CN218674758U

CN218674758U - Optical device

Info

Publication number: CN218674758U
Application number: CN202221385859.5U
Authority: CN
Inventors: 赵康俊; 黄有为; 陈鲁; 张嵩
Original assignee: Shenzhen Zhongke Feice Technology Co Ltd
Current assignee: Shenzhen Zhongke Feice Technology Co Ltd
Priority date: 2022-06-02
Filing date: 2022-06-02
Publication date: 2023-03-21
Anticipated expiration: 2032-06-02

Abstract

The utility model provides an optical device, include: the filter is used for filtering incident light irradiated to the surface of the filter, the incident light forms detection light reaching the sample after being filtered by the filter, or the filter is used for filtering the incident light from the sample to form detection light; the filter comprises a plurality of sub light receiving surfaces, the filter is provided with a reference plane, the sub light receiving surfaces with zero included angle between the reference plane are first sub light receiving surfaces, and all the sub light receiving surfaces with zero included angle with the reference plane are positioned on the reference plane; the plurality of sub light receiving surfaces have a first sub light receiving surface, and the detection light is formed by incident light reflected by the first sub light receiving surface. The optical device can reduce the diffraction efficiency of the first sub-receiving surface to the high diffraction order of the incident light, improve the diffraction efficiency of zero-order light, and further improve the light utilization rate.

Description

Optical device

Technical Field

The present invention relates to an optical device, and more particularly to an optical device capable of filtering light through a pupil plane and a method of operating the same.

Background

In the production process of the chip, deposition and etching are carried out on a bare silicon base layer by layer to form a required pattern film layer, finally, a plurality of chips are formed on a wafer, and then the wafer is cut to form a single chip. The wafer with the patterned film layer formed on the bare silicon substrate is called a patterned wafer. In the process of manufacturing semiconductor transistors, if defects (e.g., particle dust) are formed on the wafer, voids may appear in the subsequently formed film layer, which may affect the performance of the formed chip.

Therefore, in order to improve the yield of the formed chips, it is necessary to detect defects on the surface of the patterned wafer and measure the positions or sizes of the formed patterns during the chip production process. The optical device has the advantages of no contact, small damage, high detection speed and the like, and is widely applied to the detection of the pattern wafer.

However, since the surface of the patterned wafer is formed with a complex pattern, when the patterned wafer is inspected by an optical device, the pattern on the surface of the wafer diffracts or scatters the inspection light, thereby interfering with the light formed by the defect, and reducing the inspection accuracy; in addition, higher requirements are also put on the measurement of the measurement pattern as the pattern is reduced, which requires adaptive adjustment of the angle of the detection light and the light intensity of the light spot according to the detected pattern.

In the prior art, light scattered by a pattern on a wafer surface needs to be filtered by a filter, or the light intensity of a light spot incident on the surface of the wafer needs to be adjusted by the filter.

The utility model provides an optical equipment can reduce the diffraction efficiency of high diffraction order, improves the diffraction efficiency of zero order light, and then can improve light utilization rate.

SUMMERY OF THE UTILITY MODEL

For solving the above problem, the utility model provides an optical device can reduce the diffraction efficiency of high diffraction order, improves the diffraction efficiency of zero order light, and then can improve light utilization rate.

The technical scheme of the utility model an optical equipment is provided, include: the filter is used for filtering incident light irradiated to the surface of the filter, the incident light forms detection light reaching the sample after being filtered by the filter, or the filter is used for filtering the incident light from the sample to form detection light;

the filter comprises a plurality of sub light receiving surfaces, the filter is provided with a reference plane, the sub light receiving surfaces with zero included angle between the reference plane are first sub light receiving surfaces, and all the sub light receiving surfaces with zero included angle with the reference plane are positioned on the reference plane; the plurality of sub light receiving surfaces have a first sub light receiving surface, and the detection light is formed by incident light reflected by the first sub light receiving surface.

Optionally, the angle of each sub light receiving surface is adjustable; the filter also comprises an adjusting module, wherein the adjusting module is used for adjusting the angle of each sub light receiving surface so as to enable the sub light receiving surfaces to have a first angle or a second angle, and the second angle is any angle except the first angle; the sub light receiving surface with the second angle is a second sub light receiving surface, and the second sub light receiving surface is used for separating the detection light after part of incident light is reflected.

Optionally, the second angles of the second sub light receiving surfaces are the same, and the second angle is 10 ° to 15 °.

Optionally, the optical device further comprises a lens assembly, wherein the lens assembly comprises: an objective lens located between the filter and the sample, the reference plane of the filter being coplanar with the pupil plane of the objective lens, or the lens assembly comprising an objective lens located between the filter and the sample, and a relay lens group located on the side of the objective lens remote from the sample, the reference plane of the filter being conjugate with the pupil plane of the objective lens, the relay lens group being configured to conjugate a filter plane with the pupil plane of the objective lens, the filter plane being coplanar with the reference plane;

wherein, the pupil plane of the objective lens is the focal plane of the objective lens far away from the sample side.

Optionally, the optical axis of the relay lens group and the optical axis of the objective lens have a non-zero included angle, and the filtering surface is not perpendicular to the central axis of incident light reaching the filter.

Optionally, the method further includes: a first detector; the objective lens is used for collecting incident light from a sample and enabling the incident light to reach the filter; the filter is used for filtering incident light collected by the objective lens to form detection light; the first detector is used for collecting the detection light and detecting the object to be detected according to the detection light.

Optionally, the first detector is configured to detect the sample according to the detection light; the first detector is an image sensor, and the detecting comprises imaging the sample to form a detection image; the filter is used for filtering a part formed by scattering of a background pattern on the surface of a sample in the incident light; the first detector is also used for acquiring the defects on the surface of the sample according to the detection image.

Optionally, the optical device further includes: the illumination assembly is used for emitting illumination light to the sample, and the illumination light forms the incident light after passing through the sample; the lighting assembly is a point light source, a line light source or a surface light source.

