CN117348338A - Mask defect detection device and method - Google Patents
Mask defect detection device and method Download PDFInfo
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- CN117348338A CN117348338A CN202311297954.9A CN202311297954A CN117348338A CN 117348338 A CN117348338 A CN 117348338A CN 202311297954 A CN202311297954 A CN 202311297954A CN 117348338 A CN117348338 A CN 117348338A
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- 238000001514 detection method Methods 0.000 title claims abstract description 56
- 230000007547 defect Effects 0.000 title claims abstract description 51
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- 238000003384 imaging method Methods 0.000 claims abstract description 47
- 230000001105 regulatory effect Effects 0.000 claims abstract description 10
- 230000005540 biological transmission Effects 0.000 claims description 14
- 210000001747 pupil Anatomy 0.000 claims description 14
- 238000002955 isolation Methods 0.000 claims description 10
- 230000003287 optical effect Effects 0.000 claims description 7
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- 238000007689 inspection Methods 0.000 claims description 2
- 230000008859 change Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 230000001427 coherent effect Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 238000001900 extreme ultraviolet lithography Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
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- 230000015572 biosynthetic process Effects 0.000 description 2
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- 239000002245 particle Substances 0.000 description 2
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- 230000005469 synchrotron radiation Effects 0.000 description 2
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- 230000009286 beneficial effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
- G03F1/82—Auxiliary processes, e.g. cleaning or inspecting
- G03F1/84—Inspecting
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/956—Inspecting patterns on the surface of objects
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/105—Scanning systems with one or more pivoting mirrors or galvano-mirrors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/956—Inspecting patterns on the surface of objects
- G01N2021/95676—Masks, reticles, shadow masks
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- Optics & Photonics (AREA)
- Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
- Preparing Plates And Mask In Photomechanical Process (AREA)
Abstract
The invention provides a mask defect detection device and a method, wherein the detection device comprises a shell with a vacuum cavity; a mask driving assembly for placing a mask to be inspected; an illumination system comprising a galvanometer assembly and a zone plate; the vibration mode of the vibrating mirror assembly is regulated to control the scanning track of the reflected light beam to the zone plate and form a certain pattern; the off-axis zone plate is arranged on a reflection light path of the mask plate and is used for receiving reflection light from the mask plate and imaging the reflection light at an image plane; and the detector is arranged at the image plane and is used for receiving the imaging light beam of the off-axis zone plate. The invention aims to overcome the defect that a mask defect detection device is difficult to adapt to various different extreme ultraviolet light sources, is applicable to the light sources under various different extreme ultraviolet light parameters, is also applicable to different mask patterns, avoids the excessive dependence of the mask defect detection device on a certain light source, and improves the use flexibility of the device.
Description
Technical Field
The present invention relates to the field of semiconductor lithography, and more particularly, to a mask defect detection apparatus and method.
Background
In the photolithography process, the photomask is the "negative" of the chip circuitry, and its quality directly determines the reliability and yield of the integrated circuit chip. If there are particles or scratches on the mask, or the design of the pattern is wrong, the particles or scratches are projected and copied onto the wafer, resulting in low yield of chip fabrication. Therefore, the quality of each stage of mask production must be sufficiently reliably detected for use in a lithographic projection process for chip production. In EUV lithography (Extreme ultraviolet lithography), EUV light waves have a strong penetration depth in multilayer film reflection during lithographic mask projection, so that mask defects buried in the multilayer film can also affect the final effect of projection.
With the development of EUV lithography, in existing EUV mask inspection apparatuses, EUV light sources based on different generation principles are also becoming mature, including: a higher harmonic light source, the EUV light wave produced by the light source being characterized by high coherence; a synchrotron radiation light source based on a synchrotron radiation accelerator science device, the properties of EUV light formed according to different inserts also being different; an LPP/DPP light source, which emits EUV light waves based on plasma, is an EUV lithography machine manufactured by ASML company.
The parameters such as coherence, energy density, divergence and the like of the extreme ultraviolet light between the different light sources are different, but the design of the illumination system of the mask defect detection device in the prior art is manufactured based on the property of the beam line of the specific light source, so that the same mask defect detection device is difficult to adapt to multiple different extreme ultraviolet light sources, such as using different detection devices for different light sources, the cost is high, or when different light sources are utilized on the same detection device, the imaging quality and the detection efficiency cannot be ensured due to the incompatibility and the like, and therefore, the current mask defect detection device cannot meet the development requirement of the current mask defect detection.
