Shock resistant variable load tolerant wafer shipper

Details Shock resistant variable load tolerant wafer shipper Shock resistant variable load tolerant wafer shipper

2001-05-08

2003-04-22

Fidei, David T. (Department: 3728)

Special receptacle or package

Holder for a removable electrical component

For a semiconductor wafer

C206S303000

Reexamination Certificate

active

06550619

ABSTRACT:

BACKGROUND OF THE INVENTION
Integrated circuits are manufactured from semiconductor wafers that are conventionally round in shape and made of highly brittle silicon. Such wafers are subjected to a variety of processing steps in transforming the semiconductor wafer into integrated circuit components. The various processing steps must be performed under ultra-clean conditions to minimize the potential of contamination of the wafers as they are being processed. Each wafer may be subjected to dozens if not hundreds of steps in its processing cycle. The potential for contamination and destruction of a wafer or reduction in yield is ever present throughout the various processing and packaging steps. Particularly during the steps that take place at fabrication facilities any minute particulates can destroy the integrated circuit on which it falls. Once the processing steps of the wafers are completed they are generally shipped while still in wafer form to a facility that will dice and capsulate in integrated circuit packaging each individual circuit on the wafer.
The stringent particulate control that takes place during the processing steps is generally not necessary in shipping the completed wafers to the facility that dices and packages the individual circuits.
Traditionally, during the processing and storage and shipping of semiconductor wafers the wafers are supported and constrained at their edges to prevent any contact and possible damage and contamination to the faces of the wafers having the circuits thereon.
Even as semiconductor wafers are getting larger in scale, now up to 300 millimeters in diameter, the density of components is getting significantly greater. Moreover, disks are also are getting thinner providing much thinner completed integrated circuit packages. This has been driven, at least in part, by the cellular phone industry that has sought thinner cell phones.
Accompanying the trend towards larger, more dense and thinner wafers, the wafers are becoming more valuable, more brittle, more easily damaged during shipment. Although it is possible, desirable, and common to ship thicker wafers in enclosed containers that would support the wafers exclusively by their edges, using such devices to ship the thinner wafers has proven problematic due to breakage and damage of the wafers. Foam material, such as urethane, is used to cushion the top and bottom of the stack.
Thus for the thinner more fragile wafers, enclosures are utilized which have the wafers axially stacked on top of one another and separated by layers of paper-like flexible sheet material. Thus the support of each wafer is by adjacent wafers and the entire stack of wafers.
Referring to
FIG. 1
, prior art wafer carrier as illustrated in U.S. Pat. No. 5,553,711 to Lin discloses a container that has a base, upright sidewalls defining a circular pocket, wafer dividers and a cover that comes down and threadingly attaches to the base.
FIG. 2
discloses a conventional wafer carrier in which the enclosure is defined by a cookie tin like plastic container having a bottom
40
, a top lid
42
and utilizing a circular urethane foam bottom cushion
44
, and sheet material
49
interspersed between wafer
50
.
Referring to
FIGS. 2 and 3
, another wafer shipper is disclosed for shipping the stacked wafers with dividers therebetween. This wafer shipper has a base
52
and a top cover
54
. The base and top cover are injection molded and have circular shaped and axially extending structural members
56
,
58
in the base component. Similarly, the top cover has axially extending circular structural members
59
and
60
and radially extending ribs
66
,
69
that also project axially.
These stacking wafer shippers may be both manually handled as well as robotically handled. Thus, means for opening and closing such containers must be both manually and robotically operable and for manual purposes should be intuitive as well as simple, reliable, and quick. Various means are known for latching such wafer shippers. These include threads such as shown in prior art
FIG. 1
, a snap-on seal as shown in prior art
FIG. 2
, a minimal rotation thread, and axially projecting spring latches.
The wafer shippers that use the threaded engagements are awkward and subject to misalignment and improper attachment. These wafer shippers visually appear symmetrical in at least two planes and therefore there are typically four different options in assembling a top cover to a bottom cover. However, conventional prior art shippers generally require that the top cover be assembled in a specific orientation for proper latching.
U.S. Pat. No. 6,193,068 to Lewis, et al. discloses axially extending spring latches and utilizes a double wall to define the pocket for the stack of wafer carriers. Said double wall thickness is defined by two spaced thin wall sections which are not attached to one another extending from the base. This configuration appears to allow the individual unsupported thin walls supported only at the base to take on and retain deformation. The concentric arrangement of the thin walls makes any such deformation visibility apparent. The double sidewall in this prior art embodiment may help to isolate direct impact on the top cover from direct communication from top cover structure to the wall defining the wafer pocket.
In the embodiment shown in
FIGS. 7
,
8
,
9
, and
10
, any separation stress will occur as illustrated by G in FIG.
11
. Such loading of the wafer shipper also can cause the deformation of the otherwise planar corners of the base to be stressed out of position causing wobbling when placed on a planar surface and error in seating when placed on a machine interface. Such deformation can be caused in part by an overloading condition and also in part by the structural configuration of the wafer shipper.
It would be desirable to provide sufficient structure in the base of such wafer shipper to prevent such distortion and bowing. Moreover, it would be highly desirable to provide a wafer carrier that has indicating means therein to prevent such an overloaded condition.
Referring to
FIGS. 12
,
13
,
14
, and
15
a further prior art wafer shipper is shown. This wafer shipper has stunted threads
82
,
84
that allow the wafer carrier to be rotated less than 30° to accomplish the latching. This wafer carrier has the difficultly of requiring relatively precise angular positioning for initial placement of the top cover on the base before said rotation.
This embodiment utilizes axially projecting double thin wall similar to the prior art embodiment of
FIGS. 8
,
9
and
10
, although the double sidewalls are connected at the ends of each segment. Thus, four separate wall portions are defined all of which are distinct from one another and integral with the base. Due to the connecting portions
94
which connect each of the pairs of thin sidewall segments, a direct impact blow on the top cover will transmit the force of such blow directly from the top cover through said connecting portions
94
to the wafers. This top cover also has features configured as nubs, which may engage a floppy disk. See
FIG. 16
that is a cross-sectional of the wall at one of said nubs.
Generally all embodiments of the wafer carriers herein will be injection molded of thermoplastic material such as polypropylene. Such material requires structure such as ribs and channels for rigidity.
In that these shippers do not have the severe particulate control issues that are necessary for carriers in the fab processing environment, it is not necessary to have hermetic sealing. In fact, such hermetic sealing is inimical to robotic handling and easy manual handling, specifically the opening and closing of the shippers. Still it is important to have the interface between the top cover and the base to provide as good of sealing characteristics as possible. Moreover, it is important to eliminate or reduce any bowing that occurs along one of the sidewalls intermediate the corners of the top cover or the base.
These types of containers may be utilized once and thrown a

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