KR20080012240A - ILLUMINATION SYSTEM FOR A PROJECTION EXPOSURE APPARATUS WITH WAVELENGTHS <= 193 nm - Google Patents

Abstract

A illumination system for a projection exposure apparatus having a wavelength not more than 193 nm is provided to adjust uniformity of illumination of a field in a field plane by including a size adjusting apparatus for adjusting first and second regions of field raster devices. An optical device is disposed on a plane in a light path from an optical source(1) to a field plane, including a plurality of field raster devices(5). Illumination is supplied to the plane, and only a first region of at least one of the plurality of field raster devices in the plane is illuminated while a second region of the field raster device is not illuminated. A size adjusting apparatus adjusts the size of the first and second regions of the field raster devices so that the uniformity of the illumination of a field in the field plane is adjusted. The field can have a first shape, and the field raster device can have a second shape wherein the first shape generally agrees with the second shape.

Description

ILLUMINATION SYSTEM FOR A PROJECTION EXPOSURE APPARATUS WITH WAVELENGTHS ≤ 193 nm}

The present invention relates to an illumination system and a projection exposure apparatus for a projection exposure apparatus having a wavelength of 193 nm or less, preferably 126 nm or less, in particular 100 nm or less, and the uniformity of illumination in the field plane and the illumination inside the exit pupil. A method for controlling ellipticity and telecentricity is described.

Lighting systems for microlithography with a wavelength λ of 193 nm or less are known in many publications.

In order to be able to reduce the structure width of electronic devices, particularly in the sub-micrometer range, it is desirable to reduce the wavelength of the light used. In this case, the use of light having a wavelength of 193 nm or less, in particular the use of lithography using soft X-rays and referred to as so-called Extreme Ultraviolet (EUV) lithography, is proposed.

EUV lithography is currently discussing wavelengths in the range from 10 to 30 nm, in particular from 11 to 14 nm, in particular from 13.5 nm. The image quality of the EUV lithography is determined on the one hand by the projection objective and on the other hand by the illumination system. The illumination system should illuminate the field as uniformly as possible in the field plane in which the mask supporting the structure, the so-called reticle, can be placed therein. By the projection objective, the field in the field plane is transferred to the image plane, also referred to as the wafer plane. Light sensitive objects, such as wafers, are disposed in the image plane.

In the case of a system operating with EUV light, the optical elements are formed as reflective optical elements, in particular as mirrors. The shape of the field in the field plane of the EUV lighting system typically has the shape of a ring field.

Projection exposure apparatuses in which the illumination systems are used in the same way as in the present invention are generally operated in a so-called scanning mode. Lighting systems for EUV lithography and projection exposure apparatuses with lighting systems of this type are disclosed in US Pat. No. 6,452,661, US Pat. No. 6,198,793 or US Pat. No. 6,438,199. The aforementioned EUV lighting systems include so-called honeycomb condensers for adjusting the Etendue, illuminating the field uniformly in the field plane and illuminating the pupil as defined in the pupil plane. The honeycomb concentrators are generally two facetted optical elements, a first faceted optical element with a plurality of field raster elements and a second facet type with a plurality of pupil raster elements. It includes an optical element.

In WO 2002/27401 a double-facetted illumination system is known, in which only a wide range of fully illuminated field raster elements are transferred to the field plane.

US 6,771,352 discloses a lighting system in which individual field raster elements can be completely blocked by a light barrier. A method of partially blocking one field raster element is also described in US Pat. No. 6,771,352, but for this purpose the light barriers known in US Pat. No. 6,771,352 always partially transmit light. Let's do it. The disadvantage of this approach is that no clearly defined boundary is formed between the irradiated and unirradiated portions of one field raster element.

Clear boundaries are an advantage, especially if the uniformity to be corrected varies significantly. By intentionally setting the position of the boundary, the correction can have a relatively strong effect in a particular area or in one particular place of the field in which the boundary is formed. Strong fluctuations in uniformity occur, for example, when the illumination of field raster elements has locally limited strong fluctuations. Such fluctuations can occur due to shadows projected by, for example, the supporting spokes of the collector disposed in the light path in front of the optical element with field raster elements. Collectors with spokes for supporting individual collector shells are disclosed, for example, in EP 1354325.

WO 2005/015314 discloses that an attenuator, in particular filter elements, is arranged in a plane conjugated to the field plane or in order to improve the illumination uniformity of the field in the field plane. Double faceted lighting systems are known which are arranged in close proximity. According to WO 2005/015314, the filter elements are assigned to individual facets of the first faceted element. In this way, it is possible to influence the light intensity inside each individual light channel assigned to one side of the first faceted element.

The disadvantage in the system known from WO 2005/015314 was a complicated configuration. Another disadvantage of the above-mentioned systems according to the prior art is that only field raster elements that are broadly fully illuminated as described in WO 02/27401 in order to reach as uniform as possible in the field plane, i. It was a fact that it is a warrior. However, in the case of illumination in a circular manner, more than 20% of the light emitted from the light source into the plane in which the field raster elements are arranged is not available by the illumination system.

Disadvantages in US Pat. No. 6,400,794, where half-illuminated facetts were also used, were the centroid and elliptic errors within the exit pupil of the lighting system. In the case of a double faceted illumination system, one optical channel is formed as a result of the mutual assignment between the field raster element and the pupil raster element. As such, non-uniform illumination of the first faceted optical element with field raster elements results in non-uniform illumination of the second faceted optical element with pupil raster elements. As a result of such non-uniform illumination, the above-described center of gravity error and ellipticity error appear. Thus, in the prior art, there has been provided an illumination system in which the utilization of the light emitted from the light source is insufficient or an excessively large center-of-center error and elliptic-error error occur.

In the case of the present application, uniform illumination within the field plane of the illumination system means that the difference between the scan integrated minimum and maximum energy (ΔSE), the so-called uniformity error, falls below a predetermined value above the field height. will be. For the uniformity error ΔSE expressed as a percentage, the following equation applies:

The term "far center error" in the present application means, for example, the deviation between the center of the circular exit pupil and the intersection of the center ray in the exit pupil plane.

