Wafer defect detection device and control method

Abstract

According to the wafer defect detection device and the control method provided by the invention, by adjusting the position of the bright field detector and / or the dark field detector, the corresponding view field change under the change of the imaging magnification is accurately matched, so that the requirements of dark field imaging and bright field imaging on the view field integrity can be met while the adjustable detection precision is realized, and the wafer defect detection efficiency is improved. The purpose of covering the bright and dark field imaging view field under any objective lens magnification is achieved, and the imaging effect and the detection accuracy are improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor detection technology, and in particular to a wafer defect detection device and a control method. 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] The intensity of the bright field signal light is much greater than that of the dark field signal light. The bright field signal light has a great interference with the dark field signal light, which reduces the dark field detection accuracy. In order to solve the above problems, some solutions perform bright field and dark field detection on the sample 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 defect detection device and a control method to improve the detection accuracy of semiconductor wafers.

[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 semiconductor wafer bright and dark field defect detection device, comprising a first illumination light source, an objective lens, a second illumination light source, a bright field detector and a dark field detector, wherein the magnification of the objective lens is switchable, and the position of the bright field detector and / or the dark field detector is adjustable; The light beam emitted by the first 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 acquired by the bright field detector, and a bright field image is obtained by imaging; The light beam emitted by the second 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 which is acquired by the dark field detector, and a dark field image is obtained by imaging; wherein: By adjusting the position of the dark field detector so that the target surface of the dark field detector covers the dark field acquisition field corresponding to any magnification of the objective lens, and / or adjusting the position of the bright field detector so that the target surface of the bright field detector covers the bright field acquisition field corresponding to any magnification of the objective lens, and avoiding the mutual crosstalk between the dark field acquisition field and the bright field acquisition field caused by the change of the illumination spot position; 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 embodiments, the bright field detector and the dark field detector are respectively a bright field camera and a dark field camera, the target surfaces of each of the bright field camera and the dark field camera are conjugate with the plane where the wafer to be measured is located, and the field of view center of the bright field camera and the field of view center of the dark field camera have a preset eccentricity relative to the optical center field of view.

[0007] In some embodiments, the off-axis amount L of the dark field camera, the magnification M of the objective lens, and the position l of the dark field illumination spot relative to the optical center field of view are related as follows: l=L / M.

[0008] In some embodiments, when the magnification of the objective lens is switched to M1, and the dark field illumination spot is fixedly configured at a position l relative to the optical center field of view, the target surface of the dark field camera needs to be moved to a position corresponding to the off-axis amount and satisfy L1= l ×M1.

[0009] In some embodiments, if the target length of the dark field camera is K, the maximum imaging field of view is the field length K′=K / Mmin of the objective lens at the minimum magnification, and the length of the dark field illumination spot must satisfy C=K′+b, where b is the range in which the dark field illumination spot is larger than the field of view required for imaging, and b is 1~5mm.

[0010] In some of the embodiments, a driving device is further included, and the driving device is used to adjust the position of the bright field detector and / or the dark field detector on the imaging plane.

[0011] In some embodiments, there are two second illumination light sources, the light paths of the light beams emitted by the second illumination light sources are symmetrically distributed, and the incident plane of the light beams emitted by the second illumination light sources that are incident on the surface of the wafer to be measured after passing through the dark field illumination light path is not perpendicular to the plane where the dark field illumination spot is located.

[0012] In some embodiments, there is one second illumination light source, and the incident plane of the light beam emitted by the second illumination light source and incident on the surface of the wafer under test after passing through the dark field illumination light path is inclined to the plane where the dark field illumination spot is located.

[0013] In some embodiments, a spectroscopic element is further included. The bright field signal light and the dark field signal light after passing through the objective lens are incident on the spectroscopic element. The spectroscopic element separates the bright field signal light and the dark field signal light and reflects them to the bright field detector and the dark field detector respectively.

