A crystal bright and dark field defect detection device

Abstract

The present application provides a wafer bright and dark field defect detection device, which is equipped with objective lenses of multiple magnifications. These objective lenses can be flexibly switched according to the requirements of detection accuracy, thereby realizing switching between high detection accuracy and low detection speed and low detection accuracy and high detection speed; and the dark field illumination beam is precisely configured at the dark field light source end, so that the dark field illumination spot covers the collection field of view corresponding to the dark field detector under the required multiple objective lens magnifications, and crosstalk between the bright and dark field collection fields is avoided by effectively controlling the dark field illumination spot area.

Description

Technical Field

[0001] The present application relates to the field of semiconductor detection technology, and in particular to a wafer bright and dark field defect detection device. Background Art

[0002] In the field of semiconductor inspection, brightfield inspection is a key optical inspection method. However, brightfield inspection is limited by the diffraction limit, and the minimum detectable defect is only the radius of the Airy disk. Darkfield inspection, on the other hand, relies on Rayleigh or Mie scattering from small particles. By detecting the scattered signal from small defects, it can improve detection sensitivity. Therefore, to enhance the detection sensitivity of the inspection device, a darkfield device is often configured within the brightfield device to form a bright-darkfield inspection system.

[0003] Typically, the intensity of brightfield signal light is much greater than that of darkfield signal light, significantly interfering with it and reducing darkfield detection accuracy. To address this issue, some solutions perform separate brightfield and darkfield detection on the sample being tested, followed by data fusion. This approach is time-consuming, and vibrations during the detection process can cause errors in the alignment of the two detections, reducing detection accuracy. Other solutions use different wavelengths of illumination for the bright and dark fields to distinguish between the bright and dark field signal light. However, the wafer being tested responds differently to different illumination wavelengths, and this band-based approach limits the detection band. Summary of the Invention

[0004] In view of this, the present invention provides a wafer bright and dark field defect detection device to improve wafer detection accuracy.

[0005] In order to solve the technical problem that the wafer detection accuracy in the existing solution needs to be improved, this application adopts the following technical solution:

[0006] One of the purposes of the present application is to provide a wafer bright-field and dark-field defect detection device, comprising a bright-field illumination source, an objective lens, a dark-field illumination source, a bright-field detector, and a dark-field detector, wherein the objective lens has multiple switchable magnifications;

[0007] The light beam emitted by the bright field illumination light source is irradiated onto the surface of the wafer to be measured through the objective lens, and the bright field signal light generated by the reflection passes through one side of the optical axis behind the objective lens to form a bright field acquisition field which is captured by the bright field detector, and an image is formed to obtain a bright field image;

[0008] The light beam emitted by the dark field illumination light source is irradiated onto the surface of the wafer to be measured, and the dark field signal light generated by scattering passes through the other side of the optical axis of the objective lens to form a dark field acquisition field that is captured by the dark field detector, and a dark field image is obtained by imaging; wherein:

[0009] The distribution of the dark field illumination spot on the surface of the wafer to be measured is controlled by configuring the light emitting surface of the dark field illumination light source so that the dark field illumination spot covers the dark field acquisition field corresponding to all magnifications of the objective lens and avoids crosstalk with the bright field acquisition field;

[0010] The bright field image and the dark field image are collected simultaneously and used to obtain the bright field defect characteristics and the dark field defect characteristics of the surface of the wafer under test respectively through image processing.

[0011] In some embodiments, the width, length and light intensity of the light emitting surface of the dark field illumination light source are configured so that the light beam meets the distribution requirements of the dark field illumination light spot.

[0012] In some embodiments, the length of the light-emitting surface of the dark field illumination light source is C′=C / MI, the width of the light-emitting surface of the dark field illumination light source is W′=W×cos(θ) / MI, and the size of the light-emitting surface of the dark field illumination light source is configured as C′×W′, wherein: C is the length of the dark field illumination spot, MI is the magnification of the dark field illumination light path through which the light beam emitted by the dark field illumination light source passes, W is the width of the dark field illumination spot, θ is the angle between the illumination light and the normal of the wafer to be measured, θ is 40-70 degrees, and the opening size of the aperture element is C′×W′.

[0013] In some embodiments, the light beam emitted by the dark field illumination light source is imaged on the surface of the wafer under test through the dark field illumination optical path, and forms a narrow and long dark field illumination spot on the surface of the wafer under test; the dark field illumination optical path includes a first lens group, an aperture element and a second lens group arranged in sequence, the first lens group and the second lens group constitute a coupling lens group, and the aperture element is arranged on the object focal plane of the coupling lens group.

