Wafer Cassette

Abstract

A front opening wafer container including an enclosure portion and a door. A wafer support system is provided including a pair of spaced apart cantilever wafer shelves, each wafer shelf including a pair of opposing inclined ramp portions. The ramp portions are cooperatively positioned and configured so that when the wafer is received on the shelves, the wafer is supported on the ramps at a lower peripheral corner of the wafer, all other portions of the wafer being free from contact with the wafer support system. Each wafer shelf may have a generally concave upper surface and the incline of the ramps is continuous with the concave upper surfaces of the wafer shelves.

Description

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 60/819,208 entitled WAFER CASSETTE and filed Jul. 7, 2006, said application being hereby fully incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to wafer containers and, in particular, to systems for supporting wafers in wafer containers.

BACKGROUND OF THE INVENTION

[0003] Semiconductor and magnetic components used in electronic devices are typically manufactured from "wafers," meaning silicon wafers, magnetic substrates or the like. In the processing of these wafers into finished devices, numerous steps must be performed and the wafers must often be transported facility to facility and internally within a facility. The wafers are generally very sensitive to physical and electrical shock. Additionally, the wafers may be quite valuable, particularly after processing steps have been completed.

[0004] Specialized carriers have been developed for transporting and storing batches of wafers before, during, and after processing in order to provide protection. Two types of specialized wafer containers in common usage are known as FOUPs (front opening unified pod) and FOSBs (front opening shipping boxes). These containers have a container portion with interior wafer supports for holding a stack of wafers in a horizontal axially spaced arrangement in the interior of the container. The container has a front door that allows insertion and removal of the wafers and a door sealingly engages onto the wafer container and may be latched in place. Such boxes are, for example, disclosed in U.S. Pat. Nos. 6,216,874; 6,206,196; 6,010,008; 5,944,194, all of which are owned by the owner of this application and are hereby fully incorporated herein by reference.

[0005] A generic prior art front opening carrier is depicted in FIG. 1. The wafer container is shown seated on automatic processing equipment 25, and generally includes enclosure portion 20 and door 22. Enclosure portion 20 has open front 24, top 23, a pair of sides 28, 29, back side 32, and bottom 34. Door frame 36 defines open front 24 and is configured for receiving door 22. Enclosure portion 20 may have robotic handling flange 42. Wafer supports 46 in the interior of enclosure portion 20 support wafers (not shown) that are aligned in a horizontal orientation in a stacked space array. Door 22 has outwardly facing side 50, inwardly facing side 52 and periphery 54. Periphery 54 has latch slots 58 on the outwardly facing side. Exterior panel 62, which may be the principal structural panel of the door, covers latch mechanisms (not shown) associated with keyholes 68 and that have latch members (not shown), which extend out of the latch slots 58.

[0006] During transport, wafers may shift in response to physical shocks to the container. The shifting of the wafers upon the wafer supports may cause particles to be abraded from the wafer or the supports upon which the wafer rests. Such particles, even if they are very tiny, may cause defects to occur in photolithography and other processing steps. Accordingly, formation of particles is desirably avoided.

[0007] Some prior attempts at alleviating particulate formation have focused on the plastic materials used in the container. For instance, U.S. Pat. Nos. 5,780,127 and 6,808,668 disclose various polymer materials and methods to be used in making wafer supports with reduced potential for particulate formation. Said patents are hereby fully incorporated herein by reference.

[0008] Other attempts at reducing particulate formation in wafer containers have been directed at the physical configuration of the wafer supports and cushioning. For instance, U.S. Pat. Nos. 6,267,245 and 6,644,477 disclose such support and cushioning systems, and are hereby fully incorporated herein by reference.

[0009] These prior attempts, however, have not been fully successful at eliminating particulate formation within wafer containers. Accordingly, what is needed in the industry is a wafer container having features for further limiting particulate formation.

[0010] Another trend in the industry has been toward ever larger diameter and thinner wafers. While 150, 200, and 300 mm semiconductor wafers have been generally standard in the industry, larger wafer diameters such as 450 mm and larger are now contemplated and used. A drawback of the larger wafer sizes, however, is gravitational deflection or sag occurring in the wafer when supported on shelves at the outer periphery of the wafer as in prior wafer containers. This wafer sag may reduce clearance between wafers at the centers of the wafers and make it difficult to access the wafers for insertion and removal from the container with standard robotic tools inserted between wafers proximate the center. Accordingly, what is further needed in the industry is a wafer container that accommodates larger diameter wafers while reducing gravitational sag.

