U.S. patent application number 09/482390 was filed with the patent office on 2001-07-19 for insert for use in transporting a wafer carrier.
Invention is credited to Rauchut, Joseph C, Reichl, Gary J, Rodolfo, Noel L, Roth, James V JR..
Application Number | 20010008216 09/482390 |
Document ID | / |
Family ID | 23915869 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008216 |
Kind Code |
A1 |
Rauchut, Joseph C ; et
al. |
July 19, 2001 |
Insert for use in transporting a wafer carrier
Abstract
An assembly for storing semiconductor wafers includes a
container, a wafer carrier and a plate. The container may be a box
having a substantially rectangular bottom surface. The wafer
carrier fits in the container. The wafer carrier has a plurality of
slots. Each slot is capable of receiving a semiconductor wafer. The
plate has a size and shape so as to snugly fit in a predetermined
position in the container. The plate substantially prevents motion
of the wafer carrier relative to the container. The plate may be an
insert formed of a separate piece of material from the wafer
carrier. The insert has a substantially rectangular shape so as to
fit snugly on the bottom surface of the box. The insert has at
least one mounting feature to snugly hold the wafer carrier. For
example, the insert may have at least one groove shaped to receive
a tab extending from a bottom of the wafer carrier. The insert may
be formed of an acetyl homopolymer, polypropylene, polyethylene, or
other soft plastic. In an alternative configuration, the plate may
be integrally formed from the same piece of material as the wafer
carrier.
Inventors: |
Rauchut, Joseph C;
(Harleyville, PA) ; Reichl, Gary J; (Coopersburg,
PA) ; Rodolfo, Noel L; (Boston, MA) ; Roth,
James V JR.; (Emmaus, PA) |
Correspondence
Address: |
WILLIAM H. MURRAY
DUANE MORRIS & HECKSCHER LLP
ONE LIBERTY PLACE
PHILADELPHIA
PA
19103-7396
US
|
Family ID: |
23915869 |
Appl. No.: |
09/482390 |
Filed: |
January 12, 2000 |
Current U.S.
Class: |
206/710 ;
206/454; 206/709; 206/711; 211/41.18 |
Current CPC
Class: |
H01L 21/67386 20130101;
H01L 21/67369 20130101 |
Class at
Publication: |
206/710 ;
206/454; 211/41.18; 206/709; 206/711 |
International
Class: |
B65D 085/00; A47G
019/08; B65D 085/30; B65D 085/48 |
Claims
What is claimed is:
1. An insert for a container, the container being shaped to contain
a wafer carrier during transport, the wafer carrier being shaped to
hold a plurality of semiconductor wafers, said insert having a size
and shape so as to snugly fit in a predetermined position in the
container, said insert having at least one mounting feature to
snugly hold the wafer carrier.
2. The insert of claim 1, wherein the container is a box having a
rectangular bottom surface, and the insert has a rectangular shape
so as to fit snugly on the bottom surface of the box.
3. The insert of claim 1, wherein the insert has at least one
groove shaped to receive a tab extending from a bottom of the wafer
carrier.
4. The insert of claim 1, wherein the insert is formed of one of
the group consisting of an acetyl homopolymer, polypropylene, and
polyethylene.
5. An assembly for storing semiconductor wafers, comprising: a
container; a wafer carrier that fits in the container, the wafer
carrier having a plurality of slots, each slot capable of receiving
a semiconductor wafer; and a plate to which the wafer carrier is
attached, the plate having a size and shape so as to snugly fit in
a predetermined position in the container, said plate substantially
preventing motion of the wafer carrier relative to the
container.
6. The assembly of claim 5, wherein the plate is an insert formed
of a separate piece of material from the wafer carrier, said insert
having at least one mounting feature to snugly hold the wafer
carrier.
7. The assembly of claim 6, wherein the container is a box having a
substantially rectangular bottom surface, and the insert has a
substantially rectangular shape so as to fit snugly on the bottom
surface of the box.
8. The assembly of claim 6, wherein the insert has at least one
groove shaped to receive a tab extending from a bottom of the wafer
carrier.
9. The assembly of claim 6, wherein the insert is formed of one of
the group consisting of an acetyl homopolymer, polypropylene, and
polyethylene.
10. A method for handling at least one semiconductor wafer,
comprising the steps of: (a) snugly fitting an insert in the bottom
of a container; (b) mounting a wafer carrier on the insert; (c)
inserting the at least one semiconductor wafer in the wafer
carrier; and (d) transporting the container, with the insert, wafer
carrier and at least one wafer contained therein.
