CN115406894A - Illumination device, defect detection system, photoetching machine and defect detection method - Google Patents

Illumination device, defect detection system, photoetching machine and defect detection method Download PDF

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Publication number
CN115406894A
CN115406894A CN202110592434.5A CN202110592434A CN115406894A CN 115406894 A CN115406894 A CN 115406894A CN 202110592434 A CN202110592434 A CN 202110592434A CN 115406894 A CN115406894 A CN 115406894A
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light
illumination
defect detection
defect
unit
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杨晓青
韩雪山
张一志
申永强
顾杰
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Shanghai Micro Electronics Equipment Co Ltd
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Shanghai Micro Electronics Equipment Co Ltd
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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
    • G01N21/8806—Specially adapted optical and illumination features
    • 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
    • G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • 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
    • G01N21/94—Investigating contamination, e.g. dust
    • 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
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/7085—Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load
    • 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
    • G01N21/8806—Specially adapted optical and illumination features
    • G01N2021/8835—Adjustable illumination, e.g. software adjustable screen
    • 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
    • G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • G01N2021/8854—Grading and classifying of flaws
    • G01N2021/8861—Determining coordinates of flaws
    • 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
    • G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • G01N2021/8854—Grading and classifying of flaws
    • G01N2021/8874—Taking dimensions of defect into account
    • 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
    • G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • G01N2021/8887—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges based on image processing techniques

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  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)

Abstract

The invention provides an illumination device, a defect detection system, a lithography machine and a defect detection method. Wherein, the illumination unit is used for providing linear illumination. The light adjusting unit is used for adjusting the divergence angle of the illumination to a preset value. The light splitting unit is used for splitting the illumination after passing through the light adjusting unit into at least two beams of sub-illumination. The at least two sub-beams of light are distributed in a staggered mode, and light spots formed by mutually overlapping light intensity comprise light spots distributed in a flat-top Gaussian mode. Therefore, the light adjusting unit is used for increasing the divergence angle of the illumination to a preset value so as to realize telecentric illumination in a limited space and improve the defect detection accuracy. The light spots formed by the light splitting units ensure the uniformity of partial light intensity in a certain direction, and the influence on defect detection caused by nonuniform and unstable light intensity due to internal motion and external vibration is avoided, so that the high precision of a defect detection system is ensured, and the product yield is improved.

Description

Illumination device, defect detection system, photoetching machine and defect detection method
Technical Field
The invention relates to the technical field of integrated circuit manufacturing, in particular to an illuminating device, a defect detection system, a photoetching machine and a defect detection method.
Background
In the manufacturing process of semiconductor integrated circuits or flat panel displays, pollution control is a crucial link for improving the yield of products. Among them, the glass (glass) surface and the thin film (pellicle) surface of the reticle as the pattern template are susceptible to contamination, damage, and the like during clamping, transportation, storage, exposure, and the like, to generate defects such as foreign particles, fingerprints, scratches, pinholes, and the like. If defect detection is not performed before exposure, the existence of the defects directly affects the exposure performance and the product yield of the lithography machine in the exposure process. Therefore, defect detection is required before exposure of the reticle to determine whether the reticle can be directly used for exposure, so as to avoid the influence of the defects of the reticle on the exposure.
At present, a defect detection method for a mask is mainly realized by using a defect detection system composed of an illumination device and an imaging detection device, specifically, measurement light is projected onto the mask through the corresponding illumination device, the measurement light is scattered at a defect of the mask, generated scattered light enters the corresponding imaging detection device, and the imaging detection device detects signals of the scattered light and processes detection results to obtain information such as equivalent size of the defect of the mask. Wherein, for guaranteeing the defect detection precision, lighting device need provide far away illumination, and far away heart degree is higher, detects more accurately.
However, the detection accuracy of the defect detection system mainly composed of the illumination device and the imaging detection device at present cannot be further improved, and the main reasons include:
1. the defect detection system is generally integrated in a lithography machine, and is limited by the mechanical space inside the lithography machine, so that the existing defect detection system is required to be small enough to avoid occupying too much mechanical space inside the lithography machine, thereby causing the defect detection accuracy to be limited.