SUMMARY OF THE INVENTION

[0011] The present invention substantially meets the aforementioned need of the industry by providing containers, wafer support systems, and methods that further limit particulate contamination within wafer containers and reduce gravitational sag of larger diameter wafers.

[0012] Embodiments of the invention further provide wafer support surfaces having sloped wafer support regions providing supporting zones of contact only at the lower peripheral corner of the wafer, reducing contact between the supported wafer and wafer support and thereby minimizing damage and contamination to the wafer.

[0013] The wafer supports may be formed separately or integrally with the wafer container. If formed separately, the wafer supports may be snapped into pre-formed structure in the wafer container and/or may be secured therein by connectors. If formed separately from the container, the wafer supports of this invention may be formed integrally by such processes as injection molding or components thereof may be formed separately. If formed separately, the components are assembled and may be secured in assembled form by connectors. If formed integrally with the container, the wafer supports may be formed by such known processes as overmolding.

[0014] According to an embodiment a wafer container includes an enclosure portion with a top, a bottom, opposing sides, a back and an open front defined by a door frame. A door is selectively receivable in the door frame to sealingly close the open front. A wafer support system is provided in the enclosure for receiving and supporting at least one wafer, the wafer support system including a pair of spaced apart cantilever wafer shelves, each wafer shelf including a pair of opposing inclined ramp portions. The ramp portions are cooperatively positioned and configured so that when the wafer is received on the shelves, the wafer is supported on the ramps at a lower peripheral corner of the wafer, all other portions of the wafer being free from contact with the wafer support system. The ramps may inclined at between one degree and nine degrees, between three degree and seven degrees, or about five degrees with respect to the horizontal. Each wafer shelf may have a generally concave upper surface, and in some embodiments, the incline of the ramps is continuous with the concave upper surfaces of the wafer shelves.

[0015] In embodiments of the invention, the wafer support system includes a pair of wafer support structures, wherein each wafer support structure includes a column with one of the pair of wafer shelves extending therefrom. The wafer support structures may be secured in the enclosure portion with a plurality of fasteners, or may be integrally molded with the enclosure portion using an overmolding process. The column and wafer shelves may be integrally formed in one piece or may be molded as separate pieces and later assembled.

[0016] In an embodiment, a wafer container for supporting a plurality of wafers in a horizontally oriented, spaced apart, axially aligned arrangement includes an enclosure portion having a top, a bottom, opposing sides, a back and an open front defined by a door frame. A door is selectively receivable in the door frame to sealingly close the open front. A wafer support system is provided in the enclosure for receiving and supporting the wafers, the wafer support system including a pair of spaced apart opposing wafer support structures, each wafer support structure including a column with a plurality of spaced apart cantilever wafer shelves extending therefrom. Each of the wafer shelves of a first one of the wafer support structures is horizontally registered with one of the wafer shelves of the other wafer support structure to define a plurality of horizontally oriented slots, each for receiving one of the plurality of wafers. Each wafer shelf includes a pair of opposing inclined ramp portions for contacting the wafer, the ramp portions cooperatively positioned and configured so that when the wafer is received in the slot, the wafer is supported on the ramps at a lower peripheral corner of the wafer, all other portions of the wafer being free from contact with the wafer support system.

[0017] According to an embodiment, a wafer container includes an enclosure portion having a top, a bottom, opposing sides, a back and an open front defined by a door frame. A door is selectively receivable in the door frame to sealingly close the open front. The container further includes means for supporting at least one wafer in the enclosure, wherein the means supports the wafer at a plurality of spaced apart locations along lower peripheral corner of the wafer, all other portions of the wafer being free from contact with the container.