Disclosure of Invention
The invention aims to overcome the defect that a mask defect detection device is difficult to adapt to a plurality of different extreme ultraviolet light sources, and provides a mask defect detection device and a mask defect detection method. The invention can be suitable for light sources under various extreme ultraviolet parameters, is also suitable for different mask patterns, increases the imaging resolution of mask detection, avoids the excessive dependence of a mask defect detection device on a certain light source, and improves the flexibility of the device in use.
In order to solve the technical problems, the invention adopts the following technical scheme:
a mask defect detection apparatus comprising:
the shell comprises a vacuum cavity, and an entrance opening which is arranged on the shell and used for injecting extreme ultraviolet light into the vacuum cavity;
the mask driving assembly is arranged in the vacuum cavity and is used for placing a mask plate to be detected;
the illumination system comprises a galvanometer assembly, wherein the galvanometer assembly comprises a reflecting mirror for reflecting extreme ultraviolet light and a galvanometer which is connected with the reflecting mirror and used for changing the ray direction and the position of a reflected light beam; the illumination system further comprises a zone plate, wherein the zone plate is positioned between the galvanometer assembly and the mask driving assembly and is used for focusing the reflected light beam to the mask to be detected to form light spots; the vibration mode of the vibrating mirror assembly is regulated to control the reflected light beam to scan onto the zone plate and form a certain filling pattern;
the off-axis zone plate is arranged on a reflection light path of the mask plate and is used for receiving reflection light from the mask plate and imaging the reflection light at an image plane;
and the detector is arranged at the image plane and is used for receiving the imaging light beam of the off-axis zone plate.
The invention adopts the illumination system formed by the galvanometer component and the zone plate, is compatible and applicable to extreme ultraviolet light with different light sources, ensures the luminous flux density of the extreme ultraviolet light on the mask plate, and can improve the mask defect detection performance and efficiency. The basic principle of the lighting system is as follows: by utilizing a Fourier synthesis technology, the vibration direction of the vibrating mirror is reasonably designed to change the scanning track on the zone plate, different filling patterns are formed, and the numerical aperture NA of the illumination side is controlled c (i.e., from the reticle to the zone plate side), and then coherent control of the illumination system may be performed:
wherein σ is the coherence factor of the system, NA c For illumination side numerical aperture (i.e. from reticle to zone plate side), NA o For the imaging side numerical aperture (i.e., from the mask to the off-axis zone plate side), the system is incoherent illumination when the coherence factor σ= infinity, and coherent illumination when σ = 0.
The invention utilizes the characteristics that the vibration of the vibrating mirror can change the direction and the position of light, controls the vibration in the horizontal and vertical directions by changing the voltage or the current of the vibrating mirror, and realizes accurate light path control, thus, extreme ultraviolet light is reflected by the vibrating mirror assembly, scans the filling zone plate, and changes different scanning modes by adjusting the vibration of the vibrating mirror, and the vibrating mirror assembly can scan the zone plate according to a certain scanning mode, thereby controlling the numerical aperture of the zone plate to the mask, and realizing the free adjustment of the numerical aperture in a certain range; the illumination system proposal of the invention flexibly adjusts the filling patterns of the vibrating mirror assembly to the zone plate according to different complex mask patterns, and the filling of the zone plate with different illumination patterns can be suitable for the light sources under various extreme ultraviolet parameters, is also suitable for different mask patterns, improves the process window of mask detection, enhances the imaging resolution of mask detection, avoids the excessive dependence of mask defect detection devices on a certain light source, and improves the flexibility of device use.
In addition, the mask driving assembly completes carrying, sampling, fixing, aligning, sample changing and the like of the mask in a vacuum environment, the mask driving assembly is provided with at least a two-dimensional motion electromechanical system, the mask is horizontally placed, and the driving device is used for completing posture adjustment, alignment and the like; second, the vacuum degree of the vacuum chamber of the shell should be generally less than 10 -7 torr。
Further, the vibration isolation platform is used for bearing the shell. The mask defect detection has very strict vibration requirements on the system, so that the whole device needs to be subjected to vibration isolation, the root mean square of vibration isolation of a vibration isolation platform at 1Hz is not more than 3nm, and a stable exposure environment is provided for the mask defect detection.