11. The method of claim 10, wherein step (a) includes fitting a
substantially rectangular insert on a substantially rectangular
bottom surface of the container.
12. The method of claim 10, wherein step (b) includes fitting at
least one tab of the wafer carrier into a corresponding slot in the
insert.
13. The method of claim 10, wherein the insert is formed of one of
the group consisting of an acetyl homopolymer, polypropylene, and
polyethylene.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to semiconductor
fabrication, and more specifically to apparatus for storing and
transporting semiconductor wafers.
DESCRIPTION OF THE RELATED ART
[0002] FIG. 1 shows a conventional assembly 10 for transporting
semiconductor wafers 40. A container 20 has a box bottom 22 and a
box cover 24. Inside the container 20 is a wafer carrier or
cassette 30 that holds a plurality of semiconductor wafers 40. The
wafer carrier 30 is a tray having a plurality of slots formed
between adjacent pairs of ribs 34. Although only one pair of ribs
34 is visible in FIG. 1, one of ordinary skill understands that a
plurality of ribs are arranged from front to back in planes
parallel to the ribs 34 shown in FIG. 1. A respective slot is
formed between each successive set of ribs 34. Each slot is capable
of storing a respective wafer 40. Although only one wafer 40 is
shown in FIG. 1, one of ordinary skill understands that a plurality
of wafers are arranged from front to back in planes parallel to
wafer 40. The box 20 with the wafer carrier 30 and wafers 40 inside
may be transported between different processing stations, typically
on wheeled carts.
[0003] The exemplary wafer carrier 30 also has right and left
rearwardly projecting tabs 36 on its bottom, extending in a
direction perpendicular to the plane of FIG. 1. A pair of
stiffening ribs 38 are integrally formed at the front and rear ends
of the wafer carrier 30. A structural cross member 32 is provided
in the front of the wafer carrier 30, and a similar cross member is
present in the back. The wafer carrier 30 is typically made from a
carbon impregnated polypropylene material or similar material.
Exemplary wafer carrier systems such as that shown in FIG. 1 are
manufactured by Entegres, Inc., Chaska, Minn. (formerly Fluoroware,
Inc.).
[0004] Because they contain a large number of wafers 40 in known
positions, the wafer carriers 30 are useful in automated
semiconductor processing. The wafers 40 can be automatically
removed from the wafer carrier 30 for processing in an automated
wafer processing system (not shown). For example, an ion implant
system includes various wafer handling mechanisms for transferring
semiconductor wafers into and out of the ion implanter. Some ion
implant systems include a wafer clamp for transferring
semiconductor wafers from the wafer carrier in which they are
stored, onto an ion implanter disk. The wafer clamp grasps the
wafer while it is disposed in the carrier, removes it from the
carrier, and places it on the ion implanter disk.
[0005] Experience with wafer handling systems has shown that, after
transport, upon removal from the wafer carrier, wafers often have
an unacceptable number of contaminant particles on their surfaces.
These contaminant particles interfere with the processing of the
wafers.
[0006] An improved method and system for handling semiconductor
wafers is desired.
SUMMARY OF THE INVENTION
[0007] One aspect of the invention is an insert for a container.
The container is shaped to contain a wafer carrier during
transport. The wafer carrier is shaped to hold a plurality of
semiconductor wafers. The insert has a size and shape so as to
snugly fit in a predetermined position in the container. The insert
has at least one mounting feature to snugly hold the wafer
carrier.
[0008] Another aspect of the invention is an assembly for storing
semiconductor wafers, including: a container, a wafer carrier and a
plate to which the wafer carrier is attached. The wafer carrier
fits in the container. The wafer carrier has a plurality of slots,
each slot capable of receiving a semiconductor wafer. The plate has
a size and shape so as to snugly fit in a predetermined position in
the container and substantially prevent movement of the wafer
carrier relative to the container.
[0009] Another aspect of the invention is a method for handling at
least one semiconductor wafer. an insert is snugly fitted in the
bottom of a container. A wafer carrier is mounted on the insert. At
least one semiconductor wafer is inserted in the wafer carrier. The
container is transported with the insert, wafer carrier and at
least one wafer contained therein.
[0010] The above and other features of the present invention will
be better understood from the following detailed description of the
exemplary embodiment of the invention which is provided in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross sectional view of a conventional container
and wafer carrier assembly for transporting semiconductor
wafers.
[0012] FIG. 2 is cross sectional view of a container and wafer
carrier according to the present invention for transporting
semiconductor wafers.
[0013] FIG. 3 is a top plan view of the insert shown in FIG. 2.
[0014] FIG. 4 is a front elevation view of the insert shown in FIG.
3.
