Photocopying – Projection printing and copying cameras – Detailed holder for original
Reexamination Certificate
2000-04-19
2002-07-02
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Detailed holder for original
C355S076000, C414S935000, C414S941000
Reexamination Certificate
active
06414744
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a mask-handling apparatus used in lithographic projection apparatus for imaging of a mask pattern in a mask onto a substrate.
More particularly it relates to a mask-handling apparatus having a load-port module constructed to receive masks, the mask-handling apparatus being constructed and arranged to exchange a mask between the load-port module and the mask holder.
BACKGROUND OF THE INVENTION
A lithographic projection apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, the mask (reticle) may contain a circuit pattern corresponding to an individual layer of the IC, and this pattern can then be imaged onto a target area (die) on a substrate (silicon wafer) which has been coated with a layer of photosensitive material (resist). In general, a single wafer will contain a whole network of adjacent dies which are successively irradiated through the reticle, one at a time. In one type of lithographic projection apparatus, each die is irradiated by exposing the entire reticle pattern onto the die at once; such an apparatus is commonly referred to as a waferstepper. In an alternative apparatus—which is commonly referred to as a step-and-scan apparatus—each die is irradiated by progressively scanning the reticle pattern under the projection beam in a given reference direction (the “scanning” direction) while synchronously scanning the wafer table parallel or anti-parallel to this direction; since, in general, the projection system will have a magnification factor M (generally<1), the speed v at which the wafer table is scanned will be a factor M times that at which the reticle table is scanned. More information with regard to lithographic devices as here described can be gleaned from International Patent Application WO 97/33205.
Lithographic apparatus may employ various types of projection radiation, such as ultraviolet (UV) radiation, extreme UV (EUV) radiation, X-rays, ion beams or electron beams, for example. Depending on the type of radiation used and the particular design requirements of the apparatus, the projection system may be refractive, reflective or catadioptric, for example, and may comprise vitreous components, grazing-incidence mirrors, selective multi-layer coatings, magnetic and/or electrostatic field lenses, etc; for simplicity, such components may be loosely referred to in this text, either singly or collectively, as a “lens”.
Up to very recently, apparatus of this type contained a single mask table and a single substrate table. However, machines are now becoming available in which there are at least two independently movable substrate tables; see, for example, the multi-stage apparatus described in International Patent Applications WO 98/28665 and WO 98/40791. The basic operating principle behind such multi-stage apparatus is that, while a first substrate table is underneath the projection system so as to allow exposure of a first substrate located on that table, a second substrate table can run to a loading position, discharge an exposed substrate, pick up a new substrate, perform some initial alignment measurements on the new substrate, and then stand by to transfer this new substrate to the exposure position underneath the projection system as soon as exposure of the first substrate is completed, whence the cycle repeats itself; in this manner, it is possible to achieve a substantially increased machine throughput, which in turn improves the cost of ownership of the machine. The apparatus may also have more than one mask table and may comprise components which are operated in vacuum, and are correspondingly vacuum-compatible.
A mask present on the mask table will be exchanged for another one when another mask pattern is required for imaging. The latter mask has to be discharged from the mask table and another mask has to be taken from some location and loaded on the mask table. The exchange process may take some time, which will result in a decreased throughput of the lithographic projection apparatus.
An object of the present invention is to provide a mask handler in a lithographic projection apparatus that enables a very short reticle exchange process to yield an improved throughput of substrates and therefore an improved cost of ownership of the apparatus.
SUMMARY OF THE INVENTION
According to the present invention there is provided a lithographic projection apparatus for imaging of a mask pattern in a mask onto a substrate, said apparatus comprising:
an illumination system constructed and arranged to supply a projection beam of radiation;
a mask table provided with a mask holder constructed to hold a mask;
a substrate table provided with a substrate holder constructed to hold a substrate;
a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate; and
a mask-handling apparatus comprising a load-port module constructed to receive masks, the mask-handling apparatus being constructed and arranged to exchange a mask between the load-port module and the mask holder, characterized in that
the mask-handling apparatus further comprises a first robot and a second robot, the first robot being constructed and arranged to exchange a mask between the load-port module and the second robot, and the second robot being constructed and arranged to exchange a mask between the first robot and the mask holder.
The first and second robots allow for a concurrent exchange of a mask at the load-port module and of a mask at the mask table, and the configuration may be designed such that the first robot presents a new mask to the second robot at the moment a mask should be interchanged on the mask table for another one. Both robots may be designed for their specific tasks in a mask-handling sequence, the second robot being constructed such that the actual transfer to the mask holder of the mask table takes place very fast and efficiently.
An embodiment of such a second robot is provided with two mask holding arrangements, which allows placement of a new mask in one of the mask holding arrangements before or during unloading of a mask from the mask table in another one of the mask holding arrangements. Removal of the unloaded mask and supply of the new mask may then take place in one quick action. Preferably, the second robot is rotatable, for instance like a carousel, for a very quick and efficient transfer of the new mask to the mask table by a simple rotation.
In a further embodiment each mask holding arrangement of the second robot comprises an elevator constructed to exchange a mask between the second robot and the mask holder, and the elevators may be provided with vacuum-operated end-effectors constructed to hold a mask at its top side.
The load-port module, the robots and the mask holder may be understood as mask stations that are constructed to receive a mask. In yet a further embodiment, the mask-handling apparatus comprises one or more further mask stations constructed to receive a mask, the first robot being constructed and arranged to exchange a mask between one of the load-port module, the second robot and the further mask station or stations and another one of the load-port module, the second robot and the further mask station or stations. The further mask station or stations may comprise a mask library constructed and arranged to store one or more masks, and/or a mask inspection station constructed and arranged to check a mask for contamination. Such further mask stations improve the functionality of the mask handler, and the two-robot configuration allows the first robot to be constructed such as to be able to exchange a mask between the various stations while the actual exchange of masks at the mask table may still take place very fast.
A conveniently constructed first robot has an arm-like configuration provided with three rotary joints such as to allow movement in a plane. Such a configuration allows mask to be exchanged readily between various mask stations positioned such that they may be accessed in
Kuiper Doede
Kuit Jan J.
Adams Russell
Asml Netherlands B.V.
Fuller Rodney
Pillsbury & Winthrop LLP
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