GB2290414A

GB2290414A - Wafer basket

Info

Publication number: GB2290414A
Application number: GB9512022A
Authority: GB
Inventors: Masato Hosoi
Original assignee: Shin Etsu Polymer Co Ltd; Shin Etsu Chemical Co Ltd; Shin Etsu Handotai Co Ltd
Current assignee: Shin Etsu Polymer Co Ltd; Shin Etsu Chemical Co Ltd; Shin Etsu Handotai Co Ltd
Priority date: 1994-06-17
Filing date: 1995-06-14
Publication date: 1995-12-20
Anticipated expiration: 2015-06-14
Also published as: DE19521575A1; FR2725185A1; FR2725185B1; JP2791971B2; DE19521575C2; KR100332719B1; GB2290414B; JPH088332A; GB9512022D0; TW299485B; KR960002468A

Description

2290414 WAFER BASKET IN WAFER-HOLDER BOX

BACKGROUND TO THE INVENTION

The present invention relates to a waf er basket in a wafer-holder box for the storage or transportation of various kinds of disk-formed precision substrate plates such as semiconductor silicon wafers, photomask masters, photomasks and the like, with safety and reliability, in the manufacture of semiconductor devices.

As is well known, it is usual for various disk-formed precision substrate plates such as semiconductor silicon wafers, which are produced by slicing a single crystal silicon rod or boule, to be manufactured in a special plant for that purpose and transported in large quantities to other manufacturers for the fabrication of various semiconductor devices. Accordingly, one very important problem in this manufacturing process is to provide a safe and reliable means for the storage and transportation of such expensive wafer materials, because wafers are generally very thin and brittle and. are readily damaged mechanically and must be strictly protected from any trace of contamination in handling and during storage and transportation. To meet these requirements, various types of wafer-holder boxes, tightly sealable by mounting a covering, have been developed heretofore and are in use for holding a large number of waf ers to ensure safety in storage and transportation.

It is essential in such a waf er-holder box that the wafers contained therein are prevented from contact with the adjacently held wafers during transportation of the holder boxes on a rattling vehicle so that, as is disclosed in Japanese Utility Model Kokai 1-129836, the wafers are usually held with elastic resilience in an orderly aligned fashion keeping a definite space between them in a wafer basket provided with a number of grooves for insertion of the wafers, by which vibration of the wafers during transportation can be alleviated so that the wafers are prevented from damage and occurrence of dust particles can be prevented by virtue of the absence of rubbing contact between the wafers and the supporting surfaces of the wafer basket.

A typical example of the above-mentioned wafer basket in the prior art is illustrated in Figure 6 in a perspective view and is in the form of a framework consisting of a pair of oppositely facing side walls a, a, an end wall b connecting the side walls a,a, corner members f, f and a tie plate c, which def ines an end plane opposite to the end wall b by connecting the corner members f,f, to form a square or rectangular framework, while the tie plate c connecting the corner members f,f is provided on its outwardly facing surface with a rib or line protrusion d having a semicircular cross section for indexing or positioning purposes running in the longitudinal direction of the tie plate c. In mounting such a wafer basket on an automatic machine for transfer, inspection, processing and so on, it is usual that the waf er basket is put in position, as is illustrated in Figure 7 by a cross-sectional side view, to stand on the corner members f,f, which serve as the legs, with the end plane def ined by the tie plate c with a rib d facing downwardly so that the rib d is engaged with a groove on a machine stage S.

The wafer-insertion grooves or slits e provided on the inwardly facing surface of the side walls a,a each run in a direction parallel to the surface of the machine stage S.

While automatic machines on which the above-mentioned wafer basket is mounted are designed in such a fashion as to comply with the disposition of the wafers W in parallel with the surface of the machine stage S, such a completely parallel disposition of the wafers W is not always accomplished and the wafers W may be more or less inclined relative to the surface of the machine stage S, sometimes resulting in an erroneous movement of the machine. This problem is more serious with wafers having a larger diameter, for several reasons. The non-narallelism reason for the in the holding disposition of wafers W is due to the form of and play in the wafer-insertion grooves e.

