion of an exemplary

location of such sensors in a machine suitably configured to perform CMP of semiconductor workpieces. see, for example U. S. Patent Application Serial No. 08/926, 700, entitled"Combined CMP and Workpiece Cleaning Apparatus and Associated Methods". filed September 10,1997. in the name of Gonzales-Martin, et. al.

Referring now to Figure 2, the tool 10 may be controlled by a suitable processor 40. The processor 40 receives the plurality of sensor outputs and controls the operation of the tool 10 as determined by operator input and preprogrammed software or hardware applications. The processor may be part of a larger controller or central processing unit. Additionally, the processor may include any number of suitable memory and processing elements adapted to perform the various processes and programs that may be realized in the form of software instructions and the like. The processor may also perform additional functions unrelated to the present invention. For the preferred embodiment, the processor is also connected to an SEMI Equipment Communications (SECS) interface 42 which converts the instructions and data from the processor 40 into the SEMI format for transfer to an Equipment Virtual Controller (EVC) 44.

The EVC 44 is preferably a non-volatile storage system appropriately configured to receive, store, and process workpiece position and status information from the tool 10. The preferred embodiment of the tool 10 may contain more than 100 workpieces located throughout the tool 10. One exemplary embodiment is configured with a 122 workpiece capacity. At the load and unload station 12, multiple workpieces may be awaiting processing or may be awaiting removal from the tool 10. Additionally, a plurality of workpieces may also be undergoing processing at any one of the numerous polishing or cleaning stations contained within the tool 10. Thus, an essential feature of the present invention is the ability to track the location of a plurality of workpieces within the tool 10 and restore the location information after an interruption of workpiece processing in the tool 10. Upon restoral of operations of the tool 10 following an interruption, for example from a power failure, the processor 40 is configured such that it queries the EVC 44 for workpiece status data before it continues normal operations.

During normal operations, the processor 40 continually receives from the workpiece mapping system the current status and position of workpieces within the tool 10. Parameters routinely updated within the processor include the specific position of each workpiece within the tool 10. the elapsed processing time for a particular operation of the tool upon a workpiece. and the like. These parameters are utilized by the processor 40 to control the operation of the tool and are provided to the EVC 44 on a continual basis. The EVC 44 receives the parameters and updates and stores the workpiece status and position information. Therebv. the EVC 44 contains

the current status and position of each workpiece within the tool 10.

The processor begins receiving workpiece status information upon the insertion of a cassette containing a plurality of workpieces into the tool. The cassette name is entered into the processor. The workpiece mapping system is preferably utilized to determine the number of workpieces within the cassette and to assign a slot identification to each workpiece. For purposes of the present embodiment, the cassette nominally holds 25 workpieces in 25 slots. The mapping information is then sent to the processor. The cassette name and slot identification information are then utilized to track and record the position and status of each workpiece. Upon the initial loading of a cassette containing workpieces, the operator may assign a recipe to each workpiece or to a particular batch of workpieces. The recipe designates the processing the workpiece is to receive from the tool. Additional status variables can be assigned to each workpiece and updated as needed. These status variables may include: the station identification (initially set to correspond to the slot identification), the state identification, run number, segment number, segment time, elapsed time, and carrier offset. Each of these variables may be periodically sent from the processor to the EVC where they are stored and retrieved upon a catastrophic failure.

The station identification is preferably a three digit number ranging from 001 to 122. Each number designates a particular location within the tool. For example: 010 = Input Cassette 1, Slot 10; 101 = Robot; 119 = unload flipper, and so forth. Thus, as the workpiece is processed by the tool, the station identification is updated to reflect the workpiece's current position. In the preferred embodiment, each station identification can be assigned to only one workpiece at any one time.

The state identification is preferably a three digit number ranging from 200-222 which represents the current status of an individual workpiece. The preferred tool 10 can process a plurality of workpieces at each processing station : thus, multiple workpieces can simultaneously possess the same state identification. For example, the index table 22 contains a plurality of load cups 20, each of which may contain a workpiece. The workpieces in the load cups, while awaiting transport to the polishing station, can each be assigned a particular state identification.

For example, state identification 204 may represent"waiting to be picked up by the carrier".

Other state identifications may signify the following states: waiting for a polishing event to begin or end; waiting for a cleaning event to begin or end; waiting to move to the cleaning station: and the like. Thus, when a catastrophic failure occurs, the state identification indicates the last known status of each workpiece.

