Abstract:
A system for storing transporting and processing articles includes a plurality of transportable containers, each transportable container having an interior region adapted to receive a plurality of articles and data processing device provided on the transportable container for receiving, storing, transmitting and displaying information related to the articles received by the corresponding transportable container. A plurality of workstations are adapted to receive one of the transportable containers and to process selected ones of the articles. The workstation also verifies that at least one of the articles in the transportable container has arrived at the appropriate workstation and communicates with a central processing unit to receive and transmit status information and processing information, and to transmit information stored by the data processing device provided on the transportable container. The system may also include a storage station for receiving said transportable container, for providing communication between the data processing devices provided on the transportable container and the central processing unit, and for making a backup copy of the information stored by said data processing device.

Description:
CONTINUATION APPLICATION INFORMATION 
     This is a continuation-in-part of co-pending application Ser. No. 054,212, filed May 18, 1987, which is a continuation-in-part of application Ser. No. 686,444, filed Dec. 24, 1984, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to standardized mechanical interface systems for reducing particle contamination of semiconductor wafers during semiconductor processing. More particularly, the present invention relates to an apparatus for information processing in standard mechanical interface systems. 
     2. Description of the Related Art 
     A standardized mechanical interface (SMIF) system has been proposed to reduce particle contamination by significantly reducing particle fluxes onto wafers. This end is accomplished by mechanically insuring that during transport, storage and processing of the wafers, the gaseous media (such as air or nitrogen) surrounding the wafers is essentially stationary relative to the wafers and by inSuring that particles from the outside environment do not enter the immediate internal wafer environment. 
     The SMIF concept is based on the realization that a small volume of still, particle free air, with no internal source of particles, is the cleanest possible environment for wafers. Further details of one proposed system are described in the article &#34;SMlF: A Technology for Wafer Cassette Transfer and VLSI Manufacturing&#34;, by Mihir Parikh and Ulrich Kaemph, Solid State Technology, July 1984, pp. 111-115, and the above cross-referenced applications. 
     A SMIF system has three main components, namely, (1) minimum volume, dust proof transportable containers or boxes are used for storing and transporting wafer cassettes; (2) canopies are placed over the cassette ports of processing equipment so that the environments inside the boxes and the canopies become miniature clean spaces; and (3) doors on the boxes are designed to mate with doors on the interface ports on the equipment canopies and two doors are open simultaneously so that particles which may have been on the external door surfaces are trapped (sandwiched) between the doors. 
     In the proposed SMIF system, a box is placed at the interface port on top of the canopy at a desired processing station; latches release the boxed door and the interface port door simultaneously. A mechanical elevator lowers the two doors with the cassette riding on top into the canopy covered space. A manipulator picks up the cassette and places it into the cassette port/elevator of the equipment. After processing, the reverse operation takes place. 
     In typical processing environments today, &#34;clean rooms&#34; are established in which through filtering and other techniques attempts are made to remove particles which may cause contamination on semiconductor wafer surfaces. The SMIF concept is one way which has come under consideration for improving the processing environment over that available in clean rooms. 
     The proposed SMlF systems involve transporting cassettes of wafers from processing station to processing station inside the boxes. A given processing station may be located long distances from the preceding station. Further, the processing may be complex, involving a large number of steps different processing times, requiring the boxes including wafer cassettes to be stored between processing stations. Thus there is a need to identify the boxes containing wafers so that information about the wafers within the boxes can be processed. 
     The proposed SMIF systems, however, have not been fully satisfactory. The SMIF systems which have been proposed include boxes which may be marked with &#34;OCR&#34; or bar codes. This sort of proposed marking will identify the particular box, however, the user is unable to effectively include information with the box concerning the wafers within the box. Further, external markings of this nature do not serve to control physical access to the wafers in the box. Accordingly, there is a need for improved apparatus for information processing in SMIF systems. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a system for transporting and storing articles which provides improved tracking of the articles. 
     A further object of the present invention is to provide a system which centrally tracks articles undergoing processing and which centrally stores data regarding articles undergoing processing at a variety of locations. 
     Another object of the present invention is to provide a system which centrally controls the processing of articles being processed at a plurality of workstations so that the proper process steps and are performed in the proper sequence. 
     Another object of the present invention is to provide a system for processing articles which reduces or eliminates human decision making regarding the process to be performed at the point of processing. 
     These and other object of the present invention are provided by a system in which a plurality of containers are each provided with data storage and a communication link for reading and updating the stored data. A plurality of workstations each have a communication link which reads the data stored by the container and confirms that the articles in the container have arrived at the proper location. The workstation also reports that the articles have arrived and the status of the articles to a central data processor. The central data processor downloads processing information and the workstation then removes that articles from the container and processes the articles. After processing the workstation reports to the central data processor and updates the information stored by the container. 
     A system for performing a series of processing steps for an article in accordance with the present invention comprises: 
     a transportable container for the article, said transportable container including: 
     first interface means for controlling access to the article in said transportable container, and 
     container data processing means for receiving, storing and transmitting data relating to the identity and processing history of the article; 
     second interface means, provided at each workstation, for interfacing with said first interface means; 
     workstation data processing means, provided at each workstation, for receiving data from and transmitting data to said container data processing means, for processing the data received from said container data processing means, and for controlling said first and second interface means to permit access to the article in said transportable container based on a comparison of the processing history of the article and the identity of the workstation; and 
     central data processing means for receiving data from and transmitting data to each of said container and workstation data processing means and for processing data received from each of said container and workstation data processing means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective view of a SMIF system positioned adjacent processing equipment. 
