JP2005274161A - Flaw inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flaw inspection device capable of detecting a flaw only of an object layer at the time of inspection of a multilayered specimen. <P>SOLUTION: The flaw inspection device 1 comprises an illumination means equipped with a light source and converting the light flux from the light source to almost parallel light flux to illuminate the specimen having a plurality of layers; an image forming means for branching at least one of the regular reflected light irradiating the specimen and diffracted light into two polarized components mutually crossing at a right angle to form the respective images of the specimen; an imaging means for imaging the respective images formed by the image forming means; and an image processing means for extracting the flaw of one of a plurality of the layers of the specimen from two images taken by the image forming means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a defect inspection apparatus for detecting a defect of an object to be inspected.

  Conventionally, when a substrate such as a semiconductor is manufactured, defects may be formed on the substrate due to various causes. For example, the film thickness unevenness of the resist applied to the substrate surface in the photolithography process, the dust adhering to the resist, the line width defect of the pattern on the substrate after etching, the pinhole in the pattern, etc. Causes defects. In addition, the in-focus failure in pattern exposure causes a defect in formation of a cross-sectional shape of a resist after development, and as a result, causes a failure in a subsequent process.

  As described above, since the defect is a cause of a product defect, a process of detecting a defect on the object such as the substrate and correcting the defect is generally performed. In order to detect the defect, a defect inspection apparatus is generally used.

  For example, Patent Document 1 discloses the conventional defect inspection apparatus. The conventional defect inspection apparatus of Patent Document 1 will be described below with reference to FIG.

  The defect inspection apparatus of Patent Document 1 includes an illumination unit 102 having a light source, and a collimator lens 103 that converts a light beam emitted from the illumination unit 102 into a parallel light beam. The illumination unit 102 and the collimator lens 103 illuminate the subject at an incident angle θi with respect to the normal of the subject surface. The defect inspection apparatus further includes a collimating lens 104, an imaging lens 106, and a line image sensor 107. The collimating lens 104 converges the light beam reflected, diffracted, and scattered by the subject 101 at the inspection angle θ with respect to the normal of the surface of the substrate 101 by the substrate 101 as the subject, and enters the imaging lens 106. Let

  This defect inspection apparatus moves the substrate 101 relative to the defect inspection apparatus in a direction orthogonal to the width direction of the line image sensor 107 (indicated by an arrow AA in FIG. 7). By this movement, the defect inspection apparatus captures the entire substrate 101 and acquires an inspection image.

  In this inspection image, the defect can be observed by the brightness of light reflected by the substrate 101 (reflected light). Specifically, defects such as film thickness unevenness appear as the brightness of the regular reflection light. In addition, defects due to poor focusing are observed as the brightness of the diffracted light. As described above, since the defect is detected by the brightness of the specular reflection light and the diffracted light, the substrate 101 is imaged at a plurality of inspection angles θd so that the substrate 101 can be imaged at the inspection angle θd with the clearest contrast. .

And the some inspection image imaged as mentioned above is compared with the reference image which is the image at the time of imaging the board | substrate which does not have a defect, and the part from which the brightness | luminance of a reference image and an inspection image differs is made into a defect. Extract.
JP-A-9-61365

  In general, a multi-layer pattern is formed on the surface of the substrate 101 by a photolithography process, and a resist layer is formed as an upper layer of these patterns. The conventional defect inspection system is intended to inspect defects in the upper resist layer. However, if there is a defect below the upper resist layer, it detects the lower layer defect at the same time as the upper resist layer defect. End up. For example, when there is uneven thickness in the lower layer, the uneven thickness affects the intensity of the regular reflection light and diffracted light of the irradiated light due to thin film interference with the lower layer including the resist layer. Therefore, in the inspection image, not only the defect of the upper resist layer but also the defect of the lower layer may be exposed as a portion having a different luminance. That is, in the conventional defect inspection apparatus, it may be difficult to detect a defect in the resist layer using the brightness of the reflected light due to the influence of the defect in the lower layer.

  In view of the above problems, an object of the present invention is to provide a defect inspection apparatus capable of detecting defects only in a target layer when inspecting a multilayer object.