[0014] In some embodiments, the coupling lens group and the objective lens have the same or slightly larger numerical aperture, the aperture element has a preset opening size and satisfies C′×W′, wherein C′=C / MI, W′=W×cos(θ) / MI, C is the length of the dark field illumination spot, MI is the magnification of the dark field illumination light path, W is the width of the dark field illumination spot, and θ is the angle between the illumination light and the normal of the wafer under test.

[0015] In some embodiments, there are two dark field illumination light sources, the dark field illumination light paths through which the light beams emitted by the two dark field illumination light sources pass are symmetrically distributed, and the illumination areas formed on the surface of the wafer to be measured are combined to produce the dark field illumination spot, and the incident plane of the light beam emitted by the dark field illumination light source incident on the surface of the wafer to be measured is not perpendicular to the plane where the dark field illumination spot is located.

[0016] In some embodiments, there is one dark field illumination light source, and the incident plane of the light beam emitted by the dark field illumination light source onto the surface of the wafer to be measured is inclined to the plane where the dark field illumination spot is located.

[0017] In some embodiments, a spectroscopic element having two reflective surfaces is further included. The bright field signal light and dark field signal light generated on the surface of the wafer to be measured are incident on the two reflective surfaces of the spectroscopic element respectively through a common imaging optical path. The two reflective surfaces of the spectroscopic element reflect the bright field signal light and the dark field signal light to the bright field detector and the dark field detector respectively.

[0018] In some embodiments, the bright field detector and the dark field detector are respectively a bright field camera and a dark field camera, the imaging planes of the bright field camera and the dark field camera are conjugate to the plane where the wafer to be measured is located, the field of view center of the bright field camera and the field of view center of the dark field camera are symmetrically distributed about the optical center field of view and the distance from the optical center field of view is L; the common imaging optical path through which the bright field signal light and the dark field signal light pass is the minimum magnification M min The distance between the bright field acquisition field and the dark field acquisition field and the optical center field is L1=L / M. min ;

[0019] The common imaging optical path through which the bright field signal light and the dark field signal light pass is the maximum magnification M max The distance between the bright field acquisition field and the dark field acquisition field and the optical center field is L2=L / M. max ;

[0020] The target length of the bright field camera and the dark field camera is K, and the corresponding maximum length on the object side is K′=K / M min .

[0021] In some embodiments, the distribution of the dark field illumination spot meets the following parameter requirements:

[0022] The width of the dark field illumination spot W is the dark field field under all magnifications, and the width of the dark field W = L2-L1 = L / (M max -M min );

[0023] The distance between the illumination boundary of the dark field illumination spot and the optical center field of view is B=L / M min +a, a is the diffusion width of the dark field illumination spot, a is 0.1~0.5mm;

[0024] The dark field illumination spot length C=K′+b, where b is the range where the illumination spot is larger than the field of view required for imaging, and b is 1-5 mm;

[0025] The illumination uniformity of the dark field illumination spot in the spot width and the spot length is greater than 80%, and the illumination uniformity is the minimum illumination of the illumination spot divided by the maximum illumination value.

[0026] This application adopts the above technical solution, and its beneficial effects are as follows:

[0027] The wafer bright and dark field defect detection device provided by the present application is provided with a dark field illumination light source. The dark field illumination light source is used to regulate the distribution of the dark field illumination spot in the dark field acquisition field of view, so that the dark field illumination spot covers the dark field acquisition field of view corresponding to the objective lens at all magnifications, thereby solving the problem of changes in the dark field acquisition field of view corresponding to the dark field detector when the objective lens is switched. At the same time, the dark field illumination light source is used to control the dark field illumination spot area to avoid crosstalk with the bright field acquisition field of view. By precisely configuring the dark field illumination beam at the dark field light source end, it will not affect the bright field imaging, and will also cover the dark field imaging field of view at multiple magnifications, ensuring the dark field illumination requirements while improving the accuracy of dark field detection.

