KR101652355B1 - optical apparatus for examining pattern image of semiconductor wafer - Google Patents

Abstract

An objective optical system placed at a predetermined position with respect to a wafer placed on a table for acquiring a semiconductor device image or a wafer image, an imaging optical system for forming a wafer image obtained by an objective optical system spaced apart from an objective optical system, In the optical wafer inspection apparatus provided with the imaging unit or the image sensing unit, a distance between the imaging optical system and the imaging unit on the actual optical path between the imaging optical system and the imaging unit or a position at which the focus of the imaging optical system is formed is changed And a path changing element capable of changing the path of the wafer. At this time, the path changing element may be a liquid crystal panel or an electrically adjustable mirror.
According to the present invention, since the length of the optical path incident on the imaging unit in the imaging optical system can be arbitrarily adjusted arbitrarily, it is possible to conveniently and arbitrarily change the position of the focus of the inspection object image past the imaging optical system within a certain range. It is possible to easily obtain a plurality of wafer images with different focus positions in the imaging section within a short time, thereby constructing a TSOM image (TSOM image) and comparing the same with the reference TSOM image, And the degree of abnormality can be grasped.

Description

Technical Field [0001] The present invention relates to an optical apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer inspection apparatus, and more particularly, to a wafer inspection apparatus capable of obtaining an image of a wafer portion on which a semiconductor circuit is formed and analyzing the image to check whether a defect exists.

As one method for inspecting wafers, a wafer inspection apparatus for acquiring and inspecting images of a part of a wafer typically irradiates a single wavelength pulse illumination light with a predetermined period to a corresponding region of the wafer, . A field of view (FOV: Field Of View) in which a lens-attached image can be obtained by one pulse illumination is reflected and a reflected light of a target area passes through a lens portion, Once the imaging is performed on the imaging region of the wafer, the wafer moves so that the next imaging region adjacent to the imaging region can be imaged at the next pulse illumination time.

Assuming that the pulse illumination time is very short in order to capture all areas of the wafer, it is assumed that the wafer hardly moves during this time, and the wafer is irradiated during the pulse illumination period by the width of the imaging object area, It must move in the width direction.

Incidentally, the imaging of the imaging target region illuminated by the illumination with one individual imaging element is limited in the capacity of the existing imaging element, so that it takes too much time to inspect the entire wafer and a large imaging element capacity can be used Even though it is not suitable because it takes a lot of time for analysis in a computer system connected to the image sensor and analyzing the image.

Therefore, the entire imaging unit is provided with a plurality of unit imaging elements to form a focal plane array (FPA), thereby increasing the area of the wafer that can be imaged at one time, analyzing each imaging element with one computer, An area sensor type wafer image inspection apparatus is used which reduces the time required for inspection.

However, it is difficult to actually arrange a plurality of unit image pickup elements in close contact with each other in the focal surface array. For example, in addition to a pixel area for receiving an image, each image pickup device must be provided with a row and column lead for fetching an information signal corresponding to an image formed in the pixel area to the outside. In order to install such a lead, Area or installation space is required. Considering such lead wire installation space, it is hard to imagine that the pixel regions of the plurality of imaging elements are arranged in a matrix without a gap.

Therefore, a plurality of unit image pickup elements to be included in a virtual matrix of unit image pickup elements to be arranged on the focal surface of the image pickup area of the wafer are spatially separated from each other in reality, and a video image A method is used in which the image is divided into regions and spatially separated and distributed to the individual imaging elements installed.

The wafer inspection apparatus for performing imaging and image analysis over the whole effective region of the wafer while using the individual image pickup devices spatially divided in this manner and detecting defects thereof is disclosed in Korean Patent Registration No. 1113602 by Negotech Limited And the perspective view of FIG. 1 shows the concept of such a conventional wafer image inspection apparatus.