[0018] These and other objects, features, and advantages of this invention will become apparent from the description which follows, when considered in view of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a perspective view of a prior art wafer container positioned on processing equipment;

[0020] FIG. 2 is a perspective view of a wafer container according to an embodiment of the present invention;

[0021] FIG. 3 is a front elevation view of a wafer container according to an embodiment of the present invention;

[0022] FIG. 3a is a sectional side view of the wafer container and wafer support system of FIG. 3 taken at section 3A-3A of FIG. 3;

[0023] FIG. 4 is a perspective view of a wafer support member according to an embodiment of the invention;

[0024] FIG. 5 is a perspective view of another embodiment of the wafer container of the invention formed by overmolding;

[0025] FIG. 6 is a perspective view of another embodiment of the wafer container of the invention wherein the wafer support members are assembled from separately formed parts;

[0026] FIG. 7 is a perspective view of the wafer supports of the embodiment of FIG. 6;

[0027] FIG. 8 is a fragmentary perspective view of a portion of the wafer supports of FIG. 7;

[0028] FIG. 9 is a fragmentary perspective view of a wafer support ramp according to an embodiment of the present invention;

[0029] FIG. 10 is a cross-sectional view of the wafer support ramp of FIG. 9 taken at section 10-10 of FIG. 9; and

[0030] FIG. 11 is a fragmentary cross-sectional view of a wafer support ramp according to an embodiment of the invention, wherein the ramp is continuous with a concave upper surface of the wafer support member.

[0031] While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

[0032] A person of ordinary skill in the art will readily appreciate that individual components shown on various embodiments of the present invention are interchangeable and may be added or interchanged on other embodiments without departing from the spirit and scope of this invention. General details of semiconductor wafer containers and various components applicable to the present invention are described in U.S. Pat. Nos. 6,951,284; 6,955,382; 6,880,718; 6,811,029; 6,758,339; 6,736,268; RE 38,221; and 6,464,081, all owned by the owner of the present invention, and all hereby fully incorporated herein by reference.

[0033] Wafer container 70 according to embodiments of the present invention is depicted in FIGS. 2-10. Wafer container 70 generally includes enclosure 72 and door 74. Enclosure 72 generally includes unitary shell 76 having top wall 78, opposing bottom wall 80, side walls 82, 84, back wall 86 and open front 88, which is defined by door frame 90. Kinematic coupling 92 may be received on bottom wall 80 for positioning container 70 on processing equipment (not shown), while robotic handling flange 94 may be received on top wall 78 to enable automated handling of container 70.

[0034] Door 74 is receivable in door frame 90 to sealingly close container 70, and generally includes outer wall 96 and inner wall 98 defining an enclosed space for latch mechanisms (not shown) for latching door 74 in place. The latch mechanisms are operable through keyholes 100 defined in outer wall 96.

[0035] Wafer support system 102 is provided in enclosure 72 for receiving a plurality of wafers 104 in a horizontal, spaced apart, axially aligned arrangement. Wafer support system 102 generally includes a pair of wafer supports 106 positioned proximate, but spaced apart from, each of side walls 82, 84. In an embodiment depicted in FIGS. 3, 3a, 4, 9, and 10 wafer support 106 generally includes rear column 108 having integral attachment beams 110, 112, with cantilever shelves 114 spaced apart therebetween. Each cantilever shelf 114 and lower attachment beam 112 defines a pair of opposing wafer support ramps 116, 118. Moreover, as depicted in FIG. 3a, upper surface 120 of cantilever shelves 114 and lower attachment beam 112 is slightly concave, sloping upwardly in each direction from low point 122 toward ramps 116, 118. As depicted in FIG. 3, the cantilever shelves 114 of the pair of wafer supports 106 are horizontally registered so as to define a plurality of horizontal slots 123, each for receiving a wafer 104. It will be appreciated that enclosure 72 and wafer supports 106 may be configured to provide any desired number of slots 123, from one up to thirty or more.

[0036] In the embodiments depicted, ramps 116, 118, are inclined at about five degrees from horizontal. Other angles of incline for ramps 116, 118, however, may be suitable for other embodiments and are within the scope of the present invention. For instance, in some embodiments, ramps 116, 118, may be inclined at between about three degrees and seven degrees from the horizontal, and in others between about one degree and nine degrees from the horizontal.

[0037] Attachment beams 110, 112, may include bosses 126, 128, 130, for securing wafer support 106 in enclosure 72. In an embodiment, each boss 126, 128, 130, defines a bore 132 that receives a fastener (not depicted) extending through shell 76. To provide electrical conductivity for static dissipation from the wafers 104, the fasteners may be electrically conductive and may extend into or through kinematic coupling 92 from bosses 128, 130. As known to those of skill in the art, kinematic coupling 92 may be partially or wholly made from electrically conductive or static dissipative material so as to provide an electrical path to ground.

