CN112649435B - Focal plane measuring device and defect detection equipment - Google Patents
Focal plane measuring device and defect detection equipment Download PDFInfo
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- CN112649435B CN112649435B CN202011390083.1A CN202011390083A CN112649435B CN 112649435 B CN112649435 B CN 112649435B CN 202011390083 A CN202011390083 A CN 202011390083A CN 112649435 B CN112649435 B CN 112649435B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
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- G—PHYSICS
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0221—Testing optical properties by determining the optical axis or position of lenses
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/0278—Detecting defects of the object to be tested, e.g. scratches or dust
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
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Abstract
The invention provides a focal plane measuring device and a defect detecting device, comprising: the device comprises a focus measuring light source, a focus measuring marking plate, an optical assembly, an imaging unit, a focus plane compensation structure and a control unit; the focusing light source is used for providing a first illumination beam which is obliquely incident, the focusing mark plate comprises at least one group of focusing patterns, each group of focusing patterns comprises at least 3 sub marks, and after the first illumination beam is projected to the focusing mark plate, a measuring Jiao Tuxing is projected to the surface of the test sample piece and generates a reflected beam; the focal plane compensation structure is positioned on one side of the imaging surface of the imaging unit and is used for changing the transmission path of the reflected light beam so that the imaging surface of the reflected light beam converged by the optical component is positioned on the receiving surface of the imaging unit to form at least one group of signal images, and each group of signal images comprises at least 3 sub-patterns; the control unit obtains the vertical height of the test sample piece according to the position of at least one sub-pattern. The invention realizes the coaxial measurement of the focus point and the defect detection point and improves the precision of the focus plane measurement.
Description
Technical Field
The present invention relates to detection technology, and more particularly, to a focal plane measuring device and a defect detecting apparatus.
Background
With the deep and popular industrial automation and intellectualization, the use of automatic optical inspection equipment (Auto Optical Inspection, AOI) to replace traditional manual visual inspection has become a trend in technology development. AOI equipment is widely used in the fields of automobiles, medicines, traffic, semiconductors and the like by virtue of the rapid and accurate defect identification positioning capability.
Currently, existing AOI equipment typically includes optical imaging systems, stages, material transport systems, and the like. Wherein the optical imaging system comprises an illumination unit, an imaging objective, a detector, etc. The illumination unit is responsible for providing the required radiant light, the objective is used for collecting the surface light signal that awaits measuring, and the detector is responsible for converting light into digital signal.
As the resolution ratio of defect detection is higher and higher, when the resolution ratio of about 1 mu m is required, the focal depth is only about a few mu m, and the fluctuation of a detection sample and the shake of a moving platform can cause defocusing, so that the defect measurement accuracy of the sample is affected.
Fig. 1 is a schematic diagram of a defect detecting device in the prior art, as shown in fig. 1, light generated by a detecting light source 10 passes through an illumination lens group 11 and is reflected by a defect detecting mirror 12 to a half mirror 21. Part of the reflected light is projected onto the surface of the test sample 50 through the defect detection objective lens 20, and meanwhile, the defect detection objective lens 20 collects the reflected or scattered light on the surface of the test sample 50, and the reflected or scattered light enters the spatial light modulator 22 and the imaging light path rear end lens group 23 after passing through the half-reflecting half-lens 21, so that the light beam can be transmitted to the camera 30. The off-axis focal plane test point 41 of the off-axis focal plane measuring device 40 is not coincident with the focal plane 42 of the defect detection objective 20, and the off-axis focal plane test point 41 does not truly represent the focal plane 42 of the defect detection objective 20 when there is an inclination of the test piece 50, resulting in defocus at the time of defect detection.
Disclosure of Invention
The embodiment of the invention provides a focal plane measuring device and defect detecting equipment, which realize the coaxial measurement of a focal point and a defect detecting point, thereby improving the focal plane control precision, further improving the defect detecting resolution, ensuring that the imaging focal planes of reflected light beams of all sub marks in a focal measurement graph are coplanar and are all positioned on a receiving surface of an imaging unit, reducing the sampling difficulty, improving the mark imaging contrast and improving the focal plane measuring precision.
