TWI785041B - Catoptric system, lithographic exposure tool, method for forming fringe pattern onto workpiece and microdevice manufacturing method - Google Patents

Abstract

A catoptric system, a lithographic exposure tool, a method for forming fringe pattern onto workpiece and a microdevice manufacturing method are provided. A catoptric system having a reference axis and including a reflective pattern-source (carrying a substantially one-dimensional pattern) and a combination of two optical reflectors disposed sequentially to transfer EUV radiation incident onto the first optical component to the pattern-source the substantially one-dimensional pattern of which is disposed in a curved surface. In one case, such combination includes only two optical reflectors (each may contain multiple constituent components). The combination is disposed in a fixed spatial and optical relationship with respect to the pattern-source, and represents an illumination unit (IU) of a 1D EUV exposure tool that additionally includes a projection optical sub-system configured to form an optical image of the pattern-source on an image plane with the use of only two beams of radiation. These only two beams of radiation originate at the pattern-source from the EUV radiation transferred onto the pattern-source.

Description

Reflective systems, lithography exposure tools, forming streaks on workpieces Method of patterning and method of manufacturing micro-device

The present invention relates to the optical design of spatially-dense line printers configured to operate in the extreme ultraviolet (EUV) and/or ultraviolet portion of the spectrum, and more particularly to There is an illumination subsystem for a lithography exposure tool configured as such a printer.

[CROSS-REFERENCE TO RELATED APPLICATIONS]

This application asserts U.S. Provisional Patent Application No. 62/504,908, filed May 11, 2017, U.S. Patent Application No. 15/599,148, filed May 18, 2017, and U.S. Provisional Patent Application No. The priority and rights of the international patent application PCT/US2018/027785 and the international patent application PCT/US2018/029160 filed on 16th. The disclosures of each of the above applications are incorporated herein by reference.

The structure of currently commercially available EUV lithography equipment (hereinafter referred to as a general EUV system) is configured to image a photomask carrying an arbitrary two-dimensional (two-dimensional, 2D) pattern on a workpiece (for example, semiconductor wafer, substrate) on a rectangular field (rectangular field). Due to the two-dimensional nature of such patterns that must be optically transferred from the reticle and imaged onto the workpiece, it is necessary to implement a general EUV system as a scanning system to provide the relative displacement between the substrate and the reticle. Currently, such implementations are accomplished with one mobile station for the reticle and at least one further mobile station for the substrate, without which the reticle pattern can be translated with sufficient accuracy and resolution. The transfer of all features to the substrate is rather difficult and cannot be achieved in practice. The structural and operational complexity of currently used systems inevitably and greatly increases operating costs and reduces the number of substrate exposures per unit time, partly due to the limited transmission of EUV light through the optical system. Furthermore, a series of optical components of existing general-purpose EUV systems requires and is characterized by high complexity due to the process of optical imaging in two dimensions required to transfer the pattern onto the workpiece. As an example, the series of optical assemblies may include: - six polished mirrors in the projection portion (or projection optics) of the series of optical assemblies, with mirror roughness less than 0.1 nm root mean square ( rms ) and mirror alignment tolerance Sub-1nm, etc.; - complex and finely tuned illumination parts of the series of optical components; - and large reticles or masks with complex reflective coatings. Furthermore, proper pattern transfer requires the use of complex combinations of alignment masks. All these factors inevitably lead to high design and fabrication costs of a general EUV system.

Embodiments provide a reflective system with a reference axis. The reflection system Comprising: a reflective pattern source carrying a substantially one-dimensional (1D) pattern defined in a spatially curved surface; and a combination of only two optical components, the only three optical components arranged sequentially with respect to each other to transfer EUV radiation (incident on a first of the only three optical assemblies) to the pattern source. Each of the three optical components has non-zero optical power. The combination is arranged in a substantially fixed spatial and optical relationship with respect to the pattern source and represents an illumination unit (IU) of an EUV exposure tool comprising projection optic (PO) sub- system, the projection optics subsystem has a reference axis and is configured (with a reduction factor of N>1 on an image plane optically conjugate to the pattern source) to form the optical image. The only two beams of radiation originate at the patterned source as a result of diffraction of the EUV radiation transferred onto the patterned source. In a specific embodiment, the projection optical subsystem is a reflective projection optical subsystem including only a primary reflector and a secondary reflector. It should be noted that the illumination unit IU may further be referred to interchangeably as an illumination lens, IL or simply as an illuminator. The projection optics subsystem or PO of an exposure tool to supplement the illumination unit may be referred to herein interchangeably as the "PO subsystem" or "projection lens" or "PL".

Related embodiments provide a lithographic exposure tool having a string of optical elements positioned to deliver EUV radiation to a target workpiece via the string of optical elements. The train of optical elements comprises: (i) a reflective illumination unit (IU); (ii) a reflective pattern source configured to receive the EUV radiation from the illumination unit and to pass through the substantially one-dimensional surface of the pattern source. pattern (the pattern is defined at the curved ) diffracting the EUV radiation to form first and second diffracted beams of the EUV radiation; and (iii) a reflective projection optics (PO) subsystem positioned from the pattern A source receives the first diffracted beam and the second diffracted beam and (with a reduction factor of N>1 in an image plane optically conjugate to the patterned source) utilizes only the first diffracted beam The beam and the second diffracted beam form an optical image of the pattern source. In particular instances, the substantially one-dimensional pattern forms a one-dimensional (1D) diffraction grating configured as one of: (i) a phase diffraction grating; (ii) an amplitude a diffraction grating; and (iii) an attenuated phase-shifting diffraction grating.

The lithographic exposure tool is generally configured to form the image to include a spatial frequency up to twice the spatial frequency characterizing the substantially one-dimensional pattern.

In operation of such a lithographic exposure tool, the first diffracted beam and the second diffracted beam represent a pattern formed from the EUV radiation at a spatially curved substantially one-dimensional pattern of the pattern source. Corresponding diffraction orders respectively, and have equal absolute values but different signs. Alternatively or in addition, the train of optical elements may be configured to transfer the first diffracted beam and the second diffracted beam from the pattern source to a first element of the projection optics subsystem , such that the first diffracted beam and the second diffracted beam are spatially separated from each other by the last element of the lighting unit without making the first diffracted beam and the second diffracted beam Either of the beams is intercepted by the last element of the lighting unit. Here, the lighting unit includes a first fly's eye (FE) reflector and a second fly's eye reflector, and each of the first fly's eye reflector and the second fly's eye reflector includes an individual Separate pairs of reflective elements The first fly's eye mirror is positioned to image the distribution of the EUV radiation from the entrance pupil of the illumination unit to the second fly's eye mirror. Here, said last element of said lighting unit is represented by said second fly's-eye reflector.

In a related embodiment, the lighting unit includes a first fly's eye (FE) reflector and a second fly's eye reflector, each of the first fly's eye reflector and the second fly's eye reflector comprising respective corresponding arrays of individual constituent reflective elements, and the first fly's eye mirror positioned to image the distribution of the EUV radiation from the entrance pupil of the illumination unit to the second fly's eye mirror . Alternatively or additionally, i) the pattern source is arranged in a substantially fixed spatial relationship with respect to the lighting unit and/or ii) the substantially one-dimensional pattern has an outer boundary, and the first contrast value and the second The two contrast values remain substantially equal (here, the first contrast value is the value of the optical contrast of the first portion of the image formed at the target workpiece representing the outer boundary, and the second contrast value is a value of optical contrast for a second portion of the image, the second portion representing a portion of the one-dimensional pattern within the outer boundary). Alternatively or in addition, an optical element of the illumination unit may be positioned to block the third beam of EUV radiation from propagating to a surface located between this optical element and the first optical element of the projection optics subsystem (here, The third beam represents the zeroth order diffraction of the EUV radiation formed at the patterned source). When the substantially one-dimensional pattern is associated with a spatially curved surface, such an optical element is represented by a fly's eye (FE) mirror comprising an array of individually constituting reflective elements.

In one embodiment of the lithography exposure tool, the projection optics subsystem A primary mirror and a secondary mirror are included, and at least one of the primary mirror and the secondary mirror contains two identical reflective elements that are spatially disconnected from each other. Here, the reflective surface of any one of the first reflective element and the second reflective element among the two identical reflective elements may be configured to be congruent with a part of the rotationally symmetrical surface.

