TW202412096A - Apparatus for and method of in situ clamp surface roughening - Google Patents

Abstract

Disclosed is a dedicated roughening substrate provided with abrasive element useful for in situ roughening of a surface of a clamp in a semiconductor photolithography apparatus. Also disclosed is a method of using the roughening substrate in which the roughening substrate is loaded, positioned opposite the clamp, and then pressed against the clamp and moved laterally.

Description

Device and method for in-situ fixture surface roughening

The present invention relates to a fixture that can be used to hold a reticle or substrate in a device used for semiconductor photolithography, and more particularly, to the treatment of the surface of such a fixture that contacts the reticle or substrate.

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. Lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In that case, a patterned device (which is alternatively called a mask or a reticle) may be used to produce the circuit pattern to be formed on individual layers of the IC. This pattern may be transferred to a target portion (e.g. comprising a portion of one or more dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is usually performed by imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of sequentially patterned adjacent target portions.

Known lithography devices include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern in a given direction (the "scanning" direction) by means of a radiation beam while simultaneously scanning the substrate parallel or antiparallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by embossing the pattern onto the substrate.

By using a clamp, an object such as a patterned device or substrate is attached to an object support such as a mask stage or wafer stage, respectively. An electrostatic clamp can be provided to electrostatically clamp the object to the object support. As part of holding the object, the clamp is in contact with the object. If necessary, the surface of the clamp that contacts the object is roughened. Otherwise, even after the electrostatic clamping force is removed, the object has a tendency to continue to adhere to the clamp due to the extremely flat surfaces of the clamp and the object being adhered via optical contact. This "stickiness" can complicate and prolong the time required to remove the object from the clamp, or even prevent damage-free removal.

During the life of a gripper, the gripper surface must be roughened periodically or, for example, when it begins to become sticky. Gripper roughening is typically performed with the scanner/stepper offline and the gripper removed from its operating environment. This can create a significant amount of downtime.

Therefore, there is a need for a system for roughening the fixture to reduce machine downtime.

The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of the embodiments. This invention content is not a comprehensive overview of all covered embodiments, and is neither intended to identify the key or important elements of all embodiments, nor is it intended to limit the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to a more detailed description presented later.

According to one aspect of the embodiment, a device and method are disclosed for in-situ roughening of a fixture by providing a roughened substrate that can be loaded in the same manner as a reticle or substrate and then moved to and pressed against the surface of the fixture to be roughened. The roughened substrate includes abrasive elements that are connected to the substrate base by a flexure so that the abrasive elements can conform to the surface of the fixture and apply a substantially uniform normal force to the fixture surface. The abrasive elements are then moved back and forth laterally to roughen the fixture surface.

According to another aspect of the embodiment, each grinding element has a respective actuator, such as a piezoelectric element, which is controlled to move the grinding element laterally.

According to another aspect of the embodiment, a device is disclosed that includes a substrate base and a plurality of grinding elements, each of which is mechanically coupled to the substrate base by a respective coupling element. The substrate base may include a zoom mask base. Each of the respective grinding elements may include a piezoelectric element that is configured to move the respective grinding element laterally under the control of a control unit. Each of the respective coupling elements may include a respective flexure that may be preloaded and may have a low spring constant in a direction substantially perpendicular to the substrate base. The spring constant in a direction substantially perpendicular to the substrate base is in a range of about 50 N/m to about 5000 N/m.

Each of the plurality of polishing elements may have substantially the same shape and size. The plurality of polishing elements may be arranged in an array, which may be an ordered array. The array may substantially cover the substrate base.

Each of the grinding elements may include a ceramic material. For each of the grinding elements, a distance between the grinding element and the substrate base may be limited by a stopper.

