Wafer bright and dark field defect detection device

Abstract

According to the wafer bright and dark field defect detection device provided by the invention, the objective lenses with multiple multiplying powers are arranged, and the objective lenses can be flexibly switched according to the requirement of detection precision, so that switching between high detection precision and low detection speed and low detection precision and high detection speed is realized; and the dark field illumination light beam is accurately configured at the dark field light source end, so that the dark field illumination light spot covers the acquisition view field corresponding to the dark field detector under the required multiple objective lens multiplying power, and the crosstalk of the dark field acquisition view field and the dark field acquisition view field is avoided by effectively controlling the dark field illumination light 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, bright field inspection is an important inspection method in optical inspection. However, bright field inspection is limited by the diffraction limit, and the minimum inspection defect is only the radius of the Airy disk; while dark field inspection is based on Rayleigh scattering or Mie scattering of small-sized particles. As long as the scattering signal of small-sized defects can be detected, the detection sensitivity can be improved. Therefore, in order to improve the detection sensitivity of the detection device, a dark field detection device is usually configured in the bright field detection device to construct a bright and dark field detection device.

[0003] Usually, the intensity of bright field signal light is much greater than that of dark field signal light. Bright field signal light has great interference with dark field signal light, which reduces the accuracy of dark field detection. In order to solve the above problems, some solutions perform bright field and dark field detection on the samples under test respectively, and then perform data fusion. This method takes a long time. At the same time, vibration during the detection process will cause errors in the alignment of the two detections, reducing the detection accuracy. There are also some solutions that use different wavelengths of illumination light sources for bright and dark fields to distinguish between bright and dark field signal lights. The wafer under test responds differently to different illumination wavelengths, and the band-dividing solution 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: One of the purposes of the present application is to provide a wafer bright 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 multiple magnifications of the objective lens are switchable; The light beam emitted by the bright field illumination light source is irradiated to 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 acquired by the bright field detector, and a bright field image is obtained by imaging; 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 acquisition field formed by the scattered dark field signal light passing through the other side of the optical axis of the objective lens is acquired 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 to be measured 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 corresponding to all magnifications of the objective lens and avoids crosstalk to the bright field acquisition field; 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.

[0006] In some of the 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.

[0007] 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 under test, θ is 40-70 degrees, and the opening size of the aperture element is C′×W′.

[0008] In some embodiments, the light beam emitted by the dark field illumination light source is imaged on the surface of the wafer under test via a dark field illumination light path, and forms a narrow and long dark field illumination spot on the surface of the wafer under test; the dark field illumination light 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.

[0009] In some embodiments, the coupling lens group and the objective lens have the same or slightly larger numerical aperture, and 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 normal angle between the illumination light and the wafer under test.

[0010] 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 respectively are symmetrically distributed, and the illumination areas respectively formed on the surface of the wafer to be measured are combined to generate 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.

[0011] In some embodiments, there is one dark field illumination light source, and an incident plane where the light beam emitted by the dark field illumination light source is incident on the surface of the wafer to be measured is inclined with respect to a plane where the dark field illumination spot is located.

[0012] In some of the embodiments, a spectroscopic element having two reflective surfaces is further included. The bright field signal light and the 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 element 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.

[0013] 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 with the plane where the wafer under test 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 with respect to 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 Under the condition that the distance between the bright field acquisition field of view and the dark field acquisition field of view and the optical center 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 Under the condition that the distance between the bright field acquisition field of view and the dark field acquisition field of view and the optical center field of view 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 .

[0014] In some embodiments, the distribution of the dark field illumination spot meets the following parameter requirements: The width W of the dark field illumination spot is the dark field field under all magnifications, and the width 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, a is 0.1~0.5mm; The spot length of the dark field illumination spot is 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; 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.

[0015] This application adopts the above technical solution, and its beneficial effects are as follows: The wafer bright and dark field defect detection device provided by the present application is provided with a dark field illumination light source, and the distribution of the dark field illumination light spot in the dark field acquisition field of view is regulated by the dark field illumination light source, so that the dark field illumination light spot covers the dark field acquisition field of view corresponding to the objective lens at all magnifications, thereby solving the problem that the dark field acquisition field of view corresponding to the dark field detector changes when the objective lens is switched; at the same time, the dark field illumination light source is used to control the dark field illumination light spot area to avoid crosstalk with the bright field acquisition field of view. By accurately 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, thereby ensuring the dark field illumination requirements while improving the accuracy of dark field detection.