[0028] The wafer bright and dark field defect detection device provided in this application realizes simultaneous detection of bright and dark fields with a common optical path and separate fields of view, and can support switching of different magnifications of the same objective lens to synchronously change the imaging magnification, thereby realizing switching between high detection accuracy and low detection speed and low detection accuracy and high detection speed, thereby better meeting different application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] Figure 1 A schematic structural diagram of a semiconductor wafer bright and dark field defect detection device provided in Example 1 of the present application;

[0031] Figure 2 A schematic diagram of a specific optical path provided in Example 1 of the present application;

[0032] Figure 3 A schematic diagram of the installation position of the camera target surface on the image side provided in Example 1 of the present application;

[0033] Figure 4 This is a diagram illustrating the common optical path field of view distribution of bright and dark fields provided in Example 1 of the present application;

[0034] Figure 5 This is an optical schematic diagram of the dark field illumination solution provided in Example 1 of the present application;

[0035] Figure 6 A detailed optical schematic diagram of the dark field illumination solution provided in Example 1 of the present application;

[0036] Figure 7 This is an optical schematic diagram of another dark field illumination solution provided in Example 1 of the present application. DETAILED DESCRIPTION

[0037] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0038] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application 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 should not be understood as a limitation on this application.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0040] In order to make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below with reference to the accompanying drawings and embodiments.

[0041] Example 1

[0042] See also Figure 1 , which is a schematic diagram of the structure of the wafer bright-field and dark-field defect detection device provided in Example 1 of the present application, includes a bright-field illumination source 100, an objective lens 200, a dark-field illumination source 300, a bright-field detector 400, and a dark-field detector 500. The objective lens 200 has multiple switchable magnifications. The technical solution for implementing this is described in detail below.

[0043] The brightfield illumination light source 100 is used to emit a brightfield illumination beam. The specific structure of the brightfield illumination light source 100 is not limited and can be a single light source or multiple light sources. The light beam emitted by the brightfield illumination light source 100 can be split or combined to meet optical path requirements to ensure the flexibility of the entire system.

[0044] The objective lens 200 can be configured as a plurality of objective lenses with switchable magnifications. In practice, these objective lenses can be flexibly switched according to the requirements of detection accuracy. After the objective lens is switched, the dark field field of the dark field detector will also change due to the change in the microscopic magnification of the imaging system.

[0045] In some embodiments, the objective lens 200 may be configured to include a combination of multiple objective lenses with different magnifications, such as Figure 1 The combination of objective lenses 1, ... and n shown in the figure can switch the objective lenses of corresponding magnifications into the optical path according to the actual detection accuracy requirements.

[0046] In some embodiments, the objective lens 200 can also be configured to include a single objective lens and an objective lens converter. The objective lens converter can switch the objective lens to different magnifications, and the objective lens of the corresponding magnification can be switched into the optical path according to the actual detection accuracy requirements.

[0047] The dark field illumination light source 300 is used to emit a dark field illumination light beam. The specific structure of the dark field illumination light source 300 is not limited and can be a single light source or multiple light sources. The light beam emitted by the dark field illumination light source 300 can be split or combined to meet the optical path requirements to ensure the flexibility of the entire system.

[0048] In this embodiment, the dark field illumination light source 300 can be set according to actual needs. For example, the width, length and light intensity of the light emitting surface of the dark field illumination light source 300 can be appropriately configured as needed; or the light beam of the dark field illumination light source 300 can be shaped; or the light beam position of the dark field illumination light source 300 can be adjusted to meet the detection needs.

[0049] The bright field detector 400 and the dark field detector 500 are used to obtain the imaging signal of the bright field illumination light source and the imaging signal of the dark field illumination light source, respectively.

[0050] In some embodiments, the bright field detector 400 and the dark field detector 500 are a bright field camera and a dark field camera, respectively.

[0051] The working method of the semiconductor wafer bright and dark field defect detection device provided in the above embodiment of the present application is as follows:

[0052] The light beam emitted by the bright field illumination light source 100 is irradiated onto the surface of the wafer to be measured through the objective lens 200. The bright field signal light generated by the reflection passes through one side of the optical axis of the objective lens 200 to form a bright field acquisition field that is captured by the bright field detector 400, and a bright field image is obtained by imaging. The light beam emitted by the dark field illumination light source 300 is irradiated onto the surface of the wafer to be measured. The dark field signal light generated by the scattering passes through the other side of the optical axis of the objective lens 200 to form a dark field acquisition field that is captured by the dark field detector 500, and a dark field image is obtained by imaging.

