Automatic focusing system and focusing method for pattern wafer defect detection

Abstract

The invention belongs to the technical field of optical design, and particularly relates to an automatic focusing system and focusing method for pattern wafer defect detection, and the automatic focusing system comprises an incident light modulation assembly which modulates incident light into a projection pattern so as to form an image on a wafer; the light is reflected to the return light collection assembly on the wafer, and the return light collection assembly obtains the current defocusing amount; the focus position bias lens group moves until the current defocusing amount reaches the set defocusing amount; the focusing light source and the illumination light source can share one set of objective lens, automatic focusing can be carried out in the coaxial direction of the shallow-focus deep objective lens, meanwhile, additional optical path difference is avoided, whether the wafer is located at the focusing position or not can be judged by comparing the current defocusing amount with the set defocusing amount, focal length adjustment is achieved in cooperation with the focus position offset lens set, and the focusing precision is improved. And meanwhile, the wave band is inconsistent with the wave band of the illumination light source, so that the illumination light source and the focusing light source can be effectively distinguished, different objective lenses are adapted, and the repeatability of light path design is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical design, and in particular relates to an automatic focusing device for a laser beam, and more particularly to an automatic focusing system and a focusing method for pattern wafer defect detection. Background Art

[0002] In the field of semiconductor manufacturing, wafer size is getting smaller and smaller, and the corresponding defect size on the wafer is also getting smaller and smaller. The types of defects include particles, graphic defects, scratches on the wafer surface, etc. Graphic wafer defect detection equipment needs to perform fast and accurate inspections on wafers to ensure the yield and production rate in chip production.

[0003] The detection light source used in existing detection equipment has reached the DUV (deep ultraviolet) level, and the NA (numerical aperture) value of the corresponding objective lens is also getting larger and larger. These two factors will also make the focal depth of the objective lens shallower while improving the resolution of the objective lens. It needs to be focused coaxially with the illumination objective lens to meet the requirements of high precision and detection point overlap. At the same time, the coaxial focusing part and the illumination part will result in poor focused image quality, and the stray light brought by the focused light source will affect the detection sensitivity.

[0004] Therefore, it is urgent to develop a new automatic focusing system and focusing method for graphic wafer defect detection to solve the technical problems of how to adjust the focal length to make the focusing light source and the illumination light source coaxial and overcome the poor image quality after coaxiality and the influence of stray light on detection sensitivity.

[0005] It should be noted that the above information disclosed in this background technology section is only used to understand the background technology of the present application concept, and therefore, the above description is not considered to constitute information of the prior art. Summary of the Invention

[0006] The embodiments of the present disclosure at least provide an automatic focusing system and focusing method for pattern wafer defect detection.

[0007] In a first aspect, an embodiment of the present disclosure provides an automatic focusing system for detecting defects in graphic wafers, which includes: an incident light modulation component, a return light collection component, a first beam splitter prism, a focus position bias mirror group, a dichroic mirror and an objective lens; wherein the incident light modulation component, the return light collection component and the focus position bias mirror group are arranged around the first beam splitter prism, and the focus position bias mirror group, the dichroic mirror and the objective lens are arranged in sequence; the incident light modulation component modulates the incident light into a projection pattern, and the projection pattern passes through the first beam splitter prism, the focus position bias mirror group, the dichroic mirror and the objective lens in sequence to form an image on the wafer; the projection pattern is reflected on the wafer and passes through the objective lens, the dichroic mirror, the focus position bias mirror group and the first beam splitter prism to the return light collection component, so that the return light collection component obtains the current defocus amount; and the focus position bias mirror group moves between the first beam splitter prism and the dichroic mirror according to the current defocus amount until the current defocus amount reaches the set defocus amount.

[0008] In an optional embodiment, the incident light modulation component includes: a focusing light source and a projection mask; the focusing light source, the projection mask, and the first dichroic prism are arranged in sequence; the focusing light source emits incident light toward the projection mask so that the projection mask modulates the incident light into a projection pattern.

