JP5852043B2 - Device for homogenizing laser radiation and method of manufacturing the same - Google Patents

Description

  The invention relates to a device for homogenizing laser radiation in the illumination field according to the preamble of claim 1 and to a method of manufacturing such a device.

  In many cases, not only in an illumination system in a projection exposure apparatus for microlithography, but also in an optical system for other applications, one purpose is to illuminate the illumination field as uniformly as possible It is. For this purpose, the light emitted from the primary radiation source should generally be adjusted by appropriate sub-optical systems in the illumination system.

  If a laser is used as the primary radiation source, it should be taken into account that the laser radiation emitted by the laser generally has a non-uniform intensity distribution, usually referred to as a non-uniform beam distribution. As an example, the laser radiation emitted by an excimer laser has a normal distribution in one direction and a substantially trapezoidal intensity distribution perpendicular to this direction. The intensity distribution may vary over time. During operation, lateral beam offsets and angular offsets can also occur.

  However, in order to obtain a sufficiently uniform intensity distribution in the illumination field at any point in time, a device for homogenizing laser radiation, often referred to as a beam homogenizer, is used.

  German patent application DE 102 25 674 A1 describes a cylindrical lens element system for homogenizing laser radiation. The cylindrical lens element system includes a first cylindrical lens element array including a plurality of first cylindrical lens elements and a plurality of second cylindrical lenses disposed in a beam path of laser radiation downstream of the first cylindrical lens element. And at least one second cylindrical lens element array including the elements so that the laser radiation is imaged in an at least partially uniformized manner on the illumination field. The cylindrical lens element has a convex cylindrical lens element surface. The cylindrical lens element array consists of individual cylindrical lens elements that support each other along the edge of the lens element in each case. Due to diffraction effects at the edge of the lens element, intensity amplification may occur around the illuminated field of view. In order to improve the homogenization effect, a part of the first cylindrical lens element and / or the second cylindrical lens element is used to irradiate the laser radiation onto the illumination field and the other first and / or second It has been proposed that the cylindrical lens elements be shaped and / or positioned so as to image the laser radiation with a different dimension than the one that images the laser radiation onto the illumination field. In one embodiment, the second cylindrical lens element array has cylindrical lens elements that are alternately and shaped to lie in a plane perpendicular to the beam direction and whose focal lengths have alternately different values. .

  Patent EP 1 839 083 B1 includes a first cylindrical lens element array through which the light to be homogenized can pass, and a second through which light that has passed through the first cylindrical lens element array can pass. A device for homogenizing light comprising a cylindrical lens element array is described. Each of the first cylindrical lens element array and the second cylindrical lens element array has convex and concave cylindrical lens elements having cylindrical axes parallel to each other, and these cylindrical lens elements are arranged side by side and alternately. Is done. The cylindrical axes of the cylindrical lens elements of the first and second cylindrical lens element arrays extend parallel to each other. The vertex line of the convex cylindrical lens element of the first cylindrical lens element array is aligned with the vertex line of the convex cylindrical lens element of the second cylindrical lens element array. Further, the vertex line of the concave cylindrical lens element of the first cylindrical lens element array is aligned with the vertex line of the concave cylindrical lens element of the second cylindrical lens element array. The concave cylindrical lens elements of the first cylindrical lens element array have a different spread in the direction in which the cylindrical lens elements are arranged side-by-side from the corresponding direction of the concave cylindrical lens elements of the second cylindrical lens element array. Have. In the case of the illustrated embodiment, the cylindrical lens element array is embodied as an integral optical element, each of which is at least one optical element formed in such a manner that the convex cylindrical lens element surfaces are located side by side with each other. It has a functional substrate surface. Convex cylindrical lens element surfaces located immediately adjacent to each other fuse together in a concave shaped transition region, and the concave shaped transition region forms a concave cylindrical lens element surface in each case. Targeted changes in the extent and / or curvature of the concave cylindrical lens elements of the first and / or second cylindrical lens element array can avoid excessive intensity increases in the periphery of the illuminated illumination field It is intended to be.

DE 102 25 674 A1 EP 1 839 083 B1

  One problem addressed by the present invention is to improve a general purpose device for homogenizing the laser radiation in the illumination field so that the homogenization effect is not affected by the instability of the laser radiation incident in the device. is there. Yet another problem to be addressed is to provide a method of manufacturing such a device.

  In order to solve these and other problems, the present invention provides a device comprising the features of claim 1. Furthermore, a method comprising the features of claim 12 is provided. Furthermore, a device comprising the features of claim 17 and an illumination system comprising the features of claim 19 are provided.

  Advantageous developments are specified in the dependent claims. All wording of the claims is incorporated into the content of this description by reference.

  A general purpose device for homogenizing laser radiation in an illumination field has a first substrate that allows laser radiation to pass in the direction of the illumination field from the incident side. The first substrate has at least one optical functional substrate surface formed in such a manner that a plurality of convex cylindrical surfaces having cylindrical axes parallel to each other are positioned side by side. Convex cylindrical lens element surfaces located directly adjacent to each other fuse in each case within the transition region. Such a first substrate is embodied as an integral optical element in a microlens element array manner, and the shaping of the optically functional substrate surface results in the desired optical effect of this substrate surface. In this case, the transition region is, first of all, the portion of the illumination intensity generated by the transition region in the illumination field is much greater than the portion of the illumination intensity generated by the convex cylindrical lens element surface in the illumination field. Second, the local distribution of this part in the illumination field (which may be caused by the transition region) is designed to be substantially independent of variations in the laser radiation incident into the device. Variations in incident laser radiation may be caused, for example, by intensity variations in the beam distribution, by lateral beam offsets, and / or by angular variations (directed) at the device location.

