Source: http://www.google.com/patents/USRE41307?dq=7,194,691
Timestamp: 2017-12-16 19:19:03
Document Index: 716282764

Matched Legal Cases: ['arts 12', 'arts 12', 'arts 12', 'arts 12', 'arts 12', 'Application No. 2000', 'Application No. 00310188', 'Application No. 2000']

Patent USRE41307 - Mask for clamping apparatus, e.g. for a lithographic apparatus - Google Patents
An apparatus for supporting a mask comprises a pair of members. The mask held against each member by a vacuum arrangement which prevents relative motion between the mask and members. The members are compliant such that they accommodate flatness variations in the mask but without deforming the mask....http://www.google.com/patents/USRE41307?utm_source=gb-gplus-sharePatent USRE41307 - Mask for clamping apparatus, e.g. for a lithographic apparatus
Publication number USRE41307 E1
Application number US 11/050,624
Also published as DE60036844D1, DE60036844T2, EP1107066A2, EP1107066A3, EP1107066B1, US6480260
Publication number 050624, 11050624, US RE41307 E1, US RE41307E1, US-E1-RE41307, USRE41307 E1, USRE41307E1
Inventors Sjoerd N .L. Donders, Tjarko A. R. van Empel
Patent Citations (15), Non-Patent Citations (6), Referenced by (2), Classifications (18), Legal Events (2)
Mask for clamping apparatus, e.g. for a lithographic apparatus
US RE41307 E1
An apparatus for supporting a mask comprises a pair of members. The mask held against each member by a vacuum arrangement which prevents relative motion between the mask and members. The members are compliant such that they accommodate flatness variations in the mask but without deforming the mask.
1. A lithographic projection apparatus for imaging of a mask pattern in a mask onto a substrate provided with a radiation-sensitive layer, the apparatus comprising:
a first object table for holding a mask having a stiffness;
a projection system constructed and arranged to image irradiated portions of the mask onto target portions of the substrate;
said mask table first object table including at least one compliant member constructed and arranged to hold said mask such that, when the mask is held by said at least one compliant member, said at least one compliant member yields under the weight of the mask to conform substantially to a profile of the mask, and supports substantially the entire weight of the mask without a support, under a point of contact between the mask and the compliant member, to support substantially the entire weight of the mask, wherein a portion of said at least one compliant member is in direct contact with said mask and said portion has a stiffness lower than the stiffness of the mask.
2. An apparatus according to claim 1, wherein said at least one member comprises a pair of parallel strips.
7. An apparatus according to claim 1, further comprising a plurality of supports defining constructed and arranged to define a position of said mask perpendicular to its plane.
9. An apparatus according to claim 5, wherein said at least one support member comprises a duct in communication with said vacuum space, said duct being constructed and arranged to evacuate said vacuum space.
12. An apparatus according to claim 7, comprising four supports, wherein each support is arranged to support said mask proximate a respective one of its corners.
13. An apparatus according to claim 12, wherein three of said supports are fixed and a fourth one of said supports is movable perpendicular to the plane of the mask and is arranged to provide a desired supporting force.
18. An apparatus according to claim 17, further comprising a vacuum chamber in a table supporting said at least one member, said vacuum chamber being constructed and arranged to deform said member.
19. An apparatus according to claim 17, wherein said at least one member is pre-stressed.
20. An apparatus according to claim 17, wherein said at least one member is made of one or more materials selected from: metal, silica, CaF2, MgF2, BaF2, Al2O3 and Zerodur ceramic.
providing a substrate provided with a radiation-sensitive layer to a second object table; and
irradiating portions of the mask and imaging irradiated portions of the mask onto target portions of said substrate; and
holding said mask, during operation, on said first object table with the aid of at least one compliant member such that said at least one compliant member yields under the weight of the mask to conform substantially to the profile of the mask and supports substantially the entire weight of the mask without a support, under a point of contact between the mask and the compliant member, to support substantially the entire weight of the mask, wherein a portion of said at least one compliant member is in direct contact with said mask and said portion has a stiffness lower than the stiffness of the mask.