Further, the reflecting mirror plane on the galvanometer component and the sample plane on the mask plate are in a pair of conjugate relations relative to the zone plate, when the light spot size on the galvanometer component is fixed, the light spot size on the mask plate can be regulated and controlled according to the object image relation, and the light spot on the galvanometer component and the light spot on the mask plate meet the following object image relation:
wherein:
wherein D is a Spot diameter at galvanometer, D b Spot diameter at reticle, L 1 -object distance, L, from the plane of the galvanometer to the plane of the zone plate 2 -image distance from the plane of the zone plate to the plane of the reticle, focal length of f-path, mag-optical magnification.
The vibrating mirror assembly and the zone plate jointly form the illumination system of the mask defect detection device, light spots on the mask plate and light spots on the vibrating mirror assembly are in a pair of conjugate relations, and a plane where the reflecting mirror and the mask plate are located is opposite to the zone plate plane and is a pair of conjugate planes, so that the object-image relation is met. Under the condition that the focal length of the zone plate for a specific wavelength is fixed and the spot diameter at the vibrating mirror is unchanged, the spot diameter at the mask plate is in direct proportion to the image distance. Therefore, when the spot size of the galvanometer component is fixed, the spot size on the mask can be regulated and controlled according to the object-image relationship, and the size of the field of view on the mask can be flexibly regulated by designing the object-image relationship of the illumination system, so that the detection efficiency of the mask is improved.
Further, the vibrating mirror is a biaxial piezoelectric ceramic vibrating mirror or a Micro-electromechanical system (Micro-Electro Mechanical System, MEMS); the reflecting mirror is a multilayer film plane reflecting mirror or a multilayer film curved reflecting mirror. The reflectance of the mirror was greater than 60% at an incident angle of 48 ° for an euv wavelength of 13.5 nm.
Further, the zone plate is a fresnel zone plate, the fresnel zone plate is formed by alternately forming a plurality of transparent zones and opaque zones, and when point-to-point imaging is performed, the optical path difference between the light spots on a pair of conjugate planes to the adjacent transparent zones is the wavelength of an extreme ultraviolet beam. The Fresnel zone plate is condensed by utilizing the diffraction principle of light, when light waves emitted from object points are diffracted by each zone plate, the phase difference reaching an image point has multiple differences, so that constructive superposition can be generated, the light wave diffraction has a plurality of main maxima, the Fresnel zone plate naturally also has a plurality of focuses, compared with a lens, the Fresnel zone plate has the advantages of large area, portability, foldability and the like, the Fresnel zone plate is particularly suitable for telecommunication, optical ranging and aerospace technology, the focal length of the zone plate is shortened along with the increase of wavelength, the focal length and the chromatic aberration of the zone plate are opposite to those of a glass lens, achromatism is facilitated by matching the two, the Fresnel zone plate utilizes the diffraction rule to change wave fronts intentionally so as to cause diffraction fields required by people, and the Fresnel zone plate can also reduce speckle caused by strong coherence of light beam lines, so that the imaging quality is improved.
Further, the principal ray of the reflected beam scanned onto the zone plate by the galvanometer assembly is perpendicular to the plane of the zone plate, and the included angle between the plane of the zone plate and the plane of the mask plate is 8 degrees. The invention uses a zone plate as a light focusing element, and extreme ultraviolet light is focused on the mask plate plane through the zone plate, and the angle of the zone plate is fixed, so that the incident angle of a focused light beam relative to the mask plate plane is fixed, the reflection angle of the extreme ultraviolet light at a galvanometer assembly is not limited by extremely strict beam angles or beam positions, the adaptability of the mask defect detection device to light sources under various different extreme ultraviolet light parameters is improved, the setting angle or position of an intermediate optical element is not required to be frequently replaced for different light sources, the complexity of repeatedly adjusting and positioning for different light sources is avoided, and the use flexibility of the device is improved.
Further, the off-axis zone plate is a part of the Fresnel zone plate and consists of a mother Fresnel zone plate, a windowing and a pupil, wherein the pupil is positioned on one side of the mother Fresnel zone plate and is internally tangent with the outer edge of the mother Fresnel zone plate; the window is positioned at the other side of the mother Fresnel zone plate and is symmetrical to the pupil relative to the mother Fresnel zone plate in a central axis, and the reflected light beam of the mask passes through the center of the pupil. The function of windowing is to block 0 th order diffracted light from reaching the mask plate, so that the generated diffracted light increases imaging background interference, wherein the mother Fresnel zone plate can also be a Fresnel zone plate, the connecting angle between the pupil center and the spot center of the mask plate is also generally 8 degrees, namely, the reflected beam line of the mask plate passes through the pupil center, and the pupil receives the reflected light from the mask plate and images at an image plane.