  Compared to a beam homogenizer that includes a cylindrical lens element array composed of individual cylindrical lens elements, this configuration can take advantage of the manufacturing and stability of an integral lens element array. There are no undesired edges where the diffractive effect may lead to an undesirable light distribution.

  In this case, the refractive effect of the concave cylindrical lens element surface is intentionally omitted when compared to an integral cylindrical lens element array having alternating convex and concave cylindrical lens element surfaces on the patterned substrate surface. It is burned. Alternatively, the portion of the optical functional substrate surface that occupies an overwhelming portion of the laser radiation that passes toward the illumination field originates from the region of the convex cylindrical lens element surface and, in comparison, the portion that originates from the transition region Is shaped as small as possible. In this case, these parts of the radiation emanating from the transition region are guided in such a way that this part of the disturbance does not cause a local increase or decrease of the illumination intensity in the illumination field in the case of variations in the incident laser radiation. It is burned.

  Even in the device according to the claimed invention, in some cases it cannot be avoided that a certain part of the intensity in the illumination field emanates from the transition region. However, at locations within the device's far field, there is no local accumulation of radiation intensity and there is an optical effect of different transition regions so that there is at least an approximately uniform distribution of the effects of all transition regions. Having can be accomplished. This approach is based in particular on the following insights.

  In many cases, trying to separate the far field of the device, i.e., the intensity distribution in the illumination field, from instabilities on the light source side, for example, placed one after the other in a fly-eye condenser or similar array, for example. A cylindrical lens element array is used. It has been recognized that this separation is not easily possible for the radiation part emanating from the transition region. In general, the transition region causes an additional light distribution in the illumination field that shifts depending on the characteristics of the incident laser radiation in the illumination field. When all the transition regions have the same surface shape, for example, a concave shape, it may occur that all the radiation portions emitted from the transition region are incident on the same field region of the illumination field. In this case, there is a risk that the radiation portions emitted from the transition region will be summed up in a locally undesirable manner. This adversely affects the temporal uniformity of the illumination within the illumination field, also called “uniformity stability”. Such local inhomogeneities occur naturally and temporarily when appropriate in the case of illumination variations, i.e. temporal variations or incident laser radiation variations, even if there is an intensity correction factor, Either it works only statically or cannot react fast enough, so it cannot be corrected or it can only be corrected with difficulty.

  In the case of the claimed invention, the intensity of these error portions is substantially reduced, so that even in the case of variations in illumination intensity on the light incident side of beam uniformity, the desired local area within the illumination field is desired. The intensity distribution is kept within the tolerance range. In this respect, the device according to the invention is essentially less sensitive to variations in incident laser radiation. Therefore, subsequent correction is unnecessary.

  There may be various practical implementations within the scope of the claimed invention.

  In some embodiments, the transition region has an irregular surface shape that differs in the direction in which adjacent convex cylindrical lens element surfaces lie side by side. In this case, in particular, each transition region may have a different irregular surface shape in the direction in which adjacent convex cylindrical lens element surfaces are located side by side.

  In this case, the term “irregular surface shape” cannot be defined in particular by the value of the radius of curvature and / or by a locally precisely defined deviation from the basic curvature. Therefore, such irregular surface shapes do not have a uniform lens element effect or a uniform focal length. The optical effect of a preferable irregular surface shape is mainly a scattering effect. The deviation of the irregular surface shape from a similar regular surface shape, for example a planar shape or a cylindrical curved shape, is in this case larger than the manufacturing tolerance. As a result, even in the case of fluctuations in illumination intensity on the incident side, the low radiation part emanating from the transition region is always distributed almost uniformly over the illumination field.

  Similar, or equal types of three, four, five, six, or more transition regions with different irregular surface shapes in each case occur at the structured substrate surface. It is particularly preferred if each transition region has a different irregular surface shape.

  It has been found that the transition region is particularly preferred if it has a random distribution of surface shapes in the direction in which adjacent convex cylindrical lens element surfaces lie side by side. Therefore, the surface shape of the transition region can be randomized with respect to its optical effect. Due to the random change in the shape of the transition region, possible external light can be mixed and thus its overall effect can be locally attenuated. In the case of an appropriate design of the transition region, the transition region can perform a diffusion shielding function. Also in this case, the intensity contribution of the transition region shifts depending on the illumination on the light incident side. However, all of the contributions shift equally and do not result in excessive local intensity increases.

  Means for randomizing the transition region may be advantageous independent of other features in the universal device.

  Different randomly distributed (randomized) surface shapes can be different irregular surface shapes. However, it is also possible for the transition regions to have different concave shapes distributed according to a random distribution. The concave transition region can have, for example, different widths, different radii of curvature, and / or different depths, and one or more of these characteristics vary according to a random distribution.

  Alternatively or additionally, the transition region is possible in order to keep the portion of the radiation that passes through the transition region generally towards the illumination field small compared to the portion that passes through the convex cylindrical lens element surface. It can be as narrow as possible. Thus, one embodiment is that the transition region has a width that is less than 5% of the width of the convex cylindrical lens element surfaces joined in this direction in the direction in which adjacent convex cylindrical lens element surfaces are located side by side. to enable. In particular, the width of the transition region may be less than 4% of the width of the convex cylindrical lens element surface to be joined, less than 3%, less than 2%, or less than 1%. In this case, the width of the convex cylindrical lens element surface can be determined in particular between lines in which the surface shape of the convex cylindrical lens element lying between the lines can be described analytically. Alternatively or additionally, the lateral boundary of the convex cylindrical lens element surface can be determined by changing the sign of the curvature direction or radius of curvature at the joint.