2. Because the upper surface and the lower surface of the mask are required to be subjected to defect detection, the mask needs to be placed on a reticle fork (mask carrying device) in the actual detection process. However, since the plate fork is easily affected by the internal motion mechanism and the external vibration of the lithography apparatus, and the light intensity distribution gradient of the measuring light provided by the illumination device is large, the repeatability of the defect detection result (such as the particle gray scale) of the defect detection system is poor, and the detection accuracy of the defect is seriously affected.
Therefore, a new illumination device, a defect detection system, a lithography machine and a defect detection method are needed to improve the defect detection accuracy.
Disclosure of Invention
The invention aims to provide an illuminating device, a defect detection system, a photoetching machine and a defect detection method, which aim to solve the problem of low defect detection precision.
In order to solve the above technical problem, the present invention provides an illumination device, including: the light path is provided with an illumination unit, a light adjusting unit and a light splitting unit which are arranged in sequence along the light path;
the illumination unit is used for providing linear illumination and transmitting the linear illumination to the light adjusting unit;
the light adjusting unit is used for adjusting the divergence angle of the illumination to a preset value, and the adjusted illumination is telecentric illumination;
the light splitting unit is used for splitting the illumination after passing through the light adjusting unit into at least two beams of sub-illumination; the at least two beams of sub-lights are distributed in a staggered mode, and the light spots formed by the mutual superposition of light intensities comprise light spots distributed in a flat-top Gaussian mode.
Optionally, in the lighting device, the at least two sub-beams of light are distributed in a staggered manner, and the light intensities of the light spots formed by overlapping the light intensities are uniform in the length direction, and part of the light intensities in the width direction are in flattop gaussian distribution; wherein the length direction and the width direction are perpendicular to each other.
Optionally, in the lighting apparatus, the light splitting unit includes a wedge-shaped substrate, and the illumination passes through the light adjusting unit and then penetrates through the wedge-shaped substrate to form the at least two beams of illumination.
Optionally, in the lighting device, the light splitting unit further includes a flat glass.
Optionally, in the lighting device, the flat glass and the wedge-shaped substrate are spliced; part of the illumination is transmitted through the flat glass, and part of the illumination is transmitted through the wedge-shaped substrate.
Optionally, in the lighting device, the flat glass and the wedge-shaped substrate are stacked on each other; and part of the illumination is transmitted through the flat glass, and part of the illumination is transmitted through the flat glass and the wedge-shaped substrate in sequence.
Optionally, in the lighting device, the preset value range of the divergence angle is as follows: greater than 20 degrees and less than 90 degrees.
Optionally, in the lighting device, the light adjusting unit includes a cylindrical micro lens array, a powell prism, and/or a diffusion sheet.
Optionally, in the lighting device, the lighting device further includes: a beam expander and a collimator group; wherein,
the beam expander is used for expanding the illumination, so that the diameter of the illumination is enlarged and the illumination can be parallelly transmitted to the light adjusting unit;
the collimating lens group is used for maintaining the collimation of the at least two beams of light which are output by the light splitting unit and distributed in a staggered mode.
Based on the same inventive concept, the invention also provides a defect detection system, which comprises the lighting device and the imaging detection device; wherein,
the lighting device is used for providing a light spot as measuring light and projecting the measuring light onto an object to be measured with a defect, and the measuring light is scattered at the defect to generate scattered light; wherein the light spots provided by the lighting device comprise light spots in a flat-top Gaussian distribution;
the imaging detection device is used for receiving and detecting the scattered light and processing the detected information to obtain the information of the defects.
Optionally, in the defect detection system, the information about the defect includes an equivalent size and a position coordinate of the defect.
Optionally, in the defect detection system, the defect detection system further includes a focal plane measuring device, a first moving stage and a second moving stage; wherein,
the focal plane measuring device is used for measuring the position of the object to be measured relative to the imaging detection device;
the first motion table is used for adjusting the distance of the object to be detected in a first direction relative to the imaging detection device;
the second motion platform is used for bearing the object to be measured and driving the object to be measured to move along a second direction so as to realize that the measuring light scans the whole surface of the object to be measured.