     FIG. 2 is a schematic representation of a SMIF system employing the present invention. 
     FIG. 3A and 3B are circuit diagrams of one embodiment of the present invention. 
     FIG. 4 is an alternative embodiment of an apparatus according to the present invention. 
     FIG. 5 is a schematic diagram of a power supply according to the present invention. 
     FIG. 6 is a schematic representation of the mounting relationship of apparatus according to the present invention. 
     FIG. 7 is a block diagram of a system included on the transportable container in one embodiment of the present invention. 
     FIG. 8 is a chart used in explanation of part of the circuit of FIG. 5. 
     FIG. 9A, 9B and 9C constitute a flow chart used in the explanation of the processing system in accordance with the present invention. 
     FIG. 10 is an alternative flow chart for substitution for a portion of the flow chart of FIG. 9. 
     FIG. 11 is a flow chart used in the explanation of the processing system in accordance with the present invention. 
     FIG. 12 is a perspective view of a tray and transportable container of the inventory management system in accordance with the present invention. 
     FIG. 13 is a block diagram of an inventory management system in accordance with the invention. 
     FIG. 14 is a block diagram of one application of a system in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, a detailed description of the present invention is provided. 
     In FIG. 1, a semiconductor wafer processing station 100 is shown. A given semiconductor manufacturing process may include any number of processing stations such as the station 100 shown in FIG. 1. The stations are manufactured to handle processing steps such as the application of photo resist materials, the alignment of masks for exposing photo resist materials, the deposition of materials on semiconductor wafers, and so forth. 
     FIG. 1 shows a transportable container 10 for semiconductor wafers, or other articles to be processed, mounted on the processing station 100. The transportable container 10 is removeably engaged on the canopy 30 of the processing station 100 by a means 60 for engaging described with reference to FIG. 2. 
     The transportable container 10 is adapted for containing a cartridge 31 for holding a plurality of semiconductor wafers 32. The cartridge 31 is lowered into the processing station 100 without exposure to outside air. 
     According to the present invention, an intelligent data card 40 is mounted on the transportable container 10. The term &#34;data card&#34; as used herein refers to the portion of the present invention mounted on the transportable container 10, and at a minimum includes data storage means as described below. Further, mounted on the processing station 100 is a means 50 for communication with an electronic card 40 on a transportable container 10 engaged on the processing station 100. The means 50 for communicating with the data card 40 is connected to a data processor 20 on the processing station 100. The data processor 20 may include a display 21 such as an LED or liquid crystal display. Also, the data processor 20 may include a keyboard 22 for inputting data regarding for instance the control of the process. 
     In operation, an operator will carrier the transportable container 10 from a first processing station 100 to a second processing station 100 with the data card 40 attached to the container 10. The data stored in the data card 40 is communicated to the means 50 on the processing station 100 for communicating with the data card 40 when the transportable container 10 is engaged. The data from the data card 40 on the transportable container 10 is communicated through the means 50 to the data processor 20. In preferred embodiments as described below in more detail, the data processor 20 may also communicate to the data card 40 through the means 50. 
     FIG. 2 illustrates schematically the transportable container 10 engaged on the canopy 30 of a processing station. An engaging means 60 for engaging the transportable container 10 on the canopy 30 of the processing station is shown. The engaging means 60 includes a guide 61 on the canopy. Also, a tab 62 is formed on the transportable container 10. When the transportable container 10 is mounted on the guide 61 and fully engaged, the port 70 on the canopy 30 through which the cartridge of semiconductor wafers is lowered, is aligned with the transportable container 10. The data card 40 is mounted on the transportable container 10 along at least one side of the transportable container 10. The communicating means 50 is mounted adjacent the engaging means 60 in relationship with the card 40. The communicating means 50 is connected over communicating line 51 to the process controller 20 on the processing station 100. 
     FIG. 3A illustrates a circuit for mounting on the data card 40 in one embodiment of the present invention. FIG. 3B illustrates a communication means 50 for receiving data from the card 40 as shown in FIG. 3A. The circuit of FIG. 3A includes a timer/counter 41 and a storage means 42 such as a &#34;PROM&#34; or other stable storage device. The timer/counter 41 is connected to the storage means 42 across a communication bus 43. The timer/counter, when power is applied, generates addresses in sequence to the storage means 41 which outputs data through the light emitting diode 44 or other optical transmission means. In the embodiment of FIG. 3A, there is a single light emitting diode mounted on the data card 40. In this manner the timer/counter sequences through data locations in the storage means 41 and causes data to be output serially through the light emitting diode 44. 
     The communicating means 50 of FIG. 3B includes a photosensitive transistor 52 or other photo detector which responds to the data transmitted by the light emitting diode 44 to generate a signal across the control line 51 for communication with process control on the processing station 100. When the transportable container 10 is engaged on the engaging means 60 as shown in FIG. 2, the light emitting diode 44 and the photosensitive transistor 52 are aligned for optimum communication. 
     The data card 40 includes a power supply 45, such as a battery. The power supply will be applied to the timer/counter by a switch 46 which is engaged only when the transportable container 10 is fully engaged on the engaging means 60. 
     An alternative embodiment for a circuit on the data card 40 is shown in FIG. 4. The embodiment of FIG. 4 includes a microcomputer 101 or other data processing means and a static memory device such as a RAM 102. The microcomputer 101 communicates with the memory device 102 across the bus 103. The microcomputer 101 communicates with a transmitter 104 such as the light emitting diode 105. Also, the microcomputer 101 communicates with a receiver 106 such as the photosensitive transistor 107. The microcomputer receives power from power supply (described below) at +5 volts along line 108. The memory device 102 receives power from a battery along line 109. The storage device 102 likewise receives an enable signal on line 110 when the power supply supplying power to the microcomputer 101 is in operation. 
