KR102425448B1 - Apparatus for generating three-dimensional shape information of an object to be measured - Google Patents

Abstract

An embodiment of the present invention provides a light source unit emitting single-wavelength light, a collimator for collimating the single-wavelength light emitted from the light source unit, and a light splitter for splitting the single-wavelength light passing through the collimator into object light and reference light; an object light objective lens for passing the object light divided by the light splitter, a reference light objective lens for passing the reference light divided by the light splitter, an optical mirror for reflecting the reference light passing through the reference light objective lens, the An interference fringe formed by passing the object light passing through the objective lens and reflected from the surface of the measurement target and the reference light reflected by the optical mirror passing through the object light objective lens and the reference light objective lens, respectively, to the light splitter A processor for receiving and storing an image including intensity information of an object hologram generated by transforming the interference fringes in the image sensor and the image sensor for recording, and generating three-dimensional shape information of the measurement target object; wherein the light source unit emits light of the single wavelength using known step information of the measurement target in a first direction, measurement accuracy in the first direction, and a bit depth of the image sensor. Provided is an apparatus for generating three-dimensional shape information of an object to be measured, in which a wavelength value is determined.

Description

Apparatus for generating three-dimensional shape information of an object to be measured}

The present invention relates to an apparatus for generating three-dimensional shape information of an object to be measured. More specifically, the present invention relates to a three-dimensional (3D) measurement target object from an image including intensity information of an object hologram generated by interference between a reference light reflected from an optical mirror and an object light reflected from or transmitted through the measurement target object. It relates to an apparatus for generating shape information.

The digital holographic microscope refers to a microscope that acquires the shape of an object using digital holography technology.

While a general microscope is a device that acquires the shape of an object by acquiring reflected light that is reflected from an object, a digital holographic microscope is a device that acquires interference and/or diffracted light generated by an object, and acquires the shape of an object therefrom to be.

A digital holographic microscope uses a laser that generates light of a single wavelength as a light source, and uses a light splitter to split the light generated by the laser into two lights. At this time, one light (hereinafter referred to as reference light) is directed toward the image sensor, and the other light (hereinafter referred to as object light) is reflected from the target and directed toward the above-described image sensor, so that interference between the reference light and the object light occurs. do.

The image sensor may record the interference fringe according to the interference phenomenon as a digital image, and restore the three-dimensional shape of the measurement target object from the recorded interference fringe. In this case, the interference fringes recorded by the image sensor are generally referred to as holograms.

The existing optical holographic microscope records the interference pattern according to the interference phenomenon between the reference light and the object light with a special film. At this time, when the reference light is irradiated to the special film on which the interference fringes are recorded, the shape of the virtual measurement object is restored at the location where the measurement object was located.

Compared with the conventional optical holographic microscope, the digital holographic microscope digitizes (or digitizes) the interference fringes of light through an image sensor, and restores the shape of the object to be measured through electronic calculation of the interference fringe information rather than an optical method. There is a difference in

On the other hand, the conventional digital holographic microscope using a single wavelength laser light source has a problem in that the minimum unit length of measurement of an object is limited to the wavelength length of the laser. In order to compensate for this, another conventional digital holographic microscope using a laser light source of two or more wavelengths has a problem in that the manufacturing cost of the microscope is high, and a three-dimensional shape of an object cannot be obtained in real time.

In addition, the above-described conventional digital holographic microscopes generate a computer generated hologram (CGH) with a computer to restore the shape of the object to be measured, and then display it on a spatial light modulator (SLM), and display it on the displayed shape. A three-dimensional holographic image of the object was obtained by illuminating the reference light. However, this method not only requires the use of an expensive spatial light modulator (SLM), but also digitizes the special film in the above-described optical holographic microscope, so the technical limitations are clear.

In order to solve the problems of the conventional digital holographic microscopes, for example, Korean Patent Application Laid-Open No. 10-2016-0029606 (hereinafter referred to as "the published prior art") proposes a digital holographic microscope and a digital holographic image generation method. Hereinafter, a brief look at the disclosed prior art.

2 is a block diagram illustrating in detail a two-wavelength digital holographic microscope apparatus according to the prior art.

Referring to Figure 2, the conventional two-wavelength digital holographic microscope apparatus is a mixed light source unit 10, a wavelength division unit 20, an interference fringe acquisition unit 30, an object unit 40, an image sensor unit 50, It includes an image storage unit 60 , a control unit 70 , and an object shape restoration unit 80 .

The mixed light source unit 10 includes a mixed light source light emitting unit 11 and a light source unit lens 12 . The mixed light source emitting unit 11 emits mixed light having a wavelength band distributed in several bands that are not singular. The light source unit lens 12 optically adjusts the mixed light generated by the mixed light source light emitting unit 11 and makes it incident on the wavelength dividing unit 20 .

The wavelength divider 20 includes a first light splitter 21 , a first filter plate 22 , a second filter plate 23 , and a first reflector 24 . The first light splitter 21 receives the mixed light incident from the mixed light source unit 10 and splits it into two lights. At this time, the first light splitter 21 serves to divide the incident mixed light in different directions to proceed. The first filtering plate 22 obtains a first beam having a predetermined single wavelength by receiving one of the beams divided by the first beam splitter 21 . Here, the light input to the first filtering plate 22 is filtered while passing through the first filtering plate 22 , and a first ray having a single wavelength determined according to the characteristics of the first filtering plate 22 is obtained. The second filter plate 23 receives the other one of the lights divided by the first light splitter 21 in the same manner as the first filter plate 22 , and receives a second light having a wavelength different from the wavelength of the first light beam. get the beam And the second ray is sent to the interference fringe acquisition unit (30). The first reflector 24 serves to receive the first ray obtained from the first filtering plate 22 and reflect it to the interference fringe acquisition unit 30 .

The interference fringe acquisition unit 30 includes a second light splitter 31 , a third light splitter 32 , a second reflector 33 , a third filter plate 34 , and a third reflector 35 . The second beam splitter 31 receives the first beam input from the wavelength splitter 20 and splits it into a first object beam and a first reference beam. At this time, the second beam splitter 31 serves to divide the incident first beam in different directions and propagate it. The third beam splitter 32 also receives the second beam in the same manner as the second beam splitter 31 and splits it into a second object beam and a second reference beam. The second reflector 33 receives the first reference light, and transmits the reflected first reflection reference light to the second light splitter 31 . The third filter plate 34 may receive the first reference light divided by the second light splitter 31 and send it to the second reflector 33 , and may receive the reflected first reflection reference light and send it to the second light splitter. In addition, the third filter plate 34 blocks the progress of the second object light so that it does not reach the second reflector 33 when the light of the second object reaches the second light splitter 31 and is split so that some of the light travels in the direction of the second reflector 33 . . To this end, the third filter plate 34 is a filter plate having the same characteristics as the first filter plate 22 in transmitting light. The third reflector 35 receives the second reference light, and sends the reflected second reference light to the third light splitter 32, where the second reflector 33 and the third reflector 35 are the control unit 70 ) can be configured so that the angle can be adjusted according to the control of an off-axis hologram.

Meanwhile, the first and second object lights obtained as described above are converted into first and second reflecting object lights, respectively, and sent to the image sensor unit 50 through the following process. The second light splitter 31 causes the first object light divided as described above to be incident on the measurement target object mounted on the objective unit 40, and the second object is divided and sent from the third light splitter 32. Light is incident on the measurement target object. In this case, the reflected light reflecting the first object light incident from the measurement target object is referred to as the first reflecting object light. In addition, the reflected light reflecting the second object light incident from the measurement target object is referred to as a second reflecting object light. The second light splitter 31 receives the first and second reflector light reflected as described above and transmits them to the third light splitter 32 . The third light splitter 32 transmits the first and second reflector light received as described above to the image sensor unit 50 again.