  Alternatively or additionally, the transition region may allow the adjacent convex cylindrical lens element surfaces to have a width of less than 30 μm in the direction in which they are located side by side, this width being preferably 15 μm. Or less, in particular 10 μm or less. Usually, for technical reasons, in particular, it does not mean that a minimum width of 5 μm is undershot, or only in exceptional cases.

  Alternatively or additionally, the transition region is more than 5% of the center-to-center distance (pitch) between the convex cylindrical lens element surfaces joined in this direction in the direction in which adjacent convex cylindrical lens element surfaces are located side by side. In particular, less than 3% of this center-to-center distance, less than 2% and less than 1%.

  In this case, the transition region can be shaped, for example, as a substantially V-shaped notch between the convex cylindrical lens element surfaces that are directly joined.

  Alternatively or additionally, it may be preferred to use suitable means to completely block a significant part of the laser radiation from passing through the transition region in the direction of the illumination field. In some embodiments, the transition region is substantially opaque to the laser radiation used. This is achieved, for example, by a substrate surface carrying a light-impermeable coating in the transition region, which significantly absorbs and / or reflects incident laser radiation. In particular, separate substrate cooling can be advantageous when using a coating that absorbs most of the radiation. A coating can be provided over the irregular surface shape to prevent the retroreflective radiation portion from causing retroreflection that results in disturbances.

  Where appropriate, a transition region in the form of a concave cylindrical lens element, using a black dye or coating that is opaque to the maximum possible wavelength at the wavelength of the laser radiation (preferably having a transmission close to 0). This transition region can be made "harmless" with respect to optical effects on the intensity distribution within the illumination field. In the optical path upstream of the substrate surface, a separate radiation shielding optical element or radiation deflecting optical element that shields only the transition region and allows the radiation to pass as far as possible towards the convex cylindrical lens element surface without obstruction. It can also be installed. Corresponding means can be provided in the case of a conventional cylindrical lens element array composed of individual cylindrical lens elements.

  In some embodiments, the convex cylindrical lens elements have a uniform distance between the apex lines in the direction in which the concave cylindrical lens elements are located side by side. As a result, combinations with other substrates to form multi-stage devices can often be particularly advantageous.

  The first substrate is a flat or continuously curved substrate surface, or similarly convex and / or concave cylinder, on the side opposite to the optical functional substrate surface composed of convex cylindrical lens element surfaces. It can have a lens element surface.

  In some embodiments, a plurality of convex cylindrical lens element surfaces having cylindrical axes parallel to each other are formed in a manner that is also located side by side on opposite substrate surfaces. These vertex lines may extend parallel to the vertex line of the opposite cylindrical lens element surface. In other embodiments, the cylinder axes on opposite sides of the first substrate are rotated by 90 degrees relative to each other. Thus, in this case, the first substrate has intersecting cylindrical lens element arrays. As a result, the laser radiation passing in two mutually perpendicular directions can be made uniform using the patterned substrate.

  In some embodiments, the device includes a second substrate that allows laser radiation to pass from the incident side in the direction of the illumination field, the second substrate having a first optical functional substrate surface. In the first optical functional substrate surface, a plurality of convex cylindrical lens element surfaces having parallel cylindrical axes are formed side by side, and the convex cylindrical lens element surfaces positioned directly adjacent to each other are: In each case, they merge with each other in the transition region.

  These transition regions can also be designed according to the claimed invention. The transition region can be configured as a concave cylindrical lens element surface that continuously merges with adjacent convex cylindrical lens element surfaces.

  The second substrate also has, if appropriate, a further cylindrical lens element array on the side opposite the first functional substrate surface, in which the cylindrical axis of the cylindrical lens element is on the opposite side. The cylindrical lens element extends parallel or perpendicular to the cylinder axis.

  There are various cases where the first substrate is processed to produce a first optically functional substrate surface having a non-concave transition region between the convex cylindrical lens element surfaces. As an example, the first substrate surface can be manufactured using a lithography pattern forming method. Thereby, the entire substrate surface including the convex cylindrical lens element surface and the transition region positioned therebetween can be guided to a desired shape.

  For example, using a processing tool that can be driven in a rotating manner and has concave sections that are positioned side by side to form convex cylindrical lens element surfaces that are positioned side by side and a transition region between the concave sections that will be described later. The first substrate surface can be patterned, and some or all of the transition regions have irregular surface shapes that differ in the direction in which adjacent recessed sections are located side by side. Thus, the processing tool can have a negative shape of the substrate surface to be manufactured in its working area provided for material removal.

  The substrate surface can be patterned using a material removal processing tool having a processing area having a width that is significantly smaller than the width of the transition region in the direction in which the convex cylindrical lens elements are located side by side. The machining tool can move at a uniform or non-uniform moving speed parallel to the direction in which the convex cylindrical lens elements are located side by side during the production of the transition region, and the descending depth of the machining tool is an irregular function Controlled according to. This also makes it possible to produce a random surface function within the transition region. Alternatively, move the machining tool at a uniform or non-uniform moving speed parallel to the direction of the cylinder axis without changing the descent depth, and then offset the machining tool laterally by about one machining width. (Adjacent to the direction in which the cylindrical lens element surfaces lie side by side) to create adjacent machining trajectories and alter the descent depth so that the desired surface profile is gradually produced during this lateral offset Is also possible.

  A combination of mechanical patterning and lithographic patterning can be used to pattern the substrate surface. Preferably, in this case, the convex cylindrical lens element surface is manufactured using a material removal processing tool, while the substrate surface in the transition region is patterned using a lithographic patterning method in advance, after, or simultaneously. . Generally, mechanical patterning is performed first, followed by lithographic patterning.