[0009] In an optional embodiment, the return light collecting component includes: a second beam splitter prism, a receiving mask, a first detector, a second detector and a controller; the second beam splitter prism is located on one side of the first beam splitter prism, the receiving mask is located between the first detector and the first beam splitter prism, and the second detector is located on one side of the second beam splitter prism; the first detector and the second detector are electrically connected to the controller; the projection pattern is respectively emitted to the receiving mask and the second detector through the first beam splitter prism and the second beam splitter prism; the projection pattern forms a corresponding current return image through the receiving mask, so that the first detector collects the light intensity value of the current return image; the second detector collects the light intensity value of the projection pattern; the controller is configured to obtain the current defocus amount based on the light intensity value of the current return image and the light intensity value of the projection pattern.

[0010] In an optional embodiment, the receiving mask is located at a conjugate position of the projection mask.

[0011] In an optional embodiment, the receiving mask and the projection mask are both arranged in a stripe shape.

[0012] In an optional embodiment, the focus position biasing lens group includes: a first glued mirror, a first single lens, a second single lens and a moving unit; the first glued mirror, the first single lens, and the second single lens are arranged in sequence and are all movably connected to the moving unit, and the moving unit is electrically connected to the controller; the controller is also configured to drive the moving unit to drive the first glued mirror, the first single lens, and the second single lens to move synchronously.

[0013] In an optional embodiment, the moving unit includes: a driving member and a screw; the driving member is electrically connected to the controller, the screw is movably connected to the driving member, and the first glued mirror, the first single lens, and the second single lens are movably connected to the screw; the controller is also configured to send a control signal to the driving member so that the driving member drives the screw to rotate, thereby driving the first glued mirror, the first single lens, and the second single lens to move synchronously.

[0014] In an optional embodiment, the autofocus system further includes: an image quality compensation lens group; the image quality compensation lens group is located between the focus position biasing lens group and the dichroic mirror.

[0015] In an optional embodiment, the autofocus system further includes: an illumination light source; the illumination light source is located on one side of the dichroic mirror to emit illumination light to the dichroic mirror.

[0016] In a second aspect, an embodiment of the present disclosure also provides a focusing method using an automatic focusing system as described above, comprising: an incident light modulation component modulating the incident light into a projection pattern, and the projection pattern passes through a first beam splitter prism, a focus position bias mirror group, a dichroic mirror, and an objective lens in sequence to form an image on a wafer; the projection pattern is reflected on the wafer and passes through the objective lens, the dichroic mirror, the focus position bias mirror group, the first beam splitter prism to a return light collection component, so that the return light collection component obtains a current defocus amount; and the focus position bias mirror group moves between the first beam splitter prism and the dichroic mirror according to the current defocus amount until the current defocus amount reaches a set defocus amount.

[0017] The beneficial effect of the present invention is that, by setting a dichroic mirror, the present invention can enable the focusing light source and the illumination light source to share a set of objective lenses, and can automatically focus in the coaxial direction of the shallow depth of focus objective lens while avoiding additional optical path difference. The incident light modulation component cooperates with the return light collection component to collect the current defocus amount, and after comparing it with the set defocus amount, it is determined whether the wafer is in the focus position, and the focus position offset lens group is cooperated to realize focal length adjustment, meeting the requirement of a shallow depth of focus of the objective lens, so that the wafer is within the range of the depth of focus of the objective lens.

[0018] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purposes and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 A structural diagram of an automatic focusing system provided in an embodiment of the present disclosure; Figure 2 A schematic diagram of receiving a mask-modulated return image provided by an embodiment of the present disclosure; Figure 3 A block diagram of the principle of an automatic focusing system provided by an embodiment of the present disclosure; Figure 4 A schematic diagram of a first detector and a second detector receiving signals provided in an embodiment of the present disclosure; Figure 5 A path diagram of a focused light source on an objective lens and a wafer provided in an embodiment of the present disclosure; Figure 6 A structural diagram of a focus position offset lens assembly provided by an embodiment of the present disclosure; Figure 7 A point diagram of an objective lens imaging provided by an embodiment of the present disclosure; Figure 8 A field curvature distortion diagram of an objective lens imaging provided in an embodiment of the present disclosure.