According to another aspect of the embodiment, a method for roughening the surface of a fixture in a semiconductor photolithography apparatus is disclosed, the method comprising the following steps: loading a roughened substrate onto a platform, the roughened substrate having a surface with a plurality of grinding elements; aligning the roughened substrate with the fixture so that the surface of the fixture having the nodules is opposite to the surface of the roughened substrate having the grinding elements; pressing the grinding elements against the surface of the fixture; roughening the nodules by substantially translating the grinding elements in a plane substantially parallel to the surface of the fixture until a desired roughness is obtained; moving the roughened substrate away from the fixture; moving the roughened substrate to a position where a roughened multiplied mask can be unloaded from the platform, and unloading the roughened substrate from the platform. The step of translating the roughened substrate in a plane substantially parallel to the surface of the fixture until a desired roughness is obtained includes determining the time when the nodules have the desired roughness. Determining the time to obtain a desired roughness includes determining the time that an amount of time known to cause the desired roughness has elapsed. Determining the time to obtain the desired roughness includes sensing the roughness of the nodule. Roughening the nodule by generally translating the grinding element in a plane generally parallel to the surface of the fixture until the desired roughness is obtained may include moving the substrate. A plurality of grinding elements may be mechanically coupled to respective actuators, and roughening the nodule by generally translating the grinding element in a plane generally parallel to the surface of the fixture until the desired roughness is obtained may include causing the actuator to generally move its respective grinding element in a plane generally parallel to the surface of the fixture. The actuator may include a piezoelectric element.

Other embodiments, features and advantages of the subject matter of the present invention, as well as the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings.

Various embodiments are now described with reference to the drawings, wherein like reference numerals are used throughout to refer to like elements. In the following description, for the purpose of explanation, numerous specific details are set forth in order to enhance a thorough understanding of one or more embodiments. However, it may be apparent in some or all cases that any of the embodiments described below may be practiced without employing the specific design details described below. In the following description and in the claims, the terms "upper," "lower," "top," "bottom," "vertical," "horizontal," and similar terms may be used. Unless otherwise specified, such terms are intended to indicate only relative orientation with respect to gravity, and not any orientation.

FIG. 1 schematically illustrates a lithography apparatus 100 according to an embodiment of the present invention. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or EUV radiation); a support structure or support member or pattern support member (e.g. mask stage) MT constructed to support a patterned device (e.g. mask) MA and connected to a first positioner PM configured to precisely position the patterned device according to certain parameters; a substrate stage (e.g. wafer stage) WT constructed to hold a substrate (e.g. anti-etching agent coated wafer) W and connected to a second positioner PW configured to precisely position the substrate according to certain parameters; and a projection system (e.g. refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B onto a target portion C of the substrate W via the patterned device MA. (eg, including one or more dies).

Illumination systems may include various types of optical components for directing, shaping, or controlling radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof.

The support structure holds the patterned device in a manner that depends on the orientation of the patterned device, the design of the lithography apparatus, and other conditions (e.g., whether the patterned device is held in a vacuum environment). The support structure may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterned device. The support structure may be, for example, a frame or table, which may be fixed or movable as desired. The mask support structure may ensure that the patterned device is in a desired position, for example, relative to a projection system. Any use of the term "reduced mask" or "mask" herein may be considered synonymous with the more general term "patterned device."

The term "patterned device" as used herein should be broadly interpreted as referring to any device that can be used to impart a pattern to a radiation beam in its cross-section so as to create a pattern in a target portion of a substrate. It should be noted that if, for example, the pattern imparted to the radiation beam includes phase-shifting features or so-called auxiliary features, the pattern may not correspond exactly to the desired pattern in the target portion of the substrate. Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in a device (such as an integrated circuit) created in the target portion.

Patterned devices can be transmissive or reflective. Examples of patterned devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. One example of a programmable mirror array uses a matrix arrangement of mirror facets, each of which can be individually tilted so as to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam that is reflected by the mirror array.