Optionally, the optical device further includes: a light source; the light source is used for generating the incident light, and the incident light forms detection light after being filtered by the filter and reaches the surface of the sample.

Optionally, the detection light reaching the sample is used for processing the sample, or the detection light forms signal light after passing through the sample, and the optical device further includes a second detector, which is used for detecting the signal light and detecting the sample according to the signal light.

Optionally, the objective lens is further configured to collect the signal light, and the optical apparatus further includes: a fourth beam splitter for separating the signal light collected by the objective lens from the detection light; the fourth beam splitter is located on the optical path between the objective lens and the relay or on the optical path between the relay and the filter.

Optionally, the lens assembly further comprises one or a combination of a first tube mirror and a variable power mirror; the first tube lens is positioned on the light path of one side of the filter, which is far away from the objective lens; the variable-magnification mirror is used for enabling the imaging magnification of the lens component to be adjustable.

Optionally, the relay lens group includes a first relay lens and a second relay lens, which are sequentially arranged, the objective lens is located on a light path between the sample and the first relay lens, the first relay lens is located on a light path between the objective lens and the second relay lens, and adjacent focuses of the first relay lens and the second relay lens are overlapped; the optical axes of the first relay lens and the second relay lens are overlapped, and the focal lengths of the first relay lens and the second relay lens are different.

Optionally, the focal length of the first relay lens is greater than the focal length of the second relay lens.

Optionally, all sub-illuminated surfaces of the filter form an illuminated surface of the filter; the size of the light receiving surface is equal to 0.8 gamma-11.2 gamma times of the size of the entrance pupil of the lens component, wherein gamma is a multiplying factor:

wherein β is an included angle between an exit direction of incident light propagating along an optical axis of the objective lens after passing through the relay lens group and the optical axis of the relay lens group, and γ is an included angle between the filter surface and the optical axis of the relay lens group; f. of ₂ Is the focal length of the first relay lens, f ₃ Is the focal length of the second relay lens.

Optionally, the focal length of the objective lens is 5mm to 20mm; the focal length of the first relay lens is 50-100 mm; the focal length of the second relay lens is 100-200 mm; and the included angle between the optical axis of the objective lens and the optical axis of the relay lens group is 20-40 degrees.

Optionally, the optical axis of the objective lens is parallel to the sample surface normal or an acute included angle is formed between the optical axis of the objective lens and the sample surface normal.

Optionally, the optical device further includes: a first beam splitter and a pupil viewer;

the first beam splitter is used for splitting the incident light, so that part of the incident light reaches the filter, and part of the incident light reaches the pupil observer, and the pupil observer is conjugated with the position of the filter; the first beam splitter is positioned on the optical path of one side of the filter along the opposite direction of the incident light propagation.

Optionally, the pupil viewer is an image sensor or a flat plate with a flat surface.

Optionally, the pupil viewer is an image sensor; the optical apparatus further includes a processor for forming a pupil image from the collected incident light by the image sensor; determining the position of a first sub light receiving surface according to the pupil image; setting a filter structure according to the position of the first sub light receiving surface; in the filter structure arranged according to the position of the first sub-receiving surface, the processor is specifically configured to: selecting a filter according to the first sub-receiving surface, and adjusting the position of the filter; or, the angle of each sub light receiving surface of the filter is adjustable, and the filter structure arranged according to the position of the first sub light receiving surface comprises: and adjusting the angle of the sub light receiving surface at the position of the first sub light receiving surface to enable the sub light receiving surface at the position to be the first sub light receiving surface, reflecting or transmitting the incident light to form the filtered light, and enabling the sub light receiving surfaces at other positions not to be parallel to the first sub light receiving surface.

The utility model discloses among the optical equipment that technical scheme provided, the reflected incident light of first sub-sensitive surface forms detect the light, and be zero all sub-sensitive surfaces between and the reference plane be located the coplanar, then the grating that is formed by first sub-sensitive surface no longer is the blazed grating, then can reduce the diffraction efficiency of first sub-sensitive surface to the high diffraction order of incident light, improves the diffraction efficiency of zero order light, and then can improve the light utilization ratio.

Further, the lens assembly includes: the optical system comprises an objective lens and a relay lens group, wherein the relay lens group is used for enabling a filter surface to be conjugated with a pupil surface of the objective lens, the pupil surface is a focal plane on one side, close to the relay lens group, of the objective lens, an optical axis of the relay lens group and an optical axis of the objective lens form a non-zero included angle, the filter surface is not perpendicular to a central axis of incident light reaching a filter, and the objective lens is located on a light path between a sample and the relay lens group; the filter is used for filtering the received incident light to form detection light; the filter comprises a first sub-acceptance surface which reflects or transmits the incident light to form the detection light; the optical axis of the first sub illuminated surface is not perpendicular to the optical axis of the relay lens group, and the first sub illuminated surface is parallel to the filtering surface. The device can separate the light reflected by the first sub light receiving surface of the filter from the incident light, so that the interference of the light reflected by the first sub light receiving surface to the incident light is reduced.

Further, the first sub light receiving surface reflects incident light to form detection light, so that the loss of the capacity of the detection light can be reduced, and if the filter surface is not perpendicular to the incident light reaching the filter, the detection light formed by reflecting the incident light reaching the first sub light receiving surface by the first sub light receiving surface is separated from the incident light, so that the energy loss of the subsequent separation detection light and the incident light can be reduced, and the utilization rate of light energy can be further improved.

Furthermore, incident light reaches the sample through the objective lens after being filtered by the filter, and the filter can control the incident angle of detection light, so that the interference of the detection light with an unnecessary incident angle is filtered, and the processing or detection precision is improved.

Further, the relay lens group comprises a first relay lens and a second relay lens; the focal length of the first relay lens is larger than that of the second relay lens, the relay lens group forms a reduced image on the pupil plane, so that the whole pupil plane of the objective lens can be filtered through a smaller filter, and the volume of the equipment is reduced.

