Dynamic spatial filter and optical detection system

Abstract

The embodiment of the invention discloses a dynamic spatial filter, and the filter comprises a plurality of masks which have a preset shape and are used for achieving a specific spatial filtering function; the mask is connected to the motion output end of the X-axis motion mechanism; the X-axis movement mechanism is used for driving the mask to move on the X axis; the movement output end of the X-axis movement mechanism is borne by the movement output end of the Y-axis movement mechanism, and the Y-axis movement mechanism is used for driving the driving output end of the X-axis movement mechanism to move on the Y axis; the two-dimensional position of the mask is adjusted through the X-axis displacement and the Y-axis displacement; meanwhile, the embodiment of the invention discloses an optical detection system adopting the dynamic spatial filter. The shielding area of the spatial filter can be dynamically controlled in a two-dimensional mode, and flexible control over the pattern spatial information frequency spectrum of the to-be-detected object with the pattern is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of industrial detection, in particular to the field of semiconductor imaging detection. BACKGROUND

[0002] In the semiconductor industry, yield refers to the degree of functionality and reliability of integrated circuits manufactured on the wafer surface. During the manufacturing process, yield loss can be attributed to multiple links, including ion implantation, etching, deposition, planarization, cleaning, and photolithography process steps. The main mechanisms that lead to yield loss include: (1) gaseous molecular contamination introduced by the environment or equipment, as well as organic or inorganic particle contamination; (2) defects generated by previous processes, such as scratches, cracks, particle residues, and overlay deviations; (3) process fluctuations, such as deviations in doping concentration or film thickness from the expected values; (4) design deviations, i.e., mask pattern errors transmitted to the wafer pattern, resulting in critical dimension deviations. These mechanisms introduce microscopic defects during the manufacturing process, and the size and density of these defects directly affect the final chip yield. Therefore, it is necessary to detect and locate defects on the wafer after each process, in order to trace and optimize the process in a timely manner, thereby improving the yield.

[0003] The complexity of patterns on patterned wafers directly affects the difficulty of defect detection. The more complex the circuit pattern, the higher the defect detection rate and false positive rate. Logic devices, as a representative integrated circuit with high complexity patterns, are widely used, with smaller feature sizes, more metal layers, and significantly higher structural complexity than other types of semiconductor devices, thus becoming a major source of yield risk. Currently, the semiconductor industry generally believes that the defect detection capability of logic devices is a key indicator of the comprehensive performance of detection equipment.

[0004] Therefore, dark-field patterned wafer defect detection equipment is commonly used in the field of semiconductor imaging detection. To improve the defect detection rate of such detection equipment, the defect signal in the image needs to be as strong as possible compared to the background signal. Many methods have been proposed in the prior art to suppress the background signal. These methods can be divided into: (1) methods based on the optimization of light signal detection capability of the front-end optical system; (2) methods based on the optimization of defect recognition capability of the back-end image algorithm.

[0005] An effective solution in the category of the above method (1) is to use a spatial filter to suppress the contribution of the background signal to the image. The basic principle of this method is that, under certain lighting conditions, the scattered light of defects (such as foreign contaminant particles, pits, scratches) and the scattered light of the background (such as the periodic pattern of the logic circuit) differ in the frequency spectrum space. There is a certain amount of non-overlapping part between the partial spectral components of the defects and the spectral components of the background, which makes it possible to separate the two light signals in the frequency domain space. If the spectral components of the background signal are removed as much as possible by some method, while the spectral components of the defect signal are preserved as much as possible, then the background information in the time domain space (such as the image) corresponding to the frequency domain is also removed. This spectral separation or decoupling mechanism, often referred to as an optical spatial filtering mechanism, depends on a specially designed spatial filter for implementation.

[0006] Various optical spatial filtering methods in the prior art have the common feature of achieving spatial spectral gating of scattered light signals by placing a mask baffle on the pupil plane of the imaging lens group (or imaging system). There are various spatial filters in the prior art, and the pattern design of these spatial filters is specific to several or several categories of representative integrated circuit layout patterns. However, the limitation of this design method is that the pattern of the spatial filter is fixed and static, and due to the mechanical space limitation in the optical system, the number of spatial filters that can be accommodated is limited, ultimately resulting in the spatial filter being able to only exhibit good background pattern filtering effect for wafers of specific several circuit patterns. The fixed pattern spatial filter has very limited flexibility, making the defect detection equipment less versatile for different patterned wafer samples. In addition, for spatial filters using mechanical light baffles or reticles, there is also a diffraction effect at the edges of the filter. High-order diffracted light with a large diffraction angle can deviate from the imaging system, and these stray light can easily interfere with other optical devices or photosensitive elements of the dark-field patterned wafer detection system. The stop band of the existing spatial filter is difficult to flexibly adjust according to the characteristics of the circuit pattern on the wafer surface.