26. A mask table comprising at least one compliant member for holding a mask such that, when the mask is held by said at least one compliant member, said at least one compliant member yields under the weight of the mask to conform substantially to the profile of the mask and supports substantially the entire weight of the mask without a support, under a point of contact between the mask and the compliant member, to support substantially the entire weight of the mask, wherein a portion of said at least one compliant member is in direct contact with said mask and said portion has a stiffness lower than the stiffness of the mask.
27. An apparatus according to claim 17, wherein the membrane supports substantially the entire weight of the mask when the mask is held by said at least one member.
28. A method according to claim 24, wherein said at least one compliant member is a membrane.
29. A method according to claim 28, wherein the membrane supports substantially the entire weight of the mask when the mask is held with the aid of said at least one member.
30. A method according to claim 24, wherein said at least one member comprises a pair of parallel strips.
31. A method according to claim 24, further comprising a plurality of supports constructed and arranged to define a position of said mask perpendicular to its plane.
32. A method according to claim 24, wherein said at least one member is arranged to exert a torsional force on said mask for compensating against gravitational sagging of said mask.
33. A mask table according to claim 26, further comprising a plurality of supports constructed and arranged to define a position of said mask perpendicular to its plane.
34. A mask table according to claim 26, wherein said at least one compliant member comprises a membrane.
35. A mask table according to claim 34, wherein the membrane supports substantially the entire weight of the mask when the mask is held by said at least one member.
For the sake of simplicity, the projection system may hereinafter be referred to as the “lens”; however, this term should be broadly interpreted as encompassing various types of projection system, including refractive optics, reflective optics, catadioptric systems, and charged particle optics, for example. The radiation system may also include elements operating according to any of these principles for directing, shaping or controlling the projection beam of radiation, and such elements may also be referred to below, collectively or singularly, as a “lens”. In addition, the first and second object tables may be referred to as the “mask table” and the “substrate table”, respectively. Further, the lithographic apparatus may be of a type having two or more mask tables and/or two or more substrate tables. In such “multiple table” devices the additional tables may be used in parallel, or preparatory steps may be carried out on one or more stages while one or more other stages are being used for exposures. Twin stage lithographic apparatus are described in International Patent Applications WO 98/28665 and WO 98/40791, for example.
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 be imaged onto a target portion (comprising one or more dies) 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 target portions which are successively irradiated via the mask, one at a time. In one type of lithographic projection apparatus, each target portion is irradiated by exposing the entire mask pattern onto the target portion at once; such an apparatus is commonly referred to as a wafer stepper. In an alternative apparatus—which is commonly referred to as a step-and-scan apparatus—each target portion is irradiated by progressively scanning the mask pattern under the projection beam in a given reference direction (the “scanning” direction) while synchronously scanning the substrate 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 substrate table is scanned will be a factor M times that at which the mask table is scanned. More information with regard to lithographic devices are here described can be gleaned from International Patent Application WO 97/33205.
In the above apparatus, the mask must be securely held (“clamped”) so that it can be accurately positioned in the x, y and z direction and in rotational orientation about the x, y and z axes (referred to as the Rx, Ry and Rz directions). The z direction is defined as being the direction along an axis which is substantially parallel to the optical axis of the projection system, and the x and y directions are along axes which are substantially perpendicular to the z axis and to each other. The mask can be subjected to large accelerations in its plane (the xy plane), particularly in a step-and-scan apparatus where the acceleration can be around 5 g (where g is the gravitational acceleration). In the z direction, the mask can be positioned with a 100 Hz bandwidth actuator which requires a relatively high stiffness in the z direction. The mask clamping arrangement must be sufficiently secure to withstand such accelerations and also to provide the mask with the necessary stiffness in the xy plane.
Preferably the or each member is made of one or more materials selected from metal, silica (SiOx), CaF2, MgF2, BaF2, Al2O3 and Zerodur® (trademark) ceramic. Most of these materials can enable the member to be made of the same material as the mask. This has the advantage that the mask and member can then have the same mechanical properties, such as coefficient of thermal expansion, and, therefore, further reduces distortion and creep.