[0014] The second object of the present application is to provide a control method, which is applied to any one of the wafer defect detection devices, and the control method comprises the following steps: Switch the magnification of the objective lens; The position of the dark field detector is adjusted so that the target surface of the dark field detector covers the corresponding dark field acquisition field of view at any magnification of the objective lens, and / or the position of the bright field detector is adjusted so that the target surface of the bright field detector covers the corresponding bright field acquisition field of view at any magnification of the objective lens, thereby avoiding mutual crosstalk between the dark field acquisition field of view and the bright field acquisition field of view caused by changes in the position of the illumination spot.

[0015] In some of the embodiments, when the magnification of the objective lens is switched to M1 and the position l of the dark field illumination spot relative to the optical center field of view is fixed, the eccentricity L1=l×M1 of the dark field camera relative to the optical center field of view is calculated, and the target surface of the dark field camera is moved to the position corresponding to L1.

[0016] In some embodiments, if the target length of the dark field camera is K, the maximum imaging field of view is the field length K′=K / Mmin of the objective lens at the minimum magnification, and the length of the dark field illumination spot is configured to be C=K′+b, where b is the range in which the dark field illumination spot is larger than the field of view required for imaging, and b is 1~5mm.

[0017] This application adopts the above technical solution, and its beneficial effects are as follows: The wafer defect detection device and control method provided by the present application can accurately match the corresponding field of view changes under the imaging magnification change by adjusting the position of the bright field detector and / or the dark field detector, and can achieve adjustable detection accuracy while meeting the requirements of dark field imaging and bright field imaging for field of view integrity, so as to achieve the purpose of covering the field of view of bright and dark field imaging under any imaging magnification, thereby improving the detection accuracy. In addition, since the device does not need to adjust the position of the illumination spot, the possible mutual interference of bright and dark field imaging caused by the change of the illumination spot position is avoided.

[0018] The semiconductor wafer bright and dark field defect detection device and control method provided by the present application realize 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; at the same time, while realizing simultaneous detection of bright and dark fields with a common optical path and separate fields of view, the free configuration of various detection accuracy and detection modes is supported through switching of imaging magnifications and matching of imaging fields of view in response to the diverse requirements of different detection objects in terms of accuracy and speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] 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 the installation position of the camera target surface on the image side provided in Example 1 of the present application; Figure 3 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 4 This is a step flow chart of the semiconductor wafer bright and dark field defect detection method provided in Example 2 of the present application. DETAILED DESCRIPTION

[0021] 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.

[0022] Example 1 See also Figure 1 , is a schematic diagram of the structure of the semiconductor wafer bright and dark field defect detection device provided in Example 1 of the present application, including a first illumination light source 100, an objective lens 200, a second illumination light source 300, a bright field detector 400 and a dark field detector 500, and the magnification of the objective lens 200 can be switched. The technical solution implemented is described in detail below.

[0023] The first illumination light source 100 is used to emit a bright field illumination light beam. The specific structure of the first 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 first illumination light source 100 is split or combined to meet the light path requirements to ensure the flexibility of the entire system.

[0024] 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.

[0025] In some embodiments, the objective lens 200 can be configured to include a combination of multiple objective lenses with different magnifications, that is, a combination of objective lenses 1, ... and objective lenses n, and objective lenses of corresponding magnifications can be switched into the optical path according to actual detection accuracy requirements.

[0026] 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.

[0027] It can be understood that by setting an objective lens with switchable magnification in the optical path, simultaneous detection of bright and dark fields on the same optical path can be achieved, and switching of different magnifications of the same objective lens can be supported to synchronously change the imaging magnification, thereby achieving switching between high detection accuracy and low detection speed and low detection accuracy and high detection speed, to better meet different application requirements; at the same time, while achieving simultaneous detection of bright and dark fields on the same optical path and separate fields, the switching of imaging magnifications and matching of imaging fields of view support the free configuration of multiple detection accuracies and detection modes in response to the diverse requirements of different detection objects in terms of accuracy and speed.

[0028] The second illumination light source 300 is used to emit a dark field illumination light beam. The specific structure of the second illumination light source 300 is not limited, and can be a single light source or multiple light sources. The light beam emitted by the second illumination light source 300 is split or combined to meet the light path requirements to ensure the flexibility of the entire system.

[0029] In this embodiment, the second 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 second illumination light source 300 can be appropriately configured according to needs; or the light beam of the second illumination light source 300 can be shaped; or the light beam position of the second illumination light source 300 can be adjusted to meet detection needs.