[0022] In the picture: 1. Incident light modulation component; 101. Focusing light source; 102. Projection mask; 103. Converging lens group; 104. Reflecting mirror; 2. Return light collection assembly; 201. Second beam splitter prism; 202. Receiving mask; 2021. Return image; 2022. Black area; 203. First detector; 204. Second detector; 3. The first beam splitter prism; 4. Focus position offset lens group; 401. First cemented lens; 402. First single lens; 403. Second single lens; 404. Moving unit; 4041. Driving member; 4042. Lead screw; 5. Dichroic mirror; 6. Objective lens; 601. Lens one; 602. Lens two; 603. Lens three; 604. Lens four; 605. Lens five; 606. Lens six; 607. Lens seven; 608. Lens eight; 609. Lens nine; 6010. Lens ten; 7. Wafer; 8. Image quality compensation lens group; 9. Lighting source. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] In this document, when it is mentioned that a first component is located on a second component, this may mean that the first component may be directly formed on the second component, or that a third component may be interposed between the first component and the second component. In addition, in the drawings, the thickness of components may be exaggerated or reduced in order to effectively describe technical content.

[0025] As used herein, when an element or layer is referred to as being "located on," "engaged to," "connected to," "attached to," or "coupled to" another element or layer, it may be directly located on, engaged, connected, attached to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," "directly attached to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0026] The terms used herein are only used to describe specific exemplary configurations and are not intended to be limiting. As used herein, the singular articles "a", "an" and "the" may also be intended to include plural forms, unless otherwise clearly indicated herein. The terms "comprise", "include" and "have" are inclusive and therefore specify the presence of features, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or combinations thereof. The method steps, processes and operations described herein should not be interpreted as necessarily requiring them to be performed in the particular order discussed or shown, unless specifically identified as an execution order. Additional or alternative steps may be adopted.

[0027] As used herein, the phrases "in one embodiment," "according to one embodiment," "in some embodiments," and the like generally refer to the fact that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure. Thus, a particular feature, structure, or characteristic may be included in more than one embodiment of the present disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example," "exemplary," and the like are used to "serve as an example, instance, or illustration." Any implementation, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations, aspects, or designs. Instead, the use of the terms "example," "exemplary," and the like is intended to present concepts in a concrete manner.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0029] The following embodiments of the present invention are described in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0030] like Figures 1 to 8At least one embodiment provides an automatic focusing system for defect detection of a patterned wafer 7, comprising: an incident light modulation component 1, a return light collection component 2, a first beam splitter prism 3, a focus position biasing lens group 4, a dichroic mirror 5, and an objective lens 6; wherein the incident light modulation component 1, the return light collection component 2, and the focus position biasing lens group 4 are arranged around the first beam splitter prism 3, and the focus position biasing lens group 4, the dichroic mirror 5, and the objective lens 6 are arranged in sequence; the incident light modulation component 1 modulates the incident light into a projection pattern, and The projection pattern passes through the first beam splitter prism 3, the focus position bias lens group 4, the dichroic mirror 5, and the objective lens 6 in sequence to form an image on the wafer 7; the projection pattern is reflected on the wafer 7 and passes through the objective lens 6, the dichroic mirror 5, the focus position bias lens group 4, and the first beam splitter prism 3 to the return light collecting component 2, so that the return light collecting component 2 obtains the current defocus amount; and the focus position bias lens group 4 moves between the first beam splitter prism 3 and the dichroic mirror 5 according to the current defocus amount until the current defocus amount reaches the set defocus amount.

[0031] In at least one embodiment, by setting a dichroic mirror 5, the focusing light source 101 and the illumination light source 9 can share a set of objective lenses 6, and automatic focusing can be performed in the coaxial direction of the shallow depth of focus objective lens 6 while avoiding additional optical path difference. The incident light modulation component 1 cooperates with the return light collection component 2 to collect the current defocus amount, and after comparing it with the set defocus amount, it is determined whether the wafer 7 is in the focus position, and the focus position offset lens group 4 is cooperated to realize focal length adjustment to meet the requirement of a shallow depth of focus of the objective lens 6, so that the wafer 7 is within the focal depth range of the objective lens 6.