  In view of the above problems, the defect inspection apparatus of the present invention has the following configuration.

        A defect inspection apparatus according to an aspect of the present invention includes a light source, and a light beam emitted from the light source is made to be a substantially parallel light beam to illuminate a subject having a plurality of layers, and the subject is irradiated with the illumination unit. At least one of the specularly reflected light and diffracted light of the light beam is branched into two polarization components orthogonal to each other, and an image forming means for forming an image of each subject, and an image formed by the image forming means An image pickup means for picking up each image and an image processing means for extracting a defect in one layer among the plurality of layers of the subject from two images picked up by the image pickup means.

  The present invention can provide a defect inspection apparatus capable of detecting defects in only a target layer when inspecting a multilayer object.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A defect inspection apparatus according to one embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic side view showing a defect inspection apparatus 1 according to the present embodiment. FIG. 2 is a schematic block diagram showing a control system of the defect inspection apparatus 1 in FIG. In addition, the defect inspection apparatus 1 of this Embodiment inspects the multilayer substrate 101 as a subject. Note that a resist layer having a plurality of periodic patterns is formed on the uppermost layer of the substrate 101.

The defect inspection apparatus 1 includes a stage 2, an illumination unit 3, an imaging unit 4, imaging units 7 and 7 ′, and a control system 200.
In the present embodiment, the stage 2 is configured so that the substrate 101 can be sucked and held and moved along the X axis. In the present specification, the X and Z axes substantially coincide with the normal direction of the surface of the substrate 101 supported by the stage 2. In the present embodiment, the stage 2 supports the substrate 101 such that the longitudinal direction of the substrate 101 is parallel to the X axis and the width direction is parallel to the Y axis. In addition, the defect detection apparatus is provided with a not-shown subject transport unit provided with a substrate transport robot that transports a semiconductor wafer substrate or FPD glass substrate to be inspected onto the stage 2. The subject transport unit includes a stocker (cassette) that stores the substrate 101 that is the subject before the inspection, and a stocker (cassette) that stores the substrate 101 after the inspection.

  The illuminating unit 3 is an illuminating unit that illuminates the substrate 101 that is the subject, and includes a light source 31 and a collimating lens 32. The collimating lens 32 shapes the light that has passed through it into linear parallel light. In addition, although the shape of the collimating lens 32 is arbitrary, in this Embodiment, it has the shape cut out by two planes parallel to the optical axis of a spherical lens. The illumination unit 3 is supported by a rotation support unit having a rotation mechanism (not shown) so that an angle (incident angle) θi formed between the optical axis of the collimating lens 3 and the normal line (Z axis) of the substrate 101 can be changed. Yes. The collimator lens 32 illuminates a linear region along the width direction of the substrate 101 that intersects the optical axis.

  The light source 31 is a lighting device having a known configuration, and in the present embodiment, is constituted by a halogen lamp and a fiber bundle, and the emission end of the fiber bundle is supported by the rotation support portion. The light source 31 and the exit point, that is, the exit end of the fiber bundle are arranged on the focal point of the collimating lens 32. The illumination unit 3 illuminates linear illumination light in the width direction (Y direction) of the substrate 101 by the light source 31 and the collimator lens 32 described above. In the present specification, an area illuminated by the illumination unit 3 is defined as an illumination area.

The imaging unit 4 includes a collimating lens 41, a polarizing beam splitter 42, imaging lenses 43 and 43 ′, and imaging units 7 and 7 ′.
The imaging unit 4 is supported by a rotation support unit having a rotation mechanism (not shown) so that an angle (inspection angle) θd formed by the optical axis of the collimating lens 41 and the normal line (Z axis) of the substrate 101 can be changed. ing. The collimating lens 41 guides light (regular reflection light, diffracted light, diffused light, etc.) generated from the illumination area of the substrate 101 to the polarization beam splitter 42.