[0030] The bright field detector 400 and the dark field detector 500 are used to obtain the imaging signal of the first illumination light source and the imaging signal of the second illumination light source respectively. The position of the bright field detector 400 and / or the dark field detector 500 is adjustable.

[0031] Furthermore, a driving device (not shown) is included, and the driving device is used to adjust the position of the bright field detector 400 and / or the dark field detector 500 on the imaging plane.

[0032] The working method of the wafer defect detection device provided in the above embodiment of the present application is as follows: The light beam emitted by the first illumination light source 100 is irradiated to the surface of the wafer to be measured through the objective lens 200, and 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 which is acquired by the bright field detector 400, and a bright field image is obtained by imaging; The light beam emitted by the second 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 to form a dark field acquisition field of view which is acquired by the dark field detector 500, and a dark field image is obtained by imaging; wherein: By adjusting the position of the dark field detector 500 so that the target surface of the dark field detector 500 covers the corresponding dark field acquisition field of view at any magnification of the objective lens 200, and / or adjusting the position of the bright field detector 400 so that the target surface of the bright field detector 400 covers the corresponding bright field acquisition field of view at any magnification of the objective lens 200, crosstalk between the dark field acquisition field of view and the bright field acquisition field of view caused by changes in the position of the illumination spot can be avoided.

[0033] 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.

[0034] The wafer defect detection device provided in the present embodiment is provided with objective lenses of multiple magnifications, and these objective lenses can be flexibly switched according to the requirements of detection accuracy. After the objective lenses are 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, which may cause some unexpected situations, such as the dark field illumination spot is too small to cover the entire 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 does not adjust the illumination spot to avoid mutual interference of light beams caused by illumination changes. By adjusting the position of the dark field detector 500 and / or adjusting the position of the bright field detector 400, the dark field illumination spot and the bright field illumination spot cover the corresponding dark field acquisition field of view and bright field acquisition field of view at any magnification of the objective lens 200, and avoid crosstalk between the dark field acquisition field of view and the bright field acquisition field of view, so as to achieve adjustable detection accuracy while meeting the requirements of dark field imaging and bright field imaging for field of view integrity, thereby achieving the purpose of covering the bright and dark field imaging fields of view at multiple imaging magnifications and improving detection accuracy.

[0035] Please refer to Figure 1 The semiconductor wafer bright and dark field defect detection device provided in Example 1 of the present application further includes: a reflector 10, a beam splitter 20, a dichroic mirror 30, an imaging lens group 40, a focus detection component 50 and a beam splitter element 600. The specific optical path is as follows: The light beam emitted by the first 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 the objective lens 200, the dichroic mirror 30 and the imaging lens group 40, and then the bright field field formed by the beam splitter element 600 is acquired by the bright field detector 400, and a bright field image is obtained by imaging.

[0036] The light beam emitted by the second 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 objective lens 200, the dichroic mirror 30 and the imaging lens group 40, and then the dark field field formed by the beam splitter 600 is acquired by the dark field detector 500, and a dark field image is obtained by imaging.

[0037] In this embodiment, the spectroscopic element 600 can be a spectroscopic prism or an isosceles right-angle reflector. For example, the symmetry axis of the isosceles right-angle reflector coincides with the optical axis, and the two right-angle faces are reflectors. The reflectors reflect two relatively narrow fields of view outside the optical axis to the target surfaces of the bright field detector 400 and the dark field detector 500 respectively; or the multi-faceted reflector is an isosceles trapezoidal structure, the symmetry axis of the isosceles trapezoid coincides with the optical axis, and the hypotenuse of the trapezoid is the reflective surface.

[0038] It can be understood that the main optical path of this embodiment is a detection device that shares the optical path of bright field imaging and dark field imaging, which corresponds to different imaging fields of view respectively. The bright field signal light and the dark field signal light are separated by a spectroscopic element 600. The bright field and dark field signals are respectively irradiated to the non-coplanar mirrors of the multi-faceted reflector and enter the corresponding detectors after reflection. Compared with the wavelength spectroscopic or intensity spectroscopic scheme, the use of multi-faceted reflector spectroscopic does not lose signal light energy and can support a wide spectrum band, has higher sensitivity, but reduces the single imaging field of view.