Further, the optical device further comprises an illumination assembly for emitting illumination light to the sample, the illumination light forming the incident light after passing through the sample. The illumination assembly is a surface light source, so that the throughput of the optical equipment can be improved.

Drawings

The advantages and mode of realisation of the present invention will become more apparent from the following detailed description, given with reference to the accompanying drawings, wherein the same is given by way of illustration only, and not by way of limitation, in any sense, and wherein the same is given by way of illustration only, and not strictly to scale. In the drawings:

fig. 1 is a schematic structural diagram of a first embodiment of an optical device according to the present invention;

fig. 2 is a schematic diagram of an internal structure of a repeater according to a first embodiment of the optical device provided in the present invention;

fig. 3 is a schematic diagram illustrating an operating principle of a filter in a first embodiment of the optical device according to the present invention;

fig. 4 is a schematic structural diagram of an internal structure of a relay in a first embodiment of the optical device according to the present invention;

fig. 5 is a schematic structural diagram of a second optical embodiment according to the present invention;

fig. 6 is a schematic structural diagram of a third optical embodiment according to the present invention.

Detailed Description

The utility model discloses technical scheme provides an optical equipment can reduce the diffraction efficiency of first sub-photic face in the high diffraction order of incident light, improves the diffraction efficiency of zero order light, and then can improve light utilization rate.

In the prior art, in order to detect a pattern wafer, a detection system generally needs to use a fourier filter to filter out periodic patterns, so as to improve the signal-to-noise ratio of defects. The barrier strips are placed on the pupil plane, so that the spatial frequency components of the periodic patterns can be mechanically blocked, and the effect of filtering background patterns is achieved.

However, the system using mechanical filters for filtering has a complicated mechanical structure, high speed and poor flexibility, and only can detect a wafer with a specific pattern.

In order to solve the above-mentioned technical problem, an optical device uses a mirror array as a filter, however, since blazed gratings are formed on the sub light receiving surfaces of the mirror array, the energy ratio of the zero-order diffracted light of parallel light of different incident angles by the filter is different, and the energy ratio of the zero-order diffracted light is low, so that the energy loss is large.

In order to solve the above technical problem, the present invention provides an optical device, a filter for filtering incident light irradiated onto a surface of the filter, wherein the incident light forms detection light reaching a sample after being filtered by the filter or forms detection light after being used for filtering the incident light from the sample; the filter comprises a plurality of sub light receiving surfaces, the filter is provided with a reference plane, the sub light receiving surfaces with zero included angle between the reference plane are first sub light receiving surfaces, and all the sub light receiving surfaces with zero included angle with the reference plane are positioned on the reference plane; the plurality of sub light receiving surfaces have a first sub light receiving surface, and the detection light is formed by incident light reflected by the first sub light receiving surface. The optical device can reduce the diffraction efficiency of the first sub-receiving surface to the high diffraction order of the incident light, improve the diffraction efficiency of zero-order light, and further improve the light utilization rate.

The technical solution of the present invention will be described in detail with reference to the following examples.

Fig. 1 to fig. 3 are schematic structural diagrams of an embodiment of an optical device according to the present invention.

Referring to fig. 1 to 3, the present invention provides an optical apparatus, including: a filter 130 for filtering incident light irradiated onto the surface of the filter 130, wherein the incident light is filtered by the filter 130 to form detection light reaching the sample, or the filter 130 is used for filtering incident light from the sample to form detection light;

the filter 130 includes a plurality of sub light receiving surfaces 124, the filter 130 has a reference plane, the sub light receiving surface with a zero included angle between the reference planes is a first sub light receiving surface, and all the sub light receiving surfaces with a zero included angle with the reference plane are located in the reference plane; the plurality of sub light receiving surfaces have a first sub light receiving surface, and the detection light is formed by incident light reflected by the first sub light receiving surface.

The incident light reflected by the first sub light receiving surfaces forms the detection light, all the sub light receiving surfaces with zero included angle with the reference plane are located on the same plane, all the first sub light receiving surfaces are coplanar, and the grating formed by the first sub light receiving surfaces is not a blazed grating any more, so that the diffraction efficiency of the first sub light receiving surfaces to the incident light in the high diffraction order can be reduced, the diffraction efficiency of zero-order light can be improved, and the light utilization rate can be further improved.

In this implementation, the optical apparatus further comprises a lens assembly. The lens assembly comprises an objective lens 120 positioned between the filter 130 and the sample 100, and a relay group 122 positioned on the side of the objective lens 120 far from the sample 100, wherein the reference plane of the filter 130 is conjugate with the pupil plane of the objective lens 120, the relay group is used for conjugating a filter plane with the pupil plane of the objective lens 120, and the filter plane is coplanar with the first sub-acceptance plane; wherein the pupil plane of the objective lens 120 is the focal plane of the objective lens 120 on the side away from the sample 100.

In this embodiment, the article is for placement in a front focal plane of the objective lens; the front focal plane and the rear focal plane are respectively positioned at two sides of the objective lens.

In other embodiments of the present invention, the reference plane of the filter may be conjugate to the front focal plane of the objective lens; specifically, the filter reference plane is located at a focal plane of the subsequent first relay lens close to the second relay lens. In another implementation, the filter is located at any position on the optical path between the sample and the first detector.

In other embodiments of the present invention, the lens assembly includes: an objective lens located between the filter and the sample, a reference plane of the filter being located at a pupil plane of the objective lens; the reference plane of the filter can be conjugate with the front focal plane of the objective lens, so that the filter can limit the view field of the lens component and reduce stray light.