In addition, the first reflection reference light and the second reflection reference light obtained as described above are sent to the image sensor unit 50 through the following process. Specifically, the second beam splitter 31 receives the first reflection reference light reflected from the second reflector 33 and sends it to the third beam splitter 32 . As described above, the third light splitter 32 receives the first reflection reference light sent from the second light splitter 31 and the second reflection reference light reflected from the third reflector 35 and receives the image sensor unit 50 again. send to Accordingly, in the third beam splitter 32, the first reflecting object light, the first reflecting reference light, the second reflecting object light, and the second reflecting reference light are all sent in the same direction to the image sensor unit 50, and then mutually interfere with each other. An interference fringe is created.

On the other hand, the second reflector 33 and the third reflector 35 are angled according to the control of the controller 70 to constitute an off-axis system that allows light rays of different wavelengths to form different interference fringes. It is characterized in that it can be adjusted in multiple directions. That is, as the angles of the second reflector 33 and the third reflector 35 are different from each other, the first reflection reference light reflected from the second reflector 33 and the second reference light reflected from the third reflector 35 are different. When the separation occurs in the direction of the light, the first reflection reference light and the second reflection reference light are combined with the first reflection object light and the second reflection object light reaching the image sensor unit 50 to form an interference fringe, each wavelength A different deaxially descaled interference fringe is formed.

The objective unit 40 includes an object holder 41 and an objective lens 42 . The object holder 41 fixes the measurement target object to the holder to be measured, and the objective lens 42 optically adjusts the first object light and the second object light incident on the measurement target object.

The image sensor unit 50 projects the interference fringe obtained by the interference fringe acquisition unit 30 onto a digital image sensor, measures the projected interference fringe using the digital image sensor, and converts the measured value to a discrete signal. convert to In general, a recording of the interference fringe is called a hologram. As such a digital image sensor, various image sensors such as a CCD may be used.

The image storage unit 60 stores the interference fringe information converted into the discrete signal by the image sensor unit 50 in various storage media such as a memory or a disk device.

The control unit 70 implements the above-described off-axis system and controls the positions and angles of the second reflector 33 and the third reflector 35 in order to obtain the interference fringe, such as the interference fringe obtaining unit 30 ) and control the objective unit 40 such as adjusting the objective lens 42 to adjust the first and second object light incident on the measurement target object, and the interference fringe is measured and corresponding to the The image sensor unit 50 is controlled to convert the information into a discrete signal, and the image storage unit 60 is controlled to store the interference fringe information converted into the discrete signal.

The object shape restoration unit 80 includes a phase information acquisition unit 81 , a thickness information acquisition unit 82 , and a shape restoration unit 83 . The phase information acquisition unit 81 obtains phase information of the interference fringe for the first ray and the phase information of the interference fringe for the second ray by using the interference fringe information, respectively, and the thickness information acquisition unit 82 obtains thickness information of the measurement target object using the phase information, and the shape restoration unit 83 restores the real-time three-dimensional shape of the measurement target object using the thickness information. In this case, the thickness information of the object to be measured includes information on the difference between the paths traveled by the object light and the reference light, respectively. Due to the optical path difference between the object light and the reference light, the interference fringe is formed when the object light and the reference light overlap.

According to the disclosed prior art including the above content, it is possible to improve the measurement resolution and secure the real-time of the image acquisition, but still the following problems occur.

In the prior art disclosed first, since a mixed light source having a wavelength band distributed in several bands is used, the wavelength dividing unit 20 divides the first light source and the second light source having different wavelengths to obtain at least two or more single wavelengths. In order to do this, the first filter plate 22, the second filter plate 23, and the first reflector 24 must be used.

In addition, the interference fringe acquisition unit 30 includes a third light splitter 32 for splitting the second light source, a third reflector 35 for reflecting the second light source, and a second light source for the second reflector 33 . The third filter plate 34 to block the incident to the must be additionally used.

Accordingly, the structure of the microscope becomes complicated, which is accompanied by various problems such as an increase in manufacturing cost and an increase in design complexity. Therefore, a new method for solving the above-mentioned problems while using a light source of a single wavelength is required.

Republic of Korea Patent Publication No. 10-2016-0029606 Republic of Korea Patent Publication No. 10-2010-0095302 Republic of Korea Patent Publication No. 10-2012-0014355 Korean Patent No. 10-1139178 Korean Patent No. 10-1441245 U.S. Patent No. 7,649,160

The present invention aims to solve the problems of the prior art as described above, and to accurately generate 3D shape information of an object to be measured by acquiring only one hologram.

In particular, the present invention is to generate three-dimensional shape information of an object to be measured with improved accuracy by generating information about reference light and curvature aberration information of an object light objective lens from one hologram and correcting the obtained object hologram in consideration of this.

In addition, the present invention seeks to solve the problem of complex optical device structures and thus significant high cost.

Furthermore, the present invention intends to detect defects in such structures with high probability by accurately acquiring the three-dimensional shape of ultra-fine structures such as TFTs and semiconductors.

An embodiment of the present invention provides a light source unit emitting single-wavelength light, a collimator for collimating the single-wavelength light emitted from the light source unit, and a light splitter for splitting the single-wavelength light passing through the collimator into object light and reference light; an object light objective lens for passing the object light divided by the light splitter, a reference light objective lens for passing the reference light divided by the light splitter, an optical mirror for reflecting the reference light passing through the reference light objective lens, the An interference fringe formed by passing the object light passing through the objective lens and reflected from the surface of the measurement target and the reference light reflected by the optical mirror passing through the object light objective lens and the reference light objective lens, respectively, to the light splitter A processor for receiving and storing an image including intensity information of an object hologram generated by transforming the interference fringes in the image sensor and the image sensor for recording, and generating three-dimensional shape information of the measurement target object; wherein the light source unit emits light of the single wavelength using known step information of the measurement target in a first direction, measurement accuracy in the first direction, and a bit depth of the image sensor. Provided is an apparatus for generating three-dimensional shape information of an object to be measured, in which a wavelength value is determined.

Another embodiment of the present invention provides a light source unit emitting single-wavelength light, a collimator for collimating the single-wavelength light emitted from the light source unit, and a light splitter for splitting the single-wavelength light passing through the collimator into object light and reference light, After the object light divided by the light splitter passes through the measurement target object, an object light objective lens for passing the object transmitted light including information on the measurement target object, and reflecting the object transmitted light passing through the object light objective lens a second optical mirror, a reference light objective lens passing the reference light divided by the light splitter, a first optical mirror reflecting the reference light passing through the reference light objective lens, the reference light reflected by the first optical mirror, and A second light splitter to which the object transmitted light reflected by the second optical mirror is transmitted, respectively, an image sensor for recording an interference fringe formed by the reference light transmitted to the second light splitter, and the object transmitted light, and the image sensor and a processor for receiving and storing an image including intensity information of an object hologram generated by transforming the interference fringe, and generating three-dimensional shape information of the measurement target object, wherein the light source unit is The measurement target object, wherein the wavelength value of the single wavelength light is determined using step information of the measurement target in a first direction, measurement accuracy in the first direction, and a bit depth of the image sensor A device for generating 3D shape information is provided.

In an embodiment of the present invention, the wavelength value of the single wavelength light satisfies both a first range equal to or greater than a maximum height value among step information of the measurement target object and a second range of the arbitrarily selected measurement accuracy of the image sensor. It may be determined by any one selected from the bit depth candidate group.

In an embodiment of the present invention, the processor extracts real image components corresponding to a real image from among at least one frequency component included in the image, and conjugates with the reference light based on the real image components. conjugate) generating a real image hologram including the correction light and mounting information of the measurement target object, and based on the correction light, an intermediate hologram from which information of the reference light is removed from the real image hologram, the intermediate After generating the curvature aberration correction information from the hologram, based on the curvature aberration correction information, a correction hologram in which an error due to curvature aberration is improved in the intermediate hologram is generated, and from the correction hologram, the 3 Dimensional shape information can be generated.

In one embodiment of the present invention, the processor generates 3D shape information of the measurement target from the intermediate hologram, and the curvature based on the 3D shape information of the measurement target generated from the intermediate hologram At least one parameter for determining the aberration correction information may be determined, and the curvature aberration correction information may be generated based on the parameter.

