Wafer Transport Device

Abstract

A transport container for transporting a semiconductor wafer generated in a specified shape from a base material by 3D printing, At least a region of the surface of the transport container comprises a coating material for protecting the semiconductor wafer from chemicals capable of etching the semiconductor wafer, the coating material being applied by a low-temperature coating process, more particularly a low-temperature sintering process, preferably at a temperature below 150°C, the coating material being composed of polytetrafluoroethylene, perfluoroalkoxy polymer or polyvinylidene fluoride, the defined shape of the transport container comprises a device at its base suitable for removing the liquid medium, the defined shape of the transport container comprises one or more integrated workpiece holders for semiconductor wafers and / or carriers for semiconductor wafers so that the semiconductor wafer to be transported can be loaded in an upright position, and the specified transport direction of the transport container in the automated transport system is parallel to the front side or the back side of the semiconductor wafer.

Description

[Technical field]

[0001] The present invention relates to an apparatus in the form of a transport container for semiconductor wafers suitable for use in an overhead hoist transport system. [Background technology]

[0002] Prior Art During the manufacturing and processing of semiconductor wafers made from silicon or other semiconductor materials, transport containers are used between the individual operational steps to transport the semiconductor wafers and / or to enable them to be maintained in a defined orientation.

[0003] The transport container here is generally configured such that a wafer cassette together with wafers can be placed in the container and transported manually or by an automated guided vehicle (AGV).

[0004] The transfer of wafer cassettes into and out of the transport container takes a lot of time depending on the level of automation.

[0005] Furthermore, multiple movements of the wafer during transport result in an increased risk of damage to the wafer being transported.

[0006] First, there are floor-targeted transport systems, for example, operated by automated guided vehicles (AGVs) or hand carts on the cleanroom floor.

[0007] Secondly, there are ceiling-targeted transport systems that operate on a rail system fixed to the ceiling of the clean room, in which case it is particularly advantageous to use an overhead hoist transport system.

[0008] Floor-directed transport systems using AGVs or hand carts require dedicated transport paths between operational units, which in cleanrooms requires additional cleanroom area at cost and potentially longer transport paths, as the operational equipment occupies straight paths.

[0009] Using an overhead hoist transport (OHT) system, for example, would overcome the above-mentioned drawbacks since the wafers could be transported under the ceiling, thus eliminating the need for additional clean room areas, an example of which is disclosed in US Patent Application US2015104276AA.

[0010] Transport containers for semiconductor wafers may be manufactured as thermoformed, injection molded, cast or welded containers, but as noted above, there are limitations to the achievable forming and functional characteristics of the container resulting from these manufacturing processes.

[0011] Document US 2004 / 206663 A1 discloses a container with a superhydrophobic surface to facilitate more effective cleaning and drying of the container.

[0012] Document WO 2004 / 005163 A1 relates to a transport container for wafers, the container being made of parts manufactured from flame-retardant materials.

[0013] Document US 2005 / 236110 A1 generally relates to a system and method for applying thin protective thermally polymerized films, such as PEEK, to molding operations for handheld tools, transport equipment, carriers, trays and similar devices usable in the semiconductor processing industry.

[0014] Document DE 42 23 326 A1 relates to a carrier for semiconductor wafers, which comprises a carrier substructure, with a diamond coating applied to at least part of the substructure.

[0015] A carrier system in semiconductor manufacturing, also called a "loadport", is configured with both mechanical and electrical interfaces between a transport container and an operation unit. The transport container is placed on the system by a transport system to load and unload processing units. Here, load ports that allow the attachment of common semiconductor transport boxes such as FOUP (Front Opening Unified Pod), FOSB (Front Opening Shipping Box), OC (Open Cassette), and SMIF (Standard Mechanical Interface) pods and that meet SEMI standards are widely used. Summary of the Invention [Problem to be solved by the invention]

[0016] Therefore, there is a need for an improved semiconductor wafer transport container that allows for use with overhead hoist transport (OHT) systems, particularly involving wet transport of semiconductor wafers and their manufacture. [Means for solving the problem]

[0017] Disclosure of the Invention The invention proposes a transport container for semiconductor wafers having the features of the independent claims. Advantageous configurations are given in the subject matter of the dependent claims and in the subject matter of the following description.