[0007] In order to solve the above problems, some patents use a transmissive spatial light modulator (such as a liquid crystal panel) as a spatial filter, and control the distribution of the light blocking area of the spatial filter through programming, with a spatial resolution up to the pixel level. Although this spatial light modulator has a certain flexibility, it inevitably leads to a decrease in the imaging quality of the imaging system, and a transmissive spatial light modulator cannot achieve complete light blocking. At the current technical level of transmissive spatial light modulators, the light wavelength is generally not less than 350 nm, while the wavelength of light used in many application equipment is 266 nm, which is not suitable for transmissive spatial light modulators. Compared with similar equipment using wavelengths greater than 350 nm, 266 nm has higher theoretical defect detection sensitivity.

[0008] There is also prior art that proposes to use a reflective spatial light modulator (such as a digital micromirror device), but the pixel effect of the digital micromirror device will cause additional derived light field to disturb the image, and the corresponding optical system of the reflective spatial light modulator is more complex, which significantly increases the difficulty and cost of assembly and adjustment. SUMMARY

[0009] The technical problem solved by the present application is to improve the flexibility of light blocking configuration of the spatial filter in the optical detection system and to achieve flexible control of the pattern spatial information spectrum of the object to be detected.

[0010] Accordingly, first, the present application provides a dynamic spatial filter, comprising:

[0011] A plurality of masks with predetermined shapes for realizing spatial filtering function;

[0012] An X-axis motion mechanism, the mask is coupled to the motion output end of the X-axis motion mechanism; the X-axis motion mechanism is used to drive the mask to displace in the X-axis;

[0013] A Y-axis motion mechanism, the motion output end of the X-axis motion mechanism is carried on the motion output end of the Y-axis motion mechanism, and the Y-axis motion mechanism is used to drive the driving output end of the X-axis motion mechanism to displace in the Y-axis;

[0014] The mask adjusts the two-dimensional position through X-axis displacement and Y-axis displacement.

[0015] Further, the mask is a circular mask.

[0016] Further, the circular mask has a smooth structure edge of light transmittance, which can be a sawtooth structure edge.

[0017] Meanwhile, the present application provides another defect optical detection system for an object to be detected with a pattern, comprising:

[0018] A light source for generating and sending a light beam for illuminating the object to be detected;

[0019] A beam expanding and shaping system for expanding and shaping the light beam from the light source so as to control the spot shape and size on the surface of the object to be detected;

[0020] An objective lens system for collecting the scattered light beam generated after the object to be detected is illuminated and focusing the scattered light beam to a back pupil;

[0021] A first lens for refocusing the divergent light rays from the back pupil of the objective lens system;

[0022] The dynamic spatial filter of the embodiment of the present application, the mask of the dynamic spatial filter is located at the back focal plane of the first lens, the back focal plane is conjugated with the back pupil plane of the objective lens system, and is used for filtering the light spot focused by the first lens;

[0023] The second lens is used for converting the light beam filtered by the dynamic spatial filter into a parallel light beam;

[0024] The tube lens system is used for imaging the parallel light beam output by the second lens to the detector;

[0025] The detector is used for detecting the defects in the object to be detected according to the image of the object to be detected; and the detector is used for imaging the light beam projected by the tube lens system.

[0026] Compared with the existing pattern preset and static spatial filter, the dynamic spatial filter according to the above embodiment is additionally provided with a motion mechanism capable of two-dimensional dynamic adjustment of the spatial filter, the shielding area of the spatial filter can be two-dimensionally and dynamically controlled, and the detection system can flexibly control the pattern spatial information spectrum of the object to be detected with a pattern; the dynamic spatial filter can flexibly configure the gating area of the spatial filter for a specific spatial spectrum by dynamically moving a single mask or multiple masks in the spatial filter according to the spatial distribution of the measured patterned wafer circuit features; the configured spatial filter can filter out the background signals related to the circuit pattern features to the maximum extent and ensure that the spatial spectrum related to the defects passes through the filter, so that the signal-to-noise ratio of the defect signals in the final image is maximized.