[0015] FIG. 5 is a side elevation view of the insert shown in FIG.
3.
DETAILED DESCRIPTION
[0016] The inventors have observed that, when using prior art wafer
transport assemblies, particle formation during wafer transport is
related to movement of the wafer carrier within the container. In
many processing facilities, the floor of the building in which the
processing equipment is located is not perfectly flat.
Consequently, the wafer carrier and wafers are jostled about within
the container. As the wafer carrier bumps into the inner walls of
the container, small particles are released or abraded from the
wafer carrier and adhere on the wafers themselves.
[0017] FIG. 2 is a cross sectional view of an improved wafer
transport assembly 100. The improved transport assembly 100 reduces
and substantially eliminates movement of the wafer carrier 130
within the container 120 during transport. In particular, the
addition of a plate (which may be an insert 150) causes the wafer
carrier 130 to fit snugly within the container 120, reducing the
motion.
[0018] In the exemplary embodiment, the insert 150 is a separate
piece that can be retrofitted into an existing transport container
120 and wafer carrier 130 assembly. For any given container 120 and
wafer carrier 130, an insert 150 may be designed to snugly fit into
the container bottom 122, with a customized set of features (such
as slots and wells) that closely matches any tabs, legs and/or
projections on the bottom of the wafer carrier 130.
[0019] As shown in FIG. 2, a container 120 has a box bottom 122 and
a box cover 124. Inside the container 120 is a wafer carrier 130
that holds a plurality of semiconductor wafers 140. The wafer
carrier 130 is a tray having a plurality of slots formed between
adjacent pairs of ribs 134. Although only one pair of ribs 134 is
visible in FIG. 2, one of ordinary skill understands that a
plurality of ribs are arranged from front to back in planes
parallel to the ribs 134 shown in FIG. 2. A respective slot is
formed between each successive set of ribs 134. Each slot is
capable of storing a respective wafer 140. Although only one wafer
140 is shown in FIG. 2, one of ordinary skill understands that a
plurality of wafers are arranged from front to back in planes
parallel to wafer 140. The box 120 with the wafer carrier 130 and
wafers 140 inside may be transported between different processing
stations, typically on wheeled carts.
[0020] The exemplary wafer carrier 130 also has right and left
downwardly projecting tabs 136 on its bottom, extending in a
direction perpendicular to the plane of FIG. 2. A pair of
stiffening ribs 138 are integrally formed at the front and rear
ends of the wafer carrier 130. A structural cross member 132 is
provided in the rear of the wafer carrier 130, and a similar cross
member is present in the front. The wafer carrier 130 is typically
made from a carbon impregnated polypropylene material or similar
material. Exemplary wafer carriers 130 and containers 120 such as
those shown in FIG. 2 are manufactured by Entegres, Inc., Chaska,
Minn.
[0021] As shown in FIG. 2, the insert 150 has a pair of slots 151
that snugly receive the projecting tabs 136 of the wafer carrier
130. Thus, with the insert 150 in place, the wafer carrier 130 has
no freedom of movement within the container 120.
[0022] FIGS. 3-5 show the exemplary insert 150, which is suitable
for use in a "Entegres.RTM." wafer transport assembly 120, 130,
manufactured by Entegres Inc. of Chaska, Minn. The box bottom 122
has a substantially rectangular bottom surface, and the insert 150
has a substantially rectangular shape so as to fit snugly on the
bottom surface of the box 122. The insert 150 has a pair of
elongated grooves 151 for receiving the tabs 136 of the wafer
carrier 130. Additional features of the grooves 151 include
chamfers or bevels 153 which facilitate insertion of the tabs 136
into the main, snug fitting grooves 152. Each end of the grooves
151 includes a rounded cutout 154 for receiving a corresponding
protuberance on the bottom of the wafer carrier 136.
[0023] In addition to the slots 151, the insert 150 has a variety
of features for facilitating insertion. For example, all four sides
of the insert 150 have chamfers or bevels 158, and all four corners
have chamfers or bevels 159. Further, several small wells or bores
155, 156 and 157 are included in the insert, to accommodate
specific pads and projections in the exemplary "Entegres.RTM." box
bottom 122.
[0024] The insert 150 may be formed from a variety of materials,
including but not limited to an acetyl homopolymer, polypropylene,
polyethylene and other soft plastics. Exemplary inserts 150 have
been formed from white "DELRIN.RTM." acetyl resin material,
manufactured by the Dupont Corporation of Wilmington, Del., and
from "ACETRON.RTM." acetyl resin, manufactured by DSM Engineering
Plastic Products, Inc., Reading, Pa. The material may be cut from
sheet stock and machined, for example, using a numerically
controlled milling machine.