Specifically, in this embodiment, the lens assembly includes: the objective lens 120 and the relay lens group 122, the relay lens group 122 is configured to conjugate a pupil plane 121 of the objective lens 120 and a filter plane 124, the pupil plane 121 is a focal plane of the objective lens 120 on a side close to the relay lens group 122, an optical axis of the relay lens group 122 and an optical axis of the objective lens 120 have a non-zero included angle, and the filter plane 124 is not perpendicular to a central axis of incident light reaching the filter 130; the objective lens 120 is located in the optical path between the sample 100 and the relay lens group 122.

The filter 130 is configured to filter the received incident light to form detected light; the filter 130 includes a first sub light receiving surface that reflects or transmits the incident light to form the detection light; the optical axis of the first sub light receiving surface is not perpendicular to the optical axis of the relay lens group 122, and the first sub light receiving surface is parallel to the filter surface 124.

The filter surface is conjugated with the pupil surface of the objective lens 120 through the relay lens group 122, and the first sub light receiving surface of the filter 130 is parallel to the filter surface because the filter surface is conjugated with the pupil surface of the objective lens 120 through the relay lens group 122, so that the pupil surface of the objective lens 120 can be accurately filtered through the filter 130, and the detection precision is improved; meanwhile, since the optical axis of the relay lens group 122 and the optical axis of the objective lens 120 form a non-zero included angle, the filter surface may not be perpendicular to the incident light reaching the filter 130, so that the light reflected by the first sub light receiving surface of the filter 130 can be separated from the incident light, thereby reducing the interference of the reflected light of the first sub light receiving surface to the incident light.

In this embodiment, the incident light comes from the sample 100, and the objective lens 120 is used for collecting the incident light from the sample 100 and making the incident light reach the filter 130 through the relay lens group 122.

In this embodiment, the optical apparatus further comprises a first detector for detecting the sample 100 according to the detection light.

In this embodiment, the first detector is an image sensor, and the detecting includes imaging the sample 100 to form a detection image. Specifically, the image sensor includes: a CCD or CMOS camera. In other embodiments of the present invention, the first detector may also be a spectrometer or a light intensity detector, and the light intensity detector includes a photodiode or a photomultiplier tube.

In this embodiment, the optical device further includes: and an illumination assembly 110 for emitting illumination light to the sample 100, the illumination light forming the incident light after passing through the sample 100. Specifically, the illuminating light is reflected, scattered, diffracted, or transmitted by the sample 100 to form the incident light.

Specifically, in this embodiment, the illumination light is scattered by the sample 100 to form the incident light, and the first detector performs dark field detection on the sample 100. The incident angle of the illumination light is different from the exit angle of the incident light. In other embodiments of the present invention, the illuminating light is reflected by the sample 100 to form the incident light, and the first detector is right for bright field detection of the sample 100.

The emergent angle of the incident light is zero degree, and the incident angle of the illuminating light is 15-75 degrees. In other embodiments of the present invention, the exit angle of the incident light may be greater than zero, and the incident angle of the illumination light may be zero.

In another embodiment of the present invention, the exit angle of the incident light is the same as the incident angle of the illumination light, and the incident angle is zero degree. The optical device further comprises a third beam splitter for separating the illumination light and the incident light; specifically, the third beam splitter is located on the light path between the objective lens 120 and the relay lens group 122, or the third beam splitter is located on the light path between the relay lens group 122 and the filter; illumination light generated by the illumination assembly 110 enters the objective lens 120 after being reflected by the third beam splitter, and the incident light enters the relay lens group 122 after being transmitted by the third beam splitter; or the illumination light generated by the illumination assembly enters the objective lens 120 after being transmitted by the third beam splitter, and the incident light enters the relay lens group 122 after being reflected by the third beam splitter.

The incidence angle of the illumination light is an included angle between the central line of the illumination light and the normal of the surface of the sample 100; the exit angle of the incident light is the angle between the incident light and the normal to the surface of the sample 100.

The illumination assembly 110 is a point light source, a line light source or a surface light source. Specifically, the illumination assembly is a surface light source 240, which can increase the detection speed, and the filter 130 filters the incident light to filter the background interference light, so that the detection precision can be improved by using the surface illumination light. The illumination assembly is a surface light source, and the throughput of the optical equipment can be improved.

In this embodiment, the optical axis of the objective lens 120 is parallel to the surface normal of the sample 100 or an acute included angle is formed between the optical axis of the objective lens 120 and the surface normal of the sample 100.

The filter 130 is used for filtering out the part of the incident light formed by the background pattern scattering of the surface of the sample 100; the first detector is also used for acquiring the defect on the surface of the sample 100 according to the detection image.

Specifically, the objective lens 120 is configured to collect incident light from the sample 100, collimate the incident light, and make the collimated incident light incident on the relay lens group 122; the relay lens group 122 is configured to image the pupil plane 121 of the objective lens 120 onto the filter plane 124 according to the collected incident light, and the filter 130 filters the incident light to filter out a portion of the incident light formed by scattering of a background pattern on the surface of the sample 100, so as to form the detected light; the first detector is configured to collect the detection light and detect the sample 100 according to the detection light.

In this embodiment, the optical device is used to detect defects on the surface of the sample 100; in other embodiments of the present invention, the first detector is further used for detecting the size, thickness, position or shape of the object to be detected.

The sample 100 is a wafer, a chip, a screen, or a back case of a mobile phone.

In this embodiment, the optical axis of the objective lens 120 is perpendicular to the surface of the sample 100, and an acute included angle is formed between the optical axis of the relay lens group 122 and the normal of the surface of the sample 100. The objective lens 120 is located in the optical path between the sample 100 and the relay lens group 122.

Specifically, the objective lens 120 includes only one or more lenses. In other embodiments, the objective lens 120 may include only one or more mirrors; or the objective lens 120 includes a lens and a mirror.

Referring to fig. 2, the relay lens group 122 includes a first relay lens 1221 and a second relay lens 1222 arranged in sequence, the objective lens 120 is located on the optical path between the sample 100 and the first relay lens 1221, and the first relay lens 1221 is located on the optical path between the objective lens 120 and the second relay lens 1222.

