Patent Application
20170294327
The present disclosure relates generally to wafer containers and to techniques for molding wafer containers and other substrate containers.
The semiconductor industry introduces unique and unconventional purity and anti-contamination requirements into the development and implementation of product designs and manufacturing processes. Material selection is essential in the manufacturing, storage, and transportation of components and assemblies.
The processing of wafer disks into integrated circuit chips often involves several steps where the disks are repeatedly processed, stored and transported in wafer carriers including wafer containers. Due to the delicate nature of the disks and their extreme value, it is vital that they are properly protected throughout this procedure. One purpose of a wafer carrier is to provide this protection. Additionally, since the processing of wafer disks is generally automated, it is necessary for disks to be precisely positioned relative to the processing equipment for the robotic removal and insertion of the wafers. A second purpose of a wafer carrier is to securely hold the wafer disks during transport.
Wafer carriers are generally configured to axially arrange the wafers or disks in shelves or slots, and to support the wafers or disks by or near their peripheral edges. The wafers or disks are conventionally removable from the carriers in a radial direction upwardly or horizontally. Carriers may have supplemental top covers, bottom covers, or enclosures to enclose the wafers or disks. Although certain known wafer shippers may have only two parts, a base and a lid, front opening wafer containers for large wafers, 300 mm and 450 mm, may be quite complex with latch systems, separate shelves and externally mounted handling and machine interface components, ballast systems, sensors, and even environmental controls. And, of course, large wafers are much more expensive than smaller wafers requiring enhanced quality control and protection from damage.
Carriers and containers for substrate carriers, including wafer containers, are typically formed of injection molded plastics such as polycarbonate (PC), polyethylene (PE), perfluoroalkoxy (PFA), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), polypropylene (PP) and others. There are a number of material characteristics which are useful and advantageous for wafer carriers depending on the type of carrier and the particular part or component of the carrier at issue. Such characteristics include the cost of the material and the ease or difficulty in molding the material. Various issues associated with semiconductor manufacturing as they related to material characteristics are discussed below. Often a certain polymer will be used for one component and another polymer for a different component. Or a component may be made of two or more polymers.
During processing of semiconductor wafers or magnetic disks, the presence or generation of particulates presents very significant contamination problems. Contamination is accepted as the single largest cause of yield loss in the semiconductor industry. As the size of integrated circuitry has continued to be reduced, the size of particles which can contaminate an integrated circuit has also become smaller, making minimization of contaminants all the more critical. Contaminants in the form of particles may be generated by abrasion such as the rubbing or scraping of the carrier with the wafers or disks, with the carrier covers or enclosures, with storage racks, with other carriers, or with the processing equipment. A most desirable characteristic of a carrier is therefore a resistance to particle generation upon abrasion, rubbing, or scraping of the plastic molded material. See U.S. Pat. No. 5,780,127, owned by a corporate predecessor of the owner of the instant application. The patent discusses various characteristics of plastics which are pertinent to the suitability of such materials for wafer carriers. Said patent is incorporated herein by reference for all purposes.
Carrier materials should also have minimal outgassing of volatile components as these may leave films which also constitute a contaminant which can damage wafers and disks. Polymer materials that release contaminants are known as “dirty” materials and usage within enclosed wafer containment environments causes contamination issues. One such material is polybutylene terephthalate (PBT) and thus usage of such has been limited in wafer carriers, particularly wafer containers.
Also, carrier materials must have adequate dimensional stability, that is, rigidity, when the carrier is loaded. Dimensional stability is necessary to prevent damage to the wafers or disks and to minimize movement of the wafers or disks within the carrier. The tolerances of the slots holding wafers and disks are typically quite small and any deformation of the carrier can directly damage the highly brittle wafers or increase the abrasion and thus the particle generation when the wafers or disks are moved into, out of, or within the carrier. Dimensional stability is also extremely important when the carrier is loaded in some direction such as when the carriers are stacked during shipment or when the carriers integrate with processing equipment. The carrier material should also maintain its integrity under elevated temperatures which may be encountered during storage or cleaning.
Visibility of wafers within closed containers is considered desirable in many cases and may be required by end users. Transparent plastics suitable for such containers, such as polycarbonates, are desirable in that such plastic is low in cost but such plastics may not have sufficient performance characteristics such as abrasion resistance, heat resistance, chemical resistance, outgassing containment, rigidity characteristics, creep reduction, fluid absorption containment, UV protection, and the like.
One major benefit of particular specialized polymers, such as PEEK, is their abrasion-resistant qualities. Typical inexpensive conventional plastics release tiny particles into the air when abraded or even when rubbed against other material or objects. While these particles are typically invisible to the naked eye, they result in the introduction of potentially damaging contaminants that may adhere to semiconductor components being processed, and into the necessarily controlled environments. Such specialized thermoplastic polymers are dramatically more expensive than conventional polymers.
