For example, such arrangements can be used in the process of manufacturing semiconductor products. In this case, the loads to be moved can be formed as containers for storing objects, particularly for storing disklike objects such as wafers, flat panels, CDs, or the like.

In the technical field of manufacturing and processing wafers (for example disks on the basis of silicon), flat panels or CDs in semiconductor industries it is common and necessary that wafers are frequently moved between different locations such as processing stations. Moreover, there is a need to store said wafers in specific storage areas, when they are not needed for the moment or before they are moved to a next processing station, respectively.

Usually, wafers are stored and processed under minienviron- ment conditions. In light of the present invention, the term minienvironment defines a localized environment created by an enclosure to isolate a product from contamination and/or peo- ple. The requirements for such minienvironments are set forth in SEMI-standards E44 for example.

During the transportation, and any processing and storage steps or conditions, said wafers are usually stored in spe- cial containers, for example in socalled Front-Opening- Unified-Pods (FOUP).

In order to move such containers from one location to another location, they are usually carried by special vehicles which

are moved along a system of tracks. Said system of tracks is generally mounted at the ceiling of said environment or fab- rication, thus forming a socalled Overhead-Transport-System (OHT).

Until now, these vehicles are moved by aid of an electric drive which receives its electric energy from one or more re- chargeable batteries. Even though the energy supply by such rechargeable batteries provides highly flexible OHT-systems with regard to its installation and the layout of the fabri- cation, it also bears several disadvantages, especially in view of a continous operation. The disadvantage of a battery driven OHT vehicle as known in the art is the reduced avail- ability and predictability, based on the needs for recharg- ing, recharging cycles, recharging logistic and the like.

According to another known solution, those vehicles carrying loads are moved by an electric drive which is cabled to an external electric power source. With such a system, the draw- backs regarding said needs for recharging procedures can be overcome. However, the disadvantage of such a system is that the requirements concernig its construction and installation are very high. Since the vehicle is fixedly wired with said electric power source, the known system is very unflexible, especially in those areas comprising off-branching tracks.

In view of the prior art it is an object of the present in- vention to provide an arrangement for moving loads through an environment which overcomes the aforementioned drawbacks and which enables a continous operation.

This object is solved by the arrangement according to inde- pendent claim 1. Further advantages, features, aspects and details of the invention are evident from the dependent claims, the description and the accompanying drawings.

According to the present invention, an arrangement for moving loads through an environment, particularly through a fabrica- tion, is provided, said arrangement comprising at least one track, at least one conveying means being movable along said track and at least one light source for supplying an ener- getic light radiation, said conveying means being comprised of an electric drive and means for converting energy col- lected from said light source into electric energy for said electric drive.

The arrangement according to the present invention enables the conveying means to operate continously for material hand- ling. The principle of the present invention is, that said conveying means which is provided with an electric drive con- tinously receives an energetic light radiation from said light source. Said energy is transformed into electric energy by said means for converting energy, which is also mounted on said conveying means. The electric energy created in such a way is used to run the electric drive und thus, the conveying means itself.

Since said energetic light radiation can be supplied conti- nously, the aforementioned drawbacks with respect to re- chargeable batteries as known in the art can be avoided. This will enable an uninterrupted operation of the conveying means, as its electric drive will always be properly charged with electric energy. Furthermore, the arrangement according to the present invention does not require any cables leading to an external electric power source. Thus, it is very flexi- ble.

The present invention is not limited to a specific use of said arrangement. The arrangement can be used in any environ- ment or fabrication, wherein a load has to be moved between different locations. Furthermore, the invention is not lim- ited to any specific load to be carried.

In one advantageous embodiment, the arrangement according to the present invention can be used in a fabrication for semi- conductor products. In the following, the invention will be explained with respect to such a fabrication, without re- stricting the scope of the present invention to said specific embodiment.

The arrangement according to the present invention comprises three basic features. The first feature is at least one track. The second feature is a conveying means being movable along said at least one track. The third feature is a light source for supplying an energetic light radiation. These ba- sic features are described in more detail hereinafter.