[0032] In at least one embodiment, the incident light modulation component 1 includes: a focused light source 101 and a projection mask 102; the focused light source 101, the projection mask 102, and the first beam splitter prism 3 are arranged in sequence; the focused light source 101 emits incident light toward the projection mask 102, so that the projection mask 102 modulates the incident light into a projection pattern.

[0033] Specifically, focused light source 101 can be an LED light source or a laser light source. The wavelength of focused light source 101 is in the infrared band, which can effectively prevent focused light source 101 from affecting illumination light source 9. Focused light source 101 passes through converging lens assembly 103 and then through projection mask 102. Projection mask 102 has a striped structure and can modulate the incident light into a striped pattern, referred to as a projection pattern.

[0034] Specifically, the reflecting mirror 104 is provided between the projection mask 102 and the first beam splitting prism 3 so as to fully utilize the space.

[0035] In at least one embodiment, see Figure 3The return light collecting component 2 includes: a second beam splitter prism 201, a receiving mask 202, a first detector 203, a second detector 204 and a controller; the second beam splitter prism 201 is located on one side of the first beam splitter prism 3, the receiving mask 202 is located between the first detector 203 and the first beam splitter prism 3, and the second detector 204 is located on one side of the second beam splitter prism 201; the first detector 203 and the second detector 204 are electrically connected to the controller; the projection pattern is respectively emitted to the receiving mask 202 and the second detector 204 through the first beam splitter prism 3 and the second beam splitter prism 201; the projection pattern passes through the receiving mask 202 to form a corresponding current return image 2021, so that the first detector 203 collects the light intensity value of the current return image 2021; the second detector 204 collects the light intensity value of the projection pattern; the controller obtains the current defocus amount according to the light intensity value of the current return image 2021 and the light intensity value of the projection pattern.

[0036] Specifically, the second beam splitter prism 201 splits the returning light into two beams of equal intensity. One beam of light is modulated again by the receiving mask 202 and then incident on the first detector 203 , while the other beam of light is directly incident on the second detector 204 . The first detector 203 and the second detector 204 convert the optical signal into an electrical signal.

[0037] In at least one embodiment, the receiving mask 202 is located at a conjugate position of the projection mask 102 and is responsible for modulating the return image 2021 .

[0038] In at least one embodiment, see Figure 2 The receiving mask 202 and the projection mask 102 are both arranged in a stripe shape, so that the projection pattern and the return image 2021 are both stripe images.

[0039] Specifically, see Figure 5 The focused light source 101 is incident from one end of the entrance pupil of the objective lens 6 and is emitted from the other end of the entrance pupil. When the wafer 7 is in the focused position, the return light forms a clear return image 2021 on the receiving mask 202. When the wafer 7 is in a downward or upward defocused state, the return image 2021 moves forward or backward relative to the receiving mask 202.

[0040] Specifically, see Figure 4 , the solid-line box represents the receiving mask 202, the dashed-line box represents the return image 2021, and the black area 2022 represents the light beam passing through the receiving mask 202. When the return image 2021 moves forward relative to the receiving mask 202, the black area 2022 expands, indicating that the light passing through the receiving mask 202 is increased; when the return image 2021 moves backward relative to the receiving mask 202, the black area 2022 shrinks, indicating that the light passing through the receiving mask 202 is decreased.

[0041] Specifically, see Figure 4 , wherein curve F represents the intensity value obtained after the return image 2021 passes through the receiving mask 202 and is received by the first detector 203, and curve N represents the intensity value obtained after the return image 2021 is directly received by the second detector 204. The current defocus amount can be obtained by the formula = F / N. Curve F will have a linear interval. Within this interval, when the value of curve F is greater than the middle value of the linear interval, wafer 7 is in a downward defocused position. When the value of curve F is less than the middle value, wafer 7 is in an upward defocused position. When the value of curve F is equal to the middle value, wafer 7 is in a focused position. The current defocus amount and defocus direction can be represented by the value of curve F. According to the relationship between curve F and the middle value of the linear interval, the position of wafer 7 can be adjusted to achieve a state where wafer 7 always remains in a focused position.

