The development is also covered by US patent application 11/580,697 of October 13 2006 and by 10/682,809 filed on October 9 2003 of the same title. The application also claims benefit of US provisional patent application Number 60/417,993 filed on October 11 2002 and titled ‘Offset Zero Footprint Storage (ZFS) using Moving Shelves or a Translating Hoist Platform’.

Fig 1

Fig 1 – Block diagram of an integrated chip manufacturing facility including an automated material handling system according to the invention

Outline and background

The new system offers access to one or more levels of material storage shelves using an overhead hoist transport vehicle operating from a single track-position. The hoist is carried from a suspended track to access Work-In-Progress (WIP) parts from storage locations beside the track. The system includes an overhead vehicle for transporting the hoist plus one or more storage bins for the WIP parts. Each storage bin is either a movable shelf or a fixed shelf.

In order to access a WIP part on a selected shelf the overhead hoist transport vehicle moves along the suspended track to a position at the side of the shelf. Next the movable shelf moves to a position at the side of the shelf, or, in the case of a fixed shelf, the hoist moves to a position above the fixed shelf. The overhead hoist is then operated to pick a desired WIP part from the shelf.

In view of the comparatively complex nature of this development this summary will leave out some possible embodiments of the development described in detail in the full WIPO publication.

The intended background of this development is in automated material handling systems, especially for WIP parts access. Systems are already available for this task and to transport parts between workstation and/or processing machines in a product manufacturing environment. A typical application is in the fabrication of integrated circuit (IC) chips in which there are various processing stages such as deposition, cleaning, ion implantation, etching and passivation, and transportation between workstations taking place several times. In such a case the WIP parts are semiconductor wafers.

Fig 2

Fig 2 – Block diagram of a second embodiment of offset zero footprint storage as the handling system of Fig 1. Here is a single row of fixed shelves with overhead hoist mounted on a translating stage

A conventional system in this context includes several WIP storage units, and one or more transport vehicles with overhead hoists. Semiconductor wafers are typically loaded into carriers such as Front Opening Unified Pods (FOUPs), each of which may be selectively accessed via the overhead hoist and vehicle. Typically the FOUPs are stored in WIP storage underneath the transportation track. The hoist transport vehicle is then positioned directly above a selected FOUP and the hoist lowered towards the FOUP and operated to pick the FOUP from the WIP storage unit or to replace the FOUP there.

A drawback of such a system is that the hoist can access only a single level of WIP storage beneath the suspension track. This can increase costs due to inefficient use of floor space. To alleviate this the WIP storage unit must be able to move a selected FOUP from its position to another that can be accessed by the hoist, but this can significantly lower the throughput of the system. Such a storage unit typically has many moving parts subject to failure, increasing costs and reducing reliability.

Fig 3

Fig 3 – Perspective of the translating stage of Fig 2

In addition a minimum amount of space is usually required between the ceiling and floor of the facility to accommodate the track and the overhead hoist transport vehicles, further restricting storage space. To serve one level of WIP storage, multiple overhead hoists must queue up at a storage unit, again lowering system throughput.

This all makes it desirable to have an automated system with enhanced efficiency whilst overcoming the above drawbacks. Such systems are becoming increasingly important when semiconductor wafers are increasing in size to 300mm and consequent weights are up to 10kg.


The system of the patent application makes more efficient use of space with higher throughput, enhanced reliability and reduced costs. In a main embodiment it includes at least one overhead hoist transport system with track, at least one translating arm for supporting at least one material unit, and an overhead hoist transport vehicle to carry the translating arm to various track locations and for raising and lowering it to various levels corresponding at least in part to the track locations.

The translating arm includes a mechanism for conveying a material unit along the length of the arm. The material storage location is at a predetermined level on a first side of the track. In one way of operating the hoist transport vehicle carries the translating arm to a track location adjacent to the material storage location, and then moves it vertically to position it approximately at the predetermined level of the material storage location. At this position the translating arm can move laterally from within the transport vehicle to another position outside of the vehicle thereby allowing the conveying mechanism to move at least one material unit from storage onto a portion of the length of the arm, or the reverse.

Fig 4

Fig 4 – Perspective of an alternative embodiment of the overhead hoist
of Fig 2

In fact the translating arm in this system embodiment is formed of a pair of arms and the storage location is a shelf. When this pair of arms is at the second position outside of the transport vehicle, they are positioned adjacent to and on opposing sides of the shelf. The width of the material unit, or FOUP, is greater than that of the shelf, causing some of it to overhang the opposing sides of the shelf.

