GB2210996A

GB2210996A - Contents verification apparatus

Info

Publication number: GB2210996A
Application number: GB8723790A
Authority: GB
Inventors: Christopher John Waters; Jonathan Burnie
Original assignee: Plessey Co Ltd
Current assignee: Plessey Co Ltd
Priority date: 1987-10-09
Filing date: 1987-10-09
Publication date: 1989-06-21
Also published as: WO1989003586A1; JPH02501694A; GB8723790D0

Abstract

A contents verification apparatus is disclosed particularly for use in the manufacture of integrated circuits wherein wafers of silicon are transported in sealed containers between closed pollution-free environments whereat particular process operations may be effected on the wafers. The verification apparatus permits the containers to be opened, the wafers to be extracted and identified and if desired sorted, split or merged for onward transmission to further environments for subsequent process operations to be effected.

Description

CONTENTS VERIFICATION APPARATUS This invention relates to a contents verification apparatus. In, for example, the fabrication of integrated circuits on silicon wafers, there exists a method in which each of the process stages comprises an individual closed pollution-free environment, and the silicon wafers are transported between these environments in closed containers. Such a method and an associated apparatus is described in an article entitled "SMIF: A technology for wafer cassette transfer in VLSI Manufacturing" by Mikir Parikh and Ulrich Kaempf published in Solid State Technology" July 1984. It is detrimental if the silicon wafers are handled at the process stations any more than is necessary and therefore the container and its contents are initially recorded and stored in a data base.The container has identification means and can be tracked between and at process stations. Its progress can be monitored and, if its contents are purposefully changed, the information can be reported to a host computer and stored in the data base. The data base ideally includes a history of each wafer, the processes it has undergone, and the container in which it is temporarily residing. This history is updated each time a container arrives at a process station.

In our copending patent application No. 87 to\E 6#% filed simultaneously herwith, we described a security tag for such a container - the security tag is arranged to provide an indication if a container has been accidentally or otherwise opened. In such an instance, it is necessary that the contents thereof be re-verified and the histories of the wafers correspondingly updated.

There may be other occasions when it is desired to verify the contents of such a container.

It is an object of the present invention to provide a contents verification apparatus particularly, but not exclusively, for use in the fabrication of integrated circuits as above described.

According to the present invention, there is provided a contents verification apparatus comprising manipulating means for extracting one article from a supply of similar articles, reading means for reading an identification provided on the article, at least one receptacle for the article wherein it may be placed by the manipulating means after it has been read, and information storage means for storing information relating to the article provided by the reading means.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side elevation of a contents verification apparatus in accordance with the present invention; Figure 2 is a schematic plan view of the apparatus shown in Figure 1; Figure 3 is a block diagram of a contents verification apparatus, its associated host computer, and other cooperating apparatus; and Figure 4 is a flow chart indicating the operation of a contents verification apparatus according to the present invention.

Referring firstly to Figures 1 and 2, a contents verification apparatus constructed in accordance with the present invention comprises a closed pollution-free environment 10 whereto a sealed container is transportable. The environment 10 includes means for loading the container thereinto, for opening the container and for removing a cassette 12 holding a plurality of silicon wafers 14. Upon removal, the cassette 12 is located at a station 16. A cassette 12 located at the station 16 presents its wafers 14 at predetermined locations relative to a wafer manipulator 18 vertically movable and pivotable so that a vacuum arm 20 thereof may engage a wafer 14 in the cassette 12 and remove the same. The arm 20 may include means for rotating a wafer 14 held thereby to index the same. The apparatus includes a track 22 whereon the manipulator 18 is mounted.The manipulator 18 positions the wafer 14 for reading of laser written identification marks thereon by a video camera 24.

The laser written identification marks may be machine readable by apparatus other than a video camera but are additionally preferably readable by an operator at a monitor outside the environment 10.

As will be described hereinafter, the contents verification apparatus is in communication with a host computer and the identity of the wafer 14 is fed thereto. The computer decides whether the wafer 14 is to be reloaded into the cassette or transferred to one of a plurality of other ports or stations 26 for subsequent submission to a process stage associated with the verification apparatus or for reloading into cassettes (not shown) for transport in sealed containers to other process stations. Elevators 28 at the stations 26 serve to position cassettes vertically to receive such onwardly destined wafers 14.

The contents verification apparatus may be a self-contained unit or it may form part of a process station constituting a stage in the manufacture of the integrated circuits.

As a self-contained unit, its most advantageous use would be in verification of the contents of a sealed container which had been inadvertently, accidentally or illegally opened as detected by the security tag described in our aforesaid copending patent application.

Even for such use, it may form part of, but preferably isolated from, a process station.

Referring now to Figures 2 and 3, the contents verification apparatus is shown at 30. It comprises the wafer orientation station 16, the wafer manipulator 18, the wafer arm 20, the stations 26 and their respective elevators 28. It also includes a system control unit 32 for controlling the movement of the manipulator 18, arm 20, elevators 28 and the means for opening the sealed container (not shown) and for removing the cassette therefrom.

As mentioned above, the apparatus 30 operates under the control of a remote host computer via a host comms line 36 and a local program control processor 34. The video camera 24 or other reader provides an input to the processor 34 and to an imaging system 38 permitting an operator to examine and read the identification marks on the wafer disk 14 positioned in the camera's field of view. A local data store 40 provides operating programs for the processor 34 and provides also correlating data as required.

Manual controls 42 are provided enabling operator intervention with non-programmed actions. A reader 44, for example, a reader as described in our aforesaid copending patent application is connected by a comms interface 46 to the processor 34.