The term "ellipticity" refers to a weight factor that characterizes the energy distribution inside the exit pupil. If the energy is uniformly distributed throughout the angular range inside the injection pupil, the ellipticity will have a value of 1. The term "ellipticity error" refers to an ideal uniform distribution, that is, a deviation of the ellipticity of a value of 1 from a specific ellipticity.

The object of the present invention is to overcome various shortcomings of the prior art, in particular characterized by low uniformity error, ellipticity error and center of gravity error while at the same time having low light loss, i.e. the low uniformity error, ellipticity error and It is to provide an illumination system for wavelengths below 193 nm that combines properties such as raw center error with high light yield.

The problem is solved by an illumination system with a light source which emits light rays having a wavelength of 193 nm or less according to the invention, in which case the illumination system has a first having field raster elements in the plane in which the first illumination is provided. A facet type optical element, wherein at least a portion of the field raster elements in the plane is not fully illuminated, and an apparatus is provided for adjusting illumination of the not fully illuminated field raster elements, in which case The illumination control device may adjust the uniformity of the second illumination of the field in the field plane. In the present application, the term "not fully illuminated" means that the area of one raster element is preferably less than 95%, more preferably less than 90%, even more preferably less than 85%, even more Preferably less than 80%, even more preferably less than 75%. In one field facet that is not fully illuminated or one field raster element that is not fully illuminated, only the first area of the field facet is illuminated. According to the invention, for example, light is blocked by a light barrier, so that the second region of the field raster element does not actually receive light. That is, they are completely shielded from light overall. For example, if one field raster element is illuminated at 50%, the first illuminated area fills 50% of the total area of the field raster element, the second unilluminated portion and the dark of the field raster element The portion likewise fills 50% of the total area of the field raster element.

In particular, the present invention provides an illumination system for a projection exposure apparatus having a wavelength in the range of 193 nm or less, preferably 126 nm or less, more preferably 30 nm or less, even more preferably 10 nm to 30 nm. In this case the light of the light source is directed to the field plane along the light path, which comprises an optical element disposed after the light source in the light path from the light source in the plane to the field plane and having a plurality of field raster elements. Wherein the plane is provided with illumination, and at least one field raster element having a plurality of field raster elements is illuminated only in the first area in the plane, not in the second area, There is an apparatus for adjusting the size of the first and second regions, in which case the image is adjusted by the size adjusting device. Field of the field in the field plane can be controlled uniformity of illumination.

In the apparatus according to an embodiment of the present invention, the mechanical configuration is very simple, since only the illumination of each side of the partially illuminated field is varied to adjust the uniformity. Thus, for example, only a light barrier fixed at the edge is sufficient, so that the mechanical elements do not protrude into the light path, resulting in no shielding. In addition, such a light barrier system also allows the introduction of light originating from the light path.

In a particularly preferred case, the uniformity error is better than ± 5%, specifically better than ± 2%, more specifically better than ± 0.5% and / or the scan-integrated ellipticity depends on the x-position, That is, within the range of 1 ± 0.1, specifically 1 ± 0.05, more specifically 1 ± 0.02, depending on the field height in the field to be illuminated. In another preferred case, the illumination system is characterized by a low center of gravity-error, wherein the center of gravity-error is ± 2.5 mrad, in particular ± 1.5 mrad, depending on its position in the field, ie field height. More specifically, the error does not exceed ± 0.5 mrad. The energy of the light source entering the plane in which the field raster elements are arranged must be received by the field raster elements by 70% or more, specifically 80% or more, more specifically 90% or more.

Preferably the field in the field plane has a first shape, the field raster elements have a second shape, the first shape generally coinciding with the second shape. In the case where the shape of the field is arcuate, the field raster elements also preferably have an arc shape, as described, for example, in US Pat. No. 6,195,201.

If the field raster elements have the shape of the field to be illuminated, the field raster elements can be arranged in columns and rows on the carrier structure of the faceted optical element, in which case the rows are preferably described in US Pat. No. 6,452,661. As is not offset from each other in order to be able to compactly fill the arc-shaped sides.

If the field raster elements are arranged in columns and rows, the plurality of field raster elements is preferably integrated into blocks.

Preferably the illumination control device comprises at least one light barrier, in which case the light barrier is preferably assigned to a field raster element that is not fully illuminated. Alternatively, multiple field facets may be assigned to one light barrier, especially if the field facets and the corresponding light barriers have very small dimensions.

If an illumination system is used in the scanning-projection exposure apparatus, the field will have one unique direction, the scanning direction, also referred to as the y-direction. In that case, the light barrier (s) are actually formed to be movable perpendicular to the scanning direction. As the light barrier (s) actually move perpendicularly to the scanning direction, ie in the x-direction, light, ie energy, can be removed or added from the field as intended according to the field height x. As such, the uniformity of illumination in the field plane can be affected by the field height.

The illumination control device may include a plurality of wires for attenuating light as an alternative to the light barrier. An optical attenuator of this type is disclosed, for example, in EP 1291721. If the adjustment is carried out by the wire, for example the wire is moved so that the shadow of the wire obscures certain areas on the field sides. Further lighting control devices are devices which can for example deform and / or tilt any optical element arranged in the light path from the light source to the field plane. Possible elements are collectors or spectral filters or additional mirrors. One further possibility is a light barrier disposed behind the collector, ie on the outlet side of the collector, in the light path from the light source to the field plane. In order to vary the illumination of the partially illuminated field facets, the entire optical element with field facets, ie the field facet plate, can also be moved.

By means of a movable control device such as a light barrier that can be assigned to individual field sides, for example, the uniformity error (ΔSE) of the field illumination is less than 10%, specifically 5% or less, more specifically 2% or less. Can be reached. For example, the remaining uniformity error of 2% is actually caused by depletion of the coating during operation, thermal deformation of the optical elements, or replacement of the optical elements or light source.