[0018] The present invention relates to a transport container for semiconductor wafers, such as silicon wafers. The invention involves producing a container with a defined shape from a substrate by an additive construction or manufacturing process, which may more particularly involve 3D printing. Thus, for example, substrate is added layer by layer until the final desired defined shape is produced. A coating material is then applied to at least a predefined area of ​​the surface of the (so constructed) container to protect against chemicals, i.e. the container is made resistant to chemicals by the coating (which acts as a protective coat).

[0019] The coated container may also be referred to as a transport container. The relevant areas of the surface to which the coating material is applied are more particularly those areas that should be protected since they are intended to come into contact with the corresponding medium or chemical during subsequent use. This concerns in particular the inside of the container, which is typically open at the top. However, it is particularly advantageous if the transport container has a lid, more particularly if said lid is impermeable to the liquids wetting its inner surface.

[0020] For example, transport containers optimized for dry or wet transport using AGV and overhead hoist transport systems and optimized in multiple respects with respect to conventional manufacturing processes can be manufactured by additive manufacturing processes or 3D printing. This is possible by free-form design without adding components that would have to be retroactively connected to conventionally manufactured containers, including, in particular, mechanical structural elements integrated as part of the container thus manufactured. In addition, chemical resistance, surface properties, integrated rechargeable power sources, mechanical coupling elements, sensors, fittings for external energy and media supplies, integrated holders for semiconductor wafers, as well as fluid function characteristics for the respective applications can be selected more variably and more adaptively compared to conventional manufacturing processes, as will be described in more detail below.

[0021] Improved, or indeed optimized, chemical resistance is achieved by applying a coating material that acts as or provides a surface seal. Preferred coating materials in this regard include polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA), and polyvinylidene fluoride (PVDF).

[0022] The inventors have recognized that containers manufactured solely from a substrate by an additive manufacturing process such as 3D printing have surfaces that are too rough to be used as transport containers for semiconductor wafers. These surfaces are too rough for the desired application and result in organic and inorganic contaminants building up on and in the surfaces, thereby adversely affecting the quality of the semiconductor wafers during transport.

[0023] However, since the relevant surfaces of the container manufactured by an additive manufacturing process (3D printing) are coated, for example with PTFE, in this case the beneficial properties of conventionally manufactured transport containers (i.e. in particular chemical resistance) can be combined with the beneficial properties of containers for semiconductor wafers (typically silicon wafers) manufactured by an additive manufacturing process (i.e. in particular free-form molding).

[0024] Assuming that containers manufactured by additive manufacturing processes may be deformed due to the severe thermal loads they are subjected to in conventional coating processes, low-temperature coating processes have been developed in combination with additive manufacturing processes.

[0025] The high purity coatings required for operation on semiconductor wafers are traditionally applied to the surface at high temperatures.

[0026] The use of controlled low temperature coating processes, preferably at temperatures below 150°C, can result in high purity coatings being applied to less temperature stable surfaces, for example of a 3D printed container, resulting in benefits such as free forming, controlled delivery and removal of chemicals into and from the shipping container, and chemical and physical properties.

[0027] For example, the material PA3200GF has a dimensional retention temperature (in the X direction at a pressure of 0.45 MPa) of up to 157 ° C according to ISO 75-1 / -2. Comparable figures apply to preferred substrates, in particular those containing polyamide with fillers. Above this temperature, the plastic profile typically collapses under its own weight. PTFE coatings, for example, are generally applied by spraying and sintered in ovens at temperatures between about 220 ° C and 420 ° C. As a result of a long low-temperature sintering process, typically at 100 ° C, it has been possible, for example, to make 3D printed silicon wafer containers resistant to chemicals and contamination.

[0028] The surface roughness of containers manufactured by additive manufacturing processes (3D printing) can be mitigated by low-temperature coatings, typically with Rz and Ra values ​​(defining the roughness) reduced by about 70% with respect to the corresponding values ​​of containers without low-temperature coatings. This therefore also results in a significant reduction in the adhesion of liquid particles or other organic or inorganic components to the (container) surfaces in the transport container, and also allows these particles or components to be removed much easier and in a controlled way when changing the liquid.