As mentioned previously and in our aforesaid patent application, each process station includes a reader 44 connected by its comms interface to the host computer and to an adjacent processor 34. In operation, and as shown in the flow chart in Figure 3, a sealed container is docked at the process station to be interrogated by the reader 44 as to its unique identity and also to check the security tag for non-authorised opening of the container since last sealing. The reader comunicates the answers to the host computer and to the local processor 34. If the container has been opened, it is necessary to send the container to a self-contained contents verification apparatus if one is not provided at the particular process station.If one is there provided, the container can be opened and each of the wafers 14 contained therein extracted from the cassette 12 read by the video cameraloperator or machine read, replaced in the cassette 12, and have information relating thereto transmitted to the host computer to up-date the history of the particular wafer held in the data store of the host computer.

When all the wafers have been examined, the cassette is resealed in its container and the security tag of the container reset. The container is then despatched to its correct destination if other than the process station containing the contents verification apparatus.

The foregoing sequence is a very desirable use of the contents verification apparatus of the present invention.

It can also be used as a "shunting yard" i.e. it will perform batch split, merge and sort facilities.

Assuming a sealed container arrives at a contents verification apparatus. If the security tag indicates that it has been opened, it is dealt with as above. Thereafter, or if the security tag reports that the container has not been opened, a "split" command is received from the host computer or from the local processor 34. The container is then opened to permit the cassette 12 therein to be located at the station 16. Each wafer 14 is then extracted from the cassette 12, manipulated for reading, read, and placed as directed in elevator 28 or into a cassette located at that port. In this way, individual wafers can be sorted into new stacks, operated on at the particular process station, or returned to the original cassette.

Further, wafers 14 already located in a particular elevator 28 or in a cassette at a station 26 can be transferred into the cassette 12 located at the station 16. In this way, cassettes for onward transmission in sealed containers to particular process stations can be shunted around. Such an arrangement is necessary in the manufacture of low volume custom integrated circuits in which many different wafers may be assembled at a process station to undergo a common process and thereafter be split to go to separate process stations. The use of a contents verification apparatus in accordance with the present invention, by updating a history of a particular wafer allows track to be kept thereof although that wafer may be mixed with other disparate wafers, at various times, in different cassettes, in different sealed containers andlor at different process stations.

The invention is not confined to the precise details of the foregoing example and many variations may be made thereto.

For example, although described in relation to the fabrication of integrated circuits, a verification apparatus as described may be used in a similarly operating apparatus. The ports 26 of the contents verification apparatus may each constitute a transfer port directly to a separate process sub-station or to a separate process station.

The host computer may deliver global commands such as "verify contents", "sort contents", "split contents" and "merge contents" to the apparatus together with appropriate identification of the wafers. Alternatively, as each wafer is read, the host computer may, in real time, indicate to the verification apparatus the necessary function to perform with that particular wafer.

The contents verification apparatus is most useful when operating in a closed pollution-free environment thereby reducing the danger of contamination of the wafers handled thereby. Where such danger does not exist, it could be used without an environmental enclosure.

Other variations are possible within the scope of the present invention.

Claims

1. A contents verification apparatus comprising manipulating means for extracting an article from a supply of similar articles, reading means for reading an identification provided on the article, at least one receptacle for the article wherein it may be placed by the manipulating means after it has been read, and information storage means for storing information relating to the article provided by the reading means.

2. An apparatus as claimed in claim 1 including an environmental enclosure for maintaining a closed pollution-free environment thereabout.

3. An apparatus as claimed in claim 1 or 2 wherein the articles are supplied thereto in a sealed container, and further including means for opening the container and for locating the contents thereof at a manipulating station.

4. An apparatus as claimed in claim 1, 2 or 3 wherein the manipulating means comprises a vacuum arm for extracting an article from the supply.

5. An apparatus as claimed in any preceding claim wherein the manipulating means comprises means for orienting the article prior to presentation thereof to the reading means.

6. An apparatus as claimed in any preceding claim wherein the reading means includes means for machine reading identification marks on the article.

7. An apparatus as claimed in any preceding claim wherein the reading means comprises a video camera and a monitor to permit an operator to read identification marks on an article.

8. An apparatus as claimed in any preceding claim further including a plurality of receptacles and central means for directing the manipulating means as to the receptacle in to which an article is to be placed after reading.

9. An apparatus as claimed in any preceding claim wherein the articles are supplied to the apparatus in stacking means inside the container, and wherein the or each receptacle is arranged to receive a stacking means, for receipt of an article, after reading, thereinto.

10. An apparatus as claimed in any preceding claim wherein the articles are silicon wafers and the apparatus is associated with a process station of an integrated circuit manufacturing process.

11. An apparatus as claimed in claim 10 wherein the apparatus or the process station associated therewith includes a reader for reading an identification of a container of articles supplied thereto and for detecting the state of a security tag attached to the container to determine whether the container has been illegally opened.

12. An apparatus as claimed in claims 9 and 10 or 9 and 11 wherein the silicon wafers are stacked in a cassette in a sealed container, and the or each receptacle contains a cassette for the receipt of wafers after reading.

13. An apparatus as claimed in any preceding claim wherein the means for storing information relating to the articles comprises a comms interface for interfacing the apparatus to a host computer having a data store whereby a complete up-dated history of each article may be maintained.

14. A contents verification apparatus substantially as hereinbefore described with reference to and or illustrated in the accompanying drawings.