[0027] Meanwhile, the mask is used to completely block light, thereby ensuring the imaging quality of the detection system; compared with the existing scheme of using a digital micromirror device to realize a dynamic mask, the technical scheme of the present application does not cause the phenomenon of disturbed image caused by the diffraction light of the pixel effect of the digital micromirror device, and the difficulty of assembly and adjustment and the system cost are significantly reduced.

[0028] According to the dynamic spatial filter of the above embodiment, further, the mask has a sawtooth structure or other smooth structure edge of light transmittance, so that the negative contribution of the zero-order diffraction light and the high-order diffraction light to the imaging of the detection system can be avoided. Specifically, the sawtooth edge structure is equivalent to converting the step transmittance of the edge of the spatial filter into a gradual transmittance in a macroscopic view. The spatial filter with the gradual transmittance has a faster decay rate of the zero-order diffraction light in the spectral space, that is, the zero-order diffraction light is more sharp, and the diffraction direction angle of the high-order diffraction light is larger. The more sharp the zero-order diffraction light is, the faster the amplitude-frequency characteristic curve of the spatial filter decays, and the better the spatial filtering effect is. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 FIG. 1 is a local cross-sectional view of a dynamic spatial filter according to an embodiment of the present application;

[0030] Figure 2 A schematic view of an X-axis movement mechanism structure of a dynamic spatial filter according to an embodiment of the present application;

[0031] Figure 3 A schematic view of a circular mask structure with a sawtooth edge structure according to an embodiment of the present application;

[0032] Figure 4 A schematic view of a circular mask structure with a sawtooth edge structure according to an embodiment of the present application;

[0033] Figure 5 A partial structure sectional view of a light collection system embedded with a dynamic spatial filter according to an embodiment of the present application;

[0034] Figure 6 A partial structure sectional view of a light collection system embedded with a dynamic spatial filter according to an embodiment of the present application;

[0035] Figure 7 A schematic view of a defect optical detection system for a patterned object to be detected according to an embodiment of the present application;

[0036] Figure 8 A schematic view of a defect optical detection system for a patterned object to be detected according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] The application will be further described below in conjunction with the drawings. Like reference numerals in different embodiments designate like elements. In the following embodiments, many details are described in order to provide a more thorough description of the application. However, it will be apparent to persons having ordinary skill in the art that some features in different embodiments can be omitted, or replaced by other devices, materials, methods, etc. In some cases, some operations related to the application are not shown or described in the specification in order to avoid the core of the application being overwhelmed by too many details, and it is not necessary to describe these operations in detail for persons having ordinary skill in the art based on the description in the specification and general knowledge in the art.

[0038] In addition, features, operations or characteristics described in the specification can be combined in any appropriate manner to form various embodiments. Meanwhile, the steps or actions in the method description can also be adjusted or replaced in an order apparent to persons having ordinary skill in the art. Therefore, the order in the specification and the drawings is only for clear description of an embodiment, and does not mean a necessary order, unless otherwise stated that a certain order must be followed.

[0039] The serial numbers of components in this document, such as "first", "second", etc., are only used to distinguish the described objects, and do not have any sequential meaning. The "connection" and "coupling" in the present application include direct and indirect connections (couplings) unless otherwise specified.

[0040] The application fields and functional configurations of integrated circuit chips are different, such as high computing power chips used in mobile communication, Internet of Things, personal computers, data centers, and artificial intelligence. Different layout designs exist in the key logic circuit units of these chips, and the difference in design mainly manifests in the pitch and size of the logic units. In order to ensure the final yield of the chip, after each process is completed, a graphic wafer defect optical detection system is needed to measure the number, type, and distribution of defects, and the logic area of the circuit becomes the focus and difficulty of defect detection, which is specifically manifested in the relatively poor defect detection rate and false detection rate of the logic area.

[0041] In order to optimize the detection rate and false detection rate, the shape (pattern) of the spatial filter commonly used in the existing graphic wafer defect optical detection system is fixed; therefore, only the spectral components of the fixed area can pass through the spatial filter. In general cases, the spatial filter with the fixed shape (pattern) can filter out the spectral components related to the spatial information of the background pattern, realize the gating function of the defect signal, and thus optimize the detection rate and false detection rate of the defect. However, the spatial filter with the fixed shape (pattern) can only obtain the best filtering effect for a specific pattern to be detected object, but when the size, pitch, and process of the object to be detected change greatly, the spatial filter must be redesigned and the related hardware must be replaced in order to maintain the detection rate and false detection rate at a high level. The design and processing period of the spatial filter with the fixed shape (pattern) is unacceptable for the online defect detection demand of advanced logic circuits. In recent years, with the increase of the complexity of logic circuits, the above problems have become more prominent.