One advantage of the present invention is that the uniformity of the lighting system can be continuously adjusted, especially with the help of an adjusting device, so that even if the illumination in the field plane changes over time due to variations in the lighting system, the specified uniformity The error does not exceed. Such a case may be a case where the illumination is changed due to, for example, a spatial and temporal positional variation of the light source. Such spatial and / or temporal positional variation of the position or emission intensity of the light source is also referred to as the "jitter" of the light source. According to an improvement of the invention, the illumination of partially illuminated areas is controlled by one or a number of field raster elements so that the specified uniformity error can be reached continuously without changing the structure of the parts of the present lighting system. It becomes possible.

In addition, alteration of the spectral intensity distribution of the light source can also alter the illumination. Thus, the reflectance of one optical element typically depends on the wavelength of the irradiated light. As such, the wavelength variations cause variations in reflectance and, in addition, variations in illumination.

Replacing one optical element in the light source or illumination beam path can also alter the fluctuations of the illumination, in particular the uniformity of the illumination in the field plane. Uniformity errors caused by replacement can also be corrected by intentionally shielding only partially illuminated field faces by the device according to the invention.

The lighting properties of the present lighting system can also be varied by the consumption of the coating occurring during operation or by the deformation due to the heat of the optical elements. Even if the illumination changes in this way, the uniformity error can be compensated by the adjusting device according to the invention.

According to the present invention, even when the illumination fluctuates due to, for example, replacement of the optical elements, thermal deformation of the optical elements, and spatial and temporal fluctuations of the light source, the uniformity error is continuously below the uniformity error specified by the adjusting device. It provides a lighting system that can be maintained. Thus, according to the invention, the uniformity error can always be kept below a certain limit, for example below 5%, in particular 2% even when the illumination fluctuates over time.

In one alternative embodiment of the present invention, rather than movable adjustment devices such as, for example, light barriers, rather than fully illuminated field raster elements are arranged in the field plane on the carrier structure of the first faceted optical element, The field illumination of the field will have some uniformity error in the range of 5% or less, in particular 2% or less.

Preferably, the first illumination has an annular shape in the plane where the first faceted optical element is disposed.

Particularly preferably the lighting system is a dual faceted lighting system with first and second faceted optical elements as described, for example, in US Pat. No. 6,438,199 or US Pat. No. 6,198,793. The second faceted optical element is disposed after the first faceted optical element in an optical path from the light source to the field plane. The second faceted optical element comprises a plurality of pupil raster elements. An optical channel is formed between one field raster element and one pupil raster element, respectively. Since the arrangement of the pupil raster elements determines the light distribution within the exit pupil, the so-called exit pupil plane, for example, by appropriately assigning the not fully illuminated field raster elements to certain pupil raster elements distributed symmetrically around the center. The pupil illumination condition within can be adjusted, in which case the pupil illumination in the exit pupil plane of the illumination system is better than ± 2 mrad, preferably better than ± 1 mrad, more preferably better than ± 0.5 mrad It has a center of gravity.

According to one embodiment of the invention, the field raster elements are arranged in a pupil raster such that the pupil illumination in the exit pupil of the illumination system has an ellipticity in the range of 1 ± 0.10, preferably 1 ± 0.05, more preferably 1 ± 0.025. Assigned to the devices.

In addition to the above illumination system, the present invention also provides a projection exposure apparatus comprising a projection objective lens and an illumination system for transferring an object illuminated in the field plane by the illumination system to the image plane.

Also, uniformity, circle of illumination system with illumination in one plane on which the first faceted optical element with field raster elements is disposed, and field in one field plane with field illumination and pupil illumination in the exit pupil Methods for controlling the center rate and ellipticity are presented. According to the method, the illumination control in the plane in which the field raster elements are arranged is such that the uniformity error ΔSE of the field illumination of the field is 5% or less, in particular 2% or less. Each field raster element is then assigned a pupil raster element of the second optical element, forming an optical channel, in which case the assignment is a circle of ± 1 mrad, preferably ± 0.5 mrad in one exit pupil plane. A pupil illumination having a center rate deviation and / or ellipticity in the range of 1 ± 0.1, more preferably 1 ± 0.05, even more preferably 1 ± 0.02 is used.

All of the above-mentioned illumination systems preferably allow light of a light source in the plane of the first faceted optical element provided with the first illumination to be at least 70%, in particular at least 80%, in particular 90% by means of field raster elements It is characterized by being accommodated to the above, because the field raster elements also receive light that is not fully illuminated.

The apparatus for adjusting illumination is preferably a system consisting of a light barrier that can be moved in one direction perpendicular to the scanning direction.

In order to be able to adjust the assignment of the field raster element to the pupil raster elements, the field raster elements can be arranged on one carrier at an inclination angle which can be varied by the actuator. Thus, the assignment of field raster elements to pupil raster elements can then be adjusted.

The projection exposure apparatus according to the invention is suitable for manufacturing microelectronic components, in which case the structured mask is transferred to a photosensitive layer in the image plane of the projection objective. The shape of the structured mask is developed while forming a portion of the microelectronic component.

The invention is explained in detail below with reference to the drawings.

1 shows a beam path in a refractive illumination system with two faceted optical elements, also referred to as a dual faceted illumination system, to illustrate the basic principle. In reflective systems for EUV wavelengths in the range of 1 to 20 nm only reflective optical elements are used, for example reflective mirror facets are used as field facets of the first faceted optical elements. The light of the primary light source 1 is collected by the collector 3 and converted into parallel or converging light bundles. The field facets or field raster elements 5 of the first faceted optical element 7 decompose the light beam 2 incident from the light source 1 into a plurality of light beams 2.1, 2.2, 2.3, A secondary light source 10 is formed at or near the second faceted optical element 11. The plane on which the first faceted optical element 7 rests is referred to as the first plane 8. In the embodiment shown, the second facet type optical element 11 lies therein, and in this embodiment the second plane 13, which is also formed therein up to the secondary light source 10, is the exit pupil of the lighting system. A plane that is conjugated to a plane. The field mirror 12 transfers the secondary light source 10 to an exit pupil (not shown) of the illumination system, which coincides with the entrance pupil of the subsequent projection objective not shown. The field raster element 5 is transferred to the field plane 14 of the illumination system via the pupil raster element 9 and the optical element 12. Preferably, the field plane 14 of the lighting system is arranged with a structured mask, a so-called reticle. The field raster elements shown in FIG. 1 and the field raster element 20 and the pupil raster element 22, wherein the optical channel 21 is formed therebetween, will now be described with reference to FIGS. 2A and 2B. The purpose of the pupil raster elements will be described. In this case, the field raster element 20 and the pupil raster element 22 are again shown as refractive elements, but are not limited to the refractive elements. Rather, such refractive elements may be an example for reflective elements.

