Transport container with an interchangeable inside container

A transport container with an interchangeable, bipartite inside container includes an outside hood, an outside bottom plate, an inside hood, an inside bottom plate, two closing levers, a sealing element and a semiconductor holder. A filter element is built into the container to provide a particle-type transportation container for transporting and storing semiconductor wafers in a semiconductor wafer cassette and for use in differing air pressure conditions and air purity conditions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a transport container with an 
interchangeable, bipartite inside container. 
2. Description of the Related Art 
Transport containers are used during the transportation of semiconductor 
wafers to protect the semiconductor wafers from contamination by ambient 
air which does not meet the highest cleanliness standards. For this 
reason, one of the most important properties of a transport container is 
its particle tightness. 
There are number of possibilities for designing transport containers. For 
example, an especially simple design for a transport container is provided 
when the container is composed only of an outside hood, an outside bottom 
plate, and a semiconductor wafer holder. Another, more complicated 
structure is a transport container having an interchangeable inside 
container within which a semiconductor wafer holder is secured. A common 
feature to all such transport containers is that they have the same size 
and the same outside dimensions in order to be interchangeable with one 
another. They should also comply with certain standardized dimensions. 
Standard dimensions for transport containers are recited, for example, in 
the publication document number 1332 of Semiconductor Equipment and 
Materials Institute, Inc., dated Jan. 10, 1986. The recommended standards 
are summarized under the term "standard mechanical interface for wafer 
cassette transfer" standard, also known as the SMIF standard. All of the 
most important dimensions of a transport container, as well as its 
essential outside component parts are recited in this publication. This 
publication also provides recommendations that the component parts of the 
transport container should meet. 
The publication SMIF-Pod, "The Nucleus of the Asyst-SMIF system" of Asyst 
Technologies, Inc., discloses a transport container having an 
interchangeable inside container. The transport container is manufactured 
in accordance with the aforementioned SMIF specifications and is suitable 
for the acceptance of semiconductor wafers. In cross-sectional drawings, 
the details such as the inside hood semiconductor wafer holder, the 
outside hood, and the bottom plate of the transport container are shown 
being loaded with a semiconductor wafer cassette. 
It is, of course, known to use transport containers for storing and 
transporting semiconductor wafers. Such transport containers are 
manufactured and distributed by various companies such as, for example, 
Asyst and Empak. Previous transport containers, however, involve either 
simple structures in which no inside containers are provided, or involve 
transport containers having inside containers that are not particle-tight. 
The demand made of the particle tightness of these transport containers is 
low, so that they can be utilized only in clean rooms with filtered 
ambient air. Another disadvantage of a simple structured transport 
container is that the transport container must be replaced and cleaned 
after a certain number of process steps in the semiconductor manufacturing 
process. When transport containers having inside containers are used, the 
contaminated inside container is replaced with a new one. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a closeable and dust-tight 
transport container of standardized outside dimensions having a 
semiconductor wafer holder moveably disposed within an inside hood to 
avoid friction. 
This and other objects are inventively achieved by a transport container 
including an inside hood and an inside bottom plate which together form a 
closed inside container and within which is secured an interchangeable 
semiconductor wafer holder secured to the inside hood and moveable 
therewithin by the provision of film hinges. 
The transport container of the present invention is for transporting and 
storing semiconductor wafers in a semiconductor wafer cassette. The 
transport container includes an outside hood and an outside bottom plate, 
an inside hood and an inside bottom plate, two closing levers for 
non-positive closing of the outer hood and the outer bottom plate, and an 
interchangeable semiconductor holder secured to the inside hood. 
The advantages achieved with the invention are that the semiconductor 
transport container, within which are transported semiconductor wafers, 
can be used in or moved through rooms with a lower clean room category and 
can also be used in ambient air. As a result of the novel design of the 
semiconductor wafer holder in the transport container, no additional 
particles are released when loading and unloading a container with 
semiconductor wafers. This is achieved in that the semiconductor wafer 
holder does not have any sliding parts, and touches the inner bottom plate 
only with two narrow ridges. During loading and unloading, this leads to 
the fact that only a rolling motion is carried out at the contacting 
surfaces of the narrow ridges of the semiconductor wafer holder with the 
inner bottom plate. During fluctuating pressure conditions, a filter in 
the inside bottom plate provides a particle-free air stream to ensure that 
clean conditions are maintained within the container. 