The light source can be any source, which is able to emit an energetic light radiation. Therefore, the present invention is not limited to specific embodiments for said lihgt source.

For example, the ligt source can be adapted to emit short- waved light radiation or to emit solar energy.

The means for converting energy can be any means being capa- ble for converting said energy collected from said light source into electric energy for said electric drive. Said means can basically function in a manner that the emitted and collected energetic light radiation from said light source eliminates electrons from their state of binding. These elec- trons are now freely movable and can be conducted as an elec- tric current through said electric drive.

For example, said means for converting energy collected from said light source into electric energy for said electric drive can be comprised of one or more cells, which are par- ticularly formed as photoelectric cells or solar cells. The number and arrangement of said cell or cells depends on the amount of electric energy, which is necessary to run the electric drive.

Furthermore, one or more additional rechargeable battery or batteries can be provided. Advantageously, said battery or batteries are connected to said means for converting energy and said electric drive. The purpose of such an additional battery or batteries is to provide an intermediate storage battery, wherein electric energy produced by said means for converting energy is stored. Thus, the conveying means can also, at least temporarily, be moved under conditions, in which a light source is not available. Such a situation can arise, when the light source is installed only in one or a few locations, and the conveying means has to be moved also to locations, at which a light source is not installed. Fur- thermore, the rechargeable battery or batteries can bridge any periods, in which the light source does not work.

The solar powered vehicle has redundant batteries. One will be actively recharged by the solar cell from the light provi- ded by the lighting asove the track. While this is occurring, the vehicle is powered by a separate battery that is not being trickle charged during this time. Battery sensors in a control unit are in the vehicle to monitor the discharge sta- tus of the active battery and the battery being trickle char- ged. There is an electronic circuit in the vehicle to accom- plish the switching of batteries. Switching is performed when the vehicle is not in a critical operation mode, such as ac- tive transport, but when idle for a period between movements.

The switching is controlled by battery discharge sensor sta- tus or as commanded by a vehicle controlling system proces- sor. Switching may be actived when the active battery reaches a level of discharge such that the vehicle operation can be negatively affected and/or when the active battery reaches a level that the rechargeable battery should be discharged to to prevent memory effects from recharging without sufficient- ly draining the battery. The switching operation occurs if the battery being trickle charged has sufficient power provi- ded from the discharge sensor to power the vehicle. Additio- nal redundant batteries being trickle charged could be used

to assure that a battery exists with enough charge to power the vehicle without it having to go off-line. The switch con- troller switches over from one battery to the other battery when a predefined charging level of one of the batteries is reached. Such a level is indicated by a control signal.

The vehicle can be alternately equipped with a device to di- rectly charge batteries through a charging station. Off-line charging for dedicated solar charging can occur, or alterna- tely through a direct contact power station to directly and rapidly charge the batteries with current at the specified voltage in the event the solar recharging is not sufficient.

The charging station may also have the ability to refresh the batteries by draining power to the recommended limit with subsequent full recharging to extend the battery life as long as possible.

A small level of information processing and storage ability is resident on the vehicle to indicate the number of times that the batteries have been cycled or switched in operation, and how long each battery lasted during operation. This moni- tors the recharge-ability of the batteries and indicates when the batteries should be replaced to maintain maximum effi- ciency. This information can alternately be transferred to the host or any other node by direct contact, e. g. during charging station time, or transmitted through RF, IR or other wireless method. A database of this information is kept on each vehicle or vehicle controlling system processor and re- ports can be generated to indicate which vehicles need main- tenance. This communication method may also be used to indi- cate when the vehicle goes off-line or is in operation, thereby providing real-time information of the vehicle availability or use to the vehicle controlling system proces- sor.

Preferably, two or more tracks are provided, said tracks forming a system of tracks. By use of a system of tracks, the

conveying means can be moved very easy to any desired loca- tion within said environment. In case of a semiconductor fab- rication for example, said conveying means can be easily moved to a processing station, a tool, a storage area or the like. Advantageously, the system of tracks may be comprised of one or more branching points.