In such an apparatus, a plurality of unit image pickup elements, that is, two-dimensional detectors 87a, 87c, 87d, 87e and 87f, forming at least one focus surface, and at least one optical element optic element), here, a beam splitter 69 in the form of a glass plate, prisms 89a, 89b and 95, a mirror and the like are used to divide the image of the focus surface.

In such an apparatus, a focus array (FPA: Focal Plane Array) is always used when a plurality of unit image pickup devices are arranged in order to secure an accurate image of a target area. The image other than the focus surface array is always reset which is the subject of setting.

On the other hand, a semiconductor device originally formed a circuit device by integrating circuit elements such as a device and a wire into a small-sized plane, and used a method of continuously reducing the size of devices and conductors in order to increase the degree of integration. However, as the degree of device integration increases, reducing the size of devices and wires has been hampered by various limitations in the process of making semiconductor devices, such as the optical limitations of photolithography processes. In addition, It is in a state that it can import.

In such a situation, in order to increase the device integration degree of the semiconductor device, a three-dimensional device configuration such as the layering of the semiconductor device and the solidification of the device configuration has been searched for.

When a semiconductor device is manufactured through a highly precise and complicated multi-step process step, the inspection work that confirms whether the semiconductor device can perform its function as it is designed according to the design, finds the process defect, corrects the problem, And play a very important role in enhancing effectiveness.

Among the conventional semiconductor device inspection apparatuses, an image inspection apparatus acquires an image of a part of a target semiconductor device, determines whether the image is normal, and checks whether the semiconductor device is defective. The three- The conventional inspecting method of a planar semiconductor device causes a problem that inspections can not be adequately performed.

For example, if the pattern is too small, the illumination beam is difficult to reach through it, and the optical microscope gives meaningful resolution results only when it is larger than half the wavelength size of the light used. In a small pattern inspection such as a semiconductor device inspection, The user can use a method of grouping similar patterns at a certain distance and determining the size by observing how the light is dispersed among the groups. In this method, it is very difficult to measure the new three- There are many difficulties.

Of course, non-optical measurement methods can be considered, but non-optical image processing methods such as scanning probe microscopy are expensive and slow, making it difficult to use them as practical inspection devices.

Recently, the National Institute of Standards and Technology (NIST), Ravikiran Attota et al. Have demonstrated the possibility of measuring three-dimensional fine patterns using a through focus scanning optical microscopy (TSOM) ("TSOM method for semiconductor metrology", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 79710T, April 20, 2011)

This technique uses a conventional optical microscope, but uses a method of creating a three-dimensional image data space for an object by collecting two-dimensional images at different focus positions for the same object. Thus, the resulting two-dimensional images constitute a through-focus image comprising a plurality of in-focus images and out-of-focus images that are out of focus . Computer processing of such a three-dimensional image data space is performed. The computer extracts a brightness profile from a plurality of through-focus images for the same subject being collected and uses the focus position information to create a through-focus scan optical microscope (TSOM) image.

The image provided by the through-focus scanning optical microscope (TSOM) does not represent the object in detail but is slightly abstract, unlike ordinary photographs. However, the difference between the images is inferred from the fine difference in shape of the measured three- .

Through a simulation study, the through-focus scanning optical microscope (TSOM) is known to be capable of measuring characteristics below 10 nanometers and presents possibilities for fine three-dimensional structure shape analysis.

However, it is a time-consuming task to obtain an optical image having a large number of focal points with respect to a very small object, and a method used for actual semiconductor device investigation has not yet been adequately presented.

In Patent Application No. 10-2013-0146941, a semiconductor image obtained through an objective lens is separated by using a splitting optical system such as a beam splitter as shown in FIG. 2, and images are formed on a plurality of unit scratch elements, A semiconductor image inspecting apparatus for causing a phase having a position to be formed is disclosed. In such an inspection apparatus, an image having a plurality of different focal positions can be obtained at substantially the same time, and a TSOM image is obtained by processing these images.