In this embodiment, the adjacent focal points of the first relay lens 1221 and the second relay lens 1222 coincide; the optical axes of the first relay lens 1221 and the second relay lens 1222 are coincident, and the focal lengths of the first relay lens 1221 and the second relay lens 1222 are different.

In other embodiments of the present invention, the adjacent focal points of the first relay lens 1221 and the second relay lens 1222 may not coincide; and/or the optical axes of the first relay lens 1221 and the second relay lens 1222 have an acute included angle.

In other embodiments, the relay lens group 122 may be an optical diffraction element.

Specifically, in this embodiment, the first relay lens 1221 collects the incident light passing through the objective lens 120 and converges the incident light onto the focal plane adjacent to the first relay lens 1221 and the second relay lens 1222, the incident light enters the second relay lens 1222 through the focal plane adjacent to the first relay lens 1221 and the second relay lens 1222, and the incident light passing through the second relay lens 1222 forms an image of the pupil plane 121 at the filter plane 124.

The filter 130 partially blocks the image of the pupil plane 121 to block part of the incident light from entering the detection assembly, so as to filter the interference light scattered by the background on the surface of the sample 100, thereby improving the detection accuracy of the optical device.

In this embodiment, the first relay mirror 1221 is a lens, and the second relay mirror 1222 is a lens; in other embodiments of the present invention, the first relay lens 1221 is a mirror, and specifically, the first relay lens 1221 is a spherical mirror or an aspheric mirror; the second relay mirror 1222 is a mirror, and specifically, the second relay mirror 1222 is a spherical mirror or an aspheric mirror. Referring to fig. 4, fig. 4 is a schematic diagram illustrating that the first relay mirror 1221 and the second relay mirror 1222 are both mirrors. The first relay mirror 1221 and the second relay mirror 1222 are both concave mirrors.

Referring to fig. 2 and 4, adjacent focal points of the first relay lens 1221 and the second relay lens 1222 coincide; the optical axes of the first relay lens 1221 and the second relay lens 1222 are coincident, and the imaging relation can be deduced that:

wherein f is ₁ Is the focal length of the objective lens 120, f ₂ Is the focal length, f, of the first relay lens 1221 ₃ The focal length of the second relay lens 1222 is α, which is the angle at which the object point on the surface of the sample enters the relay lens group 122 in parallel after passing through the objective lens 120, β is the angle at which the parallel light exits the relay lens group 122, γ is the angle between the pupil plane 121 and the optical axis of the relay lens group 122 after being imaged by the relay lens group 122, and θ is the angle between the pupil plane 121 and the plane perpendicular to the optical axis of the relay lens group 122.

From the above formula, when f ₂ ≠f ₃ It is possible to achieve tan β · tan γ ≠ 1, i.e. of the filter surface 124 and the relay lens group 122The optical axis is not vertical, and the parallel incident light is incident obliquely to the filter 130.

All sub-illuminated surfaces of the filter form an illuminated surface of the filter.

The optical principle can be derived, and the magnification before and after the pupil size is imaged by the relay lens group 122 is as follows:

specifically, in the present embodiment, the size of the light receiving surface of the filter is equal to 0.8 Γ to 11.2 Γ times the size of the entrance pupil of the lens assembly, where Γ is a magnification factor:

wherein β is an included angle between an exit direction of incident light propagating along the optical axis of the objective lens 120 after passing through the relay lens group 122 and the optical axis of the relay lens group 122, and γ is an included angle between the filtering surface 124 and the optical axis of the relay lens group 122; f. of ₂ Is the focal length, f, of the first relay lens 1221 ₃ Is the focal length of the second relay mirror 1222.

This application is by design f ₂ And f ₃ The pupil size after imaging by relay optics group 122 is made to approach the filter 130 size and a larger spacing is maintained between relay optics group 122 and filter 130 for placement of the pupil viewer. In this embodiment, the focal length of the first relay mirror 1221 is greater than the focal length of the second relay mirror 1222. The focal length of the first relay mirror 1221 is greater than the focal length of the second relay mirror 1222, so that the size of the image formed by the pupil plane 121 via the relay mirror group 122 is smaller than the size of the pupil plane 121, and the size of the filter 130 can be reduced.

Specifically, the size of a pupil formed by imaging the entrance pupil of the lens assembly through the relay lens group is equal to the size of the light receiving surface of the filter.

Specifically, in this embodiment, the focal length of the objective lens is 5mm to 20mm; the focal length of the first relay lens is 50-100 mm; the focal length of the second relay lens is 100-200 mm; and the included angle between the optical axis of the objective lens and the optical axis of the relay lens group is 20-40 degrees.

In this embodiment, the filter 130 includes a plurality of sub-acceptance surfaces; the sub light receiving surfaces are reflecting surfaces, and the angle of each sub light receiving surface is adjustable; the filter 130 further includes an adjusting module, which is configured to adjust an angle of each sub light receiving surface, so that the sub light receiving surface has a first angle and a second angle, where the second angle is any angle other than the first angle. Each second angle may be the same or different.

The sub light receiving surface with the first angle is a first sub light receiving surface, the sub light receiving surface with the second angle is a second sub light receiving surface, the second sub light receiving surface is used for separating part of incident light from the detection light after reflecting, the filter 130 is provided with reference planes, and all the sub light receiving surfaces with zero included angle between the reference planes are positioned on the reference planes; the first angle is an included angle between the first sub light receiving surface and the reference plane, and the second angle is an included angle between the second sub light receiving surface and the reference plane.

The sub light receiving surfaces are reflecting surfaces, incident light is reflected to form detection light, the loss of the capacity of the detection light can be reduced, the filter surface is not perpendicular to the incident light reaching the filter, the detection light formed by the incident light reaching the first sub light receiving surface after being reflected by the first sub light receiving surface is separated from the incident light, and therefore the energy loss of the subsequent separation detection light and the incident light can be reduced, and the utilization rate of light energy is further improved.

