CN117238785A - Detection device and detection equipment - Google Patents

Abstract

The present disclosure provides a detection apparatus and a detection device including the detection apparatus, the apparatus including: a light source; the light source end beam splitting unit is used for splitting light emitted by the light source into a first light beam and a second light beam; a first lighting unit receiving the first light beam; a second illumination unit that receives the second light beam and causes the second light beam to provide illumination to the focus mark; the beam combining unit is used for combining the first light beam and the second light beam; the objective lens is used for enabling the first light beam and the second light beam after beam combination to be projected onto the bearing table and imaging a sample and a focusing mark on the bearing table; the detection end beam splitting unit is used for splitting a first detection light containing sample imaging information and a second detection light containing focusing mark imaging information; a first detection unit that detects first detection light; and the second detection unit detects second detection light, and the focusing mark imaging information in the second detection light comprises the imaging definition of the focusing mark to obtain the focusing position of the object lens on the sample. The detection device disclosed by the disclosure improves the detection precision.

Description

Detection device and detection equipment

Technical Field

The present disclosure relates to the field of integrated circuit devices, and in particular, to a detection apparatus and a detection device.

Background

In integrated circuit manufacturing processes, wafer (wafer) surfaces are typically inspected, for example: CD (Critical Dimension ) and OVL (Overlay) were tested. In addition, each process is prone to various defects on the wafer surface, such as: incomplete or uneven pattern, bubble defects, surface scratches, particle defects, and the like. These defects tend to reduce wafer yield, and therefore, there is also a need to screen products by a defect inspection apparatus.

With the development of the technology to the third generation of semiconductor materials, the transparent semitransparent polymers are used for the wafers, and the defects of scratches, cracking, edge breakage and the like are easily caused on the surfaces of the wafers in the integrated circuit manufacturing process, so that higher requirements are put on the detection technology.

Disclosure of Invention

The problem addressed by the present disclosure is to provide a detection apparatus and a detection device, which improve detection accuracy by improving imaging quality.

To solve the above-mentioned problems, the present disclosure provides a detection apparatus including: a light source; the light source end beam splitting unit is used for splitting light emitted by the light source into a first light beam and a second light beam; a first lighting unit for receiving the first light beam; a second illumination unit configured to receive the second light beam and cause the second light beam to provide illumination to a focus mark; the beam combining unit is used for combining the first light beam and the second light beam with the focusing mark information; the objective lens is used for enabling the first light beam and the second light beam after beam combination to be projected onto the bearing table and imaging the sample and the focusing mark on the bearing table; the detection end beam splitting unit is used for splitting the first detection light containing the imaging information of the sample and the second detection light containing the imaging information of the focusing mark; a first detection unit configured to detect first detection light; and the second detection unit is used for detecting second detection light, and the focusing mark imaging information in the second detection light comprises focusing mark imaging definition and is used for obtaining the focusing position of the object lens on the sample.

Optionally, the second illumination unit comprises a grating scale for providing a focusing mark.

Optionally, the second illumination unit is critical illumination.

Optionally, the grating ruler is a transmission type grating ruler, and the second lighting unit sequentially includes on a light path: a first lens for focusing the second light beam at the position of the grating scale; and the second lens is used for receiving the second light beam transmitted through the grating ruler and converting the second light beam into parallel light.

Optionally, the grating scale is position-adjustable in its extending direction and comprises a plurality of regions, each region having a different grating pitch.

Alternatively, the pitch of each region is in the range 5 to 200 microns.

Optionally, the first lighting unit is kohler lighting or critical lighting.

Optionally, the first illumination unit is kohler illumination, and includes a third lens for focusing the first light beam at a back focal plane of the objective lens.

Optionally, the light source end beam splitting unit and the detection end beam splitting unit are polarization beam splitters; the first light beam and the first detection light are first linearly polarized light, and the second light beam and the second detection light are second linearly polarized light.

Optionally, a first analyzer is arranged between the detection end beam splitting unit and the first detection unit, and is used for transmitting first linearly polarized light; and a second analyzer is arranged between the detection end beam splitting unit and the second detection unit and used for transmitting second linearly polarized light.

Optionally, a first half-wave plate is arranged between the light source and the light source end beam splitting unit and used for adjusting the rotation angle of the linearly polarized light of the light source end.

Optionally, a second half-wave plate is arranged between the objective lens and the beam splitting unit at the detection end, and is used for adjusting the rotation angle of the linearly polarized light at the detection end.

Optionally, the position of the objective lens in the optical axis direction is adjustable.