As a result, overmolding has been adopted by manufacturers of substrate containers, specifically wafer containers, where two distinct portions, each injection molded and each formed of different polymers are made intergral during the overmolding such that there is a gapless, crackless, hermetic juncture between the two different polymers. See U.S. Pat. Nos., 6,428,729; 6,428,729; and 7,168,564 which are owned by the owner of the instant application. These patents are incorporated herein by reference for all purposes. In certain circumstances it has been found that stresses may be associated with the overmolded component, especially where there are significant expanses of the polymers, such as in container portions. These stresses make fracturing under shock situations more common. It would be helpful to have a solution to the fracturing issue.
Moreover, it is expensive to manufacture the different mold components for overmolding when both (or more) portions are injection molded. Additionally, see U.S. Pat. Publications US20050236110, and US20050056601 in which thin film molding was disclosed in an overmold application. These publications are incorporated by reference herein for all purposes. The thin films have some minimal rigidity such that inserting them in three dimensional complicated structure is problematic. The techniques disclosed in said publications have not been commercially adopted for various reasons, presumably due to their difficulty in actual use and including the difficulty of repeatedly molding a consistent product using thin films.
As mentioned above, it is critical for wafers to be properly positioned in wafer carriers so that they are properly grasped and not damaged by robotic handling equipment. It has been found that during the door removal of 300 mm wafer containers, such as FOSBS(“Front Opening Shipping Boxes”), wafers drop inconsistently from a between-shelf seating position to an on-shelf seating position. In other words, the wafers are not uniformly positioned on the shelves. A solution to this problem would be welcome.
Overcoming the disadvantages of overmolding thin films and finding advantageous applications for thin film molding would be welcomed by the industry.
Embodiments of the present disclosure relates generally to a system and method for including a thin protective containment thermopolymer film in the molding process for handlers, transporters, carriers, trays and like devices utilized in the semiconductor processing industry. The thermoplastic film of suitable size and shape may be vacuum formed into a preform that approximates the final shape of the component portion desired. The shaped preform is then put in the component mold, and overmolded with the primary injection molded polymer. In embodiments, pins, or other structure may secure the thin film in position so that the polymer being injected does not displace or move the pre-shaped thin film. Suitable texturing may be provided with the thin film before insertion in the component mold or the mold may have surface treatment to modify the thin film surface texture in the final molded component.
In embodiments, a thin strip of PBT is pre-shaped by heating the strip with a suitable form to shape the wafer engagement ramp surfaces at the back side of a wafer container. The preformed strip, the “preform”, is then put in a mold that includes wafer shelves and the ramp surfaces and conventional polycarbonate is injection molded over the preformed strip. In embodiments, the PBT thin film may be 0.254 mm thick or within a range of plus or minus 25% of the 0.254 mm. The PBT allows the wafers to easily slide down from the seated position in the valley of V-shaped recess to seat on shelves as is conventional in front opening shipping boxes (FOSBs).
In other embodiments the PBT film may be about 0.254 mm. In other embodiments the PBT thin film may be 0.254 mm±0.050 mm. In other embodiments the PBT thin film may be 0.100 to 0.400 mm thick. In other embodiments the PBT thin film may be less than 0.300mm. In other embodiments the PBT thin film may be, less than 0.500 mm. In other embodiments the PBT thin film may be less than 1 mm. The above ranges also may be applicable for other thin films such as PEEK, PTFE, PFA, PC, amongst others. Such films may be formed of combinations of polymers and have additives.
A feature and advantage of some embodiments is that a conventional mold originally used for non-overmolding applications, can be used for overmolding applications without a new mold being constructed for the first portion of the overmold. Rather a less precise form, such as a form for vacuum form molding of thin components may be utilized for forming the preform. Such forms are significantly less expensive than injection molds.
In embodiments, pins or claws or other structure may retain the preformed film in place before and during the injection molding of the polymer over same.
In embodiments, an original mold may be sufficiently heated to preform the thin film before the primary molding operation; “primary” in the sense of greater quantities such as when the polycarbonate is injected for the base.
In embodiments, the component mold may have gates for injecting the molten polymer in the cavity directly opposite the seated position of the thin film portion for providing improved retention of the thin film in the mold. Where the desired location of the thin film for functionality is displaced from injection gates, the thin film insert portion may be enlarged to position a portion of the thin film opposite the gate for better securement of the thin film.
In embodiments, a mold may have a gate placed opposite where the thin film will be placed and have supplemental pins, hooks, or other hold-down features.
In embodiments, the thin film may be pre-formed for wafer engagement surfaces, reticle engagement surfaces, machine interface engagement surfaces, other contact surfaces. In embodiments a thin film may be preshaped, to define a containment surface, thereby providing a barrier to prevent outgassing or diffusion of moisture out of the primary containment material, which may be for example PC.
