SMIF load port interface including smart port door

Details SMIF load port interface including smart port door SMIF load port interface including smart port door

2001-07-13

2003-03-11

Keenan, James W. (Department: 3652)

Material or article handling

Device for emptying portable receptacle

With container opening means

C414S940000

Reexamination Certificate

active

06530736

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a standard mechanical interface (SMIF) load port assembly including a so-called “smart” port door, and in particular to a SMIF load port assembly including a port door position compensation assembly capable of dynamically adjusting a relative spacing between a front surface of a port door and a front surface of a pod loaded onto the load port assembly so as to compensate for any misalignment of the front surface of the pod.
2. Description of Related Art
A SMEF 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.
The SMIF system provides a clean environment for articles by using a small volume of particle-free gas which is controlled with respect to motion, gas flow direction and external contaminants. Further details of one proposed system are described in the paper entitled “SMIF: A TECHNOLOGY FOR WAFER CASSETTE TRANSFER IN VLSIMANUFACTURING,” 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 0.5 &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 become of interest.
A SMIF system has three main components: (1) minimum volume, sealed pods used for storing and transporting wafer cassettes; (2) a minienvironment supplied with ultraclean air flows surrounding cassette load ports and wafer processing areas of processing stations so that the environments inside the pods and minienvironment become miniature clean spaces; and (3) robotic transfer assemblies, such as load ports, to load/unload wafer cassettes and/or wafers from the sealed pods to the processing equipment without contamination of the wafers in the wafer cassette from external environments. The system provides a continuous, ultraclean environment for the wafers as they move through the wafer fab.
SMIF pods are in general comprised of a pod door which mates with a pod shell to provide a sealed environment in which wafers may be stored and transferred. So called “bottom opening” pods are known, where the pod door is horizontally provided at the bottom of the pod, and the wafers are supported in a cassette which is in turn supported on the pod door. It is also known to provide front opening unified pods, or FOUPs, in which the pod door is vertically oriented, and the wafers are supported either in a cassette mounted within the pod shell, or to shelves mounted in the pod shell. Front opening pods include a door having a rear surface which is included as part of the sealed pod environment, and a front surface which is exposed to the environment of the wafer fab.
FIG. 1
is a prior art perspective view of a 300 mm front opening SMIF pod
20
including a pod door
22
mating with a pod shell
24
to define a sealed environment for one or more workpieces located therein.
FIG. 2
is a prior art perspective view of a 300 mm load port assembly
23
for transferring wafers between the pod
20
and a process tool
28
to which the load port assembly
23
is affixed. In order to transfer the workpieces between pod
20
and process tool
28
, the pod is manually or automatedly loaded onto a pod advance plate
25
so that a front surface
31
of the pod door faces a front surface
30
of a port door
26
in the load port assembly.
The front surface
30
of the port door
26
includes a pair of latch keys
32
which are received in a corresponding pair of slots
33
of a door latching assembly mounted within pod door
22
. An example of a door latch assembly within a pod door adapted to receive and operate with latch keys
32
is disclosed in U.S. Pat. No. 4,995,430 entitled “Sealable Transportable Container Having Improved Latch Mechanism”, to Bonora et al., which patent is assigned to the owner of the present invention, and which patent is incorporated by reference herein in its entirety. In order to latch the pod door to the port door, the pod door
22
is seated adjacent the port door
26
so that the vertically oriented latch keys are received within the vertically oriented slots
33
.
In addition to decoupling the pod door from the pod shell, rotation of the latch keys
32
also lock the keys into their respective slots
33
, thus coupling the pod door to the port door. There are typically two latch key
32
and slot
33
pairs, each of which pairs are structurally and operationally identical to each other.
The pod advance plate
25
typically includes three kinematic pins
27
, or some other registration feature, which mate within corresponding slots on the bottom surface of the pod to define a fixed and repeatable position of the bottom surface of the pod on the advance plate and load port assembly.
Referring to
FIG. 3
, the pod advance plate
25
is translationally mounted to advance the pod toward and away from the load port. Once a pod is detected on the pod advance plate by sensors in the load port assembly, the pod is advanced toward the load port in the direction of arrow A—A until the front surface
31
of the pod door
22
lies in contact with the front surface
30
of the port door
26
. It is desirable to bring the front surfaces of the respective doors into contact with each other to trap particulates and to ensure a tight fit of the port door latch key in the pod door key slot. However, some process tool manufacturers require that a small space be provided between the port plate surrounding the port door and the pod shell flange at the front edge of the pod shell after the pod has advanced. This space prevents any possible contact between the port plate and the front surface of the pod due to a misaligned front pod surface as explained below.
Once the pod and port doors are coupled, horizontal and vertical linear drives within the load port assembly move the pod and port doors together toward the process tool, and then away from the load port so that wafers may thereafter be transferred between the interior of the pod
20
and interior of process tool
28
.
Regardless of the desired relative positions of the pod and port doors after pod advance, it is necessary to precisely and repeatably control this relative positioning to ensure proper transfer of the pod door onto the port door and to prevent particulate generation. hI order to establish the desired relative positions, conventional load port assembly systems rely on the fact that the kinematic pins establish a fixed and known position of the pod on the load port assembly so that, once seated on the kinematic pins, the pod may simply be advanced toward the load port a fixed amount to place the front surfaces of the respective doors in the desired relative positions.
However, it is a drawback to conventional front opening load port assemblies that the system aligns the bottom surface of the pod to the load port assembly by the kinematic pins, but registers

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