  These and further features will become apparent not only from the claims but also from the specification and drawings, wherein each individual feature is in each case an embodiment of the invention and in other fields as such. Alternatively, it can be achieved as a plurality in the form of partial coupling, and an advantageous and essentially protective embodiment can be constructed. Exemplary embodiments of the invention are illustrated in the drawings and are described in more detail below.

1 is a perspective view of a device for homogenizing laser radiation according to an embodiment of the present invention. FIG. FIG. 6 is a schematic view of a cross section through an integral substrate having a substrate surface patterned along a cross-sectional plane extending perpendicular to the cylinder axis. FIG. 6 is a schematic diagram of a variation of one method for manufacturing a patterned substrate. FIG. 3 is an enlarged detail view of a material removal rotation tool used for patterning purposes. FIG. 6 is a schematic diagram of another method variation for manufacturing a patterned substrate in which a rotating tool having a very small width is used. FIG. 3 is an illustration of an exemplary embodiment of a substrate with a transition region covered with a light opaque coating. FIG. 6 is an illustration of an exemplary embodiment in which a separate selective light shielding element for shielding the transition region is disposed upstream of the substrate. FIG. 6 is an illustration of an exemplary embodiment with a separate light deflection element disposed upstream of the substrate. 1 is a schematic diagram of a microlithographic projection exposure apparatus including an illumination system in which an embodiment of a multi-stage homogenizing device is arranged.

  Some aspects of the claimed invention are described below on the basis of a device for homogenizing laser radiation in the illumination field of an illumination system for a microlithographic projection exposure apparatus. The illumination system receives laser radiation in a primary laser radiation source, for example an excimer laser emitting in the deep ultraviolet region (DUV), on its incident side, and from this laser radiation into the object plane of the downstream projection lens Form illumination radiation incident on the illuminated pattern of the mask located. The projection lens images the illumination pattern of the mask onto an object to be patterned, such as a semiconductor wafer.

  Inside the illumination system, a device HOM for homogenizing the laser radiation shown in one embodiment shown in FIG. 1 is arranged in a state of being ready for operation, and the device HOM is configured so that the laser radiation is It contributes to homogenizing the laser radiation LR arriving from the laser radiation source so as to have as uniform an intensity distribution as possible in the illumination field ILF downstream of the device HOM. Located between the device HOM and the illumination field is a refractive Fourier optical unit FO that generates a Fourier transform for transforming the angular distribution of radiation at the output of the device HOM into a corresponding local distribution of radiation intensity in the illumination field. The illumination field ILF can be placed, for example, in a plane that is optically conjugate to the object plane of the downstream projection lens.

  The device 100 has a first substrate S1 through which the laser radiation LR can pass from the incident side in the direction of the illumination field ILF. Located at a distance D behind the first substrate is a second substrate S2 through which the laser radiation can pass in the direction of the illumination field after passing through the first substrate. Both substrates are made of a material that is transparent to laser radiation, for example calcium fluoride or synthetic quartz glass.

  The first substrate S1 has, on its incident side, a first optical functional substrate surface S1-1 in the form of a first cylindrical lens element array CLA1. The first cylindrical lens element array CLA1 is formed by arranging a plurality of convex cylindrical lens element surfaces CL having cylindrical axes parallel to each other in such a manner that they are positioned side by side on the first substrate surface. The cylindrical lens element surfaces are located side by side in the Y direction perpendicular to the cylindrical axis.

  FIG. 2 shows the first substrate parallel to the ZY plane so that the convex cylindrical lens element surface formed on the first substrate surface S1-1 is cut perpendicular to the cylinder axis or the vertex line thereof. A cross section through S1 is shown. Convex cylindrical lens element surfaces located directly adjacent to each other fuse in each case in the transition regions TR1, TR2, TR3, etc. In FIG. 2, the surface shapes of these transition regions are shown in an enlarged manner and will be described in more detail below.

  Another cylindrical lens element array is formed on the second substrate surface S1-2 of the first substrate S1 located opposite to the first substrate surface S1-1, and this array has cylindrical axes parallel to each other. A plurality of convex cylindrical lens element surfaces having the above are arranged side by side. The cylinder axes in this case extend perpendicular to the cylinder axis on the opposite radiation entrance side, i.e. parallel to the Y direction, and the cylindrical lens element surfaces are located side by side in the X direction. Also in this case, a narrow transition region is formed between the cylindrical lens element surfaces.

  The second substrate S1 has a similar structure. However, the cylindrical axis of the cylindrical lens element surface located on the light incident side facing the first substrate S1 is parallel to the Y direction, that is, the light incident side of the first substrate (first substrate surface S1-1). ) In the direction perpendicular to the cylindrical axis of the cylindrical lens element or parallel to the cylindrical axis of the cylindrical lens element on the light exit side (second substrate surface S1-2) of the first substrate S1. A narrow transition region is also formed between these convex cylindrical lens element surfaces.

  The second substrate surface S2-2 of the second substrate S2 located on the light emission side of the second substrate S2 is arranged in a manner that is positioned side by side and parallel to the X direction, that is, the second substrate surface S2-2. A plurality of convex cylindrical lens element surfaces having a cylindrical axis extending perpendicular to the cylindrical axis of the cylindrical lens element surface on the light incident surface of the substrate and parallel to the cylindrical axis of the cylindrical lens element surface on the light incident side of the first substrate S1 Is formed.

  When viewed in the radiation transmission direction (Z direction), in this case, the vertex line (center line) extending in parallel with the cylindrical axis of the convex cylindrical lens element surface on the first substrate surface S1-1 of the first substrate S1 is Align to the second substrate surface S2-2 of the two substrates. Further, the vertex line of the cylindrical lens element on the light emission side (second substrate surface S1-2) of the first substrate is aligned with that of the cylindrical lens element surface (S2-1) on the incident side of the second substrate. To do.