Further, the detector is a CCD camera or an sCMOS camera sensitive to extreme ultraviolet light, the detector is placed at an image plane and used for receiving imaging light beams and imaging, the center of the mother Fresnel zone plate, the receiving center of the detector and the center of the image plane of the mask are arranged on the same straight line, and the straight line is perpendicular to the plane of the mask. The detector is placed on the image plane of the imaging system, the photosensitive plane of the detector is placed horizontally with the mask plate and is used for receiving photons and completing detection, imaging of the mask plate is completed, and imaging is used for judging and detecting defects of the mask plate.
Further, the fill pattern includes, but is not limited to, a round hole illumination pattern, an annular light transmissive illumination pattern, a dipole illumination pattern, and a quadrupole illumination pattern. It should be noted that, the galvanometer component can be scanned onto the zone plate through program control to form a plurality of different filling patterns, wherein the bipolar illumination patterns comprise a vertical bipolar photo pattern and a horizontal bipolar illumination pattern, the quadrupole illumination patterns comprise a symmetrical quadrupole illumination pattern and an asymmetrical quadrupole illumination pattern, and different filling modes have different imaging resolutions corresponding to different mask patterns.
The invention also provides a detection method using the mask defect detection device, which specifically comprises the following steps:
placing a mask plate to be detected on the mask driving assembly, and adjusting the placing positions of the galvanometer assembly, the zone plate, the off-axis zone plate and the detector in the vacuum cavity;
the extreme ultraviolet light is injected from an injection port and reaches the galvanometer assembly, and finally enters the detector to be received through reflection of the galvanometer assembly, focusing of the zone plate, reflection of the mask plate and imaging of the off-axis zone plate;
and the detector receives the light reflected by the mask plate collected by the off-axis zone plate, forms a pattern on the mask plate, and completes mask pattern imaging.
It should be noted that, the galvanometer assembly reflects and scans extreme ultraviolet light onto the zone plate, the zone plate focuses the reflected light beam onto the mask to be detected to form light spots, the reflected light beam is continuously radiated to the off-axis zone plate through the mask, the off-axis zone plate receives the reflected light from the mask and images at the image plane, the detector can receive the imaging light beam of the off-axis zone plate, the photosensitive plane of the detector is horizontally arranged with the mask and is used for receiving photons and completing detection, imaging of the mask is completed, and imaging is used for judging and detecting defects of the mask.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention adopts the illumination system formed by the vibrating mirror component and the zone plate, is compatible and suitable for extreme ultraviolet light with different light sources, ensures the luminous flux density on the mask, utilizes the characteristics that the vibrating mirror vibrates to change the direction and the position of light, controls the vibration in the horizontal and vertical directions by changing the voltage or the current of the vibrating mirror, and realizes accurate light path control, thus, the extreme ultraviolet light is reflected by the vibrating mirror component, scans the filled zone plate, changes different scanning modes by adjusting the vibration of the vibrating mirror, and the vibrating mirror component can scan the zone plate according to a certain scanning mode, thereby controlling the numerical aperture of the zone plate for the mask and realizing the free adjustment of the numerical aperture in a certain range; the zone plate can focus any type of incident light filling patterns on the mask plate, so that the effect of further improving the detection resolution of mask defects is achieved, and the size of a focusing light spot on the mask plate is not affected by different types of incident light filling patterns.
(2) The illumination system proposal of the invention can flexibly adjust the filling patterns of the vibrating mirror assembly to the zone plate according to different complex mask patterns, the filling of the zone plate with different illumination patterns can be suitable for the light sources under various extreme ultraviolet parameters, the invention is also suitable for different mask patterns, increases the imaging resolution of mask detection, avoids the excessive dependence of mask defect detection devices on a certain light source, and improves the use flexibility of the devices.
Drawings
FIG. 1 is a schematic diagram of a mask defect detecting apparatus according to the present invention; wherein the arrow direction represents the extreme ultraviolet trend;
FIG. 2 is a diagram showing the object-image relationship between the light spot on the galvanometer assembly and the light spot on the mask plate; wherein the arrow direction represents the extreme ultraviolet trend;
fig. 3 is a schematic diagram of a formable fill pattern of a galvanometer assembly of the present invention on a zone plate.