  The polarization beam splitter 42 is disposed on the optical axis of the collimating lens 41 and branches the light beam from the collimating lens 41 into two polarization components (p-polarized light and s-polarized light) orthogonal to each other. The polarization beam splitter 42 guides the branched polarization components to the imaging lenses 43 and 43 '. The imaging lenses 43 and 43 ′ are arranged on the respective optical paths of the polarization beam splitter 42, and the entrance lenses of the imaging lenses 43 and 43 ′ are arranged at a substantially focal position of the collimating lens 41. The imaging lenses 43 and 43 ′ image the light flux from the collimating lens 41 on the corresponding imaging units 7 and 7 ′.

  The imaging units 7 and 7 ′ are known imaging devices, and are line image sensors in the present embodiment. The imaging units 7 and 7 ′ capture images by the corresponding imaging lenses 43 and 43 ′. The imaging units 7 and 7 ′ are connected to the control system 200, and send captured images to the control system 200. With the above configuration, the defect inspection apparatus 1 can illuminate the substrate 101 at an arbitrary incident angle θi by rotating the illumination unit 3. Further, the defect inspection apparatus 1 can set an arbitrary inspection angle θd by rotating the imaging unit 4 and can capture the light generated at the inspection angle θd in the illumination region by the imaging units 7 and 7 ′. The imaging unit 7 captures an image of the illumination region with one polarization component (for example, S-polarized light) that has passed through the polarization beam splitter 42, and the imaging unit 7 ′ uses the other polarization component reflected by the polarization beam splitter. An image of the illumination area may be taken.

  Next, the control system 200 will be described with reference to FIG. In FIG. 2, only the imaging unit 7 is shown as the imaging unit connected to the control system 200 in order to simplify the drawing. The imaging unit 7 ′ is also connected in the same manner as the imaging unit 7.

  The control system 200 includes a stage control unit 201, a drive circuit 202, an optical system control unit 203, a substrate transport control unit 204, an image interface (image I / F) 205, an image processing device 206, a monitor 207, 210, an image storage device 208, a host computer 209, a keyboard 211, a memory 212, and a sequencer 213.

The stage control unit 201 is connected to the stage 2 and controls the driving of the stage 2.
The drive circuit 202 is connected to the imaging units 7 and 7 ′, and controls the driving of the imaging units 7 and 7 ′ in synchronization with the control of the stage control unit 201.
The optical system control unit 203 is connected to the illumination unit 3 and the imaging unit 4 and controls the driving thereof. More specifically, the optical system control unit 203 controls the light amount and position of the illumination unit 3, and controls the angles (incident angle θi and inspection angle θd) of the illumination unit 3 and the imaging unit 4 with respect to the substrate. .

The substrate transport control unit 204 is connected to the above-described subject transport unit, and controls the driving of the subject transport unit.
The image I / F 205 is connected to the imaging units 7 and 7 ′ and the image processing device 206. The images acquired by the imaging units 7 and 7 ′ are transferred to the image processing device 206 via the image I / F 203.

The image processing device 206 performs image processing on the images acquired by the imaging units 7 and 7 ′, and creates an inspection image to be described later. Note that the image processing apparatus 206 is connected to the host computer 209, and the drive is controlled by the host computer 209. The image processing apparatus 206 extracts defects such as in-focus defects from the inspection image under the control of the host computer 209. Further, the image processing apparatus 206 sends defect-free data such as the type, number, position, and area of defects related to the extracted defects to the host computer 209.
In the present embodiment, the imaging units 7 and 7 ′ are line image sensors. For this reason, the image processing apparatus 206 reconstructs the image for each line sent from the imaging units 7 and 7 ′, and creates two inspection images corresponding to the imaging units 7 and 7 ′. The image processing device 206 is further connected to a monitor 207 and an image storage device 208.

A monitor 207 is an image display device that displays a processed image and an inspection image created by the image processing device 206.
The image storage device 208 is a data storage device that stores processed images and inspection images.

  The host computer 209 is connected to the image processing device 206, the monitor 210, the keyboard 211, the memory 212, and the sequencer 213. The host computer 209 controls driving of the image processing apparatus 206 and the sequencer 213, and displays a control menu on the monitor 210 with necessary settings for this control.