[0042] In at least one embodiment, the focus position biasing lens group 4 includes: a first cemented mirror 401, a first single lens 402, a second single lens 403 and a moving unit 404; the first cemented mirror 401, the first single lens 402, and the second single lens 403 are arranged in sequence and are all movably connected to the moving unit 404, and the moving unit 404 is electrically connected to the controller; the controller drives the moving unit 404 to drive the first cemented mirror 401, the first single lens 402, and the second single lens 403 to move synchronously.

[0043] Specifically, the focus position offset lens group 4 moves in the optical path to change the divergence angle of the light beam, thereby playing the role of focal length adjustment. The movement amount of the focus position offset lens group 4 is ±5mm, and the corresponding focal length adjustment range is ±3um. The light beam emitted from the focus position offset lens group 4 is parallel light.

[0044] Specifically, the first composite mirror 401 includes a biconvex lens and a biconcave lens, the first single lens 402 is a biconcave lens, the second single lens 403 is a plano-convex lens, and the biconvex lens in the first composite mirror 401 has a positive optical focal length, and the biconcave lens in the first composite mirror 401 has a negative optical focal length, that is, the first composite mirror 401 has a positive optical focal length and is responsible for converging the light passing through the projection mask 102; the first single lens 402 has a negative optical focal length; and the second single lens 403 has a positive optical focal length.

[0045] Specifically, the first composite mirror 401 has seven surfaces arranged in sequence from front to back, and the curvature radius of surface one is 48.52mm, the corresponding thickness is 10.34mm, and the material is H-ZLAF68B; the curvature radius of surface two is -30mm, the corresponding thickness is 15.82mm, and the material is H-ZF71; the curvature radius of surface three is 50.82mm, the corresponding thickness is 110mm, and the material is air; the curvature radius of surface four is -26.18mm, the corresponding thickness is 15.5mm, and the material is H-QF6A; the curvature radius of surface five is 23.3mm, the corresponding thickness is 17.5mm, and the material is air; the curvature radius of surface six is ​​infinite, the corresponding thickness is 14mm, and the material is H-LAK8A; the curvature radius of surface seven is -33mm, the corresponding thickness is 800mm, and the material is air.

[0046] In at least one embodiment, the moving unit 404 includes: a driving member 4041 and a screw rod 4042; the driving member 4041 is electrically connected to the controller, the screw rod 4042 is movably connected to the driving member 4041, and the first glued mirror 401, the first single lens 402, and the second single lens 403 are movably connected to the screw rod 4042; the controller is suitable for sending a control signal to the driving member 4041, so that the driving member 4041 drives the screw rod 4042 to rotate, thereby driving the first glued mirror 401, the first single lens 402, and the second single lens 403 to move synchronously.

[0047] In at least one embodiment, the autofocus system further includes: an image quality compensation lens group 8 ; the image quality compensation lens group 8 is located between the focus position biasing lens group 4 and the dichroic mirror 5 .

[0048] Specifically, the image quality compensation lens group 8 includes a second cemented lens, which includes a biconvex lens and a meniscus lens. The biconvex lens has a negative optical focal length, and the meniscus lens has a positive optical focal length.

[0049] Specifically, the second composite mirror has three surfaces in sequence from front to back, and the curvature radius of surface one is 150.32mm, the corresponding thickness is 15mm, and the material is H-BAK3; the curvature radius of surface two is -101.42mm, the corresponding thickness is 6mm, and the material is H-ZF73; the curvature radius of surface three is -206.65mm, the corresponding thickness is 120mm, and the material is air.