In a manufacturing process using a lithographic projection apparatus according to the invention a pattern in a mask is imaged onto a substrate which is at least partially covered by a layer of energy-sensitive material (resist). Prior to this imaging step, the substrate may undergo various procedures, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other procedures, such as a post-exposure bake (PEB), development, a hard brake and measurement/inspection of the imaged features. This array of procedures is used as a basis to pattern an individual layer of a device, e.g. an IC. Such a patterned layer may then undergo various processes such as etching, ion-implantation (doping), metallisation, oxidation, chemo-mechanical polishing, etc., all intended to finish off an individual layer. If several layers are required, then the whole procedure, or a variant thereof, will have to be repeated for each new layer. Eventually, an array of devices will be present on the substrate (wafer). These devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc. Further information regarding such processes can be obtained, for example, from the book “Microchip Fabrication: A Practical Guide to Semiconductor Processing”, Third Edition, by Peter van Zant, McGraw Hill Publishing Co., 1997, ISBN 0-07-067250-4.
Although specific reference may be made in this text to the use of the apparatus according to the invention in the manufacture of ICs, it should be explicitly understood that such an apparatus has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic beads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle”, “wafer” or “die” in this text should be considered as being replaced by the more general terms “mask”, “substrate” and “target portion”, respectively.
In the present document, the terms illumination radiation and illumination beam are used to encompass all types of electromagnetic radiation or particle flux, including, but not limited to, ultraviolet radiation (e.g. with a wavelength of 365, 248, 193, 257 or 126 nm), EUV, X-rays, electrons and ions.
a first object table (mask table) MT for holding a mask MA (e.g., a mask), and connected to first positioning means for accurately positioning the mask with respect to item PL;
The radiation system comprises a source LA (e.g. a Hg lamp, excimer laser, an undulator provided around the path of an electron beam in a storage ring or synchrotron, or an electron or ion beam source) which produces a beam of radiation. This beam is caused to traverse various optical components comprised in the illumination system,—e.g. beam shaping optics Ex, an integrator IN and a condenser CO—so that the resultant beam PB has a desired shape and intensity distribution in its cross-section.
FIGS. 2 and 3 illustrate two arrangements for supporting a mask (reticle) 10 on parts 12 of the mask table by means of a pair of members 14. In FIG. 2, two opposite edges of the reticle 10 are supported on portions of the members 14 which are cantilevered from the edges of the opposing parts 12 of the mask table; in the case of a transmissive mask, as here, a space is provided between the parts 12, enabling the projection beam to traverse the mask table. Alternatively, as shown in FIG. 3, the reticle can be supported on a pair of parallel members 14 which are each supported on parts 12 at each of their ends. The arrangement of FIG. 2 is generally preferred because the strip-shaped members 14 are supported on parts 12 along their length in the y direction, and therefore have a higher stiffness to reduce sagging of the reticle. In case of a reflective mask, it is preferred to employ a membrane which supports said reflective mask (almost) completely. In all cases the members are compliant such that they yield to the shape of the reticle 10 without deforming it by force to adopt a particular configuration.
In the illustrated embodiments, the members 14 may be made of the same material as the reticle, such as silica, CaF2, MgF2, BaF2, Al2O3 and Zerodur® ceramic, for example. However, other possibilities are contemplated, such as supporting the reticle on baths of gel, for example, or making the member (partly) out of metal.
By “vacuum” a reduced gas pressure is of course meant, such as 5.5×104 Pa for example, such that the excess external pressure provides a normal force holding the reticle 10 and the member 14 against each other. Relative motion between the reticle 10 and member 14 in the xy plane is impeded by the friction between the two components, which is increased by the normal force. The coefficient of friction between the member and reticle can, of course, be selected by the choice of material for and/or the roughness of the contact surfaces.