  The keyboard 211 is an input device for inputting commands and information necessary for the control menu and / or other controls to the host computer 209.

  The memory 212 is a storage unit that stores control information necessary for the control. The control information includes, for example, examination conditions (such as optical system settings, examination areas, and image processing conditions) for each type of specimen, examination data, and a subject that has the same configuration as the subject and has no defects. A reference image obtained by imaging the image, a defect determination criterion for determining a product defect, a command and information input from the keyboard, and the like.

  The sequencer 213 is connected to the stage control unit 201, the drive circuit 202, the optical system control unit 203, and the substrate transfer control unit 204, and sends a drive sequence to be controlled to be controlled by them. Also, the sequencer 213 sends a drive command from the host computer 209 to them.

Below, operation | movement of the defect inspection apparatus 1 of the said structure is demonstrated.
When the defect inspection apparatus 1 inspects the substrate 101 that is the subject, first, the user inputs the type of the substrate 101 and an instruction to start inspection from the keyboard 211. When these are input, the host computer 209 acquires the inspection conditions corresponding to the corresponding substrate 101 from the inspection conditions (recipe) of the control information in the memory 212 based on the type of the input substrate 101. After acquiring the inspection conditions corresponding to the substrate 101, the host computer 209 issues a control command to the optical system control unit 203 via the sequencer 213 based on the acquired inspection conditions. Upon receiving the control command, the optical system control unit 203 performs settings for the illumination unit 3 and the imaging unit 4 according to the acquired inspection conditions. In the present embodiment, the defect inspection apparatus 1 performs defect detection on the resist layer of the substrate 101.

  Further, the host computer 209 issues a drive command to the substrate transfer control unit 204 and the stage control unit 201 via the sequencer 213 before, during, or after the acquisition of the inspection conditions. Upon receiving this drive command, the substrate transport control unit 204 drives the subject transport unit to take out one substrate 101 from the stocker and place it on the stage 2. Further, when the substrate 101 is placed on the stage 2, the stage 2 sucks and holds the substrate 101 and performs alignment with the illumination unit 3 and the imaging unit 4 under the control of the stage control unit 201. .

  In this way, setting of inspection conditions corresponding to the substrate 101 and alignment of the substrate 101 are performed. After these operations are performed, the host computer 209 outputs an imaging start command to the stage control unit 201, the drive circuit 202, and the optical system control unit 203.

  The stage 2 moves the substrate 101 at a constant speed along the X axis in accordance with an imaging start command. Further, in synchronization with the movement of the stage 2, the driving circuit 202 captures an image line by line by the imaging units 7 and 7 ′, and the image data is processed through the image I / F 205. Transfer to device 206. The imaging operation of the stage 2 and the imaging units 7 and 7 ′ is set so that the entire surface of the substrate 101 can be inspected, and is completed when the substrate 101 is imaged over the entire surface.

  After the imaging operation is completed, the image processing apparatus 206 subsequently checks the P-polarized component and S-polarized component inspection images corresponding to the imaging units 7 and 7 ′ from the image data transferred from the image I / F 205. Create These two inspection images are images having a luminance distribution reflecting the structure of the resist layer on the surface of the substrate 101 and the underlying layer. Since these two inspection images are images picked up with different polarization components, they have different luminance distributions reflecting the above structure. This is because the reflectivity at the interface and the average refractive index of the periodic pattern change depending on the direction of polarization.

  For example, the inspection image is formed as shown in FIGS. 3 and 4 for each different deflection component. In FIG. 3 and FIG. 4, a region A1 is a region other than a defect. Regions A2 and A3 are regions that show defects. The region A3 is a region showing a defect in the uppermost resist layer in the substrate 101, and has substantially the same luminance value in FIGS. On the other hand, the regions A1 and A2 have luminance values that are substantially reversed in brightness in FIGS. 3 and 4 due to changes in reflectance and the like depending on the deflection direction.