The field raster element 20 is transferred by the pupil raster element 22 and the optical element 12 to the field plane 14 of the illumination system in which a field of a predetermined structure and shape is illuminated therein. The field plane 14 is arranged with a reticle or a structured mask. In general, the structural expansion of the field raster element 20 determines the shape of the field illuminated in the field plane.

One example is shown in FIG. 6 for a field illuminated in a field plane having a shape as formed inside a ring field-scanner, for example.

In the first embodiment of the present invention, the field raster element 20 may have a field shape. In other words, for example, if the field is ring-shaped, the field raster elements will likewise have a ring-shaped shape. Such content is described, for example, in US Pat. No. 6,452,661 or US Pat. No. 6,195,201, the contents of which are hereby incorporated in their entirety by reference.

As an alternative to the ring shape, the field raster elements can have a rectangular shape. In order to illuminate an arc-shaped field in the field plane, if the field raster elements are rectangular, for example, as described in US Pat. No. 6,198,793, the rectangular field is deformed into an arc-shaped field by a field mirror, for example. Need to be.

In systems with arc-shaped raster elements, no field mirror is needed to illuminate the ring field in the field plane. The field raster element 20 is designed such that an image of the primary light source 1, the so-called secondary light source 10, is formed at or near the location where the pupil raster element 22 is located. In order to avoid excessively high heat loads being applied to the pupil raster element 22, the pupil raster elements may be defocused relative to the secondary light source.

Secondary light sources are expanded because of the defocusing. The expansion can also be caused by the shape of the light source.

In one preferred embodiment of the present invention, the shape of the pupil raster elements may be matched to the shape of the secondary light source.

As shown in FIG. 2B, the optical element 12 projects the secondary light source 10 to the exit pupil plane 26 of the illumination system, in which case the exit pupil enters the projection objective lens at the exit pupil plane 26. Coincides with the pupil. In the exit pupil plane 26, a third light source, so-called sub-pores, is formed for each of said secondary light sources. This is illustrated in FIG. 8.

3 shows the shape of a reflective projection exposure apparatus with an illumination system according to the invention, such as used for EUV lithography. All optical elements are reflective optical elements, ie mirrors, such as field face mirrors. In the present embodiment, the light beam of the light source 101 is converged by grazing incidence collector mirror 103 formed as a mesh collector mirror with a plurality of mirror shells, and the spectrum in the grating spectral filtering element 105. After filtering it is directed towards the first faceted optical element 102 with field raster elements with an intermediate image of the light source. The light source 101, the collector mirror 103 and the grating spectral filter 105 form one so-called light source unit 154. The first faceted optical element 102 with field raster elements forms a secondary light source at or near the location of the second faceted optical element 104 with pupil raster elements. The first faceted optical element 102 is disposed in the first plane 150, and the second faceted optical element 104 is disposed in the second plane 152. In the general case, since the light source is an expanded light source, the secondary light sources are also expanded. In other words, each secondary light source has a predetermined shape. As described above, the individual pupil raster elements can be adjusted to the predetermined shape of the secondary light source.

The pupil raster elements, together with the optical elements 121, are used to transfer the field raster elements to the field plane 129 of the illumination system, in which even the mask 114 supporting the structure can be placed therein. For example, field field illumination of one field is used as the field plane, as shown in FIG. 6.

The spacing D between the first faceted optical element 102 and the second faceted optical element 104 is shown in FIG. 3, running from the first optical element 102 to the second optical element 104. And is defined along the main beam CR passing through the center field point Z.

To each field raster element of the first facet type optical element 102, a pupil raster element of the second facet type optical element 104 is assigned, as shown in Figs. Between each field raster element and each pupil raster element a beam of light extends from the field raster element to the pupil raster element. The individual light beams traveling from the field raster element towards the pupil raster element are referred to as so-called optical channels.

Also shown in FIG. 3 is the exit pupil plane 140 of the illumination system, which coincides with the incident pupil plane of the projection objective 126. The exit pupil plane is defined by the intersection S of the main beam CR passing through the central field point Z of the ring field shown as an example in FIG. 6 across the optical axis OA of the projection system 126. Is defined by point. In the exit pupil plane 140, pupil illumination is formed.

One example of an exit pupil of an illumination system as shown in FIG. 3 with a pupil illumination is shown in FIG. 8.

Projection system or projection objective 126 has six mirrors 128.1, 128.2, 128.3, 128.4, 128.5, 128.6 in the illustrated embodiment. The structured mask is transferred by the projection objective onto the image plane 124 on which the photosensitive object is disposed.

In FIG. 3 a local x, y, z-coordinate system is shown in the field plane 129 and a local u, v, z-coordinate system is shown in the exit pupil plane 140.

Figure 4a shows a two-dimensional arrangement of field raster elements according to the prior art, in which less than 70% of the light incident from the light source is received by circular illumination and used to illuminate the field in the field plane. . Each of the reflective field faces 309 is disposed on a first faceted optical element, so-called field honeycomb plate, indicated by reference numeral 102 in FIG. 3. 4A shows a possible arrangement of 178 field raster elements 309 on a field honeycomb plate according to the prior art. Circle 339 indicates the exterior illumination boundary of the circular illumination of the first optical element with field raster element 309. In practice the rectangular field raster element 309 has, for example, a length X _FRE = 43.0 mm and a width Y _FRE = 4.00 mm. All field raster elements 309 are fully illuminated because they are disposed in circle 339. As can be seen from FIG. 4A, a large portion of light impinging on the field mirror is not used. Circle 341 indicates an interior illumination boundary caused by, for example, the intermediate light barrier of the reticulated collector.

4B to 4D show an arrangement of first faceted optical elements according to embodiments of the present invention.