100: 1D EUV system

102: System

114: light source

118: first mirror/mirror array/optical assembly

122: second mirror/mirror array/optical assembly

126: Relay reflector/relay mirror

130: first reflector

130A: Center Visually Impaired/Primary Mirror

134: second reflector

134A: Central visual impairment

140: Radiation

144: Mask/Pattern Source/Surface

144': mask/pattern source

148: Radiation

152A, 152B: diffracted beam

156: Workpiece/Wafer/Substrate/Image Plane

156A: Wafer table

160: Aperture

160': field end

164: Aperture

170: system

180: radiation

210: collector/collector mirror/source

210A: Center Opening/Center Disc Visually Impaired

214: Tin injection port

216: Secondary light source IF

216-A, 216-B: light source

218:Plasma emission/plasma distribution

504: bunch

508: circle/curve/boundary

510: circle/boundary line

514: Area/Illumination Pupil

532A, 532B: area

534A, 534B: area

540: Boundary

544A, 544B: area

700:FE1 array

710: sub-aperture

714:Outer boundary

716: Boundary

800: FE2 array

810: Subaperture/Mirror Elements

824:External Boundary/Aperture

900: Lighting Units/Illuminators

918-i, 918-j: sub-aperture

922:Second "fly's eye" mirror array/FE-2 mirror

922-i: Subaperture

922-j: Mirror

926: relay mirror

934: Image plane

1010: center

1100: 1D EUV system/optical element string

1120: position

1301, 1302, 1303, 1304, 1305, 1306: steps

1311, 1312, 1313, 1314, 1315, 1316, 1317, 1318, 1319: steps

1400: Lighting unit/mirror/mirror array

1410: reflective element/mirror element

1450: Fly's Eye Mirror Array/Mirror

1460: reflective element

1510: folding mirror

1520: Radiant Flux / Radiation

A, B: area

AX: optical axis

EE: dotted line

EP: entrance pupil

f ₁ , f ₂ , f ₃ : focal length

FE1, FE2: "Fly's eye" mirror array

FE1-A, FE1-B: First "fly's eye" mirror array/mirror

FE1-D: Spatial range

FE2-D, FE2-d: Spatial range

h ₀ , h ₁ , h ₂ , h ₃ , h ₄ , h ₅ : size

LA, LB: optical input

LPP: laser driven plasma

M1: Primary mirror, mirror element

M2: Secondary mirror, mirror element

NA : numerical aperture

P(+1): point

t ₀ , t ₁ , t ₂ , t ₃ , t ₄ : values

X, Y, Z: direction

Ω _PO : solid angle

Φ ₁ , Φ ₂ , Φ _c , Φ _R : optical power

The invention will be more fully understood by referring to the following detailed description of specific embodiments in conjunction with the accompanying drawings, which are not drawn to scale:

FIG. 1A provides a general schematic diagram of a one-dimensional EUV exposure tool of an embodiment; FIG. 1B and FIG. 1C schematically illustrate related embodiments of a one-dimensional EUV exposure tool in more detail; FIG. 2A shows a laser-driven plasma light source. Configuration of the light collection system, the laser-driven plasma light source has an ellipsoidal mirror for refocusing the EUV radiation from the laser-driven plasma LPP to an "intermediate focus" (IF) (this in turn is implemented for the illumination unit acts as a light source, for example, and is called a secondary light source). A 5 sr collector and 1.6 sr subaperture configuration are schematically shown for comparison; FIG. 2B is a schematic diagram of a ray-based model of the laser-driven plasma source shown in FIG. Injection port 214 and collector 210 of secondary light source IF 216; Figures 2C and 2D show the assumed substantially Gaussian distribution of the plasma of the laser driven plasma source according to the model used for the calculation.

Figures 3A and 3B show, respectively, the distribution of radiation as a function of the angle of a laser-driven plasma source model when viewed along the optical axis, and the radiation from the same source when viewed transverse to the optical axis. The angular distribution in the identified cross-sectional plane; Fig. 4A and Fig. 4B show the distribution of the light produced by the modeled laser-driven plasma source and the direction cosine of such light at the plane of the secondary light source respectively, so The secondary light source passes through the converging point of the rays reflected by the collector of the plasma source; FIGS. Figure 6A and Figure 6B show the first-level layout of the illumination unit of the optical system of the embodiment containing a flat or planar mask (pattern source); Figure 7A is along the Schematic showing the overlap of the "tiled" multiplicity of sub-apertures of the first "fly's eye" mirror of an illumination unit, viewed from the optical axis, from a laser-driven plasma source for the source itself Light is received; FIG. 7B shows the angular distribution of individual mirror elements (sub-apertures) of the first fly-eye mirror shown in FIG. 7A; FIG. 7C is an implementation of the first fly-eye mirror shown in FIGS. 7A and 7B Figure 8 is a schematic diagram of the second fly-eye reflector of the lighting unit receiving light from the first fly-eye reflector when viewed along the optical axis; Figure 9 is a schematic diagram of the second fly-eye reflector configured to Schematic diagrams of related embodiments of lighting units of embodiments of multiple light sources operating together; FIGS. 10A and 10B are diagrams showing dimensions of embodiments of fly-eye reflectors FE1 and FE2 of embodiments of lighting units; 11A is a schematic diagram of an embodiment of a monolithic optical element string for a one-dimensional EUV tool constructed in accordance with the present concepts; FIG. 11B provides an illustration of the optical pathways within an embodiment of an illumination unit; Each of FIG. 1C also shows a diagram of the spatial coordinates of the EUV beam incident on the pattern source (reticle) of the one-dimensional EUV system from the last mirror of the illumination unit of the one-dimensional EUV system , and the first and second diffracted beams represent different diffraction orders formed at the patterned source as a result of diffracting the incident EUV beam on the light source. The last mirror of the lighting unit may be a relay mirror of the lighting unit (for example, in the case where the pattern source is substantially flat, this is the third mirror in the three-mirror embodiment of the lighting unit shown in FIG. 1B ) or a second mirror (for example in the case of the pattern source being spatially curved, in the two-mirror embodiment of the illumination unit shown in FIG. 1C); FIGS. 14A and 14B are schematic diagrams of related embodiments of elements of an illumination unit of an example of a one-dimensional EUV system containing a spatially curved reticle or pattern source; FIG. Related embodiments of monolithic optical element strings for 1D EUV tools with curved reticle or pattern source; FIGS. 16A and 16B show the illumination unit of an optical system with an embodiment of a spatially curved reticle (pattern source) First level layout; Figures 17A, 17B, 17C, and 17D show light propagating EUV radiation through the illumination unit and projection optics subsystem of a one-dimensional EUV system in the following plane The optical path is parallel to the plane containing the radiation beam representing the diffraction orders formed at the spatially curved reticle.

In general, the size and relative proportions of elements in the drawings may be set differently from the actual size and relative proportions, so as to properly facilitate the conciseness, clarity and understanding of the drawings. For the same reason, it may not necessarily be necessary to show all elements presented in one figure in another figure.

The discussed embodiments set forth an optical system configured as an illumination unit of a one-dimensional EUV exposure tool and disclose the use of a new one-dimensional pattern for a selected substrate (which may be referred to generally as a workpiece or a wafer and in specific cases A method of lithographic marking in which a pre-formed spatially distorted pattern can already be carried, wherein the new one-dimensional pattern contains spatially densely packed parallel lines.

As already mentioned above, general EUV systems present various problems, among which there is the problem of ensuring that general EUV systems remain commercially competitive. These problems include: (A) Insufficient optical power generated by the EUV light sources that are typically equipped with general-purpose EUV systems. Currently, a typical output is about 40 watts to 80 watts. This problem is exacerbated by the fact that the optical power delivered from the EUV light source to the reticle by the illumination subsystem of the EUV system is further reduced by the limited (approximately 70% for each mirror) reflectivity of the EUV mirrors . This illumination subsystem may be further interchangeably referred to as an illumination unit, IU (or illumination lens, IL or simply illuminator). (B) Sensitivity of the operation of a general EUV system to defects and/or particles on the reticle mask. Indeed, since general-purpose EUV systems are configured to convert 2D patterns from reticles into The image is transferred to the wafer, so the pattern transferred to the wafer can be easily damaged by defects or particles on the reticle. Said another way, each defect or particle larger than tens of nanometers on the reticle can destroy the pattern printed on the wafer. (C) Very stringent requirements on the optical aberrations of the projection subsystem imposed by the two-dimensional nature and high resolution of the arbitrary pattern to be printed. The projection subsystem may be more interchangeably referred to as projection optics (PO) or projection lens (PL).

Alternatives to the EUV lithography process currently in use (and specifically a process that involves multiple patterning of the substrate with deep ultraviolet (DUV) light using an immersion lens, sometimes at a wavelength of approximately 193 nm) Can be less expensive but involves complex wafer handling between multiple exposures. Eventually, as the resolution required for features increases, it will reach a point where the cost of the multiple patterning process is similar to the cost of general EUV exposure.

Printing patterns with simplified geometries using general EUV systems and/or alternative immersion systems is not economically attractive for any of the above reasons. The scenario thus poses the problem of configuring EUV exposure tools that are specifically and judiciously configured and optimized for imaging patterns comprising densely spaced lines; in particular—in the extreme ultraviolet spectrum region (eg, at a wavelength of about 13.5 nm). Not only will the design and operational characteristics of such a tool meet the optomechanical requirements involved in imaging the transfer of a simplified reticle's one-dimensional pattern onto a semiconductor substrate, but the reduced cost of such a tool will be beneficial to the industry would also be helpful. An important part of this simplified EUV system is its illumination subsystem or unit (referred to simply as an illumination unit (IU)), which The OR unit delivers light from the light source of the exposure tool to a mask whose pattern is intended to be imaged on the image plane and printed on the workpiece at this imaging plane, which is the subject of this disclosure. (The projection optics subsystem or PO of an exposure tool used to supplement the illumination unit may be referred to interchangeably herein as the "PO subsystem" or "projection lens" or "PL".)

As used herein, unless otherwise stated, the term "one-dimensional pattern" (or "1D pattern") refers to a pattern defined on the surface of a mask or reticle for photolithographic transfer to a selected substrate. A photosensitive photoresist (eg, a semiconductor wafer) to generate an image of the one-dimensional pattern) and a geometric pattern extending across the surface, usually along two axes transverse to each other. A one-dimensional pattern can vary along a first axis of the pattern while remaining substantially unchanged along a second axis (i.e., a one-dimensional pattern can be varied by a geometrical change along the second axis by a value that does not exceed the change observed along the first axis. 50%, preferably no more than 20% of the change observed along the first axis, more preferably no more than 10% of the change observed along the first axis, even more preferably no more than 20% of the change observed along the first axis characterized within 5% or less of the observed variation along the first axis, and optimally within 1% or less of the observed variation along the first axis). An example of a one-dimensional pattern is any collection of spatially spaced apart essentially identical, parallel, elongate pattern elements (such as, for example, parallel lines or slits in an otherwise opaque screen defined at a gobo). combination) provided. In a particular case, the considered one-dimensional pattern may form a linear (one-dimensional) grating characterized by a periodically varying amplitude along a first selected axis and a constant amplitude along a second axis chosen transverse to the first axis (eg, 1D diffraction grating). Furthermore, as will be understood by those skilled in the art, to correct for imaging distortions caused by deformation of the optical system or substrate, a one-dimensional image The pattern may however have small variations along the first axis and/or the second axis. For the purposes of this disclosure, an element or component containing a substantially one-dimensional pattern (and regardless of the specific configuration of such element or component, eg, as a reticle or mask) may be referred to interchangeably as a pattern source.