[0042] Therefore, the embodiment of the present application provides a dynamic spatial filter, which includes a plurality of masks for filtering, having a predetermined shape and size; at the same time, an X-axis motion mechanism is added, and the mask is coupled to the motion output end of the X-axis motion mechanism; the X-axis motion mechanism is used to drive the X-axis displacement of the mask; a Y-axis motion mechanism is added, and the motion output end of the X-axis motion mechanism is carried on the motion output end of the Y-axis motion mechanism, and the Y-axis motion mechanism is used to drive the motion output end of the X-axis motion mechanism to displace in the Y-axis; the mask adjusts the two-dimensional position through the X-axis displacement and the Y-axis displacement. This makes the dynamic spatial filter of the embodiment of the present application can control the shielding area of the spatial filter, and realize flexible and fine control of the spatial information spectrum of the pattern of the measured graphic wafer sample.

[0043] The dynamic spatial filter can dynamically move one or more masks in the spatial filter according to the spatial distribution of the spectrum of the circuit pattern features of the wafer under test, so as to flexibly configure the gating area of the spatial filter for a specific spatial spectrum. The dynamic spatial filter can filter out the background signal related to the circuit pattern features to the greatest extent, and ensure that the spatial spectrum related to the defect pattern passes through the filter, so that the signal-to-noise ratio of the defect signal in the final image is maximized. When the pattern of the wafer under test changes, the light blocking unit position of the spatial filter is reconfigured in a short time, so that the signal-to-noise ratio of the wafer under test is maximized. Therefore, the dynamic spatial filter has advantages that the existing fixed pattern spatial filter does not have. The mask achieves complete light blocking, which ensures the imaging quality of the imaging system. Compared with the existing scheme of using a digital micromirror device to realize a dynamic mask, the technical scheme of the present application does not cause the phenomenon of diffraction light disturbing the image due to the pixel effect of the digital micromirror device, and the difficulty of assembly and adjustment and the system cost are significantly reduced.

[0044] In an optional embodiment, the shape and size of the mask are adapted to the shape and size of the pattern arrangement position of the object to be detected. The periodically arranged structure units in the object to be detected generally form a plurality of periodically arranged diffraction spots at the light plane. As long as the plurality of masks can block the plurality of periodically arranged diffraction spots, the plurality of masks can be used.

[0045] When the plurality of masks are driven by the same movement mechanism, the distance between the two adjacent masks is fixed in advance, and the X and Y axis interval distance between the two adjacent masks depends on the interval distance between the periodically arranged structure units in the object to be detected. Each mask in the plurality of masks can also be driven by an independent X and Y axis movement mechanism. In this way, the X and / or Y axis distance between the two adjacent masks can be changed through the independent movement structure, so as to adapt to different types of objects to be detected, thereby improving the convenience of detecting different types of objects to be detected.

[0046] In an optional embodiment, the mask of the present embodiment is a circular mask. The number and size of the circular mask are determined according to the number and size of the periodic structure units (patterns) of the object to be detected.

[0047] In an optional embodiment, please refer to Figure 1 , Figure 2As shown, the Y-axis motion mechanism includes a Y-axis load mechanism, a first transmission component, and a first drive component. The first drive component drives the first transmission component, and the first transmission component drives the motion output end of the Y-axis load mechanism. Specifically, the first drive component can be a motor, and the first transmission component can be a lead screw. The Y-axis load mechanism includes a clamp 12 and a slide rail 13. The clamp 12 is fitted onto the slide rail 13 in a one-to-one correspondence. The motor drives the lead screw, and the lead screw drives the clamp 12 to move along the slide rail 13. The clamp 12 is both the motion output end of the Y-axis load mechanism and the motion output end of the entire Y-axis motion mechanism.