The graphic indicia are illustrated as follows:
1-shell, 11-entrance, 2-mask driving assembly, 3-galvanometer assembly, 31-reflector, 32-galvanometer, 4-zone plate, 411-round hole illumination pattern, 412-annular light transmission illumination pattern, 413-bipolar illumination pattern, 414-quadrupole illumination pattern, 5-off-axis zone plate, 6-detector, 8-vibration isolation platform, 100-mask.
Detailed Description
The invention is further described below in connection with the following detailed description. Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to be limiting of the present patent; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there is an azimuth or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc., based on the azimuth or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not indicated or implied that the apparatus or element referred to must have a specific azimuth, be constructed and operated in a specific azimuth, and thus terms describing the positional relationship in the drawings are merely illustrative and should not be construed as limitations of the present patent, and specific meanings of the terms described above may be understood by those skilled in the art according to specific circumstances.
Example 1
As shown in fig. 1, a mask defect detecting apparatus includes:
the device comprises a shell 1, wherein the shell 1 comprises a vacuum cavity, and an entrance port 11 which is formed in the shell 1 and is used for injecting extreme ultraviolet light into the vacuum cavity;
a mask driving assembly 2 disposed in the vacuum chamber and used for placing a mask 100 to be inspected;
an illumination system including a galvanometer assembly 3, the galvanometer assembly 3 including a mirror 31 for reflecting extreme ultraviolet light, and a galvanometer 32 coupled to the mirror 31 for changing a direction and a position of light of the reflected light beam; the illumination system further comprises a zone plate 4, wherein the zone plate 4 is positioned between the galvanometer assembly 3 and the mask driving assembly 2 and is used for focusing the reflected light beam to the mask plate 100 to be detected to form a light spot; the vibration mode of the vibrating mirror assembly 3 is regulated to control the reflected light beam to scan onto the zone plate 4 and form a certain filling pattern;
the off-axis zone plate 5 is arranged on a reflection light path of the mask 100 and is used for receiving the reflection light from the mask 100 and imaging at an image plane;
a detector 6, disposed at the image plane, for receiving the imaging beam of the off-axis zone plate 5.
The illumination system formed by the galvanometer assembly 3 and the zone plate 4 is compatible and applicable to extreme ultraviolet light with different light sources, ensures the luminous flux density of the extreme ultraviolet light on the mask 100, and has the following basic principle: by utilizing a Fourier synthesis technology, the vibration direction of the vibrating mirror is reasonably designed to change the scanning track on the zone plate, different filling patterns are formed, and the numerical aperture NA of the illumination side is controlled c (i.e., from the reticle to the zone plate side), and then coherent control of the illumination system may be performed:
wherein σ is the coherence factor of the system, NA c For illumination side numerical aperture (i.e. from reticle to zone plate side), NA o For the imaging side numerical aperture (i.e., from the mask to the off-axis zone plate side), the system is incoherent illumination when the coherence factor σ= infinity, and coherent illumination when σ = 0.
The characteristic that the vibration of the vibrating mirror 32 can change the direction and the position of light is utilized, the vibration in the horizontal direction and the vertical direction is controlled by changing the voltage or the current of the vibrating mirror, and the accurate light path control is realized, so that the extreme ultraviolet light is reflected by the vibrating mirror assembly 3, scans the filling zone plate 4, changes different scanning modes by adjusting the vibration of the vibrating mirror 32, and the vibrating mirror assembly 3 can scan the zone plate 4 according to a certain scanning mode, thereby controlling the numerical aperture of the zone plate 4 to the mask 100, and realizing the free adjustment of the numerical aperture in a certain range; the illumination system scheme of the embodiment can flexibly adjust the filling patterns of the vibrating mirror assembly 3 on the zone plate 4 according to different complex mask patterns, and the filling of the zone plate 4 with different illumination patterns can be suitable for the light sources under various extreme ultraviolet parameters, and also suitable for different mask plate 100 patterns, so that the process window of mask detection is improved, the imaging resolution of mask detection is enhanced, the excessive dependence of a mask defect detection device on a certain light source is avoided, and the flexibility of device use is improved.
In the present embodiment, the vacuum degree of the vacuum chamber of the housing 1 is less than 10 -7 torr。
In this embodiment, the mask driving assembly 2 has at least two-dimensional motion electromechanical system, which performs the operations of carrying, sampling, fixing, aligning, and changing the samples of the mask 100 in a vacuum environment, where the mask 100 is horizontally placed, and the operations of posture adjustment, alignment, and the like are performed by the driving device.