In a first aspect, an embodiment of the present invention provides a focal plane measurement apparatus, including: the device comprises a focus measuring light source, a focus measuring marking plate, an optical assembly, an imaging unit, a focus plane compensation structure and a control unit; the focusing light source is used for providing a first illumination light beam which is obliquely incident, the focusing mark plate comprises at least one group of focusing patterns, each group of focusing patterns comprises at least 3 sub marks, and after the first illumination light beam is projected onto the focusing mark plate, the focusing Jiao Tuxing is projected onto the surface of the test sample piece and generates a reflected light beam;
the focal plane compensation structure is positioned on one side of an imaging surface of the imaging unit and is used for changing the transmission path of the reflected light beam, so that the imaging surface of the reflected light beam converged by the optical component is positioned on a receiving surface of the imaging unit, at least one group of signal images are formed, the signal images are in one-to-one correspondence with the measurement Jiao Tuxing, each group of signal images comprises at least 3 sub-patterns, and each sub-pattern is in one-to-one correspondence with a sub-mark in the focus measurement pattern;
and the control unit acquires the vertical height of the test sample piece according to the position of at least one sub-pattern.
Optionally, the focal plane compensation structure comprises at least one corner cube set; the pyramid prism group comprises a first pyramid prism and a second pyramid prism, and the connecting line direction of the first pyramid prism and the second pyramid prism is parallel to the receiving surface of the imaging unit.
Optionally, the first pyramid prism and the second pyramid prism are both right angle prisms, and right angle surfaces of the first pyramid prism and the second pyramid prism are both 45 ° with the imaging unit receiving surface.
Optionally, each group of the focusing patterns on the focusing mark plate comprises at least M sub marks, wherein M is more than or equal to 3;
the focal plane compensation structure comprises N pyramid prism groups, wherein the N pyramid prism groups are sequentially arranged along the direction perpendicular to the receiving surface of the imaging unit, and N is more than or equal to 2 and less than or equal to M-1.
Optionally, the focusing mark plate comprises three groups of focusing patterns, and each group of focusing patterns comprises three sub marks.
Optionally, the optical component comprises a beam splitting prism and a projection relay lens, the reference mark plate comprises a reference pattern for reducing the influence of the structural change of the focal plane testing device, the second illumination beam is projected to the reference mark plate to form a reference beam carrying the information of the reference pattern,
the reflected light beam passes through the projection relay lens, then passes through the beam splitting prism, is combined with the reference light beam, and is projected to the imaging unit.
Optionally, the optical assembly further includes a mirror, and the reflected light beam reflected by the test sample is projected onto the mirror, and is reflected by the mirror to vertically propagate.
Optionally, the imaging device further comprises a magnification lens, and the reflected light beam is projected to the imaging unit after passing through the magnification lens.
Optionally, after the first illumination beam is projected onto the focusing mark plate, forming at least three focusing beams by at least 3 sub-marks in a group of focusing patterns; the focusing light beams are reflected by the surface of the test sample piece to form at least three reflected light beams, the reflected light beams are converged to the imaging unit after passing through the optical assembly to form at least three groups of signal images, the signal images correspond to the test Jiao Tuxing one by one, and each group of signal images comprises at least three light spots;
the incidence angle of the focusing light beam on the test sample piece is alpha, the magnification of the magnification lens is beta, the vertical position change distance of the test sample piece is dz, the moving distance of the light spot on the imaging unit is x, and the requirements are satisfied:
x＝2·dz·sinα·β。
in a second aspect, an embodiment of the present invention provides a defect detecting apparatus, including a focal plane measuring device according to the first aspect;
the device further comprises a defect detection unit, wherein the defect detection unit comprises a defect detection objective lens, and the focal point of the first illumination beam is positioned at the center of the field of view of the defect detection objective lens.
Optionally, the device further comprises a vertical inclination adjustment table, wherein the vertical inclination adjustment table is used for bearing a test sample;
the control unit is also used for controlling the vertical height of the test sample piece along the optical axis direction of the defect detection objective lens and adjusting the inclination angle of the test sample piece until the test sample piece is positioned in the depth of field range of the defect detection objective lens, and the inclination angle of the test sample piece is smaller than a preset value.