[0050] Specifically, the focused light source 101 must utilize a different wavelength band than the illumination light source 9. Using a focused light source 101 with a wavelength band of 615nm±5nm and designing the illumination light entering the objective lens 6 as parallel light facilitates optimal image quality. A piece of glass that reflects the 615nm±5nm wavelength band and transmits the 266nm wavelength is placed in front of the objective lens 6, allowing both the illumination light and the focused light to enter the objective lens 6 simultaneously. To achieve optimal image quality in the infrared band, an image quality compensation lens assembly 8 is provided. This not only ensures image quality for the autofocus system but also allows for individual replacement of the image quality compensation lens assembly 8 based on the specifications of subsequent objective lenses 6, ensuring repeatable optical paths.

[0051] In at least one embodiment, the autofocus system further includes: an illumination light source 9 ; the illumination light source 9 is located on one side of the dichroic mirror 5 to emit illumination light to the dichroic mirror 5 .

[0052] Specifically, the illumination light passes through the dichroic mirror 5 and is converged by the objective lens 6 onto the wafer 7 .

[0053] Specifically, the objective lens 6 comprises lens one 601, lens two 602, lens three 603, lens four 604, lens five 605, lens six 606, lens seven 607, lens eight 608, lens nine 609, and lens ten 6010, which are arranged in sequence from the object plane along the optical axis; and lens one 601 and lens two 602 constitute a first lens group with negative optical focal length; lens three 603, lens four 604, and lens five 605 constitute a second lens group with positive optical focal length, which collimates the light beam into quasi-parallel light; lens six 606, lens seven 607, and lens eight 608 constitute a third lens group with positive optical focal length; and lens nine 609 and lens ten 6010 constitute a fourth lens group with positive optical focal length, which focuses the light beam.

[0054] Specifically, lens one 601 is a plano-concave lens, which bends toward the image plane, one side of which is flat, centrally transmitted and has a circular area, and the other side is concave; lens two 602 is a double concave lens; lens three 603 is a meniscus lens, which bends toward the object plane; lens four 604 is a double convex positive lens; lens five 605 is a plano-convex lens; lens six 606 is a meniscus negative lens, which bends toward the image plane; lens seven 607 is a plano-convex lens; lens eight 608 is a plano-convex lens; lens nine 609 is a meniscus positive lens, which bends toward the image plane; lens ten 6010 is a meniscus positive lens, which bends toward the image plane.

[0055] Specifically, all lenses of the objective lens 6 are spherical, the half field of view is equal to 4.8 degrees, all optical elements are made of fused silica, and the laser spectrum ranges are 266 nm and 615 nm.

[0056] Specifically, the objective lens 6 is provided with twenty faces in sequence, and the curvature radius of face 1 is infinite, the corresponding thickness is 12.5 mm, and the material is JGS1; the curvature radius of face 2 is 47.47 mm, the corresponding thickness is 12 mm, and the material is air; the curvature radius of face 3 is -35.46 mm, the corresponding thickness is 12.5 mm, and the material is JGS1; the curvature radius of face 4 is 135.76, the corresponding thickness is 11 mm, and the material is air; the curvature radius of face 5 is -220.8 mm, the corresponding thickness is 15mm, material is JGS1; the curvature radius of surface six is ​​-65.38mm, its corresponding thickness is 8mm, the material is air; the curvature radius of surface seven is 281.73mm, its corresponding thickness is 15mm, the material is JGS1; the curvature radius of surface eight is -160.41mm, its corresponding thickness is 8mm, the material is air; the curvature radius of surface nine is 123.28mm, its corresponding thickness is 15mm, the material is JGS1; the curvature radius of surface ten is infinite, its corresponding thickness is 30mm, the material is The curvature radius of surface 11 is 126.93mm, the corresponding thickness is 15mm, and the material is JGS1; the curvature radius of surface 12 is 78.62mm, the corresponding thickness is 30mm, and the material is air; the curvature radius of surface 13 is infinite, the corresponding thickness is 15mm, and the material is JGS1; the curvature radius of surface 14 is -134.45mm, the corresponding thickness is 2.5mm, and the material is air; the curvature radius of surface 15 is 154.8mm, the corresponding thickness is 15mm, and the material is JG S1; the curvature radius of surface 16 is infinite, its corresponding thickness is 5mm, and the material is air; the curvature radius of surface 17 is 58.17mm, its corresponding thickness is 12.5mm, and the material is JGS1; the curvature radius of surface 18 is 119.18mm, its corresponding thickness is 5mm, and the material is air; the curvature radius of surface 19 is 53.56mm, its corresponding thickness is 12.5mm, and the material is JGS1; the curvature radius of surface 20 is 113.78mm, its corresponding thickness is 43mm, and the material is air.