[0048] Please combine Figure 1 , Figure 2 As shown, the X-axis motion mechanism includes an X-axis load mechanism, a second transmission component, and a second drive component. The second drive component drives the second transmission component, which in turn drives the motion end of the X-axis load mechanism. Specifically, the second drive component 21 can be a rotary motor, the second transmission component includes a gear set 22 and a transmission shaft 23, and the X-axis load mechanism includes a wound rotor 24 and a pull wire 25. The wound rotors 24 are fixed or integrated onto the clamp 12 (not shown in the figure) in a one-to-one correspondence. Every two pull wires 25 are pulled parallel between a pair of wound rotors 24, and a circular mask 11 is bonded to the two parallel pull wires 25 using optical adhesive. The rotary motor drives the gear set, which adjusts the rotational speed and minimum rotational step, driving the transmission shaft to rotate. The transmission shaft drives the wound rotor to rotate. The pull wire 25 is both the motion output end of the X-axis load mechanism and the motion output end of the entire X-axis motion mechanism.

[0049] In optional embodiments, please refer to Figure 2 As shown, two parallel pull wires 25 are fitted into the grooves 240 of the two wound rotors 24. The spacing between the pull wires is equal to the groove spacing b of the wound rotors. The groove spacing b can be approximately equal to the radius of the circular mask to ensure the stability of the mask fixed on the pull fiber. In this example, the circular mask can be a thin metal sheet coated with a light-absorbing material, with a diameter not exceeding 2 mm. In the one-to-one pair of wound rotors, one end of one of the wound rotors 24 is connected to a drive shaft 23. The rotation of the drive shaft 23 drives the wound rotor 24 to rotate.

[0050] The diameter d of the pull wire 25 does not exceed one-tenth of the diameter of the circular mask to ensure that its presence does not generate optical noise. Optionally, the pull wire can be made of optical fiber. The optical fiber material is transparent and has a diameter of only tens of micrometers. It will not cause optical noise inside the lens barrel of the light collection system, which can ensure the filtering performance of the system and the tensile strength is also suitable.

[0051] The length of the transmission shaft is adjusted according to the actual mechanical design, and the length of the pull wire needs to exceed the effective aperture of the pupil plane in the specific application scene. The specific angle of the rotary motor is controlled by the upper controller to drive the circular mask to move to the specified position on the second axis. The stroke control of the rotary motor is within the range that the circular mask does not reach the winding rotor, so as to ensure that the mask is not damaged by the winding rotor.

[0052] In an optional embodiment, the number of circular masks is 6.

[0053] The diameter of the circular mask can be adjusted according to the required spatial resolution of the stop band. Within the range of mechanical strength that can be tolerated, the smaller the diameter of the circular mask, the smaller the area that can block the pupil plane spectrum space of the optical system, the smaller the corresponding spatial spectrum range, and the finer the spectral spatial difference that can be distinguished by the circular mask. And because the blocking area forms a band-stop filtering effect, the smaller the diameter of the circular mask, the higher the spatial resolution of the stop band.

[0054] In an optional embodiment, please refer to Figure 3 As shown in the figure, the circular mask can also be processed to have a sawtooth structure edge. The sawtooth structure edge is a kind of smooth structure edge with light transmittance, which can avoid the negative contribution of zero-order diffracted light and high-order diffracted light to imaging. Specifically, the sawtooth edge structure is equivalent to converting the step transmittance of the spatial filter edge into a gradual transmittance in a macroscopic sense. The spatial filter with gradual transmittance has a faster decay rate of zero-order diffracted light in the frequency spectrum space, that is, the zero-order diffracted light is more sharp, and the diffraction direction angle of the high-order diffracted light is larger. The more sharp the zero-order diffracted light, the faster the amplitude-frequency characteristic curve of the spatial filter decays, and the better the spatial filtering effect.

[0055] The circular mask 11 with a sawtooth structure edge can be a thin metal plate with a thickness of not more than 1 mm and a diameter of not more than 4 mm. The circular mask with a sawtooth structure can also be a thin layer of transparent dielectric plate coated with an opaque metal film, with a thickness of not more than 1 mm and a diameter of not more than 4 mm. When applied to a light collection system, the periodical arc length L of the sawtooth structure is determined by the illumination light wavelength λ, the illumination light line width w L , and the equivalent focal length f of the front lens group. As shown in the figure, Figure 4 In this example, the periodical arc length L is not more than 1 mm. Limited by the precision machining process level, the width a is not more than 2 mm.

[0056] Meanwhile, the application provides a light collection system with a built-in dynamic spatial filter, which comprises a front lens group, a rear lens group and a lens barrel, and the mask, the Y-axis load mechanism and the X-axis load mechanism are built into the lens barrel, and the mask can be adjusted in the effective aperture of the pupil plane. This makes the light collection system of the application capable of controlling the blocking area of the mask and achieving flexible and fine control of the spatial information spectrum of the patterned wafer sample.