In the focal plane measuring device provided by the embodiment of the invention, the first illumination beam obliquely incident is provided by the focal length measuring light source, and the focal length measuring pattern on the focal length measuring mark plate is obliquely projected onto the surface of the test sample piece, so that the focal length measuring point of the first illumination beam can be positioned at the center of the field of view of the defect detection objective lens, the coaxial measurement of the focal length measuring point and the defect detection point is realized, the focal plane control precision is improved, and the defect detection resolution is further improved. On the other hand, the focal plane measuring device further comprises a focal plane compensation structure, the focal plane compensation structure changes the transmission path of the reflected light beam reflected by the surface of the test sample piece of the focal measurement graph, and the imaging focal plane of the reflected light beam is compensated to the receiving surface of the imaging unit, so that the imaging focal planes of the reflected light beams of all the sub marks in the focal measurement graph are coplanar and are all positioned on the receiving surface of the imaging unit, the sampling difficulty is reduced, the marking imaging contrast is improved, and the accuracy of focal plane measurement is improved.
Drawings
FIG. 1 is a schematic diagram of a defect detecting device in the prior art;
fig. 2 is a schematic structural diagram of a focal plane measuring device according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a signal image according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of an optical path before adding a focal plane compensation structure according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of an optical path after adding a focal plane compensation structure according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of focal plane testing principle according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a defect detecting apparatus according to an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
Fig. 2 is a schematic structural view of a focal plane measuring device according to an embodiment of the present invention, fig. 3 is a schematic structural view of a signal image according to an embodiment of the present invention, fig. 4 is a schematic optical path before a focal plane compensating structure is added according to an embodiment of the present invention, fig. 5 is a schematic optical path after a focal plane compensating structure is added according to an embodiment of the present invention, and referring to fig. 2 to fig. 5, a focal plane measuring device 60 includes a focal plane measuring light source 610, a focal plane measuring mark plate 611, an optical component 63, an imaging unit 66, a focal plane compensating structure 68, and a control unit 80. The focusing light source 610 is configured to provide a first illumination beam incident obliquely, and the focusing marking plate 611 includes at least one set of focusing patterns, each set of focusing patterns including at least 3 sub-marks. After the first illumination beam is projected onto the coking-measuring marking plate 611, the meter Jiao Tuxing is projected onto the surface of the test sample piece 50 and a reflected beam is generated. The focal plane compensation structure 68 is located at the imaging plane side of the imaging unit 66, and is used for changing the transmission path of the reflected light beam, so that the imaging plane 67, on which the reflected light beam is converged by the optical component 63, is located at the receiving plane of the imaging unit 66, and at least one group of signal images is formed, where the signal images correspond to the measured images Jiao Tuxing (one-to-one correspondence), and each group of signal images includes at least 3 sub-patterns, and each sub-pattern corresponds to a sub-mark in the measured image on the measured focus mark plate 611 one by one. The control unit 80 obtains the vertical height of the test sample 50 according to the position of at least one sub-pattern.
Illustratively, the geodesic marking plate 611 includes three sets of geodesic Jiao Tuxing 6111, each set of geodesic patterns including three sub-markings 6112, the three sub-markings 6112 preferably being three linear markings. After the first illumination beam is obliquely irradiated to the focusing mark plate 611, three groups of measuring points Jiao Tuxing and 6111 are projected onto the surface of the test sample piece 50 to form three groups of measuring points and generate three groups of reflected beams, the reflected beams are converged to the imaging unit 66 through the optical assembly 63 to form three groups of signal images, as shown in fig. 3, the signal images correspond to the measuring points Jiao Tuxing (one-to-one correspondence), and each group of signal images comprises three light spots, namely three sub-patterns, and the light spots correspond to the sub-marks one to one. For a silicon wafer to be tested with a photoetching pattern on the surface, as different photoetching patterns have different reflectivities, so that different photoetching patterns at different positions can influence the intensity of a signal image, in order to reduce the influence of the photoetching patterns on the intensity of the signal image, the acquisition of the signal image is facilitated, each group of focus measurement patterns 6111 comprise a plurality of sub-mark design schemes, when the intensity of a sub-pattern signal generated by one sub-mark is weaker than that of acquisition and analysis, the sub-pattern signal generated by other sub-marks 6112 is measured, and in addition, the influence caused by uneven reflectivities can be reduced by adopting a plurality of sub-marks 6112, so that the measurement accuracy is further improved. In this embodiment, each group of the focal length measurement patterns 6111 includes three sub-marks 6112, so that it can be ensured that signal images meeting the intensity requirement can be acquired. Furthermore, by adopting 3 groups of focusing patterns, the focal plane positions of 3 points of the test object can be obtained at the same time, and further the inclination posture measurement of the whole focal plane can be obtained.