[0053] By configuring the light-emitting surface of the dark field illumination light source 300, the distribution of the dark field illumination spot on the surface of the wafer to be measured is controlled so that the dark field illumination spot covers the dark field acquisition field corresponding to all magnifications of the objective lens 200 and avoids crosstalk with the bright field acquisition field; in addition, the bright field image and the dark field image are collected simultaneously and used to obtain the bright field defect characteristics and dark field defect characteristics of the surface of the wafer to be measured respectively through image processing.

[0054] It should be noted that the dark field illumination spot needs to be larger than the dark field acquisition field of view to ensure imaging uniformity. Of course, the bright field imaging spot also needs to be larger than the bright field acquisition field of view.

[0055] The wafer bright and dark field defect detection device provided in this embodiment is provided with objective lenses with multiple magnifications, and these objective lenses can be flexibly switched according to the requirements of detection accuracy. After the objective lens is switched, the dark field field of view corresponding to the dark field detector will also change due to the change in the microscope magnification of the imaging system. This will cause some unexpected situations, such as the dark field illumination spot is too small to cover the entire dark field imaging field of view (i.e., the dark field imaging field of view), and the dark field illumination spot is too large to interfere with the bright field imaging. The present application accurately configures the dark field illumination beam at the dark field light source end, so that the dark field illumination spot covers the dark field of view corresponding to the dark field detector under the required multiple objective lenses, and at the same time controls the dark field illumination spot area to avoid crosstalk with the bright field signal.

[0056] In some embodiments, the width, length, and light intensity of the light-emitting surface of the dark-field illumination light source 300 are configured to meet the dark-field illumination spot distribution requirements. For example, the light path can be designed so that the light beam emitted by the dark-field illumination light source 300, after being magnified by the dark-field illumination lens assembly, precisely meets the dark-field illumination spot distribution requirements. This ensures that the dark-field illumination spot covers the dark-field fields of view corresponding to the dark-field detectors under the required multiple objective lenses, while also controlling the dark-field illumination spot area to avoid crosstalk with the bright-field signal.

[0057] See also Figure 2 , which is a schematic diagram of a specific optical path provided in Example 1 of the present application, includes: a bright field illumination light source 100, a reflector 10, a spectrometer 20, a dichroic mirror 30, an imaging lens assembly 40, a focus detection assembly 50, an objective lens 200, a dark field illumination light source 300, a bright field detector 400, a dark field detector 500, and a spectrometer assembly 600. The specific optical path is as follows:

[0058] The light beam emitted by the bright field illumination light source 100 passes through the reflector 10, the spectrometer 20, the dichroic mirror 30 and the objective lens 200 in sequence to irradiate the surface of the wafer under test. The bright field signal light generated by the reflection passes through one side of the optical axis of the objective lens 200, and then passes through the dichroic mirror 30 and the imaging lens group 40. The bright field acquisition field formed by the spectrometer component 600 is captured by the bright field detector 400 and the bright field image is obtained by imaging.

[0059] The light beam emitted by the dark field illumination light source 300 is irradiated onto the surface of the wafer to be measured. The scattered dark field signal light passes through the other side of the optical axis of the objective lens 200, and then passes through the dichroic mirror 30 and the imaging lens group 40, and then through the dark field acquisition field formed by the spectrometer component 600 to be captured by the dark field detector 500, and a dark field image is obtained by imaging.

[0060] In this embodiment, the spectroscopic component 600 is a spectroscopic prism or a polygonal reflector. The spectroscopic prism can be a right-angle isosceles prism, and the polygonal reflector can be an isosceles trapezoidal structure with reflectors on both sides. The bright field detector 400 and the dark field detector 500 are a bright field camera and a dark field camera respectively.

[0061] It can be understood that the main optical path provided in the above-mentioned embodiment of the present application utilizes a spectroscopic component 600 with two reflective surfaces. The bright field signal light and dark field signal light generated on the surface of the wafer to be measured are respectively incident on the two reflective surfaces of the spectroscopic component 600 through a common imaging optical path. The two reflective surfaces of the spectroscopic component 600 reflect the bright field signal light and the dark field signal light to the bright field detector 400 and the dark field detector 500, respectively.

[0062] Furthermore, the center of the beam splitter assembly 600 coincides with the optical axis, reflecting two relatively narrow fields of view outside the optical axis onto the target surfaces of the brightfield camera and the darkfield camera, respectively. Both the brightfield camera and the darkfield camera are line scan cameras, which have a very small field of view in the scanning dimension. Therefore, the two narrow fields of view distributed by the beam splitter assembly provided in this application meet the field of view width of the scanning dimension. No beam splitting is performed in the direction perpendicular to the schematic diagram, thus meeting the full field of view requirements of the line scan camera along the length of the target surface.