     The generation of the power supply voltage on line 108, the battery voltage on line 109 and the enable signal on line 110 is accomplished by the circuit shown in FIG. 5. 
     FIG. 5 shows a power supply 120 for mounting on the data card 40 used in conjunction with the circuit shown in FIG. 4. The power supply 120 is adapted to receive power through a transformer coupling device 121, when the transportable container 10 is engaged by the engaging means 60 on the processing station 100. The relationship of the transformer coupling is described in more detail with reference to FIG. 6. An AC signal is received from transformer coupling means 121 and converted to DC in an AD to DC converter 122, such as the bridge shown in FIG. 5. A voltage regulator 123 may be included to provide a stable voltage for the operation of the components on the data card 40. The output of the voltage regulator 123 is supplied as the power supply voltage to the microcomputer 101 across line 108 in the embodiment of FIG. 4. On the data card 40, a battery 125 is included. The battery voltage is slightly less than the output of the voltage regulator 123 on line 108. It is connected through the Shottley diode 126 to the node 127 which is likewise connect through a Shottley diode 128 to the power supply output on line 108. Node 127 is supplied as the battery voltage to the storage device 102 on line 109. 
     The memory enable signal (MENABLE) operates to enable the memory device 102 only when the power from the transformer coupled power 121 is turned on. For the embodiment shown in FIG. 5 including the rectifying optocoupler 141 and the circuit including R1 and C1 and the diode 142, the memory enable circuit is generated as it will be described with reference to FIG. 8. 
     The rectifying optocoupler 141 is a means for generating voltage on line 143 from the power supply such as battery 125 when the power from the transformer coupling device is off. When the power from the transformer coupling device turns on as indicated by line 200 of FIG. 8 at point 201, output on line 143 tends to drop which can be seen at point 301 of line 300 on FIG. 8. However, the speed at which the voltage on line 143, MENABLE can drop as determined by the time constant set by R1 and C1. Thus, the power on line 108 will reach the voltage necessary to drive the microcomputer 101 before the enable signal on line 110 reaches a level to enable the memory device 102. This prevents causing disruption of the data stored in the memory device before the power is completely up in the data card 40. 
     However, when power turns off at Point 202 in FIG. 8, the rectifying optocoupler 141 will supply a charging current across line 143 which will rapidly charge the capacitor C1 as can be seen at point 302 on line FIG. 8. Thus, the static RAM will be disabled very rapidly when power is turned off from the transformer coupling device 121. 
     A variety of other circuits for protecting the data stored in the memory device 102 can be devised as suits the particular embodiment of the data card 40 chosen by the user. 
     FIG. 6 shows one configuration for mounting the data card 40, such as the one described with reference to FIGS. 4 and 5, in communication with the communication means 50 for receiving the data from the data card 40 and transmitting data to the data card 40. When the transportable container 10 is fully engaged on the engaging means 60 and mounted on the canopy 30 of the processing station, the data card 40 and the communicating means 50 are aligned for communication. 
     As mentioned with reference to FIG. 5, a transformer coupling device 21 is mounted on the data card 40. Likewise, a mate transformer coupling device 131 is mounted on the communicating means 50. When the transportable container 10 is engaged on the engaging means 60 fully, the transformer coupling device 121 and its mate 131 are aligned so power is transmitted from the communicating means 50 to the data card 40 on the transportable container 10. 
     Also shown in FIG. 6 schematically are the transmitting means 104 and the receiving means 106 on the card 40. Mounted adjacent the transmitting means 104 on the communicating means 50 when the transportable container 10 is fully engaged is a mate receiving means 134 for receiving the data from the data card 40. Also a transmitting means 136 is mounted on the communicating means 50 so that it is adjacent the receiving means 106 on the transportable container 10 when the transportable container 10 is fully engaged on the engaging means 60. The communicating means 50 communicates across the communication line 51 with the data processing means 20 on the processing station 100. 
     A preferred embodiment of the circuit mounted on the data card 40 is shown in FIG. 7. The data card 40 shown schematically in FIG. 7 includes a data processing system 151 in communication across a bus 152 with a plurality 153 of input/output devices. 
     The data processing system includes a CPU 154, a non-volatile memory device such as a ROM 155, a random access memory device 156 for reading and writing data, and a power supply 157 such as the power supply shown in FIG. 5. 
     The plurality of input/output devices include any one of the following devices. First, a display 160, such as an LED or liquid crystal display, may be mounted on the data card 40 for providing data to an operator. Also a keyboard 161 may be mounted on the data card 40 with the transportable container 10 so that an operator may control data stored within the data card 40. 
     A sensor device 162 may be included on the data card 40 which communicates with a plurality of sensors on the transportable container 10. These sensors may provide information regarding conditions, such as engagement or disengagement of the transportable container 10 with an engaging means 60, opening or closing of the port in the transportable container 10 for allowing access to the articles stored within a container or other conditions. Further, a sensor may be included which indicates whether a retaining device has engaged the articles stored in the container. Many other sensors may be included depending on the particular processing steps being carried out and the characteristics of articles being transported in the transportable container 10. 
     The plurality of input/output devices 153 includes a transmitter 163 and a receiver 164 such as the light emitting diode 44 and photosensitive transistor 52 discussed with reference to FIGS. 4 and 6. The transmitter 163 and receiver 164 may be of other varieties of phototransistors and photodetectors as suited to the particular use required. Further, the transmitter and receiver may be comprised of a magnetic tape and a magnetic reading head. Other acoustic, inductive or optical means of accomplishing data communication between the electronic data card 40 and the communication means 50 may be implemented as suits the particular needs of the device. 
