KR101652356B1

KR101652356B1 - optical apparatus for examining pattern image of semiconductor device

Info

Publication number: KR101652356B1
Application number: KR1020150044515A
Authority: KR
Inventors: 이준호
Original assignee: (주)넥스틴
Priority date: 2015-03-30
Filing date: 2015-03-30
Publication date: 2016-08-31

Abstract

Disclosed is an optical apparatus for examining a wafer, comprising a lighting optical system, an objective optical system, an imaging optical system, and an imaging part or an image detection part. The lighting optical system supplies an illumination light to a wafer. The objective optical system obtains a wafer image. The imaging optical system forms the wafer image obtained by the objective optical system. The imaging part or the image detection part allows the wafer image passing through the imaging optical system to be formed therein. A wavefront deformation element is installed between the objective optical system and the imaging optical system. The optical apparatus for examining a wafer allows the wavefront to be deformed to generate a plurality of wafer images (through focus image) having the position of an examination target object or each different focused position on the imaging part without mechanical movement of the imaging part. The wavefront deformation element may be a liquid crystal panel or a deformable mirror. According to the present invention, the wavefront of a light entering from the examination target object to the image optical system through the objective optical system is deformed to be adjusted by the wavefront deformation element such that longitudinal shift of focus is achieved in accordance with a wavefront aberration theory, thereby obtaining a plurality of wafer images having each different focused position on the imaging part. Accordingly, a through focus scanning optical microscopy (TSOM) image is formed to be compared with a reference TSOM image, thereby determining whether the examination target object has an error and a degree of the error.

Description

Technical Field [0001] The present invention relates to an optical wafer inspection 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.

The applicant's patent application No. 10-2013-0146941 discloses a technique in which a semiconductor image obtained through an objective lens is separated by using a split 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 inspection apparatus is disclosed in which an image having a different focal position is formed. In such an inspection apparatus, an image having a plurality of different focal positions at substantially the same time can be obtained, and these images are processed to obtain a TSOM image.

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)

The present invention allows a plurality of images of different focus positions to be obtained in a short time without moving the stage on which the wafer is placed or the lens section for acquiring the wafer image, thereby enabling a through-focus scanning optical microscope (TSOM) image 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, do.

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 another aspect of the present invention, there is provided a wafer inspection apparatus including an illumination optical system for providing illumination light to a wafer, an objective optical system for acquiring a wafer image (semiconductor device image provided on the wafer) An optical wafer inspection apparatus comprising an imaging optical system, an imaging unit in which a wafer image passed through an imaging optical system is formed, or an image sensing unit,

A wavefront deformation element is provided between the objective optical system and the imaging optical system to deform a wavefront to generate a plurality of wafer images (through focus images) having different focus positions in the imaging section without mechanical movement of the inspection object or the imaging section do.

In the present invention, the wavefront deflection element may be a liquid crystal panel or a deformable mirror. In this case, the wavefront deformation element may be a desired shape of the wavefront change in a certain range by adjusting the voltage of the liquid crystal panel or the movement amount of the deformed mirror in a region receiving the light emitted from the light source through the lens system.

In order to precisely control the wavefront of the wavefront-deforming element in the present invention, a beam separator is provided between the wavefront-deforming element and the imaging optical system to measure the wavefront reflected by the wavefront- And the result can also be used for the wave front deformation element control.

In this case, the wavefront measuring device measures the shape of the wavefront after reflecting or twisting the wavefront deforming element, and a Shack-Hartmann sensor or a curvature sensor can be used. For accurate wavefront deformation control, wavefront deformation elements and closed loops can be constructed.

According to the present invention, a wavefront of light incident on an inspection optical system via an objective optical system to an imaging optical system is adjustably changed by a wavefront deformation element, and a longitudinal shift of focus is performed in accordance with wavefront aberration theory, It is possible to acquire a plurality of wafer images having different focus positions, thereby constructing a TSOM image (TSOM image) and comparing the same with the reference TSOM image, thereby determining the abnormality and abnormality of the object to be inspected.

As a result, according to the present invention, a wavefront deformation element can be further added between an objective optical system and an imaging optical system without changing an installation configuration or setting state of an objective optical system, an imaging optical system, and an imaging unit of a conventional optical image inspection apparatus, The method can easily and rapidly adjust the temperature of the object to be inspected. Thus, it is possible to obtain the image of the TSOM image of the object to be inspected in a short time and judge whether the object to be inspected is abnormal.

