Electricity: electrical systems and devices – Electric charge generating or conducting means – Use of forces of electric charge or field
Reexamination Certificate
2000-10-04
2002-11-12
Berhane, Adolf Deneke (Department: 2838)
Electricity: electrical systems and devices
Electric charge generating or conducting means
Use of forces of electric charge or field
Reexamination Certificate
active
06480369
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This invention claims priority of a German filed patent application DE P 198 53 092.7.
FIELD OF THE INVENTION
The invention relates to a receiving and supporting system for a substrate in an exposure system, which is supplied with an electro-statical chuck arrangement movable in X, Y coordinates to support the substrate on a bearing surface during exposure.
BACKGROUND OF THE INVENTION
Supporting systems for the reception of substrates, especially of masks and wafers, during the time of exposure, are known in various models according to the state of art.
As a rule, those supporting systems are arranged on a table, movable in two coordinates X, Y, having a bearing area for the substrate, on which the substrate is laid prior to the exposure process and where it is held while the table step by step is moved into direction X and/or Y and where the substrate in succession is brought into the desired position of exposure.
In most cases, the bearing levels are formed with high-plane bearing surfaces, possibly also with several punctiform bearing elements.
The basic bodies, mounting plate, etc., on which the bearing elements are positioned or bearing surfaces are formed, are in most cases mechanically affixed to the table via metering means for the positioning of the substrate in Z coordinate. The Z coordinate thereby corresponds to the exposure direction of the exposure beam-path, directed right-angled onto the substrate's surface.
The sensitive handling of the substrate during the receiving phase into the exposure system, and the precision during the positioning of the substrate surface relative to the exposure system are substantial criterion in regard to the quality and sensitivity of structure during exposure and increasing importance, as far as future attempts of the micro-electronic industry for the reduction of structure dimensions are concerned.
Since the substrate itself is not stable against deformations, the main problems with these versions of supporting systems appear in the precision of the positioning for the substrate, even in case of temperature-or pressure variations, as well as in the dimensional shape of the substrate support.
Therefore it has to be taken into account, that no mechanical force, regardless what origin, is influencing the substrate, which would lead to deformations and therefore unacceptable deviations in structure.
Furthermore, for the construction of supporting systems it has to be considered, that the direction of the exposure beam is not unintentionally influenced by magnetic fields and/or electric power charges. Above all, the manufacturing of supporting systems must be kept within economically reasonable limits.
In consideration of these high requirements, the supporting systems according to the state of art need to be evaluated.
The U.S. Pat. No. 5,535,090 and the publication “Semiconductor International”, Sherman, Vol. 20, No. 8, p. 319-322 for example announce a decive, with electro-static chuck arrangement for the support of substrates during exposure. The chuck arrangement shows a conductive layer, which can be applied to the substrate via electrical supply contacts with electrical switch-off potentials. In case of potential application, an electro-static field develops, by means of which the substrate is held on a plane insulation layer, positioned above the conductive layer. In this case, the extent of the force of attraction between the chuck arrangement and the substrate is dependant upon the electrical voltage applied, the size of the conductive layer, (the so called chuck electrode), and the thickness of the insulation layer, located between the conductive layer and the substrate.
To avoid unintentional influence of the exposure beam path, appropriate measures have to be taken to prevent electro-static charging at unwanted locations of the supporting system or the exposure system, when applying electro-static chuck arrangements in exposure systems.
An appropriate measure is for example the use of non-magnetic materials. This is achieved in the described arrangement of the mentioned publication by using sapphire material.
Sapphire admittedly is non-magnetic, however the costs for purchase are extremely high and consequently the technological costs for the production of the plane bearing surface for the substrate are immense. Therefore, in the arrangement mentioned above, the 8″ sized bearing surface has not completely been covered with sapphire material, but several 2″ sized sapphire plates have been arranged via an intermediate layer of Niob. Disadvantageous in this case is the technologically elaborate manufacturing procedure for a multi-layer bearing surface.
In addition to this, the uniformity of the material, carrying the substrate, is not guaranteed, resulting in a non-uniformity of the supporting power as far as the entire bearing surface is concerned.
The U.S. Pat. No. 5,600,530 also describes a supporting device for substrates, where once again an electro-static chuck arrangement is provided. In this case, however, the material used for the insulation layer of the chuck arrangement is aluminium oxide, and the invention furthermore describes a procedure, in which the thick aluminium oxide layer is thinned down to the appropriate thickness. Due to its unfavourable properties in temperature-fluctuations, the use of aluminium oxide leads to detrimental problems. For the compensation of this disadvantage, the use of aluminium oxide to manage a high exposure accuracy leads to extensive measures in order to avoid positioning errors and/or deformations of the substrate on the aluminium oxide layer. A solution for this problem, resulting from the use of aluminium oxide, however, is no described in the mentioned patent.
Another substrate receiving device for treatment in an electron-beam-system is disclosed in U.S. Pat. No. 5,644,137. The arrangement described here, is equipped with interferometers for the positioning and observation of the table and so of the substrate during the movement in X, Y coordinates. A stabilisation of the substrate's position relative to the exposure system is reached, as some parts of the supporting system and the interferometer mirrors are manufactured from material of equal expansion-behaviour, resulting in a higher positioning precision in the directions X and Y.
Unfortunately, this patent does not mention any means and measures to solve the problem of material expansion in direction to coordinate Z, or the imprecision resulting from this.
Another disadvantage in the publications mentioned above, is the fact that the supporting systems do not provide technical feeding devices that enable the receiving of the substrate via e.g. a robot arm and its sensitive and exact positioning on the deposit area.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to develop supporting systems in the abovementioned style with further improvements to facilitate a precise receiving from a handling system and a better positioning and shape stability during the exposure.
For a receiving and supporting unit of the abovementioned style, this task is solved through the characterizing features of claim 1. Further advantageous improvements are indicated in features of the sub-claims.
The receiving and supporting unit of the abovementioned style provides at least a second electrostatic chuck arrangement, which—similar to the first electro static chuck arrangement, that supports the substrate during exposure,—provides a bearing surface for the substrate, whereby the bearing surface of the first chuck arrangement und the bearing surface of the second chuck arrangement mutually form a bearing surface for the substrate, and whereby the bearing surface of the second chuck arrangement is positioned in Z direction, that is to say in the direction of the exposure light beam-path , relatively moveable to the bearing surface of the first chuck arrangement.
In regard to their holding force, both chuck arrangements are designed to support the substrate in a save
Damm Christoph
Kirschstein Ulf-Carsten
Peschel Thomas
Risse Stefan
Berhane Adolf Deneke
Foley & Lardner
Leica Microststems Lithography GmbH
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