[0057] Specifically, see Figure 7 ,Through the point array diagram formed after objective lens 6, we can see that the light spots are all within the diffraction limit, and the maximum field of view is ±0.428mm of image height.

[0058] Specifically, see Figure 8 , the field curvature distortion diagram of the image after passing through objective lens 6, the field curvature is smaller than the focal depth, and the distortion is within 1%.

[0059] Based on the same technical concept, at least one embodiment also provides a focusing method using an automatic focusing system as described above, which includes: the incident light modulation component 1, the return light collection component 2, and the focus position bias mirror group 4 are arranged around the first beam splitter prism 3, and the focus position bias mirror group 4, the dichroic mirror 5, and the objective lens 6 are arranged in sequence; the incident light modulation component 1 modulates the incident light into a projection pattern, and the projection pattern passes through the first beam splitter prism 3, the focus position bias mirror group 4, the dichroic mirror 5, and the objective lens 6 in sequence to form an image on the wafer 7; the projection pattern is reflected on the wafer 7 and passes through the objective lens 6, the dichroic mirror 5, the focus position bias mirror group 4, the first beam splitter prism 3 to the return light collection component 2, so that the return light collection component 2 obtains the current defocus amount; and the focus position bias mirror group 4 moves between the first beam splitter prism 3 and the dichroic mirror 5 according to the current defocus amount until the current defocus amount reaches the set defocus amount.

[0060] In summary, the present invention enables the focusing light source and the illumination light source to share a set of objective lenses by setting a dichroic mirror, and can automatically focus in the coaxial direction of the shallow depth of focus objective lens while avoiding additional optical path difference. The incident light modulation component cooperates with the return light collection component to collect the current defocus amount, and compares it with the set defocus amount to determine whether the wafer is in the focus position, and cooperates with the focus position offset lens group to realize focal length adjustment, meet the requirement of a shallow depth of focus of the objective lens, and make the wafer within the focal depth range of the objective lens.

[0061] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0062] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, terms such as "first", "second" and other numerical terms do not imply an order or sequence when used herein unless expressly indicated above. Therefore, without departing from the teachings of the example embodiments, the first element, component, region, layer or section discussed above may be referred to as a second element, component, region, layer or section.

[0063] Spatially relative terms, such as "inside," "outside," "below," "beneath," "down," "above," "on," etc., may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. In addition to the orientations depicted in the figures, spatially relative terms may be intended to encompass different orientations of the device in use or operation. For example, if the device in the figures is flipped, an element described as being "below" or "below" other elements or features will be oriented to be "above" the other elements or features. Thus, the example term "below" may encompass both above and below orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0064] In the above discussion, unless otherwise indicated, the terms "about," "approximately," "substantially," etc., when used to describe a numerical value, mean a variation of + / - 10% of the value.

[0065] With the above-described preferred embodiments of the present invention as inspiration, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. An automatic focusing system for pattern wafer defect detection, characterized in that: include: An incident light modulation component (1), a return light collection component (2), a first beam splitter prism (3), a focus position offset lens group (4), a dichroic mirror (5) and an objective lens (6); wherein The incident light modulation component (1), the return light collection component (2), and the focus position biasing mirror group (4) are arranged around the first beam splitting prism (3), and the focus position biasing mirror group (4), the dichroic mirror (5), and the objective lens (6) are arranged in sequence; The incident light modulation component (1) modulates the incident light into a projection pattern, and the projection pattern passes through the first beam splitter prism (3), the focus position offset lens group (4), the dichroic mirror (5), and the objective lens (6) in sequence to form an image on the wafer (7); The projection pattern is reflected on the wafer (7) and passes through the objective lens (6), the dichroic mirror (5), the focus position offset lens group (4), and the first beam splitter prism (3) to the return light collection component (2), so that the return light collection component (2) obtains the current defocus amount; and The focus position offset lens group (4) moves between the first beam splitter prism (3) and the dichroic mirror (5) according to the current defocus amount until the current defocus amount reaches the set defocus amount.