Optionally, the system further comprises a processing unit, which is integrated with the second detection unit or is an independent component, and is used for obtaining an evaluation function of the imaging definition of the focusing mark, judging the focusing position of the objective lens through the evaluation function, and further controlling the objective lens to move to the focusing position.

Optionally, a displacement spectroscope is arranged between the detection end beam splitting unit and the second detection unit, and is used for obtaining a first imaging area and a second imaging area on the second detection unit; the processing unit obtains a first objective lens position when the objective lens position makes the first imaging area the clearest; and further for obtaining a second imaging position when the objective lens position sharpens the second imaging region; the intermediate position of the first imaging position and the second imaging position is the focusing position of the object lens on the sample.

Optionally, the first detection unit is an area-array camera, and the second detection unit is a line-array camera or an area-array camera.

Optionally, the second detection unit is a line-scan camera, a slit is disposed between the detection end beam splitting unit and the line-scan camera, and the slit is parallel to a stripe formed by imaging of the grating ruler.

Optionally, the light source is a single light source, and is configured to emit a single light beam.

Optionally, one or more displacement spectroscopes are arranged between the beam splitting unit at the detection end and the second detection unit, and are used for obtaining a plurality of imaging areas on the second detection unit.

Correspondingly, the disclosure also provides a detection device, which comprises the detection device provided by the disclosure.

Compared with the prior art, the technical scheme of the present disclosure has the following advantages:

according to the imaging method and the imaging device, the first illumination unit is arranged to provide illumination for imaging of the sample, and the second illumination unit is also arranged to provide illumination for imaging of the focusing mark (for example, the grating ruler), so that different illumination modes can be respectively configured according to respective requirements of imaging of the sample and imaging of the focusing mark, and imaging quality is improved.

In an alternative scheme, the polarized beam splitter splits the light emitted by the light source, and imaging is carried out by polarized light, so that the definition of imaging details can be improved, and the imaging quality is further improved.

In the alternative scheme, the second illumination unit adopts critical illumination to provide focusing marks for the grating ruler of interference fringes, so that the influence of light generated by non-uniformity of illumination on two sides of the grating ruler can be reduced, and in addition, the light projected to a non-imaging space can be reduced, so that the light efficiency is improved, and imaging conditions with high signal to noise ratio and high definition are provided.

In the alternative, the grating ruler is adjustable in position in the extending direction and comprises a plurality of areas, each area has different grating pitches, in practical application, the areas corresponding to the grating pitches can be matched aiming at different wafer processes, focusing is realized by the areas, and then more accurate self-focusing positions can be obtained.

Drawings

FIG. 1 is an optical diagram of one embodiment of a detection apparatus of the present disclosure;

FIG. 2 is a contrast image of FIG. 1 using different light sources;

FIG. 3 is a schematic diagram of the half-wave plate of FIG. 1 with the rotation angle adjusted;

FIG. 4 is a partial light path diagram of another embodiment of a detection apparatus of the present disclosure;

FIG. 5 is a comparison of two focus states in the embodiment of the detection apparatus shown in FIG. 4;

fig. 6 is a plot of a sharpness evaluation function obtained by the detection apparatus shown in fig. 4 in two focusing states.

Detailed Description

As known from the background art, the imaging quality of the current detection device cannot meet the requirements of the process on the detection precision.

In order to solve the technical problem, the present disclosure provides a detection device, referring to fig. 1, an optical path diagram of an embodiment of the detection device of the present disclosure is shown. The detection device includes: a light source 100, a light source-side beam splitting unit 101, a first illumination unit 102, a second illumination unit 103 including a focusing mark, a beam combining unit 104, an objective lens 105, a detection-side beam splitting unit 107, a first detection unit 108, and a second detection unit 109.

According to the method, the first illumination unit 101 is arranged to provide illumination for sample imaging, and the second illumination unit 102 is also arranged to provide illumination for focusing marks, so that different illumination modes can be respectively configured according to respective imaging requirements of sample imaging and focusing mark imaging, and imaging quality and detection accuracy are improved.

Wherein the light source 100 is configured to provide illumination light. In this embodiment, the light source 100 is a single light source. By single light source is meant herein that only one light source provides illumination light for both the first illumination unit 102 and the second illumination unit 103. The compactness of the detection device can be improved by adopting a single light source mode, and the cost can be reduced.

Specifically, the light source 100 of the present embodiment is a white light source or a monochromatic light source (e.g., blue or red light).

Referring to fig. 2, a comparison of the imaging of fig. 1 using different light sources is shown, wherein fig. 2a is an image of a sample obtained with a white light source (white LED) and fig. 2b is an image obtained with a blue light source (blue LED). As can be seen from a comparison of the images of the two light sources, the white light source can provide satisfactory images, while the blue light source can provide more detailed features on the sample with higher imaging quality.