Image processing such as image processing and creation and comparison of TSOM images can be performed using a processing processor and a computer having a built-in program. The image comparing and judging unit of the computer compares the TSOM image with the TSOM image of the normal pattern for the corresponding area already stored in the computer memory to determine whether the pattern defect has occurred in the corresponding unit inspection area.

In this conventional technique, the image processing means includes a plurality of terminals (not shown) for receiving and processing images detected by the unit image pickup device 81 of the image detecting unit and images processed by the terminals, And a master terminal (not shown). When the image processing speed of each terminal is low, an image detected by the unit image pickup device of the image detecting unit is divided into a plurality of paths for faster inspection, The image distributing unit may be further provided.

On the other hand, the pulse period of the laser 30 constituting the illumination light and the moving speed of the wafer 10 in the wafer stage 20 are interlocked with each other so that even when the wafer 10 moves at a constant speed, There is provided a trigger signal generating section 90 for adjusting the moving speed of the wafer 10 on the wafer stage 20 so as to move in the x-axis by the width of the region and to capture the next imaging region accurately by the imaging element.

A signal associated with a video digital signal of the image detecting unit is input to a trigger signal generating unit 90 for operating a wafer stage through a computer or directly from a unit image pickup device to control the moving speed of the wafer, .

That is, the trigger signal generating unit 90 generates a control signal of the laser 30 that provides the driving signal and the illumination light of the wafer stage 20 for transferring the wafer so that the imaging regions projected onto the image detecting unit are not overlapped or missing .

The imaging element may be prepared such that the illumination light shines in the wafer area and the imaging of the wafer is input to the pixel unit without a separate signal, but the imaging can be performed only when the signal comes by the signal synchronized with the illumination . For example, the trigger signal generator 90 provides a caption control signal to the laser 30 and the image detector to provide illumination light to acquire a wafer image.

Accordingly, the position data to which the inspection position is mapped is stored in the lower stage control device, and when the stored mapping data reaches the corresponding position, the imaging signal and the trigger signal for lighting the illumination light of the illumination unit are generated. The generated trigger signal may be configured to generate an accurate synchronizing signal for illumination and image acquisition in the trigger signal generating unit so that the image acquiring signal and the illumination generating signal can be distinguished from each other and output.

However, such an inspection apparatus is complicated in the structure of the apparatus because a plurality of images are obtained by dividing an image into a plurality of images using a splitting optical system and disposing an imaging optical system and an imaging device on a plurality of divided images, Since it is easy to occupy a lot of space and the configuration of the device is complicated, it takes a great deal of effort and effort to set it, and once a setting problem occurs, there may arise a problem that a lot of time and efforts must be repeated again in order to correct the setting again .

Korean Patent Registration No. 10-1113602 Korean Patent Application No. 10-2013-0146941

&Quot; TSOM method for semiconductor metrology ", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 79710T (April 20, 2011)

In the present invention, a plurality of images of different focus positions can be obtained for a small period of time without moving a stage on which a wafer is placed or a lens section for acquiring a wafer image, thereby enabling a through-focus scanning optical microscope (TSOM) Dimensional inspection of a fine pattern of a wafer by performing a three-dimensional inspection of the wafer.

It is an object of the present invention to provide a wafer inspection apparatus capable of judging whether or not a three-dimensional fine pattern of a wafer is defective while basically using an existing optical wafer inspection apparatus, and at the same time, .

An object of the present invention is to provide a wafer inspection apparatus capable of promptly determining whether a three-dimensional fine pattern is defective at a low cost by using an existing optical wafer image inspection apparatus.

According to an aspect of the present invention,

An objective optical system placed at a predetermined position with respect to a wafer placed on a table for acquiring a semiconductor device image or a wafer image, an imaging optical system for imaging a wafer image obtained from the objective optical system and spaced apart from the objective optical system, 1. An optical wafer inspection apparatus comprising an imaging unit or an image sensing unit,

A path changing element is provided between the imaging optical system and the imaging unit so as to change the distance on the substantial optical path between the imaging optical system and the imaging unit or the position where the focus of the imaging optical system is formed by the adjusting unit.