[0016] The wafer bright and dark field defect detection device provided in the present application realizes simultaneous detection of bright and dark field common optical path 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

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. 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 paying any creative work.

[0018] Figure 1 A schematic diagram of the structure of a semiconductor wafer bright and dark field defect detection device provided in Example 1 of the present application; Figure 2 A schematic diagram of a specific optical path provided in Example 1 of the present application; 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; Figure 4 This is a schematic diagram of the common light path field distribution of bright and dark fields provided in Example 1 of the present application; Figure 5 An optical schematic diagram of the dark field illumination solution provided in Example 1 of the present application; Figure 6 A detailed optical schematic diagram of the dark field illumination solution provided in Example 1 of the present application; Figure 7 An optical schematic diagram of another dark field illumination solution provided in Example 1 of the present application. DETAILED DESCRIPTION

[0019] Embodiments of the present application are described in detail below, and examples of the embodiments 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. In the description of the present 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 the present 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 the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined. In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0020] Example 1 See also Figure 1 , is a schematic diagram of the structure of the wafer bright and dark field defect detection device provided in Example 1 of the present application, including a bright field illumination light source 100, an objective lens 200, a dark field illumination light source 300, a bright field detector 400 and a dark field detector 500, and multiple magnifications of the objective lens 200 can be switched. The technical solution implemented is described in detail below.

[0021] The bright field illumination light source 100 is used to emit a bright field illumination light beam. The specific structure of the bright field illumination light source 100 is not limited, and it can be a single light source or multiple light sources. The light beam emitted by the bright field illumination light source 100 is split or combined to meet the light path requirements to ensure the flexibility of the entire system.

[0022] The objective lens 200 can be set to 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 view corresponding to the dark field detector will also change due to the change of the microscopic magnification of the imaging system.

[0023] In some embodiments, the objective lens 200 may be configured to include a plurality of objective lens combinations with different magnifications, such as Figure 1 The combination of objective lenses 1, ... and objective lenses n shown in the figure can switch objective lenses of corresponding magnifications into the optical path according to the actual requirements of detection accuracy.

[0024] In some embodiments, the objective lens 200 may also be configured to include a single objective lens and an objective lens converter. The objective lens converter may switch the objective lens to different magnifications, and the objective lens of the corresponding magnification may be switched into the optical path according to actual detection accuracy requirements.

[0025] 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 it can be a single light source or multiple light sources. The light beam emitted by the dark field illumination light source 300 is split or combined to meet the light path requirements to ensure the flexibility of the entire system.

[0026] 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 according to needs; 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 detection needs.

[0027] 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.

[0028] 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.

[0029] 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: The light beam emitted by the bright field illumination light source 100 is irradiated onto the surface of the wafer under test through the objective lens 200, and the bright field signal light generated by reflection passes through one side of the optical axis of the objective lens 200 to form a bright field acquisition field that is acquired 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 under test, and the dark field signal light generated by scattering passes through the other side of the optical axis of the objective lens 200 to form a dark field acquisition field that is acquired by the dark field detector 500, and a dark field image is obtained by imaging. 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 300, so that the dark field illumination spot covers the dark field acquisition field of view corresponding to the objective lens 200 at all magnifications and avoids crosstalk with the bright field acquisition field of view; in addition, the bright field image and the dark field image are collected simultaneously, and are 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.

[0030] It should be pointed out that the dark field illumination spot needs to be larger than the dark field acquisition field of view, so as to ensure the imaging uniformity of the acquisition field of view. Of course, the bright field imaging spot also needs to be larger than the bright field acquisition field of view.

[0031] The wafer bright and dark field defect detection device provided in the present 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.

[0032] In some embodiments, the light beam meets the distribution requirements of the dark field illumination light spot by setting the width, length, and light intensity of the light emitting surface of the dark field illumination light source 300. For example, the light path design can be used to make the light beam emitted by the dark field illumination light source 300 meet the distribution requirements of the dark field illumination light spot after being magnified by the dark field illumination lens group, so as to ensure that the dark field illumination light 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 light spot area to avoid crosstalk with the bright field signal.