Optionally, in the defect detecting system, the first direction and the second direction are perpendicular to each other.
Optionally, in the defect detecting system, the imaging detection device includes an imaging detection mirror group and a detector; the imaging detection mirror group is used for converging the scattered light and transmitting the scattered light to the detector; the detector is used for detecting the scattered light and processing the detected information to obtain the defect information.
Based on the same inventive concept, the invention also provides a photoetching machine, which comprises the defect detection system.
Based on the same inventive concept, the invention also provides a defect detection method, which comprises the following steps:
the lighting device provides light spots for measuring light, wherein the light spots comprise light spots in a flat-top Gaussian distribution;
the measuring light is projected to an object to be detected, if the measuring light is projected to a defect position on the object to be detected, scattering occurs and scattered light is generated, and the scattered light is transmitted to the imaging detection device;
the imaging detection device detects the scattered light and obtains defect information.
Optionally, in the defect detection method, the information of the defect includes an equivalent size and a position coordinate of the defect
In summary, the present invention provides an illumination apparatus, a defect detection system, a lithography machine and a defect detection method. Wherein the lighting device comprises: the light path is arranged along the light path and comprises an illumination unit, a light adjusting unit and a light splitting unit which are arranged in sequence. The illumination unit is used for providing linear illumination and transmitting to the light adjusting unit. The light adjusting unit is used for adjusting the divergence angle of the illumination to a preset value, and the adjusted illumination is telecentric illumination. The light splitting unit is used for splitting the illumination after passing through the light adjusting unit into at least two beams of sub-illumination. The at least two sub-beams of light are distributed in a staggered mode, and light spots formed by mutually overlapping light intensity comprise light spots distributed in a flat-top Gaussian mode. Therefore, the divergence angle of the illumination is increased to the preset value through the light adjusting unit, so that telecentric illumination is realized in a limited space, and the defect detection accuracy is improved. And, the facula that produces after the adjustment behind the light adjustment unit is including being the facula that flat-topped gauss distributes to guarantee the even of some light intensity in certain direction, avoid inside motion and external vibration to lead to the inhomogeneous unstability of light intensity, in order to arouse the influence to defect detection, and then guaranteed defect detection system's high accuracy, be favorable to improving the product yield.
Drawings
FIG. 1 is a schematic diagram of a defect detection system according to an embodiment of the present invention;
FIG. 2 is a schematic view of a lighting device according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a plate yoke according to an embodiment of the present invention;
FIG. 4 is a schematic illustration of the vibration of the plate fork of an embodiment of the present invention;
FIG. 5 is a schematic diagram of a simulation of the repeatability and vibration frequency of an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a light splitting unit according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of an optical splitting unit according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of sub-illuminations projected onto the same image plane according to an embodiment of the present invention;
FIG. 9 is a schematic diagram illustrating the relationship between the light intensity and the position of a light spot of a flattened Gaussian beam according to an embodiment of the present invention;
FIG. 10 is a cross-sectional view of the light adjusting unit and the light splitting unit in combination according to the embodiment of the present invention;
FIG. 11 is an X-direction cross-sectional view of a light adjusting unit and a light splitting unit combined according to an embodiment of the present invention;
FIG. 12 is a diagram illustrating the relationship between the light intensity of the measuring light before defocusing and the position of the light spot according to the embodiment of the present invention;
fig. 13 is a schematic diagram illustrating a relationship between the light intensity of the measurement light after being out of focus and the position of the light spot according to the embodiment of the present invention.
Detailed Description
To further clarify the objects, advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is to be noted that the drawings are in greatly simplified form and are not to scale, but are merely intended to facilitate and clarify the explanation of the embodiments of the present invention. Further, the structures illustrated in the drawings are often part of actual structures. In particular, the drawings may have different emphasis points and may sometimes be scaled differently. It should be further understood that the terms "first," "second," "third," and the like in the description are used for distinguishing between various components, elements, steps, and the like, and are not intended to imply a logical or sequential relationship between various components, elements, steps, or the like, unless otherwise indicated or indicated.