[0029] The proposed additive manufacturing process (3D printing) allows for an optimized container design, i.e. a transport container optimized in terms of shape and fit for use in combination with an overhead hoist transport system, for example the liquid volume of the transport container can be weight optimized with easy manufacturability to adapt the shape of the container to the semiconductor wafers contained and transported in said container, so that the amount of media or chemicals required when using the transport container is not unnecessarily large (meaning for example that the volume in which the liquid is contained is kept as low as possible).

[0030] Particularly preferably, the container of defined shape comprises means for removing the medium or chemical, particularly preferably also comprising a plurality of supply means and / or removal means.

[0031] Particularly preferably, one or more integral workpiece holders for one or more semiconductor wafers or their carriers are also present. The workpiece holder can, for example, be designed in such a way that one or more semiconductor wafers can be inserted therein and held directly.

[0032] Likewise, the workpiece holder may preferably also be designed so that a carrier, cassette or another holder can be inserted therein and further so that one or preferably more than one semiconductor wafer can be inserted and held. Wafer holders (cassettes) for 5, 10, 15 or 25 silicon wafers are preferably inserted into the workpiece holder, which allows multiple silicon wafers to be inserted and / or withdrawn together without the need to insert and withdraw them together with a wafer rack.

[0033] In this context, the term "batch processing" is conventional in semiconductor manufacturing. It involves simultaneously or individually inserting or withdrawing an entire load of wafers into a 3D printed carrier and the wafer holders located therein. As a result, the time-consuming operation of loading and unloading wafer cassettes is eliminated. In addition, by eliminating the loading and unloading of cassettes, the risk of vibration-induced damage to the wafers at the interface with the cassette is also reduced.

[0034] Preferably, furthermore, one or more frames and / or one or more fastening means are provided for attachment and automatic connection to various operating units. Reinforcing elements integrated into the container shape are particularly preferred.

[0035] Automatic coupling of the transport container to the operating unit is achieved, preferably with an overhead hoist transport system, by placing the container on mechanical, electrical, data processing and / or fluidic coupling elements integrated for that purpose in the operating unit.

[0036] In this respect, it is preferred to employ three or more mechanical components. In the area of ​​contact with the transport container, these three or more mechanical components can be configured in the form of pins with head pieces that are chamfered, rounded, conical or frustoconical in shape, or in the form of rollers. These configurations on the carrier system can include a rotationally symmetric, axially symmetric or asymmetric distribution over the area. The carrier system may be equipped with additional shape elements that allow the transport container to be placed to be pre-positioned in the horizontal XY direction. Furthermore, stabilizing elements may be arranged on the carrier system that prevent the transport container from tilting laterally.

[0037] Here, the weight of a fully loaded transport container is preferably more than 25 kg and less than 120 kg.

[0038] The necessary corresponding parts, which are preferably integrated into the transport container, result in a mechanical, electrical and / or fluid connection between the operating unit and the transport container when the container is positioned, particularly preferably via a form-fitting connection.

[0039] The supply means and removal means may preferably be of integrated form and may then have any desired design.

[0040] In conventionally manufactured transport vessels, the supply and removal facilities, supply lines and adapters are typically realized by mechanical adapters that include additional conduits, electrical lines and attachments on the vessel.

[0041] Conversely, additive manufacturing processes or 3D printing allow such elements to be integrated, for example, into the container shape, side walls or base, and allow the inlet and outlet ports to be located in a targeted manner at points ideal for providing fast and physically close connections of media, power and data, and for mechanically coupling the container to an operating unit or a transport system, for example an overhead hoist transport system. Preferably, even in this case, this may be designed in a targeted manner according to the desired application of the transport container, for different transport systems, such as AGVs or overhead hoist transport systems, which are primarily used.