Other aspects, features and advantages other than those described above will become apparent from the following detailed description, claims and drawings for carrying out the invention.

According to an embodiment of the present invention made as described above, according to the present invention, it is possible to accurately generate three-dimensional shape information of an object to be measured by acquiring only one hologram.

In particular, by generating information about the reference light and curvature aberration information of the objective lens of the object light from one hologram, and correcting the obtained object hologram in consideration of the information, 3D shape information of the measurement target object with improved accuracy can be generated.

In addition, it is possible to solve the problem of complex optical device structures and thus significant high cost.

Furthermore, by accurately acquiring the three-dimensional shape of ultra-fine structures such as TFTs and semiconductors, defects in these structures can be detected with high probability.

Of course, the scope of the present invention is not limited by these effects.

1 is a block diagram showing in detail a two-wavelength digital holographic microscope apparatus according to the disclosed prior art.
2A is a block diagram illustrating a schematic configuration of a holographic restoration apparatus according to a first embodiment of the present invention.
2B is a block diagram illustrating a schematic configuration of a holographic restoration apparatus according to a second embodiment of the present invention.
2C and 2D are block diagrams schematically showing another embodiment of the first embodiment and the second embodiment of the present invention.
3 and 4 are diagrams for explaining a method of determining a condition of light provided from a light source unit.
5A and 5B are diagrams for explaining an external shape of an exemplary measurement target object;
6 is an example of an image of a portion of a measurement target object.
7 is a diagram illustrating a frequency component of an image of a portion of the measurement target shown in FIG. 6 .
FIG. 8 is a diagram for explaining a method of extracting frequency components corresponding to real images from the frequency components shown in FIG. 7 .
9A is a diagram illustrating the intensity of a digital reference light.
9B is a diagram illustrating a phase of a reference light.
9C is a diagram illustrating the intensity of correction light.
9D is a diagram illustrating a phase of a correction light.
10 is a diagram illustrating an exemplary real image hologram.
11 and 12 are diagrams for explaining a method for a processor to determine a curvature aberration correction term from an intermediate hologram according to an embodiment of the present invention.
13 is a diagram illustrating an example of a three-dimensional shape of a measurement target object generated from a hologram.
14 is a flowchart illustrating a method of generating 3D shape information of a measurement target object performed by a holographic restoration apparatus according to an embodiment of the present invention.
15 and 16 are flowcharts of a noise removal method of a holographic restoration apparatus according to embodiments of the present invention.

Hereinafter, various embodiments of the present disclosure are described in connection with the accompanying drawings. Various embodiments of the present disclosure are capable of various changes and may have various embodiments, and specific embodiments are illustrated in the drawings and the related detailed description is described. However, this is not intended to limit the various embodiments of the present disclosure to specific embodiments, and should be understood to include all modifications and/or equivalents or substitutes included in the spirit and scope of the various embodiments of the present disclosure. In connection with the description of the drawings, like reference numerals have been used for like components.

Expressions such as “comprises” or “may include” that may be used in various embodiments of the present disclosure indicate the existence of the disclosed corresponding function, operation or component, and may include one or more additional functions, operations, or components, etc. are not limited. Also, in various embodiments of the present disclosure, terms such as “comprise” or “have” are intended to designate that a feature, number, step, action, component, part, or combination thereof described in the specification is present, It should be understood that it does not preclude the possibility of addition or existence of one or more other features or numbers, steps, operations, components, parts, or combinations thereof.

In various embodiments of the present disclosure, expressions such as “or” include any and all combinations of the words listed together. For example, "A or B" may include A, may include B, or may include both A and B.

Expressions such as “first”, “second”, “first”, or “second” used in various embodiments of the present disclosure may modify various components of various embodiments, but do not limit the components. does not For example, the above expressions do not limit the order and/or importance of corresponding components. The above expressions may be used to distinguish one component from another. For example, both the first user device and the second user device are user devices, and represent different user devices. For example, without departing from the scope of the various embodiments of the present disclosure, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

When a component is referred to as being “connected” or “connected” to another component, the component may be directly connected to or connected to the other component, but with the component It should be understood that other new components may exist between the other components. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it will be understood that no new element exists between the element and the other element. should be able to

The terminology used in various embodiments of the present disclosure is only used to describe one specific embodiment, and is not intended to limit the various embodiments of the present disclosure. The singular expression includes the plural expression unless the context clearly dictates otherwise.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the present disclosure pertain.

Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in various embodiments of the present disclosure, ideal or excessively formal terms not interpreted as meaning

2A is a block diagram showing a schematic configuration of an inspection unit 300A according to the first embodiment of the present invention.

In the present invention, a 'holographic restoration apparatus' may refer to a device that acquires a hologram (hereinafter, referred to as an 'object hologram') for a measurement target object, and analyzes and/or displays the obtained object hologram.

For example, the holography restoration apparatus 300A may be a device that is disposed on a semiconductor manufacturing line, obtains an object hologram of a produced semiconductor, and determines whether the semiconductor is integrity from the obtained object hologram. However, this is an example, and the spirit of the present invention is not limited thereto.

Meanwhile, in the present invention, an 'object hologram' is a hologram that can be generated from an image obtained by the holography restoration apparatus 300A, and may mean a hologram before various processing by the holography restoration apparatus 300A is performed. have. A detailed description thereof will be provided later.

Referring to FIG. 2A , the holography restoration apparatus 300A according to the first embodiment of the present invention includes a light source unit 310 emitting single-wavelength light and a collimator 320 for collimating single-wavelength light emitted from the light source unit 310 . ), a light splitter 330 that splits the single wavelength light passing through the collimator 320 into an object light O and a reference light R, and an object passing the object light O divided by the light splitter 330 The optical objective lens 340, the reference light objective lens 360 that passes the reference light R divided by the light splitter 330, and the optical mirror 370 that reflects the reference light R that has passed through the reference light objective lens 360 ), the object light O reflected from the surface of the measurement target object 350 through the object light objective lens 340 and the reference light R reflected by the optical mirror 370 are respectively transmitted through the object light objective lens 340 ) and the reference light passing through the objective lens 360 and being transmitted to the light splitter 330 to record the image formed by the image sensor 380 and a processor 390 for processing the image acquired by the image sensor 380 may include.

In this case, the processor 390 may generate 3D information of the measurement target object 350 from the image acquired by the image sensor 380 . A detailed description of the operation of the processor 390 will be described later.

2B is a block diagram illustrating a schematic configuration of a holographic restoration apparatus 300B according to a second embodiment of the present invention.

Referring to FIG. 2B , the holography restoration apparatus 300B according to the second embodiment of the present invention includes a light source unit 310 emitting single-wavelength light and a collimator 320 for collimating single-wavelength light emitted from the light source unit 310 . ), a light splitter 330 that splits the single wavelength light passing through the collimator 320 into an object light O and a reference light R, and the object light O divided by the light splitter 330 is the measurement target object After passing through 350 , the object light objective lens 340 that passes the object transmitted light T including the information of the measurement target 350 , and the object transmitted light T that has passed through the object light objective lens 340 is reflected A second optical mirror 372 to let the light pass through, the reference light objective lens 360 passing the reference light R divided by the light splitter 330, and the first reflecting the reference light R passing through the reference light objective lens 360 A second light splitter 332 through which the reference light R reflected by the optical mirror 370, the first optical mirror 370 and the object transmitted light T reflected by the second optical mirror 372 are transmitted, respectively; The image sensor 380 that records an image formed by the reference light R and the object light transmitted light T transmitted to the second light splitter 332, and a processor 390 that processes the image acquired by the image sensor 380 ) may be included.

Of course, even in this second embodiment, the processor 390 may generate 3D information of the measurement target object 350 from the image acquired by the image sensor 380 . A detailed description of the operation of the processor 90 will be described later.

2C and 2D are block diagrams schematically showing another embodiment of the first embodiment and the second embodiment of the present invention.