In contrast, the term "two-dimensional pattern (2D pattern)" is defined to denote a collection of pattern elements whose variation or change must be defined along two axes transverse to each other. One of the simplest examples of a two-dimensional pattern is provided by a grid or mesh which, when having a spatial period defined along two transverse axes, forms a two-dimensional grating. With reference to the pattern of the mask of the mask disclosed herein, one-dimensional patterns and two-dimensional patterns are considered as such regardless of the curvature of the surface of the substrate (or mask) on which the patterns are formed. For the sake of brevity, the structure of an EUV system configured in accordance with the inventive concept (in which it is intended to use the embodiments of the illumination unit discussed herein) is specifically and purposefully configured to image a one-dimensional reticle pattern, and in It is referred to herein as a "one-dimensional EUV system". For brevity and by comparison, an EUV system configured to image a two-dimensional patterned reticle (eg, a general EUV system) may be referred to as a "two-dimensional EUV system."

The term "optical conjugation" and related terms are understood to be defined by the principle of optical reversibility according to which light will travel along the original path if its direction of propagation is reversed. Thus, these terms are defined by two surfaces when referring to two surfaces, points of one of which are imaged to points on the other surface using a given optical system. If an object is moved to a point occupied by its image, a new image of the moved object will appear at the point where the object originally appeared. The points across the optically conjugated surfaces are called and defined as optically conjugated points. When a first layer is disposed directly on a given surface or substrate or a second layer, or when said first layer is disposed on an intermediate third layer and said intermediate third layer is subsequently disposed on said given surface or on a substrate or second layer, said first layer or pattern is defined as being carried by (or carried on) said given surface or substrate or second layer.

The design of the illumination unit according to the inventive concept and the co-optimization of said illumination unit with the projection optics subsystem of a one-dimensional EUV exposure tool makes it possible to practically achieve an exposure tool or machine configured to operate at high cost Efficient way to optically transfer dense line patterns with high spatial resolution (this in the case of periodic line patterns corresponds for example to ten to twenty nanometers, preferably less than ten nanometers, more preferably a few nanometers, e.g. 5 nm or less pitch or period) to enable 10-nm and 7-nm node semiconductor devices (as defined by the International Semiconductor Technology Map (eg, ITRS 2.0)). The disclosed concepts stem from the realization that modern high-density semiconductor chip designs are increasingly based on one-dimensional geometric patterns. The structure is specifically configured to illuminate or irradiate a one-dimensional pattern (e.g., a pattern representing a one-dimensional grating) carried by the optical substrate and is coupled with a projection optics subsystem (also specifically configured to illuminate a densely packed set of lines Embodiments of the illumination unit used in conjunction with embodiments of imaging) present clear structural and operational advantages over corresponding optical systems of common two-dimensional EUV systems in the following respects:

The combination of the illumination unit and the optical projection part (of the one-dimensional EUV system implemented according to the present invention) is substantially simplified and affordable compared to the two-dimensional EUV system. and does include fewer reflective surfaces, which actually provide good quality exposure with less optical power (e.g., tens of watts, down to about 20 watts in one example) required from the light source; - due to the self-system The PO eliminates some or even many optical surfaces (compared to 2D EUV systems), thus substantially reducing the cost of scanning reticle stages, pellicles, other components, and the proposed EUV grating machine.

- Embodiments utilizing a dense-line 1D EUV lithography system solve the long-standing problem of insufficient illumination levels that exposure tools utilizing EUV light typically have by providing an illumination optics assembly having: (1) A first reflector and a second reflector comprising an array of faceted fly-eye reflectors, and (2) a relay mirror disposed between such reflectors and a mask. In such a 1D EUV system, the shape of one of the fly's eye array mirrors preferably matches the shape of the entrance pupil of the projection optics assembly that characterizes the 1D reticle pattern. The entire range of pitch values is optimized for two-beam interference.

Schematic example of a 1D EUV exposure tool.

More generalized schematic diagrams of possible embodiments 102 and 170 of a portion 100 of the one-dimensional EUV system shown in FIG. 1A configured in accordance with the concepts of the present invention are shown in FIGS. 1B and 1C . Systems 102 and 170 may include one or more light sources (as shown a light source 114). In an embodiment, system 102 is shown to include: an optical illumination subsystem or unit (IU) containing first mirror 118 and second mirror 122 and relay mirror 126; and a PO subsystem (reflective objective) , comprising two or more mirrors, at least one of which has a defined optical obscuration (the dual-mirror objective of embodiment 102 is shown to contain a first mirror 130 and a second mirror 134 each having a corresponding central visual barrier 130A and 134A). The term "optical visual impairment" is used herein to mean at least a portion (of an optical element) within the boundaries of which the further transfer of light incident on an optical element to the next optical element is hampered, inhibited or even blocked. An example of a visual barrier in the case of the illustrated reflective objective is provided by: (i) a through opening in the base of a curved mirror (such as, for example, curved primary mirror 130A), at the boundaries of which , light incident on this mirror is not reflected further towards the curved secondary mirror 130B but is transmitted through the through opening, or (ii) lacks a reflective coating in a predetermined area of the mirror (essentially defining the same optical effect). The term central visual impairment defines a visual impairment whose center is at the reference axis of the optical system. For the purposes of this disclosure, the term "on-axis illumination" is a shorthand notation for illumination in which (i) the illumination propagates generally parallel to the optical axis and/or the direction of propagation of the illumination includes directions parallel to the optical axis (excluding dipole or ring illumination in the axial direction), (ii) the center of the illumination position is at the point where the optical axis penetrates the plane of the object.

Referring to FIG. 1B , mirror 118 collects radiation 150 emitted by light source 114 and diverts the radiation 150 via reflection off mirror 122 to relay mirror 126 as radiation 140 . The system further includes a reticle 144 disposed in optical communication with the IU and PO. Reticle 144 bears a spatially dense one-dimensional pattern and is positioned to be irradiated by radiation 148 delivered from light source 114 and reflected by relay mirror 126 to reticle 144 via visual barrier 134A. As shown, the reticle 144 is a gobo that operates in reflection (in related embodiments, the reticle can optionally be configured as a transmissive reticle). It is also intended to be based on the In particular implementations of systems 100 and 102, the surface of the substrate of the reticle 144, 144' on which the one-dimensional pattern bears may be spatially curved (in which case the reflective reticle has non-zero optical power) or at Spatially flat (with essentially zero optical power). In the example shown in Figure IB, this surface of the reticle 144 is substantially planar. In the example shown in Figure 1C, this surface of the reticle 144' is substantially curved in space.

Furthermore, the one-dimensional pattern on the reticle can judiciously be distorted in a manner suitable to compensate for the undesirable distortion of the PO. When the one-dimensional pattern carried by the reticle is configured as a properly sized linear diffraction grating, the reticle 144 diffracts radiation 148 incident thereon to form a diffracted beam of light Comprising spatially distinct beams 152A and 152B, beams 152A and 152B each represent a different diffraction order (in one example, +1 and -1 diffraction orders) and propagate toward the mirror 130 of the PO (which may suitably blocking the zeroth order diffraction from this propagation). The PO's first mirror 130 and second mirror 134 in combination redirect the diffracted beam through the visual barrier 130A to the workpiece of interest or substrate 156 to image the one-dimensional pattern on which the reticle 144 is carried. At least one layer of photoresist is exposed.

It should be understood that in accordance with the inventive concept, the reticle is placed in a substantially fixed spatial and optical relationship with respect to the IU and PO subsystems because once the reticle is selected and defined within the 1D EUV exposure tool, the light Both the mask's position and orientation are fixed (except for some minor adjustments that may need to be made to maintain focus and alignment). The term "substantially fixed relationship" refers to and defines the situation when the position of the reticle, whose mechanical support lacks configuration, is however subject to some small adjustments. In order to scan the structure of the reticle with a motion synchronized with the movement of the wafer stage during operation of the exposure tool, the magnitude of the small adjustment is sufficient to correct any errors in focus, magnification, and alignment during operation of the exposure tool. error on the one hand.

Systems 100 and 102 may also include, in some embodiments, a fixed or variable size aperture 160 (eg, having a specific shape variable slit; interchangeably referred to as "pattern blind" or "blind field stop" or simply "field stop"), the IU Can be arranged to be substantially optically conjugate to the reticle 144 and 144'; the pupil stop or aperture 164 (sized to match the desired shape of the entrance pupil of the PO); the stage/mounting unit to support the reticle (Fig. not shown in); wafer stage 156A, equipped with appropriate stage movers (not shown) to provide scanning of wafer 156 relative to reticle 144 and beams 152A and 152B, as established by the lithography exposure process required; and other auxiliary elements required (eg, vacuum chambers, metrology systems, and temperature control systems). The x-axis is defined perpendicular to the axis along which scanning is performed during operation of the system, and the y-axis is defined parallel to this scanning axis. In embodiment 102, the one-dimensional pattern includes lines parallel to the Y-axis.

As shown in the generalized schematic diagram 100 shown in FIG. 1A , the system further includes a control unit (control electronics) optionally equipped with a programmable processor and configured to manage at least the crystal operation of the rotary table, and in some embodiments manages the operation of at least one of the light source, IU, and PO subsystems.