[0063] See also Figure 3 , is a schematic diagram of the installation position of the camera target surface on the image side provided in this embodiment 1.

[0064] In this embodiment, the imaging planes of the bright field camera and the dark field camera are conjugate with the plane of the wafer to be measured. Since the bright field camera and the dark field camera are arranged in a paraxial layout, the field of view center (photosensitive position) of the bright field camera and the field of view center (photosensitive position) of the dark field camera are symmetrically distributed with respect to the optical center field of view, and the distance from the optical center field of view is L. The conjugate positions of the bright field field of view and the dark field field of view on the wafer are related to the magnification of the optical system.

[0065] It can be understood that the present application changes the system magnification by switching the objective lens magnification (such as 1X to 20X, etc.), that is, when switching to other magnification objective lenses, the bright field and dark field acquisition positions will be changed from solid lines (such as Figure 3 If the magnification is multiple, there will be multiple acquisition positions for the bright field and dark field, such as Figure 4 As shown, the common imaging optical path through which the bright field signal light and the dark field signal light pass is the lowest magnification Mmin Under the condition of 1:1, the distance between the bright field acquisition field and the dark field acquisition field and the central field of view is L1=L / M min ; The common imaging optical path through which the bright field signal light and the dark field signal light pass is the maximum magnification M max The distance between the bright field and dark field and the central field of view is L2=L / M. max The length of the camera target surface K corresponds to the maximum length on the object side K′=K / M min .

[0066] Please refer to Figure 4 In the optical imaging field of view, since the bright field camera and the dark field camera are symmetrically distributed around the central field of view (optical axis), the specific positions of the bright field and the dark field are different at different magnifications. For the existing technology, since the camera is at the center of the field of view, this problem does not exist, so the dark field illumination is usually a very narrow linear spot, and there is no need to consider covering multiple fields of view, and there is no need to consider the uniformity in the scanning direction; the dark field of view provided by this application needs to be based on the requirements of the optical system for simultaneous detection of bright and dark fields. It is a dark field illumination with good uniformity and clear boundaries of the illumination spot. The dark field illumination spot covers the corresponding dark field of view at all magnifications and avoids crosstalk with the bright field of view. The specific distribution of the dark field illumination spot meets the following parameter requirements:

[0067] The width of the dark field illumination spot W is the dark field field under all magnifications, and the spot width W=L2-L1=L / (M max -M min ).

[0068] The distance between the illumination boundary of the dark field illumination spot and the optical center field of view is B=L / M min +a, a is the diffusion width of the dark field illumination spot, which is theoretically close to 0. In practice, it needs to be combined with the difficulty of dark field illumination design. In this application, a is preferably 0.1~0.5mm.

[0069] The spot length of the dark field illumination spot is C=K′+b, where b is the range in which the illumination spot is larger than the field of view required for imaging. Usually, in order to reduce engineering difficulty, some redundancy is removed. In this application, b is preferably 1~5mm.

[0070] The illumination uniformity of the dark field illumination spot in both the spot width and the spot length is greater than 80%. The illumination uniformity is the minimum illumination of the illumination spot divided by the maximum illumination value.

[0071] It can be understood that by controlling the width, length and light intensity of the light emitting surface of the dark field illumination light source 300, the distribution of the dark field illumination spot can meet the above parameter requirements to ensure that the dark field illumination spot covers the dark field of view corresponding to the dark field detector under the required multiple objective lenses, and at the same time control the dark field illumination spot area to avoid crosstalk with the bright field signal.

[0072] See also Figure 5 , which is an optical schematic diagram of the dark field illumination solution provided in Example 1 of the present application.

[0073] In this embodiment, to ensure illumination uniformity, the dark-field illumination solution provided in this embodiment uses external oblique incident illumination, that is, the light beams emitted by the two dark-field illumination light sources are incident on the surface of the wafer under test through the corresponding dark-field illumination light paths, and the incident plane is not perpendicular to the plane where the dark-field illumination spot is located. In other words, the two dark-field illumination light paths are arranged on the same side of the optical center field of view, symmetrically with the vertical plane of the optical center field of view, and both emit illumination beams to the surface of the wafer at a certain oblique angle. The two illumination beams overlap on the wafer surface, and the overlapping area constitutes the dark-field illumination spot. It can be understood that for a surface light source with good uniformity to be projected onto the required illumination position on the surface of the wafer under test, the lighting device needs to reach the imaging level to ensure a clear dark-field illumination contour.