In the present invention, the path changing element may be a liquid crystal panel or an electrically adjustable mirror (deformable mirror).

When a liquid crystal panel is used as a path changing element, a liquid crystal is disposed between two transparent substrates, and a transparent electrode is provided on the inner surface of each transparent substrate. When a voltage applied between two transparent electrodes is changed, The refractive index of the liquid crystal layer is changed by changing the twist angle of the liquid crystal, so that a phase difference or a path difference of light passing therethrough is generated. Accordingly, the actual distance between the imaging optical system and the imaging unit does not change, As shown in FIG.

At this time, the voltage applied between the two transparent electrodes at a specific time is constant with respect to the entire area through which the image of the semiconductor device passes, and the thickness and the refractive index of the liquid crystal layer are made constant.

When a moving mirror is used as a path changing element, a mirror of a light beam including an image of a semiconductor device has a predetermined angle with respect to a mirror so that the mirror reflects light. In the mirror, So that the position of the mirror placed on the piezoelectric body can be easily and adjustably moved in parallel with the axis of the light beam.

According to the present invention, since the length of the optical path incident on the imaging unit in the imaging optical system can be arbitrarily and arbitrarily adjusted, it is possible to conveniently and arbitrarily change the position of the focus of the inspection object image past the imaging optical system within a certain range. It is also possible to shorten the lifting time.

Therefore, according to the present invention, it is possible to conveniently acquire a plurality of wafer images having different focus positions in the imaging unit in a short time, thereby constructing a TSOM image (TSOM image) and comparing the same with the reference TSOM image, The degree of abnormality can be grasped.

As a result, according to the present invention, it is possible to add a path changing element without changing the installation configuration or setting state of the objective optical system, the imaging optical system, and the image pickup section of the existing optical image inspection apparatus, It is possible to obtain an image of the TSOM image of the object to be inspected in a short period of time and judge whether the object to be inspected is abnormal while adjusting it to a desired degree by an adjustable method.

According to the present invention, it is possible to determine whether a three-dimensional fine pattern of a wafer is defective while fundamentally using an existing optical wafer inspection apparatus, thereby reducing equipment cost and accurately determining whether the defect is present within a short time.

1 is a perspective view showing an example of a configuration of a conventional optical wafer image inspection apparatus,
2 is a configuration diagram showing an example of the configuration of another optical wafer image inspection apparatus of the TSOM system,
FIG. 3 is a schematic view showing a configuration of an optical wafer image inspection apparatus according to an embodiment of the present invention,
FIG. 4 is a configuration diagram illustrating a configuration of an optical wafer image inspection apparatus according to another embodiment of the present invention,
Fig. 5 is a conceptual explanatory diagram showing a case where the mirror-surface mounting angle of the moving mirror, which is a path changing element, is changed in the another embodiment of the present invention,
6 is a configuration diagram showing a configuration of a moving mirror as a path changing element used in another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

According to the embodiment of FIG. 3, the wafer 1 on which the semiconductor device to be inspected is formed is seated on the table 220. The table 220 may be movable in three axial directions or in a plane. An objective optical system (objective lens) 230 is spaced apart from the wafer by a focal distance with respect to a normal white plane light and faces the wafer 1. An objective optical system 230 and an objective optical system are disposed on an extension line An imaging optical system (imaging lens) 240 spaced apart from the objective optical system, and an image pickup unit 250, that is, an image pickup device are sequentially positioned. As the imaging element, a charge coupled device (CCD) or a complimentary metal oxide semiconductor (CMOS) imaging element, such as a conventional one, can be used. The imaging optical system 240 is also spaced apart from the imaging element by the focal distance with respect to the white plane wave of the imaging optical system.