[0042] Specifically, in the case of application as a wet transport container for an overhead hoist transport system, additive manufacturing processes such as 3D printing allow for a very accurate and simple design and manufacture of the upper container edge, preferably for receiving the container by a so-called shuttle (OHT transport vehicle) with a lowerable holding device for the container, which, when manufactured accurately, ensures that the container can be used with commercially available overhead hoist transport systems.

[0043] The inventors have realized that for a large number of identically constructed transport containers, integrated mechanical coupling elements can be integrated with high positional accuracy by an additive manufacturing process. The absolute accuracy of positioning the integrated mechanical coupling elements with the wafer holder by an additive manufacturing process is a prerequisite for carrying out identical loading / unloading operations carried out on separate process equipment, without the need to provide separate loading / unloading devices, such as wafer loading / unloading robots, for each transport container. Thus, a high reproducibility of the process sequence can be ensured.

[0044] The present inventors have further recognized that, particularly in conjunction with an overhead hoist transport system, there is a requirement for direct routing between operational units when processing wafers in series.

[0045] The feedback time obtained from a downstream operational step for the purpose of controlling a preceding operational step often plays a substantial role according to specified product requirements.

[0046] The inventors have also recognized that feedback time can be further reduced when using overhead hoist transport compared to conventional wafer cassette transport previously performed by floor-directed transport means in wet transport, thereby allowing for more effective control of preceding operations.

[0047] A requirement for wet transport using overhead hoist transport systems is the use of the transport container of the present invention which is particularly suited for such systems.

[0048] One preferred transport container for transporting semiconductor wafers has been manufactured from a substrate by 3D printing into a defined shape.

[0049] In this case, at least one area of ​​the surface of the transport container includes a coating material for protection against chemicals.

[0050] Chemicals used in the manufacture of semiconductor wafers are sometimes acidic or alkaline, and intentionally applied chemical residues or chemicals are also located in the transport container. A common feature of these chemicals is that they can also contaminate or etch the surfaces of the transport container. As a result of the above-mentioned coating, the surfaces are protected from etching, the adhesion of chemicals and impurities is inhibited, and the cleaning of the container is improved.

[0051] The coating is in this case applied by a low-temperature coating process. Particularly preferred in this context are low-temperature sintering processes. This operation is preferably carried out at temperatures below 150°C.

[0052] The coating here preferably consists of one of the following materials: polytetrafluoroethylene, perfluoroalkoxy polymers or polyvinylidene fluoride.

[0053] The defined shape of the transport container preferably comprises at its base a device suitable for removing the liquid medium, particularly preferably this device is designed as a valve for rapid emptying of the liquid contained in the transport container.

[0054] The valve is in this case more preferably designed to be opened automatically by deposition in the vessel, said deposition taking place at the appropriate point.

[0055] Often, the medium is fed into and removed from the transport vessel for the wet transport of semiconductor wafers in a controlled manner, so that impurities after transport are quickly and controlledly removed. In the transport vessel of the present invention, a very extensive and rapid evacuation can typically be achieved by an integrated quick evacuation system, which is specifically envisaged for the purpose and is typically configured as a so-called quick dump valve, and can therefore be more effectively adapted to prevent repeated deposition of particles after they have been removed from the surface.

[0056] It has proven to be particularly advantageous if the semiconductor wafers for transport can be introduced in an upright position if the transport container comprises one or more integrated workpiece holders for semiconductor wafers and / or carriers for semiconductor wafers.

[0057] A usual feature of commercially available containers is that they are fitted snugly into the transport system so that the axis of the transport direction always coincides with the same axis of the transport container. Therefore, the container cannot be mounted rotated, for example, by 90°. There is therefore a designated transport axis for the container.

[0058] The present inventors have recognized that a semiconductor wafer is loaded into a transport container so that either the front side or the back side of the semiconductor wafer is parallel to a designated transport direction.

[0059] The effect of this is that the moving liquid cannot exert any force or any substantial force on the semiconductor wafer during transportation, which would increase the damage (cracks) if the semiconductor wafer were to be transported rotated by 90 degrees.