In order to solve the above technical problem, the present embodiment provides a defect detection system, referring to fig. 1, the defect detection system includes the illumination device 10 and the imaging detection device 20. The lighting device 10 provides light spots with uniform light intensity in the length direction and part of the light intensity in the width direction in a flat-top gaussian distribution, so as to be used as measuring light, and the measuring light is projected onto the object M to be measured. Wherein the length direction and the width direction are perpendicular to each other. Further, in the defect detection system, the width direction is a scanning direction of detection. The measuring light is scattered through the defects on the object M to be measured and generates scattered light, the scattered light is transmitted to the imaging detection device 20, and defect information is obtained after the detection of the imaging detection device 20. If the measuring light is projected onto the surface of the object M to be measured and there is no defect, the measuring light is reflected by the object M to be measured and generates a reflected light, and the reflected light does not enter the imaging detection device 20. That is, when the surface of the object M has no defect, the imaging detection device 20 does not receive the light beam.
Further, the imaging detection device 20 includes an imaging detection mirror group 201 and a detector 202. The imaging detection mirror group 201 is used for converging the scattered light and transmitting the scattered light to the detector 202. The detector is a photoelectric detector and is used for detecting the scattered light and performing photoelectric conversion on the scattered light so as to obtain the defect information. The defect information includes an equivalent size and position coordinates of the defect.
In addition, the defect detection system further includes a focal plane measuring device 30, the first moving stage 40, and a second moving stage 50. Wherein the focal plane measuring device 30 is used for measuring the position of the object M relative to the imaging detection device 20. Typical measurement principles include, but are not limited to, multi-wavelength confocal measurements, triangulation, and the like. The first moving stage 40 is configured to adjust a distance between the object M and the imaging detection device 20 in a first direction, that is, adjust a vertical height (Y direction) of the object M according to the detection information of the focal plane measurement device 30, so as to ensure that the scattered light can enter the imaging detection device 20 and the reflected light does not enter the imaging detection device 20. The second motion stage 50 is configured to bear the object M and drive the object M to move along a second direction (X direction), so as to scan the entire surface of the object M with the measuring light. Wherein the first direction (Y-direction) and the second direction (X-direction) are perpendicular to each other.
Based on the same inventive concept, the embodiment also provides a lithography machine, which comprises the defect detection system.
The object M to be measured in this embodiment is a mask. Currently, the length and width of the commonly used mask is about 152mm, and the effective area is usually more than 132mm × 104mm, so that the linear light spot generated by the illumination device 10 needs to be at least more than 104mm, preferably more than 125mm. To ensure the defect detection accuracy, the measuring light generated by the illumination device 10 has the following characteristics: the deviation between the chief rays of the respective fields of view in the measuring beam is less than 5 degrees, preferably less than 1 degree. I.e. the illumination means 10 is required to provide telecentric illumination. The illumination field d of telecentric illumination, the focal length f of the collimating lens group and the divergence angle theta of the measuring light satisfy the following relation:
d＝f*sin(θ)*2；
however, since the mechanical space inside the lithography machine is very limited, the defect detection system is required to be compact, i.e. the focal length f of the collimator set is reduced as much as possible. Therefore, on the premise of ensuring telecentric illumination, the divergence angle θ of the measurement light needs to be increased to satisfy the above requirement.