Instead of using LEDs as the light source 100, the light source 100 may be a halogen light source or a laser light source.

In practical applications, the light source 100 may be configured according to the accuracy requirements and cost requirements of the detection device. If the accuracy requirement is high, a monochromatic light source or a laser light source can be adopted. If a low cost configuration is required, a white light halogen light source may be employed as the light source 100.

The light source end beam splitting unit 101 is configured to split light emitted from the light source 100 into a first light beam and a second light beam. By the light source-side beam splitting unit 101, the illumination light emitted from the light source 100 can be split into two beams so as to enter the first illumination unit 102 and the second illumination unit 103, respectively.

In this embodiment, the light source-side beam splitting unit 101 is a polarizing beam splitter (Polarizing Beam Splitter, PBS) for splitting light emitted from the light source 100 into a first linearly polarized light (e.g., s-light) and a second linearly polarized light (e.g., p-light).

Specifically, the polarizing beam splitter transmits the first linearly polarized light and enters the first illumination unit 102, and is further configured to reflect the second linearly polarized light and enter the second illumination unit 103, thereby realizing beam splitting. Compared with the traditional light intensity imaging technology, the method has the advantages that the influence of the polarized light on the imaging quality of the sample and the focusing mark can be reduced by adopting the polarized light to image, so that more detail characteristics are captured, the imaging sensitivity is higher, the imaging quality is higher, and the self-focusing effect of the detection device based on imaging is optimized.

In other embodiments, the light source end beam splitting unit 101 may be another beam splitter, for example: displacement beam splitters, and the like.

As shown in fig. 1, in the present embodiment, a first half-wave plate 1111 is provided between the light source 100 and the light source-side beam splitting unit 101 for adjusting the rotation angle of the light source-side linearly polarized light, so that the components of the first linearly polarized light and the second linearly polarized light can be adjusted, and thus the components of the light respectively entering the first illumination unit 102 and the second illumination unit 103 can be adjusted.

The principle of adjusting the light component of the first half wave plate 1111 will be described with reference to fig. 3. In fig. 2, P1 represents the polarization state of light emitted by the light source 100, and the light is natural light without a specific polarization direction. P2 represents the light emitted from the light source, which is linearly polarized after passing through the first half wave plate 1111, and P3 and P4 represent the polarization direction of the first linearly polarized light and the polarization direction of the second linearly polarized light, respectively.

The angle between the linearly polarized light of the first half wave plate 1111 and the first linearly polarized light is α, if α is smaller than 45 degrees, the component of the first linearly polarized light is larger, and if α is larger than 45 degrees, the component of the second linearly polarized light is larger. Therefore, in practical application, the first linearly polarized light and the second linearly polarized light component can be adjusted by configuring the polarization direction of the first half-wave plate 1111, so that the light components respectively entering the first illumination unit 102 and the second illumination unit 103 can be controlled, and thus, the adjustment of the sample imaging and the light component imaging the focusing mark is realized, and further, the imaging quality is improved, and the self-focusing effect is optimized.

With continued reference to fig. 1, the detection device is further provided with a lens (not labeled) on the optical path between the light source 100 and the first half-wave plate 1111, for collimating the light emitted from the light source 100 to obtain a parallel light beam. In addition, the detection device is further provided with a diaphragm (not labeled) between the first half-wave plate 1111 and the light source side beam splitting unit 101, so that stray light entering the light source side beam splitting unit 101 can be reduced.

The first illumination unit 102 is configured to receive the first light beam, where the first light beam is configured to be projected onto the carrying platform, and provide illumination light to the sample 106 on the carrying platform, so as to implement imaging of the sample 106.

In this embodiment, the first illumination unit 102 adopts a kohler illumination method. The point on the whole plane of the illumination light field in the kohler illumination mode has even contribution, which not only eliminates the influence of the uneven shape and brightness of the light source on the illumination plane light field, but also improves the illumination efficiency to the greatest extent, so that as many light rays as possible are projected on the illumination plane, and therefore, the first illumination unit 102 in the kohler illumination mode can provide even and high-efficiency illumination light for the sample 106.

As in fig. 1, the first illumination unit 102 comprises a third lens 1020 for focusing the first light beam at the back focal plane of the objective lens 105, thereby realizing the manner of kohler illumination.

It should be noted that, in other embodiments, the first lighting unit 102 may also be a critical lighting manner. For critical illumination, the third lens 1020 may not be disposed in the first illumination unit 102, thereby implementing a critical illumination mode.