A feature and advantage of particular embodiments is that they provide a cost-efficient method of selectively utilizing desirable polymers, and the polymers' corresponding functional characteristic, wherein it is not necessary to utilize more of the polymer than is required.
Another advantage and feature of particular embodiments is that a functional thermoplastic film can be selectively bonded to a portion of a wafer carrier, chip tray, or other semiconductor component handler or transporter that contacts sensitive parts, components, or processing equipment.
A further advantage and feature of particular embodiments is the selective use of preferred low friction and/or abrasion-resistant polymer films on parts being used in the semiconductor processing industry for engagement of functional portions of substrate contacting surfaces.
Still another advantage and feature of particular embodiments is forming a semiconductor component handling device with a polymer filmed surface area that is transparent or translucent while still providing functional performance advancements for the selected surface. Such a handling device is formed by utilizing a thin enough layer of a material on a selected target structure of the device, preforming the layer, and overmolding the structure, to the substantially transparent or translucent device body constructed of a material such as PC.
A feature and advantage of embodiments is utilization of a preformed thin film intermediate injection molded overmolded portions. In such applications, the thin film may be preformed to be applied to the first injection molded portion and the second injection molded portion is molded thereon.
A feature and advantage of embodiments is a front opening wafer container that has a between-shelf seating position for wafers defined by forward and rearward V-shaped wafer edge receiving portions and an on-shelf seating position and that utilizes a material in the rearward V-shaped wafer edge receiving portion that has a coefficient of friction with respect to the wafers that is less than the material utilized for the forward V-shaped wafer edge receiving portions. Whereby when the door is removed from the front opening wafer container, the wafers drop from the between-shelf seating position to the on-shelf seating position more uniformly and have less of a tendency to not seat properly. In such embodiments, the material of the rearward V-shaped wafer edge receiving portion may be PBT and the material of the forward V-shaped wafer edge receiving portions may be polycarbonate or other material that presents a frictional resistance to wafers sliding on the ramps of the V-shaped wafer edge receiving portions.
A feature and advantage to embodiments ‘herein is that upon opening the doors to 300 mm wafer containers incorporating the disclosure, the wafers drop and seat more uniformly upon the wafer shelves compared to prior art wafer containers. A feature and advantage of embodiments of the disclosure is utilizing PBT for wafer seating portions without exposing the wafers to unacceptable levels of contaminants from the PBT.
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In embodiments, the PBT thin film may be 0.254 mm thick or within a range of plus or minus 25%. In other embodiments, the PBT thin film may be 254 mm±0.050 mm thick. In other embodiments the PBT thin film may be 0.100 to 0.400 mm thick. In other embodiments the PBT thin film may be less than 0.300 mm. In other embodiments the PBT thin film may be less than 0.500 mm. In other embodiments the PBT thin film may be less than 1 mm. The above ranges also may be applicable for other thin films such as PEEK, PTFE, PFA, PC, amongst others. Such films may be formed of combinations of polymers and have additives.
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Suitable texturing may be provided with the thin film before insertion in the component mold or the mold may have surface treatment to modify the thin film surface texture in the final molded component.
The preform 92 may have retention portions 93, such as tabs, that are displaced from the functional portion 98 of the preform, that is displaced from the ramps and V-shaped engagement portions. The retention portions may be gripped or clamped in the mold 94, see
In addition to insert molding a single film, a plurality of films can be laminated to form a composite film structure for moldable bonding to the semiconductor component handling devices. For instance, various film layers can include differing performance or containment characteristics listed herein, or to provide a combination thereof. A myriad of film lamination techniques known to one skilled in the film lamination art are envisioned for use with embodiments of the disclosure. For instance, U.S. Pat. Nos. 3,660,200, 4,605,591, 5,194,327, 5,344,703, and 5,811,197 disclose thermoplastic lamination techniques and are incorporated herein by reference in their entireties for all purposes.
Referring to
The above references in all sections of this application are herein incorporated by references in their entirety for all purposes.
All of the features disclosed in this specification (including the references incorporated by reference, including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including references incorporated by reference, any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The disclosure is not restricted to the details of the foregoing embodiment (s). The disclosure extends to any novel one, or any novel combination, of the features disclosed in this specification (including any incorporated by reference references, any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed The above references in all sections of this application are herein incorporated by references in their entirety for all purposes.
Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose could be substituted for the specific examples shown. This application is intended to cover adaptations or variations of the present subject matter. Therefore, it is intended that the disclosure be defined by the attached claims and their legal equivalents, as well as the following illustrative aspects. The above described aspects embodiments of the disclosure are merely descriptive of its principles and are not to be considered limiting. Further modifications of the disclosure herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the disclosure.
This application claims priority to U.S. Provisional Application Nos. 62/043,297 filed Aug. 28, 2014, and 62/049,144 filed Sep. 11, 2014. Both applications are incorporated herein by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/047498 | 8/28/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62043297 | Aug 2014 | US | |
| 62049144 | Sep 2014 | US |