Therefore, the lighting device 10 provided by the present embodiment can solve the above problem. Referring to fig. 2, the illumination apparatus 10 includes an illumination unit 101, a light adjusting unit 103, and a light splitting unit 104. The illumination unit 101 is configured to provide linear illumination and transmit the linear illumination to the light adjustment unit 103. Optionally, the illumination unit 101 includes a laser, and the laser provides a line light spot. The light adjusting unit 103 is configured to adjust a divergence angle of the illumination to a preset value. The light splitting unit 104 is configured to split the illumination light passing through the light adjusting unit 103 into at least two sub-illumination lights; the at least two sub-beams of light are distributed in a staggered mode, and light spots formed by mutually overlapping light intensity comprise light spots distributed in a flat-top Gaussian mode. Further, on the same image plane 106, the at least two sub-lights are distributed in a staggered manner and the light intensities are mutually superposed to form a light spot with uniform light intensity in the length direction and partial light intensity in the width direction in a flat-top gaussian distribution. The length direction and the width direction are perpendicular to each other, and the propagation directions of the at least two beams of light and the planes where the length direction and the width direction are located form a certain inclination angle. Furthermore, in the defect detection, the width direction is the scanning direction of the detection, so that the uniformity of light intensity in the scanning process is ensured, the influence of vibration on the detection is reduced, and the stability of subsequent detection is improved conveniently.
Further, the positions of the light adjusting unit 103 and the light splitting unit 104 may be interchanged, that is, the illumination may sequentially pass through the light adjusting unit 103 and the light splitting unit 104; alternatively, the light may sequentially pass through the light splitting unit 104 and the light adjusting unit 103.
The divergence angle of the illumination passing through the light adjusting unit 103 can be adjusted to be more than 20 degrees, so that the focal length of the collimator group 105 can be controlled to be less than 150mm, even less than 125mm. Therefore, the lighting device 10 provided by the embodiment can meet the requirement of reducing the space occupied by the defect detection system, and has better adaptability and expansibility.
Further, the light adjusting unit 103 includes, but is not limited to, a cylindrical micro lens array, a powell prism, and/or a diffusion sheet. The preset value range of the divergence angle is as follows: greater than 20 degrees and less than 90 degrees, preferably 40 degrees, 50 degrees, 60 degrees, or the like.
In addition, in actual inspection, since both the upper and lower surfaces of the reticle need to be inspected for defects, the reticle needs to be supported by a reticle fork N shown in fig. 3. The shape of the plate fork N is generally a square-shaped fork, so that the plate fork N is convenient to match with the shape of the mask. In order to bear the mask and meet the detection requirement, the thickness of the plate fork N is limited and cannot be thickened. Therefore, the mode of the plate fork N is low, and the plate fork is easily influenced by a motion mechanism inside equipment and external vibration, so that the vibration of the mask plate is caused, and the detection precision is influenced.
Referring to fig. 4, fig. 4 is a diagram illustrating an example of the plate fork N vibrating due to the influence of the internal motion mechanism and the externally induced vibration when the mask plate is detected in the defect detection system.
Although the scattered light is homogenized by means of detector integration in the imaging detection device 20 in the defect detection system. However, the influence of vibration on the detection is amplified because the incidence angle of the measuring light and the receiving angle of the imaging detection device 20 deviate from the normal direction of the mask due to vibration, and the problem cannot be solved well by the mode of detector integration. Referring to fig. 5, fig. 5 is a simulation diagram of the effect of different frequency vibrations on the sensitivity of the repeatability of the grain gradation measurement in the defect detection system. The particle gray level repeatability is used for representing the particle gray level detection repeatability, the smaller the particle gray level repeatability is, the better the particle size detection repeatability is, and the higher the detection accuracy is. During simulation, the amplitude corresponding to vibration of each frequency is 1 micron, the abscissa is the vibration frequency, and the ordinate is the influence on the gray level repeatability of the particles. Where the repeatability of 0.02 corresponds to a gray scale change of 2%. Therefore, as can be seen from fig. 5, the influence of the vibration of the plate fork N has a great influence on the reproducibility of the particle gradation detection.