As shown in the optical path diagram of fig. 1, a reflecting mirror (not labeled) is further disposed on the optical path between the third lens 1020 and the light source end beam splitting unit 101, so as to change the direction of the optical path and improve the space compactness of the detection device.

The second illumination unit 103 includes a focus mark for receiving the second light beam and causing the second light beam to provide illumination light to the focus mark.

The focus mark is used as a reference for adjustment of the focus position of the objective lens 105. In the present embodiment, the grating scale 1030 is provided in the second illumination unit 103, and the second light beam can interfere through the grating scale 1030 (even in the process of imaging by the grating scale 1030), thereby generating fringes with alternate brightness and darkness, which are used as a focusing mark.

The second beam is used to provide illumination light to the grating scale 1030, thereby effecting imaging of the grating scale 1030. The detection device can determine whether the sample 106 is located at the optimal position of the objective lens 105 by analyzing the imaging definition of the grating 1030, and can implement the process of self-focusing the objective lens 105 and the sample 106 by adjusting the distance between the objective lens 105 and the sample 106 and determining the imaging definition of the grating 1030 in real time.

The grating scale 1030 is a measuring element that works by utilizing the optical principle of a grating, and is widely used in the field of detection. The grating scale 1030 images as fringes with alternate brightness due to interference phenomenon. In this embodiment, the second illumination unit is critical illumination, which is more favorable for providing illumination for the grating ruler 1030 with interference fringes for the imaging image, so that the influence of light generated by non-uniformity of illumination on measurement accuracy can be reduced.

Specifically, the grating scale 1030 is a plurality of lines formed of germanium material and arranged at intervals, the lines have a width in the micrometer range, and the pitch of the lines is the grating pitch.

In this embodiment, the grating scale 1030 is a transmissive grating scale, so that the light source end and the detection end can be respectively located at two sides of the grating scale 1030, and a larger space is provided for the arrangement of the optical elements of the light source end and the detection end. In other embodiments, a reflective grating scale 1030 may also be used.

In this embodiment, the second lighting unit 103 sequentially includes, in the optical path direction: a first lens 1031 for focusing the second light beam at the position of the grating scale 1030; and a second lens 1032 for receiving the second light beam transmitted through the grating ruler 1030 and converting the second light beam into parallel light. The critical illumination mode of the second illumination unit 103 can be achieved by the configuration of the relative positions of the first lens 1031, the grating scale 1030, and the second lens 1032. In other embodiments, the illumination mode of critical illumination may also be implemented by other optical elements and arrangements.

In this embodiment, the grating scale 1030 includes a plurality of regions in the extending direction thereof, and each region has a different grating pitch. In actual detection, the region corresponding to the grid distance can be matched for different wafer processes (for example, different process nodes), focusing can be realized by using the region, and further, a more accurate self-focusing position can be obtained. Alternatively, the pitch of each region is in the range 5 to 200 microns.

In order to enable imaging of the respective areas of the grating scale 1030 into the optical path of the second illumination unit 103. The position of the grating ruler 1030 in the extending direction is adjustable, specifically, a stepping motor is installed on the grating ruler 1030 to realize the adjustment of the position of the grating ruler 1030 in the extending direction, so that different areas of the grating ruler 1030 enter a detection light path.

As shown in fig. 1, a reflecting mirror is further disposed between the light source end beam splitting unit 101 and the second illumination unit 103, for changing the transmission path of the second light beam, so that the reflected second light beam is parallel to the first light beam, thereby improving the structural compactness of the detection device.

And a beam combining unit 104, configured to combine the first light beam and the second light beam transmitted through the grating scale 1030. Through beam combination, the first light beam and the second light beam can be guided to an imaging main light path (namely a light path where the objective lens 105 is located), and the sample and the grating ruler 1030 are imaged through the same imaging system, so that whether the objective lens 105 and the bearing table are at the optimal imaging position in the imaging system can be reflected through the imaging quality of the grating ruler 1030, and the self-focusing adjustment is realized through the objective lens 105, so that the imaging quality of the sample 106 is improved, and the detection precision is further improved.

In this embodiment, the beam combining unit 104 is also a polarizing element, and is configured to transmit the first linearly polarized light and reflect the second linearly polarized light, so as to combine the two polarized light beams. In other embodiments, the beam combining unit 104 may also be an optical element that performs beam combining based on other principles.

And an objective lens 105, configured to project the combined first beam and second beam onto a stage, and further configured to image the grating 1030 and a sample 106 (e.g., wafer) located on the stage.