Referring to FIGS. 2C and 2D , the holographic restoration apparatuses 300A and 300B, which are other embodiments of the first and second embodiments, transmit the light of a single wavelength provided from the light source unit 310 to the inspection unit 100 . It may further include a light transmitter 311 for

Here, the inspection unit 100 refers to an optical configuration of the holographic restoration apparatuses 300A and 300B except for the light source unit 310 and the processor 390 . Specifically, the inspection unit 100 according to the first embodiment includes a collimator 320, a light splitter 330, an object light objective lens 340, a reference light objective lens 360, an optical mirror 370, and an image sensor ( 380 , the inspection unit 100 according to the second embodiment includes a collimator 320 , a light splitter 330 , an object light objective lens 340 , a second optical mirror 372 , and a reference light objective lens 360 . ), a first optical mirror 370 , a second light splitter 332 , and an image sensor 380 . In this case, the inspection unit 100 may omit the collimator 320 by the function of the light transmitter 311 to be described later. The inspection unit 100 is an optical system that forms a path of an object light O and a reference light R for generating an object hologram of an object to be measured. The system will be built with the distance set in advance.

The light transmitter 311 is a configuration for increasing the degree of freedom of the position of the inspection unit 100 , and transmits the light of a single wavelength provided from the light source unit 310 to the inspection unit 100 that is spaced apart from the light source unit 310 . It can perform the function of forwarding. The light transmitter 311 is a flexible light transfer medium, and may be, for example, an optical fiber. When an optical fiber is used as the optical transmitter 311 , the optical fiber 311 performs a function of transmitting light only for a specific wavelength, so that noise of input light transmitted from the light source unit 310 can be removed, may be provided to the inspection unit 100 by expanding the beam size when emitting the . In other words, the optical fiber 311 may replace the function of the collimator 320 , and the inspection unit 100 may omit the collimator 320 if necessary.

The holography restoration apparatuses 300A and 300B of FIGS. 2C and 2D described above are disposed in an in-line deposition system like a semiconductor process, so that the inspection can be performed in real time without the need to take out the inspection object to the outside of the system after deposition. When provided in such an in-line deposition system, in order to minimize interference with the deposition process, only the compact type inspection unit 100 is disposed inside the in-line deposition system, and the bulky light source unit 310 is disposed outside. can be The light transmitter 311 may be installed between the light source unit 310 physically spaced apart from each other and the inspection unit 100 , and may transmit the light provided from the light source unit 310 to the inspection unit 100 .

The object light O is measured by the holography restoration apparatus 300A according to the first embodiment of the present invention and the holography restoration apparatus 300B according to the second embodiment of the present invention, respectively, shown in FIGS. 2A to 2D , respectively. The point that is reflected from the target object 350 (the embodiment of FIGS. 2A and 2C ) or that the object light O transmits through the measurement target object 350 (the embodiment of FIGS. 2B and 2D ) and some configuration thereof It has substantially the same configuration, except for the additional use of elements (eg, the second optical mirror 372 and the second light splitter 332 of the embodiment of FIG. 2B , and thus arrangement of some components).

In particular, it should be noted that the image has the same characteristics in that the image is acquired by the image sensor 380 and the processor 390 generates the reference light R from the acquired image.

Hereinafter, the holography restoration apparatuses 300A and 300B according to the first and second embodiments of the present invention will be collectively referred to as the holography restoration apparatus 300 .

Meanwhile, the processor 390 of the holography restoration apparatus 300 according to an embodiment of the present invention may include any type of apparatus capable of processing data. For example, the processor 390 may refer to a data processing device embedded in hardware having a physically structured circuit to perform a function expressed as a code or an instruction included in a program. The processor 390 may be included in the inspection unit 300 and disposed inside the transfer chambers 201 to 205 , but may be provided as a separate configuration and disposed outside the transfer chambers 201 to 205 .

As an example of the data processing device embedded in the hardware as described above, a microprocessor, a central processing unit (CPU), a processor core, a multiprocessor, an ASIC (Application-Specific Integrated) Circuit) and a processing device such as an FPGA (Field Programmable Gate Array) may be included, but the scope of the present invention is not limited thereto.

Also, the image sensor 380 according to an embodiment of the present invention may be implemented as at least one image sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS).

3 and 4 are diagrams for explaining a method of determining a condition of the light L provided from the light source unit 310 .

Referring to FIGS. 3 and 4 , the light source unit 310 includes known step information of the measurement target 350 in the first direction, the measurement accuracy in the first direction, and the bit depth of the image sensor 380 . (bit depth) may be used to determine the wavelength value of single-wavelength light.

The holographic restoration apparatus 300 generates 3D shape information of the measurement target object 350 including the structures M1 and M2 having a height with respect to the first direction. Here, the first direction may be a direction perpendicular to one surface of the substrate on which the structures M1 and M2 are disposed. Alternatively, the first direction may be a direction in which the object light O is irradiated toward the measurement target object 350 through the object light objective lens 340 .

All types of source devices capable of generating light may be applied to the light source unit 310 , and, for example, a laser capable of irradiating light of a specific wavelength band may be used. The light source unit 310 may use a laser having good coherence to form an interference fringe between the object light O and the reference light R. The light source unit 310 may generate light of a wavelength λ required by the holographic restoration apparatus 300 , and in this case, the wavelength λ may be determined by step information of the measurement target object 350 .

The holography restoration apparatus 300 generates an object hologram by using the interference between the object light O reflected from the surface of the measurement target object 350 and the reference light R, and the coherence that determines the coherence. length) for accurate measurement. In other words, accurate measurement is possible only when the wavelength of the light is longer than the height of the measurement target object 350 . The holographic restoration apparatus 300 extracts the phase information of light from the image including the recorded interference fringes.

At this time, the phase information is expressed in radians. If the wavelength of the light is shorter than the height of the measurement object 350, the phase of the object light O reflected from the surface of the measurement object 350 changes within one period. Accurate measurement is difficult because it is impossible to distinguish whether it is one or a change over one cycle. In other words, when the complex amplitudes of light corresponding to the phase information π/2 and 5π/2 of the image recorded in the image sensor 380 are recorded, since they have the same complex amplitude at π/2 and 5π/2, these two cannot be distinguished. Therefore, the wavelength of the light should be longer than the height of the measurement target object 350 .

Meanwhile, the wavelength value of the single-wavelength light may be determined in a first range greater than or equal to the maximum height value among step information of the measurement target object. As described above, the wavelength of light used for measurement should be longer than the height of the measurement target 350, and as shown in FIG. 3 , the first structure in which the measurement target 350 has a first height t1. In the case of including the second structure M2 having a second height t2 higher than M1 and the first height t1, it should be longer than the second height t2. For example, when the step of the measurement target object is 400 nm to 600 nm, the wavelength value of the single wavelength light may be determined in the range of 600 nm or more. Meanwhile, the light source unit 310 may be selected from a wavelength band (400 nm to 700 nn) of a visible ray region as an embodiment. In this case, the first range C1 of the wavelength value of the single wavelength light may be 600 nm to 700 nm.

)을 2의 n승으로 나눈 값에 비례할 수 있다. 이러한 관계식은 하기 수학식 1로 표현할 수 있다. The light source unit 310 may determine the wavelength value of the single wavelength light by using the measurement accuracy for the first direction and the bit depth of the image sensor. Here, the measurement accuracy means the accuracy with respect to the step of the measurement target object 350 , and may be the resolution of the holography restoration apparatus 300 in the first direction. Measurement accuracy has a correlation between a wavelength value of light generated by the light source unit 310 and a bit depth (n) of the image sensor 380 . Specifically, the measurement accuracy depends on the wavelength (

) divided by 2 to the power of n. This relational expression can be expressed by Equation 1 below.

[Equation 1]

In this case, the wavelength value of the single wavelength light is the bit depth of the image sensor that satisfies both the first range C1 equal to or greater than the maximum height value among the step information of the measurement target 350 and the second range C2 of the arbitrarily selected measurement accuracy. It may be determined by any one selected from the candidate group. As shown in FIG. 4 , in a graph where the x-axis represents wavelength and the y-axis represents measurement accuracy, the measurement accuracy according to wavelength may be represented as a graph of a linear function for each bit depth of the image sensor. The bit depth candidate group of the image sensor may include beep depths passing through an area where the first range C1 and the second range C2 overlap, such as a hatched area in the drawing.