  In the case of this example, convex cylindrical lens elements parallel to each other on the light incident side (first substrate surface S1-1) of the first substrate and the light emitting side (second substrate) of the second substrate. The convex cylindrical lens elements parallel to each other in the plane S2-2) have the same radius of curvature and are located at a distance equal to the focal length in the Z direction (nominal radiation transmission direction) from each other. The radius of curvature of the cylindrical lens element surface on the light exit side S1-2 of the first substrate S1 is dimensioned so that its focal plane is located inside the second substrate. The radius of curvature of the convex cylindrical lens element surface on the light incident side S2-1 of the second substrate S2 is small, and the front focal plane thereof is dimensioned so as to be located in an area without material between the substrates. Other arrangements with other relative focal plane positions are possible.

  The laser radiation LR incident from the incident side of the device is divided into several partial beams located side by side in the Y direction by the convex cylindrical lens element surface on the first substrate surface S1-2 of the first substrate S1. The The second substrate surface S1-2, which extends perpendicular to the partial beam (ie in the Y direction) and through which the radiation passes next, results in a division corresponding to the X direction perpendicular to the Y direction. These partial beams are converted by the second substrate and the Fourier optical unit FO downstream in the direction of the illumination field ILF.

  Transition regions TR1 and TR2 between the convex cylindrical lens element surfaces on the first substrate surface S1-1 of the first substrate S1 pass through the transition region toward the illumination field ILF among the illumination intensities in the illumination field. The part is very small compared to the part passing through the convex cylindrical lens element surface, and furthermore, if the local distribution of this part in the illumination field is a variation in the beam distribution of the incident laser radiation LS, or temporary It is designed using special means so as to have a characteristic that it does not actually change in the case of a beam offset. Several means contribute to this design.

  First, the transition regions TR1 and TR2 are very narrow compared to the convex cylindrical lens element surfaces to be joined. Second, the surface shape in the transition region is that each transition region has a different surface shape, and this deviation in surface shape is generated due to the process instructions governed by manufacturing, and the optical surface Randomized in the sense that it exceeds the normal tolerances in the production of The surface shape is irregular in each case in the direction in which adjacent convex cylindrical lens element surfaces are positioned side by side, and as a result, has no cumulative lens element effect. Within the transition region, the surface shape is preferably not concave or continuously differentiable in some other way in the direction in which the joining cylindrical lens element surfaces lie side by side.

  In this case, the width W of the convex cylindrical lens element surface in the direction in which the cylindrical lens element surfaces are located side by side (the Y direction in FIG. 2) is the surface radius of the convex cylindrical lens element surface between the lines. And sometimes measured between lines that can be described analytically using a conic constant and yet another constant. In contrast, the transition region has a very small width WTR, which defines the width of the region where the transition region has a random surface shape that cannot be analytically described in that region. Preferably, the condition WTR <0.05 · W, particularly WTR <0.03 · W is satisfied.

  Very small widths such as transition regions TR1, TR2 can be explained by the ratio between the center-to-center distance or pitch PI between the vertex lines of the directly adjacent cylindrical lens elements and the width W of the convex cylindrical lens elements. it can. This ratio PI / W is preferably greater than 0.95 or greater than 0.98.

  Due to the small width of the transition region, the portion of the radiation that passes through the transition region toward the illumination field is very small from the beginning relative to the portion that passes through the convex cylindrical lens element surface. Furthermore, the surface shape of the transition region and thus its optical effect is randomized. As a result of the change in the surface shape in the transition region, essentially undesired external light occurring in the region of the transition region is mixed, so that the overall effect is locally attenuated. In this way, the transition region acquires a diffuse shielding function and what is achieved is that in the case of variations in the incident laser radiation, the intensity in the illumination field will still shift, but all contributions will shift equally. However, an excessive local increase in illumination intensity does not occur.

  This configuration is advantageous in the case of all the substrate surfaces that are incident on the outer region of the convex cylindrical lens element surface, that is, in a transition region where the radiation intensity is not so small. If the radiation is already split and shaped upstream of the substrate surface so that the laser radiation is only incident into the area of the convex cylindrical lens element surface, the means for randomizing the surface shape of the transition region is omitted. be able to. In this case, a conventional cylindrical lens element array can be used, and where appropriate, convex cylindrical lens element surfaces are formed in the transition region, and these surfaces are smooth to adjacent convex cylindrical lens element surfaces. To merge.

  In the arrangement of FIG. 1, for example, the transition region at the entrance surface S2-1 of the second substrate may be where the laser radiation is “seen” at all or very little. In this case, the transition region of the substrate surface does not need to be randomized and can have, for example, a concave shape.

  There are various possibilities for patterning the substrate surface such that a plurality of different surface shapes occur in the transition region during the manufacture of the optical component. A method variant in which a rotary tool TO1 having a polished outer surface ABR is used is described below with reference to FIG. This tool can be, for example, a grinding tool (abrasive surface with a granular abrasive with a non-geometrically determined cutting edge) or a milling tool (abrasive surface with a geometrically determined cutting edge). be able to. During processing, the rotary tool TO1 is rotated so that the substrate material is gradually removed using the polishing outer surface ABR until the desired surface shape of the substrate surface S1-1 having the required surface quality is generated. It rotates around the axis RA and is pressed by the outer surface ABR onto the substrate S1 to be processed with an appropriate pressing force. In this case, the rotation axis RA of the rotary tool extends parallel to the direction in which the convex cylindrical lens element surfaces to be manufactured are located side by side.