The term "projection system" as used herein should be interpreted broadly to cover any type of projection system appropriate to the exposing radiation used or to other factors such as the use of an immersion liquid or the use of a vacuum, including refractive, reflective, catadioptric, magnetic, electromagnetic, and electro-optical systems, or any combination thereof. Any use of the term "projection lens" herein should be considered synonymous with the more general term "projection system."

The supporting structure and the substrate stage may also be referred to as an object support hereinafter. The object includes but is not limited to a patterned device (such as a reticle) and a substrate (such as a wafer).

As described herein, the device is of a reflective type (eg, using a reflective mask). Alternatively, the device may be of a transmissive type (eg, using a transmissive mask).

The lithography apparatus may be of a type having two (dual stage) or more substrate stages (and/or two or more mask stages). In such "multi-stage" machines, the extra stages may be used in parallel, or preparatory steps may be performed on one or more stages while one or more other stages are being used for exposure.

The lithography apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, so as to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithography apparatus, such as the space between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term "immersion" as used herein does not mean that structures such as the substrate must be immersed in the liquid, but only that the liquid is located between the projection system and the substrate during exposure.

Referring to Figure 1, the illuminator IL receives a radiation beam from a radiation source SO. For example, when the source is an excimer laser, the source and the lithography apparatus may be separate entities. In such cases, the source is not considered to form part of the lithography apparatus, and the radiation beam is delivered from the radiation source SO to the illuminator IL by means of a beam delivery system comprising, for example, suitable guide mirrors and/or a beam expander. In other cases, for example, when the source is a mercury lamp, the source may be an integral part of the lithography apparatus. The radiation source SO and the illuminator IL together with the beam delivery system (if necessary) may be referred to as a radiation system.

The illuminator IL may include an adjuster for adjusting the angular intensity distribution of the radiation beam. In general, at least the outer and/or inner radial extent of the intensity distribution in a pupil plane of the illuminator (commonly referred to as σ outer and σ inner, respectively) may be adjusted. Furthermore, the illumination system IL may include various other components, such as an integrator and a condenser. The illuminator may be used to adjust the radiation beam to have a desired uniformity and intensity distribution in its cross-section.

A radiation beam B is incident on a patterned device (e.g. a mask) MA held on a support structure (e.g. a mask table) MT and is patterned by the patterned device. After reflection from the patterned device (e.g. a mask) MA, the radiation beam B passes through a projection system PS which focuses the beam onto a target portion C of a substrate W. By means of a second positioner PW and a position sensor IF2 (e.g. an interferometric device, a linear encoder or a capacitive sensor), the substrate table WT can be precisely moved, e.g. in order to position different target portions C in the path of the radiation beam B. Similarly, a first positioner PM and a further position sensor IF1 can be used to precisely position the patterned device (e.g. a mask) MA relative to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library or during scanning. In general, movement of the support structure (e.g., mask table) MT may be achieved by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming part of a first positioner PM. Similarly, movement of the substrate table WT may be achieved using a long-stroke module and a short-stroke module forming part of a second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure (e.g., mask table) MT may be connected to a short-stroke actuator only, or may be fixed. The mask alignment marks M1, M2 and substrate alignment marks P1, P2 may be used to align the patterned device (e.g., mask) MA and the substrate W. Although the substrate alignment marks as described occupy dedicated target portions, the substrate alignment marks (these are called street alignment marks) can be positioned in spaces between target portions. Similarly, in the case where more than one die is disposed on a patterned device (e.g., a mask) MA, the mask alignment marks can be positioned between the dies.

FIG2 depicts a partial cross-section of a fixture 110 (which may be an electrostatic fixture) that may be applied to the edge of an object such as a zoom mask or a wafer. FIG2 also schematically illustrates the fixture pressure that may be generated by the fixture by the arrows in the figure. The fixture 110 includes a fixture lower portion 120 formed of an insulating material and a fixture upper portion 130 formed of a dielectric material. The fixture upper portion 130 is formed with a plurality of nodules 140. The tops of the nodules 140 define a plane 150 in which an object (not shown) is held. The first electrode 160 is disposed between the clamp lower portion 120 and the clamp upper portion 130, and the first electrode 160 is adapted to be held under a voltage (typically 3 kV) to generate an electrostatic clamping force. The ground electrode 170 is held to the ground and is separated from the first electrode 160 by a gap 180, which acts as a barrier between the first electrode and the ground electrode. The gap 180 may be filled with an insulating material, a dielectric material, or remain empty.