     Further, the data card 40 may include a real time clock 165 for generating data regarding real time. Data from the clock 165 may be useful by the processing stations in determining parameters for processing and the like. Also, the clock 165 may be used for determining length of storage time for the articles contained in the transportable container 10. 
     DISTRIBUTED PROCESSING SYSTEM 
     In accordance with the present invention, the transportable container 10 with the data card 40 attached to it can be used in conjunction with a plurality of work stations, such as the work station 100 illustrated in FIG. 1, to form a novel distributed processing system. Once such distributed processing system is used to fabricate semiconductor integrated circuits. The fabrication of semiconductor integrated circuits typically involves the processing of semiconductor wafers using a variety of discrete processing operations using a corresponding variety of work stations. 
     For example, the processing operations and corresponding work stations involved in the fabrication of a semiconductor integrated circuit from a semiconductor wafer might include the following operations and work stations A resist is applied to the wafer at a first work station. The thickness of the resist is measured at a second work station. A circuit pattern is exposed onto the resist at a third work station. The circuit pattern is developed at a fourth work station. The width of one or more circuit traces are measured at a fifth work station. Etching of the exposed resist is performed at a sixth work station. Those skilled in the art will appreciate that the exemplary processing steps and work stations just described are but a representative few of a large variety of possible processing steps and work stations. 
     In a given semiconductor integrated circuit processing environment, there may be a variety of batches of wafers simultaneously undergoing fabrication. Each batch may be enclosed within a different transportable container 10 or group of containers each with its own associated card 40. Furthermore, different batches of wafers may undergo different operations at different work stations so as to ultimately produce different types of semiconductor integrated circuits. Alternatively, different batches of semiconductor wafers may use the same work stations, but may be processed somewhat differently by the work stations as to ultimately produce different types of semiconductor integrated circuits. For example, the resists of two batches of wafers both might be etched at the sixth work station, but one batch might be etched for a longer period of time than the other. 
     Additionally, the nature of the processing operations to be performed in the course of fabricating integrated circuits from a batch of wafers may depend upon the outcome of earlier processing steps. For example, the step of etching the exposed resist at the sixth work station may have an etch time which depends upon the width of the one or more circuit traces measured at the fifth work station. Therefore, the outcome of the circuit trace measurement is used to determine the etch time. 
     Consequently, there exists a need for a processing system such as that of the present invention for the control of complex processing operations like the manufacture of semiconductor integrated circuits. 
     Referring to the drawing of FIG. 1, it will be appreciated that the work station 100 is merely representative of a variety of work stations which can form part of a processing system in accordance with the present invention. Thus, although the processing system will be described with reference to the work station 100 shown in FIG. 1, it will be appreciated that the actual processing system includes a plurality of work stations for performing a variety of processing operations such as those discussed above: applying a resist, measuring resist thickness, exposing the resist, measuring the width of circuit traces, and etching the resist. 
     Referring once again to the illustrative drawings of FIG. 2, it can be seen that coupled to the local control, processor 20 (hereinafter &#34;local&#34; 20) is a local transfer control processor 300 and a local operation control processor 302. In operation, the local 20 is mounted on the work station 100 in electronic communication with the means 50 which serves as a two-way communication means with the data card 40. Referring to FIG. 4, the microcomputer 101 of the data card 40 can engage in two-way communication, through transmitter 104 and receiver 106, with means 50. Referring once again to FIG. 9, the local 20 is in electronic communication with local transfer control processor 300 and the local operation control processor 302. 
     The local transfer control processor 300 controls the operation of transfer means 304 which include arms 306 for transferring a cartridge 31 containing wafers 32 between the work station 100 and the transportable container 40. One embodiment of the preferred transfer means 304 is described in U.S. Pat. No. 4,676,709, entitled &#34;LONG ARM MANIPULATOR FOR SEALED STANDARD INTERFACE APPARATUS&#34;. An alternative embodiment of the transfer means 304 is described in U.S. Pat. No. 4,674,936, entitled &#34;SHORT ARM MANIPULATOR FOR SEALED STANDARD MECHANICAL INTERFACE APPARATUS&#34;. These two Patents are incorporated herein by this reference. 
     The local operation control processor 302 controls the operation of the work station 100. As explained above, work station 100 is shown for purposes of example only. Any number of a variety of different types of work stations performing a corresponding variety of processing operations can be included in the processing system. 
     The system will be explained With reference to an exemplary manufacturing operation and with particular reference to the fabrication of semiconductor integrated circuits, but it should be appreciated that the system is applicable to other operations as well. The flow charts of FIGS. 9 and 10 illustrate the novel distributed control aspects of the system. Distributed control is an important feature of the system of the present invention which must be flexible enough to efficiently select among a variety of processing steps and work stations. 
     As explained above with reference to FIG. 1, a transportable container 10 with its attached data card 40 is transported to a work station, for example, by a human operator. Referring now to FIGS. 1 and 9, after the container 10 is engaged to the work station 100, indicated as step 402 in the flow chart of FIG. 9, the local 20 queries the data card 40 as to whether it is ready to exchange digital information, step 404. The data card 40 responds with a digital message generated by its microcomputers 101 (see FIG. 4) that it is set to exchange digital information, step 406. 