Further, taking one of the sets of the coking patterns on the coking mark plate 611 as an example, as shown in fig. 4, after the first illumination beam is projected onto the coking mark plate 611 before the focal plane compensation structure 68 is added, three coking beams are formed by 3 sub-marks in the set of coking patterns, which are respectively a first coking beam L1, a second coking beam L2 and a third coking beam L3. The first, second and third focusing beams L1, L2 and L3 are reflected by the surface of the sample 50 to form first, second and third reflected beams L1', L2' and L3 'respectively, and the first, second and third reflected beams L1', L2 'and L3' are converged to the imaging unit 66 to form 3 light spots through the optical assembly 63. The imaging focal plane of the first reflected light beam L1' is located behind the receiving plane of the imaging unit 66, the imaging focal plane of the second reflected light beam L2' is located above the receiving plane of the imaging unit 66, and the imaging focal plane of the third reflected light beam L3' is located in front of the receiving plane of the imaging unit 66, that is, the first reflected light beam L1' and the third reflected light beam L3' are in an out-of-focus state. As shown in fig. 5, after the focal plane compensation structure 68 is added, the first reflected light beam L1' and the second reflected light beam L2' are projected onto the focal plane compensation structure 68, and the transmission path is changed by the focal plane compensation structure 68 such that the imaging focal planes of the first reflected light beam L1', the second reflected light beam L2', and the third reflected light beam L3' are coplanar and all located on the receiving surface of the imaging unit 66, so as to form a clear signal image.
After acquiring the signal images, the control unit 80 acquires the vertical height of the surface of the test piece 50 according to the position of at least one light spot in the set of signal images. Further, the coking marking plate 611 comprises M groups of meters Jiao Tuxing, M.gtoreq.3. That is, the focus measurement mark plate 611 includes at least three sets of focus measurement patterns, and accordingly, at least three focus plane compensation structures are provided, each focus plane compensation structure corresponds to one set of focus measurement patterns one by one and adjusts the imaging path of the corresponding focus measurement pattern, so as to obtain at least three sets of signal images, and based on the positions of respective light spots in the at least three sets of signal images, the vertical height difference between different sets of signal images is obtained, so as to realize the tilt measurement of the test sample 50.
In the focal plane measuring device 60 provided by the embodiment of the invention, the first illumination beam with oblique incidence is provided by the focal length measuring light source 610, and the focal length measuring pattern on the focal length measuring mark plate 611 is obliquely projected onto the surface of the test sample piece 50, so that the focal length measuring point of the first illumination beam can be positioned at the center of the field of view of the defect detecting objective lens 20, and the coaxial measurement of the focal length measuring point and the defect detecting point is realized, thereby improving the focal plane control precision and further improving the defect detecting resolution. On the other hand, the focal plane measuring device 60 further includes a focal plane compensation structure 68, where the focal plane compensation structure 68 changes the transmission path of the reflected light beam reflected by the surface of the test sample 50 in the focal plane measuring pattern, and compensates the imaging focal plane of the reflected light beam to the receiving surface of the imaging unit 66, so that the imaging focal planes of the reflected light beams of the sub-marks in the focal plane measuring pattern are coplanar and all located on the receiving surface of the imaging unit 66, thereby reducing the sampling difficulty, improving the mark imaging contrast, and improving the accuracy of focal plane measurement.