Namely, as is illustrated by Figures 8a and 8b each illustrating a cross-section of a groove e having an outwardly opening tapered or r trapezoidal cross section to hold a wafer W, the wafer W is held in the groove e by contact between the peripheral ridge of the waf er W and the sloped wall of the outwardly opening groove e in the open-end portion of the groove e, as is shown in Figure 8a, while the waf er W reaches the bottom of the groove e at or in the vicinity of the bottom of the basket as is illustrated in Figure 8b. These situations mean that, as a consequence of the difference in the contacting position between a wafer W and the groove e, which is low in the open end of the grooves e (Figure 8a) and high at the bottom of the grooves e (Figure 8b), the wafer W is held in the groove e in an inclined disposition and not parallel with the surface of the machine stage S.

Alternatively, a groove e having an orthogonal cross-section, as is illustrated in Figure 8c, has been proposed, of which the surface of the groove e is substantially in parallel to the surface of the machine stage S so that the waf er W can be held in the groove substantially in parallel to the surface of the machine stage S. Such a design of the groove e with an orthogonal cross-section, however, has a problem that, due to the increased contacting area between the wafer W and the surf ace of the groove e, the wafer W is at greater risk of contamination by contact therewith or decreased smoothness of the surface leading to eventual degradation of the wafer quality.

Further alternatively, the wafer W can be held substantially in parallel to the machine stage S even with a wafer-insertion groove having a tapered or outwardly opening cross section as shown in Figures 8a and 8b when the wafer basket has no play of the groove e relative to the diameter of the wafer W so that the waf er W is held tightly in the groove e.

This approach of groove design is not practicable because of the decrease in the working efficiency in the insertion of the wafer W into or taking the wafer W out of the groove e due to the tightness of holding without play, not to mention the risk of increased mechanical damage on the wafers W.

SUMMARY OF THE INVENTION

The present invention accordingly has as an object to provide an improvement in a wafer basket having a plural number of wafer-insertion grooves each in parallel to the others in which wafers can be held one by one, when the wafer basket is mounted on a machine stage in a disposition parallel to the surface of the machine stage, still without adversely affecting the practicality of the insertion of wafers into and taking the wafers out of the grooves, so that any operational errors of the waferprocessing automatic machine, and any mechanical damage of the wafers, can be prevented by virtue of ease in handling thereof.

Thus, the present invention provides an improvement in a wafer basket to be contained in the box body of a wafer-holder box, which wafer basket is an integral body formed from a thermoplastic resin in the form of a generally rectangular framework consisting of a pair of oppositely facing side walls each being provided on the inwardly facing surface with a plurality of wafer-insertion grooves running in the up and down direction of the side walls to open in the upper end thereof, an end wall perpendicular to the side walls connecting the side walls to define a first end plane of the framework, two corner members provided substantially symmetrically each along the end line of one of the side walls opposite to the end wall to define a second end plane of the framework and a tie plate connecting the corner members and provided on the outwardly facing surface with a line protrusion or rib running in the direction to connect the side walls for positioning of the basket, the improvement comprising having each of the corner members f ormed in such a shape that the width of each of the corner members within the plane of the side wall is larger at or in the vicinity of the upper end than at or in the vicinity of the lower end.

Such a shape of the corner members can be accomplished when each of the corner members has a trapezoidal form having a larger width at or in the vicinity of the upper end thereof than at or in the vicinity of the lower end.

Alternatively, the same effect can be obtained when a rectangular corner member is provided with a protrusion at or in the vicinity of the upper end thereof, the protrusion being in rectangular, trapezoidal or semicircular form or in the form of a truncated cone or pyramid.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a perspective view of one embodiment of the wafer basket according to the invention.

Figure 2 is a vertical cross-sectional view of the wafer basket illustrated in Figure 1, holding wafers and mounted on a machine stage.

Figure 3 is a perspective view of an assembly comprising a wafer-holder box body, a wafer basket of the invention holding a number of wafers and a covering member, as disassembled is into parts.

Figure 4 is a perspective view of another embodiment of the wafer basket according to the invention.

Figure 5 is a vertical cross-sectional view of the wafer basket illustrated in Figure 4, holding wafers and mounted on a machine stage.

Figure 6 is a perspective view of a conventional wafer basket of the prior art.

Figure 7 is a vertical cross-sectional view of the conventional wafer basket illustrated in Figure 6, holding wafers and mounted on a machine stage.

Figures 8a, 8b and 8c are each an enlarged partial vertical crosssectional view showing the disposition of a wafer within a waferinsertion groove.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.

When a wafer basket of the invention holding a number of wafers each inserted into one of the wafer-insertion grooves is put into a wafer-holder box and a covering member is put thereon, each of the waf ers is held with security by means of the wafer damper held by a supporting frame interposed between the box body and the covering member.