The downward arrow in Figure 2 schematically illustrates the clamping pressure that can be generated by the clamp of Figure 2. The length of the arrow represents the clamping force, and it can be seen that a uniform clamping pressure can be generated across the width of the first electrode, the magnitude of which depends on a number of parameters, including the applied voltage, the dielectric constant of the clamp upper portion 130, and the dimensions of the various portions of the clamp 110. When a voltage is applied to the first electrode 160, an object can be held in the plane 150 by an electrostatic clamping force. For example, additional details regarding electrostatic clamps of this nature are disclosed in U.S. Patent No. 9,455,172, issued September 27, 2016, the entire contents of which are incorporated herein by reference.

As described above, in operation, the top of the nodules 140 contacts the generally flat surface of the object to be held. This can result in optical contact binding of these surfaces, which can prevent effective removal of the object from the fixture. To address this problem, the top of the nodules can be intentionally roughened to prevent adequate optical contact. Generally speaking, the surface roughness Ra (arithmetic mean of the absolute value of the profile height deviation from the center line) is preferably in the range of about 3 nm to about 7 nm.

During use, the nodule top surface may become too smooth due to wear, making optical contact bonding possible again. When this happens, it is necessary to re-roughen the nodule top. One way to achieve this is to remove the fixture from the tool and roughen the fixture manually. However, this results in a significant loss of downtime. Alternatively, it would be advantageous to have a system for re-adjusting the nodule top in situ and utilizing shorter downtime.

The following discussion uses a reticle as an example, but it should be understood that the disclosed principles can be applied to other clamped objects, such as substrates. FIG. 3 shows an example of a roughened reticle 200 according to one aspect of an embodiment. The roughened reticle 200 includes an array of abrasive elements 210 mounted on a reticle base 220 in a manner described below. The roughened reticle 200 can be loaded into the tool just like any other reticle, but after it is positioned facing the fixture, the reticle 200 is pressed against the fixture and caused to move laterally. This causes the abrasive elements 210, which are configured to substantially cover the surface of the roughened reticle 200, to contact the nodules on the fixture and subsequently roughen the top of the nodules. As an example, the grinding elements 210 (e.g., ceramic "stones") in the configuration of FIG. 3 are arranged in an ordered array, but other configurations are possible, including non-ordered arrays and arrays containing grinding elements of different sizes and shapes. In addition, the array in FIG. 3 is a 4×4 array, but it will be apparent to one of ordinary skill in the art that arrays of other sizes can be used. The overall size of the array and grinding elements 210 is selected so that the roughening retraction mask is close enough to the same size as a standard retraction mask that devices designed to work with the standard retraction mask will also work with the roughening retraction mask.

The grinding element 210 may include any material used to roughen a surface, such as a ceramic material. Other examples of materials that may be used include aluminum oxide and zirconium oxide.

Parameters relevant to the roughening process include the amount of force applied to the grinding element 210 when sliding on the fixture surface, the uniformity of the pressure between the grinding element 210 and the nodules 140 on the grinding element area, and the roughness of the stone. One of the main challenges of in-situ roughening is to ensure that the pressure on all zoom mask fixture nodules is uniform and consistent. This design goal is achieved by the system described below. As for the roughness of the stone, the same material can have a variety of different roughness. In general, the roughness of the stone used in the system disclosed in this article ranges from about 200 nm to about 1000 nm.

