Overhead substrate handling and storage system

A material handling system includes an overhead rack defining a plurality of storage positions. The overhead rack defines at least one interior window devoid of storage locations. First and second side rails are disposed above the overhead rack. A first cross rail is movably coupled to the first and second side rails. A first transport vehicle movably is coupled to the first cross rail and operable to descend below the overhead rack through the at least one interior window.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

BACKGROUND

The disclosed subject matter relates generally to semiconductor manufacturing and, more particularly, to an overhead substrate handling and storage system.

Growing technological requirements and the worldwide acceptance of sophisticated electronic devices have created an unprecedented demand for large-scale, complex, integrated circuits. Competition in the semiconductor industry requires that products be designed, manufactured, and marketed in the most efficient manner possible. This requires improvements in fabrication technology to keep pace with the rapid improvements in the electronics industry. Meeting these demands spawns many technological advances in materials and processing equipment and significantly increases the number of integrated circuit designs. These improvements also require effective utilization of computing resources and other highly sophisticated equipment to aid, not only design and fabrication, but also the scheduling, control, and automation of the manufacturing process.

Turning first to fabrication, integrated circuits, or microchips, are manufactured from modern semiconductor devices containing numerous structures or features, typically the size of a few micrometers or less. The features are placed in localized areas of a semiconducting substrate, and are either conductive, non-conductive, or semi-conductive (i.e., rendered conductive in defined areas with dopants). The fabrication process generally involves processing a number of wafers through a series of fabrication tools. Each fabrication tool performs one or more of four basic operations discussed more fully below. The four basic operations are performed in accordance with an overall process to finally produce the finished semiconductor devices.

Integrated circuits are manufactured from wafers of a semiconducting substrate material. Layers of materials are added, removed, and/or treated during fabrication to create the integrated, electrical circuits that make up the device. The fabrication essentially comprises the following four basic operations:layering, or adding thin layers of various materials to a wafer from which a semiconductor is produced;patterning, or removing selected portions of added layers;doping, or placing specific amounts of dopants in selected portions of the wafer through openings in the added layers; andheat treating, or heating and cooling the materials to produce desired effects in the processed wafer.

Although there are only four basic operations, they can be combined in hundreds of different ways, depending upon the particular fabrication process.

To facilitate processing of wafers through a process flow, wafers are typically grouped into lots. Each lot is housed in a common wafer carrier. Carriers are transported to various process and metrology tools throughout the fabrication facility to allow the required processes to be completed to fabricate integrated circuit devices on the wafers.

Modern wafer fabrication facilities employ automated material movement systems to satisfy ergonomic concerns and to maintain a high level of automation. Interbay/intrabay vehicle automated material handling systems may be employed to automate the transfer of wafers to the tools required in the process flow. One factor contributing to the efficiency of the material handling system is the delivery time between tools. Delivery time may vary depending on the distance between tools, the congestion of the tools, and the distance an idle material handling vehicle needs to travel to pick up a waiting wafer carrier. Delivery times directly affect tool utilization and system throughput.

Due to the large number of substrates being fabricated concurrently, a large number of wafer carriers may be disposed in wafer storage areas, referred to as stockers, while they await further processing. The automated material handling system coordinates transfer of the carriers to and from the storage locations and between the various processing and metrology tools. Moves to and from storage interrupt the process flow of the substrates and also add to material handling system congestion and delay.

This section of this document is intended to introduce various aspects of art that may be related to various aspects of the disclosed subject matter described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the disclosed subject matter. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. The disclosed subject matter is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.

BRIEF SUMMARY

The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the disclosed subject matter. This summary is not an exhaustive overview of the disclosed subject matter. It is not intended to identify key or critical elements of the disclosed subject matter or to delineate the scope of the disclosed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

One aspect of the disclosed subject matter is seen in a material handling system including an overhead rack defining a plurality of storage positions. The overhead rack defines at least one interior window devoid of storage locations. First and second side rails are disposed above the overhead rack. A cross rail is movably coupled to the first and second side rails. A first transport vehicle movably is coupled to the cross rail and operable to descend below the overhead rack through the at least one interior window.

DETAILED DESCRIPTION

One or more specific embodiments of the disclosed subject matter will be described below. It is specifically intended that the disclosed subject matter not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. Nothing in this application is considered critical or essential to the disclosed subject matter unless explicitly indicated as being “critical” or “essential.”