[0074] In this embodiment, the light beam emitted by the dark-field illumination light source is imaged onto the surface of the wafer under test via the dark-field illumination optical path, forming a narrow dark-field illumination spot on the surface of the wafer under test. The dark-field illumination optical path employs critical illumination, i.e., the light beam emitted by the dark-field illumination light source passes through the illumination lens assembly and forms an image on the wafer surface. This illumination method can produce a narrow and intense illumination characteristic on the wafer surface, where a uniform light source image is projected onto areas corresponding to multiple dark-field magnifications. Of course, in some cases, by adjusting the lens assembly structure of the dark-field illumination optical path, it is possible to change to Köhler illumination, which easily produces a more uniform dark-field illumination spot.

[0075] See also Figure 6 , which is a detailed optical schematic diagram of the dark field illumination solution provided in this embodiment 1.

[0076] In this embodiment, the light beam emitted by the dark field illumination light source 300 passes through the deflection prism 310 and then sequentially passes through the first lens group 311, the aperture element (not shown), the polarizer 312, and the second lens group 313, and is imaged onto the surface of the wafer under test in a critical illumination manner. The first lens group 311 and the second lens group 313 constitute a coupling lens group 320.

[0077] It is understandable that in practice, the above optical path may be adjusted according to application requirements. For example, the deflection prism 310 and the polarizer may be omitted.

[0078] It can be understood that the coupling lens group provided in this embodiment is equivalent to a condenser, which can make the image of the light source coincide with the object plane of the wafer surface, that is, the light source is imaged on the object after passing through the condenser, which makes it easy to obtain a narrow and strong illumination beam, and is also beneficial to reduce the shadow and reflection of the illumination.

[0079] It can be understood that in transmitted illumination, to fully utilize the aperture angle of the imaging objective lens, the coupling lens assembly and objective lens 200 have the same or slightly larger numerical aperture, and the aperture element has a preset opening size that satisfies C′×W′, where C′=C / MI, W′=W×cos(θ) / MI, C is the length of the dark-field illumination spot, MI is the magnification of the dark-field illumination light path, W is the width of the dark-field illumination spot, and θ is the angle between the illumination light and the normal of the wafer under test. It should be noted that because the aperture element serves to constrain the size of the illumination spot, it is not necessary to strictly set the size of the light-emitting surface of the dark-field illumination light source. It is sufficient to configure the size of the aperture element. This will also ensure that the light beam meets the distribution requirements of the dark-field illumination spot on the surface of the wafer under test.

[0080] Of course, in some cases, the aperture element can be set as a variable aperture, which can arbitrarily change the aperture angle of the light beam entering the coupling lens group to match the numerical aperture of the objective lens 200, thereby achieving light beam shaping.

[0081] It should be noted that the dark-field illumination light source 300 is imaged onto the surface of the wafer under test after passing through the deflection prism 310, the first lens group 311, the aperture element, the polarizer 312, and the second lens group 313 (the above optical components are equivalent to the dark-field illumination lens group mentioned above). By designing the above optical components, it is possible to change the width, length, and light intensity of the light-emitting surface of the light source, shape the beam, and change the spatial position of the beam, thereby achieving the distribution requirements of the dark-field illumination spot.

[0082] It can be understood that the above-mentioned dark field illumination lens group is not limited to the above-mentioned optical components and optical structures. In practice, the optical components and structures can also be adjusted according to the application. As long as the purpose of this application is met, it is within the scope of protection of this application.

[0083] Furthermore, the length of the light emitting surface of the dark field illumination light source 300 is C′=C / MI, the width of the light emitting surface of the dark field illumination light source is W′=W×cos(θ) / MI, and the size of the light emitting surface of the dark field illumination light source is configured as C′×W′, wherein: C is the length of the dark field illumination spot, MI is the magnification of the dark field illumination light path, W is the width of the dark field illumination spot, θ is the angle between the illumination light and the normal of the wafer under test, and θ is 40-70 degrees.