FIG. 4B shows the state of a total of 312 field facets arranged on the first faceted optical element, indicated at 102 in FIG. 3. Each face of each field is indicated by reference numeral 311. Field honeycombs of the individual last elements 311 are fixed on a carrier structure (not shown) of the first faceted optical element. As can be seen in FIG. 4B, as a planar light in which the first faceted optical element is disposed, an annular light having an outer light boundary 341.1 and an inner light boundary 341.2 is dealt with. The raster elements are also subdivided into four columns (343.1, 343.2, 343.3, 343.4) and a few rows 345 in total. The raster elements 311 of the individual rows are arranged directly up and down in each column, whereas the field facets are offset in different rows in FIG. 4A. The individual facets are also concentrated in blocks 347 arranged up and down. The blocks and rows are each separated from each other by space 349. FIG. 4B also shows shadows 351.1, 351.2, 351.3, 351.4 of the supporting spokes supporting the individual shells of the grazing-incident collector 103 according to FIG. 3. As can be seen from FIG. 4B, many of the field facets are only partially illuminated. In FIG. 4B the axis coordinate system is also described in the x- and y-directions. As can be seen in FIG. 4B, the field facets have much smaller dimensions in the scanning direction of the projection exposure apparatus coinciding with the y-direction than in the x-direction perpendicular to the scanning direction.

One advantage of the present invention is that the facets of the field can be arranged in blocks that allow for simple assembly. In order to properly fill the circular illumination of the field facet mirror with the fully illuminated field facets, it was not necessary to displace the field facets as in the prior art according to FIG. 4a. After the partially illuminated facets are used for illumination purposes, such a displacement is no longer necessary.

4C shows a first faceted optical element 102 constructed similarly to FIG. 4B. Like parts are provided with the same reference numerals. In FIG. 4C, the individual raster elements 311 are also arranged in a total of four columns 343.1, 343.2, 343.3, 343.4 and a plurality of rows 345. The individual rows are also spaced apart from one another, in particular the rows are spaced apart from each other so that no field sides are placed in the supporting spoke shadow area of the grazing-incident collector.

The illumination also has an outer boundary 341.1 and an inner boundary 341.2.

Also shown in FIG. 4C are light barriers 357 for individual field raster elements that are not fully illuminated. The light barriers 357 are each assigned to one field raster element 311. Individual light barriers 357 assigned to one field raster element may move in the x-direction as shown.

This results in tunable illumination in the field plane. Such details are shown in detail in FIG. 4D.

4D shows how the illumination can be adjusted in the x-direction. To illustrate this adjustment, two field raster elements or field facets 311.1 and 311.2 are shown in the illumination of the outer boundary 341.1 which are only partially illuminated. The partially illuminated field raster elements are not illuminated for the field raster element 311.1 and the illuminated portion 360.2 for the field raster element 311.2 and for the field raster element 311.1. A region 362.2 that is not illuminated for region 362.1 and field raster element 311.2. When the partially illuminated field raster elements 311.1 and 311.2 are transferred to the field plane, the illuminated areas 360.1 and 360.2 overlap and the entire illuminated field as shown in case 1 in FIG. 4D. Is added to. The light barriers 364.2 and 364.1 allow the size of the illuminated area of the field facets 311.1 and 311.2 to be adjusted. If the field faces overlap in the field plane at that time, the illumination shown in case 2 in the case of FIG. 4D appears when the light barriers 364.1 and 364.2 are adjusted in the form of dashed lines. As can be seen from the figure, only the areas 360.1.A and 360.2.A are illuminated in the field. Region 366 is not illuminated. As is evident in FIG. 4D, by moving the light barriers 364.1 and 364.2 in the x-direction, it is possible to extract energy from the illuminated field as intended and provide it inside the field according to the field height and energy. Become.

Such controllability presupposes that the uniformity of the illumination, ie the variation in the uniformity, can be affected by the field height.

By the possibility that the uniformity depending on the field height can be influenced by the field height using the adjustment device in the form of a light barrier, shown in FIGS. 4A and 4D, when the illumination changes abruptly and In addition, for example, when the uniformity in the field plane suddenly fluctuates due to fluctuations in the temporal emission intensity of the light source, as well as in spatial locations, or when replacing optical elements such as collectors or light sources, for example. The possibility of using the light barriers 364.2, 364.1 to adjust the uniformity of illumination such that the uniformity error is below a predetermined value is obtained. In particular by this possibility, the field illumination can be influenced such that the uniformity error ΔSE reaches 10% or less, preferably 5% or less, particularly preferably 2% or less. In other words, the controllability enables a kind of control system that adjusts the uniformity to fall below a predetermined uniformity error according to the uniformity of illumination in the field plane, for example using the light barrier of the control device.

Thus, for example, the uniformity and also the uniformity error can be varied after the replacement of the light source. In that case it is possible by means of light barriers 364.1 and 364.2 to adjust the illuminated areas of the partially illuminated field faces, thus bringing the uniformity error to a predetermined value.

It will also be possible to readjust during operation. For this purpose, after a predetermined number of irradiations, a sensor is provided in the field plane or in the image plane of the projection objective, for example pivoted inward, and the illumination in that plane is measured. Uniformity errors can then be detected from the measurements, and corresponding adjustments to the corrections can be made. This fact makes it possible to readjust the uniformity so that, for example, when the layers on the collector or mirror drop, or when the light source changes, the uniformity error does not exceed. When the sensor is inserted into the image plane, ie the wafer plane, the uniformity error of the projection objective lens can be detected together.

FIG. 5 shows a first arrangement of pupil raster elements 415 arranged on a second faceted optical element, indicated at 104 in FIG. 3. The u-v-z coordinate system is also described. Preferably, the shape of the pupil raster elements 415 corresponds to the shape of the secondary light source in the plane where the second optical element is disposed therein with the pupil raster elements.

FIG. 6 shows a ring shaped field such that an illumination system for the ring field scanner according to FIG. 3 is formed in the field plane 129.