Referring now to the drawings wherein like reference numbers correspond to similar components throughout the several views and, specifically, referring toFIGS. 1-5, the disclosed subject matter shall be described in the context of a matrix material handling system (MMHS)100.FIGS. 1-3are various isometric views of the MMHS100, andFIG. 4is a top view of the MMHS100. The MMHS100is disposed over a plurality of manufacturing tools110, such as tools used in the fabrication of semiconductor devices. In a semiconductor fabrication environment, exemplary manufacturing tools110include processing tools (e.g., photolithography steppers, etch tools, deposition tools, polishing tools, rapid thermal processing tools, implantation tools, etc.), metrology tools, sorters, etc.

The particular tools110disposed below the MMHS100, and their arrangement may vary depending on the particular implementation and the processing steps being performed. In one example, tools110in a common tool family may be grouped in common control areas. Hence, photolithography tools may be located in one control area, while etch tools may be located in another control area. In another example, the tools110may be grouped by process layer. Hence, the tools required to form a particular layer (i.e., starting with a photolithography step and terminating prior to the next photolithography step) may be grouped into a common control area.

The MMHS100includes one or more linear material handling vehicles120and one or more matrix material handling vehicles130. Generally, the linear material handling vehicles120move along overhead rails140disposed in aisles150between the tools110. An overhead rack160defines a plurality of storage positions170over the tools110for receiving wafer pods180. The linear material handling vehicles120move wafer pods180between different areas of a manufacturing facility, to one of the tools110, or to one of the storage positions170in the overhead rack160. For example, predefined input/output (I/O) port positions190may be defined along the periphery of the overhead rack160to receive or dispatch pods180from or to the overhead rack160. In one embodiment, an I/O port190may be provided on each side of the overhead rack160.

The matrix material handling vehicles130move pods180to various positions within the overhead rack160or to one of the tools110. The matrix material handling vehicles130are movably coupled to a gantry drive system including side rails200and a cross rail210, as shown inFIG. 5. The cross rail210includes a drive mechanism for moving along the side rails200, and the matrix material handling vehicles130include a drive mechanism for moving along the cross rail200to access the various storage positions170. The linear material handling vehicles120and the matrix material handling vehicles130also include hoist systems for raising or lowering the pods180to engage the overhead rack160or to interface with a load port220of one of the tools110.

Drive systems for moving the vehicles120,130along the rails140,200,210and hoist systems for raising and lowering the pods180to interface with the overhead rack160or the tools110are known to those of ordinary skill in the art, so they are not described in greater detail herein to avoid obscuring the present subject matter.

Certain storage positions181may be equipped with equipment to establish a vacuum and/or to provide nitrogen gas, extremely clean dry air (XCDA), or some other purge gas) for pods180stored therein. These pods180may be stored under protected conditions (e.g., to avoid oxidizing exposed regions of the wafers) near the tools110needed for the next process operation. This protected storage near the tool110increases throughput and yield. An exemplary storage location181equipped with a purge nest182is shown inFIG. 6. The purge nest182includes a frame183for supporting a wafer pod180. A purge port184fed by a gas supply line185is provided to supply a cover gas for the interfacing pod180(not shown). A vacuum port186coupled to a vacuum line187may be used to remove the purge gas exiting the pod180.

The overhead rack160defines one or more interior windows230to allow a matrix material handling vehicle130to interface with a load port240of a tool not disposed along the periphery of the overhead rack160(i.e., along an aisle150). The matrix material handling vehicle130may be provided with rotating grippers to allow a wafer pod180to be rotated as well as lowered, so that the pod180may be aligned at any angle (e.g., aligned with various cluster tool facets). The overhead rack160also defines periphery windows250to allow access to the aisle-oriented load ports220.

The overhead rack160may be constructed of a plurality interlocking grid pieces that can be dynamically configured to arrange the windows230relative the load ports240. For tools110that are susceptible to particulate contamination (e.g., while they are opened during preventative maintenance procedures), a fan filter unit (FFU) containing a high efficiency particulate air (HEPA) filter may be mounted immediately beneath the overhead rack160. For tools110that have utilities or exhaust ducts passing through the ceiling, the utilities and exhaust may be grouped to penetrate an interior window230selectively placed in the matrix, or grouped adjacent to the overhead rack160so as to not inhibit the travel of the matrix material handling vehicles130over tool load ports220.

Either the linear material handling vehicles120or the matrix material handling vehicles130can access the aisle-oriented load ports220to load the tools110. Generally, a linear material handling vehicle120lowers the pod180and reaches out to engage the load port220, while the matrix material handling vehicle130traverses through the periphery window250to engage the pod180with the load port220.