Optionally, referring to fig. 5, the focal plane compensation structure 68 includes at least one corner cube set 680. The pyramid prism group 680 includes a first pyramid prism 681 and a second pyramid prism 682, and the line direction of the first pyramid prism 681 and the second pyramid prism 682 is parallel to the receiving plane of the imaging unit 66. That is, the direction of the connection line between the first pyramid prism 681 and the second pyramid prism 682 is perpendicular to the main ray direction of the reflected light beam incident on the pyramid prism group 680. The direction of the line connecting the first pyramid prism 681 and the second pyramid prism 682 refers to the direction of the line connecting the geometric center of the first pyramid prism 681 and the geometric center of the second pyramid prism 682. In the embodiment of the present invention, the first pyramid prism 681 and the second pyramid prism 682 are adopted to form the pyramid prism group 680, and at least one pyramid prism group 680 is adopted to change the transmission path of the reflected light beam, so as to compensate the focal planes of the plurality of focusing light beams to the receiving plane of the imaging unit.
Alternatively, referring to fig. 5, the first angular pyramid prism 681 and the second angular pyramid prism 682 are right angle prisms, and the right angle faces of the first angular pyramid prism 681 and the second angular pyramid prism 682 are 45 ° from the receiving face of the imaging unit 66. The right angle faces of the first angular pyramid prism 681 and the second angular pyramid prism 682 are also each 45 ° from the chief ray of the focusing beam. The reflected light beam is projected onto the first right angle surface of the first pyramid prism 681, reflected by the first right angle surface of the first pyramid prism 681, projected onto the first right angle surface of the second pyramid prism 682 along the direction perpendicular to the principal ray of the reflected light beam, reflected by the first right angle surface of the second pyramid prism 682 onto the second right angle surface of the second pyramid prism 682, reflected by the second right angle surface of the second pyramid prism 682, projected onto the second right angle surface of the first pyramid prism 681, reflected by the second right angle surface of the first pyramid prism 681, and then continuously propagated along the direction of the principal ray of the reflected light beam. In the embodiment of the present invention, the right angle surfaces of the first pyramid prism 681 and the second pyramid prism 682 are 45 ° with the receiving surface of the imaging unit 66, and the light reflected by the right angle surfaces of the first pyramid prism 681 and the second pyramid prism 682 propagates along the direction perpendicular to the incident light, which is beneficial to control the propagation direction of the light.
Illustratively, referring to fig. 5, the first right angle surface of the first pyramid prism 681 is perpendicular to the second right angle surface of the first pyramid prism 681, the first right angle surface of the second pyramid prism 682 is perpendicular to the second right angle surface of the second pyramid prism 682, the first right angle surface of the first pyramid prism 681 is parallel to the first right angle surface of the second pyramid prism 682, and the second right angle surface of the first pyramid prism 681 is parallel to the second right angle surface of the second pyramid prism 682. The transmission path of the focusing light beam is adjusted by adjusting the distances of the first angular pyramid prism 681 and the second angular pyramid prism 682 in the direction perpendicular to the principal ray direction of the focusing light beam.
In the embodiment of the invention, each group of the coking patterns on the coking marking plate 611 comprises at least M sub marks, and M is more than or equal to 3. Referring to FIG. 5, the focal plane compensation structure 68 includes N pyramid prism groups 680, where N pyramid prism groups 680 are sequentially aligned in a direction perpendicular to the receiving plane of the imaging unit 66, that is, N pyramid prism groups 680 are sequentially aligned in a direction along the chief ray of the focusing beam, 2.ltoreq.N.ltoreq.M-1. That is, each set of the coking pattern on the coking-marking plate 611 includes at least three sub-marks, and correspondingly, the focal-plane compensation structure 68 may be provided with at least two pyramid prism sets 680 to change the transmission paths of at least two of the reflected light beams, and compensate the focal planes of at least two reflected light beams to the receiving surface of the imaging unit.
Further, at least one group of the focus measurement patterns on the focus measurement mark plate 611 comprises M sub marks, M is greater than or equal to 3, the focus plane compensation structure 68 comprises N pyramid prism groups 680, N=M-1, at this time, the M-1 reflected beams are modulated by the transmission paths through the M-1 pyramid prism groups 680, the focus planes of the M-1 reflected beams are compensated to the receiving plane of the imaging unit 66, and all the focus measurement beams share the focus plane. In other embodiments, one corner cube 680 may also modulate the transmission path of at least two reflected beams, which is not limited by the present invention.