4A shows an example of a roughened reticle 200 according to one aspect of an embodiment. The roughened reticle 200 includes a plurality of abrasive elements 210 that together substantially cover the entire surface of a reticle substrate 220.

As described above, two parameters relevant to the roughening process are the amount of force applied to the grinding element when sliding on the fixture surface and the uniformity of the pressure between the grinding element 210 and the nodule 140 on the grinding element area. It is most advantageous if the pressure is uniform and consistent on all zoom mask fixture nodules. To control these parameters and as shown in Figure 4A, each of the grinding elements has at least one flexure 230. For example, the flexure 230 can be a spring. The flexure 230 is pre-loaded to ensure a uniform minimum normal force while conforming to the shape and flatness of the fixture 110, as shown in Figure 4B. The stop 240 limits the vertical and horizontal movement of the grinding element 210 when the flexure 230 is pre-loaded.

Thus, each grinding element 210 is attached to the reticle substrate 220 by a flexure 230. The flexure 230 is preloaded in the z-direction and is designed to have a low spring constant (i.e., "softer") in the z-direction. The flexure 230 has a spring constant in the range of about 50 N/m to about 5000 N/m in a direction generally perpendicular to the reticle substrate 220. This ensures the desired consistency of the normal force between the fixture and the grinding element, which will be approximately the same as the preload force.

The flexible preloaded flexure ensures conformity to the fixture surface. Each grinding element in the grinding element array is mechanically coupled to the reticle substrate using a flexure (e.g., a spring) having a low spring constant preloaded in the z direction (orthogonal to the array corresponding to the xy plane) and having a low spring constant (softer) in z, Rx (rotation about the x axis), and Ry (rotation about the y axis), and a higher spring constant (harder) in all other degrees of freedom. The stopper 240 limits the movement of the grinding element in the z direction so that the grinding element 210 stays at a predetermined distance from the reticle substrate at most. The low spring force spring allows for a substantially constant spring force over the range of displacement in the z-direction because the applied force is sufficient to account for the preload of all grinding elements 210.

4B , the roughening reticle 200 moves in the z direction so that when the grinding element 210 is pressed against the nodules 140 on the fixture 110, the force generated by the displacement of the grinding element 210 overcomes the upward spring force applied by the deflection member 230. In this case, the force applied by the deflection member 230 is substantially constant, thus applying a substantially constant normal force on the nodules 140. Each grinding element 210 contacts a certain number n of nodules 140. Each grinding element 210 conforms to the fixture surface independently.

FIG. 5 is a flow chart of an example of a jig roughening process using a roughened multiplied mask 200. In step S500, the roughened multiplied mask 200 is loaded onto a multiplied mask stage, just like a conventional multiplied mask. In step S510, the roughened multiplied mask 200 is then aligned with the jig 110 so that the surface of the jig 110 with the nodules 140 is opposite to the surface of the roughened multiplied mask 200 with the abrasive elements 210. In step S520, the multiplied mask stage is controlled to press the roughened multiplied mask 200 against the jig 110 so that the abrasive elements 210 will contact the nodules 140 to obtain the desired contact force and displacement. The deflection member 230 will deform to maintain a separate force around the preload. In step S530, the reduction mask stage is then commanded to translate the roughened reduction mask 200 in the xy plane to perform polishing until the desired roughness is obtained. The desired roughness will have an Ra in the range of about 3 nm to about 7 nm. Then in step S540, the roughened reduction mask 200 is pulled away from the fixture. Then in step S550, the roughened reduction mask 200 is moved away from the fixture to a position where the roughened reduction mask 200 can be unloaded. Then in step S560, the roughened reduction mask 200 is unloaded from the reduction mask stage.

When the relative motion is performed for an a priori known amount of time to produce the desired surface roughness, step S530 may terminate. Alternatively, a portion of performing step S530 may include, for example, optically using sensor data to generate a positive determination that the desired surface roughness has been achieved by performing the relative xy motion until such determination is positive.