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 conceptual diagram illustrating a shape of a deformed mirror according to a magnitude of a voltage applied to a deformed mirror, which is a wavefront deforming element, according to an embodiment of the present invention,
FIG. 5 is a schematic diagram showing a configuration of an optical wafer image inspection apparatus according to another embodiment of the present invention,
6 and 7 are conceptual diagrams showing the configuration of an optical wafer image inspection apparatus of a TSOM system to which a wavefront measuring apparatus is added according to 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 100 on which the semiconductor device to be inspected is formed is seated on a table (wafer stage 120). The table can be moved in three axial directions or in a plane. The objective optical system (objective lens) 130 is spaced apart from the wafer by the focal distance with respect to the normal white plane light and faces the wafer 100. The objective optical system 130 and the objective optical system are disposed on the extension line An imaging optical system (imaging lens: 140) spaced apart from the objective optical system, and an image pickup unit 150, 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. And the imaging optical system is 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 the wafer constant area, is compared with the reference TSOM image inputted in advance, and the abnormality and the degree of abnormality can be discriminated.

A beam splitter 161 is positioned between the objective optical system and the imaging optical system and a wavefront deflection element 135 is located between the beam splitter 161 and the imaging optical system.

Further, an illumination optical system 110 having a light source 111 and a light source lens 113 positioned on the path for transmitting the light of the light source to the objective optical system or wafer is also provided. The driving of the light source, the driving of the table on which the wafer is placed, the operation of the image pickup unit, and the relationship therebetween are well known in the prior art and can be modified as needed, and therefore will not be described in detail here.

When a light beam emerging from the illumination optical system 110 is incident on the beam splitter 161, part of the light is reflected to reflect the surface of the wafer 100 through the objective optical system 130, And reaches the imaging section 150 through the objective optical system 130, the beam splitter 161, the wavefront deforming element 135, and the imaging optical system 140.

The semiconductor device image of the wafer 100 to be inspected in the process is reflected in the image pickup unit 150. When the variation of the wavefront is increased in the plane wave by adjusting the wavefront deformation element 135, The image deviating from the focal point is largely deviated from the original focal position when the wavefront deflection element 135 is absent.

It is possible to convert a plane wave into a spherical wave by applying a voltage that is divided into concentric circular areas in a wavefront deformable element area corresponding to a circular light beam sectional area. The adjustment of each part of the wavefront deforming element can be done in a manner similar to the display controller of various image display devices, and a computer having the required program and processor can serve as the controller. As the wavefront deformation element, a deformed mirror and a liquid crystal panel may be used respectively, or they may be used together.

In this embodiment, when the wavefront deflecting element 135 is a deformable mirror and the cross section of the light beam coming from the objective optical system 130 to the wave deformation element 135 is circular, The voltage is not applied and a larger positive voltage is applied to the periphery and a negative voltage is applied so that the deformed mirror in the corresponding region has a concave mirror or convex mirror shape as a whole and its curvature is changed by the step wave voltage can do.

At this time, the deformed mirror is composed of a plurality of fine mirrors arranged in a matrix form, and each of the fine mirrors is disposed on one or a plurality of piezoelectric elements. When a voltage is applied to each piezoelectric element, It is possible to adjust the positional shift amount or angle with respect to the direction. Generally, a deformed mirror is a micro-mirror in which the mirror constituting the whole mirror surface is divided into micro-zone units, and the micro-mirror is a segmented mirror type in which each actuator is controlled by a mirror, A continuous thin mirror type in which an actuator is coupled to each fine region under the 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 the 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 the piezoelectric material is known.

Assuming the piezoelectric element 210 having a reduced thickness as the voltage is increased, as shown in FIG. 4, the piezoelectric element portion at the center of the corresponding region, as shown in FIG. 4, The voltage is applied to the common electrode 221 through the individual electrode 233 in a state where the common electrode 221 is grounded. In this case, the piezoelectric element 210 is deformed in accordance with the applied voltage for each position, so that the piezoelectric element 210 has a concave shape as a whole.

On the upper side of the piezoelectric element 210, there is a mirror made of a glass layer 220 and a reflection layer 230 on the whole, and the mirror surface also has a concave shape according to the shape of the piezoelectric element.

If the voltage applied to each concentric area is changed so as to become a stepped waveform within a short time within a short time, the curvature of the curved surface formed by the deformed mirror increases accordingly, and the change of the wavefront of the light including the image, Is deepened. As a result, it is possible to obtain a plurality of images deviated from the focus by the respective voltage magnitudes of the step wave, and obtain the TSOM image corresponding thereto.