[0025] Another aspect of the invention is a method for handling one
or more semiconductor wafers. The method includes snugly fitting an
insert 150 in the bottom of a container 120; mounting a wafer
carrier 130 on the insert 150; inserting one or more semiconductor
wafers 140 in the wafer carrier 130; and transporting the container
120, with the insert 150, wafer carrier 130 and the wafer(s)
contained therein. Preferably, the method includes fitting at least
one feature (such as a tab 136) of the wafer carrier 130 into a
corresponding slot 151 in the insert 150.
[0026] Advantageously, the exemplary insert 150 is mounted in the
container 120 without any tools, and the exemplary wafer carrier
130 is attached to the insert without any tools. By carefully
selecting the size of the slot 151 (or other feature) to snugly fit
the existing tabs 136 on the bottom of the wafer carrier 130, the
insert 150 is attached by a simple press fit.
Experimental Data
[0027] Tables 1 and 2 provide comparative data for increase in the
number of particles on semiconductor wafers during transport. The
data were collected using a "SURFSCAN 6220" laser scanner to count
the number of contaminant particles on each wafer. Table 1 includes
data collected in a conventional wafer transport assembly as shown
in FIG. 1. Table 2 includes data collected in a wafer transport
assembly according to the invention, as shown in FIG. 2. In each
table, the "pre-transport" column indicates the number of particles
on the wafers before transport in the container and wafer carrier.
The "post transport" column indicates the number of particles on
the wafers after transport in the container and wafer carrier. The
"gain" column (the difference between pre-transport and
post-transport values) indicates the number of particles that
adhere to each wafer during transport.
1TABLE 1 PRIOR ART CONFIGURATION SLOT PRE-TRANSPORT POST-TRANSPORT
GAIN 15 3 601 598 14 3 644 641 13 9 467 458 12 6 414 408 11 0 383
383
[0028] As demonstrated in Table 1, a significant number of
particles adhered to each wafer during transport, as measured by
the gain column. The average gain among the five wafers during
transport was 498 particles per wafer.
2TABLE 2 USING INSERT SLOT PRE-TRANSPORT POST-TRANSPORT GAIN 15 9
89 80 14 3 158 155 13 4 117 113 12 13 136 123 11 8 123 115
[0029] The data in Table 2 show a substantial reduction in the gain
(number of particles that became adhered to each wafer during
transport) compared to the average gain without the insert in the
container. The average gain by each wafer when the insert was in
place during transport was 117 particles per wafer. This represents
a 76% reduction in particles that adhered to the wafers during
transport, when compared to the data of table 1.
[0030] The data show a dramatic decrease (by a factor or four) in
the number of particles when the insert was included.
Other Exemplary Variations
[0031] Although the exemplary insert 150 has slots 152 to
accommodate tabs 136 in the bottom of the wafer carrier 130, any
feature on the bottom of the wafer carrier may be accommodated. For
example, if a wafer carrier has slots on its bottom (not shown), a
corresponding insert may have tabs or other projections to snugly
fit into the slots of the bottom of the wafer carrier. Similarly,
if the wafer carrier has a different number of tabs than the
exemplary wafer carrier 130, the number of slots in the insert may
be varied to accommodate the wafer carrier.
[0032] Although the exemplary insert is symmetrical (and capable of
insertion in either of two positions rotated 180 degrees apart from
each other), an insert may alternatively be keyed, so that it can
only fit inside the box bottom 122 in a single position.
[0033] Although the exemplary embodiment of the invention includes
a separate insert to be added to an existing assembly including a
container 120 and a wafer carrier 130, other embodiments are also
contemplated. For example, the wafer carrier and "insert" may be
formed (e.g., molded) from a single piece of material. This single
body would include a plurality of slots for receiving wafers, like
conventional wafer carriers. In addition, the body would have a
bottom plate shaped like the insert described above with reference
to FIGS. 2-5. The bottom plate would be integrally attached to the
bottom of the wafer carrier. The bottom plate would conform to the
shape of the box bottom 122 of the container 120, and would have a
perimeter shaped to snugly fit within the perimeter of the box
bottom 122.
[0034] Although the exemplary insert is rectangular, to fit a
rectangular container, the insert (or plate) may have any shape to
fit a non-rectangular container.
[0035] Although the invention has been described in terms of
exemplary embodiments, it is not limited thereto. Rather, the
appended claim should be construed broadly, to include other
variants and embodiments of the invention which may be made by
those skilled in the art without departing from the scope and range
of equivalents of the invention.
* * * * *