Specifically, the filter 130 is a DMD.

Referring to fig. 3, when the included angle between each sub light receiving surface and the reference plane is not zero, it can be regarded as a blazed grating, and diffraction satisfies the grating equation:

d(sinθ _i -sinθ _o )＝mλ (5)

where d is the arrangement period of the sub light receiving surfaces of the filter 130, and θ _i And theta _o Respectively an incident angle and an emergent angle, m is a diffraction order, and lambda is an incident wavelength，θ _B Is the blaze angle of the grating. The blaze angle of the filter 130 is ± 12 °.

The lens assembly is an infinity corrected optical system, and the light beam passes through the relay lens group 122 and then enters the filter 130 as parallel light. Assuming that all the first sub-acceptance surfaces of the filter 130 are deflected to the 12 ° direction, the angle between the second sub-acceptance surface and the reference plane is rotated to-12 °. However, the filter 130 acts as a blazed grating and introduces new diffraction, that is, the parallel light is diffracted after passing through the first sub-light receiving surface of the filter 130. Wherein, the 0-order diffracted beam is useful imaging information, and other diffracted-order beams can cause poor imaging quality. Therefore, it is necessary to increase the 0-order diffraction beam energy ratio as much as possible.

Referring to fig. 3, the on-axis object point and the off-axis object point on the surface of the sample 100 pass through the objective lens 120 and the relay lens group 122, and then are incident on the surface of the filter 130 at different angles. As can be seen from equation (5), the diffraction patterns of parallel light beams with different incident angles passing through the blazed grating are different. Therefore, the included angles between all the first sub light receiving surfaces and the reference plane are deflected to 12 degrees, which cannot satisfy the condition that the energy ratio of all the parallel light 0-order diffracted light beams is the largest, and the imaging quality is deteriorated.

In order to solve the above problem, in the present embodiment, the angle between the first sub light receiving surface and the reference plane is set to 0 °, and the second included angles of all the second sub light receiving surfaces are set to nonzero values.

Specifically, the first angles of the first sub light receiving surfaces are the same, the second angles of the second sub light receiving surfaces are the same, the first sub light receiving surfaces are located in the same plane, the first angles are zero degrees, the second angles are 10 ° to 15 °, for example ± 12 °, and in other embodiments, the second angles of the second sub light receiving surfaces may be different.

The first sub light receiving surfaces are positioned in the same plane, so that the diffraction efficiency of the first sub light receiving surfaces to the high diffraction order of incident light can be reduced, the diffraction efficiency of zero-order light can be improved, and the light utilization rate can be further improved. Specifically, when the first sub-light receiving surfaces are located in the same plane, the filter 130 is no longer a blazed grating, the 0-order diffracted light beam has the same angle as the incident light beam, that is, the energy ratio of the 0-order diffracted light beam after the parallel light beams at all incident angles are diffracted by the filter 130 is the same.

In one embodiment, the incident light is 266nm long, the 0 th order diffraction efficiency of filter 130 can be 83%, and the + -1 st order diffraction efficiency is 1.36%. It can be seen that, in this scheme, approximately 83% of energy of parallel light after being reflected by the DMD enters the first tube mirror 126 for subsequent imaging, and other diffraction orders are negligible and have no influence on imaging quality.

The lens assembly further comprises one or a combination of a first tube mirror 126 and a zoom mirror 127; the first tube lens 126 is positioned on the optical path of the filter 130 far away from the objective lens 120; the variable power mirror 127 is used for making the imaging magnification of the lens component adjustable.

The first tube mirror 126 includes only one or more lenses, or the first tube mirror 126 includes only one or more mirrors, or the first tube mirror 126 includes both lenses and mirrors.

The optical apparatus further includes: a first beam splitter 123 and a pupil viewer 125; the pupil viewer 125 is used to monitor the pupil plane 121 to determine the position of the first sub-acceptance surface of the filter 130.

The first beam splitter 123 is located on an optical path between the relay lens group 122 and the filter 130, and the first beam splitter 123 is configured to split the incident light such that a part of the incident light reaches the filter 130 and a part of the incident light reaches the pupil observer 125, where the pupil observer 125 is conjugate to the filter 130.

The pupil viewer 125 is a flat panel or image sensor with a flat surface, the image sensor including a CCD or CMOS; specifically, the flat surface is a diffuse reflection surface; the flat plate is made of paper, ceramics, wood plates or plastics.

The pupil viewer is an image sensor; the optical apparatus further includes a processor for forming a pupil image from the collected incident light by the image sensor; determining the position of a first sub light receiving surface according to the pupil image; arranging a filter structure according to the position of the first sub light receiving surface;

in the filter structure arranged according to the position of the first sub-receiving surface, the processor is specifically configured to: selecting a filter according to the first sub-receiving surface, and adjusting the position of the filter; or, the angle of each sub light receiving surface of the filter is adjustable, and the filter structure arranged according to the position of the first sub light receiving surface comprises: and adjusting the angle of the sub light receiving surface at the position of the first sub light receiving surface to enable the sub light receiving surface at the position to be the first sub light receiving surface, reflecting or transmitting the incident light to form the filtered light, and enabling the sub light receiving surfaces at other positions not to be parallel to the first sub light receiving surface.

The number of the first detectors is multiple, and the optical device further includes a second beam splitter 135, where the second beam splitter 135 is configured to split the detection light, so that the split detection light enters different first detectors respectively. The plurality of first detectors includes detector 129 and detector 128.

Specifically, in this embodiment, the number of the first detectors is two, and the second beam splitter 135 is a half mirror.

The two first detectors are respectively an area array detector and a linear array detector; the area array detector is an industrial camera, and the linear array detector is a TDI camera.

