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Patent Issued for Lithographic Apparatus, a Method for Removing Material of One Or More Protrusions on a Support Surface, and an Article Support...

September 3, 2014



Patent Issued for Lithographic Apparatus, a Method for Removing Material of One Or More Protrusions on a Support Surface, and an Article Support System

By a News Reporter-Staff News Editor at Journal of Engineering -- ASML Netherlands B.V. (Veldhoven, NL) has been issued patent number 8810777, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Cadee, Theodorus Petrus Maria (Vlierden, NL); Gilissen, Noud Jan ('s-Gravenzande, NL); Compen, Rene Theodorus Petrus (Valkenswaard, NL); Kennon, James (Benicia, CA).

This patent was filed on February 3, 2010 and was published online on August 19, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the 'scanning'-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

"The substrate support tables used in lithography have a support surface with protrusions that extend substantially perpendicularly from the surface. In operation, the backside of the substrate is supported on the protrusions, at a small distance from the support surface of the substrate table, in a position substantially perpendicular to the direction of propagation of the projection beam. Thus, the tops of the protrusions, rather than the support surface of the wafer table, define an effective support surface for the substrate.

"In order to avoid overlay errors during projection of patterned beam of radiation on a substrate, it is desirable that the substrate top surface be flat. Unevenness of the supporting surface of the substrate support may lead to an uneven top surface of the substrate supported on the support surface. Therefore, it is desirable to avoid unevenness in the substrate support.

"Unevenness of the supporting surface can be caused by dissimilarity between the heights of material that makes up the protrusion itself. This is typically the case when a new substrate support table has been manufactured. Possibly uneven wear may also lead to unevenness. In a known embodiment, the substrate support table contains a chuck on which the table with the protrusions is supported. In an alternative embodiment the chuck and substrate support table may be integrated in a single unit. Unevenness may be the result of differences between the heights of the protrusions, or in the backside of the table or in the chuck. Therefore these elements are carefully made level. Nevertheless it has been found that unevenness may also result when the chuck and the support table (and any other elements) are assembled or installed. Similar problems may be encountered with support tables for other articles that have to be supported in a well-defined plane across the beam path, such as reflective patterning devices or transmission patterning devices

"US 2005/0061995 A1, the contents of which is herein incorporated by reference in its entirety, provides a lithographic projection apparatus including a detector to detect height deviations of the protrusions that affect a surface flatness of the article, a height adjustment device arranged to independently modify a height of the protrusion material of individual protrusions when the support table is operable in the apparatus, and a controller coupled between the detector and the height adjustment device and arranged to control the height adjustment device to adjust the height of the protrusions corresponding to the detected height deviations of the protrusions that affect the surface flatness of the article.

"An in situ height adjustment device is used to alter the height of the material that at least the top of individual protrusions are integrally made of, when the support table is at an operable position in the lithographic projection apparatus. By 'operable,' it is meant that the support table may be moved to a pattern projection position in the apparatus from the operable position without movements that are more disruptive to the support table assembly than during normal use. 'Integrally made' refers to material that is used to manufacture the support table or coatings or other material layers on the protrusions, but not to accidental foreign material such as pollution. By adjusting the height of the protrusions in the assembled support table in the lithographic apparatus, at such an operable position, a reliable local and global height adjustment may be realized.

"A detector determines which of the protrusions have a height deviation and a control unit controls the height adjustment device, for example, to remove a part of the material of selected protrusions with excess height, but not from other protrusions that do not have an excess height, or an excess height below a threshold."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "It is desirable for cost of ownership, cost of goods and/or quality of overlay to provide an improved height adjustment device for in situ use in a lithographic apparatus, or at least an alternative therefor. Furthermore, it is desirable to provide a method for use of such improved or alternative height adjustment device.

"According to an embodiment of the invention, there is provided a lithographic projection apparatus including: a beam production system configured to provide a beam of radiation, patterning the beam of radiation, and projecting the patterned beam onto a target portion of a substrate; a support table configured to support an article so that a surface of the article lies in a predetermined plane in relation to a propagation direction of the projection beam, the support table having a support surface and an array of protrusions extending from the support surface to support the article on the protrusions, at least a top of each protrusion being substantially formed of an integral protrusion material; a detector configured to detect height deviations of the protrusions that affect a surface flatness of an article supported on the support table; a material removing device arranged to modify a height of the protrusion material of one or more protrusions when the support table is operable in the apparatus; and a controller coupled between the detector and the material removing device and arranged to control the material removing device to adjust the height of the protrusions corresponding to the detected height deviations of the protrusions that affect the surface flatness of the article, wherein the material removing device includes a removal tool selected from the group consisting of a mechanical polishing device, a magneto rheological finishing tool, and a single or multipoint diamond tool.

"According to an embodiment of the invention, there is provided a method for removing material of one or more protrusions on a support surface of a support table for holding an article with a surface in a predetermined plane in relation to a projection path in a lithographic projection apparatus, the support table including a support surface with an array of protrusions, each of which includes a top that is integrally made of protrusion material, the protrusions extending from the support surface for supporting the article, the method including: measuring height deviations of the protrusions that affect a surface flatness of the planar surface of the article when the surface element is mounted on the support table; and adjusting a height of the protrusion material by removing material of one or more protrusions corresponding to the detected height deviations of the protrusions, wherein the measuring and the adjusting are executed while the support table is in an operable position in the lithographic projection apparatus, and wherein the removing is carried out by using a removal tool selected from the group consisting of a mechanical polishing device, a magneto rheological finishing tool, and a single or multipoint diamond tool.

"According to an embodiment of the invention, there is provided an article support system for use in a lithographic apparatus, the support system including: a support table configured to support an article so that a surface of the article lies in a predetermined plane in relation to a propagation direction of the projection beam, the support table having a support surface and an array of protrusions extending from the support surface to support the article on the protrusions, at least a top of each protrusion being substantially formed of an integral protrusion material; a detector configured to detect height deviations of the protrusions that affect a surface flatness of an article supported on the support table; a material removing device arranged to modify a height of the protrusion material of one or more protrusions when the support table is operable in the apparatus; a controller coupled between the detector and the height adjustment device and arranged to control the height adjustment device to adjust the height of the protrusions corresponding to the detected height deviations of the protrusions that affect the surface flatness of the article, wherein the material removing device includes a removal tool selected from the group consisting of a mechanical polishing device, a magneto rheological finishing tool, and a single or multipoint diamond tool."

For the URL and additional information on this patent, see: Cadee, Theodorus Petrus Maria; Gilissen, Noud Jan; Compen, Rene Theodorus Petrus; Kennon, James. Lithographic Apparatus, a Method for Removing Material of One Or More Protrusions on a Support Surface, and an Article Support System. U.S. Patent Number 8810777, filed February 3, 2010, and published online on August 19, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8810777.PN.&OS=PN/8810777RS=PN/8810777

Keywords for this news article include: ASML Netherlands B.V.

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Source: Journal of Engineering


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