On the other hand, in the case where the wavefront deflection element is the liquid crystal panel 135 ', the embodiment can have the same configuration as that of FIG. In this embodiment, most of the elements are common to the configuration of FIG. 3, and each of the pixels constituting the liquid crystal panel 135 'may have a configuration in which a fine mirror and a piezoelectric element corresponding to each fine mirror are combined . In each pixel, transparent electrodes are provided on the inner sides of two spaced apart transparent substrates, and the liquid crystal is positioned between the transparent electrodes. In this state, each pixel is arranged in a matrix to form the entire liquid crystal panel 135 '.

However, when 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 path difference of light passing therethrough occurs. Accordingly, when the voltages that enter the liquid crystal panel 135 'at the same time are different from each other depending on the position in the liquid crystal panel 135', the time to depart from the liquid crystal panel 135 'becomes different, and the plane wave becomes a curved surface wave .

Therefore, in the case of the wave front deforming element 135 being such a liquid crystal panel 135 ', instead of applying a voltage to each piezoelectric element in the embodiment using a deformed mirror, a voltage is applied between the transparent electrodes of each fine pixel of the liquid crystal panel The variation of the wavefront deformation factor can be adjusted by changing the degree (size) of applying a voltage with a difference according to the pixel position and putting a difference to the voltage. For example, a portion corresponding to the center of a circular light beam (a circular light beam including a semiconductor image) incident on the liquid crystal panel 135 'is also considered to have a twist angle corresponding to the voltage of the liquid crystal A larger positive voltage is applied or a negative voltage is applied so that the refractive index of the liquid crystal layer in the corresponding region is changed more greatly and the shape of the wavefront of the light beam passing through the liquid crystal layer is changed from a plane wave to a curved surface wave do. The curvature of the curved surface wave can be changed by the voltage of the step wave applied to each pixel of the corresponding part of the light beam of the liquid crystal panel 135 '.

3, the beam splitter 161, the wavefront inspection apparatus 170, and the beam profiler 180 are further provided, and the wavefront inspection apparatus 170 and the beam profiler 180 are further provided. Is reflected in adjusting the wave front deformation element 135. [0064]

More specifically, in the embodiment shown in Fig. 6, the light beam transmitted through the beam splitter 161 in the objective optical system in the configuration shown in Fig. 3 is reflected (may include some scattering) in the wavefront- And the reflected light is incident on the second beam splitter 163 again in the course of proceeding to the imaging optical system 140 and the portion transmitted through the second beam splitter 163 passes through the imaging optical system 140, And the portion reflected by the second beam splitter 163 is input to the Shack-Hartmann sensor as the wavefront inspection device 170. The Shack-

Although not shown here, in some cases, the third beam splitter is again located after the second beam splitter, and the light traveling through the third beam splitter is input to the Shark Hartmann sensor, and the reflected portion is input to a separate beam profiler 180 Configuration can also be considered.

These wavefront inspection devices measure the shape and spread angle of a wavefront of an optical beam including an image so as to grasp the state of a light beam passing through the wavefront deforming device and the movement of the focus position corresponding thereto, If there is a difference from the planned focus position shift, the voltage applied to the piezoelectric element (in the case of a deformed mirror) or the transparent electrode (in the case of the liquid crystal panel) of each part of the wavefront deforming element is controlled to adjust the wavefront deformation So that the focus position movement can be performed.

In such a device, it is possible to confirm the movement of the focus position through a light beam deformed by the actual wavefront through the wavefront deforming element, and to adjust the wavefront deformation factor according to this value, . At this time, an accurate TSOM image is a point at which a plurality of out-of-focus images constituting a reference TSOM image (an image representing a normal semiconductor device) Which is obtained by obtaining an image deviating from a plurality of focuses on the TSOM image.

In theory, in the same configuration as the embodiment of FIG. 3, the adjustment factor of the wavefront deflection element, for example, the voltage is adjusted so as to correspond to the predetermined focal point position. However, due to various factors, I can not. Therefore, in order to obtain a more accurate TSOM image for the object to be inspected, it is more suitable to construct the wavefront as shown in Embodiment 6 so that the wavefront can be directly confirmed and the wavefront can be corrected accordingly.

In the case of using the liquid crystal panel as a wavefront deflection element as in the embodiment of FIG. 5, an additional beam splitter and a wavefront inspection apparatus may be further provided as in the embodiment of FIG. 6 to form an embodiment as shown in FIG.