According to the present invention, there is no need for a system of tracks with only one special configuration. The system of tracks can be adapted to the environment, for exam- ple the fabrication, wherein it is installed. The different tracks are arranged in such a manner that every desired loca- tion can be reached by said conveying means carrying a load.

Therefore, the system of tracks may comprise one or more of the above branching points, which connect the different tracks to become said system of tracks. In this case, the different tracks function as a sort of branches which lead to different locations. The number and configuration of said tracks and said branching points depends on the respective requirements.

The present invention is not limited to a specific number of conveying means, which can be moved through the environment along said tracks. In its basic configuration, the arrange- ment according to the present invention can comprise at least one conveying means. However, it is also possible to use two or more conveying means. The invention is not limited to a special number of conveying means.

When more than one conveying means are used, the system of tracks may be comprised of one or more bypass-tracks. The purpose of such bypass-tracks is to move two or more differ- ent conveying means past one another. In this case, the re- quired number of tracks for moving more than one conveying means at the same time can be minimized.

Advantageously, said track or tracks is/are formed as an overhead track or overhead tracks. In this case, the track or tracks are preferably mounted at the ceiling of the environ- ment. Therefore, the loads carried by the conveying means of said arrangement can be moved above the people working in said fabrication and the different processing locations and units. Thus, no obstructions with respect to the transporta- tion of the loads betweeen different locations can arise.

Preferably, said track or tracks is/are formed as a guiding rail or guiding rails. For example, the rail or rails can be formed as profiles. However, the invention is not limited to specific types of profiles. The profiles can have such a con- figuration or cross-section that the conveying means is guided within or outside of said profiled guiding rail or rails.

In order to allow a continous movement of said conveying means, it is necessary that said means for converting energy is provided with enough energetic light radiation. In case that the conveying means is also provided with a rechargeable intermediate battery, it would be sufficient to have a light source, which emits an energetic light radiation at only one or at a few location (s). Then, the conveying means has to pass said light source in regular intervals, in order to al- low the battery to be charged.

The light source is preferably mounted on top of the track or tracks.

According to another embodiment, the light source can be adapted to emit energetic light radiation at various loca- tions along said track or tracks. In this case the conveying means carrying said means for converting energy can pass sev- eral locations, at which an energetic light radiation is emittet. That enables the means for converting energy to be

continously charged with the required energetic light radia- tion.

In order to achieve such a solution, said light source can comprise one or more light elements which emit an energetic light radiation independently from each other. These light elements can advantageously be the same lighting units which are also used to illuminate the entire environment or fabri- cation and which are usually mounted at the ceiling of said environment in a regular and a relatively close by pattern.

In this case, no additional or separate light source has to be used in order to provide said means for converting energy with energetic light radiation. Since the track or system of tracks can be mounted at the ceiling of said environment or fabrication, a vehicle moving along said track or tracks will regularly pass those lighting units.

According to another embodiment, said light source can be formed as one or more light channel (s), said light channel or light channels being mounted above (on top) said track or tracks and being provided with one or more openings for emit- ting energetic light radiation. According to this embodiment, the light source can be formed as a lighting conduit through which an energetic light radiation is passed. At the opening or openings, said energetic light radiation can exit from the light channel (s) an can be directed to the conveying means being moved along said track or tracks beneath said light channel (s). The number of locations at which the energetic light radiation is allowed to exit the light channel (s) is determined by the number of openings arranged in said light channel (s).

The number and course of said light channel (s) can prefere- ably correspond to the number an course of the track (s) for moving said conveying means. Advantageously, the light chan- nel (s) are formed as a light system, which corresponds in its configuration to the system of tracks in such a manner, that

a light channel will always be on top of a track for moving said conveying means.