[0060] Thus, the holder for the semiconductor wafer to be transported in the 3D printed transport container is preferably arranged to allow the liquid contained therein to move parallel to the wafer surface between the semiconductor wafers during transport, as a result of which the forces due to sloshing of the liquid on the wafer surface are suppressed, the relative movement of the wafer in the wafer holder is minimized, and the occurrence of damage to the wafer surface is avoided.

[0061] It has proven to be particularly advantageous if the transport container used comprises an energy store for electrical energy which can be used to operate the electrical components.

[0062] In addition, it is particularly preferred if elements for electronic data processing, such as for example a mini PC, are integrated into the transport container.

[0063] This greatly enhances the application possibilities, for example allowing suitable installed sensors to record movement profiles that are useful for tracking faults as they occur. [Brief description of the drawings]

[0064] [Figure 1] FIG. 2 is a schematic diagram showing a series of preferred processes in a preferred embodiment. [Diagram 2] FIG. 1 is a schematic diagram of a transport container of the present invention in a preferred embodiment. [Diagram 3] FIG. 2 is a detailed cross-sectional view of the same transport container of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] Figure 1 shows a schematic process sequence in a preferred embodiment. First of all, for this purpose in figure (a) an apparatus 106 for an additive manufacturing process, for example a 3D printer, is shown in a broad schematic representation with a print head 104 supplied with a substrate 105. The print head 104 first applies a first layer 101 of the container under manufacture onto a support 107.

[0066] After this, further layers are applied, in particular by applying a new layer to each preceding layer. In (b) a further layer 102 is exemplarily shown applied to layer 101, and in (c) a further layer 103 is exemplarily shown applied to layer 102.

[0067] In this manner, the container 100 is manufactured from the substrate by an additive manufacturing process in a desired or defined shape, as broadly shown diagrammatically in (d). As also shown in (d), a coating material 108 is applied, for example, to the open-topped interior surface of the container 100. This application is performed, for example, by an application tool 111 that receives a supply of coating material 108 from a tank 109.

[0068] The container 100 involved in this method is then dried, more specifically sintered, for example in an oven 112 within a predetermined temperature range below the dimensional integrity temperature of the substrate 105 (e.g. 150°C) for a predetermined time, as shown in (e) to form a complete, chemically resistant carrier container 110.

[0069] In Fig. 2, a transport container 202 of the invention in a preferred embodiment is shown diagrammatically, as can be produced, for example, by the process shown in and described with reference to Fig. 1. In this case, in particular, the shape of the transport container 202 or its shaping is shown, the coating with the coating material already described in connection with Fig. 1 being not explicitly shown here for the sake of clarity.

[0070] The lid of the container 201 is thus firmly assembled to the OHT vehicle 200, which is then suspended on an attachment 204 suitable for moving it vertically.

[0071] 3 shows two cross sections of a preferred transport container. A lid 300, which can be placed on the container 301 by a sealing system 304, prevents liquid from escaping during transport of the container. A number of semiconductor wafers 302 mounted on workpiece holders 303 can be transported secured within the container. The intended preferred transport direction of the transport container is along the front or back side of the stored semiconductor wafers 302.

[0072] A particularly preferred drive unit 305 ensures that the semiconductor wafers are rotated during transport, thereby eliminating the possibility of contaminant deposition sites forming on the edge of the semiconductor wafer.

[0073] As mentioned many times above, the proposed additive manufacturing process allows for free and therefore optimized design of, for example, wafer-carrying containers. No mounting and installation of components that affect the operation inside the container is necessary, rather the container can also be built without welding and without extra material. Chemical exhaust ports can be arranged at process-relevant positions, thus ensuring complete removal of reactive chemicals present on the wafer and container surfaces from said wafer and container surfaces.

[0074] The build shape can be very precisely formed by the 3D printing process down to the required liquid volume. Typically, a certain number of wafers can be transported during wet transport completely immersed in liquid. As can be seen from FIG. 3, the shape of the transport container is adapted to a certain number of wafers, and therefore the volume of liquid introduced into the container is also reduced, for example to the required minimum.

[0075] The build geometry is typically fluidically optimized for wafer transport, such that particles and chemical residues are transported away from the wafer and vessel surfaces towards the removal port without further particle accumulation on the surfaces. For this purpose, a central port, preferably located in the vessel base, is fitted to accommodate a valve for rapid emptying of the transport vessel.