The run number is used to designate the workpiece by processing batch. This number is workpiece dependent and does not change as the workpiece is processed by the tool.

The segment number is a sequential number representing a particular intermediate step during primary polishing and final polishing of a workpiece. The polishing of a workpiece commonly consists of multiple segments which may include different down forces, pressures, time spans, and/or the like. The segment number preferentially identifies a particular segment with predetermined down forces, pressures, and similar variables.

The segment time represents the cumulative time a workpiece spends in a segment or group of independent sections of a workpiece processing recipe in seconds.

The elapsed time represents the actual time spent in a segment in seconds.

The carrier offset represents the down force the carrier applies to each workpiece. Such downforce is applied to facilitate polishing of the workpieces upon the rotating polishing pad.

The combination of these and possibly other variables allow the operator to precisely know at which stage of polishing, cleaning, drying, storing, or the like a particular workpiece was at when a catastrophic failure occurred. These variables are updated in the EVC at an interval sufficient to allow recovery of workpiece status and position information on an as needed basis.

The variables are preferably updated at least once every 3 seconds and, most preferably, at least once every 100 milliseconds.

Figure 3 shows the process flow the processor 40 and EVC 44 follow in recovering workpiece status and position information. Upon initialization of the tool (block 50) the processor 40 instructs the SECS interface (block 52) to establish a communications link between the EVC and the SECS interface. The processor may wait a predetermined period of time for the link to be established. If the link is not established, the processor alerts the operator of the unavailability of recovery information from the EVC. If the link is established. setup continues.

For the preferred embodiment, the SECS interface establishes a communications link by sending a"2I" (request for recovery information) message to the EVC. The EVC will preferably send a reply if the link is established. Meanwhile, the processor preferably waits 30 seconds to receive a"51" (recovery information available) reply status message from the SECS interface. The SECS interface preferably generates the"5I"reply status message upon receipt of a reply from the EVC. If the"51"reply status message is not received by the processor within the 30 second time limit, the processor increments a counter and resends the'2I"request. After sending three consecutive '2I"requests without receiving a"51"reply status message, the processor sets the

EVC status flag to unavailable. alerts the operator to the lack of response from the EVC, and continues startup without recovery information. If a communications link exists between the EVC and the processor, the EVC will respond to the"21"-query and the SECS interface will preferably send a 4'51"status message to the processor. Upon receipt of a"51"message, the processor sets an EVC status flag to iicommunicating".

Upon the establishment of a communications link between the processor and the EVC the processor examines the response from the EVC (block 58). If recovery data is not available (block 60), the processor notifies the operator of the unavailability of recovery data (block 56).

If recovery data is available, setup continues (block 62). For the preferred embodiment, if recovery data is not available the setup of the tool continues without recovery data. If recovery data is available, the processor preferably awaits receipt of a"I L" (recovery data) message from the SECS interface and starts a timeout counter. During this time, the SECS interface will await the EVC recovery data and upon receipt convert it into a format suitable for the processor. If recovery data is not received from the EVC within the preferred time interval, set up will continue without recovery data.

Once recovery data is received it is sent to the processor where it is decoded (block 62) and validated (block 64). If the data is not valid, the processor increments a retry counter (block 66).

If the retry counter indicates a predetermined number of retries have occurred (block 68), the processor notifies the operator (block 56) that recovery data is not available and setup continues without recovery data. If the predetermined number of retries have not occurred (block 68), the EVC is queried for recovery data (block 58).

Upon the receipt of valid data (block 64), the processor will preferably send a message to the EVC which notifies the EVC that valid data has been received (block 70). In the preferred embodiment, the data sent to, stored, and received from the EVC is in the format of a table wherein each row signifies a distinct workpiece and each column provides information relative to that workpiece. The operator of the preferred embodiment can display the received data in the tabular format, in a graphical presentation, or some combination of graphical and alphanumerical presentation. Regardless of the format selected, the data can be presented on a suitable monitor, printer, or the like.