     The local 20 instructs the data card 40 to report its status, step 408. In response, the microcomputer 101 of the data card 40 performs a self-test, step 410. The self-test, for example, may include a test to determine whether the card&#39;s battery 125 and RAM 102 are in proper working order,. If the self-test determines that the card is not in proper working order, then the microcomputer 101 causes a signal to appear on the card display 21 indicating that the card 40 may not be operating properly, step 411, and digital communication between card 40 and the local 20 typically stops. If, however, the self-test shows the card 40 to be operating properly, then the card 40 reports that the procedure may continue, step 412. 
     The local 20 then requests that the card 40 identify itself and provide the current processing data, step 414. In response, the card 40 provides an identifying code. In a semiconductor integrated circuit manufacturing processing system, the card might also identify the lot number of the semiconductor wafers to be processed as well as the identity of the work station which is to perform the next processing step and a specification of what processing step is to be performed next, step 416. For example, the next processing step might be the exposing of a circuit pattern onto a resist at the third work station. The local 20 determines whether the container 10 with its contents and its card 40 is at the correct work station to perform the next processing step, step 418. If it is not, then it informs the data card 40 which reports via display 21 that the container 10 is at the wrong work station, step 420, and typically digital communication between the card 40 and the local 20 stops. If the local 20 determines that the card 40 is at the correct work station, then digital communication continues between the card 40 and the local 20. 
     The local 20 responds by instructing the local transfer control processor 300 to cause the transfer of articles to be processed from the transportable container 10 to the work station 100, step 422. For example, in semiconductor integrated circuit fabrication, a cartridge 31 containing wafers 32 to be processed is lowered from the container 10 to the work station 100 via arms 306. 
     Next, the local 20, instructs the local operation control processor 302 to initiate the processing operation, step 424. For example, the processing operation to be performed by the work station might be to expose a circuit pattern onto a resist applied to a semiconductor wafer. 
     The local 20 informs the card that the transfer has been completed and that the processing operation has been commenced, step 426. The local 20 composes a first history record identifying the work station and indicating that the transfer has occurred and that the processing operation was commenced, step 428. The local 20 communicates the first history record to the card 40, step 430. The card 40 stores first history record, step 432. The local 20 instructs the card 40 to date and time stamp the first history record; using its microcomputer 101 and real-time clock 165 (FIG. 7); the card 40 complies with the instruction and records a date and time record for the first history record, step 434. 
     Upon completion of the processing operation, the local operation control processor 302 informs the local 20 of its completion, step 436. The local 20 instructs the local transfer control processor 300 to imitate a transfer of the articles processed, the semiconductor wafers 32 for example, from the work station 100 back to the transportable container 10, step 438. 
     The local composes a second history record, step 440. The second history record, for example, provides a record of the operation of exposing a circuit pattern onto a resist applied to a semiconductor wafer. The local 20 communicates the second history record to the card 40, step 442, and instructs the card 40 to date, time stamp and store the second history record, step 444. 
     The local 20 instructs the card 40 to advance to the next processing step, step 446. In response, the card 40, prepares for the next processing step, step 448, for example by changing the identity of the work station and process to be identified in step 416 at the next work station. Finally, the card 40 causes its display 21 to identify for the operator the next work station to be visited by the transportable container, step 450. 
     Two examples which follow illustrate the significance of including a microcomputer 101 on the card 40. 
     The first example will be explained with reference to FIG. 10 in which there is shown an alternative flow chart path which can be substituted for steps 408-420 of the flow chart of FIG. 9. In the alternative flow chart, following step 406, explained above, the card 40 itself initiates and performs the self test, step 500, described above with respect to step 410. If the card 40 determines that it is not operating properly then it causes its display 21 to report its inoperability, step 502, and communication with the local 20 typically stops. On the other hand, if the card 40 determines that it is operating properly, then the card 40 requests that the local 20 report its identity, step 504. In response, the local 20 identifies itself to the card 40, step 506. The card 40 then determines whether it is the correct work station. If it is not, it causes the display 21 to display an appropriate message, step 508, and communication with the local 20 typically stops. If the card 40 determines that it is in fact at the correct work station, then the card 40 instructs the local 20 to initiate the first material transfer, step 510. 
     The second example will be explained with reference to the flow chart of FIG. 11 in which a representative series of card operations and work station operations from an exemplary semiconductor integrated circuit fabrication process are shown. For the purposes of this example, the card 40 is assumed to have stored in its RAM 102 a formula for calculating etch time; step 600 represents the storage of the formula. The formula, for example, might be: K+A (width specified--width measured) +B (resist thickness). Where K, A and B are constant values, and the &#34;width specified&#34; refers to the specified width of a circuit trace, and &#34;width measured&#34; refers to the measure width of the circuit trace, and &#34;resist thickness&#34; is the measured thickness of a resist applied to a semiconductor wafer. 
     The first processing step is to apply a resist to semiconductor wafers being processed, step 602. This step, for example, is performed at a first work station. The thickness of the resist is measured at a second work station, step 604, and the measured thickness is stored in the card&#39;s RAM 102, step 606. A circuit pattern is exposed onto the resist at a third work station, step 608. The circuit pattern is developed at a fourth work station, step 610. The width of one or more circuit traces are measured at a fifth work station, step 612, and the measured width is stored in the card&#39;s RAM 102, step 614. The card 40, using its microcomputer 101, calculates the etch time, step 616, using the formula stored in step 600 and the measurements stored in steps 606 and 614. The exposed resist is etched for the calculated etch time, step 618. 
     From the preceding two examples, it will be appreciated that the card 40 advantageously can be used as part of a distributed processing system which does not require centralized control. Instead, a card 40 associated with a transportable container 10 containing articles to be processed can store processing data pertaining to the particular articles, and can perform calculations necessary to properly process the articles. 