For example, when the measurement accuracy is set in the range of 1 nm to 2 nm, the bit depth n of the image sensor passing through the first range C1 and the second range C2 is 10 bits and 12 bits. . When the bit depth of the image sensor is 10 bits (n=10), the wavelength value of single-wavelength light can be determined by selecting it in the range of 600 nm to 700 nm, and when the bit depth of the image sensor is 12 bits (n=12), single wavelength light The wavelength value of the wavelength light may be determined by selecting it in the range of 650 nm to 700 nm.

5A and 5B are diagrams for explaining the external appearance of an exemplary measurement target object 350 . When the measurement target 350 is the substrate M, deposition materials may be formed on the substrate M along a mask pattern. Since the thin film pattern deposited on the substrate M has a rather complicated shape, the simplified pattern shown in FIGS. 5A and 5B will be exemplified below for convenience of description.

As shown in FIGS. 5A and 5B , the measurement target 350 may include rectangular parallelepiped-shaped structures 51A to 51I arranged at predetermined intervals on one surface. In other words, the measurement target 350 may include the rectangular parallelepiped-shaped structures 51A to 51I protruding in the Z direction on a plane parallel to the X-Y plane.

Hereinafter, the holography restoration apparatus 300 irradiates the object light O in a direction perpendicular to the surface on which the rectangular parallelepiped structures 51A to 51I of the measurement object 350 are arranged, and the image of the measurement object 350 is It is explained on the premise that obtaining .

First, the image sensor 380 according to an embodiment of the present invention may acquire an image of the measurement target object 350 .

In the present invention, the 'image' of the measurement target 350 is intensity information (ie, | (U0(x,y,0)| ² ) may be included, and may be expressed as Equation 2 below.

[Equation 2]

Here, the object hologram Uo(x,y,0) represents the phase information at each x,y point of the measurement object, and x,y are coordinates in the space where the measurement object is placed, which is perpendicular to the object light (O). represents the coordinates defining the plane where O(x,y) and R(x,y) represent object light (O) and reference light (R), respectively, y) represents the complex conjugate of the object light (O) and the reference light (R), respectively.

For example, the image sensor 380 may acquire an image as shown in FIG. 5 for a part of the measurement target 350 shown in FIGS. 5A and 5B (eg, a part including 51A and 51B). can

Since the image acquired by the image sensor 380 includes intensity information at each position of the object hologram U0(x,y,0) as described above, the general image acquired by the image sensor 380 It may be different from the image of the measurement target object 350 (that is, photographed only with the object light O).

Referring to Equation 1, the object hologram (U0(x,y,0)) does not include the object light 0 including the phase information of the measurement object 350 at each point and the phase information of the measurement object. It may be generated by interference of the reference light (R).

In addition, the object hologram U0(x,y,0) includes phase information (ie, height information of the object) at each point (ie, each x,y point) of the measurement target object 350, as well as the object light objective lens 340 ) may further include an error and noise (eg, speckle noise caused by the use of photons of a laser) due to aberration of the laser beam.

Accordingly, the processor 390 according to an embodiment of the present invention may perform various calculation processes as described below in order to remove the above-described error and noise from the image acquired by the image sensor 380 .

The processor 390 according to an embodiment of the present invention may identify frequency components of the image acquired by the image sensor 380 . For example, the processor 390 may check frequency components of the image by performing a 2D Fourier transform on the image.

In other words, the processor 90 calculates the frequency components included in the image including the intensity information (that is, |(U0(x,y,0)| ² ) for each position of the object hologram U0(x,y,0)). In this case, the image may include a frequency component corresponding to a real image, a frequency component corresponding to an imaginary image, and a DC component.

Of course, the image may further include various components in addition to the above three components (a frequency component corresponding to a real image, a frequency component corresponding to a virtual image, and a DC component). For example, the image may further include frequency components due to noise. However, this is an example, and the spirit of the present invention is not limited thereto.

The processor 390 according to an embodiment of the present invention may extract only components corresponding to the real image from among the identified frequency components. In this case, the processor 390 may extract components corresponding to the real image in various ways.

For example, the processor 390 extracts components having a peak value (hereafter, peak components) from among the frequency components included in the image, and includes a peak component corresponding to the real image from among the extracted peak components. Components within the frequency difference of firing may be extracted as components corresponding to the real image.

In this case, the processor 390 may determine the components corresponding to the real image in various ways based on the peak component corresponding to the real image. For example, the processor 90 may determine, among frequency components corresponding to the real image, frequency components in a cross region including a peak component as components corresponding to the real image. In this case, the length of the cross region from the peak component may be determined based on a frequency component corresponding to the real image and a distance difference value between the origin and the corresponding frequency component. For example, this is merely exemplary, and the spirit of the present invention is not limited thereto.

In an optional embodiment, the processor 390 may extract only components corresponding to the real image from among frequency components included in the hologram using an automatic real image spot-position extraction algorithm.

In the present invention, 'extraction' of a specific frequency component may mean extracting the frequency of the corresponding frequency component and the magnitude (or intensity) of the corresponding frequency component.

FIG. 7 is a diagram illustrating a frequency component of an image of a portion of the measurement target 350 shown in FIG. 6 .

As described above, the processor 390 may check the frequency components of the image acquired by the image sensor 380 , and accordingly, the processor 390 generates a frequency component 911 corresponding to the real image and a frequency component corresponding to the virtual image. Various frequency components including a 912 and a DC component 913 can be identified.

In addition, the processor 390 may extract only the frequency component 911 corresponding to the real image from among the identified components. In this case, the processor 390 removes noise from the frequency component corresponding to the real image. Specifically, the processor 390 removes, as noise, a frequency component located in the direction of the interference fringe and the normal direction of the interference fringe, so as to correspond to the real image as shown in FIGS. 8A, 8B, 8C, and 8D, for example. Frequency components in the cross region centered on the peak component may be determined as components corresponding to the real image. At this time, the direction of the cross region is rotated according to the direction of the interference fringe.

The processor 390 according to an embodiment of the present invention may generate a digital reference light from frequency components corresponding to the real image extracted by the above-described process. Looking at this in more detail, the processor 390 may calculate the propagation direction and wave number of the digital reference light based on the frequency components corresponding to the real image. In other words, the processor 390 may calculate the wavenumber vector of the digital reference light.

In addition, the processor 390 generates a digital reference light based on the propagation direction and wavenumber (or wavenumber vector) of the digital reference light, and calculates the conjugate term of the generated digital reference light R(x,y) as in Equation 3 below. It is possible to generate the correction light Rc(x,y).

[Equation 3]

Rc(x,y)= conj[R(x,y)]

In this case, R(x,y) represents the digital reference light generated based on frequency components corresponding to the real image, and Rc(x,y) represents the correction light.

The processor 390 extracts, from the frequency component 911 corresponding to the real image, the normal line of the interference fringe and the direction lines Line1 and Line2 parallel to the interference fringe corresponding to the peak component 911P. The processor 390 determines an area including Line1 and Line2 as noise areas (Noise1, Noise2, Noise3, and Noise4). The processor 390 may extract frequency components distributed in a region excluding the noise region. The processor 90 may extract frequency components corresponding to the real image from which the noise is removed by using a pattern excluding the noise region. As shown in FIG. 8C , the processor 90 may remove noise by using a cross-shaped pattern Pattern1 that excludes frequency components distributed in Line1 and Line2. At this time, the processor 90 generates a cross-shaped pattern Pattern1 based on a certain ratio of the distance difference value between the origin component 913 and the frequency component 911 corresponding to the real image, for example, 1/3 times R. can decide

The processor 90 may set various patterns for removing the noise region. As shown in FIG. 8D , noise of a frequency component corresponding to the real image can be made using a pattern 2 that has a wider width as it approaches the peak component of the frequency component 911 corresponding to the real image.