[0038] According to embodiments of the invention, lower peripheral corner 124 of wafer 104 rests on ramps 116, 118, as depicted in FIGS. 9 and 10, such that each wafer 104 is supported only at four minimal zones 138 of contact, essentially a line defined by lower peripheral corner 124 of wafer 104. This mode of support minimizes contact between wafers 104 being stored in container 70 and the wafer support system 102. Minimizing contact eliminates or greatly minimizes wafer damage and particulate contamination that would otherwise occur due to more extensive contact.

[0039] As can also be seen in FIG. 3a, concavity of upper surface 120 of cantilever shelves 114 and lower attachment beam 112 for a gap or clearance 126 between wafer 104 and upper surface 120, except for the two zones of contact 138. Clearance 126 enables a slight amount of gravitationally induced sag to occur in wafer 104 without contact between wafer 104 and upper surface 120. It will of course be appreciated that in other embodiments of the invention, the degree of concavity in upper surface 120 may be increased so that ramps 116, 118, are defined by the concavity in upper surface 120. As depicted in FIG. 11, the slope of upper surface 120 may be continuous so as to incorporate the ramps while still enabling line contact between wafer 104 and cantilever shelves 114 and lower attachment beam 112 at lower peripheral corner 124.

[0040] The wafer support 106 may be formed by several methods known to persons of skill in the art. For instance, wafer support may be formed from polymer material by injection molding, overmolding, or the like. Suitable materials are any materials with suitable abrasion resistance and chemical properties. In particular, PEEK or PEI polymers may be used, and may be combined with other materials such as carbon fiber to enable electrically conductive or static dissipative properties in wafer support 106.

[0041] In another embodiment of the invention, wafer support members 106 may be integrally formed with enclosure 72 by overmolding as depicted in FIG. 5. In such embodiments, electrical conductivity for grounding of wafer supports 106 through kinematic coupling 92 may be accomplished by a portion of wafer support 106 extending through bottom wall 80 of enclosure 72 or through conductive fasteners as disclosed above.

[0042] In a further embodiment of the invention, wafer support 106 may be formed in separate parts as depicted in FIGS. 6-8. In such embodiments, wafer support 106 generally includes column 140 defining spaced apart notches 142 and separate cantilever shelves 144. Each cantilever shelf 144 defines a tab structure 146 that is received in one of notches 142 to attach the cantilever shelf 144 to the column 140. Each column 140 in turn defines bores 148 at the top and bottom thereof to receive fasteners 150 to secure wafer support 106 in enclosure 72. Alternatively, columns 140 may be secured in enclosure 72 by any other suitable means such as by overmolding, adhesives, or the like. As previously described, cantilever shelves 144 may have a slightly concave upper surface 152, and may define ramps 116, 118, to enable line contact with wafer 104. For purposes of material reduction and lightness, shelves 144 may be molded with recesses 153 or cores 153a as depicted in FIG. 8.

[0043] Advantageously, wafer supports 106 are positioned inwardly from sides 82, 84, such that a portion 154 of wafer 104 extends outward beyond outer margin 156 of wafer support 106. This enables a greater distance between zones of contact 138, thereby reducing the amount of gravitational sag in wafer 104. Moreover, the space between outer margins 156 and sides 82, 84, enables a robotic pickup tool to be inserted in this space to insert and remove wafer 104 from enclosure 72 by lifting portion 154.

[0044] The embodiments above are intended to be illustrative and not limiting. Additional embodiments are encompassed within the scope of the claims. Although the present invention has been described with reference to particular embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For purposes of interpreting the claims for the present invention, it is expressly intended that the provisions of Section 112, sixth paragraph of 35 U.S.C. are not to be invoked unless the specific terms "means for" or "step for" are recited in a claim.