     INVENTORY MANAGEMENT SYSTEM 
     The present invention also provides a novel inventory management system which advantageously can monitor the status of articles, such as semiconductor wafers for example, between processing operations. 
     Referring to the illustrative drawings of FIG. 12, there is shown a tray 630 including a recessed region 632 sized to receive a transportable container 10 having a data card 40 mounted on it as shown. The tray 630 includes a two-way communication means 50-1 like the two-way communication means 50 described above and mounted on the work station 100. 
     As illustrated by the dashed lines 634, the base portion 636 of the transportable container 10 can fit snugly within the recessed region 632. When the transportable container is received within the recessed region 632, the card 40 is aligned with the two-way communication means 50-1 such that the card 40 and the means 50-1 can engage in two-way communication with each other. 
     Referring now to the illustrative drawings of FIG. 13, there is shown in block diagram form an inventory management system 637 which includes a plurality of trays divided into respective qroups of trays 630-1 through 630-N. Each respective individual tray is like that described with reference to FIG. 12. Each tray in the respective groups of trays 630-1 through 630-N is coupled by a respective control line 639-1 through 639-N to a multiplexer circuit 640-1 through 640-N. The respective multiplexers 640-1 through 640-N are coupled via control line 642, which for example can be an RS232 C line, to a storage control processor 644. 
     In the presently preferred embodiment, the storage control processor 644 comprises an IBM compatible personal computer. The multiplexers 630-1 through 630-N are coupled to one another in a daisy chain such that signals propagated along control line 642 proceed in a serial fashion from one multiplexer circuit to another. Although only two groups of trays 630-1 and 630-N are shown together, with two associated multiplexer circuits 640-l through 640-N, it will be appreciated that a plurality of groups of trays and a corresponding plurality of groups of multiplexers can be included in the inventory management system 637. 
     In operation, a plurality of transportable containers 10 can be placed into the respective trays 630-1 through 630-N of the inventory management system 637. An operator can use the storage control processor to ascertain, for example, the processing status of the contents of any container 10 received within any of the trays of the system 637. 
     More particularly, for example, in order to obtain information regarding the contents of the container 10 shown in FIG. 12, the storage control processor 644 instructs the respective multiplexer circuit (not shown) coupled to that tray 630 to select that tray 630 and to couple it to the processor 644. The storage control processor 644 sends digital signals to the selected tray 630 which cause two-way communication between the tray-mounted two-Way communication means 50-1 and the card 40. Through the two-way communication, the storage control processor 644, for example, can ascertain the contents of the container 10, the processing steps already performed on those contents and what processing steps are scheduled to be performed in the future. Additionally, through such two-way communication, the storage control processor 644 can be used to reprogram the microcomputer 101 of the card 40, for example, so as to modify processing instructions stored in the card&#39;s RAM 102 or to update or correct its real time clock. 
     Thus, it will be appreciated that the present inventory management system 637 advantageously can distribute, for example, the task of maintaining a history of the processing steps and a schedule of future processing steps for the articles within respective transportable containers 10. Consequently, the storage control processor 644 is free from maintaining and managing such information. 
     One example of a material tracking system, known as a SMART-Traveler System (STS), in accordance with the present invention will be provided with reference to FIG. 14. The system shown in FIG. 14 includes a plurality of work centers 700 n  (only one work center is illustrated) and a control center 701. The system is known as a SMART system because of the system&#39;s ability to track each article being processed and to centrally control the processing of each article. 
     The data card 40 (also known as a SMART-Tag) is the foundation of the STS. A data card 40 is attached to each material container and carries all the information pertaining to the material inside the container 10 to which the data card is attached. Each data card 40 has 8 kilobytes of RAM 156; a two-way infrared communications system; a battery with a life sufficient for more than one year of continuous operation; a 16 character liquid crystal display 160; an on-board microprocessor 154; and ROM 155 for storing software. The software stored in ROM 155 includes programming for providing the data card 40 with the capability of communicating with external devices using the infrared communications system. Error-free communication is accomplished using handshakes and a double checksum error detection method. When a transmission error is detected, the communication is repeated. 
     At each process station 702, a local data processor (known as a SMART-Arm Master (SAM)) 704 is responsible for checking the data card 40 attached to each material carrier 10 to assure that the correct material is processed through the correct process steps. When material arrives at a process station 702, the SAM 704 verifies that the material has come to the proper station 702. If material is not at the proper station, it is not loaded into the processing equipment 706. Once the material is loaded into the processing equipment 706, the date and time of occurrence is reported to a control center 701. A similar message is recorded when the processing is complete. Then the next sequence step information is displayed on the data card 40. 
     SAM 704 communicates with an automatic loading unit (ALU) 707, such as the transfer means 304 discussed above, provided at each workstation 702 via communications link 708. A configurable communication link 710 may also be established between a SAM 704 and the processing equipment 706 to allow recipe information can be transferred directly to the processing equipment 706. Similarly, process parameter data generated by processing equipment 706 may be collected by the SAM 704 and transferred to control center 701. The communication between each SAM 704 and ALU 707 and processing equipment 704 is SECS 1 and SECS II protocol by RS-232-C communications at 9600 BAUD. 