Although not shown, images sensed by the imaging device are typically input to a processor of a computer, processed, and automatically processed by a computer program to obtain a TSOM image if a plurality of images with different focus positions are obtained. The thus obtained inspection object, that is, the TSOM image for the semiconductor device in a certain region of the wafer 1, is compared with the reference TSOM image inputted in advance, and the abnormality and the degree of abnormality can be discriminated.

A beam splitter (BS) is positioned between the objective optical system 230 and the imaging optical system 240.

The light source unit 210 includes a light source 211 and a light source optical system 213 that converts light of the light source into parallel light. When a light beam emerging from the light source unit 210 is incident on the beam splitter, a part of the light beam is reflected to illuminate the surface of the wafer through the objective optical system, and the light reflected from the wafer surface again passes through the objective optical system 230, the beam splitter, 240 to the image sensing unit 250. Of course, the light source may emit an object to be inspected through another configuration. In this case, the beam splitter may not be provided.

However, a liquid crystal panel 260 is provided as a path changing element between the imaging optical system 240 and the imaging unit 250.

When the path changing element is the liquid crystal panel 260, a transparent electrode is formed on the inner surface of each of the two spaced apart transparent substrates with a material such as indium tin oxide (ITO) . The distance between the two substrates is constant over the whole, and the thickness of the transparent electrode is also uniformly deposited over the substrate.

When the liquid crystal panel 260 is interposed between the imaging optical system 240 and the image sensing unit 250, the refractive index of the liquid crystal panel section on the optical path is different from that of air, so that the actual distance on the optical path varies. If the voltage applied between the two transparent electrodes is changed, the twist angle of the liquid crystal is changed according to the intensity of the voltage, so that the refractive index of the liquid crystal layer is changed and a phase difference or a path difference of light passing therethrough occurs.

Therefore, even if the interval between the imaging optical system 240 and the imaging section 250 is the same, and the voltage difference applied to the liquid crystal panel 260 is changed even if there is no change in the configuration of the imaging optical system, The focus position at which the light beam including the light beam is formed is also different.

In this configuration, the range of change of the focal position can be changed according to the difference range (maximum difference) between the thickness of the liquid crystal layer and the refractive index of the liquid crystal, and the refractive index of the liquid crystal material and the refractive index depending on the voltage There may be a difference. Therefore, the type of the liquid crystal, the thickness of the liquid crystal layer, and the voltage application range are determined according to the range of change of the calculated focus position so as to acquire images of a plurality of different focal positions for obtaining the TSOM image. The magnitudes of the voltages corresponding to the plurality of different focus positions are calculated and applied to the liquid crystal panel 260.

It takes time to change the arrangement of the liquid crystal according to the voltage change but it is usually adjustable to a few milliseconds (milliseconds: msec), so it is necessary to move and adjust the table with the image pickup unit 250 in the direction of the optical axis by the motor It is possible to change the focal position within a very short time compared to the time. For example, if the voltage is changed to a stepped waveform in a predetermined voltage range within a short time, a plurality of images (optical images of the object to be inspected) having different degrees of focus (different focus positions) are obtained for each voltage magnitude of the step wave, The TSOM image can be obtained by processing the image.

It is also conceivable to install a plurality of liquid crystal panels or to use a multi-layered panel to increase the adjustable focus position range.

4 is similar to the embodiment of FIG. 3 except that the moving mirror 270 or the deformed mirror as shown in FIG. 6 is used as the path changing element provided between the imaging optical system 240 and the imaging unit 250 And the position of the imaging unit 250 is changed according to the use of the moving mirror. In FIG. 6, reference numeral 271a denotes a piezoelectric material, 271b and 271c denote electrodes, 271d denotes a glass layer, 271e denotes a reflection film, and 271f denotes a variable resistor.

More specifically, in this embodiment, a table 220 on which the wafer 1 is placed, an objective optical system (objective lens) 230 spaced apart from the wafer by a focal distance, an imaging optical system (imaging lens) 240 spaced from the objective optical system, Respectively. However, after the imaging optical system 240, a moving mirror 270 is provided. Moving mirrors are generally arranged in the form of a 45 degree reflector, or beam splitter. Therefore, the light beam incident on the moving mirror 270 travels in the direction of 90 degrees, and the image pickup unit 250 is disposed in the traveling direction at a distance from the moving mirror.