Since the digital reference light R(x,y) and the correction light Rc(x,y) have a conjugate relationship, the intensity is the same as shown in FIGS. 9A and 9C , and as shown in FIGS. 9B and 9D , Likewise, the phases can be reversed. Here, FIG. 9A is a diagram illustrating the intensity of the digital reference light R(x,y), FIG. 9B is a diagram illustrating the phase of the reference light, and FIG. 9C is a diagram illustrating the intensity of the correction light Rc(x,y). FIG. 9D is a diagram illustrating a phase of correction light.

The generated correction light Rc(x,y) may be used to correct a real image hologram Um(x,y,0), which will be described later.

Meanwhile, the 'digital reference light' is light having the same properties as the reference light R generated by the above-described light splitter 330 from light of a single wavelength, and the processor 390 restores it from the image acquired by the image sensor 380 . It may be a virtual light.

The processor 390 according to an embodiment of the present invention may generate a real image hologram based on frequency components corresponding to the real image extracted by the above-described process. For example, the processor 390 may generate a real image hologram as shown in FIG. 9 by performing an inverse 2D Fourier transform on frequency components corresponding to the real image.

In this case, the actual hologram can be expressed as Equation 4 below.

[Equation 4]

Um(x,y,0)=O(x,y)R*(x,y)

Here, Um(x,y,0) represents the actual hologram, O(x,y) represents the object light (O), and R*(x,y) represents the complex conjugate of the reference light (R).

On the other hand, such a real image hologram Um(x,y,0) includes information about the reference light R and an error due to aberration of the object light objective lens 340 in addition to information about the height of the measurement target 350 . may include

Accordingly, the processor 390 according to an embodiment of the present invention calculates the actual image hologram Um(x,y,0) in consideration of the effect of the reference light R and the error due to the aberration of the object light objective lens 340 . A correction hologram (Uc(x,y,0)) may be generated.

For example, the processor 90 may include a term (Rc(x,y)) for the correction light and a term (Rca(x) for the curvature aberration correction in the real hologram Um(x,y,0)) as shown in Equation 5 below. , y)) to generate a correction hologram (Uc(x,y,0)).

[Equation 5]

Uc(x,y,0)=Um(x,y,0)Rc(x,y)Rca(x,y)

Here, Uc(x,y,0) represents a corrected hologram from which information about the reference light R and aberration information of the object light objective lens 340 are removed, Um(x,y,0) represents a real hologram, Rc(x,y) denotes a term for correction light, and Rca(x,y) denotes a term for curvature aberration correction.

Meanwhile, the processor 390 according to an embodiment of the present invention may generate the term Rca(x,y) for the above-described curvature aberration correction in various ways.

For example, the processor 390 calculates 3 of the measurement target object 350 from the hologram (hereinafter referred to as the intermediate hologram) obtained by multiplying the real hologram (Um(x,y,0)) with only the term Rc(x,y) for the correction light. A 3D shape may be generated, and a term (Rca(x,y)) for curvature aberration correction may be generated from the generated 3D shape.

Looking at this in more detail, the processor 390 may determine at least one parameter for determining the curvature aberration correction term from the three-dimensional shape of the measurement target object 350 generated from the intermediate hologram. In this case, the parameter may include, for example, the coordinates and the radius of the center point defining the hemispherical curved surface.

11 and 12 are diagrams for explaining a method for the processor 390 to determine a curvature aberration correction term from an intermediate hologram according to an embodiment of the present invention.

For convenience of explanation, it is assumed that the image sensor 380 has acquired an image of the cuboid-shaped structure 51D of FIG. 3B and that the processor 390 has generated an intermediate hologram of the structure 51D according to the above-described process. do. It is also assumed that the three-dimensional shape 920 of the structure 51D generated from the intermediate hologram of the structure 51D is as shown in FIG. 10 .

Under the above-mentioned assumption, the processor 390 according to an embodiment of the present invention may determine at least one parameter for determining the curvature aberration correction term from the 3D shape 920 . For example, the processor 390 may determine the coordinates (Cx, Cy) of the center point of the hemispherical curved surface and the radius (r) of the curved surface as parameters from the curve on the I-I section of the three-dimensional shape 920 as shown in FIG. 12 . . At this time, the processor 390 according to an embodiment of the present invention may determine the position and/or direction of the cut surface such that the cut surface, such as the I-I cross-section, includes the center point of the three-dimensional shape 920 (ie, the center point of the hemispherical shape). Also, the processor 390 may determine that a cutting plane such as the I-I cross-section is parallel to the traveling direction of the object light 0 .

The processor 390 according to an embodiment of the present invention may generate (or determine) a curvature aberration correction term based on at least one parameter determined by the above-described process. For example, the processor 390 generates a curved surface in a three-dimensional space with reference to the coordinates (Cx, Cy) of the center point of the curved surface and the radius (r) of the curved surface, and from the generated curved surface to be reflected in the phase correction of each x and y point. A curvature aberration correction term can be generated (or determined) in a manner that generates information.

In an optional embodiment, the processor 390 may determine a correction term from an intermediate hologram of a measurement target object whose shape is known in advance (eg, an object having the same z value in all x and y coordinates).

In the case of a measurement object whose shape is known in advance, since the z value at each x and y point is known in advance, the processor 390 determines the three-dimensional shape of the measurement object generated from the intermediate hologram and the known shape of the measurement object. The correction term may be determined by checking the difference between the z values at each x and y point. However, this is an example, and the spirit of the present invention is not limited thereto.

The processor 390 according to an embodiment of the present invention may generate a three-dimensional shape of the measurement target object 350 based on the correction hologram Uc(x,y,0). In other words, the processor 390 may calculate the height of the object in the z direction at each x and y point.

For example, the processor 90 may convert the corrected hologram Uc(x,y,0) into information on the reconstructed image plane. In this case, the restored image plane means a virtual image display plane as much as a distance corresponding to the distance between the measurement target object and the image sensor by the processor, and may be a virtual plane calculated and simulated by the processor 90 .

The processor 390 may calculate the height of the object in the z direction at the x and y points as shown in FIGS. 13A, 13B, and 13C from the restored information in consideration of the reconstructed image plane. 13A shows the restoration result without removing noise from the frequency component, FIG. 13B shows the restoration result by removing noise using a cross-shaped pattern (Pattern1), and FIG. 13C shows the restoration result by removing noise using Pattern2 . A1, A2, and A3 represent the height values in the Z direction as a flat graph. It can be seen that A1 has a large change in the height value in the z-direction because noise is not removed, and A2 and A3 have little change in the height value in the z-direction.

When a cross-shaped pattern is used, the processor 390 may extract a frequency component according to Equation 5 below.

[Equation 5]

13A, 13B, and 13C illustrate three-dimensional shapes of two rectangular parallelepiped structures 51A and 51B disposed on a measurement target object 350 .

14 is a flowchart illustrating a method of generating 3D shape information of a measurement target object 350 performed by the holographic restoration apparatus 300 according to an embodiment of the present invention. Hereinafter, descriptions of the contents overlapping those described with reference to FIGS. 2 to 13 will be omitted, but will be described with reference to FIGS. 2 to 13 together.

The holographic restoration apparatus 300 according to an embodiment of the present invention may acquire an image of the measurement target object 350 ( S1201 ).

In the present invention, the 'image' of the measurement target 350 is intensity information (ie, | It may include (U0(x,y,0)| ² ), and may be expressed as in Equation 2 above.

For example, the holographic restoration apparatus 300 acquires an image as shown in FIG. 6 for a part (eg, a part including 51A and 51B) of the measurement target 350 shown in FIGS. 5A and 5B . can do.

Since the image acquired by the holography restoration apparatus 300 includes intensity information at each position of the object hologram U0(x,y,0) as described above, the holography restoration apparatus 300 acquires It may be different from the image of a general (ie, photographed only with the object light O) of the measurement target 350 .

Referring to Equation 2, the object hologram (U0(x,y,0)) does not include the object light 0 including the phase information of the measurement object 350 at each point and the phase information of the measurement object. It may be generated by interference of the reference light (R).