  Subsequently, the image processing apparatus 206 combines the two inspection images to form a combined inspection image used for defect inspection. Specifically, the composite inspection image is formed by combining the luminance values of the dots at positions corresponding to each other in the two inspection images. Note that, as described above, the resist layer defects in the two inspection images have substantially the same luminance value, and the other areas have luminance values in which the brightness is substantially inverted. . Therefore, as shown in FIG. 5, the formed combined inspection image is formed so that the defect of the resist layer to be inspected and the other areas have different luminances.

  After the composite inspection image is formed in this way, the host computer 209 issues a defect inspection command to the image processing apparatus 206. Upon receiving the defect inspection command, the image processing device 206 acquires the reference image from the memory 212. Subsequently, the image processing apparatus 206 compares the composite inspection image with the reference image, and extracts a defect. By this extraction, the image processing apparatus 206 acquires defect-related data such as the position, area, and type of the defect, and sends the defect-related data to the host computer 209.

  When the host computer 209 acquires the defect-related data, the host computer 209 compares the data with the defect determination criteria in the control information to determine whether the substrate 101 is good or bad. After this determination, the subject transport unit classifies the substrate 101 according to the above determination and stores it in the stocker. In this way, the inspection of the substrate 101 ends.

In this way, the defect inspection apparatus 1 according to the present embodiment sequentially inspects the substrate 101.
In the defect inspection apparatus 1 of the present embodiment, as shown in the above configuration and operation, the polarization beam splitter 42 converts at least one light regularly reflected and diffracted from the subject into two polarization components orthogonal to each other. Can be split into light. At the same time, the defect inspection apparatus 1 can capture respective images formed by the light beams of two polarization components orthogonal to each other branched as described above. That is, the defect inspection apparatus 1 can acquire two inspection images with different P-polarized light components and S-polarized light components for one inspection region. Note that, in these inspection images, only the defect of the layer to be inspected is represented by substantially the same luminance value due to the difference in the characteristics of the polarization components. As a result, the defect inspection apparatus 1 can extract only defects in the upper resist layer without being affected by defects in the lower layer by using inspection images of different polarization components.

  Further, the image processing apparatus 206 can combine two inspection images having different polarization components to form one combined inspection image. As a result, it is possible to obtain one composite inspection image obtained by extracting only defects in the layer to be inspected. Therefore, the defect can be detected more easily.

  Further, the image processing device 206 can acquire the reference image and compare the reference image with the composite inspection image. Thereby, the image processing apparatus 206 can acquire the defect related data such as the type of each defect by this comparison.

  Further, the image processing apparatus 206 can form a combined inspection image by combining the luminance values of the dots at positions corresponding to each other with the inspection images having different polarization components. As a result, the regions other than the defects in the resist layer have the brightness values inverted, so that the luminance values are averaged, and the luminance values become substantially uniform. Further, since the defect of the upper resist layer to be inspected has substantially the same luminance value in the inspection images of two different polarization components, the two resist images can be synthesized by combining the two inspection images. The luminance value of the defect increases with respect to other regions, and the defect can be detected more easily.

  Note that the defect inspection apparatus 1 of the present embodiment can arbitrarily change the illumination angle θi and the inspection angle θd. For this reason, the defect inspection apparatus 1 can detect the defect of the resist layer more reliably without being influenced by other layers by arbitrarily changing at least one of the illumination angle θi and the inspection angle θd.

  Moreover, although the defect inspection apparatus 1 of this Embodiment extracted the defect of the uppermost layer of the board | substrate 101, it extracts only the defect of another layer by changing illumination angle (theta) i and inspection angle (theta) d arbitrarily. Things are possible. That is, the defect inspection apparatus 1 can detect a defect in any layer to be inspected without affecting the defects in other layers.