Further developments of the invention include providing a sealing element 
or gasket for sealing engagement with the inside bottom plate. An 
assortment of nubs and depressions are provided at various locations to 
assist in alignment and connection of the various parts of the transport 
container. An interchangeable semiconductor wafer holder for mounting 
between the inner hood and the inner base plate is also provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1, a transport container includes an outer bottom plate B1; a 
sealing element, or gasket, D; an inner bottom plate B2; two closing 
levers V; a semiconductor wafer holder H; an inside hood H2; and an 
outside hood H1. On the inner bottom plate B2, two outwardly directed nubs 
or buttons No of different thicknesses extend downwardly therefrom for 
aligning and holding the outer bottom plate B1 by extending into a pair of 
similarly arranged recesses or blind holes Ve. The nubs No and the 
recesses Ve are, in a preferred embodiment, star shaped, although other 
shapes are of course possible. The ensures proper alignment of the inner 
plate B2 with the outer plate B1. 
The sealing element D is composed of an expanded silicone caoutchouc, or 
rubber, ring to which a polyethylene foil or film is applied. The sealing 
element D is inserted into a U-shaped edge, or channel extending around 
the inner bottom plate B2. The sealing element D of the illustrated 
embodiment is rectangular in shape to conform to the container. Four 
L-shaped elevations L are provided extending from the inner bottom plate 
B2 for engagement with a semiconductor wafer cassette CASS (shown in FIG. 
2). 
The outer bottom plate B1 is provided with an opening FO1, and the inner 
bottom plate B2 is provided with an opening FO2 for placement in 
registration with the opening FO1. A filter element, such as the filter 
element F shown in FIG. 2, is provided in the opening FO2 in the inner 
bottom plate B2 so that a particle-free air stream flows therethrough 
during fluctuations in the ambient pressure conditions. 
Each of the two closing levers V for non-positive closing of the outer hood 
H1 to the outer bottom plate B1 are secured by nub-depression connections 
with the outer hood H1. In the illustrated embodiment, a nub No' extends 
laterally from each of the closing levers V for engagement with a recess 
Ve' at either side of the outer hood H1. The closing levers V also include 
projecting edges K1 and K2 at each long side. The projecting edges K1 and 
K2 in the illustrated embodiment are tabs extending opposite one another 
at the ends of the closing levers V. The edges K1 of the closing levers V 
each contain a bore through which pins of a loading and unloading machine 
are conducted in order to automatically open and close the transport 
container. 
The inside hood H2 and the outside hood H1, as well as the semiconductor 
wafer holder H and the inside hood H2, are connected to one another by 
nub-depression connections. Accordingly, nubs No" are provided at a top 
surface of the inside hood H2 for engagement into recesses Ve", shown in 
broken outline, at the inside surface of the outside hood H1. Similarly, 
recesses Ve"' are provided in the semiconductor wafer holder H for 
engagement with nubs within the inside of the inside hood H2. A centering 
ring Z on the inside hood H2 facilitates fast attachment of the inside 
hood H2 to the outside hood H1 by fitting into a similarly shaped recess 
Z', shown in broken outline, at the inside surface of the outside hood H1. 
The recesses Ve" and the ring receiving recess Z' are blind holes and do 
not extend through the wall surface of the outside hood H1 in which they 
are provided. Although other shapes are envisioned, it is preferred that 
the nubs No" and recesses Ve" be of a star shape. 
The dimensions of the individual parts of the transport container of the 
invention are selected to comply with the specifications of the SMIF 
standards for Semiconductor Equipment and Materials Institute, Inc. The 
wall thickness for the inside hood as well as for the inner bottom plate 
amounts to 0.6 mm, whereas a wall thickness of about 3 mm is selected for 
the outer hood and for the bottom plate. The inside hood, the inner bottom 
plate and the semiconductor wafer holder are all manufactured of 
polyethylene, and the outer hood, the outer bottom plate and the closing 
bolt are manufactured of polycarbonate. 