Although the method of making the TSOM image and the comparison between the fine patterns are not described in detail above, the TSOM obtained by processing optical microscopic images of a plurality of different focal positions on the same three- It is possible to detect a minute difference of several tens of nanometers between two three-dimensional objects by comparing the images. As it is already known in the art of the background of the invention, detailed description thereof will be omitted.

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 wavefront deforming element, the shape of the wavefront or the focal point of the focusing optical system is changed by a voltage regulating device, for example, a voltage applying device that hangs the electrodes of the liquid crystal panel while changing the voltage or by changing the voltage to the piezoelectric device A plurality of through focus images including an out of focus image may be obtained by changing the position where the focus position is changed a plurality of times. The voltage application device may be an output terminal of a computer having a necessary processor and a program.

6 and 7, the wavefront inspection apparatus directly gives a signal to the wavefront deflection element, but in reality, when a computer is intervened and receives a signal from the wavefront inspection apparatus, It would be a common practice for the computer to be delivered as a deformable element, or for the computer to act as a regulator to control the wavefront distortion.

As described above, when a plurality of images having different focus positions are obtained, they can be automatically processed by a computer by a computer program to be used for obtaining a TSOM image, and the inspection object thus obtained, that is, Is compared with the reference TSOM image inputted in advance, so that the abnormality and the degree of abnormality can be discriminated.

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.

110: illumination optical system 111: light source
113: light source lens 120: table
130: objective optical system 135: wavefront deformation element
135 ': liquid crystal panel 140: imaging optical system
150: imaging section 161, 163: beam splitter
170: wavefront inspection apparatus 210: piezoelectric element
220: glass layer 221: common electrode
223: individual electrode 230: reflective layer

Claims

An imaging optical system for acquiring an image of the object to be inspected, an imaging optical system for forming an image of the object to be inspected, which is located at a distance from the objective optical system and is obtained by the objective optical system, and an imaging unit for forming an image of the object to be inspected through the imaging optical system, An optical wafer configured to acquire a TSOM image for an object to be inspected (wafer) by picking up images of a plurality of objects to be inspected whose focal positions are different from each other in the image pickup unit while the focus position of the focusing optical system is different from the relative position between the image pickup unit In the inspection apparatus,
An image wavefront deformation element is provided on the optical path between the objective optical system and the imaging optical system so as to change the position where the focus of the imaging optical system is focused and the relative position between the imaging unit, A plurality of inspection object images (through focus images) having different focus positions in the imaging section in a state in which the inspection object and the imaging section are fixed in position are deformed by a wavefront deformation element to deform the wavefront of the inspection object image obtained in the objective optical system Wherein the optical wafer inspection apparatus comprises:

The method according to claim 1,
Wherein the electrical signal modifies the wavefront of the image of the object to be inspected obtained by the objective optical system by changing physical properties of the material of the image wavefront deformation element.

3. The method of claim 2,
Wherein the image wavefront deformation element comprises a liquid crystal panel through which light can pass,
The liquid crystal panel can change the refractive index of the liquid crystal layer by changing the refractive index of the liquid crystal layer in the region through which the light passes,
And the degree of deformation of the wavefront of the light is adjustable.

3. The method of claim 2,
Wherein the image wavefront modification element comprises a deformable mirror capable of reflecting light,
The deformed mirror can change the position or the angle of the mirror in the region where the light is reflected to change the wavefront of the light,
And the degree of deformation of the wavefront of the light is adjustable.

The method according to claim 1,
Wherein the image wavefront deformation element modifies the wavefront to change the longitudinal focal position of the imaging optical system in accordance with the wavefront aberration theory so that the positions of the inspection object and the imaging unit are fixed, And an image is obtained.

The method according to claim 1,
At least a part of the light having passed through the image wavefront deformation element is input to a beam profiler or a wavefront inspection apparatus to measure a degree of deformation from a plane wave and a result of the measurement is input to the image wavefront deformation element, The optical wafer inspection apparatus comprising:

7. The method according to any one of claims 1 to 6,
The entire surface of the inspection object can be inspected while the inspection object moves on a plane by the table on which the inspection object is placed,
Wherein when the table is in one position, the adjusting means adjusts the distance between the longitudinal focal position of the imaging optical system and the image sensing unit by a plurality of times so that a plurality of images including an out of focus image And the through-focus image of the optical wafer is obtained.