[0039] Furthermore, the bright field detector 400 and the dark field detector 500 are respectively a bright field camera and a dark field camera. Both the bright field camera and the dark field camera adopt line scanning cameras. Line scanning cameras have better photoelectric conversion efficiency and sampling speed. The two narrow fields of view divided by the multi-faceted reflector meet the field of view width of the scanning dimension, and do not split light in the direction perpendicular to the schematic diagram, meeting all field of view requirements in the length direction of the target surface of the line scanning camera.

[0040] See also Figure 2 , is a schematic diagram of the installation position of the camera target surface on the image side provided in this embodiment 1.

[0041] In the present embodiment, the target surfaces of the bright field camera and the dark field camera are each in a conjugate relationship with the plane where the wafer to be measured is located, the field center of the bright field camera and the field center of the dark field camera have a preset eccentricity relative to the optical center field of view, and the conjugate position of the bright field camera and the dark field camera is related to the magnification of the optical system. The present invention adopts a method of changing the magnification by switching the objective lens, that is, when switching to another magnification objective lens, the spot position of the bright field and the dark field remains unchanged, but the imaging position on the camera target surface will change. If there are multiple magnifications, there will be multiple positions of the bright field and the dark field on the camera target surface. In order to enable the camera target surface to cover the bright and dark field acquisition fields of view, it is necessary to adjust the position of the camera target surface to achieve the effect of field of view adaptation.

[0042] 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 collection positions will change; if there are multiple magnifications, there will be multiple collection 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 minimum magnification M min In this case, the distance between the bright field and the dark field and the central 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 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 .

[0043] Please refer to Figure 4 In the optical imaging field of view, the bright field camera and the dark field camera are symmetrically distributed around the central field of view (optical axis), but 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 of the present application is based on the optical system requirements for simultaneous detection of bright and dark fields, and the position of the dark field illumination spot relative to the central field of view remains unchanged, but the imaging point on the camera target surface will follow the different magnifications, and will have a precise position, and the illumination spot will always be kept completely overlapped with the dark field imaging field of view to achieve precise matching.

[0044] Specifically, this embodiment takes dark field illumination and imaging as an example. After the objective lens 200 switches the magnification, the position of the dark field illumination light in the camera imaging field of view follows the displacement. The theoretical displacement is determined according to the eccentricity L set by the dark field camera and the magnification M of the objective lens. L=l×M, l is the position of the dark field illumination spot relative to the central field of view. When the dark field illumination light path is not adjusted, l is a fixed value, so the imaging magnification M will determine the eccentricity L of the dark field camera.

[0045] In this embodiment, the position of the dark-field camera is adapted to the change of the eccentricity L by moving the position of the dark-field camera, so that the target surface of the dark-field camera can always cover the dark-field imaging field of view. For example, when the imaging magnification of the objective lens is switched to M1, and the position l of the dark-field illumination spot relative to the optical center field of view is fixed, the target surface of the dark-field camera needs to be moved to the position corresponding to the eccentricity, and L1=l×M1 is satisfied. For example, under the imaging magnification M2, the dark-field camera needs to be moved to L2=l×M2. According to this method, the positions L1, L2, ...L of the dark-field camera under other imaging magnifications are calibrated respectively. n It can be understood that by adjusting the position of the dark field camera to control the distribution of the dark field illumination spot in the dark field view, the dark field illumination spot covers the corresponding dark field view at all magnifications, and the imaging accuracy is improved through precise matching, solving the problem of dark field imaging field change, while avoiding interference with bright field imaging.

[0046] Furthermore, the length of the dark field illumination spot does not need to follow the change of imaging magnification, as long as the maximum field of view can be covered. If the target length of the dark field camera is K, the maximum extent of the corresponding imaging field of view, that is, the maximum imaging field of the objective lens 200 is the field length K′=K / Mmin at the minimum magnification. The length of the dark field illumination spot must satisfy C=K′+b, where b is the range of the dark field illumination spot larger than the field of view required for imaging. Usually, in order to reduce the engineering difficulty, some redundancy is discharged. In this embodiment, b=1~5mm is preferred.