[0084] Furthermore, the darkfield illumination light source employed in this application can also utilize a high-precision machined aperture element (slit) to strictly control the darkfield illumination spot size. The slit opening has dimensions of C' x W'. The slit is placed on the object plane of the darkfield illumination coupling lens assembly, conjugate with the illumination spot, and a highly uniform surface light source is placed behind the slit to provide illumination.

[0085] Please refer to Figure 5 and Figure 6 Since the incident plane is not perpendicular to the light spot, the optical path difference from the light source to different positions on the illumination spot is different. The stretching effect of the oblique incidence of single-sided illumination causes the light spot to be uneven in length. In order to ensure good uniformity in the length direction, a symmetrical critical illumination design is adopted, that is, there are two dark field illumination light sources 300, and the optical paths of the light beams emitted by the dark field illumination light sources 300 are symmetrically distributed. Moreover, the incident plane of the light beam emitted by the dark field illumination light source that is incident on the surface of the wafer to be measured is not perpendicular to the plane where the dark field illumination spot is located.

[0086] See also Figure 7 , is an optical schematic diagram of another dark field illumination solution provided in Example 1 of the present application.

[0087] and Figure 5 and Figure 6 The difference between the dark field illumination scheme provided is that the dark field illumination scheme provided in this embodiment adopts a single dark field illumination light source, which is arranged on one side of the optical center field of view. The incident plane of the light and the plane where the dark field illumination spot is located are non-perpendicular, that is, the incident plane of the light beam emitted by the dark field illumination light source is incident on the surface of the wafer to be measured through the dark field illumination optical path and is inclined to the plane where the dark field illumination spot is located. The dark field illumination optical path is parallel or coincident with the vertical plane of the optical center field of view. At this time, the optical path difference from the light source to each position on the illumination spot will be slightly different, but it has little effect on the illumination uniformity. It can be understood that the dark field illumination system adopts a single-sided critical illumination design at this time.

[0088] Furthermore, the length of the light emitting surface of the dark field illumination light source 300 is C′=C / MI, the width of the light emitting surface of the dark field illumination light source is W′=W×cos(θ) / MI, and the size of the light emitting surface of the dark field illumination light source is configured as C′×W′, wherein: C is the length of the dark field illumination spot, MI is the magnification of the dark field illumination light path, W is the width of the dark field illumination spot, θ is the angle between the illumination light and the normal of the wafer under test, and θ is 40-70 degrees.

[0089] The semiconductor wafer bright and dark field defect detection device provided in the above-mentioned embodiment of the present application is provided with multiple magnification objective lenses, which can be flexibly switched according to the requirements of detection accuracy, thereby realizing switching between high detection accuracy and low detection speed and low detection accuracy and high detection speed; and the dark field illumination beam is precisely configured at the dark field light source end so that the dark field illumination spot covers the dark field of view corresponding to the dark field detector under the required multiple objective lenses, and at the same time controls the dark field illumination spot area to avoid crosstalk with the bright field signal.

[0090] The wafer bright and dark field defect detection device provided in the above embodiments of the present application realizes simultaneous detection of bright and dark fields with a common optical path and separate fields of view, and can support switching of different magnifications of the same objective lens to synchronously change the imaging magnification, thereby realizing switching between high detection accuracy and low detection speed and low detection accuracy and high detection speed, thereby better meeting different application requirements.

[0091] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A wafer bright and dark field defect detection device, characterized in that: It includes a bright field illumination light source, an objective lens, a dark field illumination light source, a bright field detector and a dark field detector, wherein the multiple magnifications of the objective lens are switchable; The light beam emitted by the bright field illumination light source is irradiated onto the surface of the wafer to be measured through the objective lens, and the bright field signal light generated by the reflection passes through one side of the optical axis of the objective lens to form a bright field acquisition field which is captured by the bright field detector, and an image is formed to obtain a bright field image; The light beam emitted by the dark field illumination light source is irradiated onto the surface of the wafer to be measured, and the dark field signal light generated by scattering passes through the other side of the optical axis of the objective lens to form a dark field acquisition field that is captured by the dark field detector, and a dark field image is obtained by imaging; wherein: The distribution of the dark field illumination spot on the surface of the wafer under test is regulated by configuring the light-emitting surface of the dark field illumination light source so that the dark field illumination spot covers the dark field acquisition field of view corresponding to all magnifications of the objective lens and avoids crosstalk with the bright field acquisition field of view. The width, length and light intensity of the light-emitting surface of the dark field illumination light source are configured so that the light beam meets the distribution requirements of the dark field illumination spot on the surface of the wafer under test. The length of the light-emitting surface of the dark field illumination light source is C′=C / MI, the width of the light-emitting surface of the dark field illumination light source is W′=W×cos(θ) / MI, and the size of the light-emitting surface of the dark field illumination light source is configured to be C′×W′, wherein: C is the length of the dark field illumination spot, MI is the magnification of the dark field illumination light path through which the light beam emitted by the dark field illumination light source passes, W is the width of the dark field illumination spot, and θ is the angle between the illumination light and the normal of the wafer under test; The bright field image and the dark field image are collected simultaneously and used to obtain the bright field defect characteristics and the dark field defect characteristics of the surface of the wafer under test respectively through image processing.