Preferably, said conveying means is formed as a vehicle. The configuration of said vehicle depends on the configuration of the track or tracks, along which the vehicle is moved. Advan- tageously, the vehicle can be comprised of one or more roll- ers or wheels. In a preferred embodiment, the vehicle can comprise four wheels.

At the vehicle, the electric drive, the means for converting energy and-optionally-the at least one rechargeable in- termediate battery can be mounted.

Furthermore, said conveying means-for example said vehi- cle-can comprise at least one area for receiving a load to be moved. Said area can be formed as a loadboard or the like.

Preferably, said load carried by the arrangement according to the present invention can be a container for storing disklike objects such as wafers-for example wafers with a diameter up to and beyond 300mm-, flat panels or CDs. However, the invention is not limited to specific kinds of loads or ob- jects, which can be stored within a container.

Preferably, all sorts of objects can be stored within said container which have to be stored under minienvironment con- ditions. The term"minienvironment"has already been ex- plained in the introducory part of the description.

In the latter case, the container can be a minienvironment container, particularly a Front-Opening-Unified-Pod (FOUP).

For example, such a container is definded in SEMI-Standards E44 ans E62, the contents thereof are incorporated into the description of the present invention by reference with re- spect to the FOUPs. The container can also be designed ac- cording to SEMI-Standard E47.1, the content of which is also

incorporated by reference into the description of the present invention.

Advantageously, the aforementioned arrangement can preferably be used as an Overhead-Transport-System (OHT). Such a system can preferably be used in the field of semiconductor manufac- turing. As evident from the term"overhead", said system is mounted at the ceiling of an environment or a fabrication.

Furthermore, the aforementioned arrangement can also be used in environments with clean room class one or less. Neverthe- less, the invention can also be used in dirtier environments, especially, when loads with minienvironment conditions are used.

The invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein Figure 1 shows a schematic side view of an arangement accor- dimg to the present invention and Figure 2 shows an electronic circuit diagram of the battery recharge circuit.

In Figure 1, an arrangement 20 for moving loads 12 is illus- trated, said arrangement 20 being used in an environment 10 or fabrication for manufacturing semiconductor products such as wafers, flat panels, CDs or the like.

The arrangement 20 is arranged as a socalled Overhead- Transport-System (OHT), said system being mounted at the ceiling 11 of said environment 10. For a better understand- ing, ceiling 11 is indicated in Figure 1. The attachment of arrangement 20 at ceiling 11 can be accomplished in a known manner. Therefore, this attachment is not described in detail in the present embodiment.

The arrangement 20 comprises a track 21 or a system of tracks, along which a conveying means 22 can be moved. In Figure 1, a sector of only one track 21 is illustrated, in order to explain the general function of the present inven- tion. Nevertheless, a system of tracks can be provided, which can be formed in a manner as described above and which en- ables the conveying means 22 to be moved to any desired loca- tion of said environment 10. The track 21 can be formed as a profiled guiding rail, outside of which said conveying means 22 is moved.

Said conveying means 22 is formed as a vehicle comprising a vehicle body 33. Furthermore, four wheels or rollers 24 are provided, which are attached to said vehicle body 33 to allow its movement along the outside of profiled track 21.

Vehicle 22 comprises an area 23 for receiving a load 12, said load 12 being formed as a container in the present example.

Area 23 can be formed as a loadboard. Vehicle 22 is driven by an electric drive 29 mounted at said vehicle 22. Moreover, vehicle 22 comprises a means 31 for converting energy. Said means 31 consists of a number of cells 32, which can be formed as photoelectric cells, solar cells or the like. These cells 32 are adapted to convert an energetic light radiation 28 received from a light source 25 into electric energy for said electric drive 29. The required number of cells 32 de- pends on the amount of electric energy which is necessary to run said electric drive 29. Finally, at least one recharge- able battery 30 is provided on vehicle 22, said battery 30 or batteries serving as an intermediate storage device for elec- tric energy. For that reason, rechargeable battery 30 or bat- teries is/are connected to means 31 as well as to electric drive 29.