In addition, each of the wafers is held independently from the others keeping a gap space therebetween defined by the pitch of the waferinsertion grooves from adjacent ones, so as to be prevented by the damping action from contact with the other wafers even under vibration during transportation, so that safety of transportation can be ensured without causing mechanical damage to the wafers. Further, occurrence of dust particles by the rubbing contact of the wafers with each - 11 other or with the surf ace of other parts of the box can be prevented so that the wafers as transported are free from the problem of contamination. Moreover, the handling of the wafers in putting into and taking out of the wafer basket is never disturbed in the wafer basket of the present invention, thereby greatly contributing to the improvement of the working efficiency.

In the following, the wafer basket of the invention is described in detail with reference to the accompanying drawing.

Figure 1 illustrates a perspective view an embodiment of the wafer basket, which is integral body prepared by moulding with a thermoplastic resin such as polyolefins, e.g. polyethylene, polypropylene and polybutadiene, polycarbonates, polybutylene terephthalates and the like, of which polypropylene is preferred.

The wafer basket is in the general form of a rectangular framework consisting of a pair of oppositely facing side walls 1,1, an end wall 2 connecting the wide walls 1,1 along one of the end lines thereof to define a first end plane of the framework, a pair of corner members 3,3 each of an along the other end line of the respective side walls 1, 1 to def ine the second end plane of the framework as an extension thereof and a tie plate 4 connecting the corner members 3,3. The side walls 1,1 are each provided on the inwardly facing surface with a plurality of grooves la each between two pleats lb in a symmetrical fashion running in the up and down direction on the two side walls 1,1. When a number of wafer materials are mounted on the wafer basket, each of the wafers is inserted into one of these wafer-insertion grooves la, la on the two side walls 1, 1 symmetrically so that each of the wafers is isolated with a definite distance defined by the pitch of the groove alignment from the adjacent wafers. The tie plate 4 is provided on the outwardly facing surface with a line protrusion or rib 4a having a semicircular cross - section to serve as an indexing or positioning guide when the wafer basket is mounted on a machine stage of an automatic waferprocessing machine with the tie plate 4 facing downwardly, as is being engaged with stage S.

illustrated in Figure 2, by the groove on the machine While the corner members f,f in the conventional wafer basket illustrated in Figure 6 as an extension of the respective side walls a,a each have a form of an orthogonally elongated strip to serve as standing legs when the wafer basket is mounted on a machine stage as is illustrated in Figure 7, the corner members 3,3 in the wafer basket according to the invention illustrated in Figure 1 are each in the form of an elongated trapezoid having a larger width at or in the vicinity of the upper end 3a, i.e. toward the open end of the grooves la for the insertion of wafers, than at or in the vicinity of the lower end 3b, i.e. toward the bottom of the wafer basket.

Figure 2 illustrates a cross-sectional side view of the waf er basket of Figure 1 mounted on the machine stage S and holding a number of wafers W each inserted into one of the paired wafer-insertion grooves la between the pleats lb on the side walls 1, 1. The wafer basket stands on the corner members 3,3 to serve as the legs on the machine stage S with the open end of the wafer-insertion grooves la directed in an approximately horizontal direction leftwardly on the f igure. In the conventional wafer basket illustrated in Figures 6 and 7, in which each of the corner members f,f has an orthogonally elongated form, the plane defined by the wafer- s insertion grooves e is in a disposition perfectly parallel to the surface of the machine stage S while the wafer W held in each groove e is necessarily inclined relative to the surface of the machine stage S as is explained by making reference to Figures 8a and 8b. In the wafer basket according to the invention illustrated in Figures 1 and 2, in contrast thereto, the corner members 3,3 serving as the standing legs each do not have a uniform width but have an elongated trapezoidal form so that the plane defined by each wafer-insertion groove la is in an inclined disposition relative to the surface of the machine S, higher toward the open end (left end of the figure) of the grooves la and lower toward the bottom of the waf er basket (right end of the figure). While the wafer W inserted into the grooves la is inclined relative to the plane defined by the grooves la, the inclination of the plane defined by the grooves e relative to the machine stage S and the inclination of the wafer W relative to the plane defined by the grooves e are compensatory with each other so that perfect parallelism of the wafer W to the surface of the machine stage S is ensured.