As the semiconductor CD and OVL are reduced, the sample 106 is typically imaged with a high magnification objective lens in order to capture more detailed images. For example: 50X-150X objective lens. In this embodiment, the objective lens 105 is a 100X objective lens, on one hand, the objective lens 105 with the magnification can meet the requirement of the detection device on detail image acquisition, and on the other hand, the volume of the objective lens 105 with the magnification is not too large, so that the volume of the whole detection device is reduced.

In this embodiment, the third lens 1020 focuses the first light beam to the back focal plane of the objective lens 105, so that the first light beam becomes more ideal parallel light after passing through the objective lens 105. The parallel light irradiates the sample 106 to provide a more uniform illumination, so that the illumination of the sample 106 falls into the category of kohler illumination. The kohler illumination allows for substantially comparable illumination conditions for each region of the sample 105, and higher sample imaging quality can be achieved when the first beam is projected onto the sample and then reflected and imaged by the objective lens 105.

The second beam projects the interference fringes formed by the grating scale 1030 onto the stage and reflects the fringes, and the fringes are also imaged by the objective lens 105. The grating scale 1030 and the sample 106 are imaged by the same objective lens 105 in a coaxial imaging light path, so that the imaging definition of the grating scale 1030 can reflect whether the sample 106 is located at the focusing position of the objective lens 105, so that the most clear imaging can be obtained by controlling the position of the objective lens 105.

In this embodiment, the position of the objective lens 105 along the optical axis direction (Z) is adjustable, so that when the sample is not located at the optimal focal plane of the objective lens 105, the position of the objective lens 105 can be adjusted, thereby obtaining clearer imaging. The position of the objective lens 105 in the optical axis direction can be adjusted specifically by a stepping motor.

In other embodiments, the position of the objective lens 105 may be fixed, and the position of the bearing table in the optical axis direction of the objective lens 105 may be adjustable, so as to achieve the purpose of self-focusing. Alternatively, the positions of the objective lens 105 and the stage may be adjusted in the Z direction to achieve a larger adjustment range.

As shown in fig. 1, in the detection device of this embodiment, a reflecting mirror is further disposed between the beam combining unit 104 and the objective lens 105, and is configured to change the first beam and the second beam after beam combination by reflection, so as to couple the light after beam combination into an imaging main optical path (i.e., an imaging optical path formed by the objective lens 105, the first detection unit 108, and the second detection unit 109).

The first light beam is reflected by the sample 106 and then passes through the objective lens 105 to become first detection light containing imaging information of the sample; the second light beam contains focusing mark information, reflects on the surface of the stage, and then forms an image through the objective lens 105, thereby forming second detection light containing focusing mark imaging information.

In addition, the detection device of the embodiment further comprises: the half mirror 110 is configured to reflect the first light beam and the second light beam after beam combination into the objective lens 105, and transmit the first detection light and the second detection light, and enter a subsequent detection end for detection.

Accordingly, the detection device includes: a detection end beam splitting unit 107 for splitting the first detection light containing the imaging information of the sample and the second detection light containing the imaging information of the focusing mark so as to perform detection respectively.

The beam splitting of the detection light can be realized by the detection end beam splitting unit 107, so that interference of detection of the focusing mark on sample imaging information is reduced.

In this embodiment, the detection end beam splitting unit 107 is a polarizing beam splitter, and is configured to transmit the first linearly polarized light and reflect the second linearly polarized light. Specifically, the first detection light containing the imaging information of the sample is first linearly polarized light, and the first linearly polarized light can pass through the detection end beam splitting unit 107 and reach the first detection unit 108, so as to realize detection of the first detection light. The second detection light containing the focusing mark imaging information is second linearly polarized light, and is reflected by the detection end beam splitting unit 107 and reaches the second detection unit 109, so as to realize detection of the second detection light, wherein the focusing mark imaging information in the second detection light comprises focusing mark imaging definition, and the focusing mark imaging definition is used for obtaining the focusing position of the objective lens on the sample.

In this embodiment, the polarization beam splitter can make the detection surfaces of the first detection unit 108 and the second detection unit 109 perpendicular, so that not only the interference of the light but also the reasonable arrangement of the detection elements can be realized. In other embodiments, other beam splitting elements may also be implemented to split the first detection light and the second detection light at the detection end.

In this embodiment, the first detecting unit 108 and the second detecting unit 109 are both photodetectors, and are configured to convert optical signals into electrical signals, so as to perform subsequent data processing.

Specifically, the first detection unit 108 is an area camera, and may provide a larger detection surface for the sample.