As shown in fig. 1, in the present embodiment, the mask defect detecting apparatus further includes a vibration isolation stage 8 for carrying the housing 1. The mask defect detection has very strict vibration requirements on the system, so that the whole device needs to be subjected to vibration isolation, the root mean square of vibration isolation of the vibration isolation platform 8 at 1Hz is not more than 3nm, and a stable exposure environment is provided for the mask defect detection.
As shown in fig. 2, the light spot on the plane of the reflecting mirror 31 on the galvanometer assembly 3 and the light spot on the sample plane on the mask plate 100 relative to the zone plate 4 are in a pair of conjugate relations, when the light spot size on the galvanometer assembly 3 is fixed, the light spot size on the mask plate 100 can be regulated and controlled according to the object-image relation, and the light spot on the galvanometer assembly 3 and the light spot on the mask plate 100 satisfy the following object-image relation:
wherein:
wherein D is a Spot diameter at galvanometer 32, D b Spot diameter at reticle 100, L 1 Object distance, L, from the plane of galvanometer 32 to the plane of zone plate 4 2 Image distance from the plane of zone plate 4 to the plane of reticle 100, focal length of f-path, mag-optical magnification.
It should be noted that, the galvanometer assembly 3 and the zone plate 4 together form an illumination system of the mask defect detection device of the embodiment, the light spot on the mask 100 and the light spot on the galvanometer assembly 3 are in a pair of conjugate relations, and the plane where the reflector 31 and the mask 100 are located is a pair of conjugate planes relative to the plane of the zone plate 4, so as to satisfy the object-image relation. In the case that the focal length of the zone plate 4 for a specific wavelength is fixed and the spot diameter at the galvanometer 32 is unchanged, the spot diameter at the mask 100 is in direct proportion to the image distance. Therefore, when the spot size of the galvanometer component 3 is fixed, the spot size on the mask 100 can be regulated and controlled according to the object-image relationship.
In this embodiment, the vibrating mirror 32 is a biaxial piezoelectric ceramic vibrating mirror; mirror 31 is a multilayer film planar mirror. The reflectance of the mirror 31 at an incident angle of 48 ° with respect to an extreme ultraviolet wavelength of 13.5nm is more than 60%.
In this embodiment, the zone plate 4 is a fresnel zone plate, where the fresnel zone plate is formed by alternately a plurality of transparent zones and opaque zones, and when point-to-point imaging is performed, the optical path difference between the light spots on a pair of conjugate planes with respect to the adjacent transparent zones is the wavelength of an extreme ultraviolet beam. The Fresnel zone plate is condensed by utilizing the diffraction principle of light, when light waves emitted from object points are diffracted by each zone plate, the phase difference reaching an image point has multiple differences, so that constructive superposition is generated, the light wave diffraction has multiple main maxima, the Fresnel zone plate naturally also has multiple focuses, compared with a lens, the Fresnel zone plate has the advantages of large area, portability, foldability and the like, the Fresnel zone plate is particularly suitable for telecommunication, optical ranging and aerospace technology, the focal length of the zone plate is shortened along with the increase of wavelength, the focal length and the chromatic aberration of the zone plate are opposite to those of a glass lens, achromatism is facilitated by matching the two, the Fresnel zone plate intentionally changes wave fronts by utilizing the diffraction rule, so that diffraction fields required by people are caused, and the Fresnel zone plate can also reduce speckle caused by strong coherence of a light beam line, so that the imaging quality is improved.
As shown in fig. 2, the principal ray of the reflected beam scanned onto the zone plate 4 by the galvanometer assembly 3 is perpendicular to the plane of the zone plate 4, and the angle between the plane of the zone plate 4 and the plane of the reticle 100 is 8 °. In general, the conventional mask defect detection device sets the incident angle of the light reflected to the plane of the mask 100 to be 8 °, so that the optical component used for reflection needs to be strictly placed at an angle or a position, so that the detection requirement of the incident angle of 8 ° can be met.