The field 131 has a ring shape unlike the rectangular field shown schematically in FIG. 4D. 6 describes the x-y-coordinate system and the center field point Z of the field 131. The y-direction in this case means the so-called scanning direction if the illumination system is used in a scanning microlithography projection system formed with a ring field scanner, and the x-direction means the direction perpendicular to the scanning direction. Depending on the x-position, also referred to as the so-called field height, a scan integrated value, that is, a value integrated along the y-axis, can be detected. Multiple values of one lighting device are values that depend on the field. This type of field dependent value is, for example, so-called Scanning Energy (SE), the value of the scanning energy being different depending on the field height (x). In other words, the scanning energy is a function of field height. In general, the following equation applies:

Where E is the intensity distribution in the x-y-field plane along x and y. For constant, ie uniform illumination and other characteristic values of the illumination system, such as ellipticity and center of gravity, which likewise depend on the field height (x), the values are actually the same over the entire field height (x) The advantage is that only slight deviations occur.

As a measure for the uniformity of scanning energy in the field plane, variations in scanning energy appearing over the field height are used. In other words, uniformity is expressed as a percentage by the following equation for uniformity error:

ΔSE in the above equation is the variation of the scanning-energy in terms of uniformity error or%.

SE _Max : the maximum value of scanning-energy

SE _Min : minimum value of scanning energy

By "ellipticity" in this application is indicated the weight of the energy distribution in the exit pupil or in the exit pupil plane. As shown in FIG. 7, if the coordinate system is defined in the u, v, z-direction in the exit pupil plane 140, the energy in the exit pupil 1000 is distributed over the angular region of the coordinate u, v. In Fig. 7, the pupils are distributed in the angular regions Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8. The energy volume in the individual angular regions is obtained by integration over the individual angular regions. Thus, for example, I1 represents the energy volume of the angular region Q1. For I1 the following equation applies:

Where E (u, v) is the intensity distribution in the pupil.

The -45 ° / 45 ° ellipticity is defined as follows:

The 0 ° / 90 ° ellipticity is defined as follows:

In the above formula, I1, I2, I3, I4, I5, I6, I7 and I8 are defined in the individual angular regions Q1, Q2, Q3, Q4, Q5, Q6, Q7 and Q8 of the exit pupil as shown in FIG. Energy volume as shown.

Because different exit pupils appear for each field point of the illuminated field in the field plane, the pupil and, in addition, the ellipticity, depends on its position within the field. Ring shaped fields as used for microlithography are shown in FIG. 6. The field is described by the x-, y-, z-coordinate system in the field plane 129. Since the pupil depends on the field point, the pupil depends on the x-, y-position within the field, in which case the y-direction is the scanning direction.

In addition, at each field point of the illuminated field, a central beam of one light beam is defined. The center beam is the energy weighted direction of the beam of light starting from the field point.

The deviation of the center beam from the main beam CR is the so-called center-of-center error. For the raw center error, the following equation applies:

Where E (u, v, x, y) is the energy distribution depending on the field coordinate x, y in the field plane 129 and the energy distribution depending on the pupil coordinate u, v in the exit pupil plane 140.

In general, each field point of one field in the field plane 129 is assigned one exit pupil in the exit pupil plane 140 of the lighting system according to FIG. 3. Within the exit pupil assigned to the individual field points, a number of third light sources, also referred to as sub-cavities, are formed.

8 shows an example of the scanning integrated pupil for the field height x = −52 mm of the arc shaped field as shown in FIG. 6.

The scanning integrated pupil is obtained by integration over the scanning path, i.e., the energy distribution E (u, v, x, y) along the y-direction. The scanning integrated pupil thus appears in the following manner:

In that case the integral to the coordinates (u, v) of the scanning integrated pupil is the intensity (I1, I2, I3, I4, I5, I6, I7, I8) as described above and for example x = − Calculate -45 ° / 45 ° or 0 ° / 90 ° ellipticity, depending on the field height x of 52.

As can be seen in FIG. 8, the exit pupil has a few sub-pores, ie, a third light source 500, in the exit pupil plane. As can be seen from FIG. 8, the individual sub-pores 500 possess different energies, for example a collector shell or collector support spoke of a mesh collector, such as the mesh collector 103 shown in FIG. 3. It has a microstructure formed from. Different intensity values of the sub-cavities 500 are the result of incomplete illumination of individual field raster elements or field facets of the first faceted optical element 102. As mentioned above, a few field raster elements are incompletely illuminated and the other elements are fully illuminated on the contrary. Due to the energy difference between the incompletely illuminated field raster elements and the fully illuminated field raster elements, measures are taken to ensure as much uniform ellipticity and center of gravity as possible over the field height, ie along the x-coordinate. If not, the ellipticity and center of gravity in the exit pupil, for example -45 ° / 45 ° or 0 ° / 90 ° ellipticity, fluctuate strongly with the field height, ie along the x-coordinate.

If the field facets or field raster elements are assigned very specifically to the pupil facets or pupil raster elements, it is possible to achieve a uniform ellipticity and a center of gravity as much as possible depending on the field height within the exit pupil.

The assignment rule for an example of a total of eight field- and pupil faces that ensures such a result is shown in FIGS. 9A-9B. The field facets F9, F10, F11, 12, F41, F42, F43, F44 are shown in FIG. 9B. 9 shows the corresponding pupil facets for guiding illumination within the exit pupil.

It can be seen from FIGS. 9A and 9B that if field facets facing each other, such as field facets F9 and F10 of FIG. 9A, are assigned to point symmetric sub-cavities inside the exit pupil, the center of gravity over the entire field Rate error is minimized. The same applies to the faces F11 and F12 facing each other. One faceted optical element with field facets is shown in FIG. 9A, and the corresponding faceted optical element with pupil facets PF9, PF10, PF11, PF12, PF41, PF42, PF43 and PF44 is shown in FIG. 9B. It is. The position of the pupil faces again determines the position of the sub-cavities within the exit pupil. This implies that the assignment of the field facets to the pupil facets is preferably such that the face facets, such as F9 and F10, which lie in reflection symmetry with respect to the x-axis, preferably point symmetrically inside the exit pupil. The pupil faces PF9 and PF10 having the images. Such an allocation scheme is generally preferred because field facets arranged in reflection symmetry with respect to the x-axis generally have substantially the same intensity profile in circular illumination.