Fig. 1C schematically shows an embodiment 170 of the one-dimensional EUV system 100 in which - compared to the embodiment 102 shown in Fig. IB - the relay mirror 126 has been removed. When mask The structure of 144' is configured such that when operating in reflection, reticle 144' images mirror 122 into the entrance pupil of the PO subsystem. On transmission from the light source 114, a beam of radiation 180 traverses the field stop 160', which is positioned next to the reticle 144' (as shown) or alternatively across the reticle pattern towards the PO sub-sections. A beam of radiation diffracted by the system is in close proximity to wafer 156 (as schematically shown by dashed line EE). The approximate distance separating the field stop 160' (when present) from the reticle is generally shorter than 3 millimeters, preferably shorter than 1 millimeter, more preferably shorter than 100 microns, and even more Preferably shorter than 50 microns. In the example shown in Figure 1C, the surface of the reticle (pattern source) 144' may be spatially curved. The size of the field stop 160' can be adjusted such that the diffracted beams 152A and 152B pass through the opening of the field stop 160'.

The 1D EUVD exposure tool as shown in Figures 1A and 1B is further complemented with a control unit (control electronics) optionally equipped with a programmable processor and configured to manage at least the wafer stage and, in some embodiments, manages the operation of at least one of the light source, the illumination unit, and the projection optics subsystem. (An otherwise presented control unit is not shown in FIG. 1C for illustrative simplicity.)

Coordination between light sources, lighting unit subsystems, and projection optics subsystems

Those skilled in the art will readily appreciate that, in accordance with the disclosed concepts, in one example, an embodiment of the illumination unit as a whole is configured to operatively correspond to an embodiment of projection optics comprising reflective stigmatization and in optical The above and described embodiments of projection optics are optimized as discussed in detail in PCT/US2018/027785, the disclosure of which is incorporated herein by reference. The lighting unit includes At least one mirror unit having a "fly's eye" structure. (In one example, mirrors 118 and 122 shown in FIGS. 1B and 1C are both configured as fly-eye mirrors, as discussed below).

Furthermore, the lighting unit should also be optimized for use with light sources (radiation sources) formed from laser-driven plasma-based sources. An example of a light collection schematic for such a source (configured for use with an embodiment of an optical system of a one-dimensional EUV exposure tool) is shown in FIGS. 2A and 2B . Figure 2A shows the configuration of a laser-driven plasma source with an ellipsoidal mirror ("collector mirror") sized to refocus EUV radiation received from the LPP to the secondary light source IF (the which in turn acts as a light source for an embodiment of the lighting unit). A 5 sr collector with a 1.6 sr sub-aperture configuration is schematically shown.

2B is a schematic diagram of a ray-based model of the laser-driven plasma source shown in FIG. 2A showing collector 210 with central opening 210A, tin injection port 214 and secondary light source IF 216 . The model of the source shown in FIGS. 2A and 2B includes an aperture and a visual barrier mask (formed by a combination of two reticles and a rectangle) that are set to scale with the distance from the position of the IF 216 Boundary of the Gaussian irradiance distribution of the scaled light.

The model of the source further includes the following effects: i) a three-dimensional (3D) distribution of the plasma emission 218; (ii) ellipsoidal aberrations, visual obstructions, and reflectivity variations; (iii) of visual impairment. Assume further that the source is modeled with: a) a 650 mm diameter ellipsoidal collector mirror 210; b) a source with a numerical aperture NA bounded by a 5 sr solid angle; c) a 90 micron diameter at FWHM (or at 1 Plasma 218 radiation distribution for roughly Gaussian projection at /e ² level at approximately 210 microns. The results of a simulated projection of such a plasma distribution 218 with ^FRED® are presented in Figure 2C. In the plot shown in FIG. 2C , the irradiance of the EUV source is plotted along the vertical and horizontal axes representing coordinates on the local XY plane (the plane in which the IF 216 lies and is substantially perpendicular to the optical axis). 2D includes two plots showing the distribution of the irradiance of the EUV source in two cross-sectional planes; d) IF 216 with NA of 0.25; e) 20% central dish 210A (in collector mirror 210 formed as an axially symmetric opening with a diameter of about 130 mm); and f) a 15% linear visual barrier (100 mm width) caused by the tin ejection port 214 . The reflectivity of the reflective surface of collector 210 is assumed to be about 50%; the effective diameter of IF 216 to allow for instability of the laser-driven plasma source is assumed to be about 2 mm. The modeled spatial distribution of the light generated by the plasmonic source and at the plane of the IF 216 can be evaluated from a) Figures 3A and 3B showing the intensity distribution, and b) Figure 4A. c) a ray-spot diagram at the plane of the IF 216 shown, and c) a diagram of the ray directions at the same plane as shown in FIG. 4B.

Illumination pupil.

In order to determine the parameters of the illumination subsystem of the overall optical system of a one-dimensional EUV exposure tool, the construction of ideal or target illumination conditions is appropriate. For this, construction of the illumination pupil must be performed (i.e., with an embodiment of the illumination unit, the light delivered onto the substrate/reticle/pattern source 144 and 144' carrying the 1D pattern/1D diffraction grating angular distribution). Details of pupil construction are disclosed in PCT/US2018/027785.

To this end, FIGS. 5A-5G illustrate an example of the process of pupil construction for the disclosed optical system of a one-dimensional EUVD exposure tool. The purpose of this process is to define the opto-geometric parameters of the PO subsystem of an embodiment that facilitates optimal (enhanced) imaging of a substantially one-dimensional pattern located between the IU of the exposure tool and its PO subsystem on the Select the contrast on the workpiece. For this purpose, as a 2-beam disturbance to the image plane (incident from the IU via the exposure tool to the pattern sources 144 and 144' (such as, for example, In other words, an image is formed as a result of the optical interference between the +1st order diffraction and the -1st order diffraction formed by light on the substantially one-dimensional pattern of the one-dimensional diffraction grating). Zero order diffraction is minimized by proper design of the one-dimensional diffraction grating and/or in another embodiment blocked by opaque components (e.g., element 160'). Since the etendue of the UV light source 114 is much smaller than the required illumination/imaging etendue, the buildable area (solid angle) is maximized to achieve a 100% contrast illumination pupil. This should allow for more margin in the process of making patterned workpiece 156 .

Referring to Figures 5A and 5B, the construction begins with coherent on-axis illumination assuming a one-dimensional (single frequency) diffraction grating. Here, beam 504 illuminating the one-dimensional diffraction grating of elements 144 and 144' is shown on-axis (as viewed along reference axis 204). The +1 diffracted order beam formed at the grating (grating pitch Λ _min ) then emerges at point P(+1) separated by the distance λ/ Λ _min from the center of the pupil or reference axis. The pupil construction process continues with respect to the line pair passing through the point P(+1) with respect to the pair in image space (i.e., in the one-dimensional diffraction grating being imaged from elements 144 and 144' by the PO subsystem at A circle 508 drawn with a radius equal to the desired numerical radius NA in space above the workpiece is "reflected" to obtain a boundary line 510, shown in dashed lines in FIG. 5A. The ideal shape of the illumination field—that is, the spatially distributed light delivered to elements 144 and 144′ via the IU of the 1D EUV exposure tool—to maximize Ω _IU and image contrast is then defined by the overlapping region of the two circles 508 and 510 Showing. Region 514 outlined by the overlap between circles 508 and 510 represents Ω _IU and corresponds to the illumination pupil (i.e., incident on the substrate/reticle 144 shown in FIG. 1 bearing the 1D pattern/1D diffraction grating Angular distribution of light on ). The geometric parameters of the illumination pupil 514 with respect to the parameters of the curve 508 are indicated in FIG. 5B.

In practice, it may not be a single value of the period of the substantially one-dimensional pattern on elements 144 and 144' that is of interest but a series of values. Therefore, in addition to Λ _min , which represents the minimum value of the period of the one-dimensional grating of interest, a value Λ _max , which refers to the maximum value of this period, is also introduced. (When the propagation of the zero-order diffracted beam between the elements 144 and 144' and the workpiece via the PO subsystem is blocked and if the propagation of the zero-order diffracted beam between the elements 144 and 144' and the workpiece via the PO subsystem is blocked Blocking, as a result of imaging the 1D grating from elements 144 and 144' onto workpiece 156 via an embodiment of the PO subsystem, the 1D grating period value is halved, as will be readily understood by those skilled in the art.)

Referring now to FIGS. 5C and 5D , each of which shows the outer boundary 508 of the imaging pupil, the earlier determined lobular illumination pupil 514 operating as the light source of the PO subsystem is shown as The center lies substantially on the reference axis 204 . Imaging pupils corresponding to imaging of a one-dimensional grating with period Λ _min are shown within boundary 508 as regions 532A and 532B for the +1 and -1 diffraction order beams, respectively. The imaging pupils corresponding to imaging of a one-dimensional grating with period Λ _max are shown as regions 534A and 534B for the +1 and -1 diffraction order beams, respectively. In FIG. 5E , boundary 540 outlines two regions 544A and 544B of an overall focused imaging pupil configured to represent between Λ _min and Λ _max inclusive of Λ _min and Λ _max at Imaging of a one-dimensional grating at any period within the range of . The same two regions 544A and 544B (shown as regions A and B in FIG. 5F ) correspond to the combined solid angle Ω _PO encompassed by the focused imaging pupil of the PO subsystem. FIG. 5 additionally itemizes the values and/or dimensions illustrating a specific example of the imaging pupil of the PO subsystem for the cases of NA=0.4, λ=13.5 nm, Λmax=60 nm, and Λmin=40 nm. Here, circle 508 with radius NA=0.4 represents the numerical aperture of the distribution of light incident on the image plane via an embodiment of the projection optics subsystem. (The workpiece on which the images of the one-dimensional diffraction gratings of the pattern sources 144 and 144' are formed is located at this image plane). Region 514 represents the illumination pupil including solid angle Ω _IU . The combined region A, B represents the focused imaging _pupil of the projection optics subsystem comprising the solid angle ΩPO .