In this embodiment, the off-axis zone plate 5 is a part of a fresnel zone plate, and the off-axis zone plate is composed of a mother fresnel zone plate, a window and a pupil, and the pupil is located at one side of the mother fresnel zone plate and inscribes the outer edge of the mother fresnel zone plate; the fenestration is located on the other side of the mother fresnel zone plate and is axisymmetric to the pupil with respect to the mother fresnel zone plate, and the reflected beam of the reticle 100 passes through the center of the pupil. The function of windowing is to block the 0 th order reflected light from reaching the reticle 100, so that the generated reflected light increases the imaging background interference; in this embodiment, the mother fresnel zone plate is also a fresnel zone plate, and the included angle between the pupil center and the spot center of the mask 100 is also generally 8 °, that is, the reflected beam line of the mask 100 passes through the pupil center, and the pupil receives the reflected light from the mask 100 and images the image plane.
In this embodiment, the detector 6 is a CCD camera sensitive to extreme ultraviolet light, the detector 6 is disposed at an image plane and is used for receiving and imaging an imaging beam, and the center of the fresnel zone plate, the receiving center of the detector 6 and the center of the light spot of the reticle 100 are on a straight line, which is perpendicular to the plane of the reticle 100. The detector 6 is placed on an image plane of the imaging system, and a photosensitive plane of the detector 6 is placed horizontally with the mask 100 to receive photons and complete detection, complete imaging of the mask 100, and the imaging is used for judging and detecting defects of the mask 100.
Example 2
This embodiment is similar to embodiment 1, except that in this embodiment:
as shown in fig. 3, the fill patterns include a circular hole illumination pattern 411, an annular light transmission illumination pattern 412, a dipole illumination pattern 413, and a quadrupole illumination pattern 414.
It should be noted that, the galvanometer component 3 can be scanned onto the zone plate 4 through program control to form a plurality of different filling patterns, the light transmission effect of the round hole illumination pattern 411 is round hole light transmission, the light transmission effect of the annular light transmission illumination pattern 412 is annular light transmission, the light transmission effect of the bipolar illumination pattern 413 is provided with two round holes light transmission, the bipolar illumination pattern 413 can be a vertical bipolar photo pattern and a horizontal bipolar illumination pattern, namely, the arrangement positions of the two round holes light transmission are respectively in vertical or horizontal columns, the light transmission effect of the quadrupole illumination pattern 414 is provided with four round holes light transmission, and can be a symmetrical quadrupole illumination pattern and an asymmetrical quadrupole illumination pattern, namely, the light transmission sizes of the four round holes can be the same or different, and different filling modes have different imaging resolutions corresponding to different mask patterns.
Other structures and principles of this embodiment are the same as those of embodiment 1.
Example 3
A detection method using the mask defect detection device according to the above embodiment specifically includes the following steps:
placing a mask plate 100 to be detected on the mask driving assembly 2, and adjusting the placement positions of the galvanometer assembly 3, the zone plate 4, the off-axis zone plate 5 and the detector 6 in the vacuum cavity;
the extreme ultraviolet light is injected from an injection port 11 and reaches the galvanometer assembly 3, and finally enters the detector 6 to be received through reflection of the galvanometer assembly 3, focusing of the zone plate 4, reflection of the mask 100 and imaging of the off-axis zone plate 5;
the detector 6 receives the light reflected by the mask 100 collected by the off-axis zone plate 5, forms a pattern on the mask 100, and completes mask defect detection.
It should be noted that, the galvanometer assembly 3 reflects and scans the extreme ultraviolet light onto the zone plate 4, the zone plate 4 focuses the reflected light beam onto the mask plate 100 to be detected to form a light spot, the reflected light beam is continuously emitted to the off-axis zone plate 5 through the mask plate 100, the off-axis zone plate 5 receives the reflected light from the mask plate 100 and images the reflected light at the image plane, the detector 6 can receive the imaging light beam of the off-axis zone plate 5, the photosensitive plane of the detector 6 is horizontally arranged with the mask plate 100 and is used for receiving photons and completing detection, imaging of the mask plate 100 is completed, and imaging is used for judging and detecting defects of the mask plate 100.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (10)
1. A mask defect detecting apparatus, comprising:
the device comprises a shell (1), wherein the shell (1) comprises a vacuum cavity and an entrance port (11) which is arranged on the shell (1) and is used for injecting extreme ultraviolet light into the vacuum cavity;
the mask driving assembly (2) is arranged in the vacuum cavity and is used for placing a mask plate (100) to be detected;
illumination system comprising a galvanometer assembly (3), said galvanometer assembly (3) comprising a mirror (31) for reflecting extreme ultraviolet light, and a driving device (32) connected to said mirror (31) for changing the direction and position of the light of the reflected light beam; the illumination system further comprises a zone plate (4), wherein the zone plate (4) is positioned between the galvanometer assembly (3) and the mask driving assembly (2) and is used for focusing the reflected light beam to a mask plate (100) to be detected to form a light spot; the vibration mode of the vibrating mirror assembly (3) is regulated to control the reflected light beam to scan the zone plate (4) and form a certain filling pattern;
the off-axis zone plate (5) is arranged on a reflection light path of the mask plate (100) and is used for receiving reflection light from the mask plate (100) and imaging at an image plane;
and the detector (6) is arranged at the image plane and is used for receiving the imaging light beam of the off-axis zone plate (5).