In this embodiment, the grating ruler images to form the fringes with alternate brightness, and the second detection unit 109 is a line camera, so that detection on non-fringe images can be reduced, and higher-precision detection can be further realized.

In addition, as shown in fig. 1, in order to reduce stray light entering the line camera, a slit 113 is further disposed between the detection end beam splitting unit 107 and the second detection unit 109, and the slit 113 is parallel to a stripe formed by imaging the grating ruler 1030, so as to further reduce stray light entering the line camera.

It should be noted that if a nonlinear pattern is obtained by using other focusing marks, other shapes of the matched detecting elements and stray-eliminating elements may be used to optimize the detecting effect of the second detecting unit 109. For example, the image obtained by focusing the mark is a ring with alternate brightness, stray light can be eliminated through an aperture diaphragm, and detection is performed through an area camera.

In other embodiments, the second detecting unit 109 may also be an area-array camera, through which the interference fringes formed by the grating ruler 1030 may be detected as a whole.

A first analyzer 1101 is disposed between the detection-side beam splitting unit 107 and the first detection unit 108, for transmitting the first linearly polarized light. During the detection process, the light beam sequentially passes through the first illumination unit 102, is reflected by the bearing table, and is imaged by the objective lens 105, so that light with other polarization states is easy to be doped into the first linearly polarized light, the first linearly polarized light can be transmitted through the first analyzer 1101, and the other polarized light is blocked from entering the first detection unit 108, so that the detection precision of sample imaging is improved.

Similarly, a second analyzer 1102 is provided between the detection-side beam-splitting unit 107 and the second detection unit 109 for transmitting second linearly polarized light. The detection accuracy of the focusing mark imaging can be improved by the second analyzer 1102 based on a similar principle to the first analyzer 1101.

As shown in fig. 1, a second half-wave plate 1112 is further disposed between the objective lens 105 and the detection end beam splitting unit 107, for adjusting the rotation angle of the detection end linearly polarized light. Similar to the principle of the first half-wave plate 1111, the components of the first detection light entering the first detection unit 108 and the second detection light entering the second detection unit 109 can be controlled by the angle between the second half-wave plate 1112 and the first linearly polarized light and the second first polarized light split by the detection-side beam splitting unit 107.

As shown in fig. 1, the detection device further includes: and a processing unit 112, configured to process the data of the focus marks detected by the second detection unit 109, and further make self-focusing feedback.

The processing unit 112 may be integrated in the second detection unit 109 as part of the second detection unit 109, thereby improving the integration of the detection device. Alternatively, the processing unit 112 may be a separate component, which increases the flexibility of the detection device.

In imaging, the sample 106 is positioned on the stage, and the focus marks are illuminated by the second illumination unit 103, thereby forming a shadowgraph image on the stage. If the stage is located at the focal plane of the objective lens 105, both the projected images of the sample and the focus marks have the sharpest imaging, whereas when the stage is located at the objective lens 105 without being located at the focal plane, both the projected images of the focus marks and the imaged images of the sample will be degraded. In practical applications, the focal position of the objective lens 105 may be determined according to the extremum of the evaluation function of the imaging sharpness of the focusing mark (i.e., the maximum value of sharpness), so as to control the objective lens 105 to move to the focal position.

In this embodiment, the processing unit 112 determines the focal plane position of the objective lens 105 based on the imaging definition of the focusing mark, and controls the position of the objective lens 105 to make the surface of the bearing table (i.e. the sample position) be located at the focusing position of the objective lens 105, so as to optimize the imaging quality of the sample.

In practical application, in order to improve the detection accuracy, a dual-focusing (or multi-focusing) mode can be adopted to reduce the detection error. The basic principle is that images at two positions have the same definition when imaging at the same distance above or below the focal plane.

Referring to fig. 4, a partial light path diagram of another embodiment of the detection device of the present disclosure is illustrated, and the embodiment is the same as the embodiment illustrated in fig. 1, and is not described in detail, in which the embodiment adopts a light path diagram of a dual focusing mode, and the second detection unit 209 of the embodiment adopts an area camera.

As shown in fig. 4, a displacement beam splitter 214 is provided between the detection-side beam splitting unit 207 and the second detection unit 209 for obtaining a first imaging region i and a second imaging region ii on the second detection unit 209. Specifically, a part of the second detection light projected onto the displacement beam splitter 214 may be transmitted to reach the first imaging area i of the second detection unit 209, and another part of the second detection light is reflected twice by the displacement beam splitter 214 and then reaches the second imaging area ii of the second detection unit 209. Since the second probe light reaching the first imaging region i and the second imaging region ii has different optical paths (the optical path reaching the second imaging region ii is longer in the drawing), by controlling the movement of the objective lens 105 in the Z direction, it is possible to achieve two focusing states in which the first imaging region i is clear and the second imaging region ii is blurred, and in which the first imaging region i is blurred and the second imaging region ii is clear.

