Photocopying – Projection printing and copying cameras – Methods
Reexamination Certificate
2002-02-01
2003-06-10
Fuller, Rodney (Department: 2851)
Photocopying
Projection printing and copying cameras
Methods
C355S053000, C414S935000, C414S941000
Reexamination Certificate
active
06577382
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a substrate transport method, a substrate transport apparatus, an exposure apparatus, and a device manufacturing method. More particularly, the present invention relates to a substrate transport method and substrate transport apparatus suitable for loading a wafer serving as a substrate onto a wafer stage of an exposure apparatus, or unloading a wafer from a wafer stage, and to an exposure apparatus using this, and to a device manufacturing method using the exposure apparatus. This application is a continuation application based on PCT/JP98/05453.
BACKGROUND ART
FIG.
62
and
FIG. 63
are diagrams for explaining the construction of a conventional substrate transport apparatus.
FIG. 62
is a plan view, and
FIG. 63
is an elevation view of an arm section. The substrate transport apparatus comprises a load arm
412
and an unload arm
413
, and they are able to move back and forth along a longitudinal direction of an arm guide
414
while being guided thereby so as not to interfere with each other. Furthermore, each arm
412
and
413
respectively incorporates a pair of substrate support portions
412
a
and
413
a
. On the tip ends of these are formed wafer attraction portions
412
b
and
413
b.
An unprocessed wafer W which has been transported to the position shown in the figure by the load arm
412
, is transferred to pins of an XY stage side (not shown in the figure), on release of attraction by the wafer attraction portions
412
b
. The load arm
412
which has completed transfer is then retracted and moved to bring in another wafer W. The wafer W which has been transferred to the pins is attracted and held on a mounting table of the XY stage with the lowering of the pins, and is moved to another location together with the XY stage, to be subjected to predetermined processing such as exposure.
The unload arm
413
is moved to the standby position shown in the figure, either during processing of the wafer W or immediately after processing. When the wafer W for which processing has been completed comes to the position shown in the figure together with the XY stage, the pins and the wafer W are raised. Then, at the stage where the wafer W has been raised to a higher position than the substrate support portion
413
a
, the unload arm
413
is moved to the transfer position shown by the load arm
412
in the figure, and the wafer W is received.
However, in the substrate transport apparatus as described above, the standby position of the unload arm
413
must be such that the arm is separated more than a distance “d” from the wafer W so that the wafer attraction portions
413
b
and the wafer W do not interfere. Moreover, for example when the wafer W is received by the unload arm
413
, it is necessary to move the unload arm
413
from a standby position A as far as a transfer position B. Therefore there is a problem of a drop in throughput of wafer W transport or processing, attributable to the time requirement for movement during this interval.
[Second Background Art]
Furthermore, at the time of manufacturing semiconductor devices or the like, for the exposure apparatus for transferring a pattern of a reticle serving as a mask onto each shot region of a wafer (or glass plate etc.) to which photoresist has been applied, conventionally a projection exposure apparatus of the step-and-scan type (block exposure type, or stepper type) is widely used. On the other hand, recently, in order to respond to the demand for precise transfer of large area circuit patterns, without making the burden on the projection optical system too heavy, attention is also being given to projection exposure apparatus of the scanning exposure type such as the so called step-and-scan type. According to such apparatus, step movement is carried out between shots, and at the time of performing exposure to each shot region, the reticle and the wafer are moved simultaneously with respect to the projection optical system.
With these projection exposure apparatus, in order to increase throughput, a wafer loading operation for unloading a wafer which has already been exposed on a wafer stage used for positioning and moving the wafer, and also loading an unexposed wafer onto the wafer stage, must be carried out at high speed.
A conventional wafer loader system comprises; wafer lift pins projectably provided in a wafer holder of the wafer stage, a wafer load arm for mounting the wafer on the wafer lift pins, and a wafer unload arm for removing the wafer from the wafer lift pins. Furthermore, as disclosed for example in Japanese Patent Application, First Publication, No. 9-36202, when the wafer is mounted on the wafer stage, rough alignment (prealignment) based on the external shape of the wafer is performed beforehand at the stage where the wafer is transferred from the wafer transport line to the wafer load arm.
Moreover, in order to perform wafer exchange, the wafer stage is moved to a loading position, and attraction of the exposed wafer on the wafer holder is switched off. After this, the wafer is raised together with the wafer lift pins, and then the wafer unload arm is inserted between the wafer and the wafer holder, and the wafer lift pins lowered so that the wafer is transferred to the wafer unload arm.
After this, the wafer unload arm is taken out from the loading position to the wafer transport line side, and at the same time, a wafer load arm holding an unexposed wafer is inserted into the loading position, and the wafer lift pins are raised so that the wafer is transferred onto the wafer lift pins. Then, after the wafer load arm is withdrawn, the wafer lift pins are lowered so that the wafer is mounted on the wafer holder. After this, attraction by the wafer holder is switched on. The wafer stage is then sequentially moved to positions where search alignment marks on the wafer are within detection regions of an alignment sensor, and search alignment is performed.
Moreover, in the search alignment process, for example, by detecting the position of three one dimensional search alignment marks on the wafer, the positional displacement amount and the rotation angle deviation amount of the origin of the shot array on the wafer is detected, and based on these results, the actual rough array coordinates for each shot region on the wafer are obtained. After this, the final alignment (fine alignment) is executed for example by an EGA (Enhanced Global Alignment) method. This involves detecting based on the rough array coordinates, the position of fine alignment marks (wafer marks) attached to a predetermined number of shot regions (sample shots) determined beforehand on the wafer by an alignment sensor. Then based on this result, the pattern images of the reticle in each shot region of the wafer are precisely overlapped and exposed, after which the abovementioned wafer exchange is again performed.
In the conventional technology as described above, the wafer lift pins are protrudably mounted in the wafer holder on the wafer stage, and by raising these wafer lift pins, transfer of the wafer is performed between the wafer holder and the wafer load arm or the wafer unload arm.
However, in the construction where the wafer lift pins are provided inside the wafer holder, the mechanism for the wafer stage for supporting the wafer holder becomes complicated, and there is the disadvantage of the increase in size. In particular, in order to increase throughput, it is necessary to increase stepping speed in a one-shot exposure type, or stepping traversing speed and scanning speed in a scanning exposure type. However, in the case of enlargement of the drive motor, there is the possibility of an increase in vibration and generated heat. Therefore, in situations where the wafer stage cannot be made small, it is difficult to raise the traversing speed while suppressing heat output and the like.
Furthermore, the conventional processing time for one wafer is determined from the sum of; the wafer exchange time, the search alignment time, the fine alignment time, and the
Kida Yoshiki
Nishi Kenji
Fuller Rodney
Nikon Corporation
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