The distance on the optical path from the imaging optical system 240 to the optical path reflected by the moving mirror 270 and incident on the imaging unit 250 corresponds to the focal length for the normal light of the imaging optical system 240, ), The voltage is not applied and it is supposed to be in the original position in a flat shape.

Likewise, though not shown, images sensed by the imaging device are typically input to a processor of the computer, processed, and automatically processed by a computer program to obtain a TSOM image if multiple images of different focus positions are obtained.

A light source unit 210 having a beam splitter (BS) positioned between the objective optical system 230 and the imaging optical system 240 and including a light source 211 and a light source optical system 213 for converting light of the light source into parallel light A part of the light beam reflected by the surface of the wafer 1 is reflected by the objective optical system 230 through the objective optical system 230, The beam splitter, the imaging optical system 240, and the moving mirror 270, as shown in FIG.

The moving mirror 270 has a mirror 271 disposed on an object that can change its own thickness or apply pressure to the outside by applying a voltage like a piezoelectric element. When the applied voltage is changed, the position of the mirror 271 For example, 271 ', and a deformable mirror, in which many fine moving mirrors are arranged on a plane to form the entire mirror surface, is also included in the moving mirror.

A deformed mirror is a segmented mirror in which the mirror constituting the whole mirror plane is divided into minute segments and the minute mirror is controlled by the respective actuators. In the segmented mirror type, A continuous thin mirror type in which an actuator is coupled to each fine region under a mirror layer, a membrane mirror type having a common membrane electrode and a control electrode distributed in a fine region, and a wide common electrode on a piezoelectric material layer, A bimorph mirror type in which a control electrode is provided for each fine region and a mirror layer is provided on a piezoelectric material is known. Since the moving amount of the mirror surface is the same in all portions when the same voltage is applied all over the electrode, Can be used.

The light emitted from the imaging optical system 230 is reflected by the moving mirror 270 and enters the imaging unit 250. When the position adjustment factor of the moving mirror 270, that is, the voltage applied to the piezoelectric element, is changed, The entire mirror 271 is moved in the direction of the optical axis in which the entire mirror 271 is incident to become the position 271 'to change the distance on the actual optical path, and the focal point of the imaging optical system 240 is gradually moved from the imaging unit imaging surface to the front or back I can go.

Therefore, in the image sensing unit 250, an image of the inspection object is picked up out of focus, and when the voltage is changed, the inspection object image having a different degree of deviation from the focus can be obtained.

The extent to which the image obtained by the image pickup unit is out of focus depends on the material of the piezoelectric element, the thickness of the piezoelectric element, and the voltage applied to the piezoelectric element. Depending on the angle of the mirror surface with the axis of the light beam, It can be different.

For example, if the mirror 281 faces the direction of the light beam and the imaging surface of the imaging unit 250 is adjacent to the axis of the light beam that is directed from the imaging optical system 240 to the moving mirror 280 as shown in Fig. 5, If the mirror 271 is installed in the direction of 45 degrees with respect to the optical axis of the light as in the embodiment of FIG. 4, A change of the focal position corresponding to the square root of the movement distance of the lens 271 in the optical axis direction is caused.

In the embodiment of Figs. 4 and 5, when the mirror surface moves along the optical axis or along the normal line, the position of the image on the image pickup surface where the image is to be encountered at the image pickup portion can be changed by the change of the focal position, Can be corrected through a program in a computer that receives and processes the image obtained by the image pickup unit, so that no significant problem occurs.

Therefore, even if the positions of the imaging optical system and the imaging unit are not changed, if the voltage difference applied to the piezoelectric element of the moving mirror is changed, the focal position at which the light beam including the image of the semiconductor device passing through the imaging optical system is focused is changed. The distance between the imaging planes becomes different.