In addition, the object hologram U0(x,y,0) includes phase information (ie, height information of the object) at each point (ie, each x,y point) of the measurement target object 350, as well as the object light objective lens 340 ) may further include an error and noise (eg, speckle noise caused by the use of photons of a laser) due to aberration of the laser beam.

Therefore, the holography restoration apparatus 300 according to an embodiment of the present invention may perform the calculation process of steps S1202 to S1207 in order to remove the above-described error and noise from the image acquired by the holography restoration apparatus 300. .

The holography restoration apparatus 300 according to an embodiment of the present invention may check frequency components of an image acquired by the holography restoration apparatus 300 ( S1202 ). For example, the holographic restoration apparatus 300 may perform a 2D Fourier transform on the image to check frequency components of the image.

In other words, the holographic restoration apparatus 300 determines the frequency included in the image including the intensity information (ie |(U0(x,y,0)| ² ) for each position of the object hologram U0(x,y,0)) The components may be checked, and the image may include a frequency component corresponding to a real image, a frequency component corresponding to an imaginary image, and a DC component.

Of course, the image may further include various components in addition to the above three components (a frequency component corresponding to a real image, a frequency component corresponding to a virtual image, and a DC component). For example, the image may further include frequency components due to noise. However, this is an example, and the spirit of the present invention is not limited thereto.

The holographic restoration apparatus 300 according to an embodiment of the present invention may extract only components corresponding to the real image from among the identified frequency components (S1203). In this case, the holographic restoration apparatus 300 may extract components corresponding to the real image in various ways.

For example, the holographic restoration apparatus 300 extracts components (hereinafter, peak components) having a peak value from among the frequency components included in the image, and a peak corresponding to the real image from among the extracted peak components. Components that are within a difference in frequency between the component and the firing may be extracted as components corresponding to the actual image.

In this case, the holographic restoration apparatus 300 may determine components corresponding to the real image in various ways based on the peak component corresponding to the real image. For example, the holographic restoration apparatus 300 may determine frequency components in a cross region centered on a peak component corresponding to the real image as components corresponding to the real image. However, this is an example, and the spirit of the present invention is not limited thereto.

In an optional embodiment, the holography restoration apparatus 300 may extract only components corresponding to the real image from among frequency components included in the hologram using an automatic real image spot-position extraction algorithm.

In the present invention, 'extraction' of a specific frequency component may mean extracting the frequency of the corresponding frequency component and the magnitude (or intensity) of the corresponding frequency component.

Referring back to FIG. 7 , the holography restoration apparatus 300 may check the frequency components of the image acquired by the holography restoration apparatus 300 , and accordingly, the holography restoration apparatus 300 generates a frequency component 911 corresponding to the real image. ), various frequency components including a frequency component 912 and a DC component 913 corresponding to the virtual image can be identified.

Also, the holographic restoration apparatus 300 may extract only the frequency component 911 corresponding to the real image from among the identified components. In this case, the holographic restoration apparatus 300 may determine the frequency components 911B in the cross region centered on the peak component 911A corresponding to the real image as components corresponding to the real image as shown in FIG. 7 .

The holographic restoration apparatus 300 according to an embodiment of the present invention may generate a digital reference light from frequency components corresponding to the real image extracted by the above-described process (S1204). Looking at this in more detail, the holographic restoration apparatus 300 may calculate the propagation direction and wave number of the digital reference light based on frequency components corresponding to the real image. In other words, the holographic restoration apparatus 300 may calculate the wavenumber vector of the digital reference light.

In addition, the holography restoration apparatus 300 generates a digital reference light based on the propagation direction and wavenumber (or wavenumber vector) of the digital reference light, and the generated digital reference light R(x,y) as in Equation 3 above. The correction light Rc(x,y) may be generated by finding the conjugate term.

Since the digital reference light R(x,y) and the correction light Rc(x,y) have a conjugate relationship, the intensity is the same as shown in FIGS. 9A and 9C , and as shown in FIGS. 9B and 9D , Likewise, the phases can be reversed. Here, FIG. 9A is a diagram illustrating the intensity of the digital reference light R(x,y), FIG. 9B is a diagram illustrating the phase of the reference light, and FIG. 9C is a diagram illustrating the intensity of the correction light Rc(x,y). FIG. 9D is a diagram illustrating a phase of correction light.

The generated correction light Rc(x,y) may be used to correct a real image hologram Um(x,y,0), which will be described later.

On the other hand, the 'digital reference light' is light having the same properties as the reference light R generated by the above-described light splitter 330 from light of a single wavelength, and the holography restoration apparatus 300 is obtained by the holography restoration apparatus 300. It may be a virtual light restored from an image.

The holographic restoration apparatus 300 according to an embodiment of the present invention may also generate a real image hologram based on frequency components corresponding to the real image extracted by the above-described process (S1204). For example, the holography restoration apparatus 300 may generate a real image hologram as shown in FIG. 10 by performing an inverse 2D Fourier transform on frequency components corresponding to the real image. In this case, the actual hologram can be expressed as in Equation 3 above.

The holographic restoration apparatus 300 according to an embodiment of the present invention may generate an intermediate hologram in order to generate a term Rca(x,y) for curvature aberration correction (S1205). For example, the holography restoration apparatus 300 may generate an intermediate hologram by multiplying the real hologram Um(x,y,0) by the term Rc(x,y) for the correction light. The generated intermediate hologram may be used to generate curvature aberration correction information in step S1206.

The holography restoration apparatus 300 according to an embodiment of the present invention generates a three-dimensional shape of the measurement target object 350 from the intermediate hologram generated in step S1205, and a term for curvature aberration correction from the generated three-dimensional shape ( Rca(x,y)) may be generated (S1206). Looking at this in more detail, the holographic restoration apparatus 300 may determine at least one parameter for determining the curvature aberration correction term from the three-dimensional shape of the measurement target object 350 generated from the intermediate hologram. In this case, the parameter may include, for example, the coordinates and the radius of the center point defining the hemispherical curved surface.

A method of determining a curvature aberration correction term from an intermediate hologram by the holography restoration apparatus 300 according to an embodiment of the present invention will be described with reference again to FIGS. 11 and 12 . For convenience of explanation, the holography restoration apparatus 300 has acquired an image of the rectangular parallelepiped structure 51D of FIG. 5B, and the holography restoration apparatus 300 obtains an intermediate hologram for the structure 51D according to the above-described process. Assume that you have created It is also assumed that the three-dimensional shape 920 of the structure 51D generated from the intermediate hologram of the structure 51D is as shown in FIG. 11 .

Under the above-mentioned assumption, the holographic restoration apparatus 300 according to an embodiment of the present invention may determine at least one parameter for determining a curvature aberration correction term from the three-dimensional shape 920 . For example, the holographic restoration apparatus 300 determines the coordinates (Cx, Cy) of the center point of the hemispherical curved surface from the curve on the I-I section of the three-dimensional shape 920 as shown in FIG. 12 and the radius (r) of the curved surface as parameters. can At this time, the holography restoration apparatus 300 according to an embodiment of the present invention may determine the position and/or direction of the cut surface such that the cut surface, such as the I-I cross-section, includes the center point of the three-dimensional shape 920 (that is, the center point of the hemispherical shape). . Also, the holographic restoration apparatus 300 may determine that a cut surface such as the I-I cross-section is parallel to the traveling direction of the object light 0 .

The holographic restoration apparatus 300 according to an embodiment of the present invention may generate (or determine) a curvature aberration correction term based on at least one parameter determined by the above-described process. For example, the holographic restoration apparatus 300 generates a curved surface in three-dimensional space with reference to the coordinates (Cx, Cy) of the center point of the curved surface and the radius (r) of the curved surface, and performs phase correction of each x and y point from the generated curved surface. A curvature aberration correction term may be generated (or determined) in a manner that generates information to be reflected.

In an optional embodiment, the holographic restoration apparatus 300 may determine a correction term from an intermediate hologram of a measurement target object whose shape is known in advance (eg, an object having the same z value in all x and y coordinates).