[0057] The light collection system of the application can dynamically move a single or multiple masks according to the spatial distribution of the spectrum of the measured patterned wafer circuit pattern features, so as to flexibly configure the gating area of the spatial filter for specific spatial spectrum. The configured spatial filter can filter out the background signal related to the circuit pattern features to the greatest extent, and ensure that the spatial spectrum related to the defect pattern passes through the filter, so that the signal-to-noise ratio of the defect signal in the final image is maximized. When the pattern of the measured wafer sample changes, the position of the mask can be reconfigured in a short time, so as to maximize the signal-to-noise ratio of the measured wafer sample.

[0058] In an optional embodiment, the application provides a light collection system, as shown in Figure 5 、 Figure 6 The light collection system comprises a lens barrel 51, a front lens group 52, a rear lens group 53 and a mask 11. The front lens group 52, the rear lens group 53 and the mask 11 are all installed in the lens barrel 51. The front lens group 52 and the rear lens group 53 each comprise a plurality of lenses, which can be directly used as the lens group of the objective lens in the prior art. The mask 11 is located on the pupil plane, and the rear lens group 53 is arranged behind the mask 11. The light collection system with the built-in spatial filter is still an infinite conjugate objective lens. The mask 11 is installed in the lens barrel 51 and located in the effective aperture 510 of the pupil plane of the light collection system, so as to realize the spatial filtering function, block the diffraction spots generated by the periodic structure unit of the detected object and / or the scattering spots generated by the rough surface, remove the background information in the image time domain space corresponding to the frequency domain, and at the same time, retain the spectral components of the defect signal as much as possible.

[0059] The high-order diffraction light generated by the mask 11 is enclosed in the lens barrel space, so that the diffraction light does not interfere with the external space of the light collection system.

[0060] In an optional embodiment, the application provides a light collection system, in which the periodic arc length L of the sawtooth structure can be implemented by referring to the following determination method of the periodic pitch p.

[0061] The diffraction spot at the plane of the pupil plane can be described by the following formula:

[0062]

[0063] where d x = spot length of the light spot along the spatial filter (length of the spatial filter arranged in the x direction) at the plane of the pupil plane, λ = wavelength, f = focal length of the front lens group, and w L = illumination line width at the target plane. The length of the illumination line is arranged in the y direction.

[0064] The sawtooth pitch p of the spatial filter with sawtooth can be determined from the following formula:

[0065]

[0066] where p = sawtooth pitch. The periodic sawtooth pitch can be chosen such that the first order diffraction is outside the illuminated line of the detector. In this way, the spatial filter with sawtooth structure edge in a periodic manner can be configured to have a small enough to diffract all diffraction light except zero order diffraction light out of the detector segment.

[0067]

[0068] In other words, formulas (2) and (3) are equivalent. Any type of periodic sawtooth with a sawtooth pitch that satisfies formulas (2) and (3) can be used to improve the performance of the spatial filter.

[0069] In an optional embodiment, a defect optical detection system for a graphic object to be detected according to the present application is suitable for dark field detection, please refer to Figure 7 The system basically includes:

[0070] A light source 71 is arranged to send a light beam of a preset wavelength band to the object to be detected at a preset angle. The light source can be a red laser, a blue laser, an ultraviolet light collector, an LED light source, etc. The type of the light source is not limited in the embodiments of the present application.

[0071] The beam expansion and shaping system 72 includes a beam expansion module and a shaping module, which are used to expand and shape the light beam from the light source 71 to control the spot shape and size of the pattern wafer 70 surface of the object to be detected, and can form an illumination line. The beam expansion module is used to realize the amplification of the spot diameter to meet the use requirements of the subsequent shaping module. The shaping module is used for beam shaping processing. The shaping module can be a collimating flat-top shaping element, or a free-form surface shaping element which can provide a single degree of freedom line width compression in the narrow edge direction; the shaping module can be realized in the form of a diffractive optical element (DOE), a microlens array, a prism, etc.; the shaping module can also include a one-dimensional beam expansion element, a collimating flat-top shaping element, a free-form surface shaper, etc.; or any other suitable device known in the art for shaping a light beam.