     SMART-Storage Areas (SSAs) 740 are located at each work center 700. When not undergoing processing, wafers are stored in the SSA 740 in containers 10 with data cards 40 attached. When containers 10 are brought to a SSA 740, they are placed in storage trays 630. Each storage tray 630 is connected to a storage control processor 644 via an RS-232 based communications link 746 so that the data card 40 may communicate with the storage control processor 644. The storage control processor 644 is, for example, an IBM compatible personal computer, which monitors all material in storage, keeps a back-up copy of the data card 40 data, provides a user interface for updating data card 40 whenever a change affects a lot (for example, lot arrival, lot data change on a waiting lot), and updates the SSA 740 database maintained by storage control processor 644 and the control center 701 database. The program executed by storage control processor 644 offers a menu-driven user interface. Most of the commands can be accessed through the use of a light pen 750 without the necessity of the keYboard. All of the features are also accessible through a keyboard. 
     Control center 701 provides overall facility and workcenter control and includes a central data processor (CDP) 720 which has a CPU 721, a data storage device 722, and a terminal 723 for operator interface. In the currently preferred embodiment of the invention, CPU 721 is a VAX computer manufactured by Digital Equipment Corporation. The VAX computer may be configured as the PROMIS Version 4.3 central facility host system available from Promis Systems Corporation or the COMETS centralized facility host system available from Consilium. 
     A network provides connections between CDP 720 and all other components of the STS System. The network contains three levels of communication, i.e., an Ethernet based LAN 760, an RS-485 base LANs 762, and RS-232 based communications links. 
     The Ethernet LAN may be, for example, DECNET, a proprietary network of Digital Equipment Corporation (DEC) and is based on Ethernet (IEEE 802.3) hardware and low-level protocol. Data is transmitted at 10M BAUD (nominal) over co-axial cables with a special tap and electronic card at each network node. Each storage control processor 644 communicates With CDP 720 using LAN 760. Messages sent on LAN 760 are formatted according to the SEMI Equipment Communication Standard Protocol (SECS II) for data relating to the COMETS or PROMIS systems, or according to the DEC Local Area Terminal Protocol (LAT) when a SAM 704 is used as a terminal for CDP 720. 
     A multi-drop RS-485 &#34;bus&#34; 762 connects the SAM 704 at each process station 702 to a local link manager 770. The RS-485 chain operates at 1M BAUD in synchronous communications mode using SDLC low-level protocol. Each SAM 704 generates SECS II formatted messages which are sent to the link manager 770 which transfers them to CDP 720 via LAN 760. 
     In certain work centers some of the SAMs 704 may not be set up for communicating with CDP 720. In this case the program executed by the SAM 704 will query the data card 40 on a container brought to the workstation 702 to determine the number of process steps which have been performed since the status of the wafers in the container was last reported to CDP 720. If the number of process steps exceeds a certain number of steps, for example, four steps, the SAM 704 will not allow the wafers to be processed until the status information is reported to CDP 720. Both the SAM 704 and the data card 40 will display a message indicating that the container 10 must be placed in an SAM 704 or a storage center 740 for updating. 
     Wafer processing in the STS of FIG. 14. is as follows. In order to begin a log of wafers in the facility, the operator places an empty container 10 on an ALU 707 designated for the initialization task. The operator then controls the ALU 707 to open the container 10. Wafers are inserted into a cassette and the cassette is placed on the opened container 10 door in the ALU 707. A NEWLOT function is initiated on SAM 704 and the lot ID and wafer ID numbers are entered. CDP 720 checks for lot ID duplication and verifies that the lot ID is unique. Then, the SAM 704 receives lot status from CDP 720 and Writes the lot ID, next equipment type and work center into the data card 40. The operator controls ALU 707 to close container 10 with the cassette of wafers inside. The container is released by the ALU 707 and ready to be carried to either the first process equipment or any SSA 740. 
     When not undergoing processing, wafers are stored in SSAs 740 located at each work center 700. Wafers are kept in containers 10 with data card 40s attached. The data card 40 on each container 10 indicates the lot name, and the work center identification, and the equipment type to be used for the next process step. 
     Transportation operators move among the work center SSAs 740 with carts for moving containers 10 of wafers through the facility. When a transportation operator approaches a SSA 740, the operator uses a light pen to request the lots which belong at a different SSA 740 (based on the list of work centers supported by the storage area stored on the storage control processor 644). The LED on the storage trays 630 containing those lots will blink for a specified time (i.e., ten seconds). The transportation operator will remove these containers 10 and place them on the cart for movement to the a different SSA 740. The transportation operator may consult the liquid crystal display (LCD) on each data card 40 for the destination work center. 
     When material arrives at an SSA 740, the storage control processor 644 will send a message to CDP 720 requesting the next process step information. The response from CDP 720 identifies the correct equipment type and work center to the storage control processor 704. The data card 40 is now updated as needed. If the next work center for that lot is not on the list for that storage area 740, the lot LED will blink (for ten seconds) to indicate removal by the transportation operator. 
     The storage control processor 644 will send an ACCEPT INTO CELL time stamp message. This message contains the current bin number of the lot, which CDP 720 stores for later use. The lot now waits for an equipment operator to remove it for processing. 
     When an equipment operator is ready to process wafers, the operator will go to a CDP 720 terminal, e.g., an SAM 704, to examine the queue of material. The operator select a lot from the queue and CDP 720 displays the location of this lot (based on last time-stamp location). Then, the operator will locate this container by bin number and remove it. The operator must check the LCD on the data card 40 to make sure that the correct container has been obtained. The data card 40 LCD will show the Lot ID, work center, and equipment type for the next process step. When the container is removed, the storage control processor 644 will notify CDP 720 of its removal by an Accept Into Cell time stamp. ###If CDP 720 data indicates that control action is required before the next processing step, the data card 40 LCD will show an equipment type and the control wafer action (ADD or Putback) to be performed. The operator carries the container 10 to the designated ALU 707 and places the container 10 onto the ALU 707. The SAM 704 associated with the ALU 707 recognizes that control wafer action is required and allows the operator to open the container 10. 