2. The automatic focusing system according to claim 1, wherein: The incident light modulation component (1) comprises: a focusing light source (101) and a projection mask (102); The focusing light source (101), the projection mask (102), and the first beam splitting prism (3) are arranged in sequence; The focused light source (101) emits incident light toward the projection mask (102), so that the projection mask (102) modulates the incident light into a projection pattern.

3. The automatic focusing system according to claim 2, wherein: The return light collection component (2) comprises: a second beam splitter prism (201), a receiving mask (202), a first detector (203), a second detector (204) and a controller; The second beam splitter prism (201) is located on one side of the first beam splitter prism (3), the receiving mask (202) is located between the first detector (203) and the first beam splitter prism (3), and the second detector (204) is located on one side of the second beam splitter prism (201); The first detector (203) and the second detector (204) are electrically connected to the controller; The projection pattern is emitted toward the receiving mask (202) and the second detector (204) respectively via the first beam splitter prism (3) and the second beam splitter prism (201); The projection pattern passes through the receiving mask (202) to form a corresponding current return image (2021), so that the first detector (203) collects the light intensity value of the current return image (2021); The second detector (204) collects the light intensity value of the projection pattern; The controller is configured to obtain a current defocus value according to a light intensity value of a current returned image (2021) and a light intensity value of a projection pattern.

4. The automatic focusing system according to claim 3, wherein: The receiving mask (202) is located at a conjugate position of the projection mask (102).

5. The automatic focusing system according to claim 3, wherein: The receiving mask (202) and the projection mask (102) are both arranged in a stripe shape.

6. The automatic focusing system according to claim 3, wherein: The focus position offset lens group (4) comprises: a first cemented lens (401), a first single lens (402), a second single lens (403) and a moving unit (404); The first glued mirror (401), the first single lens (402), and the second single lens (403) are arranged in sequence and are all movably connected to the moving unit (404); the moving unit (404) is electrically connected to the controller; The controller is also configured to drive the moving unit (404) to drive the first cemented mirror (401), the first single lens (402), and the second single lens (403) to move synchronously.

7. The automatic focusing system according to claim 6, wherein: The moving unit (404) comprises: a driving member (4041) and a screw rod (4042); The driving member (4041) is electrically connected to the controller, the screw rod (4042) is movably connected to the driving member (4041), and the first glued mirror (401), the first single lens (402), and the second single lens (403) are movably connected to the screw rod (4042); The controller is also configured to send a control signal to the driving member (4041) so that the driving member (4041) drives the lead screw (4042) to rotate, thereby driving the first cemented mirror (401), the first single lens (402), and the second single lens (403) to move synchronously.

8. The automatic focusing system according to claim 1, wherein: Also includes: Image quality compensation lens group (8); The image quality compensation lens group (8) is located between the focus position offset lens group (4) and the dichroic mirror (5).

9. The automatic focusing system according to claim 1, wherein: Also includes: Light source (9); The illumination light source (9) is located on one side of the dichroic mirror (5) to emit illumination light to the dichroic mirror (5).

10. A focusing method using the automatic focusing system according to any one of claims 1 to 9, characterized in that: include: The incident light modulation component (1) modulates the incident light into a projection pattern, and the projection pattern passes through a first beam splitter prism (3), a focus position offset lens group (4), a dichroic mirror (5), and an objective lens (6) in sequence to form an image on a wafer (7); The projection pattern is reflected on the wafer (7) and transmitted to the return light collection component (2) via the objective lens (6), the dichroic mirror (5), the focus position offset lens group (4), and the first beam splitter prism (3), so that the return light collection component (2) obtains the current defocus amount; and The focus position offset lens group (4) moves between the first beam splitter prism (3) and the dichroic mirror (5) according to the current defocus amount until the current defocus amount reaches the set defocus amount.

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