First level layout of lighting units.

)的反射鏡FE1及FE2的子孔徑 被繪製為等效透鏡元件。 6A schematically illustrates a first level unfolded layout of an embodiment of a lighting unit comprising a relay mirror 126 and configured to operate with a substantially flat or planar reticle 144, wherein FE1 and FE2 are in an array. Each of the mirrors (corresponding to and representing mirrors 118 and 122 shown in FIGS. an operationally equivalent sub-aperture lens element). Embodiments of the lighting unit are configured to operate with a single secondary light source IF 216 . For simplicity of illustration, each has a specified area a _i and focal length f _i (or optical power

) sub-apertures of mirrors FE1 and FE2 are drawn as equivalent lens elements.

Figure 6B shows the first stage layout of a single channel (ie, the illumination channel defined by respective corresponding fly-eye elements or sub-apertures of the FE1 and FE2 mirrors) of the overall embodiment of the lighting unit shown in Figure 6A. Here, the chief ray is chosen as the ray passing through the center of the entrance pupil of the projection optics subsystem from an off-axis point of the 1D pattern, while the marginal ray is defined as passing through the axial point of the object (1D pattern) Rays of light at the largest aperture of the entrance pupil of the projection optics subsystem.

)的反射鏡FE1及FE2的子孔徑被繪製為等效透鏡元件。 In contrast, Figure 16A schematically shows a first stage unfolded layout of an embodiment of a lighting unit comprising only two mirrors (FE1, FE2 arrayed mirrors or mirror arrays) and is configured to operate with a reticle 144' in which a substantially one-dimensional pattern is disposed at a curved surface. Here, each of the FE1 and FE2 arrayed mirrors (corresponding to and representing mirrors 118 and 122 shown in FIGS. For simplicity, shown as three operationally equivalent sub-aperture lens elements). Embodiments of the lighting unit are configured to operate with a single secondary light source IF 216 . For simplicity of illustration, each has a specified area a _i and focal length f _i (or optical power

) sub-apertures of mirrors FE1 and FE2 are drawn as equivalent lens elements.

Figure 16B shows the first stage layout of a single channel of the overall embodiment of the lighting unit shown in Figure 16A (ie, the lighting channel defined by respective corresponding fly's-eye reflective elements or sub-apertures of the FE1 and FE2 mirrors). In this embodiment, no relay mirror is required, since the curved reticle of the pattern source 144' images the array of FE2 mirrors onto the entrance pupil of the projection optics subsystem. Here, the chief ray is chosen to be from the 1D The off-axis point of the pattern passes through the center of the entrance pupil of the projection optics subsystem, while the edge ray is defined as the largest aperture passing through the entrance pupil of the projection optics subsystem from the axial point of the object (one-dimensional pattern) of light.

In practice, the values h ₁ , h ₂ , h ₃ , t ₀ to t ₃ - and the optical powers of FE1, FE2 and relay mirrors - are determined based on: i) at the optically conjugated surfaces 144 and 144' the size of the image of FE1 and the size of the image of FE2 at the optically conjugate surface of the entrance pupil of the projection optics subsystem; ii) the angle of propagation of the chief ray and the marginal ray; iii) the size _h0 of the light source 216; iv) a v) the size h ₅ of the entrance pupil EP _; and vi) the separation distance t ₄ from the surfaces 144 and 144' to EP.

Examples of Lighting Units: Reflectors

One embodiment of the illumination unit assumes a 16.5 mm wide diamond-shaped exposure field (in one specific case - a 16.6 mm wide diamond-shaped field) on the workpiece/wafer enabling proper splicing of the exposure field. It is also assumed that zero-order diffracted light from the one-dimensional patterns (diffraction gratings) on reticles 144 and 144' is blocked such that beams 152A and 152B (representing the +1 and -1 diffraction orders at elements 144 and 144' order) optical interference doubles the spatial frequency at the workpiece/wafer and also enables near normal incidence illumination. (Appropriate blocking of the zeroth order diffracted beam may be achieved by the central visual barrier of the projection optics subsystem if desired).

Each of the fly-eye arrays (FE1, FE2) of mirrors 118 and 122 is configured as a two-dimensional array utilizing a respective corresponding two-dimensional array of mirror elements (alternatively referred to as "facets" or "eyes") captured and reflected from radiating objects (e.g., light source 216) The received radiant energy. Such an array of mirror elements or facets may be referred to as a "fly-eye mirror" (or even a "fly-eye lens," as it is sometimes called in the art), and normally requires no additional large with the aid of observation lenses and/or mirrors.

The arrangement and orientation of array FE1 700 (optical element 118 in FIGS. 1B and 1C ) is a trade-off between the number of constituent elements (sub-apertures) of the array, luminous flux, and dose uniformity. When a one-dimensional EUVD system utilizing an embodiment of a lighting unit configured in accordance with the inventive concept employs a single (secondary) light source 216, the lighting unit generally contains a single array FE1. However, in some embodiments, a lighting unit may employ multiple FE1 arrays, as described below.

The schematic diagram shown in FIG. 7A shows subapertures 710 (shown as a grid) superimposed on a plot of the irradiance distribution produced by IF 216 at a distance of about 100 millimeters below (along) the optical axis. The size and orientation of the sub-apertures (compared to the distribution shown in Figure 3A); the final size of the sub-apertures is scaled to match the actual IF distance. Figure 7B provides a corresponding schematic diagram of the sub-aperture 710 in angular space. Sub-apertures 710 located outside the outer boundary 714 of the irradiance distribution and sub-apertures located within the boundary 716 of the central visual barrier were not included in the actual implementation of the FE1 array because it was intended to reduce radiation dose uniformity. The arrayed mirror FE1 700 is optically conjugated to the surface of the patterned source or reticle 144 (see FIG. 6B ), so the rhomboid shape of the chosen sub-aperture 710 is the primary indicator of the shape of the irradiance distribution at the surface 144 . This shape of the individual sub-apertures of the fly-eye mirror FE1 was chosen on the basis of the idea that the exposure field on the workpiece 156 (during operation of the one-dimensional EUVD exposure tool) is biased by half the field width at a time such that at the workpiece 156 Each point of is exposed twice and receives the same radiation dose quantity. The practical goal here is to provide a uniform radiation dose over the workpiece while maximizing the optical efficiency of the optical system of the 1D EUV tool. Some itemized characteristics of an embodiment of the FE1 arrayed mirror are summarized in FIG. 7A .

Evaluation of the FE1 array also included calculation of the static irradiance distribution at the reticle by summing the distributions within each blue-outlined element and estimation by integrating the reticle irradiance in the y-direction Radiation scan dose. The steps of estimating dose uniformity and determining operationally acceptable non-uniformity (in one case - about 1%) when the sub-apertures are "bonded" together conclude the evaluation of the FE1 array mirror. Evaluation of the uniformity of the irradiance distribution at the optically conjugated surface 144 is shown in FIG. 7C as being better than about 0.5% over the entire surface of the FE1 array.

A schematic diagram 800 of FE2 array mirrors (eg, optical assembly 122 in FIGS. 1B, 1C ) configured to relay light from the FE1 array to reticle 144 is shown in FIG. 8 . When using a single light source 216 with a one-dimensional EUV system, the number of elements (sub-apertures) in FE2 array 800 is the same as the number of elements in FE1 array 700, so the process of designing FE2 800 is essentially identifying elements 810 such that The individual images of the secondary source IF 216 (formed by the combination of each element 710 and the respectively corresponding element 810 ) are substantially evenly distributed within the optimal illumination pupil 514 at the surface of the pattern source 144 . Thus, the shape of the outer boundary 824 of the embodiment 800 substantially corresponds to the shape of the outer boundary of the illumination pupil 514 .

The hexagonal shape of the sub-apertures 810 is actually a reasonable choice as such a shape provides dense uniform tiling of the surface of the FE2 array 800 . Figure 8 shows 200 sub-apertures or elements 810 (0.0136 arcs each in image space width), which fills an optimal etendue of 88%.

It should be understood that when only a single light source is used in embodiments of the one-dimensional EUV system, each sub-element or sub-aperture of the FE1 arrayed mirror projects an image of the source onto the FE2 arrayed mirror Associated/corresponding subelements or subapertures. In other words, there is a one-to-one correspondence between the elements of the two arrays, which fulfills two requirements: a) twice (or at least once about the y-axis) symmetry to maintain zero image shift about z-axis motion of the workpiece, Where reticles 144 and 144' are imaged onto the workpiece by the projection optics subsystem, and b) maximum pupil uniformity to reduce the source coherence (at FE2).

Embodiments of a lighting unit for use with multiple radiation sources

It should be noted, however, that embodiments of the lighting unit may be configured to operate not with one light source, but with multiple light sources, based at least in part on optical power considerations. Comparing, for example, the embodiments shown in FIGS. 1B and 1C , in which a single light source 114 is schematically indicated, and with further reference to FIG. 9 , a particular example of a lighting unit 900 is shown configured to operate with multiple light sources. Here (and with reference to the illustration of secondary light source IF 216 in FIG. 2B ) two light sources are shown that provide light to the lighting unit: 216-A and 216-B.