[0072] The light collection system 73 includes a dynamic spatial filter of the embodiment of the present application, wherein the mask is arranged on the pupil plane, used to receive the scattered light beam of the object to be detected, focus the scattered light beam to the focal plane and filter to form a parallel light beam.

[0073] The tube lens system 74 is located on the image side (rear side) of the light collection system, used to image the parallel light beam projected by the light collection system to the detector, and finally realize imaging of the object to be detected to the detector.

[0074] The detector 75 is located on the image side (rear side) of the tube lens system, and according to different application requirements, the detector is used to image the light beam projected by the tube lens system 74, so as to detect the defects in the object to be detected.

[0075] The detector can be a photodiode, a photodetector or an avalanche photodetector, etc., and the type of the detector is not limited in the embodiment of the present application.

[0076] The optical trap 76 is used to eliminate the reflected light formed after the illumination spot acts on the pattern wafer 70 of the object to be detected.

[0077] Since the light collection system 73 is similar to an infinite conjugate objective lens, the infinite conjugate optical design can be realized with the tube lens system 74.

[0078] The optical detection system of the embodiment effectively avoids the interference of stray light generated by the spatial filter on the entire detection system, is beneficial to optimizing the aberration correction of the system, improves the imaging quality, further improves the detection precision of the system, and guarantees the detection quality of the system. Moreover, since the spatial filter is directly integrated in the light collection system, the overall structure of the detection system is more compact, and the stability is enhanced.

[0079] In an optional embodiment, another optical system for detecting defects of a patterned object is provided, as shown in FIG. 1, which basically comprises: Figure 8

[0080] A light source 81 is configured to generate an illumination beam to illuminate the patterned wafer. The light source can be a red laser, a blue laser, an ultraviolet light collector, an LED light source, or the like. The type of the light source is not limited in the embodiments of the present application.

[0081] A beam expanding and shaping system 82 is configured to convert the light beam emitted by the light source into a uniform distribution of illumination spots after the light beam passes through the beam expanding and shaping system. The illumination spots interact with the patterned wafer to form reflected light and scattered light. The beam expanding module is configured to expand the diameter of the light spot to meet the use requirements of the subsequent shaping module. The shaping module is configured to perform beam shaping processing. The shaping module can be a collimating flat-top shaping element, a free-form surface shaping element, a diffractive optical element (DOE), a microlens array, a prism, or the like. The shaping module can also include a one-dimensional beam expanding element, a collimating flat-top shaping element, a free-form surface shaper, or the like. Alternatively, any other device known in the art that is suitable for shaping the light beam can be used.

[0082] An objective lens system 83 is configured to receive the scattered light beam formed after the illumination spots interact with the patterned wafer and focus the scattered light beam to a back focal plane.

[0083] A first lens 84 is configured to focus the scattered light spot emitted from the back pupil plane of the objective lens system 83 to a plane where the mask 11 of the dynamic spatial filter 1 is located.

[0084] The dynamic spatial filter 1 according to the embodiments of the present application receives the light spot focused by the first lens 84 and performs spatial filtering on the pupil plane focused by the first lens 84 by using the mask 11.

[0085] A second lens 85 is configured to receive the light spot filtered by the dynamic spatial filter 1 and convert the light spot into a parallel light beam.

[0086] A tube lens system 86 is configured to image the parallel light beam output by the second lens 85 to a detector.

[0087] The detector 87 is configured to image the light beam projected by the tube lens system 86. The detector is configured to image the light beam projected by the tube lens system 86 to detect defects in the patterned object. The detector can be a photodiode, a photodetector, an avalanche photodetector, or the like. The type of the detector is not limited in the embodiments of the present application.

[0088] ​A light trap 88 is used to eliminate the reflected light formed after the illumination light spot and the object to be detected interact with the pattern wafer 80.

[0089] The above application of specific examples to illustrate the invention, is only used to help understand the invention, and not to limit the invention. For the skilled in the art to which the invention belongs, according to the idea of the invention, can make a number of simple deduction, deformation or replacement. For example, the Y axis displacement and X axis displacement vector superposition form, the specific structure of X axis movement mechanism and Y axis movement mechanism, for the skilled in the art of the invention, can also be deformed or replaced according to the specific circumstances, still can realize the purpose of the invention.