2. The wafer bright and dark field defect detection device according to claim 1, characterized in that: The light beam emitted by the dark field illumination light source is imaged on the surface of the wafer to be measured through the dark field illumination optical path, and forms a narrow and long dark field illumination spot on the surface of the wafer to be measured; the dark field illumination optical path includes a first lens group, an aperture element and a second lens group arranged in sequence, the first lens and the second lens constitute a coupling lens group, and the aperture element is arranged on the object focal plane of the coupling lens group.

3. The wafer bright and dark field defect detection device according to claim 2, characterized in that: The coupling lens group and the objective lens have the same numerical aperture, the aperture element has a preset opening size and satisfies C′×W′, wherein C′=C / MI, W′=W×cos(θ) / MI, C is the length of the dark field illumination spot, MI is the magnification of the dark field illumination light path, W is the width of the dark field illumination spot, and θ is the angle between the illumination light and the normal of the wafer under test.

4. The wafer bright and dark field defect detection device according to claim 1, wherein: There are two dark field illumination light sources, and the dark field illumination light paths through which the light beams emitted by the two dark field illumination light sources pass are symmetrically distributed, and the illumination areas formed on the surface of the wafer to be measured are combined to produce the dark field illumination spot, and the incident plane of the light beam emitted by the dark field illumination light source incident on the surface of the wafer to be measured is not perpendicular to the plane where the dark field illumination spot is located.

5. The wafer bright and dark field defect detection device according to claim 1, characterized in that: There is one dark field illumination light source, and the incident plane of the light beam emitted by the dark field illumination light source incident on the surface of the wafer to be measured is inclined to the plane where the dark field illumination spot is located.

6. The wafer bright and dark field defect detection device according to claim 1, characterized in that: It also includes a spectroscopic element with two reflecting surfaces. The bright field signal light and dark field signal light generated on the surface of the wafer to be measured are respectively incident on the two reflecting surfaces of the spectroscopic element through a common imaging optical path. The two reflecting surfaces of the spectroscopic element reflect the bright field signal light and the dark field signal light to the bright field detector and the dark field detector respectively.

7. The wafer bright and dark field defect detection device according to claim 6, characterized in that: The bright field detector and the dark field detector are respectively a bright field camera and a dark field camera, the imaging planes of the bright field camera and the dark field camera are conjugate to the plane where the wafer to be measured is located, the field of view centers of the bright field camera and the dark field camera are symmetrically distributed with respect to the optical center field of view and are spaced apart by L from the optical center field of view; The common imaging optical path through which the bright field signal light and the dark field signal light pass is the lowest magnification M min The distance between the bright field acquisition field or the dark field acquisition field and the optical center field is L1=L / M. min ; The common imaging optical path through which the bright field signal light and the dark field signal light pass is the maximum magnification M max The distance between the bright field acquisition field and the dark field acquisition field and the optical center field is L2=L / M. max ; The target length of the bright field camera and the dark field camera is K, and the corresponding maximum length on the object side is K′=K / M min .

8. The wafer bright and dark field defect detection device according to claim 7, characterized in that: The distribution of the dark field illumination spot meets the following parameter requirements: The width of the dark field illumination spot W is the dark field acquisition field under all magnifications, and the width of the dark field illumination spot W=L2-L1=L / (M max -M min ); The distance between the illumination boundary of the dark field illumination spot and the optical center field of view is B=L / M min +a, a is the diffusion width of the dark field illumination spot; The dark field illumination spot length C=K′+b, where b is the range where the illumination spot is larger than the field of view required for imaging; The illumination uniformity of the dark field illumination spot in the spot width and the spot length is greater than 80%, and the illumination uniformity is the minimum illumination of the illumination spot divided by the maximum illumination value.

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