Illustratively, referring to fig. 5, the focal plane compensation structure 68 includes two corner cube sets 680, a first corner cube set 6801 and a second corner cube set 6802, respectively. The distance between the first pyramid prism 681 and the second pyramid prism 682 in the first pyramid prism group 6801 is greater than the distance between the first pyramid prism 681 and the second pyramid prism 682 in the second pyramid prism group 6802. The first reflected light beam L1 'is projected to the first axicon group 6801, and the imaging focal plane modulated by the first axicon group 6801 is coplanar with the imaging focal plane of the third reflected light beam L3'. The second reflected light beam L2' is projected to the second pyramid prism group 6802, the imaging focal plane modulated by the second pyramid prism group 6802 is coplanar with the imaging focal plane of the third reflected light beam L3', and then the imaging unit 66 is further adjusted such that the imaging focal planes of the first reflected light beam L1', the second reflected light beam L2', and the third reflected light beam L3' are both located on the receiving plane of the imaging unit 66.
Optionally, with continued reference to fig. 2, the focal plane measuring device 60 further includes a second illumination beam and a reference mark plate 64, and the optical assembly 63 includes a beam splitting prism 633 and a projection relay lens 631. The reference mark plate 64 includes a reference pattern and the second illumination beam is projected onto the reference mark plate 64 to form a reference beam carrying information of the reference pattern. The reflected light beam passes through the projection relay lens 631, is combined with the reference beam by the beam splitter prism 633, and is projected to the imaging unit 66. Wherein the reference beam is projected onto the imaging unit 66, and a reference image is formed on the imaging unit 66, the reference image being physically separated from the signal image, i.e. the reference image and the signal image do not overlap. The reference image is used to correct thermal offset of the imaging unit 66. In the test process, the reference image and the signal image are imaged together under the same imaging unit 66 (such as a CCD), so that the relative position relationship of the reference image and the signal image under the imaging unit 66 is not changed along with the position change of the imaging unit 66 and the structure thereof, thereby eliminating the structural thermal offset caused by the heating of the imaging unit 66.
Optionally, in an embodiment, the focal plane measuring device 60 further comprises an optical fiber (not shown in fig. 2), and the focusing light source 610 is further configured to provide a second illumination beam, which is projected to the reference mark plate 64 through the optical fiber to form a reference beam. In another embodiment, the focal plane measuring device 60 may further include a reference light source (not shown in FIG. 2) for providing a second illumination beam, the second illumination beam from the reference light source being projected onto the reference mark plate 64 to form a reference beam.
Optionally, referring to fig. 2, the focal plane measuring device 60 further includes a magnification lens 65, and the reflected light beam passes through the magnification lens 65 and then is projected to the imaging unit 66. In the embodiment of the present invention, the focal plane measuring device 60 further includes a magnification lens 65, and the magnification lens 65 can amplify the reflected light beam, so that the light spot is amplified in the signal image acquired on the imaging unit 66, thereby being beneficial to acquiring the vertical height and the inclination of the test sample 50 according to the position of the light spot and the relative positions among the light spots.
Fig. 6 is a schematic diagram of focal plane testing principle provided in the embodiment of the present invention, and referring to fig. 2 and 6, the incident angle of the focal beam on the test sample 50 is α, the magnification of the magnification lens 65 is β, the vertical position change distance of the test sample 50 is dz, and the moving distance of the corresponding light spot on the imaging unit 66 is x, so as to satisfy formula (1):
x＝2·dz·sinα·β (1)
as can be seen from the formula (1), the vertical position of the test sample 50 changes, and the corresponding light spot moves on the imaging unit 66, so that the vertical height of the test sample 50 can be obtained according to the position of the light spot in the signal image obtained by the imaging unit 66.
Optionally, with continued reference to fig. 2, the optical assembly 63 further includes a mirror 632, and the reflected light beam reflected by the test sample 50 is projected onto the mirror 632, and is reflected by the mirror 632 to vertically propagate. In the embodiment of the invention, the optical assembly 63 further comprises a reflector 632, and the reflected light beam reflected by the reflector 632 propagates along the vertical direction, so that the optical elements behind the reflector 632 are sequentially arranged along the vertical direction, and the arrangement difficulty of the optical elements behind the reflector 632 is reduced.