[0033] See also Figure 2 , which is a schematic diagram of a specific optical path provided in Example 1 of the present application, including: a bright field illumination light source 100, a reflector 10, a beam splitter 20, a dichroic mirror 30, an imaging lens group 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 beam splitter assembly 600. The specific optical path is as follows: The light beam emitted by the bright field illumination light source 100 is sequentially irradiated to the surface of the wafer under test through the reflector 10, the beam splitter 20, the dichroic mirror 30 and 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, and then passes through the dichroic mirror 30 and the imaging lens group 40. The bright field acquisition field formed by the beam splitter component 600 is acquired by the bright field detector 400, and a bright field image is obtained by imaging.

[0034] The light beam emitted by the dark field illumination light source 300 irradiates 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 200, and then passes through the dichroic mirror 30 and the imaging lens group 40, and then the dark field acquisition field formed by the light splitting component 600 is acquired by the dark field detector 500, and a dark field image is obtained by imaging.

[0035] In this embodiment, the spectroscopic component 600 is a spectroscopic prism or a multi-faceted reflector. The spectroscopic prism can be a right-angle isosceles prism, and the multi-faceted 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.

[0036] It can be understood that the main optical path provided in the above-mentioned embodiment of the present application utilizes a spectroscopic component 600 having two reflective surfaces. The bright field signal light and the 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.

[0037] Furthermore, the center of the light splitting component 600 coincides with the optical axis, and the two relatively narrow fields of view outside the optical axis are reflected to the target surfaces of the bright field camera and the dark field camera respectively. Both the bright field camera and the dark field camera use line scan cameras, and the scanning dimension field of the line scan camera is very small. Therefore, the two narrow fields of view distributed by the light splitting component provided in this application meet the field of view width of the scanning dimension, and do not split in the direction perpendicular to the schematic diagram, so as to meet all the field of view requirements in the length direction of the target surface of the line scan camera.

[0038] 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.

[0039] 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.

[0040] 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 field and dark field field acquisition positions will be changed from solid lines (such as Figure 3 If there are multiple magnifications, 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 M min In this case, 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 In this case, 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 .

[0041] Please refer to Figure 4, within 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 prior art, 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 line 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; and the dark field field of view provided by the present application needs to be based on the requirements of the optical system for simultaneous detection of bright and dark fields, and 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: The spot width W of the dark field illumination spot covers the dark field field at all magnifications. The spot width 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, 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.

[0042] 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.

[0043] 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.

[0044] 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 detectors 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.

[0045] See also Figure 5 , which is an optical schematic diagram of the dark field illumination scheme provided in Example 1 of the present application.

[0046] In this embodiment, in order to ensure the uniformity of illumination, the dark field illumination scheme provided in this embodiment adopts 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 to be measured through the corresponding dark field illumination light path, 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, and are symmetrical 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 tilt angle, and the two illumination beams overlap on the wafer surface and the overlapping area constitutes a dark field illumination spot. It can be understood that for the surface light source with better uniformity to be projected and imaged at the required illumination position on the surface of the wafer to be measured, the illumination device needs to reach the imaging level to ensure a clear dark field illumination contour.

[0047] In this embodiment, 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 light path, and forms a narrow dark field illumination spot on the surface of the wafer to be measured. The dark field illumination light path adopts a critical illumination method, that is, the light beam emitted by the dark field illumination light source is imaged on the wafer surface after passing through the illumination lens group. This illumination method can form a narrow and strong illumination feature on the wafer surface. At this time, the uniform light source imaging is projected on the area corresponding to multiple magnifications of the dark field. Of course, in some cases, by adjusting the lens group structure of the dark field illumination light path, it can also be changed to a Kohler illumination method, which can easily obtain a dark field illumination spot with better uniformity.

[0048] See also Figure 6 , which is a detailed optical schematic diagram of the dark field illumination solution provided in this embodiment 1.

[0049] 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 to be imaged onto the surface of the wafer to be measured in a critical illumination manner. The first lens group 311 and the second lens group 313 constitute a coupling lens group 320.

[0050] It can be understood that in practice, the above optical path can be adjusted according to application requirements, for example, the deflection prism 310 and the polarizer can be omitted.

[0051] 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.

[0052] It can be understood that in transmitted illumination, in order to make full use of the aperture angle of the imaging objective lens, the coupling lens group and the objective lens 200 have the same or slightly larger numerical aperture, and the aperture element has a preset opening size and 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 normal angle between the illumination light and the wafer under test. It should be noted that since the aperture element plays a role in constraining 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 at this time. It is only necessary to configure the size of the aperture element, which can also make the light beam meet the distribution requirements of the dark field illumination spot on the surface of the wafer under test.