A specific instance of illuminator 900 is configured to provide:

- blade-shaped illumination pattern selected for maximum incoherence of light without contrast loss (for one-dimensional patterns with a period of tens of nanometers); - two first "fly-eye" mirrors Arrays FE1-A and FE1-B (shown as 910-A and 910-B, each containing subapertures or individual constituent mirror element 910); - a single second "fly's eye" mirror array FE2, 922, configured from tiles formed by individual hexagonal constituent mirror elements 922-i to define blade-like apertures (shown in FIG. 8 824) and efficiently combine the light inputs LA and LB received from the plurality of light sources 216-A and 216-B, and the curved relay mirrors 126 and 926, while maintaining etendue, as part of the illumination unit (when configured according to the design shown in FIG. 1B; relay 926 is not shown in FIG. 9); as shown, light from light source 216-A is captured by mirror FE1-A; light from light source 216-B The light is captured by mirror FE1-B; the light reflected by FE1-A and FE1-B is captured by FE2. Each individual mirror element or sub-aperture forms an image of a corresponding irradiating object as seen from the perspective of the position of the individual sub-aperture. Stated differently, in this embodiment there is a unique element in either FE1-A or FE1-B (but not both) associated with each element of FE2. Thus, as implemented, each of the individual mirrors of FE1-A and FE1-B has a respective corresponding mirror element in the arrayed mirror of FE2. For example, individual mirror 910-i of array FE1-A forms an image of light source 216-A at individual mirror 922-i of array FE2, while individual mirror 910-j of array FE1-B forms an image of light source 216-A at individual mirror 922-i of array FE2. An image of light source 216-B is formed at individual mirror 922-j.

It should be appreciated that the proposed embodiment 900 of the lighting unit provides an image plane 934 between the FE-2 reflector 922 and the relay mirrors 126, 926 (if present). This plane is optically conjugate to both the plane of the pattern source 144 and the workpiece/wafer 156 (see FIGS. 1B and 1C ) and provides the proper location for positioning (variable size as appropriate) The aperture 160 controls the dose of radiation power delivered to the reticle 144 and defines the boundaries of the exposure field formed at the wafer. If no relay mirrors (126, 926) are present, the pattern sources 144 and 144' with the diffraction gratings on them are placed at plane 934. For additional information on this design, the reader is referred to, for example, the examples disclosed in US patent application Ser. No. 15/599,148.

As shown, FIG. 9 shows tilted elements (sub-apertures) 922-i of FE2 arrayed mirrors 922 configured to produce FE1-i on reticle/pattern source 144. A, Overlapping images of elements (sub-apertures) 918-i and 918-j of FE1-B arrayed mirrors (possibly via some additional relay optics, such as relay mirror 126). However, the same effect can also be achieved by placing the elements 922-i of the FE2 arrayed mirror 922 on a suitably curved convex surface. In practice, it may additionally be necessary to "scramble" the fly's-eye mirror optical pathway (so that both the mirrors in the array of FE1 and FE2 in the sub-mirror elements that make up the array have many different tilts) to produce uniformity of the pupil sex.

The aperture 824 defined by the second array of FE mirrors 800 and 922 is not necessarily limited to a vane shape. For example, in a related embodiment, it may be bow-tie shaped (rectangular shaped). At this time, the mirror arrays 800 and 922 may have different sizes in two orthogonal directions.

Those skilled in the art will readily recognize that in each of the designs described above (one of the mirror arrays containing a single light source 216 and a single FE1, and one containing more than one light source and each corresponding to more than one FE1 One of the arrayed mirrors), there is light propagating from the EUV source through the illumination unit towards the reticle/pattern source (EUV radiation) no more than three consecutive reflections of the beam (and in the absence of the relay mirror 126 there are only two reflections, see the embodiment shown in FIG. 1C ), which is more complex than the prior art Designed to produce dramatic improvements in optical transmission. Each mirror employed in the EUV spectral region typically has a reflectivity of only 65% to 70%. The number of reflections is thus reduced by approximately half compared to existing designs used in general EUV machines, thus roughly doubling the amount of light transmitted via the illumination unit of embodiments of the present invention compared to general EUV systems. Indeed, the transmission through the system can be estimated as a value of X^N, where X is the typical reflectivity (65-70%) and N is the number of reflections. In conventional general purpose EUV systems, the illumination unit has at least five (or more) mirrors arranged in sequence, while one embodiment includes as few as only three or less mirrors. Thus, for an embodiment of the present invention, the transmission of an embodiment of the illumination unit increases from about 11% to 17% (for a generic EUV system with five mirrors) to about 27% to 34%.

The operational improvements are even more pronounced once the presence of the projection optics subsystem is taken into account. Indeed, a typical projection optics subsystem of a typical general-purpose EUV tool employs about six mirrors, while only two mirrors (primary and secondary) are used in embodiments of the present invention. See, eg, PCT/US2018/027785. In this case, a transmission rate of 0.9% to 2% for a typical general purpose EUV system (which includes transmission through the illumination unit and projection optics, but does not include the presence of a reticle) is using embodiments of the present invention increases by an order of magnitude to about 12% to 17%.

An embodiment of a monolithic string of optical elements.

The purpose of the flat pattern source.

11A provides a schematic illustration of an overall on-optical-axis optical element string 1100 of a one-dimensional EUV system configured to incorporate a substantially one-dimensional optical element disposed on a flat substrate of a pattern source 144. A pattern (eg, a diffraction grating with a period of tens of nanometers) is imaged on the workpiece 156 . (For this reason, the diagram shown in FIG. 11A substantially corresponds to the diagram shown in FIG. 1B ). In FIG. 11A , the ray connecting the "edge" of the source 210 with the "edge" of the relay mirror 126 is shown and may be considered a chief ray. The function of the relays 126 and 926 is to image the uniform distribution of irradiance on the arrayed mirror FE2 onto the pattern source 144 . Numeral 1120 designates the location of the plane that is optically conjugate to the flat pattern source 144 .

Referring again to FIG. 11A , the optical path ( Indicated by dotted line) folds in the first plane. The two EUV beams representing different diffraction orders formed at the substantially one-dimensional pattern of the pattern source 144 as a result of diffracting the EUV beam incident on the pattern source from the relay mirror are approximately transverse (and in particular case - orthogonal) propagates in the second plane of the first plane.

It should be noted—with reference to the embodiments shown in FIGS. 1B , 1C and according to the schematic diagram shown in FIG. 11A—that the plane of symmetry of the one-dimensional EUV systems 102, 170, and 1100 is preferably parallel to the yz plane (as drawn in the local coordinate system ) to reduce the angle of incident EUV radiation on each mirror, which increases the reflectance value that can be achieved during operation of the system. Such an arrangement advantageously minimizes the overall number of mirrors disposed in the optical path from the light source to the reflective mask. It should be noted that in this configuration, FE2 The axis along which the mirror array has a larger extent (shown as the Y coordinate in FIG. 8 ) and the axis along which the lines of the substantially one-dimensional pattern of the pattern source extend may lie in the first plane.

Although specific values and examples were chosen in this disclosure, it should be understood that the values of all parameters may be varied over wide ranges to suit different applications within the scope of the invention as claimed. For example, in a related embodiment, pattern source 144 may be located in a sub-aperture of arrays 118 and 700 (i.e., in the individual constituent reflective elements of arrays 118 and 700)—for example, in center 1010 of array FE1 in the space provided, as seen in Figure 10A.

11B is a schematic diagram showing the optical path of EUV radiation within the illumination unit portion of optical element string 1100 in a plane perpendicular to the plane in which a diffracted beam of radiation is formed at patterned source 144 . Here, the relay mirror 126 operates at a magnification of -1; and the mirrors 134, 130 of the projection optics objective are shown in dashed lines. As is apparent from FIG. 11B , the divergent beam from the intermediate focal point IF (source 114 , secondary source 216 ) is incident on FE1 . Each reflective element of FE1 reflects and converges the incident light beam to form a point of convergence on or near the reflective surface of FE2. These points are substantially optically conjugate to the intermediate focal point IF. The light beams reflected by the reflective surfaces of FE2 overlap each other on surface 1120 . This surface 1120 may be a surface optically conjugate to the surface of the pattern source 144 . The light beam passing through surface 1120 is reflected by relays 126 and 926 and reaches pattern source 144 . Here, the location optically conjugate to the pattern source 144 (a portion of the surface 1120 ) may be located on one side of the pattern source 144 . In addition, the light beams from FE2 reaching relays 126 and 926 may approach the optical axis in their propagation (in Fig. where is a one-dot chain line). The light beam from FE1 to FE2 may approach the optical axis (dot chain line in the diagram) as it progresses. Relays 126 and 926 may be positioned with their axes inclined relative to the optical axis of projection objective PO (indicated by the two optical elements 134 and 130 shown in dashed lines). In other words, the reflective surfaces of relays 126 and 926 may be inclined relative to the optical axis of the PO. The direction along which the principal ray of light (principal ray) reaches pattern source 144 from relays 126 and 926 may be substantially parallel to the optical axis of projection objective PO.

The usage of the curved pattern source.

The use of a curved pattern source 144' (i.e., a pattern source whose substantially one-dimensional pattern is disposed in a curved surface in contrast to the use of a substantially planar pattern source 144) makes the projection optics of a one-dimensional EUV lithography tool The length of the subsystem is substantially reduced (and, for example, a variation of the projection optics subsystem as discussed in reference to FIG. 12 of 62/487,245 can then be employed).