Claims

1. A dynamic spatial filter characterized by, The application relates to a mask device for optical detection, comprising: a plurality of masks with a predetermined shape for realizing a spatial filtering function; an X-axis movement mechanism, the masks being coupled to a movement output end of the X-axis movement mechanism, the X-axis movement mechanism being used for driving the masks to displace in an X-axis direction; a Y-axis movement mechanism, the movement output end of the X-axis movement mechanism being carried on a movement output end of the Y-axis movement mechanism, the Y-axis movement mechanism being used for driving the driving output end of the X-axis movement mechanism to displace in a Y-axis direction; the masks being adjusted in two-dimensional positions through the X-axis displacement and the Y-axis displacement.

2. The dynamic spatial filter of claim 1, wherein: The X-axis movement mechanism comprises an X-axis load mechanism, and the masks are fixed to a movement output end of the X-axis load mechanism.

3. The dynamic spatial filter of claim 2, wherein: The Y-axis movement mechanism comprises a Y-axis load mechanism, and the X-axis load mechanism is carried on the Y-axis load mechanism.

4. The dynamic spatial filter of claim 3, wherein: The Y-axis load mechanism comprises slide rails and clamps, the slide rails are arranged in pairs in parallel, the clamps are arranged in pairs in correspondence and are slidably installed on the slide rails, and a Y-axis driving mechanism drives the clamps to slide along the slide rails.

5. The dynamic spatial filter of claim 4, wherein: The X-axis load mechanism comprises wire winding rotors and pull wires, the wire winding rotors are fixed or integrated on the clamps, and the masks are fixed on the pull wires; the pull wires are pulled between the wire winding rotors arranged in correspondence.

6. The dynamic spatial filter of claim 4, wherein: The Y-axis movement mechanism further comprises a first transmission member and a first driving member, the first driving member drives the first transmission member, and the first transmission member drives the clamps.

7. The dynamic spatial filter of claim 5, wherein: The X-axis movement mechanism further comprises a second transmission member and a second driving member, the second driving member drives the second transmission member, and the second transmission member drives the wire winding rotors.

8. The dynamic spatial filter of claim 7, wherein: The second transmission member comprises a gear set and a transmission shaft, the second driving member comprises a rotary motor, the rotary motor drives the gear set, the gear set drives the transmission shaft, and the transmission shaft drives the wire winding rotors.

9. The dynamic spatial filter of claim 8, wherein: The wire winding rotors are provided with two grooves in parallel, the two pull wires are sleeved in the grooves of the wire winding rotors arranged in correspondence in pairs, and the two pull wires are arranged in parallel; and the masks are fixed on the two pull wires.

10. The dynamic spatial filter of claim 9, wherein: The masks are circular masks as a whole; the interval between the two grooves is approximately equal to the radius of the circular masks, so as to ensure the stability of the circular masks fixed on the two pull wires.

11. The dynamic spatial filter of claim 9, wherein: In the pair of wire winding rotors, one end of one of the wire winding rotors is coupled to the transmission shaft, and the transmission shaft drives the wire winding rotor to rotate.

12. The dynamic spatial filter according to any of claims 1-9, 11, characterized by: The masks are circular masks as a whole.

13. The dynamic spatial filter of claim 12, wherein: The circular masks are metal foils coated with light-absorbing materials, and the diameters of the circular masks are less than or equal to 2 mm.

14. The dynamic spatial filter of claim 12, wherein: The circular masks have smooth structure edges of light transmittance.

15. The dynamic spatial filter of claim 14, wherein: The smooth structure edges of light transmittance are sawtooth structure edges.

16. An optical detection system, comprising in sequence: a light source for generating and sending a light beam for illuminating a to-be-detected object; a beam expanding and shaping system for expanding and shaping the light beam from the light source so as to control the spot shape and size of the surface of the to-be-detected object; an objective system for collecting a scattered light beam generated after the to-be-detected object is illuminated and focusing the scattered light beam to a back focal plane; a first lens for refocusing divergent light rays from the back pupil plane of the objective system; the dynamic spatial filter according to any one of claims 1-15, wherein the mask is located at a back focal plane of the first lens, the back focal plane being conjugate to the back pupil plane of the objective system, for filtering the light spot focused by the first lens; a second lens for converting the light beam filtered by the dynamic spatial filter into a parallel light beam; a tube lens system for imaging the parallel light beam output by the second lens to a detector; a detector for detecting defects in the object to be detected according to the image of the object to be detected; the detector is used for imaging the light beam projected by the tube lens system.

17. The optical detection system of claim 16, wherein, Further comprising a light trap for eliminating reflected light formed after the object to be detected is illuminated.

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