In order to provide an energetic light radiation 28, a light source 25 is provided, said light source 25 being mounted on

top of track 21 and vehicle 22. Since arrangement 20 is formed as an Overhead-Transport-System, light source 25 is mounted between track 21 and ceiling 11.

In the present example, light source 25 is formed as one or more light channels 26. The number and adjustment of light channels 26 corresponds to the number and adjustments of tracks 21. If tracks 21 are formed as a system of tracks leading to different locations of environment 10, the light channels 26 are also formed as a system of light channels 26 showing the same pattern as the system of tracks 21. For that reason, the light system created by the system of light chan- nels 26 is placed straight on top of the system of tracks 21 and therfore, it is placed always straight on top of vehicle 22 moving along said tracks 21.

The light channel (s) comprise (s) a number of openings 27 through which the energetic light radiation 28 passing through channel (s) 26 can exit from said channel (s) 26. The number of openings 27 depends on the number of locations, at which an energetic light radiation shall be made available for said means 31 converting said light energy into electric ennergy and being mounted on vehicle 22.

Now, the function of such an arrangement 20 as disclosed above will be described.

In order to move a load 12 through an environment, load 12 is deposited in the area 23 of vehicle 22, for example on a loadboard, firstly. Subsequently, vehicle 22 is moved along track 21 or the system of tracks to the desired destination.

The movement of vehicle 22 is performed by electric drive 29.

In order to supply electric drive 29 with a required amount of electric energy, cells 32 of means 31, which can be formed as solar cells, are exposed to the energetic light radiation 28 that exits from light channel (s) 26 through openings 27.

The energetic light radiation is collected by solar cells 32 and is transformed into electric energy therein. The elctric energy can be used to charge electric drive 29.

The principle of said arrangement 20 is to continously pro- vide the required energy for a chargeable vehicle drive 29 by solar energy. The solar energy is provided by said system of light channels 26, which is mounted straight on top of the vehicles 22 rail track 21 or tracks. This will enable unin- terrupted operation of vehicle 22, as its electric drive 29 will always be properly charged. In order to enhance the pro- vision of electric energy for electric drive 29, rechargeable battery 30 can be used, which serves as an intermediate stor- age battery and which stores the electric energy produced by solar cells 32, before this energy is supplied to electric drive 29.

With the arrangement 20 according to the present invention, those drawbacks of common arrangements as mentioned in the introductory part of the description can be overcome.

Figure 2 shows a block diagram of the the battery charging and switch control electronics. There are two redundant bat- teries 40 and 42 provided. Additional batteries 41 and 43, resp., may be connected in parallel. One of the batteries, e. g. 40, will be charged while the other battery, e. g. 42, will be in use powering the vehicle. A switch 54 connects the battery to be charged to the charging current, which may be provided either from a line 57 connected to the solar cells (not shown in Figure 2), or alternatively, from a power line interface circuit 52 where the vehicle connects to in an off- line mode. Interface circuit 52 is provided with power from a power line 56. A switch 53 connects the battery not subject to recharging to supply line 55 which feeds power to the mo- tor of the vehicle.

A control circuit 51 controls the switches 54 and 53. The control unit 51 monitors the discharge status of the active battery, e. g. 40, as well as any parallel battery by 41. When the battery 40 reaches a level of discharge so that the vehi- cle operation could be negatively affected, the control unit 51 switches over to battery 42 which is sufficiently re- charged at that time. The control circuit 51 assures that the vehicle is not in a critical operational state, e. g. not mov- ing or lifting a weight. Further, control circuit 51 switches over to the other battery after appropriate time periods to avoid memory effects which occur when the battery is being charged without sufficient draining. When connected to the power line interface 52, rapid refreshing as well as draining to prevent a memory effect can be performed.

The control unit 51 may have RF or IR radiation capability, e. g. an antenna 58, to communicate the use/recharge cycles to a host. A database collecting to such information indicates maintenance intervals or indicates the need for replacement to the operation personnel.