To this end, referring to FIGS. 14A and 14B , in a specific design of the optical element string of a one-dimensional EUV system, there are curved pattern sources arranged in the individual reflective elements of the first reflector of the illumination unit 1400, in this case , the radiation received by mirror 1400 from radiation source 126 is diverted to mirror array 1450 (which is substantially identical to mirror 800 and which in turn forwards the radiation directly to pattern source 144', where the pattern source is substantially When flat there are no relay mirror elements 126) in the system. In the specific design shown in FIGS. 14A and 14B , about forty reflective elements 1410 of fly-eye array mirror FE1, 1400 are amplified by about forty reflective elements 1460 (of fly-eye mirror FE2, 1450 ) in units of rate optical imaging to the pattern source 144' superior. Element 1410 of FE1 is generally configured with an elliptical or spherical surface. In one specific embodiment, the curved pattern source 144' may comprise a one-dimensional phase diffraction grating that is about 20 mm to 30 mm wide (corner to corner; in one case - about 25 mm) with a width of about 450 mm. to a radius of curvature of 490 millimeters (in one case - about 473 millimeters), and has a sag of about 400 microns to 800 microns (in one case - about 660 microns). The individual reflective elements 1460 of FE2 are spherical with substantially equal radii of curvature, but tilted at different angles relative to a selected reference to place the image of the individual elements 1410 on the pattern source 144'. The specifically designed element 1460 has a radius of curvature of about 410 millimeters to about 430 millimeters (in one instance - about 419 millimeters) and a diameter of several millimeters (in one instance - about 2.3 millimeters). In FIG. 14B, the shape of the reflective surface of the reflective element 1460 may be hexagonal. The plurality of reflective elements 1460 may be formatted into a spatially closely packed array.

A specific non-limiting embodiment 1500 of a string of optical elements for a one-dimensional EUV system comprising a curved patterned source 144' disposed in the center of the FE1 mirror array is shown in FIG. Here, a fold mirror 1510 is used to forward the EUV radiation flux 1520 received from the EUV radiation source towards mirror 1400 which further reflects the EUV radiation towards mirror 1450 which in turn images mirror 1400 into a pattern source 144' on. The pattern source 144' projects the radiation towards the primary mirror M1 and further towards the secondary mirror M2 of the projection optics subsystem by diffracting the radiation, which forms the optical pattern of the pattern source 144' on the surface of the workpiece 156. image. In this design, the mirror 1450 is used to block the zeroth order diffraction of the EUV radiation formed at the pattern source 144' from propagating towards the projection optics subsystem and entering the projection optics subsystem. This additional purpose of the system.

It will be appreciated that, as in the case of the embodiment shown in FIG. 11A , the mirror array 1400 containing the patterned source 144' in its individual mirror element 1410 is optically conjugate to the patterned source 144' (see optical system). Thus, the shape of the individual mirror elements 1410 of the array 1400 is a primary indicator of the shape of the irradiance distribution of EUV radiation at the patterned source 144'. When the overall shape of the pattern source 144' and the individual elements 1410 is a rhomboid, for each pass of the scanner of the one-dimensional EUV system over the workpiece, the exposure of the workpiece 156 to EUV radiation is offset by half of the exposure field, Each point on the workpiece is exposed twice and receives the same radiation dose. By configuring the exposure system and process in this manner, the goal is to provide an extremely uniform radiation dose over the workpiece while maximizing the radiation efficiency of the overall system.

Furthermore, it should be understood with reference to Figure 15 that the preferred location of the FE2 mirror array 1450 may be on the axis of the system. In related embodiments, the substrate supporting the array of FE2 mirrors may be a substantially planar substrate or a spatially curved substrate. In general, the curved pattern source or reticle 144' can be aligned on the optical axis of the system or located off-axis of the system. Although the schematic diagram shown in FIG. 15 shows that the angle at which radiation 1520 is incident on fold mirror 1510 is substantially different from normal incidence, in a related embodiment, a one-dimensional EUV system can be configured to ensure radiation 1520 flux as much as possible. The angle of incidence on the fold mirror 1510 may be close to normal incidence to increase the reflectivity in the specified wavelength range. In another related embodiment, the one-dimensional EUV system can optionally be configured such that the incidence of radiation 1520 on folding mirror 1510 is substantially grazing incidence. In yet another related embodiment, a one-dimensional EUV system can be configured to avoid Fold mirrors are avoided and radiation from the EUV source is delivered directly onto the FE1 mirror 1400 array.

In general, it should be understood that radiation delivered by the substantially one-dimensional pattern (e.g., a diffraction grating pattern) of the pattern source 144, 144' is directed by an embodiment of the projection optical objective (e.g., as described in PCT/US2018/027785). discussed) are projected onto the image plane (the surface of the workpiece 156). In this embodiment (referring to the specific design shown in FIGS. 7A, 7B, 8, 10A, 10B, 14A, 14B), in general

- the spatial extent FE1-D of the FE1 arrayed mirror consisting of rhomboid sub-apertures of about 14 mm on a side is in the range of about 220 mm and 270 mm (in one embodiment - about 240 mm) ;- the spatial extents FE2-D and FE2-d of the arrayed mirrors corresponding to FE2 are located between about 60 mm and 85 mm along the major axis of the "blade" of the mirror, respectively, and about 85 mm along the short axis of the "blade" Between 20mm and 30mm. (In one embodiment - 78 mm and 25 mm respectively). In such an example, the extent of the individual hexagonal mirror elements 810 of the FE2 arrayed mirror is about 3 millimeters; and - the concave relay mirror 126 has a radius of curvature between about 1900 millimeters and about 2300 millimeters (about 2190 mm in a specific example), a major axis diameter between about 140 mm and 180 mm (about 160 mm in a specific example), and a minor axis diameter between about 65 mm and 85 mm ( In a specific example - about 75 mm).

In one embodiment, the bits from the vertices of the collector 210 to the image plane 156 The overall length of the system was measured to be about 3 meters.

In one embodiment, the power requirement for the secondary light source 216 is estimated to be approximately 51 watts based on the following assumptions: a) Six mirrors in the optical system - FE1, FE2, relay mirrors of the projection optics subsystem, with a 3D patterned reticle, and primary and secondary mirrors - about 65% reflectivity on each; b) 30 ^mJ /cm resistance at image plane at workpiece/substrate; c) illumination unit has a geometric efficiency of 85%; d) a one-dimensional patterned grating of a reticle has a diffraction efficiency of 25%; e) a one-dimensional EUVD exposure system has a throughput of 100 workpieces per hour; and f) 10 per workpiece or wafer seconds of acceleration and overhead.

Referring again to FIGS. 11B , 11A and 15 and with further reference to FIGS. 12A , 12B, the EUV radiation beam 148 from the radiation source is delivered to the pattern by the last mirror in the order of mirrors present in a given embodiment of the lighting unit. On-axis points of sources 144 and 144' (ie, points of pattern sources 144 and 144' on optical axis AX, see Fig. 12A) or off-axis points of pattern sources 144 and 144' (see Fig. 12B). (In embodiments employing flat pattern source 144, this last mirror in the sequence is typically relay mirror 126, while in embodiments employing curved pattern source 144', this last mirror is typically Two fly-eye reflectors 122). The radiation is then diffracted at the substantially one-dimensional patterns of pattern sources 144 and 144' to form two diffracted beams 152A and 152B that propagate on opposite sides of beam 148. (In other words, the beam of EUV radiation incident on the patterned source from the last mirror of the IU unit forms two beams at the patterned source as a result of diffraction of this incident beam on the substantially one-dimensional pattern of the patterned source. propagating between diffracted beams).

Referring now to FIGS. 15 , 17A, 17B, 17C, and 17D, FIGS. 17A-17D illustrate a portion of an embodiment of a one-dimensional EUV system that includes a first array of fly-eye mirrors FE1 and a second An illumination unit of fly's eye mirror array FE2; a pattern source 144' containing a substantially one-dimensional pattern on a curved surface; and a projection optics subsystem including mirror elements M1 and M2. Here, Figure 17A shows the optical path of EUV radiation from the FE2 mirror array to the curved reticle 144'; Figure 17B shows the EUV radiation from the FE1 mirror array via the curved reticle 144' to the mirrors of the projection optics subsystem. Optical path of M1; FIG. 17C shows the optical path of radiation from the FE1 mirror array to the image plane at the workpiece 156 (here, only the chief ray is shown in the optical path from FE1 to the curved reticle 144′) and FIG. 17D shows the optical path of radiation from the curved reticle 144' to the image plane 156. These optical path diagrams are presented in a plane parallel to the plane in which the beam of EUV radiation diffracted at the curved reticle 144' propagates.

Thus, those skilled in the art will readily appreciate that the disclosed embodiments of an illumination unit and a one-dimensional EUV lithography system employing such an illumination unit represent an integral reflective system configured to bear substantially the same A spatially curved reflection pattern source for dimensional patterns is used in conjunction with:

- When a single EUV radiation source is used, such reflective illumination unit system comprises a combination of only two (and no other) optical mirrors arranged in sequence relative to each other, said optical mirrors being used to EUV radiation on one optical assembly (from the only three optical assemblies) is transferred to the pattern source. The first optical reflector is a first fly-eye array individually constituting reflective elements. The second optical mirror is Individually in operation receiving EUV radiation from the first fly's eye mirrors constitutes a further second array of fly's eye mirrors of reflective elements. Each of the only two optical mirrors has a corresponding non-zero optical power. This combination of only three mirrors is arranged in a substantially fixed spatial and optical relationship relative to the pattern source. (The grouping of optical elements including both the combination of the only two optical assemblies and the pattern source also forms and defines another reflective system.) The epi-illumination unit represents the illumination unit of a one-dimensional EUV exposure tool that comprising a projection optics subsystem having a reference axis and configured to form the pattern source with a reduction factor of N>1 using only two beams of radiation on an image plane optically conjugate to the pattern source optical image. When the EUV radiation is transferred onto the flat patterned source via the illumination unit, the only two beams of radiation originate at the spatially curved patterned source. The projection optics subsystem of the supplementary illumination unit is a reflective projection optics subsystem comprising only primary and secondary reflectors. At least one of the only two optical components of the lighting unit includes a fly's eye (FE) reflector. In one embodiment, a pattern source is positioned in (at least partially surrounded by) individual constituent reflective elements of such a fly's eye mirror. Pattern sources may include phase shift masks.