For the preferred embodiment the data is preferably presented in a graphical presentation on a display monitor suitably located to allow the operator to observe and control the tool. To graphicallv present the recovered data, the processor reconstructs (block 72) the workpiece position information obtained from the recovered tabular data and preferably displays the

workpiece position information on a graphical workpiece verification screen (block 74). A preferred embodiment of a workpiece verification screen graphically displays the various locations within the tool a workpiece could be situated. and indicates the identity and status of each workpiece therein. The operator can then verify the accuracy of the recovery data versus the actual location of workpieces within the tool and decide whether to modify the workpiece positions shown on the workpiece verification screen (block 76). Modifications could be necessary when the operator manually removes workpieces from the tool, when workpieces are not positioned consistently with recovery data, and the like. When workpiece positions are modified by the operator, the workpiece recovery data obtained from the EVC is modified (block 78), reconstructed by the processor (block 72), and redisplayed (block 74). For the preferred embodiment, the operator during this verification phase can preferably display workpiece positions anywhere within the tool including the input and output cassettes. Additionally, for the preferred embodiment the operator can preferably verify the cassette maps, workpiece status variables, and the like to achieve any desired workpiece position and status configuration. Once the recovered data matches the desired configuration and additional modifications to the recovered data are not required (block 76), workpiece verification can be exited (block 80).

Upon exiting workpiece verification, the modified workpiece recovery data contained within the processor is sent to the EVC to update the EVC data (block 82). During the previous steps the workpiece recovery data had been modified within the processor. Block 82 sends this modified data to the EVC for updating and storage. If the EVC data can not be successfully updated (block 84) the operator is notified of the lack of response from the EVC and setup continues without recovery data (block 86). For the preferred embodiment, the processor awaits a predetermined time period for the EVC to signal receipt of the updated recovery data. If the timeout period elapses, the processor may attempt to resend the data a predetermined number of times. Additionally, for the preferred embodiment the EVC upon receipt of the recovery data verifies the received data is in the proper format and is valid data. If the updated recovery data is not valid, the EVC signals the processor to resend the updated recovery data. If after a predetermined number of tries the EVC has not received valid updated recovery data. the operator will be notified and set up will continue without recovery data.

If the EVC update is successful (block 84), the processor preferably displays an auto unload screen (block 88) or similarly queries the operator on whether the processor should commence the unloading of workpieces identified by software and operator inspection. Upon operator direction, the tool will then unload the designated workpieces (block 90).

Upon unloading the designated workpieces. the tool preferably proceeds to process the workpiece process information (block 92). This process information includes the desired recipe for each workpiece, the run time, and the like. Once the-workpiece process information is determined, the processor displays the run main polish screen (block 94). The run main polish screen preferably displays the processes to be applied to each workpiece. For workpieces which had not left their respective input cassette prior to the tools shutdown, these parameters will not change. For other workpieces, the processing time may change, the remaining processing steps may vary, and the like. If the displayed information is correct, the operator preferably presses a start button or the like (block 96) which directs the processor to resume processing the workpieces according to the recovery data (block 100). Thereafter, workpiece processing continues under normal operating conditions (block 102). If the displayed information is incorrect, the start button is not pressed (block 96), workpiece processing proceeds without recovery information (block 98) and normal operations resume (block 102).

Once a workpiece is finished being processed, the tool inserts the workpiece into an output cassette. When the output cassette is removed from the tool, the associated workpiece information is purged from the processor and can be purged from the EVC. For the preferred embodiment, all workpiece information is preferably purged from the EVC upon the removal from the tool of the cassette containing the workpiece. However, the present invention can be adopted to permanently store such workpiece information, or to provide such workpiece information to subsequent tools as the need arises.

In accordance with a further aspect of the present invention, the tool 10 contains a touch screen display (not shown) suitably employed to allow the operator to monitor, reconfigure. troubleshoot, and otherwise update workpiece position and status information. More particularly, a touch screen display may be configured to display, preferably in three dimensions, a graphical representation of the various operational features of the tool 10 and the location and status of workpieces therein. Additionally, touch screen buttons may be included which may locate workpiece positions, load default recovery information, exit/save changes to recovery information, open the load door, open the unload door, open the process door, select a cassette map, increment, decrement, clear, and set entries. These buttons allow the operator to enter and reconfigure the workpiece position and status as necessary. I-However the present invention is not to be construed as being limited to only a touch sensitive screen. Any sort of instruction input means, whether it be designated keys, alphanumeric keyboard entries. or the like are covered by the present invention.

Although the present invention has been described in conjunction with appended drawing figures, it will be appreciated that the invention is not so limite. Various additions, deletions, substitutions, and rearrangement of parts and processing steps may be made in the design and implementation of the error recovery system without departing from the spirit and scope of the present invention, as set forth more particularly in the appended claims.