     The operator moves the correct control wafers into the cassette and enters the wafer ID numbers into the SAM 704. These wafer numbers are sent in a Control Material Action message to notify CDP 720 of the completion of the control material Add/Putback. Next, the data card 40 tells the operator to take the lot to a work station 702 for processing. 
     If one of the work stations 702 is a sorter, the SAM 704 at the sorter will read the control wafer requirements from the data card 40 and command the automatic sorter. The cassette slots for control wafers will be selected by the sorter and recorded in the data card 40. Upon completion, the SAM 704 sends a Control Material Action message to notify CDP 720 of the completion of the control material Add/Putback. Next the data card 40 will tell the operator to take the container 10 to the process tool for processing. 
     The operator now carries the container 10 to the process equipment. At the equipment, the lot is placed on the ALU 707. The lot ID and the intended process destination are read from the data card 40 by the SAM 704. If the container is at the wrong process equipment (meaning that the data card 40 data and SAM 704 configuration do not match) the SAM 704 requests lot status information from CDP 720, then updates the data card 40 (if necessary) and blinks the LED (if the container is still at wrong the equipment). 
     If the container 10 is at the correct process equipment (meaning that the data card 40 data and SAM 704 configuration match) the SAM 704 asks the operator for their operator ID and attempts to track-in the lot to this processing equipment 706. To be accepted, CDP 720 will verify the lot is in waiting state, verify that the correct equipment/work station 706 as the current destination, and verify that the operator ID is valid. 
     If CDP 720 sends a rejection, SAM 704 sends a message to CDP 720 requesting lot status. In this event, a red light will blink on the ALU 707, the data card 40 LCD will show the correct destination for this container, and the cassette transfer operation will not be allowed. The data card 40 is updated if necessary. 
     As a lot-track-in has been accepted, the lights at the operator control panel of the ALU 707 so indicate. If the lot is now removed, the SAM 704 sends an Inquire Cancel Track-in to abort the operation. The lot is loaded into the equipment by ALU 707. The data card 40 is marked to show the lot in Run state. Any process specifications that were stored in the data card 40 or sent by CDP 720 are displayed on the local SAM 704 terminal screen. 
     SAM 704 sends a Start Run time stamp to CDP 720. If the station is equipped with the configurable equipment interface 710, the SAM 704 may be configured to wait for the process equipment Start message before sending the Start Run time stamp to CDP 720. 
     If the station is equipped with a configurable equipment interface 710 and the lot data calls for an automatic recipe, then the SAM 704 inserts lot parameters from the lot data into a pre-stored recipe skeleton and sends this recipe to the equipment 706. 
     Data collection operations (DCOP) can occur in one of two ways. If the station 702 is equipped with the configurable equipment interface 710, data can be acquired directly from the equipment 706 by the SAM 704. This data is sent to CDP 720. Where this method is not used, collection is done by operator entry directly into CDP 720. The SAM 704 is used as a virtual terminal for this purpose. 
     When the process step has been completed, the operator causes ALU 707 to unload the wafers from equipment 706 and to put the wafers back into container 10. First, the operator is again asked to enter their identification number on the SAM 704. The SAM 704 sends an End Run time stamp to CDP 720. If the station is equipped with the configurable equipment interface 710, the SAM 704 may be configured to send the End Run time stamp to CDP 720 when the equipment Stop message is received. The track-out is performed on the CDP 720 system automatically by the SAM 704. The lot is now updated and released to the operator. The LCD display tells the operator which work center and equipment the lot should go to next. 
     The operator carries the lot to the next station 702 or to an SSA 740. If the lot arrives at an SSA 740, the Send from Cell time stamp is sent, and then location for the lot is confirmed. 
     In this manner, the processing of every wafer is tracked by the CDP 720. This detailed wafer tracking is particularly important if the different wafers in a single container 10 are to undergo different processing steps. Another important aspect of the interaction with CDP 720 is that the operators are not required to determine process parameters for various batches; the process parameters are downloaded from CDP 720 to the SAM 704 and either displayed by SAM 704 or downloaded from SAM 704 to equipment 706 via interface 710. 
     For manual process steps, an ALU 707 may be used to move the lot out of the container 10 for processing. The lots to be processed are placed, one at a time, onto the ALU 707. The lots are validated and tracked by entering the lot data into CDP 720. Then, the container 10 may be opened and the wafers removed for processing. When the process is complete, the lot is returned to the ALU 707. Any empty container 10 (containing an empty cassette) is placed on the ALU 707 and the container 10 is opened. The lot is placed into the container 10 and the operator enters the lot ID. The SAM 704 does Track-out and writes lot information into data card 40. ALU 707 closes container 10. 
     If rework, split, join, or scrap is required, the operator must go to a CDP 720 terminal and initiate one or more of these sequences. The lot must then be placed into storage or on an ALU 707 to update the data card 40. 
     In some cases, the material information obtained by a SAM 704 upon Track-in may include a flag to indicate control action will be required before Track-out. In this event, the SAM 704 at the process tool will send the message Request Control Material Removal Information. The material removal instructions obtained will be stored in the data card 40 in the form of a pseudo-process step. When material removal instructions follow a process step, the operator is told (by the data card 40) to go to the ALU 707 for the test wafers to be removed. At the ALU 707, the wafers are removed manually, CDP 720 is notified with the Control Material Action message, and then the Track-out occurs. 
     The foregoing description of a preferred embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teachings. The particular embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.