In this embodiment, the second beam splitter 135 is located on the optical path after the first tube mirror 126 and the variable power mirror 127.

The optical device further comprises a plurality of plane mirrors 132 located on the optical path, the plane mirrors 132 being arranged to change the propagation direction of the optical path.

In another embodiment of the present invention, the exit angle of the incident light is the same as the incident angle of the illumination light, and the optical apparatus further comprises a third beam splitter for separating the illumination light and the incident light; specifically, the third beam splitter is located on the light path between the objective lens 120 and the relay lens group 122, or the third beam splitter is located on the light path between the relay lens group 122 and the filter 130; illumination light generated by the illumination assembly enters the objective lens 120 after being reflected by the third beam splitter, and the incident light enters the relay lens group 122 after being transmitted by the third beam splitter; or the illumination light generated by the illumination assembly enters the objective lens 120 after being transmitted by the third beam splitter, and the incident light enters the relay lens group 122 after being reflected by the third beam splitter.

Fig. 5 is a schematic structural diagram of a second embodiment of the optical device of the present invention.

Referring to fig. 5, the same parts of the optical device in this embodiment as those in the first embodiment are not repeated herein, and the differences include:

in this embodiment, the optical device further includes: a light source 211 for generating the incident light, wherein the incident light is filtered by the filter 130 to form a detection light, and the detection light reaches the sample 100 through the objective lens 120;

the detection light reaching the sample 100 is used for processing the sample 100, or the detection light forms signal light after passing through the sample 100, and the optical device further comprises a second detector for detecting the signal light and detecting the sample 100 according to the signal light. Specifically, the detection light is reflected, scattered, diffracted, or transmitted by the sample 100 to form signal light.

The filter 130 adjusts the incident direction of the detection light by filtering the pupil plane 121, thereby satisfying the requirement of the optical device for the incident angle of the detection light. For example: the uniformity and symmetry of the detection light are improved, and the detection precision is improved. In other embodiments of the present invention, the reference plane of the filter 130 is conjugate to the front focal plane of the objective lens, so as to limit the size of the light spot incident on the sample surface. Specifically, the filter is located on a focal plane of the first relay lens on a side close to the second relay lens. In another embodiment, the filter may be located anywhere in the optical path between the light source and the sample.

In this embodiment, the optical apparatus further includes a second detector 240, and the second detector 240 is further configured to detect the sample 100 according to the signal light. Specifically, the sample 100 has alignment marks on its surface, where the alignment marks include a first mark and a second mark located on different layers or formed by different processes; the second detector 240 is used for acquiring an alignment error between the first mark and the second mark according to the signal light formed by the alignment mark.

The second detector 240 is conjugated to the sample 100 for acquiring an image of the surface of the sample 100; alternatively, the second detector 240 is conjugated to the pupil plane 121 for acquiring an image of the pupil plane 121.

In this embodiment, the detection light is reflected by the sample 100 to form the signal light. The optical apparatus further includes: a fourth beam splitter 242, the fourth beam splitter 242 being configured to separate the signal light and the detection light. Specifically, the fourth beam splitter 242 is configured to transmit the incident light and reflect the signal light, or the fourth beam splitter 242 is configured to reflect the detection light and transmit the signal light.

In this embodiment, the fourth beam splitter 242 is located on the optical path between the relay lens group 122 and the filter 130. In other embodiments, the fourth beam splitter 242 may also be located on the optical path between the objective lens 120 and the relay lens group 122.

In this embodiment, the detection device further includes: and a second tube mirror 241 for converging the signal light to the second detector 240 to image the surface of the sample 100. The second tube lens 241 converges the light emitted from the relay lens group 122 to the second detector 240. In other embodiments, the second tube lens 241 converges the light emitted through the objective lens 120 to the second detector 240.

Specifically, the optical device further includes: a shaping mirror 227, wherein the shaping mirror 227 is used for shaping the cross section of the incident light emitted by the light source 240; the collimating mirror group 226 is configured to collimate the incident light passing through the shaping mirror group 227, and the incident light passing through the collimating mirror group 226 reaches the filter 130.

The optical device further comprises a plurality of plane mirrors 132, wherein the plane mirrors 132 are used for changing the propagation direction of the incident light, so that the incident light passing through the collimating mirror group 226 reaches the filter 130.

The optical device further includes the first beam splitter 223, the first beam splitter 223 is conjugate to the filter 130, specifically, in this embodiment, the first beam splitter 223 is located on an optical path between the filter 130 and the collimator set 226, and the first beam splitter 223 is configured to split the incident light, so that the split incident light respectively reaches the filter 130 and the pupil observer 225.

Fig. 6 is a schematic structural diagram of a third embodiment of the optical device of the present invention.

The same parts of this embodiment as the embodiment shown in fig. 5 are not described herein again, but the differences include: in this embodiment, the optical apparatus does not include the fourth beam splitter. The detection light is scattered by the sample 100 to form the signal light. The incident angle of the detection light and the exit angle of the signal light are asymmetric with respect to the normal to the surface of the sample 100. Specifically, the incident angle of the detection light is different from the exit angle of the signal light, the detection light is perpendicular to the surface of the sample 100, and the signal light and the normal line of the surface of the sample 100 form a non-zero included angle.

In this embodiment, the optical device further includes: and a set of imaging mirrors (not shown) for imaging the surface of the sample 100 to the second detector 340, wherein the second detector 340 is used for detecting the sample 100 according to the image of the surface of the sample 100.

The optical axis of the imaging lens group and the optical axis of the objective lens 120 form a non-zero included angle. The optical axis of the second detector 340 is collinear with the optical axis of the imaging lens group.

It should be noted that, in the above embodiments of the present invention, the detecting light is all perpendicular to the surface of the sample 100, in other embodiments of the present invention, the detecting light may have a non-zero included angle with the normal line of the sample 100.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present invention, and the scope of the present invention is defined by the appended claims.