  The rotary tool is fed at a substantially constant feed speed parallel to the convex cylindrical lens element to be manufactured and the cylinder axis of the transition region. The polishing tool outer surface ABR of the rotary tool has a concave section CP arranged parallel to the rotation axis RA in a manner of being positioned side by side. The radius of curvature of the concave section predefines the radius of curvature of the convex cylindrical lens element surface on the substrate. Between the concave sections CP, a transition region TR located between the convex cylindrical lens element surfaces on the substrate is generated, and a narrow transition region TIP1 projecting outwardly defining its cross-sectional shape is located. As schematically shown in FIG. 3B, these outwardly projecting transition regions have different cross-sectional shapes so that the transition regions generated thereby also have different surface shapes. In general, the tool has a working width such that the entire substrate surface on which the substrate pattern is formed can be manufactured in a single work operation by a work movement that proceeds parallel to the cylinder axis. Thereby, different surface shapes can be defined in advance in each transition region.

  With reference to FIG. 4, another manufacturing method will be described in detail below. This manufacturing method is a modification of the contour milling operation in which a rotationally driven machining tool TO2 that rotates around a rotation axis at a predetermined rotation speed during machining is used. The processing tool TO2 has chip-shaped milling teeth TIP2 having a width of only a few micrometers measured parallel to the rotation axis RA on the outside in the radial direction. Its width at the radially outer edge can be, for example, less than 30% or less than 10% of the width of the transition region TR to be manufactured.

  During the production of a substrate surface from a blank or a rough prefabricated substrate, the rotating tool TO2 is a predefinable constant along the substrate surface, parallel to the direction in which the manufactured cylindrical lens element surfaces are located side by side. Alternatively, it is moved at a variable traveling speed. The downward movement (parallel to the Z direction) directed perpendicular to the movement in the direction of the substrate depends on the travel distance or speed so that a convex surface shape is produced in the region of the convex cylindrical lens element surface. It is controlled by the method. Within the transition region, the descending depth varies irregularly while proceeding uniformly so that an irregular surface shape is produced in the transition region. The downward movement during the processing of the transition regions can be predefined individually for each transition region or can be generated, for example, using a random generator inside the machine. This method can also produce a non-concave irregular surface shape in each transition region.

  Another variation involves a machining trajectory that progressively manufactures parallel to the cylinder axis (perpendicular to the drawing of FIG. 4). For this purpose, the rotating tool is moved over the entire length of the substrate parallel to the X direction without changing the descending depth. Thereafter, the tool and the substrate are offset in the Y direction relative to each other by an adjustment distance having approximately the same size as the working width of the narrow tool in the region of the cutting blade TIP2. Next, the next adjacent machining track is machined. The descending depth (z direction) is changed in accordance with the desired surface contour for each machining track.

  In another manufacturing method, the material removal for patterning the first substrate surface is performed by using a material removal processing tool having a polishing surface having a negative shape of the substrate surface, for example, using ultrasonic waves, This is achieved by utilizing the fact that a vibration parallel to the axis is formed and this vibration tool is pressed onto the substrate. It is also possible to process using mechanical collision.

  Referring to FIG. 5, after manufacturing the desired surface contour, the transition region TR5 between the convex cylindrical lens element surfaces of the first substrate surface S1-1 is substantially radiopaque to incident laser radiation. A description of an exemplary embodiment of the first substrate S1-1 modified in this manner is provided. For this purpose, after patterning, each transition region is covered with a relatively narrow coating CT with a transmission for laser radiation close to zero. The narrow coating covers only the transition area and does not extend into the plane of the adjacent convex cylindrical lens element. Thereby, radiation is prevented from passing through the transition region in the direction of the illumination field. That is, undesirable optical effects in the transition region are masked or masked.

  In the embodiment of FIG. 6, a separate radiation shielding optical element BLE is arranged upstream of the first substrate S1 in the radiation transmission direction (parallel to the Z direction) and this optical element from the first substrate surface S1-1. The distance in the direction of radiation transmission is very small, and should preferably be significantly smaller than the distance in the direction in which the cylindrical lens element surfaces between adjacent transition regions lie side by side. The selective radiation shielding optical element is made of a material that is highly transmissive to laser radiation, such as synthetic quartz glass or calcium fluoride, and is substantially perpendicular to the beam path and thus has no refractive effect. Can have the form of a plane parallel plate. The light shielding optical element has a light shielding band BL separated from each other and having a width substantially corresponding to the width of the transition region TR6 located immediately downstream of the optical path in a direction in which the cylindrical lens elements are located side by side. Incident laser radiation is shielded by this shielding region and therefore cannot pass into the transition region. Between the light shielding bands, the laser radiation can pass towards the convex cylindrical lens element surface without obstruction. Even with this method, the disturbance effect in the transition region can be removed by masking.

  In the embodiment of FIG. 7, a separate radiation deflection optical element DEV is arranged in the beam path upstream of the first substrate S1, which optical element has the form of a substantially transmissive parallel plane plate and the radiation is obstructed. Allows to pass in the direction of the cylindrical lens element surface without. This selective radiation deflecting optical element can be configured, for example, in a prism manner in a region upstream of the transition region TR7 of the first substrate S1 disposed downstream, and in the region of the adjacent cylindrical lens element surface. With a rerouting element or deflecting element DE that deflects incident radiation that would pass into the region of the downstream transition region without a lateral redirection to substantially without loss of light. This technique can also provide a device for uniformizing laser radiation that is relatively insensitive to laser fluctuations.

  The means described with reference to FIGS. 5 to 7 and variants thereof are in each case between the convex cylindrical lens element faces in order to prevent radiation from passing from the transition region towards the downstream illumination field. It can be used with corresponding advantages in conventional cylindrical lens element arrays having a narrow concave cylindrical lens element surface.