2. A mask defect inspection apparatus according to claim 1, further comprising a vibration isolation platform (8) for carrying the housing (1).
3. The mask defect detection device according to claim 1 or 2, wherein a mirror plane on the galvanometer assembly (3) and a sample plane on the mask plate (100) are in a pair of conjugate relations with respect to the zone plate (4), a light spot size on the galvanometer assembly (3) is fixed, a light spot size on the mask plate (100) can be regulated and controlled according to an object-image relation, and the light spot on the galvanometer assembly (3) and the light spot on the mask plate (100) satisfy the following object-image relation:
wherein:
wherein D is a -spot diameter at galvanometer (32), D b -spot diameter at reticle (100), L 1 -object distance, L, from the plane of the galvanometer (32) to the plane of the zone plate (4) 2 -image distance of the zone plate (4) from the plane of the reticle (100), focal length of f-path, mag-optical magnification.
4. A mask defect detection device according to claim 1 or 2, wherein the galvanometer (32) is a biaxial piezoceramic galvanometer or a microelectromechanical system; the reflecting mirror (31) is a plane reflecting mirror or a curved reflecting mirror.
5. The mask defect detecting device according to claim 1 or 2, wherein the zone plate (4) is a fresnel zone plate, the fresnel zone plate is composed of a plurality of transparent zones and opaque zones alternately, and when the point-to-point imaging is performed, the optical path difference between the light spots on a pair of conjugate planes with respect to the adjacent transparent zones is the wavelength of an extreme ultraviolet beam.
6. A mask defect detecting device according to claim 1 or 2, wherein the principal ray of the beam scanned by the galvanometer assembly (3) onto the zone plate (4) is perpendicular to the plane of the zone plate (4), and the angle between the plane of the zone plate (4) and the plane of the mask plate (100) is 8 °.
7. The mask defect detection device according to claim 1 or 2, wherein the off-axis zone plate is composed of a mother fresnel zone plate, a windowing and a pupil, the pupil is located at one side of the mother fresnel zone plate and is inscribed with an outer edge of the mother fresnel zone plate; the windowing is positioned at the other side of the mother Fresnel zone plate, is symmetrical to the pupil relative to the mother Fresnel zone plate in a central axis, and a reflected light beam of the mask plate (100) passes through the center of the pupil.
8. A mask defect detection arrangement according to claim 7, characterized in that the detector (6) is a CCD camera or a sCMOS camera sensitive to extreme ultraviolet light, the detector (6) being placed at the image plane for receiving the imaging beam and imaging, the center of the parent fresnel zone plate, the receiving center of the detector (6) and the image plane center of the reticle (100) being in a straight line perpendicular to the reticle (100) plane.
9. A mask defect detection device according to claim 1 or 2, wherein the filling pattern comprises a circular hole illumination pattern (411), an annular light transmission illumination pattern (412), a dipole illumination pattern (413) and a quadrupole illumination pattern (414).
10. A detection method using the mask defect detection apparatus according to any one of claims 1 to 9, comprising the steps of:
placing a mask plate (100) to be detected on the mask driving assembly (2), and adjusting the placement positions of the galvanometer assembly (3), the zone plate (4), the off-axis zone plate (5) and the detector (6) in the vacuum cavity;
the extreme ultraviolet light is injected from an injection port (11) and reaches the galvanometer assembly (3), and finally enters the detector (6) to be received through reflection of the galvanometer assembly (3), focusing of the zone plate (4), reflection of the mask plate (100) and imaging of the off-axis zone plate (5);
the detector (6) receives light reflected by the mask plate (100) collected by the off-axis zone plate (5), forms a pattern on the mask plate (100), and completes mask pattern imaging.
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