In an alternative embodiment shown in Figure 6, each individual grinding element 210 is individually actuated by an individual actuator 250 (e.g., using a piezoelectric element). The actuator 250 moves its individual grinding element 210 laterally (i.e., in the xy plane) under the control of a control unit 260. This force can be applied in a coordinated manner so that as the grinding elements 210 move in different directions in the xy plane, the total net applied lateral force will be substantially zero so that they generally cancel each other out.

The following clauses may be used to further describe embodiments: 1.   A device comprising: a substrate base; a plurality of polishing elements, each of the polishing elements being mechanically coupled to the substrate base by a respective coupling element. 2.   The device of clause 1, wherein the substrate base comprises a zoom mask base. 3.   The device of clause 1, wherein each of the respective polishing elements further comprises a piezoelectric element configured to move the respective polishing element laterally under the control of a control unit. 4.   The device of clause 1, wherein each of the respective coupling elements comprises a respective flexure. 5.   The device of clause 4, wherein each respective flexure is preloaded. 6.   The device of clause 4, wherein each respective flexure has a low spring constant in a direction substantially perpendicular to the substrate base. 7.   The device of clause 4, wherein each respective flexure has a spring constant in a direction generally perpendicular to the substrate base in the range of about 50 N/m to about 5000 N/m. 8.   The device of clause 1, wherein each of the plurality of grinding elements has generally the same shape and size. 9.   The device of clause 1, wherein the plurality of grinding elements are arranged in an array. 10.   The device of clause 9, wherein the array is an ordered array. 11.   The device of clause 9, wherein the array generally covers the substrate base. 12.   The device of clause 1, wherein each of the grinding elements comprises a ceramic material. 13.   The device of clause 1, wherein for each of the grinding elements, the distance between the grinding element and the substrate base is limited by a stop. 14. A method for roughening the surface of a fixture in a semiconductor photolithography apparatus, the method comprising the following steps: Loading a roughened substrate onto a platform, the roughened substrate having a surface with a plurality of grinding elements; Aligning the roughened substrate with the fixture so that the surface of the fixture having the nodules is opposite to the surface of the roughened substrate having the grinding elements; Pressing the grinding elements against the surface of the fixture; Roughening the nodules by translating the grinding elements in a plane substantially parallel to the surface of the fixture until a desired roughness is obtained; Moving the roughened substrate away from the fixture; Moving the roughened substrate to a position where a roughened multiplied mask can be unloaded from the platform; and Unloading the roughened substrate from the platform. 15. The method of clause 14, wherein the step of translating the roughened substrate in a plane substantially parallel to the surface of the fixture until the desired roughness is obtained comprises determining a time at which the nodule has the desired roughness. 16. The method of clause 15, wherein determining a time at which the desired roughness is obtained comprises determining a time at which an amount of time known to cause the desired roughness has elapsed. 17. The method of clause 15, wherein determining a time at which the desired roughness has been obtained comprises sensing the roughness of the nodule. 18. The method of clause 14, wherein roughening the nodule by translating the abrasive element substantially in a plane substantially parallel to the surface of the fixture until the desired roughness is obtained comprises moving the substrate. 19.  The method of clause 14, wherein a plurality of abrasive elements are mechanically coupled to respective actuators, and wherein roughening the nodule by generally translating the abrasive elements in a plane generally parallel to the surface of the fixture until a desired roughness is obtained comprises causing the actuator to generally move its respective abrasive elements in a plane generally parallel to the surface of the fixture. 20.  The method of clause 19, wherein the actuator comprises a piezoelectric element.

The present invention is made with functional building blocks that illustrate the implementation of specific functions and their relationships. The boundaries of such functional building blocks have been arbitrarily defined herein for ease of description. Alternate boundaries may be defined so long as the specified functions and their relationships are properly performed. For example, the metrology module functions may be divided between several systems, or at least partially performed by the entire control system.