FIG. 7illustrates a cut-away side view of the MMHS100illustrating how tool density may be increased due to the overhead and matrix vehicles120,130. In the embodiment illustrated inFIG. 7, the system100includes linear material handling vehicles120A-F and matrix material handling vehicles130A-B. The inside linear material handling vehicles120C,120D may be provided to allow traffic to bypass the illustrated portion of the MMHS100. The linear material handling vehicles120A,120B,120E,120F may be used to load tools110A-E or to transfer pods180in to and out of their respective portions of the overhead rack160A,160B. The tools110A-E may be arranged with load ports220A-D that are disposed on edges of the MMHS100and load ports240A,240B that are disposed not on the edges. Interior windows235A-B and periphery windows250A-D are provided to allow the matrix material handling vehicles130A-B to access the various load ports220A-D,240A-B.

For example, the load port220A disposed along the edge may be accessed by the linear material handling vehicle120A or by the matrix material handling vehicle130A through the periphery window250A. The load port240A that is not disposed along the edge may be accessed by the matrix material handling vehicle130A through the interior window235A. The layout of the tools110A-E may be varied depending on the amount of available floor space and the size and port positions of the tools to improve the density of the layout.

Because the matrix material handling vehicle130can interface with a tool110through an interior window230, the tools110need not be arranged in a completely linear fashion, as is the case in a conventional machine layout. Because the size and port orientation of the various tools110may vary, avoiding a linear layout allows a denser tool layout, thereby conserving floor plan space to increase fab capacity and reducing the traversal distance between tools110to increase throughput. Due to the number of storage positions170in the overhead rack160conventional stockers need not be provided in the MMHS100, thereby reducing overall system cost and increasing throughput by avoiding moves to and from the stockers.

In one embodiment, the tools110disposed along the aisles150may be provided with conventional SEMI ports240for receiving conventional front opening unified pods (FOUP). These conventional ports240may be accessed by either the linear material handling vehicles120or the matrix material handling vehicles130. Tools110disposed near the interior windows230may be provided with advanced ports for receiving advanced wafer pods. For example, pods180may be provided that do not open to external atmosphere for loading or unloading. A protective gas may be provided during the transfer operation. The advanced load port may be provided for a cluster tool110, a carrier capable of directly interfacing with a vacuum, etc. The use of advanced pods allows direct process to process moves, which increased both yield and throughput. These direct moves also eliminates the need for FOUP handling steps, thereby reducing hardware requirements and improving cycle times.

The overhead rack160may be shared by more than one matrix material handling vehicle130. For example, as shown inFIG. 2, four or more cross rails200may be provided over the rack160, each with its own matrix material handling vehicle130. Shared regions may be defined in the overhead rack160that can be accessed by different matrix material handling vehicles130. One matrix material handling vehicle130can place a pod180in a storage position170after processing by a tool110, and another matrix material handling vehicle130can retrieve the pod180at a later time to move it to a different tool110for the next operation. If one matrix material handling vehicle130fails, another matrix material handling vehicle130can bump the cross rail200out of the way to access storage positions170in the overhead rack160that had been serviced by the failed matrix material handling vehicle130.

The MMHS100eliminates single points of failures because the overhead rack160can be loaded from by the linear material handling vehicles120using overhead rails140on either side. In cases where there is no failure, this effectively doubles the throughout density. Overlapping portions of the overhead rack160may be accessed by different matrix material handling vehicle130. The two-dimensional capabilities of the matrix material handling vehicles130also allow fast swapping at the tools110and access to tools110disposed beneath the overhead rack160. Traffic blockages associated with conventional linear material handling systems may be avoided due to the increased number of movement axes.

The proximity of the overhead rack160to the tools110allows shared local buffering for tools110of the same type. Multiple pods180requiring the same operation may be stored proximate tools110of the same type without requiring the scheduling system to identify the particular tool110that will perform the next operation. The matrix material handling vehicles130may deliver the pod180to the selected tool110after the dispatch decision is made without incurring a material handling delay. Kits of test wafers may also be stored proximate to tools110where they may be employed (e.g., to qualify a tool after maintenance) to save cycle time and reduce material handling traffic.

Scheduling for the MMHS100may be provided by centralized and local schedulers. A centralized scheduler schedules global moves within the system100, while local controllers control moves for pods180stored on the overhead rack160for a group of tools110to effect the processing of the wafers over a plurality of process steps. An exemplary scheduling system is described in U.S. patent application Ser. No. 13/247,792, entitled “Methods and Systems for Semiconductor Fabrication with Local Processing Management”, and incorporated herein by reference in its entirety.

The particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosed subject matter. Accordingly, the protection sought herein is as set forth in the claims below.