  Further, as shown in FIG. 1, the defect inspection apparatus 1 according to the present embodiment branches the light beam that has passed through the collimator lens 41 into different polarization components by the polarization beam splitter 42 of the imaging unit 4. . However, in the defect inspection apparatus 1 according to the present embodiment, the branching for each polarization component can also be realized with configurations other than those described above. For example, the defect inspection apparatus 1 ′ in FIG. 6 realizes this by using a half mirror 108 and polarizing plates 109 and 109 ′. Specifically, the half mirror 108 is an optical element that is disposed on the optical axis of the collimating lens 41 and branches the light beam from the collimating lens 41 into two. Each of the polarizing plates 109 and 109 ′ is disposed on an optical path branched by the half mirror 108, and is set to transmit polarized components orthogonal to each other. Thereby, the defect inspection apparatus 1 ′ in FIG. 6 branches at least one light beam specularly reflected and diffracted from the subject by the half mirror 108, and after the branching by the polarizing plates 109 and 109 ′. The polarization directions of the light beams can be made orthogonal to each other. Thus, it is not necessary to branch light from the substrate 101 and set the polarization direction of the light beam after branching with one optical member. Therefore, the defect inspection apparatus 1 ′ is similar to the defect inspection apparatus 1 in FIG. 1 by the half mirror 108, which is an optical element having a wider effective wavelength band than the polarizing beam splitter, and the polarizing plates 109 and 109 ′. An imaging unit having a function can be configured.

  Note that the defect inspection apparatus 1 according to the present embodiment arbitrarily configures the imaging unit as long as the light from the substrate 101 can be branched into two polarization components and imaged by the corresponding imaging units 7 and 7 ′. Can change.

  Although several embodiments have been specifically described so far with reference to the drawings, the present invention is not limited to the above-described embodiments, and all the embodiments performed without departing from the scope of the invention are not limited thereto. Including implementation.

FIG. 1 is a schematic side view showing a defect correcting apparatus according to an embodiment of the present invention. FIG. 2 is a schematic block diagram showing a control system of the defect correcting apparatus in FIG. FIG. 3 is a schematic diagram showing one of the two original images. FIG. 4 is a schematic diagram showing the other of the two original images. FIG. 5 is a schematic diagram showing an inspection image formed by two original images. FIG. 6 is a schematic side view showing a modification of the defect correcting device according to the embodiment of the present invention. FIG. 7 is a schematic perspective view showing a conventional defect correcting apparatus.

Explanation of symbols

  θi ... illumination angle; θd ... inspection angle; A1, A2, A3 ... area; 1, 1 '... defect inspection device; 2 ... stage; 3 ... illumination part; 4 ... imaging part; DESCRIPTION OF SYMBOLS 31 ... Light source; 32 ... Collimating lens; 41 ... Collimating lens; 42 ... Polarizing beam splitter; 43, 43 '... Imaging lens; 101 ... Substrate; 108 ... Half mirror; 109, 109' ... Polarizing plate; 201 ... Stage control unit; 202 ... Drive circuit; 203 ... Optical system control unit; 204 ... Substrate transport control unit; 205 ... Image interface; 206 ... Image processing device; 207, 210 ... Monitor; ... Host computer; 211 ... Keyboard; 212 ... Memory; 213 ... Sequencer

Claims (5)

An illuminating unit that includes a light source, illuminates a subject having a plurality of layers by making a light beam from the light source into a substantially parallel light beam,
Imaging means for branching at least one of the specularly reflected light and diffracted light of the light beam applied to the subject into two polarized components orthogonal to each other, and forming images of the respective subjects;
Imaging means for capturing each of the images formed by the imaging means;
A defect inspection apparatus comprising: an image processing unit that extracts a defect of one layer among a plurality of layers of the subject from two images captured by the imaging unit. The imaging means is disposed in each of an optical element that branches at least one of specularly reflected light and diffracted light of the light beam irradiated on the subject into two optical paths and an optical path branched by the optical element. A polarizing plate,
The defect inspection apparatus according to claim 1, wherein the polarizing plate on one optical path is set to transmit a polarization component orthogonal to a polarizing component that transmits the polarizing plate on the other optical path.   The defect inspection apparatus according to claim 1, wherein the image processing unit combines the two captured images to form one inspection image.   The said image processing means has the reference image which imaged the test object which is the same structure as the said test object and does not have a defect, and compares the said reference image and the said test | inspection image. Defect inspection equipment.   The defect inspection apparatus according to claim 3, wherein the image processing unit forms the inspection image by synthesizing luminance values of dots at positions corresponding to the two captured images.

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