  FIG. 8 can be used for the fabrication of semiconductor components and other finely patterned components, to obtain fine resolution down to a fraction of a micrometer (DUV). 1 shows an example of a microlithographic projection exposure apparatus WSC that operates with light from or electromagnetic radiation from. In this example, the primary light source used is an ArF excimer laser having an operating wavelength of about 193 nm, and the linearly polarized laser beam is coaxial with the optical axis AX of the illumination system ILL. Combined.

  For example, an expanded laser beam having a divergence that can be between about 1 mrad and about 3 mrad includes a secondary light source in the pupil forming plane PUP of the downstream illumination system ILL including a plurality of optical components and groups. Or it enters into a pupil forming unit PFU designed to generate a defined local (two-dimensional) illumination intensity distribution, sometimes called an “illumination pupil”. The pupil forming surface PUP is a pupil surface of the illumination system.

  The pupil forming unit PFU has an adjustable pupil definition unit PDE which gives the beam path of the expanded laser beam a specific angular distribution that can be pre-defined by settings for the incoming laser radiation. The pupil definition unit PDE can include, for example, one or more diffractive optical elements or controllable multi-mirror arrays. The downstream first optical system SYS1 introduces a Fourier transform in order to convert the generated angular distribution into a spatial distribution in the pupil plane PUP.

  The pupil forming unit PFU is variably set so that different local illumination intensity distributions (ie differently structured secondary light sources or different illumination settings) can be set in a manner that depends on the drive of the pupil forming unit. can do. This local illumination intensity distribution includes, for example, a conventional setting with a central circular illumination spot and a pre-determinable sigma value, or a pole setting such as dipole or quadrupole illumination.

  Near the pupil forming surface PUP, a field definition element FDE including an embodiment of a device HOM for homogenizing laser radiation is arranged.

  The second optical system SYS2 arranged downstream transfers the light to the rectangular illumination field on the mask M through an odd number of Fourier steps. The mask M or the reticle is arranged on the object plane OS of the downstream projection lens PO, and this object plane is also called a reticle plane.

  The second optical system may be a single Fourier optical unit that generates only one Fourier transform. In another embodiment, there is also an intermediate field plane located between the pupil plane PUP and the plane of the mask M, which is adjustable to clearly define the field boundary on all sides. A reticle / masking system is arranged that functions as a field stop. This field plane is then imaged onto the plane of mask M using yet another imaging system (sometimes referred to as a REMA lens).

  The field definition element FDE fulfills several functions. First, the incident radiation is shaped to illuminate a rectangular illumination field having a predetermined size after passing through a second optical system SYS2 downstream in the region of the mask and / or optical intermediate field plane. Secondly, the radiation is now uniformized so that the illumination field is illuminated as uniformly as possible.

  In the second optical system SYS2, each beam angle at the exit of the field definition element FDE corresponds to a specific location in the reticle plane OS, while on the other hand, the position of the point in the field definition element FDE, ie, relative to the optical axis AX. That position has the effect of determining the illumination angle of the reticle plane. The beams of light emanating from the individual channels are in this case superimposed in the field plane.

  The projection lens PO functions as a reduction lens, and forms an image of a pattern arranged on the mask M on a wafer W covered with a photoresist layer at a reduction scale, for example, a scale of 1: 4 or 1: 5. The photosensitive surface of the wafer is located in the image plane IS of the projection lens PO. Refractive, catadioptric, or reflective projection lenses are possible. Other reduction scales are possible, for example, reduction ratios as great as 1:20 or 1: 200.

  The pupil forming surface PUP is positioned at or near an optically conjugate position with respect to the image side pupil surface of the projection lens PO. As a result, the spatial (local) light distribution in the pupil PUP of the projection lens is determined by the spatial light distribution (spatial distribution) in the pupil forming surface PUP of the illumination system. Between the pupil planes, in each case, a field plane that is a Fourier transformed plane for each pupil plane is located in the optical beam path. This means in particular that the defined spatial distribution of the illumination intensity in the pupil forming plane PUP corresponds to a specific angular distribution of illumination radiation incident in the illumination field on the reticle M.

  As can be seen in another view of the pupil forming unit PFU, the lateral beam offset LAT at the entrance of the optical system SYS causes an angular error ANG in the downstream pupil forming plane PUP. The claimed invention makes it possible to generate a homogenization effect of the field-forming element FDE which is less dependent on such fluctuations of the incident laser radiation.

  In the exemplary embodiment of FIG. 1, the cylindrical axes of the cylindrical lens element arrays arranged one behind the other are Y, X when “Y” and “X” represent the orientation of the cylindrical axes in the Y direction and the X direction. , X, Y in this order. Other orders are possible, such as Y, Y, X, X, or X, X, Y, Y, or X, Y, Y, X, etc.

  A homogenization device of the type shown in this figure can be placed elsewhere in the illumination system. As an example, the arrangement of the homogenizing device and pupil forming elements can be reversed with respect to that in FIG.