In addition, the system described above can be used to fabricate semiconductor devices using the process schematically shown in FIG. 13A. In step 1301, functional and performance characteristics of the device are planned. Next, in step 1302, a mask (reticle) with a substantially one-dimensional pattern (as described above) is designed according to the previous design step 1301, and in a parallel step 1303, a workpiece is fabricated from silicon material. In step 1304, the photolithography system using the above-mentioned one-dimensional EUV optical device will form the result of step 1302 The mask pattern is exposed to the illumination radiation and an image of this pattern is transferred onto and formed in the workpiece. In step 1305, the semiconductor device is assembled (including dicing process, bonding process and packaging process), and finally in step 1306, the device is then inspected.

Figure 13B provides an example of a detailed flowchart detailing step 1304 described above. As shown, at step 1311 (oxidizing step), the surface of the workpiece is oxidized. In step 1312 (CVD step), an insulating film is formed on the surface of the workpiece. In step 1313 (electrode forming step), electrodes are formed on the workpiece by vapor deposition. In step 1314 (ion implantation step), ions are implanted into the bulk of the workpiece. The steps 1311 to 1314 described above form the preprocessing steps of the workpiece during its processing, and at each step the selection of operating parameters is made according to the processing requirements.

At each stage of workpiece processing, when the above-mentioned pre-processing steps have been completed, the following post-processing steps may be implemented. During post-processing, first in step 1315 (photoresist formation step), a photoresist is applied to the workpiece. Next, in step 1316 (exposure step), the circuit pattern of the mask (reticle) is transferred to the workpiece using the exposure apparatus described above. Then in step 1317 (developing step), the exposed workpiece is developed, and in step 1318 (etching step), portions other than the remaining photoresist (exposed material surface) are removed by etching. In step 1319 (photoresist removal step), unnecessary photoresist remaining after etching is removed. A plurality of circuit patterns are formed by repeating these pre-processing and post-processing steps.

For purposes of this disclosure and the appended claims, the terms "substantially," "approximately," "approximately," and similar terms when referring to descriptors of a value, element, property, or characteristic are intended to emphasize Those skilled in the art should understand that reference to A stated value, element, property or characteristic, while not necessarily identical to what is stated, can for practical purposes be considered to be identical to what is stated. These terms mean, for example, "almost", "mainly", "substantially", "substantially", "essentially", "substantially", "approximately" when applied to a given characteristic or quality descriptor The same but not necessarily the same throughout" is used to represent reasonably similar language and to set forth a specified characteristic or descriptor such that its scope will be understood by those skilled in the art. In one specific instance, the terms "approximately", "substantially" and "approximately" used in reference to a numerical value mean a range of plus or minus 20%, more preferably plus or minus 10%, or even A range of plus or minus 5%, preferably plus or minus 2%. As a non-limiting example, two values that are "substantially equal" to each other imply that the difference between the two values may be within +/- 20%, preferably +/- 20% of the value itself, preferably +/- /-10%, more preferably within +/-5% of the value itself, and even better within +/-2% or less of the value itself.

These terms used in describing selected properties or concepts neither imply nor provide any basis for uncertainty or imposition of numerical limitations on specified properties or descriptors. As will be understood by those skilled in the art, actual deviations from the exact value or characteristic of a stated value, element or characteristic from that stated may fall within and may vary within a numerical range defined by experimental measurement error. , said experimental measurement error is generally present when using measurement methods accepted in the art for such purposes.

For example, a reference to an identified vector or line or plane being substantially parallel to a reference line or plane should be understood to mean that a vector or line or plane is identical to or very close to a reference line or plane (existence is deemed to be actually in Typical self-referencing lines in the related art Or the angular deviation of the plane, such as between 0 degrees and 15 degrees, preferably between 0 degrees and 10 degrees, more preferably between 0 degrees and 5 degrees, even more preferably between 0 degrees degrees and 2 degrees, and optimally between 0 degrees and 1 degree). For example, a reference to an identified vector or line or plane being substantially perpendicular to a reference line or plane is to be understood as meaning that the normal to the surface of a vector or line or plane is at or very close to the reference line or plane or plane (there is an angular deviation from a reference line or plane that is considered to be practical in the related art, for example, between 0 degrees and 15 degrees, preferably between 0 degrees and 10 degrees, more preferably between 0 and 5 degrees, even better between 0 and 2 degrees, and most preferably between 0 and 1 degrees). For example, the use of the terms "substantially flat" or "planar" in reference to a given surface implies that the surface may have certain irregularities and/or roughnesses that are sized and expressed, as in The particular situation under consideration will be commonly understood by those skilled in the art.

Other specific examples of the meaning of the terms "substantially," "about," and/or "approximately" as applied to different practical contexts may have been provided elsewhere in this disclosure.

Embodiments of the system generally include electronic circuitry (eg, a computer processor) controlled by instructions stored in memory to perform the specific data collection/processing and calculation steps described above. The memory can be random access memory (random access memory, RAM), read-only memory (read-only memory, ROM), flash memory or any other suitable for storing control software or other instructions and data memory, or a combination thereof. Those skilled in the art should easily understand that the instructions or programs defining the operations of the embodiments of the present invention may include but are not limited to the following The form is delivered to the processor: permanently stored on a non-writable storage medium (for example, a read-only memory device (such as ROM) within a computer, or a device that can be read by a computer I/O accessory (such as a CD-ROM or DVD)), information stored on writable storage media (such as floppy disks, removable flash memory, and DVD drives), or via communication media (including wired or wireless computer networks) way) is sent to the computer information. Furthermore, although the present invention may be implemented as software, the functions necessary to practice the methods of the present invention may optionally or alternatively be implemented in part or in whole with firmware and/or hardware components (e.g., combinational logic, Application Specific Integrated Circuit (ASIC), Field-Programmable Gate Array (Field-Programmable Gate Array, FPGA, or other hardware) or some hardware, software, and/or firmware components Composite implementation.

It is intended that the scope of the invention described in the claims attached to this disclosure be assessed in light of the overall disclosure. Those skilled in the art may make various changes to the described details, steps and components within the spirit and scope of the invention.

Various modifications and changes may be made to the illustrated embodiments without departing from the inventive concepts disclosed. Furthermore, disclosed aspects or portions of these aspects may be combined in ways not listed above. Accordingly, the invention should not be seen as limited to the disclosed embodiments.

100: 1D EUV system

Claims (17)

A reflective system for use with a reflective pattern source carrying thereon a substantially one-dimensional pattern, the reflective system comprising: an illumination mirror disposed between a source of EUV radiation and the reflective pattern source, the an illumination mirror directing EUV radiation from the EUV radiation source to the reflective pattern source; and a projection mirror disposed between the reflective pattern source and the workpiece, the projection mirror transmitting the A diffracted beam of a reflective pattern source is directed to the workpiece, wherein the illuminating mirrors include a first mirror and a second mirror closest to the reflective pattern source among the illuminating mirrors, and wherein from the second mirror to A first radiation path of the reflective pattern source is positioned between a second radiation path from the first mirror to the second mirror and a third radiation path of the diffracted beam. The reflective system as described in claim 1 of the scope of the patent application, wherein the second radiation path is positioned on one side of the first direction of the first radiation path, and the first direction and the reflection pattern source as the source The second direction of the periodic direction is orthogonal. The reflective system according to claim 1, wherein the second radiation path is inclined relative to the optical axis of the projection mirror. The reflective system of claim 3, wherein the first radiation path is positioned along the optical axis. The reflective system as described in item 3 of the scope of the patent application, wherein the third A radiation path is parallel to the first radiation path in a first direction, and the first direction is orthogonal to a second direction that is a periodic direction of the source of the reflective pattern. The reflection system described in item 1 of the scope of the patent application, wherein the first mirror is arranged above the reflection pattern source. The reflection system according to claim 6 of the patent application, wherein the second mirror is arranged between the projection mirrors. The reflective system according to claim 1, wherein the second radiation path is arranged next to the reflective pattern source. The reflective system as described in item 1 of the patent scope of the application, wherein the distance between the first mirror and the second mirror in the first direction is smaller than the distance between the first mirror and the second mirror The distance in the direction of the optical axis of the projection mirror. A lithographic exposure tool, comprising: the reflective system described in item 1 of the scope of the patent application, which forms a stripe pattern on the workpiece; and a wafer stage, which is used to hold the workpiece and move along the scanning direction. The lithographic exposure tool according to claim 10, wherein the scanning direction is perpendicular to the periodic direction of the stripe pattern. The lithography exposure tool according to claim 11, wherein the fringe pattern is spatially fixed relative to the projection mirror. The lithographic exposure tool according to claim 12, wherein the workpiece moves relative to the spatially fixed fringe pattern. The lithographic exposure tool as described in item 12 of the scope of the patent application, wherein When the wafer stage moves, the reflective pattern source is spatially fixed. The lithography exposure tool as described in claim 10, wherein the stripe pattern is formed at the optical conjugate point of the reflective pattern source. A method of forming a stripe pattern on a workpiece, comprising: generating EUV radiation; directing the EUV radiation to a reflective pattern source through an illumination mirror; directing a diffracted beam from the reflective pattern source generated by irradiating the EUV radiation directed to said workpiece; and forming said fringe pattern for use with said diffracted beam, wherein said illuminating mirrors comprise first and second mirrors among said illuminating mirrors closest to said reflection pattern source, and wherein the first radiation path from the second mirror to the reflective pattern source is positioned between the second radiation path from the first mirror to the second mirror and the third radiation path of the diffracted beam between. A method of manufacturing a micro device, comprising: providing a workpiece; forming the stripe pattern on the surface of the workpiece by using the method described in claim 16; and processing the workpiece.

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