The conveying mechanism is configured to contact the overhanging portions of the FOUP when the arms are positioned on opposing sides of the shelf. The conveying mechanism may include several active rollers, and the shelf may have several passive rollers to facilitate movement of the FOUP.


In Fig 1 the Automated Material Handling System (AMHS) is shown (100), configured to store WIP parts and transport them between locations such as processing machines (114-115) with input/output ports (118-119) within the manufacturing environment. This may be a clean environment for making integrated circuit chips. The ceiling (104) and floor (105) is typically covered with electrically nonconductive material. The published patent application details the dimensions and spacing of such a facility.

The overhead hoist transport vehicles (102a-102b) are movably coupled to tracks (106a-106b) suspended from the ceiling. FOUPs (108a-108b) are designed to hold the WIP parts and are stored in bins such as shelves (110a-110b). The track routes are predetermined to run either side of the shelves so that the FOUPs can be accessed directly from the shelves. The shelf may be one of several in a row beside and parallel to the suspended track (106a), and one or more rows of fixed shelves may be positioned on either or both sides of the track.

As shown in Fig 1 the transport vehicle moves along the track to a position at the side of the shelf. So that the FOUP (106a) can be accessed from the fixed shelf (110a), a translating stage (112) in the transport vehicle moves the overhead hoist laterally from within the vehicle to a position directly above the fixed shelf as shown by the arrow (109a). The hoist then picks up the FOUP from the shelf for onward transport. It could also place one or more FOUPs on the shelf. The translating stage can allow the hoist to pick or place an FOUP at either side of the overhead hoist transport vehicle.

In this case the vehicle includes a cowl (103a) with a through opening to allow the translating stage to move from within the vehicle to the shelf. After picking, the FOUP passes through the cowl opening on the translating stage.

The shelf 110a is fixed but the shelf 110b is movable. This shelf may also be in multiple configurations as with the fixed shelf type. In this case the shelf moves laterally to its position beside the track to a position directly underneath the hoist within the vehicle and indicated by arrows 109b. The movement mechanism may be pneumatic, a stepper motor or servo motor controlled axis. The hoist then picks up the FOUP from the shelf for subsequent transport, or places one or more FOUPs on the shelf. Once the FOUP is held by the hoist, the shelf moves back to its original position bedside the suspended track.

The whole system operates under computerised control with the computer including one or more processors for executing instructions based on the memory. The instructions may be stored as program code as part of the operating system, as part of an application, or allocated between the operating system and the application. Any suitable program storage can be used as memory.


Fig 2 shows the Automated Material Handling System with the suspended track (406) with vehicle (402). This is configured to pick or place an FOUP (408) from a passive or fixed shelf (410). A typical suspension distance (421) is about 0.9m, and distance between the fixed shelf and floor 2.6m. The ceiling to floor distance may be around 3.5m. The shelves may be disposed in single or multiple rows as above and one or more rows may be located on either or both sides of the track. Thus the fixed, suspended shelves provide multiple levels of offset Zero Footprint Storage (ZFS).

Fig 3 shows the translating stage laterally extended to move the hoist to a position besides the transport vehicle, and directly above a selected fixed shelf. A hoist gripper is used to directly pick or place the FOUP from or to the shelf (410). The extended translating stage then moves back to its original position within the vehicle, and the FOUP moves into the transport vehicle through the cowl opening. The vehicle can then proceed to the next station.

Fig 4 show one of several variations on the basic development or specifically an overhead hoist transport vehicle (1502) configured, again, to travel on the overhead track to a position adjacent to a storage shelf. This may be suspended or otherwise disposed above, below, or at the same height as the transport vehicle. As with the vehicle (402) in Fig 2, this type is configured to pick or place an FOUP in multiple levels of Zero Footprint Storage. The translating arms (1513) of the vehicle simultaneously retract within the vehicle or extend outside of it. Each includes a series of active rollers (1515) on the upper edge of each arm, and there are passive rollers on the surface of the storage shelf. Rotation of the active rollers moves the FOUP along the upper edge of the arms. Whilst picking or placing the FOUP from or to the fixed shelf. The conventional mechanisms for moving the active rollers are omitted for clarity.

This is an edited version of the original patent and may omit legally or technically important text.