Claims

1. A wafer container comprising: a plurality of wafers; an enclosure portion including a top, a bottom, opposing sides, a back and an open front defined by a door frame; a door selectively receivable in the door frame to sealingly close the open front; and a wafer support system in the enclosure for receiving and supporting the wafer, the wafer support system including a pair of spaced apart cantilever wafer shelves, each wafer shelf including a pair of separated and opposing arcuate inclined ramp portions, one of the pair facing radially inwardly and forwardly, the other of the pair facing radially inwardly and rearwardly, the ramp portions cooperatively positioned and configured so that when the wafer is received on the shelves, the wafer is supported on the ramps at a lower peripheral corner of the wafer and partially down said ramps, all other portions of the wafer being free from contact with the wafer support system.

2. The wafer container of claim 1, wherein the ramps are inclined at between one degree and nine degrees with respect to the horizontal.

3. The wafer container of claim 1, wherein the ramps are inclined at between three degree and seven degrees with respect to the horizontal.

4. The wafer container of claim 1, wherein the ramps are inclined at about five degrees with respect to the horizontal.

5. The wafer container of claim 1, wherein each wafer shelf has a generally concave upper surface.

6. The wafer container of claim 5, wherein the plurality of wafers each have a pair of lateral edge portions, each intermediate one of the pairs of opposing arcuate inclined ramp portions, said lateral edge portions not being supported by or in vertical alignment with the respective opposing arcuate inclined ramp portions.

7. The wafer container of claim 1, wherein the wafer support system comprises a pair of wafer support structures, and wherein each wafer support structure includes a column with one of the pair of wafer shelves extending therefrom.

8. The wafer container of claim 7, wherein each of the wafer support structures is secured in the enclosure portion with a plurality of fasteners.

9. The wafer container of claim 7, wherein the wafer support structures are integrally molded with the enclosure portion using an overmolding process.

10. The wafer container of claim 7, wherein the column and wafer shelves are integrally formed in one piece.

11. A wafer comprising: a plurality of wafers; an enclosure portion including a top, a bottom, opposing sides, a back and an open front defined by a door frame; a door selectively receivable in the door frame to sealingly close the open front; and a wafer support system in the enclosure for receiving and supporting the plurality of wafers in a horizontally oriented, spaced apart, axially aligned arrangement, the wafer support system including a pair of spaced apart opposing wafer support structures positioned and attached to the enclosure portion at the back of the enclosure portion, each wafer support structure including a column with a plurality of spaced apart cantilever wafer shelves extending therefrom toward the open front, each of the wafer shelves of a first one of the wafer support structures horizontally registered with one of the wafer shelves of the other wafer support structure to define a plurality of horizontally oriented slots, each for receiving one of the plurality of wafers, each wafer shelf including a pair of opposing and separated inclined ramp portions for contacting the wafer, the ramp portions cooperatively positioned and configured so that when the wafer is received in the slot, the wafer is supported on the ramps at a lower peripheral corner of the wafer, all other portions of the wafer being free from contact with the wafer support system.

12. The wafer container of claim 11, wherein the ramps are inclined at between one degree and nine degrees with respect to the horizontal.

13. The wafer container of claim 11, wherein the ramps are inclined at between three degree and seven degrees with respect to the horizontal.

14. The wafer container of claim 11, wherein the ramps are inclined at about five degrees with respect to the horizontal.

15. The wafer container of claim 11, wherein each wafer shelf has a generally concave upper surface.

16. The wafer container of claim 15, wherein the incline of the ramps is continuous with the concave upper surfaces of the wafer shelves.

17. A wafer container comprising: at least one wafer; an enclosure portion including a top, a bottom, opposing sides, a back and an open front defined by a door frame; a door selectively receivable in the door frame to sealingly close the open front; and means for supporting the wafer in the enclosure, said means attached at the back of the enclosure portion and cantilevered toward the open front, said means supporting the wafer at a plurality of spaced apart locations along lower peripheral corner of the wafer, all other portions of the wafer being free from contact with the container.

18. The wafer container of claim 17, wherein said means for supporting the wafer in the enclosure includes a plurality of wafer support structures spaced inwardly from the most lateral points of the wafer.

19. The wafer container of claim 18, wherein each wafer support structure includes a column with a plurality of spaced apart cantilever wafer shelves extending therefrom, each wafer shelf including a pair of opposing inclined ramp portions for contacting the wafer.

20. The wafer container of claim 19, wherein the ramps are inclined at about five degrees with respect to the horizontal.