PI center-to-center distance S1 first substrate S1-1 first optical functional substrate surface S1-2 second substrate surfaces TR1, TR2, TR3 transition region W width of convex cylindrical lens element surface WTR region having a random surface shape Width of

Claims (19)

A first substrate (S1) that allows laser radiation (LR) to pass in the direction of the illumination field (ILR) from the incident side;
The first substrate has a first optical functional substrate surface (S1-1);
In the first optical functional substrate surface (S1-1), a plurality of convex cylindrical lens element surfaces having cylindrical axes parallel to each other are formed in such a manner that they are positioned side by side.
Convex cylindrical lens element surfaces located directly adjacent to each other fuse together in the transition region (TR),
A device for homogenizing laser radiation in an illumination field,
The portion of the illumination intensity in the illumination field (ILF) generated by the plurality of the transition regions is small compared to the part of the illumination intensity generated by the convex cylindrical lens element surface in the illumination field, and in the illumination field The plurality of transition regions (TR) are designed such that the local distribution of this portion is substantially independent of variations in the laser radiation incident in the device.
A device characterized by that. The device according to claim 1, characterized in that the plurality of transition regions (TR1, TR2, TR3) have different irregular surface shapes in directions in which the adjacent convex cylindrical lens element surfaces are located side by side. Each of the plurality of transition regions (TR1, TR2, TR3) has a different surface shape in the direction in which the adjacent convex cylindrical lens element surfaces are positioned side by side, and the surface shape is preferably irregular. The device according to claim 1, wherein the device has a surface shape. The plurality of transition regions (TR1, TR2, TR3) have a random distribution of different surface shapes in the direction in which the adjacent convex cylindrical lens element surfaces are positioned side by side, and the different surface shapes are preferably The device according to claim 1, wherein the device is irregular or concave. The plurality of transition regions (TR1, TR2, TR3) have a non-concave shape in the direction in which the adjacent convex cylindrical lens element surfaces are positioned side by side with each other. The device according to claim 1. The plurality of transition regions (TR1, TR2, TR3) have a width (W) of 5 (W) of the convex cylindrical lens element surface joined in this direction in the direction in which the adjacent convex cylindrical lens element surfaces are positioned side by side. And / or the plurality of transition regions are joined to the direction in which the adjacent convex cylindrical lens element surfaces are located side by side in this direction. Having a width less than 5% of the center-to-center distance (PI) between the faces, in particular less than 3% of this center-to-center distance;
The device according to claim 1, wherein the device is a device. The plurality of transition regions (TR1, TR2, TR3) have a width smaller than 30 μm in the direction in which the adjacent convex cylindrical lens element surfaces are located side by side, and the width is preferably 15 μm or more. The device according to claim 1, characterized in that it is less than 10 μm or less. The plurality of transition regions are substantially light opaque, and the substrate surface preferably carries a light opaque coating (CT) in the transition region (TR5). The device according to claim 7.   9. The convex cylindrical lens element according to any one of claims 1 to 8, wherein the convex cylindrical lens element has a uniform distance between apex lines in the direction in which the concave cylindrical lens elements are located side by side. Devices. A second substrate (S2) that allows the laser radiation to pass from the incident side in the direction of the illumination field;
The second substrate has at least one optical functional substrate surface (S2-1),
In the at least one optical functional substrate surface (S2-1), a plurality of convex cylindrical lens element surfaces having parallel cylindrical axes are formed side by side,
Convex cylindrical lens element surfaces located directly adjacent to each other fuse together in the transition region,
The device according to claim 1, wherein the device is a device.   The second substrate (S2) is arranged such that the laser radiation transmitted by the first substrate (S1) can pass from the incident side in the direction of the illumination field of view (ILR). Device according to claim 10, characterized in that it is arranged at a distance behind the substrate (S1). A method of manufacturing a substrate through which laser radiation can pass, in particular for a device for homogenizing laser radiation in an illumination field, comprising:
The substrate has a first optical functional substrate surface (S1-1);
In the first optical functional substrate surface (S1-1), a plurality of convex cylindrical lens element surfaces having cylindrical axes parallel to each other are formed in such a manner that they are positioned side by side.
Convex cylindrical lens element surfaces located directly adjacent to each other fuse together in the transition region (TR),
The first optical functional substrate surface is formed by using a processing tool having concave sections positioned side by side to form a transition region between the convex cylindrical lens element surface positioned side by side and the concave section described later. Patterned and the transition region has a different surface shape in the direction in which the adjacent convex cylindrical lens element surfaces are located side by side, preferably a surface shape shaped according to an irregular and / or random distribution,
A first substrate having a first optically functional substrate surface according to any one of claims 1 to 10 is manufactured by this method.
A method characterized by that.   The method of claim 12, wherein the first optically functional substrate surface is manufactured using a lithographic patterning method.   The convex cylindrical lens element surface of the first optical functional substrate surface is manufactured using a material removal processing tool, and the substrate surface is patterned using a lithography pattern forming method in the transition region. The method according to claim 13.   The substrate surface is patterned using a material removal processing tool having a processing area having a width that is significantly smaller than the width of the transition region in the direction in which the convex cylindrical lens elements are located side by side. The method according to any one of claims 12 to 14. A first substrate (S1) capable of passing laser radiation in the direction of the illumination field from the incident side;
The first substrate has a first optical functional substrate surface (S1-1);
In the first optical functional substrate surface (S1-1), a plurality of convex cylindrical lens element surfaces having cylindrical axes parallel to each other are formed in such a manner that they are positioned side by side.
Convex cylindrical lens element surfaces located directly adjacent to each other fuse together in the transition region,
A device for homogenizing laser radiation in an illumination field,
A plurality of the transition regions (TR1, TR2, TR3) have a random distribution having different surface shapes in directions in which adjacent convex cylindrical lens element surfaces are located side by side.
A device characterized by that. The device of claim 16 , wherein the different surface shapes are irregular or concave. An illumination system for a microlithographic projection exposure apparatus for illuminating an illumination field with light from a primary light source,
A device according to any one of claims 1 to 11 or 16 to 17 ;
An illumination system characterized by A variably adjustable pupil forming unit for the illumination system to receive light from a primary light source and to generate a variably adjustable two-dimensional intensity distribution in a pupil forming plane (PUP) of the illumination system (PFU)
The homogenization device (HOM) is disposed in a region of the pupil forming surface;
The illumination system according to claim 18 .

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