In order to keep the ellipticity error small, each of the two pairs of face mirrors arranged adjacent to each other, that is, the field face surfaces F9, F11, F10, and F12, are pupil face mirrors PF9, PF10, PF11, PF12). Thus, field facets exhibiting similar intensity waveforms are placed in the octagonal circle displaced by 90 ° in the pupil.

In the ideal case, I1 (x) = I3 (x) = I5 (x) = I7 (x) is applied, resulting in the following equation,

The ellipticity of the four channels is uniformly 1 over the field.

Faces complemented by self-illumination, for example facets F9 and F41 are assigned to pupil facets PF9 and PF41 such that sub- pupils assigned to field facets PF9 and PF41 are placed next to each other in the exit pupil. do.

The advantage of such an allocation scheme is that uniform illumination is achieved over the exit pupil. When the field facets F9 and F41 are complemented, it means that the area F9.1 that appears dark on the field facet F9 becomes the bright area F41.2 on the field facet F41. By the dark area F9.1, the corresponding sub-pupils become dark in the field area allocated to F9.1. In that case the sub- pupils assigned to the pupil face PF41 are correspondingly brightly illuminated in the field area. When the pupil faces PF9 and PF41 are arranged side by side, the action of light-dark-replacement or division is minimized over the field.

2%이다.By the individual light barriers for controlling the illumination of the individual field facets, the illumination uniformity in the field plane of the illumination system can be influenced. In particular, for example, illumination uniformity can be adjusted such that ΔSE (x) is 2% or less. The result of uniformity control using the light barrier is shown in detail in FIG. Without correction, uniformity error ΔSE has a value of 10% or more, while uniformity error ΔSE is 5% or less. In particular, the maximum value SE _Max of the scan-integrated energy SE (x) after calibration is almost 1.02 and the minimum value SE (x) _Min is about 1.0, so that ΔSE after field illumination calibration by the light barrier

2%.

The effect of uniformity adjustment with the light barrier, as described above, on the field height, i.e., the ellipticity waveform depending on the x-coordinate, is shown in Figures 11a and 11b for a -45 ° / 45 ° or 0 ° / 90 ° ellipticity. have. 11a shows a -45 ° / 45 ° -ellipse rate 2200.1 or 0 ° / 90 ° -ellipse rate 2200.2 for the illumination system according to FIG. 3 with the channel of the field facet assigned to the pupil facets in the manner described above. Shows. Depending on the field height, the -45 ° / 45 ° ellipticity fluctuates between 0.97 and 1.03, while the 0 ° / 90 ° ellipticity fluctuates between 0.97 and 1.03. FIG. 11B shows the waveform of −45 ° / 45 ° ellipticity 2200.3 and the waveform of 0 ° / 90 ° ellipticity 2200.4 after field uniformity is corrected as shown in FIG. 10. As can be seen from FIG. 11B, the 0 ° / 90 ° ellipticity as well as the −45 ° / 45 ° ellipticity only varied within the allowable error range upon uniformity correction. The −45 ° / 45 ° ellipticity varies between field heights between 0.990 and 1.01 and the 0 ° / 90 ° ellipticity is between 0.99 and 1.02.

In Figures 12a and 12b, the circle of the system depends on the field height (x), for the system according to Figure 3 with the assignment rules in the x- and y-directions already provided for the individual exit pupils belonging to the field height. Center rate error is shown.

The raw center error is less than 1 mrad in the x- and y-directions. The waveform in the x-direction prior to the uniformity correction is indicated by reference numeral 2300.1 in FIG. 12A and the waveform in the y-direction is indicated by reference numeral 2300.2. 12B shows the raw center ratio error after uniformity correction. As can be seen from FIG. 12B, the raw center error is less than ± 0.2 mrad in the y-direction as well as in the x-direction over the field.

According to the present invention, it is possible to first adjust the illumination uniformity in the field plane, the scan integrated ellipticity error and the center of gravity error of one system, the large part of the light being the plane where the first faceted element is assigned therein. An illumination system is provided that is configured to be used to illuminate a field plane at.

1 is a basic principle diagram of a dual faceted lighting system.

2A is a beam path diagram of a dual faceted illumination system up to the field plane.

2B is a beam path diagram of a dual faceted illumination system up to the exit pupil plane.

3 is a principle structural diagram of a lighting system.

4A shows a first faceted optical element with field raster elements according to the prior art.

4B is a schematic diagram of a first faceted optical element with light barrier and field raster elements in accordance with the present invention.

4C is a detailed view of a first faceted optical element with illumination control device.

4D is a schematic diagram showing an illumination control state in the example of two field facets.

5 illustrates a second faceted optical element with pupil facets.

6 shows a ring field illuminated in the field plane of the lighting system.

7 shows the distribution state of the exit pupil.

8 shows an example of an exit pupil with sub-pores.

9A and 9B are schematic diagrams illustrating a state in which eight partially illuminated facets are assigned to different pupil facets, while forming exit pupil illumination.

Figure 10 shows the uniformity waveform for the embodiment with 312 channels, in which case 100 field facets are not fully illuminated.

11A and 11B show waveforms of 0 ° / 90 ° ellipticity and -45 / 45 ° ellipticity depending on the field height x before and after uniformity correction.

12A and 12B show waveforms of the raw center ratio before and after uniformity correction.