Referring to fig. 5, a comparison of two focus states is shown in the embodiment of the detection apparatus shown in fig. 4. Wherein fig. 5a is an image taken when the first imaging area i is clear and the second imaging area ii is blurred, and wherein fig. 5b is an image taken when the first imaging area i is blurred and the second imaging area ii is clear. The processing unit obtains a first objective lens position when the objective lens moves to make the first imaging area I clearer; and is also used for obtaining the second objective position when the objective lens moves to make the second imaging area II clearer; the intermediate position of the first objective lens position and the second objective lens position is the focusing position of the objective lens on the sample. The dual-focus detection device shown in fig. 4 obtains a focus position through two imaging positions, so that problems such as optical errors, acquisition errors, mechanical errors and the like caused by single focusing can be reduced, and the detection precision is improved.

In this embodiment, the position of the objective lens along the optical path may be adjusted, and the position of the objective lens refers to the absolute position thereof. In other embodiments, the position of the bearing table along the optical axis direction may be adjustable, and the position of the objective lens refers to the relative position of the bearing table.

Specifically, the processing unit 112 is configured to obtain an evaluation function of the imaging sharpness of the focusing mark, and determine the focusing position of the objective lens according to the evaluation function, so as to control the objective lens to move to the focusing position to obtain the sharpest imaging.

As shown in fig. 6, a sharpness evaluation function curve obtained by the detection device shown in fig. 4 in two focus states is shown. Specifically, the sharpness evaluation function curve is obtained by a processing unit of the detection device. Fig. 6a is a first sharpness function curve corresponding to the first objective lens position, and fig. 6b is a second sharpness function curve corresponding to the second objective lens position. The abscissa of the first or second sharpness function curve represents the coordinate value of the objective lens in the Z direction, and the ordinate represents the quantized numerical value representing the sharpness of the image. Wherein a larger value on the ordinate indicates a higher image sharpness, whereas a smaller value on the ordinate indicates a lower image sharpness.

As shown in fig. 6a, in the first sharpness function curve, F1 is the first imaging position with the highest sharpness, and its coordinates are (1.92,77.96). In the second sharpness function curve, F2 is the second imaging position with the highest sharpness and its coordinates are (1.68,78.55). Since the two positions F1 and F2 are relatively close in sharpness, it can be determined that F1 and F2 are positions above and below the focal plane at the same distance from the focal plane, respectively, and the focal position obtained by taking the intermediate position of the first objective lens position and the second objective lens position as the focal position of the objective lens, that is, (z1+z2)/2 as the focal position of the objective lens, specifically, the focal position obtained by the two curves shown in fig. 6 is (1.92+1.68)/2=1.8. Then, the objective lens can be controlled to a focusing position corresponding to 1.8 through the stepping motor, so that the imaging quality with extremely high definition can be obtained, and the detection precision is optimized.

It should be noted that fig. 4 illustrates an example in which two imaging regions are obtained by one displacement beam splitter. In other embodiments, the imaging areas (for example, 3, 4, 5 and … … imaging areas) of more areas may be implemented on the second detection unit through a plurality of optical elements such as displacement spectroscopes, and by respectively controlling the multiple imaging areas to sequentially obtain clear images, a greater number of focusing positions may be obtained, so that detection errors may be further eliminated, and detection accuracy may be improved.

It should be noted that, fig. 4 illustrates an area-array camera as an example, and for the detection device provided with the slit and the line-array camera, the displacement spectroscope is disposed between the slit and the line-array camera, so as to change the optical paths of different areas, thereby realizing the effect of displaying different definition images in multiple areas.

In order to solve the technical problem, the disclosure further provides a detection device, including the detection apparatus provided by the disclosure, and the specific technical scheme of the detection apparatus may refer to the related description of the foregoing embodiment, which is not repeated herein.