Claims

1. An optical device, comprising: the filter is used for filtering incident light irradiated to the surface of the filter, the incident light forms detection light reaching the sample after being filtered by the filter, or the filter is used for filtering the incident light from the sample to form detection light;

2. The optical device of claim 1, wherein the angle of each sub-receiving surface is adjustable; the filter also comprises an adjusting module, wherein the adjusting module is used for adjusting the angle of each sub light receiving surface so as to enable the sub light receiving surfaces to have a first angle or a second angle, and the second angle is any angle except the first angle; the sub light receiving surface with the second angle is a second sub light receiving surface, and the second sub light receiving surface is used for separating the detection light after part of incident light is reflected.

3. The optical apparatus of claim 2 wherein the second angle of each of the second sub light-receiving surfaces is the same, the second angle being between 10 ° and 15 °.

4. The optical device of claim 1, further comprising a lens assembly, the lens assembly comprising: an objective lens located between the filter and the sample, the reference plane of the filter being coplanar with the pupil plane of the objective lens, or the lens assembly comprising an objective lens located between the filter and the sample, and a relay lens group located on the side of the objective lens remote from the sample, the reference plane of the filter being conjugate with the pupil plane of the objective lens, the relay lens group being configured to conjugate a filter plane with the pupil plane of the objective lens, the filter plane being parallel to the reference plane;

and the pupil plane of the objective lens is a focal plane on the side of the objective lens far away from the sample.

5. The optical device according to claim 4, wherein the optical axis of the relay group has a non-zero angle with the optical axis of the objective lens, and the filter surface is not perpendicular to the central axis of the incident light reaching the filter.

6. The optical device according to claim 4, wherein the relay group is configured to conjugate a filter surface to a pupil plane of the objective lens, the filter surface being coplanar with the reference plane.

7. The optical device of claim 4 or 5, further comprising: a first detector;

the objective lens is used for collecting incident light from a sample and enabling the incident light to reach the filter;

the filter is used for filtering incident light collected by the objective lens to form detection light;

the first detector is used for collecting the detection light and detecting the object to be detected according to the detection light.

8. The optical apparatus of claim 7, wherein the first detector is configured to detect the sample based on the detected light; the first detector is an image sensor, and the detecting comprises imaging the sample to form a detected image; the filter is used for filtering out a part formed by scattering of a background pattern on the surface of the sample in the incident light; the first detector is also used for acquiring the defects on the surface of the sample according to the detection image.

9. The optical apparatus of claim 7, further comprising: the illumination assembly is used for emitting illumination light to the sample, and the illumination light forms the incident light after passing through the sample; the lighting assembly is a point light source, a line light source or a surface light source.

10. The optical apparatus of claim 4, further comprising: a light source; the light source is used for generating the incident light, and the incident light forms detection light after being filtered by the filter and reaches the surface of the sample.

11. The optical apparatus as claimed in claim 10, wherein the detection light reaching the sample is used for processing the sample, or the detection light forms a signal light after passing through the sample, and the optical apparatus further comprises a second detector for detecting the signal light and detecting the sample according to the signal light.

12. The optical apparatus of claim 11, wherein the objective lens is further configured to collect the signal light, the optical apparatus further comprising: a fourth beam splitter for separating the signal light collected by the objective lens from the detection light; the fourth beam splitter is located on the optical path between the objective lens and the relay or on the optical path between the relay and the filter.

13. The optical apparatus of claim 4 wherein the lens assembly further comprises one or a combination of a first tube mirror and a variable power mirror; the first tube lens is positioned on the light path of one side of the filter, which is far away from the objective lens; the variable-magnification mirror is used for enabling the imaging magnification of the lens component to be adjustable.

14. The optical apparatus of claim 5, wherein the relay lens group comprises a first relay lens and a second relay lens arranged in sequence, the objective lens is positioned on the optical path between the sample and the first relay lens, the first relay lens is positioned on the optical path between the objective lens and the second relay lens, and the adjacent focal points of the first relay lens and the second relay lens coincide; the optical axes of the first relay lens and the second relay lens are overlapped, and the focal lengths of the first relay lens and the second relay lens are different.

15. The optical device of claim 14, wherein the focal length of the first relay lens is greater than the focal length of the second relay lens.

16. The optical device of claim 14, wherein all sub-acceptance surfaces of the filter form an acceptance surface of the filter; the size of the light receiving surface is equal to 0.8 gamma-11.2 gamma times of the size of the entrance pupil of the lens component, wherein gamma is a multiplying factor:

17. The optical device according to claim 14, wherein the focal length of the objective lens is 5mm to 20mm; the focal length of the first relay lens is 50-100 mm; the focal length of the second relay lens is 100-200 mm; and the included angle between the optical axis of the objective lens and the optical axis of the relay lens group is 20-40 degrees.

18. The optical apparatus of claim 4, wherein the optical axis of the objective lens is parallel to the sample surface normal or has an acute angle with the sample surface normal.

19. The optical apparatus of claim 4, further comprising: a first beam splitter and a pupil viewer;

20. The optical apparatus of claim 19, wherein the pupil viewer is an image sensor; the optical apparatus further comprises a processor for forming a pupil image from the collected incident light by the image sensor; determining the position of a first sub light receiving surface according to the pupil image; arranging a filter structure according to the position of the first sub light receiving surface; in the filter structure arranged according to the position of the first sub-receiving surface, the processor is specifically configured to: selecting a filter according to the first sub-receiving surface, and adjusting the position of the filter; or, the angle of each sub light receiving surface of the filter is adjustable, and the filter structure arranged according to the position of the first sub light receiving surface comprises: and adjusting the angle of the sub light receiving surface at the position of the first sub light receiving surface to enable the sub light receiving surface at the position to be the first sub light receiving surface, reflecting or transmitting the incident light to form the detection light, and enabling the sub light receiving surfaces at other positions not to be parallel to the first sub light receiving surface.