The above description includes examples of one or more embodiments. Of course, it is not possible to describe every conceivable combination of components or methods for the purpose of describing the aforementioned embodiments, but those skilled in the art will recognize that many additional combinations and arrangements of the various embodiments are possible. Therefore, the described embodiments are intended to encompass all such changes, modifications and variations that fall within the spirit and scope of the appended claims. In addition, to the extent that the term "including" is used in an embodiment or in the claims, this term is intended to be inclusive in a manner similar to the term "comprising" when "comprising" is used as a transitional word in a technical solution. In addition, although the elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is also covered unless a singular limitation is explicitly stated. In addition, unless otherwise stated, all or a portion of any aspect and/or embodiment may be utilized in combination with all or a portion of any other aspect and/or embodiment.

100: lithography device 110: fixture 120: lower part of fixture 130: upper part of fixture 140: nodule 150: plane 160: first electrode 170: ground electrode 180: gap 200: zoom mask 210: grinding element 220: zoom mask base 230: deflector 240: stopper 250: actuator 260: control unit B: radiation beam C: target part IL: illuminator M1: mask alignment mark M2: mask alignment mark MA: patterning device MT: support structure P1: substrate alignment mark P2: substrate alignment mark PM: first positioner PS: projection system PW: Second positioner SO: Radiation source W: Substrate WT: Substrate stage S500: Step S510: Step S520: Step S530: Step S540: Step S550: Step S560: Step

FIG. 1 depicts a lithography apparatus according to an embodiment of the present invention.

FIG. 2 depicts a partial cross-section of a conventional edge clamp and schematically illustrates the clamp pressure.

FIG. 3 is a plan view of a roughened substrate according to an embodiment of the present invention.

FIG. 4A is a cross-sectional view of a roughened substrate according to an embodiment of the present invention.

FIG. 4B is a cross-sectional view of a roughened substrate engaged with a fixture according to an embodiment of the present invention.

FIG. 5 is a flow chart illustrating a method for roughening a fixture surface according to an embodiment of the present invention.

FIG6 is a plan view of a roughened substrate according to an embodiment of the present invention.

Other features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein.

200: Zoom mask

210: Grinding element

220: Zoom mask base

230: bending parts

240: Stopper

Claims (7)

A method for roughening the surface of a clamp in a semiconductor photolithography apparatus, the method comprising the following steps: Loading a roughened substrate onto a platform, the roughened substrate having a surface with a plurality of abrasive elements; Aligning the roughened substrate with the clamp so that a surface of the clamp having nodules is opposite a surface of the roughened substrate having abrasive elements; Pressing the abrasive elements against the surface of the clamp; Roughening the nodules by translating the abrasive elements in a plane substantially parallel to the surface of the clamp until a desired roughness is obtained; Moving the roughened substrate away from the clamp; Moving the roughened substrate to a position where a roughening reticle can be unloaded from the platform; and Unloading the roughened substrate from the platform. The method of claim 1, wherein the step of translating the roughened substrate in the plane substantially parallel to the surface of the fixture until the desired roughness is obtained includes determining when the nodules have the desired roughness. The method of claim 2, wherein determining when the desired roughness has been achieved comprises determining a time elapsed that is known to result in the desired roughness. The method of claim 2, wherein determining when the desired roughness has been achieved comprises sensing the roughness of the nodules. The method of claim 1, wherein roughening the nodules by translating the grinding elements substantially in the plane substantially parallel to the surface of the fixture until the desired roughness is obtained includes moving the substrate. A method as claimed in claim 1, wherein a plurality of the grinding elements are mechanically coupled to respective actuators, and wherein roughening the nodules by translating the grinding elements substantially in the plane substantially parallel to the surface of the fixture until the desired roughness is obtained includes causing the actuators to move their respective grinding elements substantially in the plane substantially parallel to the surface of the fixture. A method as claimed in claim 6, wherein the actuators comprise a piezoelectric element.