In a simulation test, the vibration data actually measured in the simulation analysis chart 4 shows that the repeatability influence of the vibration of the plate fork N on the particle measurement gray scale reaches 16.7%, and therefore, the vibration of the plate fork N has a large influence on the repeatability of the particle measurement gray scale of the defect detection device. After analysis, the fundamental cause of the influence is that the light intensity distribution gradient of the measuring light is large, so that the corresponding residence time of the measuring light distributed on different positions is changed during vibration, and the repeatability difference of signals is finally generated. In other words, the velocity of the plate fork N in the horizontal direction X instantaneously changes due to the vertical vibration. Because the light intensity distribution of the measuring light is in large gradient distribution, the energy collected in the following two conditions can be greatly different: in the first case: the plate fork N is slowest when the relative light intensity is highest, and the plate fork N is fastest when the relative light intensity is lowest. In the second case: the plate fork N is fastest when the relative light intensity is highest, and is slowest when the relative light intensity is lowest. That is, the vibration of the plate fork N causes the instantaneous change of the speed of the plate fork N in the horizontal direction X, causing the fluctuation of scattered light, thereby affecting the repeatability of the particle measurement gray scale, resulting in the reduction of the defect detection accuracy.
In this regard, the illumination device 10 provided in this example obtains the light spot by the light splitting unit 104 to reduce the gradient of the light intensity distribution of the measurement light, so that the balance of the illumination intensity can be ensured, and the influence of the vibration on the detection precision can be reduced.
Specifically, referring to fig. 6, the light splitting unit 104 includes the plate glass 1041 and the wedge-shaped substrate 1042. The plate glass 1041 and the wedge-shaped substrate 1042 are spliced. Part of the illumination is transmitted through the plate glass 1041, and part of the illumination is transmitted through the wedge-shaped substrate 102. The splicing manner shown in fig. 6 is an up-down splicing manner, and besides the splicing manner shown in the figure, the splicing manner may be a left-right splicing manner, so that part of light passes through the flat glass 1041, and the rest of light passes through the wedge-shaped substrate 102.
In addition to the above arrangement, the plate glass 1041 and the wedge substrate 1042 may be stacked on each other. Referring to fig. 7, part of the light is transmitted through the plate glass 1041, and part of the light is transmitted through the plate glass 1041 and the wedge-shaped substrate 1042 in sequence. Since the illumination unit provides a typical gaussian beam, the light intensity is attenuated from the middle of the field of view to both sides. Therefore, at least two sub-illuminations, each of which is a gaussian beam, can be obtained by the action of the flat glass 1041 and the wedge-shaped substrate 1042. As shown in fig. 8, the sub-lights are illuminated on the same image plane 106, and are distributed in a staggered manner along the width direction in the light splitting unit 104, and the light intensities are mutually superimposed, and the light intensity peaks are mutually staggered, and by the superposition, the light spots shown in fig. 9, which have uniform light intensity in the length direction and part of the light intensity in the width direction is in a flat-top gaussian distribution, are obtained. And the light intensity gradient change is small, and the light intensity balance of the measuring light projected onto the mask can be ensured, so that the influence of vibration on detection is reduced.
The light splitting unit 104 may be a flat glass plate processed to have the structure shown in fig. 6 and 7. That is, the plate glass 1041 and the wedge-shaped substrate 1042 may be integrally formed.
In addition, the light splitting unit 104 may further include only the wedge substrate 1042. Referring to fig. 11 to 12, the cylindrical microlens array, the powell prism and/or the diffusion sheet in the light adjusting unit 103 are integrally formed with the wedge-shaped substrate 1042. After passing through the cylindrical micro lens array and/or the powell prism, the illumination passes through the wedge-shaped substrate 1042 to form at least two beams of sub-illumination, so as to form light spots which are shown in fig. 9 and have uniform light intensity in the length direction and have flat-top Gaussian distribution of partial light intensity in the width direction, thereby ensuring that the light intensity is stable and uniform in the scanning process, reducing the influence of vibration on detection and improving the detection accuracy.
Further, except that the light spot is acquired by arranging the light splitting unit 104. The spots can also be obtained in an out-of-focus manner. However, as can be seen from a comparison between fig. 12 and fig. 13, the light spot is obtained by arranging the light splitting unit 104 because the light spot is out of focus or the width of the light spot is too large.
After the optical segmentation unit 104 is arranged, simulation test is performed again on the actually measured vibration data in fig. 4, and it is found that the repeatability influence of the vibration of the plate fork N on the particle measurement gray scale is reduced to 6.6%, so that the optical segmentation unit 104 greatly alleviates the influence of the vibration of the plate fork N on the particle measurement gray scale repeatability of the defect detection device.