Therefore, the type, the thickness, and the voltage application range of the piezoelectric element are determined according to the change range of the calculated focus position so as to acquire images of a plurality of different focus positions for obtaining the TSOM image, and the angle of the mirror surface and the position Also make decisions. Then, the magnitude of the voltage corresponding to a plurality of different focus positions is calculated and applied to the piezoelectric element.

The change of the position of the mirror due to the voltage change can occur very quickly. Therefore, it is possible to change the focal position within a very short time compared to the time taken to move and adjust the table mounted with the imaging unit by the motor in the direction of the optical axis. If the voltage is changed to a stepped waveform in a certain voltage range within a short time, a plurality of images (optical images of the object to be inspected) having different degrees of focus (different focal positions) are acquired for each voltage magnitude of the step wave, The TSOM image can be obtained.

A method of thickening the piezoelectric element to increase the adjustable focus position range or using a thin piezoelectric element in a superimposed manner may be considered.

In the apparatuses of the present invention described above, since the distance on the optical path through the path changing element is changed, the focusing position (focus position) of the focusing optical system changes in the actual space, . An accurate TSOM image is a reference image obtained by obtaining a plurality of out-of-focus images constituting a reference TSOM image (image representing a normal semiconductor device) This can be a TSOM image obtained by obtaining images deviating from a plurality of focuses.

In this case, the path change element refers to the liquid crystal panel and the moving mirror, but any factor that can actually change the path of light through factors that can easily and quickly change the size, such as a voltage change, can be regarded as a path change element.

In the structure of the present invention, imaging is performed on each area while the wafer is moved in a plane by a table (wafer stage) so that inspection can be performed on the entire surface of the wafer. When the table is in one position, In the path changing element, a control device, for example, a voltage applying device for applying voltage to the two electrodes of the liquid crystal panel while changing the voltage or changing the voltage to the piezoelectric element of the moving mirror, A plurality of through focus images including an out of focus image may be obtained by changing the focus or the focus position of the focusing optical system a plurality of times. The control device may be an output terminal of a computer having a necessary processor and a program.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. That is, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

210: light source 220: table (wafer stage)
230: objective optical system 240: imaging optical system
250: image pickup unit 260: liquid crystal panel
270, 280: Moving mirror 271, 281: Mirror

Claims (5)

An objective optical system for acquiring a wafer image, an imaging optical system for forming a wafer image obtained by the objective optical system and spaced apart from the objective optical system, and an imaging unit for forming a wafer image through the imaging optical system, And acquiring a TSOM image for a wafer by picking up images of a plurality of inspection objects having different focal positions in the imaging unit, the optical wafer inspection apparatus comprising:
Wherein a path changing element is provided on the optical path between the imaging optical system and the image pickup unit and the position of the focal point of the imaging optical system is changed by changing the state of the path changing element by an electrical signal, And the plurality of wafer images (through focus images) having different focus positions in the imaging section are held in a state in which the positions of the wafer and the imaging section are fixed by changing the positions of the wafer and the imaging section. The method according to claim 1,
Wherein the path changing element is a liquid crystal panel capable of changing the refractive index of the liquid crystal layer by changing the voltage between the two electrodes with the liquid crystal layer interposed therebetween. The method according to claim 1,
The path changing element is a moving mirror or a deformable mirror that can reflect the light emitted from the imaging optical system and transmit the reflected light to the imaging unit and change the position or shape of the reflecting surface according to a voltage change. Optical wafer inspection apparatus. delete 4. The method according to any one of claims 1 to 3,
Inspection of the entire surface of the wafer can be made as the wafer moves in a plane by the table on which the wafer is placed,
Wherein when the table is in one position, the path changing element changes the position of the focus of the imaging optical system by the adjusting device and the distance between the imaging unit a plurality of times so that a plurality of images including an out of focus image And a through-focus image of the optical wafer is obtained.

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