Illustratively, referring to fig. 2, the focal plane measuring apparatus further includes an illumination relay lens 612, and the focusing beam is obliquely projected onto the test sample 50 after passing through the illumination relay lens 612. The focused beam of light projected onto the test sample 50 is denoted as test mark 62. After the test mark 62 is reflected by the test sample 50 and passes through the projection relay lens 631, the pattern formed on the reflecting mirror 632 and the signal image are in an object-image conjugate relationship with respect to the magnification lens 65, and the reference pattern and the reference image are also in an object-image conjugate relationship with respect to the magnification lens 65.
Illustratively, referring to fig. 2, the imaging unit 66 may include a CCD camera, and in particular, the imaging unit 66 may select a linear array CCD camera having a high sampling frequency and a large dynamic range.
Illustratively, referring to FIG. 2, the angle at which the confocal beam is incident on the test sample 50 is greater than 0 and less than 90, and coaxial measurement is achieved by oblique incidence of the confocal beam.
Fig. 7 is a schematic structural diagram of a defect detecting apparatus according to an embodiment of the present invention, and referring to fig. 7, the defect detecting apparatus includes a focal plane measuring device 60 in the foregoing embodiment. The defect detection apparatus further comprises a defect detection unit comprising a defect detection objective 20. The focal point of the first illumination beam is located in the center of the field of view of the defect detection objective 20.
The defect detection device provided by the embodiment of the invention comprises the focal plane measuring device 60 in the embodiment, so that the coaxial measurement of the focal point and the defect detection point is realized, the focal plane control precision is improved, and the defect detection resolution can be further improved. On the other hand, the focal plane compensation structure 68 compensates the focal planes of the plurality of focusing beams to the receiving plane of the imaging unit 66, so that the imaging focal planes of the reflected beams of the sub-marks in the plurality of measured focusing patterns are coplanar and all located on the receiving plane of the imaging unit 66, thereby reducing the sampling difficulty, improving the mark imaging contrast, and improving the accuracy of focal plane measurement.
Optionally, referring to fig. 7, the defect inspection apparatus further comprises a vertical tilt adjustment station 70, the vertical tilt adjustment station 70 being for carrying the test sample 50. The test piece 50 moves with the movement of the vertical tilt adjustment table 70. The control unit 80 is further configured to control a vertical height of the test sample 50 along the optical axis direction of the defect detection objective 20 and adjust an inclination angle of the test sample 50 until the test sample 50 is located within a depth of field of the defect detection objective 20, and the inclination angle of the test sample 50 is smaller than a preset value. In the embodiment of the present invention, the position of the light spot in the signal image may be obtained through the imaging unit 66, when the vertical height or the inclination angle of the test sample 50 along the optical axis direction of the defect detection objective 20 changes, the position of at least one light spot and the relative positions among a plurality of light spots correspondingly change, so that the vertical height and the inclination angle of the current test sample 50 may be obtained according to the position of the light spot in the signal image, and the vertical inclination adjustment table 70 may be controlled to adjust the vertical height and the inclination angle of the test sample 50, so that the test sample 50 is located within the depth of field range of the defect detection objective 20, and the inclination angle of the test sample 50 is also made smaller than the preset value, so that all the test sample 50 is located on the focal plane of the defect detection objective 20, so that the defect detection objective 20 may clearly image the test sample 50, thereby facilitating the subsequent defect detection of the test sample 50.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, and that various obvious changes, rearrangements, combinations, and substitutions can be made by those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.