The degree of influence of the addition of the light segmentation unit 104 on telecentric illumination is only 0.1 degree, and almost no influence is caused on telecentric illumination. Moreover, the optical splitting unit 104 does not interfere with each other, and the formation of the light spot including the flat-top gaussian distribution is not affected, because the dominant wavelength of the semiconductor laser used in the actual product is 640 nm, and the bandwidth is 4 nm, the coherence length is 0.1 μm, and assuming that the added wedge-shaped substrate 1042 is N-BK7 with a thickness of 2 μm and a refractive index of 1.51, the optical path difference between the splitting part and the non-splitting part of the illumination is (1.51-1) × 2=1.02 μm, which is much greater than 0.1 μm, so that interference does not occur. Therefore, the illuminating device can not only ensure telecentric illumination, but also obtain relatively stable light spots as measuring light.
Further, with continued reference to fig. 2, the illumination apparatus further includes a beam expander 102 and a collimator set 105. Wherein, illumination warp behind beam expander 102, form parallel propagation and diameter and enlarge illumination, pass through in proper order again light adjustment unit 103 with behind the light segmentation unit 104, form two at least bundles sub-illumination, each sub-illumination warp behind the collimating mirror group 105 transmission, not only realize telecentric lighting, still form the facula.
Based on the same inventive concept, the present embodiment further provides a defect detection method, please refer to fig. 1, which includes:
the method comprises the following steps: the illumination device 10 provides a spot of light as measurement light; wherein the light spots comprise light spots in a flat-top Gaussian distribution.
Preferably, on the same image plane, the light intensity of the light spot is uniform in the length direction, and part of the light intensity in the width direction is in flat-top gaussian distribution, wherein the length direction and the width direction are perpendicular to each other, and the width direction is the scanning direction. That is, in the scanning direction, the light intensity of the light spot is almost flat-top gaussian distribution, so as to ensure that the light intensity is uniform and stable in the scanning process. Furthermore, under the action of the light adjusting unit 103, the light spot is telecentric illumination.
Step two: the measuring light is projected onto the object M to be measured, and if the measuring light is projected onto a defect of the object M to be measured, scattering occurs and scattered light is generated, and the scattered light is transmitted to the imaging detection device 20. If the measuring light is projected onto the surface of the object M to be measured and there is no defect, the measuring light is reflected by the object M to be measured and generates a reflected light, and the reflected light does not enter the imaging detection device 20. That is, when the surface of the object M is free from defects, the imaging detection device 20 does not receive a light beam.
Step three: the imaging detection device 20 detects the scattered light and obtains defect information. That is, the detector 202 obtains the equivalent size or position information of the defect through photoelectric conversion, so as to avoid the influence of the defect on the exposure effect, and further improve the yield of the product.
In summary, the illumination apparatus, the defect detection system, the lithography machine and the defect detection method provided in this embodiment are provided. The divergence angle of the illumination is increased to a preset value by the light adjusting unit 30, thereby implementing telecentric illumination in a limited space to improve defect detection accuracy. Moreover, the light splitting unit 40 forms light spots with uniform light intensity in the length direction and flat-top Gaussian distribution of partial light intensity in the width direction, so that the phenomenon that the light intensity is uneven and unstable due to internal movement and external vibration is avoided, the influence on defect detection is caused, the high precision of a defect detection system is further ensured, and the improvement of the product yield is facilitated.
It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the protection scope of the technical solution of the present invention, unless the content of the technical solution of the present invention is departed from.

Claims (17)

1. An illumination device, characterized in that the illumination device comprises: the light path is provided with an illumination unit, a light adjusting unit and a light splitting unit which are arranged in sequence along the light path;
the illumination unit is used for providing linear illumination and transmitting the linear illumination to the light adjusting unit;
the light adjusting unit is used for adjusting the divergence angle of the illumination to a preset value, and the adjusted illumination is telecentric illumination;
the light splitting unit is used for splitting the illumination after passing through the light adjusting unit into at least two beams of sub-illumination; the at least two sub-beams of light are distributed in a staggered mode, and light spots formed by mutually overlapping light intensity comprise light spots distributed in a flat-top Gaussian mode.
