System for preventing improper insertion of FOUP door into FOUP

Details System for preventing improper insertion of FOUP door into FOUP System for preventing improper insertion of FOUP door into FOUP

2001-12-13

2003-12-16

Estremsky, Gary (Department: 3677)

Closure fasteners

Bolts

Sliding

C292SDIG001, C206S710000, C220S324000

Reexamination Certificate

active

06663148

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to front opening unified pods, or FOUPs, and in particular to FOUPs which include mechanisms for preventing the FOUP door from being improperly inserted into the FOUP.
2. Description of Related Art
A SMIF system proposed by the Hewlett-Packard Company is disclosed in U.S. Pat. Nos. 4,532,970 and 4,534,389. The purpose of a SMIF system is to reduce particle fluxes onto semiconductor wafers during storage and transport of the wafers through the semiconductor fabrication process. This purpose is accomplished, in part, by mechanically ensuring that during storage and transport, the gaseous media (such as air or nitrogen) surrounding the wafers is essentially stationary relative to the wafers, and by ensuring that particles from the ambient environment do not enter the immediate wafer environment.
A SMIF system has three main components: (1) minimum volume, sealed pods used for storing and transporting wafers and/or wafer cassettes; (2) an input/output (I/O) minienvironment located on a semiconductor processing tool to provide a miniature clean space (upon being filled with clean air) in which exposed wafers and/or wafer cassettes may be transferred to and from the interior of the processing tool; and (3) an interface for transferring the wafers and/or wafer cassettes between the SMIF pods and the SMIF minienvironment without exposure of the wafers or cassettes to particulates. Further details of one proposed SMIF system are described in the paper entitled “SMIF: A TECHNOLOGY FOR WAFER CASSETTE TRANSFER IN VLSI MANUFACTURING,” by Mihir Parikh and Ulrich Kaempf,
Solid State Technology
, July 1984, pp. 111-115.
Systems of the above type are concerned with particle sizes which range from below 0.02 microns (&mgr;m) to above 200 &mgr;m. Particles with these sizes can be very damaging in semiconductor processing because of the small geometries employed in fabricating semiconductor devices. Typical advanced semiconductor processes today employ geometries which are one-half &mgr;m and under. Unwanted contamination particles which have geometries measuring greater than 0.1 &mgr;m substantially interfere with 1 &mgr;m geometry semiconductor devices. The trend, of course, is to have smaller and smaller semiconductor processing geometries which today in research and development labs approach 0.1 &mgr;m and below. In the future, geometries will become smaller and smaller and hence smaller and smaller contamination particles and molecular contaminants become of interest.
FOUPs are in general comprised of a vertically oriented FOUP door which mates with a FOUP shell to provide a sealed, ultraclean interior environment in which wafers may be stored and transferred. The wafers are supported either in a cassette which may be inserted into the shell, or to shelves mounted to the interior of the shell.
In order to transfer wafers between a FOUP and a process tool within a wafer fab, a pod is typically loaded (either manually or automatedly) onto a load port on a front of the tool so that the pod door lies adjacent the port door of the process tool. Thereafter, latch keys within the port door engage a latch assembly within the FOUP door to decouple the FOUP door from the FOUP, and at the same time couple the FOUP door to the port door. Details relating to such a latch assembly within a pod door are disclosed for example in U.S. Pat. No. 4,995,430, entitled “Sealable Transportable Container Having Improved Latch Mechanism”, to Bonora et al., which patent is owned by the assignee of the present application. The assembly disclosed therein includes a two-stage latching operation to securely latch a pod door to a pod shell as shown in prior art FIGS.
1
and
2
A-
2
B. The latch assembly is mounted within the pod door, and includes a latch hub
28
which engages first and second translating latch plates
30
. The port door includes a pair of latch keys that extend into slots
13
formed in the latch hub to thereby rotate the latch hubs clockwise and counterclockwise. Rotation of each latch hub
28
will cause translation of the first and second latch plates
30
in opposite directions.
FIG. 1
is a front view of an interior of the pod door illustrating the latch assembly in the first stage of the door latching operation. When a pod door is returned from its engagement with the port door to the pod, the latch keys within the port door rotate the latch hub
28
to thereby translate the latch plates
30
outwardly so that latch fingers
14
on the distal ends of the latch plates
30
extend in the direction of arrows A into slots
15
formed in the pod shell. The slots
15
conventionally include a transverse wall
17
formed in the pod shell which divides the slot generally in half. The fingers
14
include a space
19
which aligns over the wall
17
when the fingers
14
are received within the slots
15
.
FIG. 2A
is a side view through line
2
—
2
of the latch assembly shown in
FIG. 1
, and
FIG. 2B
is a side view as in
FIG. 2A
but illustrating the second stage of the door latching operation. In particular, the latch hub
28
further includes a pair of ramps
40
so that, after the fingers
14
have engaged within the slots
15
of the pod shell, further rotation of the hub causes the proximal ends
32
of the latch plates engaged with the hub to ride up the ramps. This causes the latch plates to pivot in the direction of arrows B, about axes lying in the plane of each latch plate and perpendicular to the direction of latch plate translation. The effect of this pivoting during the second stage is to pull the pod door tightly against the pod shell to thereby provide a firm, airtight seal between the pod door and shell.
In order to separate a pod door from a pod shell, as when a pod is initially loaded onto a load port interface for wafer transfer, mechanisms within the port door engage the rotatable hub
28
and rotate the hub in the opposite direction than for pod latching. This rotation disengages the latch fingers
14
from the pod shell and allows separation of the pod door from the pod shell.
The Semiconductor Equipment and Materials International (“SEMI”) standard relating to FOUP doors requires that the positions of the door mounting features, i.e., the rotatable latch hubs, the fingers on the latch plates and the slots in the FOUP shell, be symmetrical about a horizontal axis. The authors of the standard believed it would be convenient to allow the FOUP door to be inserted into the FOUP right side up or up side down. However, as it turns out, this symmetry of the mounting mechanisms about the horizontal axis provides a significant disadvantage as explained with reference to FIG.
3
.
FIG. 3
shows a FOUP
20
housing a plurality of wafers
21
. The FOUP door
22
is conventionally provided with a plurality of protrusions
23
defining a plurality of recesses
24
therebetween. The position of the protrusions
23
and recesses
24
are precision controlled so that upon insertion of the FOUP door
22
into FOUP
20
, the wafers
21
within the FOUP seat within recesses
24
to prevent the wafers
21
from getting dislodged. However, if the FOUP door is inserted up side down, the wafers
21
may not align within recesses
24
, and instead the protrusions
23
may contact the wafers
21
. This is true because in a conventional FOUP, a distance X between a top wafer and the top interior surface of the FOUP is different than a distance Y between the bottom wafer and the bottom interior surface of the FOUP, and thus the position of the protrusions and recesses are not symmetrical about the horizontal axis. Contact between the protrusions on the port door and the wafers can result in damage and/or destruction of each of the wafers within the FOUP. Thus, for 300 mm semiconductor wafers, an improper seating of the FOUP door in the FOUP can result insignificant monetary losses.
The error in loading a FOUP door into a FOUP up side down frequently occurs when the FOUP door is manually returned to an empty FOUP. For examp

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