The detection equipment comprises the optical path and the like of the detection device provided by the embodiment, and also comprises mechanical elements such as a mechanical shell and a bracket, so that the detection device can be fixed and protected, and further comprises electric elements such as an external driving and general control unit and the like, so that the normal starting and running of the detection device can be realized.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims (20)

1. A detection apparatus, characterized by comprising:

a light source;

the light source end beam splitting unit is used for splitting light emitted by the light source into a first light beam and a second light beam;

a first lighting unit for receiving the first light beam;

a second illumination unit configured to receive the second light beam and cause the second light beam to provide illumination to a focus mark;

the beam combining unit is used for combining the first light beam and the second light beam with the focusing mark information;

the objective lens is used for enabling the first light beam and the second light beam after beam combination to be projected onto the bearing table and imaging the sample and the focusing mark on the bearing table;

the detection end beam splitting unit is used for splitting the first detection light containing the imaging information of the sample and the second detection light containing the imaging information of the focusing mark;

a first detection unit configured to detect first detection light;

and the second detection unit is used for detecting second detection light, and the focusing mark imaging information in the second detection light comprises focusing mark imaging definition and is used for obtaining the focusing position of the object lens on the sample.

2. The detection apparatus according to claim 1, wherein the second illumination unit includes a grating scale for providing a focus mark.

3. The detection apparatus according to claim 2, wherein the second illumination unit is critical illumination.

4. A detection device according to claim 3, wherein the grating scale is a transmissive grating scale, and the second illumination unit comprises, in order in the optical path:

a first lens for focusing the second light beam at the position of the grating scale;

and the second lens is used for receiving the second light beam transmitted through the grating ruler and converting the second light beam into parallel light.

5. The inspection apparatus of claim 2 wherein said grating scale is adjustable in position in its direction of extension and comprises a plurality of regions, each region having a different grating pitch.

6. The detecting device for detecting the rotation of a motor rotor as claimed in claim 5, wherein the pitch of each region is in the range of 5 to 200 μm.

7. The detection apparatus according to claim 1, wherein the first illumination unit is kohler illumination or critical illumination.

8. The detection apparatus according to claim 7, wherein the first illumination unit is a kohler illumination, comprising a third lens for focusing the first light beam at a back focal plane of the objective lens.

9. The detecting device according to claim 1, wherein the light source side beam splitting unit and the detection side beam splitting unit are polarization beam splitters; the first light beam and the first detection light are first linearly polarized light, and the second light beam and the second detection light are second linearly polarized light.

10. The detecting device for detecting the rotation of a motor rotor as claimed in claim 9, wherein a first analyzer for transmitting the first linearly polarized light is provided between the detecting-end beam splitting unit and the first detecting unit;

and a second analyzer is arranged between the detection end beam splitting unit and the second detection unit and used for transmitting second linearly polarized light.

11. The detecting device for detecting the rotation of a motor rotor as claimed in claim 9, wherein a first half-wave plate is provided between the light source and the light source end beam dividing unit for adjusting the rotation angle of the light source end linearly polarized light.

12. The detecting device for detecting the rotation of a motor rotor as claimed in claim 9, wherein a second half-wave plate for adjusting the rotation angle of the linearly polarized light of the detecting end is provided between the objective lens and the beam splitting unit of the detecting end.

13. The detecting device according to claim 1, wherein a position of the objective lens in the optical axis direction is adjustable.

14. The apparatus according to claim 13, further comprising a processing unit, integrated with the second detecting unit or a separate component, configured to obtain an evaluation function of imaging sharpness of the focusing mark, and further configured to determine a focusing position of the objective lens according to the evaluation function, so as to control movement of the objective lens to achieve focusing.

15. The detecting device for detecting the rotation of a motor rotor as claimed in claim 14, wherein a displacement beam splitter is provided between the detecting end beam splitting unit and the second detecting unit for obtaining a first imaging region and a second imaging region on the second detecting unit;

the processing unit obtains a first objective lens position when the objective lens position makes the first imaging area the clearest; and further for obtaining a second objective position when the objective position sharpens the second imaging region; the intermediate position of the first objective lens position and the second objective lens position is the focusing position of the objective lens on the sample.

16. The detection apparatus according to any one of claims 1 to 15, wherein the first detection unit is an area camera, and the second detection unit is a line camera or an area camera.

17. The detecting device for detecting the rotation of a motor rotor as claimed in any one of claims 1 to 15, wherein the focusing marks are provided by a grating ruler, the second detecting unit is a line camera, a slit is arranged between the beam splitting unit at the detecting end and the line camera, and the slit is parallel to the stripes formed by imaging of the grating ruler.

18. The detection apparatus according to any one of claims 1 to 15, wherein the light source is a single light source for emitting a single light beam.

19. The detection apparatus according to any one of claims 1 to 14, wherein one or more displacement beam splitters are provided between the detection end beam splitting unit and the second detection unit for obtaining a plurality of imaging areas on the second detection unit.

20. A detection apparatus comprising a detection device according to any one of claims 1 to 19.