In the case of a measurement object whose shape is known in advance, since the z value at each x and y point is known in advance, the holography restoration apparatus 300 determines the three-dimensional shape of the measurement object generated from the intermediate hologram and the known measurement object. The correction term may be determined by checking the difference in z values at each x and y point of the shape. However, this is an example, and the spirit of the present invention is not limited thereto.

The holography restoration apparatus 300 according to an embodiment of the present invention considers the effect of the reference light R and the error due to the aberration of the object light objective lens 340 to be a real image hologram (Um(x,y,0)) A correction hologram Uc(x,y,0) may be generated from ( S1207 ). For example, as shown in Equation 5 above, the holographic restoration apparatus 300 includes a term for correction light (Rc(x,y)) and a term for curvature aberration correction (Rca) in the real hologram (Um(x,y,0)) as shown in Equation 5 above. By multiplying by (x,y)), a correction hologram (Uc(x,y,0)) can be generated. In this case, the term (Rc(x,y)) for the correction light may be generated in step S1204, and the term (Rca(x,y)) for the curvature aberration correction may be generated in step S1206.

The holographic restoration apparatus 300 according to an embodiment of the present invention may generate 3D shape information of the measurement target object 350 based on the correction hologram Uc(x,y,0) (S1208). In other words, the holographic restoration apparatus 300 may calculate the height of the object in the z direction at each x and y point.

For example, the holography restoration apparatus 300 may convert the corrected hologram Uc(x,y,0) into information on the restored image plane. In this case, the restored image plane means a virtual image display plane as much as a distance corresponding to the distance between the measurement target object and the image sensor by the processor, and may be a virtual plane calculated and simulated by the holography restoration apparatus 300 . .

The holographic restoration apparatus 300 may calculate the height of the object in the z direction at the x and y points as shown in FIG. 13 from the restored information in consideration of the restored image plane. 13 exemplarily illustrates the three-dimensional shape of two rectangular parallelepiped-shaped structures 51A and 51B disposed on the measurement target object 350 .

15 and 16 are flowcharts of a noise removal method of the holographic restoration apparatus 300 according to embodiments of the present invention.

The holographic restoration apparatus 300 according to an embodiment of the present invention may extract only components corresponding to the real image from among the identified frequency components (S1203).

In S12031 , the holography restoration apparatus 300 determines a first frequency component corresponding to the real image included in the image, a second frequency component corresponding to the virtual image, and a third frequency component corresponding to the origin.

In S12032 , the holography restoration apparatus 300 calculates the direction and the normal direction of the interference fringe from the first frequency component, and determines the frequency component located in the direction and the normal direction of the interference fringe as noise.

In S12033, the holography restoration apparatus 300 extracts a frequency component corresponding to the real image by removing the noise from the first frequency component.

In another embodiment, the holography restoration apparatus 300 may set a pattern from which noise is removed and extract a frequency component corresponding to the real image by using the pattern.

In S12034 , the holography restoration apparatus 300 determines a first frequency component corresponding to the real image included in the image, a second frequency component corresponding to the virtual image, and a third frequency component corresponding to the origin.

In S12035, the holography restoration apparatus 300 generates a cross-region pattern including a peak component of the first frequency component. In S12036, the holography restoration apparatus 300 extracts frequency components included in the cross-region pattern from among the first frequency components.

The formula to which the cross region pattern is applied is as follows. The holographic restoration apparatus 300 may extract frequency components included in the cross region pattern according to Equation 7 below.

[Equation 7]

Here, ms is the size of the cross region pattern, xc is the X coordinate of the peak component, and yc is the Y coordinate of the peak component. R is a number proportional to the distance between the frequency component and the origin component corresponding to the real image. For example, R may be distance/3, distance/2, and the like.

The size (ms) of the cross-region pattern is determined based on the distance between the origin component and the frequency component corresponding to the real image, but the size of the cross-region pattern is adjustable in order to efficiently remove the noise component. The size of the cross-region pattern can be optimized through an iterative denoising process.

In another embodiment, in order to more efficiently remove noise, the holographic restoration apparatus 1 may give different weights according to the location of the filtering area through hemispherical filtering. For example, the holographic restoration apparatus 1 may multiply a weight smaller than 1 as it moves away from the center.

[Equation 8]

Here, R refers to a number proportional to the distance between the frequency component and the origin component corresponding to the real image. For example, R may be distance/3 , distance/2 , and the like.

The embodiment according to the present invention described above may be implemented in the form of a computer program that can be executed through various components on a computer, and such a computer program may be recorded in a computer-readable medium. In this case, the medium may be to store a program executable by a computer. Examples of the medium include hard disks, magnetic media such as floppy disks and magnetic tapes, optical image sensors such as CD-ROMs and DVDs, magneto-optical media such as floppy disks, and those configured to store program instructions, including ROM, RAM, flash memory, and the like.

Meanwhile, the computer program may be specially designed and configured for the present invention, or may be known and used by those skilled in the computer software field. Examples of the computer program may include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

As described above, the holographic restoration apparatus 300 according to an embodiment of the present invention, that is, the inspection unit 300, can accurately generate three-dimensional shape information of the measurement target object by acquiring one hologram. . The above-described inspection unit 300 can simplify components while generating accurate three-dimensional shape information through the above-described methods, so that the inspection unit 300 can be disposed inside the in-line deposition equipment to perform real-time inspection on the in-line process. let there be

The specific implementations described in the present invention are only examples, and do not limit the scope of the present invention in any way. For brevity of the specification, descriptions of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connections or connecting members of the lines between the components shown in the drawings exemplarily represent functional connections and/or physical or circuit connections, and in an actual device, various functional connections, physical connections that are replaceable or additional may be referred to as connections, or circuit connections. In addition, unless there is a specific reference such as "essential", "importantly", etc., it may not be a necessary component for the application of the present invention.

Therefore, the spirit of the present invention should not be limited to the above-described embodiments, and the scope of the spirit of the present invention is not limited to the scope of the scope of the present invention. will be said to belong to

300, 300A, 300B: Holographic Restoration Device
310: light source unit
320: collimator
330,332: optical splitter
340: object light objective lens
350: object to be measured
360: reference light objective lens
370,372: optical mirror
380: image sensor
390: processor

Claims (2)

a light source unit emitting single wavelength light;
a collimator for collimating the single wavelength light emitted from the light source unit;
a light splitter for splitting the single wavelength light passing through the collimator into object light and reference light;
an object light objective lens for passing the object light divided by the light splitter;
a reference light objective lens for passing the reference light divided by the light splitter;
an optical mirror for reflecting the reference light passing through the reference light objective lens;
Interference formed when the object light reflected from the surface of the measurement target through the object light objective lens and the reference light reflected by the optical mirror pass through the object light objective lens and the reference light objective lens, respectively, and are transmitted to the light splitter an image sensor that records the pattern; and
A processor configured to receive and store an image including intensity information of an object hologram generated by transforming the interference fringe in the image sensor, and generate three-dimensional shape information of the measurement target object;
The light source unit determines the wavelength value of the single wavelength light using previously known step information of the measurement target in the first direction, measurement accuracy in the first direction, and the bit depth of the image sensor. is decided,
The processor extracts real image components corresponding to a real image from among at least one frequency component included in the image, and based on the real image components, the correction light and the reference light in a conjugate relationship with the reference light; A real image hologram including mounting information of a measurement target is generated, an intermediate hologram from which information of the reference light is removed from the real image hologram is generated based on the corrected light, and curvature aberration correction information is generated from the intermediate hologram. Then, based on the curvature aberration correction information, a correction hologram in which an error due to curvature aberration is removed from the intermediate hologram is generated, and the three-dimensional shape information of the measurement object is generated from the correction hologram. of 3D shape information generating device. The method of claim 1,
The processor generates three-dimensional shape information of the measurement target object from the intermediate hologram, and determines the curvature aberration correction information based on the three-dimensional shape information of the measurement object generated from the intermediate hologram. An apparatus for generating three-dimensional shape information of an object to be measured, determining a parameter and generating the curvature aberration correction information based on the parameter.

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