2. The illumination device according to claim 1, wherein on the same image plane, the at least two sub-illuminations are distributed in a staggered manner and the light intensities are superposed to form the light spot, which has a uniform light intensity in the length direction and a flat-top gaussian distribution of partial light intensities in the width direction; wherein the length direction and the width direction are perpendicular to each other.
3. The illumination device as recited in claim 1, wherein the light splitting unit comprises a wedge-shaped substrate through which the illumination passes after passing through the light conditioning unit to form the at least two sub-illuminations.
4. The illumination device of claim 3, wherein the light splitting unit further comprises a flat glass.
5. The illumination device of claim 4, wherein the flat glass and the wedge-shaped substrate are arranged in a tiled arrangement; part of the illumination is transmitted through the flat glass, and part of the illumination is transmitted through the wedge-shaped substrate.
6. The illumination device according to claim 4, wherein the flat glass and the wedge-shaped substrate are stacked on each other; and part of the illumination is transmitted through the flat glass, and part of the illumination is transmitted through the flat glass and the wedge-shaped substrate in sequence.
7. A lighting device as recited in claim 1, wherein said preset range of divergence angles is: greater than 20 degrees and less than 90 degrees.
8. A lighting device as recited in claim 1, wherein said light conditioning unit comprises a cylindrical microlens array, a powell prism and/or a diffuser.
9. A lighting device as recited in claim 1, further comprising: a beam expander and a collimator set; wherein,
the beam expander is used for expanding the illumination, so that the diameter of the illumination is enlarged and the illumination can be parallelly transmitted to the light adjusting unit;
the collimating lens group is used for maintaining the collimation of the at least two beams of light which are output by the light splitting unit and distributed in a staggered mode.
10. A defect detection system, characterized in that it comprises an illumination device and an imaging detection device according to any one of claims 1-9; wherein,
the lighting device is used for providing light spots as measuring light and projecting the measuring light onto an object to be measured with defects, and the measuring light is scattered at the defects and generates scattered light; wherein the light spots provided by the lighting device comprise light spots in a flat-top Gaussian distribution;
the imaging detection device is used for receiving and detecting the scattered light and processing the detected information to obtain the information of the defects.
11. The defect detection system of claim 10, wherein the information of the defect comprises an equivalent size and location coordinates of the defect.
12. The defect detection system of claim 10, further comprising a focal plane measuring device, a first motion stage, and a second motion stage; wherein,
the focal plane measuring device is used for measuring the position of the object to be measured relative to the imaging detection device;
the first motion table is used for adjusting the distance between the object to be detected and the imaging detection device in a first direction;
the second motion platform is used for bearing the object to be measured and driving the object to be measured to move along a second direction so as to realize that the measuring light scans the whole surface of the object to be measured.
13. The defect detection system of claim 12, wherein the first direction and the second direction are perpendicular to each other.
14. The defect detection system of claim 10, wherein the imaging detection device comprises a set of imaging detection mirrors and a detector; the imaging detection mirror group is used for converging the scattered light and transmitting the scattered light to the detector; the detector is used for detecting the scattered light and processing the detected information to obtain the defect information.
15. A lithography machine, characterized in that it comprises a defect detection system according to any one of claims 10 to 14.
16. A defect detection method using the defect detection system according to any one of claims 10 to 14, the defect detection method comprising:
the lighting device provides light spots for measuring light, wherein the light spots comprise light spots in a flat-top Gaussian distribution;
the measuring light is projected to an object to be detected, if the measuring light is projected to a defect position on the object to be detected, scattering occurs and scattered light is generated, and the scattered light is transmitted to the imaging detection device;
the imaging detection device detects the scattered light and obtains defect information.
17. The defect detection method of claim 16, wherein the information of the defect comprises an equivalent size and a position coordinate of the defect.
CN202110592434.5A 2021-05-28 2021-05-28 Illumination device, defect detection system, photoetching machine and defect detection method Pending CN115406894A (en)

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