It is therefore important to adequately design the trapezoidal form of the corner members 3,3 to serve as the standing legs when the wafer basket is mounted on a machine stage S. Namely, the difference in the width of the corner member 3 between the end positions 3a and 3b should just compensate the inclination of the Wafer W relative to the plane defined by the waferinsertion groove la, which is usually in the range from 00151 to 1 0 001 depending on the size of the wafer materials so that the width difference is in the range from about 0.3 mm to 3 mm though dependent on the size of the wafer materials W Figure 3 of the accompanying drawing illustrate,5 a perspective view of a typical assembly of the wafer-holder box as disassembled into the box body A, the wafer basket C according to the invention holding a number of wafers W each inserted into the waferinsertion grooves, the covering member E which is put on the box body A with the frame-formed packing member B in between to ensure air- tightness of covering, while the wafers W are gently pressed against the waf er basket C by means of the damper member D between the wafer basket C and the covering member E so that the waf ers W are protected from vibrations or mechanical shocks during transportation on a rattling vehicle.

Figures 4 and 5 illustrate another embodiment of the waf er basket according to the invention. by a perspective view and by a cross sectional side view as mounted on a machine stage S with a plural number of wafers W each inserted into one of the wafer-insertion grooves.

The wafer basket of this embodiment is also an integral body consisting of two oppositely facing side walls 11,11 each in a pleated form with a number of pleats llb forming a wafer-insertion groove lla between two pleats llb, llb, an end wall 12 connecting the two side walls 11, 11 along the end line of each side wall 11,11, corner members 13,13 each as an extension of the side walls 11,11 and a tie plate 14, which is parallel to the end wall 12 and to the plane defined by the grooves lla, connecting the corner respectivel 17 - members 13,13 and provided with a rib 14a having a semicircular cross section.

Unlike the wafer basket illustrated in Figures 1 and 2, in which each of the corner members 3,3 has an elongated trapezoidal form, the corner members 13,13 in this embodiment of Figure 4 each have a generally orthogonal form having a uniform width from the lower end to the upper end. Instead of having a trapezoidally sloped side line, however, the corner member 13 has a rectangular protrusion 13a in the vicinity of the upper end, i.e. toward the open end of the wafer-insertion grooves lla. When the waf er basket is turned by 900 and mounted on a machine stage S with the tie plate 14 facing downwardly as is illustrated in Figure 5 by a crosssectional view, accordingly, the wafer basket standing on the corner members 13,13 as the legs is necessarily inclined relative to the surface of the machine stage S due to the height difference between two end portions by the width of the rectangular protrusion 13a, so that the same effect as in the first embodiment of Figures 1 and 2 can be obtained to ensure perfect parallelism between the wafers W held by the wafer basket and the surface of the machine stage S. Of course optionally, the protrusion 13a provided on each of the corner members 13,13, which is in an orthogonal form in Figures 4 and 5, may have a different shape such as a trapezoidal or semicircular form as an extension of the corner member 13 or the form of a truncated cone or pyramid 1 ii

Claims

1. In a wafer basket to be contained in the box body of a wafer-holder box, which wafer basket is an integral body formed from a thermoplastic resin in the form of a generally rectangular framework consisting of a pair of oppositely facing side walls each being provided on the inwardly facing surface with a plurality of wafer-insertion grooves running in the up and down direction of the wide walls to open in the upper end thereof, an end wall perpendicular to the side walls connecting the side walls along each of the end lines of the side walls to define a first end plane of the framework, two corner members provided substantially symmetrically each along the other end line of one of the side walls opposite to the end wall to def ine a second end plane of the framework as an extension of the respective side walls and a tie plate connecting the corner members and provided on the outwardly facing surface with a protrusion for positioning of the basket when mounted on a machine stage, the improvement which comprises having each of the corner members formed in such a shape that the width of each of the corner members within the plane of the side wall is larger at or in the vicinity of the upper end than at or in the vicinity of the lower end.

2. The improvement as claimed in claim 1 in which each of the corner members has a form of an elongated trapezoid having a larger width at or in the vicinity of the upper end than at or in the vicinity of the lower end thereof.

3. The improvement as claimed in claim 1 in which each of the corner members is provided with a protrusion at or in the vicinity of the upper end thereof.

4. A wafer basket for locating in the box body of a wafer-holder box, which basket is substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 to 3 or Figures 4 and 5 of the accompanying drawings.

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