End effector for substrate handling

Details End effector for substrate handling End effector for substrate handling

2000-02-14

2001-09-04

Dunn, Tom (Department: 1725)

Metal fusion bonding

Including means to force or clamp work portions together...

C228S044700, C228S049100, C228S049500

Reexamination Certificate

active

06283355

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to substrate handling, and more particularly, to towers for positioning substrates and to methods of efficiently manufacturing the towers, components of such towers, and end effectors using such towers and components.
2. Description of the Related Art
Transport chambers are generally used in conjunction with a variety of substrate processing chambers, which may include semiconductor processing systems, material deposition systems, and flat panel display processing systems. Growing demands for cleanliness and high processing precision increase the need for reduced amounts of human interaction between the processing steps. This need has been partially met by transport chambers, which operate as intermediate handling apparatus between such processing steps.
In the use of transport chambers, when a substrate is required for processing, a robot arm within the transport chamber may be used to retrieve a selected substrate from storage and place it into one of the multiple processing chambers. Transport of substrates among multiple storage facilities and processing chambers is typically referred to as cluster tool architecture.
FIGS. 1A and 1B
schematically illustrate a typical cluster tool architecture. substrates
101
may be stored in a clean room
102
. The substrates
101
may be the base on which layers are deposited in semiconductor processing, or by the material deposition systems, or may be a support used in the flat panel display processing systems, for example. Such substrates are very fragile, giving rise to a need to carefully handle the substrates. The substrates
101
are commonly referred to as wafers.
A load lock
104
is generally coupled to the clean room
102
. In addition to being a retrieving and serving mechanism, the load lock
104
also serves as a pressure varying interface between the clean room
102
and a transport chamber
106
that interfaces with various processing chambers
108
a
-
108
c
.
FIG. 1B
shows in more detail a cassette
110
in the clean room
102
for storing the substrates
101
. The load lock
104
has a prior art end effector
112
within it. A drive assembly
114
serves to move an arm assembly
116
connected to the end effector
112
. As described below, the prior art end effector
112
is made by alternately stacking prior art spatulas
118
and spacers
120
. The load lock
104
also interfaces with the various processing chambers
108
a
-
108
c
by way of a main robot arm
122
of the transport chamber
106
.
In use, the end effector
112
of the load lock
104
is moved through a port
124
of the clean room
102
and receives a supply of the wafers
101
. In detail, each spatula
118
receives one of the wafers
101
from the cassette
110
and supports the wafer
101
for transport. The end effector
112
is then moved out of the clean room
102
and back into the load lock
104
, where the wafers
101
are stored prior to being used for processing. Such processing is initiated by the main robot arm
122
. reaching into the load lock
104
and removing one of the wafers
101
from the supported position on the spatula
118
.
It may be appreciated that two wafer transfer operations are required to move the wafers
101
from the clean room
102
into a processing chamber
108
, and that each such transfer operation is to be accomplished without human intervention. For the first transfer, the spatulas
118
of the end effector
112
must be aligned with the wafers
101
contained in the cassette
110
. If not aligned, horizontal movement of the end effector
112
toward the cassette
110
may cause one or more of the spatulas
118
to move horizontally and hit one or more of the wafers
101
. Such hitting may break the wafers
101
, or otherwise damage the wafers
101
, as by scratching an upper device surface
126
, of the wafers
101
. While this type of damage to a wafer
101
is a significant cost factor in such processing, a greater cost factor results when the end effector
112
is not aligned with the main robot arm
122
in a second wafer transfer operation. For example, when the processing of the wafer
101
is substantially complete, the value of the wafer
101
includes the increased cost of the processing that has taken place since the wafer
101
left the clean room
102
. However, the first wafer transfer operation has a greater potential of damaging multiple wafers, resulting in a higher cost of production.
Attempts have been made to provide end effectors
112
with spatulas
118
accurately aligned with both the cassette
110
(and the wafers
101
therein) and the main robot arm
122
. One such attempt is to make a stack of alternating spatulas
118
and spacers
120
as shown in FIG.
1
C. There, bolts
132
are illustrated for squeezing the spatulas
118
and the spacers
120
together to form the end effector
112
. Referring to
FIG. 1C
, a desired relative positioning of the spatulas
118
is depicted by reference lines
128
. This desired relative positioning will properly align each spatula
118
with the wafers
101
that are in the cassette and with the robot arm
122
for transfer among the cassette
110
, the load lock
104
, and the transport chamber
106
. To achieve the desired relative spacing of the spatulas
118
of the end effector
112
, attempts are made to hold the thickness T of every one of the spacers
120
and every one of the spatulas
118
within a very close tolerance. For example, the same desired relative positioning is indicated in
FIG. 1D
by the reference lines
128
. However, the actual relative positioning (shown by reference lines
130
and
130
U) differs significantly from the desired relative positioning even though the spatulas
118
and the spacers
120
are within the desired tolerance (are in-tolerance). In this example, the significant difference is due to the thickness TT of spacers
120
TT being at the thick end of the tolerance. Such thicknesses TT are shown in
FIG. 1D
accumulating, and resulting in and in-tolerance spacer
120
and the in-tolerance upper spatulas
118
U being positioned above the reference lines
128
and
128
U, indicating misalignment of the spatulas
118
U. Such misalignment of the spatulas
118
U with the reference lines
128
and
128
U resulting from the accumulation of tolerances is referred to as tolerance stacking. Although not shown in
FIG. 1D
, such misalignment of the spatulas
118
U with the reference lines
128
may also result from the accumulation of tolerances that are at the thin end of the desired tolerance. Tolerance stacking is a significant cause of the wafer damage problem described above.
These misalignment problems not only cause the noted wafer damage problems, but may also result in damage to the prior art end effectors
118
. Such end effector damage may require retooling of the prior art end effector
118
, such as by shutting down the operation of the load lock
104
, removing the prior art end effector
112
and replacing any broken spatulas
118
, for example.
It may be appreciated that the use of the stacked spatulas
118
and the spacers
120
for the prior art end effectors
112
is dependent on the success of expensive efforts to make each of the spatulas
118
and each of the spacers
120
within very tight tolerances, e.g. plus or minus 0.0005 inches. Also, selection of spatulas
118
and spacers
120
for use in a particular end effector
112
, and other costly steps necessary to attempt to reduce tolerance stacking in stacked arrangements of spatulas
118
and spacers
120
, give rise to an unfilled need to avoid using the stacked arrangements. Further, when these expensive manufacturing efforts fail, the noted significant cost factors (e.g., damage to an unprocessed wafer
101
, or misalignment of the end effector
112
, causing damage to a wafer
101
that has been substantially completely manufactured), are but a part of the resulting costs because process shut-down and reworking of the end effectors
112
ma

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