[0047] Similarly, the change of the eccentricity L can be adapted by moving the position of the brightfield camera, so that the target surface of the brightfield camera can always cover the brightfield imaging field of view. For example, when the imaging magnification of the objective lens is switched to M1, and the position l' of the brightfield illumination spot relative to the optical center field of view is fixed, the target surface of the brightfield camera needs to be moved to the position corresponding to the eccentricity, and satisfy L1=l'×M1. For example, under the imaging magnification M2, the darkfield camera needs to be moved to L2=l'×M2. According to this method, the positions of the brightfield cameras at other imaging magnifications L1, L2, ... L n .

[0048] It should be noted that the above method of adjusting the position of the bright field camera to match the bright field imaging field of view can be used to adjust the position of the dark field camera to match the dark field imaging field of view. The effect can be referred to the dark field method, which will not be repeated here.

[0049] In some embodiments, 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 incident plane of the light beam emitted by the second illumination light source 300 incident on the surface of the wafer to be measured is not perpendicular to the plane where the dark field illumination spot is located, and the surface light source with better uniformity is 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 that the dark field illumination contour is clear; in addition, the dark field illumination optical path adopts a critical illumination method, that is, the light beam emitted by the second illumination light source 300 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, the light source beam can also be irradiated on the surface of the wafer to be measured in the manner of Kohler illumination by changing the lens group structure of the dark field illumination optical path.

[0050] It should be noted that: 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 spot is different, and the stretching effect of the single-sided illumination oblique incidence causes the light spot to be uneven in length. In order to ensure good uniformity in the length direction, a symmetrical lighting design is adopted, that is, there are two second illumination light sources 300, and the optical path of the light beam emitted by the second illumination light source 300 is symmetrically distributed, and the incident plane of the light beam emitted by the second 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.

[0051] In other embodiments, a single dark field illumination light source may be provided, in which a single dark field illumination light source is disposed 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 to or coincides 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 will have little effect on the illumination uniformity. It can be understood that at this time, the dark field illumination system adopts a single-sided critical illumination design.

[0052] In this embodiment, a motion platform (not shown) is further included, on which the wafer to be measured is carried. The motion platform is driven by a driving device to move so as to adjust the position of the bright field detector 400 and / or the dark field detector 500 on the imaging plane.

[0053] The wafer defect detection device provided in the above-mentioned embodiment of the present application can adjust the position of the bright field detector and / or the dark field detector to accurately match the corresponding field of view changes under the change of imaging magnification, thereby achieving adjustable detection accuracy while meeting the requirements of dark field imaging and bright field imaging for field of view integrity, thereby achieving the purpose of covering the bright and dark field imaging fields under multiple imaging magnifications, improving imaging accuracy through precise matching, solving the problem of dark field imaging field of view changes, avoiding interference with bright field imaging, and improving detection accuracy; at the same time, while realizing simultaneous detection of bright and dark field common optical paths and separate fields of view, the switching of imaging magnifications and matching of imaging fields of view support the free configuration of multiple detection accuracies and detection modes in response to the diverse requirements of different detection objects in terms of accuracy and speed.

[0054] Example 2 See also Figure 4 , which is a flow chart of the steps of the control method of the wafer defect detection device provided in Embodiment 2 of the present application, is applied to the wafer defect detection device provided in any of the above embodiments, and includes the following steps: Step S410: Switching the magnification of the objective lens 200.

[0055] Step S420: Adjust the position of the dark field detector 500 so that the target surface of the dark field detector 500 covers the corresponding dark field acquisition field of view at any magnification of the objective lens 200, and / or adjust the position of the bright field detector 400 so that the target surface of the bright field detector 400 covers the corresponding bright field acquisition field of view at any magnification of the objective lens 200, thereby avoiding crosstalk between the dark field acquisition field of view and the bright field acquisition field of view caused by changes in the position of the illumination spot.