All mask clamping arrangements described above are suitable for holding a mask in such a way as to avoid exerting a force on the mask sufficient to substantially deform it. Generally, however, masks may be deformed intrinsically and, consequently, may deviate substantially in shape from a flat plane; examples of such deviations are wedge-like, parabolic, saddle-shaped and cork-screw-like deformations, etc. Such deformations at mask level will generally lead to undesirable focal plane deviations at wafer level. In a step-andscan apparatus the position of said mask may generally be adjustable (in three degrees of freedom: z, Rx, Ry) during a scan in order to minimize or completely remove the said focal plane deviations. To this end, one or more actuators—which are located so as to enable movement of the mask table and therefore the mask in the z, Rx or Ry directions—are selectively and independently moved. In order to establish the positional correction needed, a “height map” of the mask pattern may be determined. Said height map can be determined by determining the focal plane form/position at wafer level. Said focal plane form/position can be determined either using a technique such as “FOCAL” or, alternatively, one may directly measure the aerial image, e.g. using a Transmission Image Sensor (TIS). Both methods will be described below.
One or more transmission image sensor(s) (TIS) can be used to determine the lateral position and best focus position (i.e. vertical and horizontal position) of the projected image from the mask under the projection lens. A transmission image sensor (TIS) is inset into a physical reference surface associated with the substrate table (WT). In a particular embodiment, two sensors are mounted on a fiducial plate mounted to the top surface of the substrate table (WT), at diagonally opposite positions outside the area covered by the wafer W. The fiducial plate is made of a highly stable material with a very low coefficient of thermal expansion, e.g. Invar, and has a flat reflective upper surface which may carry markers used with another fiducial in alignment processes. The TIS is used to determine directly the vertical (and horizontal) position of the aerial image of the projection lens. It comprises apertures in the respective surface close behind which is placed a photodetector sensitive to the radiation used for the exposure process. To determine the position of the focal plane, the projection lens projects into space an image of a pattern provided on the mask MA and having contrasting light and dark regions. The substrate stage is then scanned horizontally (in one or preferably two directions) and vertically so that the aperture of the TIS passes through the space where the aerial image is expected to be. As the TIS aperture passes through the light and dark portions of the image of the TIS pattern, the output of the photodetector will fluctuate (a Moiré effect). The vertical level at which the rate of change of amplitude of the photodetector output is highest indicates the level at which the image of TIS pattern has the greatest contrast and hence indicates the plane of optimum focus. The horizontal level at which the rate of change is highest indicates the aerial image's lateral position. An example of a TIS of this type is described in greater detail in U.S. Pat. No. 4,540,277. Advantages of TIS include robustness and speed because it is a direct measurement technique not involving exposure of a resist.
US4549843 Mar 15, 1983 Oct 29, 1985 Micronix Partners Mask loading apparatus, method and cassette
US4716299 Jan 23, 1986 Dec 29, 1987 Nippon Kogaku K. K. Apparatus for conveying and inspecting a substrate
US4986007 Mar 25, 1987 Jan 22, 1991 Svg Lithography Systems, Inc. Reticle frame assembly
US6118515 May 9, 1996 Sep 12, 2000 Nikon Corporation Scanning exposure method
JPH1097967A Title not available
JPH07136885A Title not available
JPH07192984A Title not available
JPH08167553A Title not available
JPS6480036A Title not available
1 * English Translation (Formal) of JP 7-192984 (dated Jul. 28, 1995).
2 English translation of Japanese Office Action issued in Japanese Patent Application No. 2000-359637 dated Apr. 25, 2006.
3 * English Translation of JP 7-136885 (dated May 30, 1995).
4 * English Translation of JP 7-192984 (dated Jul. 28, 1995).
5 European Office Action issued for European Patent Application No. 00310188.8-1226, dated May 18, 2007.
6 Japanese Office Action issued in Japanese Patent Application No. 2000-359637 mailed Oct. 17, 2006.
US9070535 * Jun 25, 2013 Jun 30, 2015 Varian Semiconductor Equipment Associates, Inc. Proximity mask for ion implantation with improved resistance to thermal deformation
US20140374626 * Jun 25, 2013 Dec 25, 2014 Varian Semiconductor Equipment Associates, Inc. Proximity mask for ion implantation
U.S. Classification 355/53, 355/73, 430/311, 355/72, 250/492.22, 355/76, 355/74, 355/75, 355/77
International Classification G03F7/20, H01L21/027, G03B27/60, G03B27/58, G03B27/42, A61N5/00, G03C5/00