[0076] A workpiece holder 304 is additionally provided, which is preferably integrated into the transport container by suitable molding during the manufacture of said container. A carrier or wafer carrier can preferably be inserted tightly and flush into this workpiece holder 304.

[0077] Particularly preferably, one or more semiconductor wafers can be inserted directly into the workpiece holder without a wafer carrier. The orientation of the workpiece holder is preferably designed such that, when the container is fully filled, no forces are generated due to sloshing of liquid against the wafer surface during wet transport, thereby causing no relative movement of the wafers within the wafer holder. The slots of the wafer holder are aligned with the transport direction of the container.

[0078] In addition, an integrated frame and attachment (including mechanical coupling elements) can be realized for simple adaptation to the receiving device of a transport system (e.g., an overhead hoist transport system). Particularly preferably, various mechanical coupling elements are simultaneously provided on the underside of the transport container. The coupling elements serve for accurate and consistent positioning on the operating line, for example, for loading the wafers using a robotic system without special measuring techniques for capturing the container position.

[0079] Furthermore, by suitable molding a sensor holder is produced, into which a sensor can be inserted, for example, which sensor may possibly serve, for example, to monitor a defined filling level.

[0080] In this regard, it may be mentioned that the features or components integrated into the shape of the transport container are merely exemplary. Further components and / or features may be provided. Depending on the desired application of the transport container, only certain components and / or features may be provided. [Explanation of symbols]

[0081] Abbreviation 100: Coated containers 101: First layer of container under construction 102: Second layer of container under construction 103: Further layers of containers in production 104: Print head 105: Base material 106: 3D printer 107: Support part 108: Coating materials 109: Tank 110: Transport container 111: Application tool 112: Oven 200: OHT transport vehicle 201: Lid of a transport container fixed to an OHT transport vehicle 202: Transport container 203: Carrier system for transport containers 204: Vertical transport attachment for transport vehicles 300: Container lid 301: Container 302: Semiconductor wafer 303: Workpiece holder for semiconductor wafers 304: Sealing system between container and lid 305: A drive unit capable of rotating a semiconductor wafer contained in a container under liquid

Claims

1. A transport container (301) for transporting a semiconductor wafer (302), produced by 3D printing from a substrate (105) into a defined shape; at least a region of an inner surface of the transport container (301) includes a coating material (108) for protecting the semiconductor wafer from chemicals capable of etching the semiconductor wafer; said coating material (108) being applied by a low temperature coating process, more particularly a low temperature sintering process, at a temperature below 150°C; the coating material (108) is comprised of polytetrafluoroethylene, perfluoroalkoxy polymer or polyvinylidene fluoride; The defined shape of the transport vessel comprises at its base a device suitable for removing the liquid medium; the defined shape of the transport container comprises one or more integrated workpiece holders (303) for the semiconductor wafers (302) and / or carriers for the semiconductor wafers (302) so that the semiconductor wafers (302) to be transported can be loaded in an upright position, A transport container (301) in an automatic transport system, wherein a designated transport direction of the transport container (301) is parallel to a front side or a back side of the semiconductor wafer.

2. A transport container (301) as described in claim 1, wherein the device suitable for removing the liquid medium is configured to be automatically opened by accumulation in the transport container (301).

3. 3. The transport container (301) of claim 1 or 2, comprising an active energy store for electrical energy.

4. A transport container (301) according to any one of claims 1 to 3, comprising a system for electronic data processing.

5. The transport container (301) according to any one of claims 1 to 4, comprising one or more fastening devices capable of fastening the container to both a floor-targeted transport system and a ceiling-targeted transport system.

6. The transport container (301) according to any one of claims 1 to 5, comprising one or more cover devices (300) for preventing liquid leakage during transport operations.

7. The transport container (301) according to any one of claims 1 to 6, wherein the weight of the transport container (301) filled with liquid and semiconductor wafers (302) is more than 15 kg and less than 120 kg.

8. A process for transporting semiconductor wafers comprising using a transport container according to any one of claims 1 to 7.

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