[0053] Of course, in some cases, the aperture element can be set as a variable aperture, and the aperture angle of the light beam entering the coupling lens group can be arbitrarily changed to match the numerical aperture of the objective lens 200, thereby achieving light beam shaping.

[0054] It should be noted that the dark field illumination light source 300 is imaged onto the surface of the wafer to be measured 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 source's luminous surface, shape the light beam and change the spatial position of the light beam, thereby achieving the distribution requirements of the dark field illumination spot.

[0055] It can be understood that the above-mentioned dark field illumination lens group is not limited to the above-mentioned optical components and their optical structures. In practice, the optical components and structures can be adjusted according to the application. As long as the purpose of this application is met, it is within the protection scope of this application.

[0056] 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.

[0057] Furthermore, the dark field illumination light source used in the present application can also be processed by high-precision aperture elements (slits) in order to strictly control the size of the dark field illumination spot, and the slit opening size is C'×W'. The slit is placed on the object plane of the dark field illumination coupling lens group, conjugate with the illumination spot, and a high uniform surface light source is placed behind the slit to provide illumination.

[0058] Please refer to Figure 5 and Figure 6 Since the incident plane is not perpendicular to the light spot, at this time, the optical path difference from the light source to different positions on the illumination light spot is different, and the stretching effect of the single-sided oblique 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 path of the light beam emitted by the dark field illumination light source 300 is symmetrically distributed, 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 light spot is located.

[0059] See also Figure 7 , is an optical schematic diagram of another dark field illumination scheme provided in Example 1 of the present application.

[0060] 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, and the incident plane of the light is non-perpendicular to the plane where the dark field illumination spot is located, 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 light path and is inclined to the plane where the dark field illumination spot is located, and the dark field illumination light 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.

[0061] 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.

[0062] The semiconductor wafer bright and dark field defect detection device provided in the above-mentioned embodiments of the present application is provided with objective lenses with multiple magnifications, and these objective lenses can be flexibly switched according to the requirements of detection accuracy, so as to achieve switching between high detection accuracy and low detection speed and low detection accuracy and high detection speed; and the dark field illumination beam is accurately 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, the dark field illumination spot area is controlled to avoid crosstalk with the bright field signal.

[0063] The wafer bright and dark field defect detection device provided in the above-mentioned embodiments of the present application realizes simultaneous detection of bright and dark field common optical path 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.

[0064] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in 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 to the surface of the wafer to be measured through the objective lens, and the bright field acquisition field formed by the reflected bright field signal light passing through one side of the optical axis of the objective lens is acquired by the bright field detector, and a bright field image is obtained by imaging; 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 acquisition field formed by the scattered dark field signal light passing through the other side of the optical axis of the objective lens is acquired 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 to be measured 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 corresponding to all magnifications of the objective lens and avoids crosstalk with the bright field acquisition field; 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 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 on the surface of the wafer to be measured.

3. The wafer bright and dark field defect detection device according to claim 2, characterized in that: 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, and θ is the normal angle between the illumination light and the wafer under test.

4. 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 under test via the dark field illumination light path, and forms a narrow and long dark field illumination spot on the surface of the wafer under test; the dark field illumination light 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.

5. The wafer bright and dark field defect detection device according to claim 4, characterized in that: The coupling lens group and the objective lens have the same or slightly larger numerical aperture, and 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 normal angle between the illumination light and the wafer under test.

6. The wafer bright and dark field defect detection device according to claim 1, characterized in that: 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 respectively are symmetrically distributed, and the illumination areas respectively formed on the surface of the wafer to be measured are combined to generate 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.

7. 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 where the light beam emitted by the dark field illumination light source is incident on the surface of the wafer to be measured is inclined with respect to the plane where the dark field illumination light spot is located.

8. The wafer bright and dark field defect detection device according to claim 1, characterized in that: It also includes a spectroscopic element with two reflective surfaces. The bright field signal light and the 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 element 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.

9. The wafer bright and dark field defect detection device according to claim 8, 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 with 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 with respect to 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 of view or the dark field acquisition field of view and the optical center 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 Under the condition that the distance between the bright field acquisition field of view and the dark field acquisition field of view and the optical center field of view 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 .

10. The wafer bright and dark field defect detection device according to claim 9, characterized in that: The distribution of the dark field illumination spot meets the following parameter requirements: The width W of the dark field illumination spot is the dark field acquisition field of view covering all magnifications, and the width W of the dark field illumination spot is 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 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; 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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