Claims (9)
1. A focal plane measuring device, comprising: the device comprises a focus measuring light source, a focus measuring marking plate, an optical assembly, an imaging unit, a focus plane compensation structure and a control unit; the focusing light source is used for providing a first illumination light beam which is obliquely incident, the focusing mark plate comprises at least one group of focusing patterns, each group of focusing patterns comprises at least 3 sub marks, and after the first illumination light beam is projected onto the focusing mark plate, the focusing Jiao Tuxing is projected onto the surface of the test sample piece and generates a reflected light beam;
the focal plane compensation structure is positioned on one side of an imaging surface of the imaging unit and is used for changing the transmission path of the reflected light beam, so that the imaging surface of the reflected light beam converged by the optical component is positioned on a receiving surface of the imaging unit, at least one group of signal images are formed, the signal images are in one-to-one correspondence with the measurement Jiao Tuxing, each group of signal images comprises at least 3 sub-patterns, and each sub-pattern is in one-to-one correspondence with a sub-mark in the focus measurement pattern;
the control unit obtains the vertical height of the test sample piece according to the position of at least one sub-pattern;
the focal plane compensation structure comprises at least one pyramid prism group; the pyramid prism group comprises a first pyramid prism and a second pyramid prism, and the connecting line direction of the first pyramid prism and the second pyramid prism is parallel to the receiving surface of the imaging unit;
the first pyramid prism and the second pyramid prism are right-angle prisms, and right-angle surfaces of the first pyramid prism and the second pyramid prism are 45 degrees with the receiving surface of the imaging unit;
the reflected light beam passes through the pyramid prism group and then continuously propagates along the direction of the principal ray of the reflected light beam; and adjusting the transmission path of the reflected light beam by adjusting the distance between the first pyramid prism and the second pyramid prism in the direction perpendicular to the main ray direction of the reflected light beam.
2. The focal plane measurement device of claim 1, wherein each set of the focal length measurement patterns on the focal length measurement mark plate comprises at least M of the sub-marks, M being greater than or equal to 3;
the focal plane compensation structure comprises N pyramid prism groups, wherein the N pyramid prism groups are sequentially arranged along the direction perpendicular to the receiving surface of the imaging unit, and N is more than or equal to 2 and less than or equal to M-1.
3. The focal plane measurement device of claim 1, wherein the focal length measuring mark plate comprises three sets of the focal length measuring patterns, each set of the focal length measuring patterns comprising three of the sub-marks.
4. The focal plane measuring device of claim 1, further comprising a second illumination beam and a reference mark plate, wherein the optical assembly comprises a beam splitting prism and a projection relay lens, the reference mark plate comprises a reference pattern for reducing the influence of the structural change of the focal plane measuring device, the second illumination beam is projected onto the reference mark plate to form a reference beam carrying the information of the reference pattern,
the reflected light beam passes through the projection relay lens, then passes through the beam splitting prism, is combined with the reference light beam, and is projected to the imaging unit.
5. The focal plane measurement device of claim 4, wherein the optical assembly further comprises a mirror, the reflected light beam reflected by the test piece being projected onto the mirror, reflected by the mirror and propagating vertically.
6. The focal plane measurement device of claim 1, further comprising a magnification lens, the reflected light beam passing through the magnification lens and then being projected to the imaging unit.
7. The focal plane measurement device of claim 6, wherein the first illumination beam, after being projected onto the focal length measuring mark plate, forms at least three focal length measuring beams by at least 3 sub-marks in a set of the focal length measuring patterns; the focusing light beams are reflected by the surface of the test sample piece to form at least three reflected light beams, the reflected light beams are converged to the imaging unit after passing through the optical assembly to form at least three groups of signal images, the signal images correspond to the test Jiao Tuxing one by one, and each group of signal images comprises at least three light spots;
the incidence angle of the focusing light beam on the test sample piece is alpha, the magnification of the magnification lens is beta, the vertical position change distance of the test sample piece is d, and the moving distance of the light spot on the imaging unit is x, so that the following conditions are satisfied:
x＝2·dz·sinα·β。
8. defect detection apparatus comprising a focal plane measuring device according to any one of claims 1-7;
the device further comprises a defect detection unit, wherein the defect detection unit comprises a defect detection objective lens, and the focal point of the first illumination beam is positioned at the center of the field of view of the defect detection objective lens.
9. The defect inspection apparatus of claim 8, further comprising a vertical tilt adjustment station for carrying a test specimen;
the control unit is also used for controlling the vertical height of the test sample piece along the optical axis direction of the defect detection objective lens and adjusting the inclination angle of the test sample piece until the test sample piece is positioned in the depth of field range of the defect detection objective lens, and the inclination angle of the test sample piece is smaller than a preset value.
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| CN115046744B (en) * | 2022-08-15 | 2022-11-08 | 之江实验室 | Focal plane detection and inclination adjustment method and device based on SLM (Selective laser melting) generated light spot lattice |
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