FIG. 2 shown a cross section of the transport container which includes the 
outer plate B1 the sealing element D, the inner bottom plate B2, the two 
closing levers V, the semiconductor wafer holder H, the inside hood H2 as 
well as the outside hood H1. Shown within the transport container is a 
semiconductor wafer cassette CASS, which holds a plurality of 
semiconductor wafers in parallel arrangement. It is preferred that the 
fastening of the semiconductor wafer holder H to the inside hood H2, the 
fastening of the inside hood H2 to the outside hood H1, and the inside 
bottom plate B2 to the outside bottom plate B1 be provided by 
nub-depression connections which have the advantage of being easily 
detachable. 
The projecting edge parts K2 of the closing lever V can be clearly seen in 
FIG. 2 holding the outer bottom plate B1 to the outer hood H1 through the 
sealing element D. Opening of the transport container is carried out by 
moving the closing levers V in the directions indicated by the arrows 
shown in FIG. 2 so that the edge parts K2 no longer lie under the outer 
bottom plate B1. This is accomplished by the pins of the loading and 
unloading machine. As the levers V are moved to the opened condition, a 
spring bias is exerted toward the original closed position by fastening 
clips B of the closing lever V, which are secured to the outside hood H1 
through nub-depression connections and on which are provided the nubs No'. 
Since the transport container is exposed to different pressure conditions, 
a filter element F at the inside of the bottom plate B2 provides a 
particle-free air stream between the inside and the outside of the 
transport container. Instead of providing an additional filter element, it 
is also possible to supply a filter membrane mounted in the inner bottom 
plate B2. 
The semiconductor wafer holder H is seated in a moveable fashion in the 
inside hood H2 by film hinges F1, F2 and F3. A spacer A is also provided 
extending from a rear surface of the holder H to maintain a minimum 
spacing between the semiconductor wafer holder H in the inside hood H2. A 
ledge LE on the inner bottom plate B2 serves to support the lower portion 
of the semiconductor wafer holder H. 
In FIGS. 3 and 4, the sealing element or gasket D is shown and is composed 
of an expanded silicone caoutchouc, or silicone rubber, ring S and a 
polyethylene foil or film P arranged thereabove. The silicone rubber ring 
S, of course, corresponds to the shape of the inner bottom plate B2. The 
thickness of the polyethylene film at a sealing surface DF of the gasket D 
is approximately 0.1 mm. The material hardness of the rubber ring is 
preferably 5 degrees Shore. To increase the particle tightness, the inner 
bottom plate B2 overlaps the silicone rubber ring S. In FIG. 3, the 
sealing element D is in the closed condition in the transport container; 
and in FIG. 4, by contrast, the transport container is open. The outer 
contours of the inside hood H2, the outer bottom plate B1, and the inside 
hood H1 can be clearly seen in both figures. Thus, the inner bottom plate 
B2 has a thin portion overlying the sealing gasket D and a thicker portion 
on either side thereof, the outside edge portion being folded down along 
side the gasket D to form a U-shaped portion. 
FIG. 5 shows the semiconductor wafer holder H for use in the transport 
container. The broken lines of FIG. 5 of the semiconductor wafer holder 
indicate the wall thickness of the material; the wall thickness, for 
example, amounts to 0.6 mm. The wafer holder H includes two lateral 
longitudinal webs LS1 and LS2 and a reinforced middle web M. The 
semiconductor wafers contact the semiconductor wafer holder only at a 
reinforcement VS on the middle web M. Two moveable, narrow mounting webs 
St3 and St4 are attached to a lower portion of the middle web M of the 
semiconductor wafer holder H by two thin film hinges F1. The mounting webs 
St3 and St4 are augmented in the middle by a stationary web St2 that 
serves as a spacer to maintain the holder H spaced from the inside bottom 
plate. 
The upper portion of the wafer holder H includes two depressions Ve'" by 
which the semiconductor wafer holder H is secured to the inner hood H2. 
The depressions Ve'" have a further web arranged perpendicularly to the 
drawing connected to an upper web St1 through a film hinge F3. The upper 
web St1 is connected to the center web M by a film hinge F2. The film 
hinges F2 and F3 are formed thicker and therefore more inflexible than the 
film hinges F1. 
By comparison of FIGS. 2 and 5, the position of the mounting webs St1, St3 
and St4 can be seen, as well as the positions of the film hinges F1, F2 
and F3. Thus, the holder H is hingedly moveable within the inner 
container. 
Although other modifications and changes may be suggested by those skilled 
in the art, it is the intention of the inventor to embody within the 
patent warranted hereon all changes and modifications as reasonably and 
properly come within the scope of his contribution to the art.