[0056] Specifically, this embodiment takes dark field illumination and imaging as an example. After the objective lens 200 switches the magnification, the position of the dark field illumination light in the camera imaging field of view follows the displacement. The theoretical displacement is determined according to the eccentricity L set by the dark field camera and the magnification M of the objective lens. L=l×M, l is the position of the dark field illumination spot relative to the center field of view. When the dark field illumination light path is not adjusted, l It is a fixed value, so the imaging magnification M will determine the off-axis amount L of the dark field camera.

[0057] In this embodiment, the position of the dark-field camera is adapted to the change of the eccentricity L by moving the position of the dark-field camera, so that the target surface of the dark-field camera can always cover the dark-field imaging field of view. For example, when the imaging magnification of the objective lens 200 is switched to M1, the target surface of the dark-field camera needs to be moved to the position corresponding to the eccentricity and satisfying L1=l×M1. For example, under the imaging magnification M2, the dark-field camera needs to be moved to L2=l×M2. According to this method, the positions L1, L2, ... L of the dark-field camera under other imaging magnifications are calibrated respectively. n .

[0058] It can be understood that by adjusting the position of the dark field camera to control the distribution of the dark field illumination spot in the dark field of view, the dark field illumination spot can cover the corresponding dark field of view at all magnifications, thereby improving the imaging accuracy through precise matching, solving the problem of changes in the dark field imaging field of view, and avoiding interference with the bright field imaging.

[0059] Furthermore, the length of the dark field illumination spot does not need to follow the change of imaging magnification, as long as the maximum field of view can be covered. If the target length of the dark field camera is K, the maximum extent of the corresponding imaging field of view, that is, the maximum imaging field of the objective lens 200 is the field length K′=K / Mmin at the minimum magnification. The length of the dark field illumination spot must satisfy C=K′+b, where b is the range of the dark field illumination spot larger than the field of view required for imaging. Usually, in order to reduce the engineering difficulty, some redundancy is discharged. In this embodiment, b=1~5mm is preferred.

[0060] Similarly, the change of the eccentricity L can be adapted by moving the position of the bright field camera, so that the target surface of the bright field camera can always cover the bright field imaging field of view. For example, when the imaging magnification of the objective lens is switched to M1, and the position l' of the bright field illumination spot relative to the optical center field of view is fixed, the target surface of the bright field camera needs to be moved to the position corresponding to the eccentricity and satisfy L1=l'×M1. For example, under the imaging magnification M2, the dark field camera needs to be moved to L2=l'×M2. According to this method, the positions of the bright field cameras at other imaging magnifications L1, L2, ... L n .

[0061] It should be noted that the above method of adjusting the position of the bright field camera to match the bright field imaging field of view can be used to adjust the position of the dark field camera to match the dark field imaging field of view. The effect can be referred to the dark field method, which will not be repeated here.

[0062] In some embodiments, to ensure the uniformity of illumination, the dark field illumination scheme provided in this embodiment adopts external oblique incident illumination, that is, the incident plane of the light beam emitted by the second illumination light source 300 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. The surface light source with good uniformity is 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. In addition, the dark field illumination optical path adopts a critical illumination method, that is, the light beam emitted by the second illumination light source 300 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.

[0063] It should be noted that: 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 spot is different, and the stretching effect of the single-sided illumination oblique incidence 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 second illumination light sources 300, and the optical path of the light beam emitted by the second illumination light source 300 is symmetrically distributed, and the incident plane of the light beam emitted by the second 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.

[0064] The control method of the wafer defect detection device provided in the above-mentioned embodiment of the present application adjusts the position of the bright field detector and / or the dark field detector to accurately match the corresponding field of view changes under the change of imaging magnification, thereby achieving adjustable detection accuracy while meeting the requirements of dark field imaging and bright field imaging for field of view integrity, thereby achieving the purpose of covering the bright and dark field imaging fields under multiple imaging magnifications, improving imaging accuracy through precise matching, solving the problem of dark field imaging field of view changes, and avoiding interference with bright field imaging, thereby improving detection accuracy; at the same time, while realizing simultaneous detection of bright and dark field common optical paths and separate fields of view, the switching of imaging magnifications and matching of imaging fields of view support the free configuration of multiple detection accuracies and detection modes in response to the diverse requirements of different detection objects in terms of accuracy and speed.