Claims (26)

Projection radiation of 193 nm or less, specifically 126 nm or less, more specifically 30 nm or less, in particular in the range of 10 nm to 30 nm, where light from the light source is directed along the light path towards the field plane 129 In a lighting system for a device, Optical element 102 having a plurality of field raster elements 309 and disposed in a plane 150 within the light path from the light source 101 after the light source 101 to the field plane 129. Including, The plane 150 is provided with illumination, wherein at least one field raster element of the plurality of field raster elements 309 in the plane 150 is illuminated only in the first region 360.1, 360.2 and the second region. Not illuminated (362.1, 362.2), There is an apparatus for adjusting the size of the first and second regions of the field raster elements 311.1, 311.2, And a uniformity of field illumination of the field (131) in the field plane (129) by the scale adjustment device. The method of claim 1, Illumination in the plane 150 is received by the field raster elements 309 disposed in the plane 150, 70% or more, specifically 80% or more, more specifically 90% or more are accommodated Illumination system for projection exposure apparatus. The method according to claim 1 or 2, The uniformity error ΔSE of the field illumination is 10% or less, specifically 5% or less, more specifically 2% or less. The method according to any one of claims 1 to 3, The field 131 has a first shape, the field raster elements 309 have a second shape, and the first shape generally coincides with the second shape. Lighting system. The method of claim 4, wherein And said field raster elements (309) have an arc shape. The method according to any one of claims 1 to 5, Said field raster elements (309) are arranged in columns (343.1, 343.2, 343.3, 343.4) and rows, said rows not being offset from each other. The method according to any one of claims 1 to 6, The field raster elements are arranged in columns and rows, and a plurality of field raster elements are integrated into blocks (347). The method according to any one of claims 1 to 7, And said illumination control device comprises at least one light barrier (357). The method of claim 8, And the light barrier (357) is formed to be movable within the plane (150). The method of claim 9, A scanning direction is defined in the plane (150) and the light barrier (357) is formed to be movable in a direction substantially perpendicular to the scanning direction. The method according to any one of claims 8 to 10, The light barrier (357) is assigned to one or more field raster elements (309) illumination system for a projection exposure apparatus. The method according to any one of claims 1 to 5, The lighting control device An apparatus disposed in the light path from the light source to the field plane to deform and / or tilt an optical element; An apparatus for moving the optical element (102) within the plane (150); And And one or a combination of devices for moving at least one light barrier assigned to one field raster element. A projection irradiation apparatus having a wavelength of 193 nm or less, specifically 126 nm or less, more specifically 30 nm or less, in particular 10 nm to 30 nm, in which light of the light source is guided along an optical path directed to the field plane 129. In the lighting system for Optical element 102 having a plurality of field raster elements 309 and disposed in a plane 150 within the light path from the light source 101 after the light source 101 to the field plane 129. Including, The plane 150 is provided with illumination, at least one portion of the plurality of field raster elements is incompletely illuminated in the plane, The incompletely illuminated field raster elements are arranged such that field illumination is provided within the field plane 129 having a uniformity error ΔSE, wherein the uniformity error ΔSE is 10% or less, specifically 5%. Hereinafter, more specifically, it has a value of 2% or less, One pupil raster element 22 is assigned to each field raster element 20, and an optical channel is formed between the field raster element and the assigned pupil raster element, so that the exit pupil illumination in the exit pupil of the illumination system is An illumination system for a projection exposure apparatus having a scan integrated ellipticity in the range of 1 ± 0.1, specifically 1 ± 0.05, more specifically 1 ± 0.02. The method of claim 13, Said field having a first shape, said field raster elements having a second shape, said first shape generally coinciding with said second shape. The method of claim 14, And said field raster elements have an arc-shaped shape. The method according to any one of claims 13 to 15, Wherein said field raster elements are arranged in columns and rows, said rows being offset from one another. The method according to any one of claims 13 to 15, Wherein said field raster elements are arranged in columns and rows, and a plurality of field raster elements are integrated into blocks. The method according to any one of claims 1 to 17, Illumination system for a projection exposure apparatus, characterized in that the illumination in the plane (150) has a circular shape or an annular shape. The method according to any one of claims 1 to 18, The optical element is a first optical element 102 and has a plurality of pupil raster elements next to the first optical element 102 in the optical path from the light source 101 to the field plane 129. An illumination system for a projection exposure apparatus, characterized in that a second optical element (104) is arranged. The method of claim 19, One pupil raster element 22 is assigned to each field raster element 20, and light rays are formed between the field raster element and the corresponding pupil raster element, and the exit pupil illumination in the exit pupil plane of the illumination system is An illumination system for a projection exposure apparatus, characterized in that it has a centroid error error of 2.5 mrad or less, specifically 1.5 mrad or less, more specifically 0.5 mrad or less. 21. A projection exposure apparatus comprising the illumination system according to any one of claims 1-20. And a projection objective lens for transferring an object illuminated in the field plane by the illumination system to an image plane. To adjust the uniformity, center-of-centre, and ellipticity of an illumination system having illumination in a plane 150 in which a first optical element with a plurality of field raster elements is disposed, field illumination in a field in the field plane, and pupil illumination in an exit pupil. In the method, Illumination control in the plane 150 with field raster elements such that the uniformity of field illumination of the field has a uniformity error of 10% or less, specifically 5% or less, more specifically 2% or less. Adjusting using a device; And Assigning each field raster element to a pupil raster element of a second optical element to define an optical channel, The assignment is such that the pupil illumination of the exit pupil plane has a center of gravity error of 2 mrad or less, specifically 1.5 mrad or less, more specifically 0.5 mrad or less, and / or 1 ± 0.1, specifically 1 ± 0.05, more specifically How to adjust the uniformity, the center of gravity and the ellipticity of the lighting system is performed to have an ellipticity of 1 ± 0.02. The method of claim 22, The illumination control device includes a light barrier, the light barrier being assigned to incompletely illuminated field raster elements, the illumination field having a scanning direction in the plane 150, and the light barrier having uniformity. Moving in a direction perpendicular to the scanning direction to adjust the uniformity, center of gravity and ellipticity of the illumination system. The method of claim 22 or 23, The illumination control device includes a device for modifying and / or tilting an optical element disposed in an optical path from a light source to the field plane, wherein the optical element is deformed and / or tilted to adjust uniformity. A method for adjusting the uniformity, center of gravity, and ellipticity of an illumination system. The method according to any one of claims 22 to 24, The field raster elements are arranged on the carrier at a predetermined inclination angle, and the inclination angle is varied by the actuator, so that the assignment of the field raster elements to the pupil raster elements is controlled. Method for controlling the rate and ellipticity. Using a projection exposure apparatus according to claim 21, transferring the structured mask to a photosensitive layer in the image plane of the projection objective lens, and Developing the structured mask to form a portion of the microelectronic component or the microelectronic component itself.

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