[0065] 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 defect detection device, characterized in that: It comprises a first illumination light source, an objective lens, a second illumination light source, a bright field detector and a dark field detector, wherein the magnification of the objective lens is switchable, and the position of the bright field detector and / or the dark field detector is adjustable; The light beam emitted by the first 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 acquired by the bright field detector, and a bright field image is obtained by imaging; The light beam emitted by the second 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 which is acquired by the dark field detector, and a dark field image is obtained by imaging; wherein: By adjusting the position of the dark field detector so that the target surface of the dark field detector covers the dark field acquisition field corresponding to any magnification of the objective lens, and / or adjusting the position of the bright field detector so that the target surface of the bright field detector covers the bright field acquisition field corresponding to any magnification of the objective lens, and avoiding the mutual crosstalk between the dark field acquisition field and the bright field acquisition field caused by the change of the illumination spot position; 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 defect detection device according to claim 1, characterized in that: The bright field detector and the dark field detector are respectively a bright field camera and a dark field camera, the target surfaces of the bright field camera and the dark field camera are respectively in a conjugate relationship with the plane where the wafer to be measured is located, and the field of view center of the bright field camera and the field of view center of the dark field camera have a preset eccentricity relative to the optical center field of view.

3. The wafer defect detection device according to claim 2, characterized in that: The off-axis amount L of the dark field camera, the magnification M of the objective lens and the position l of the dark field illumination spot relative to the optical center field of view have the following relationship: l=L / M.

4. The wafer defect detection device according to claim 3, characterized in that: When the magnification of the objective lens is switched to M1, and the position l of the dark field illumination spot relative to the optical center field of view is fixed, the target surface of the dark field camera needs to be moved to a position corresponding to the off-axis amount, and satisfy L1=l×M1.

5. The wafer defect detection device according to claim 2, characterized in that: If the target length of the dark field camera is K, the maximum imaging field of view is the field length K′=K / Mmin of the objective lens at the minimum magnification, and the length of the dark field illumination spot must satisfy C=K′+b, where b is the range in which the dark field illumination spot is larger than the field of view required for imaging, and b is 1~5mm.

6. The wafer defect detection device according to claim 4, characterized in that: It also includes a driving device, which is used to modulate the position of the bright field detector and / or the dark field detector on the imaging plane.

7. The wafer defect detection device according to claim 1, characterized in that: There are two second illumination light sources, and the light paths of the light beams emitted by the second illumination light sources are symmetrically distributed. The incident plane of the light beams emitted by the second illumination light sources that are incident on the surface of the wafer to be measured after passing through the dark field illumination light path is not perpendicular to the plane where the dark field illumination spot is located.

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

9. The wafer defect detection device according to claim 1, characterized in that: It also includes a spectroscopic element. The bright field signal light and the dark field signal light after passing through the objective lens are incident on the spectroscopic element. The spectroscopic element separates the bright field signal light and the dark field signal light and reflects them to the bright field detector and the dark field detector respectively.

10. A control method, applied to the wafer defect detection device according to any one of claims 1 to 9, characterized in that: The control method comprises the following steps: Switch the magnification of the objective lens; The position of the dark field detector is adjusted so that the target surface of the dark field detector covers the corresponding dark field acquisition field of view at any magnification of the objective lens, and / or the position of the bright field detector is adjusted so that the target surface of the bright field detector covers the corresponding bright field acquisition field of view at any magnification of the objective lens, thereby avoiding mutual crosstalk between the dark field acquisition field of view and the bright field acquisition field of view caused by changes in the position of the illumination spot.

11. The control method according to claim 10, characterized in that: When the magnification of the objective lens is switched to M1 and the position l of the dark field illumination spot relative to the optical center field of view is fixed, the eccentricity L1=l×M1 of the dark field camera relative to the optical center field of view is calculated, and the target surface of the dark field camera is moved to the position corresponding to L1.

12. The control method according to claim 11, characterized in that: If the target length of the dark field camera is K, the maximum imaging field of view is the field length K′=K / Mmin of the objective lens at the minimum magnification, and the length of the dark field illumination spot is configured to be C=K′+b, where b is the range in which the dark field illumination spot is larger than the field of view required for imaging, and b is 1~5mm.

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