JP2022108359A - Appearance inspection device - Google Patents

Abstract

Kind Code: A1 A visual inspection apparatus capable of quickly performing a desired inspection on both a high reflectance portion and a low reflectance portion even if an inspection image includes a mixture of high reflectance portions and low reflectance portions. I will provide a. Kind Code: A1 A visual inspection apparatus 1 for inspecting an appearance of a site to be inspected based on an image obtained by capturing the external appearance of the inspection target site includes an inspection image acquisition unit 3, a reference image registration unit 4, and an inspection unit 5, and acquires the inspection image. A first level inspection image P1 obtained by imaging at least the appearance of the inspection target region Rx with a first brightness, and a second level inspection image P2 obtained by imaging the appearance of the inspection target region Rx with a second brightness, A first level reference image Pf1 corresponding to a first brightness and a second level reference image Pf2 corresponding to a second brightness are acquired in the reference image registration unit as inspection images at one time. The inspection unit compares the first level inspection image with the first level reference image for inspection, and compares the second level inspection image with the second level reference image for inspection. [Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to a visual inspection apparatus for comparing an inspection image obtained by capturing the appearance of a portion to be inspected with a reference image to inspect the portion to be inspected. For example, the present invention relates to a visual inspection apparatus that takes an image of the appearance of a semiconductor device or the like formed on a wafer and judges the quality of the semiconductor device or the like.

A semiconductor device is formed by layering a large number of semiconductor device circuits (i.e., repeated appearance patterns of device chips) on a single semiconductor wafer, and then singulated into individual chip parts. They are packaged and shipped individually as electronic components or incorporated into electrical products.

Before individual chip components are separated into individual chips, an inspection image obtained by picking up repeated appearance patterns of device chips formed on a wafer is compared with a reference image to inspect the quality of each chip component. (For example, Patent Document 1).

Also, there is known a technique for reducing erroneous detection due to misalignment by performing defect detection after aligning an image to be inspected and a reference image (for example, Patent Document 2).

JP 2007-155610 A Japanese Unexamined Patent Application Publication No. 2003-4427

FIG. 8 is an image diagram showing an example of an inspection image Px in the prior art.

A wiring circuit pattern, an insulating film, and the like are formed in layers on a semiconductor device to be inspected, and a portion Ra with a low reflectance and a portion Rb with a high reflectance are mixed. If there are scratches, foreign matter, pattern defects, etc. (hereinafter referred to as scratches or the like) in the regions Ra and Rb having different reflectances, it is difficult to inspect all the scratches and the like under one imaging condition.

For example, if an image Px is acquired under an imaging condition suitable for a region Ra with a low reflectance, a desired inspection can be performed for a flaw X1 or the like hidden in a region Ra with a low reflectance included in the image Px. The portion Rb is overexposed, and the desired inspection cannot be performed for the flaw X2 or the like hidden in the portion Rb.
On the other hand, if the image Px is acquired with a light amount, an exposure time, and the like (imaging conditions) suitable for the high-reflectance region Rb, the desired inspection cannot be performed for the flaw X2 or the like hidden in the high-reflectance region Rb included in the image Px. Although it can be performed, the flaw X1 or the like hidden in the portion Ra with low reflectance is blackened, and the desired inspection cannot be performed for the flaw X1 or the like hidden in the portion Ra.

In the prior art, in order to perform a desired examination, it is necessary to change the imaging conditions for the portions Ra and Rb having different reflectances and to perform imaging in two steps, which delays the examination time. , there is a problem that the number of sheets processed per unit time is reduced.

Therefore, the present invention has been made in view of the above problems,
To provide a visual inspection apparatus capable of quickly performing a desired inspection on both a high reflectance site and a low reflectance site even if an inspection image contains both the high reflectance site and the low reflectance site. for the purpose.

In order to solve the above problems, one aspect of the present invention includes:
An appearance inspection apparatus for inspecting an appearance of a part to be inspected based on an image obtained by capturing the appearance,
an inspection image acquiring unit that acquires an image obtained by imaging the appearance of an inspection target site as an inspection image;
a reference image registration unit for registering a reference image serving as an inspection reference for an inspection image;
an inspection unit that inspects the inspection image by comparing it with the reference image;
The inspection image acquisition unit acquires at least a first level inspection image obtained by imaging the appearance of the inspection target region with a first brightness, and a second level inspection image obtained by imaging the appearance of the inspection target region with a second brightness different from the first brightness. 2 level inspection images are acquired at once as inspection images,
In the reference image registration unit, a first level reference image corresponding to a first brightness as an inspection reference for the first level inspection image and a second level inspection image corresponding to a second brightness as an inspection reference for the second level inspection image are stored. A second level reference image is registered as a reference image,
The inspection unit compares the first level inspection image with the first level reference image for inspection, and compares the second level inspection image with the second level reference image for inspection.

According to this aspect,
A first-level inspection image and a second-level inspection image captured under imaging conditions with different brightnesses are acquired at once, and inspected by comparing them with the first-level reference image and the second-level reference image. can be done.

Even if an inspection image includes both high reflectance and low reflectance areas, desired inspection can be quickly performed on both the high reflectance areas and the low reflectance areas.

It is an image figure which shows an example of a test|inspection image in an example of the form which embodies this invention. It is a conceptual diagram which shows a mode that the appearance image in an example of the form which embodies this invention is imaged. It is an image figure which shows an example of a test|inspection image in an example of the form which embodies this invention. It is an image figure which shows an example of the reference|standard image in an example of the form which embodies this invention. It is a conceptual diagram which shows an example of a test result in an example of the form which embodies this invention. It is a flowchart which shows an example of a test|inspection flow in an example of the form which embodies this invention. It is an image figure which shows an example of the reference|standard image in another example of the form which embodies this invention. FIG. 10 is an image diagram showing an example of an inspection image in the conventional technology;

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated, using a figure. In the following description, the three axes of the orthogonal coordinate system are X, Y, and Z, the horizontal directions are expressed as the X direction and the Y direction, and the direction perpendicular to the XY plane (that is, the direction of gravity) is expressed as the Z direction. do. In the Z direction, the direction against gravity is expressed as up, and the direction in which gravity acts is expressed as down. Also, the direction of rotation with the Z direction as the central axis is defined as the θ direction.
Here, a description will be given based on an example in which semiconductor devices or the like repeatedly formed on the surface of the wafer W at a predetermined vertical and horizontal pitch are to be inspected, and inspection target portions Rx are set. The inspected portion Rx includes a portion Ra with a low reflectance and a portion Rb with a high reflectance.

FIG. 1 is a schematic diagram showing the overall configuration of an example of a mode embodying the present invention. FIG. 1 schematically shows each part constituting a visual inspection apparatus 1 according to the present invention.

The appearance inspection apparatus 1 inspects the appearance of an inspection target region Rx based on an image of the appearance.
Specifically, the visual inspection apparatus 1 includes an imaging section 2 , an inspection image acquisition section 3 , a reference image registration section 4 and an inspection section 5 . Furthermore, the visual inspection apparatus 1 includes a wafer holding section H, a relative movement section M, a computer CP, a controller CN, and the like.

The image capturing unit 2 captures an image of the appearance of the inspection target region Rx.
Specifically, the imaging unit 2 outputs a first level inspection image P1 and a second level inspection image P2. The first level inspection image P1 is obtained by imaging the appearance of the inspection target region Rx with a first brightness. On the other hand, the second level inspection image P2 is obtained by imaging the appearance of the inspection target region Rx with a second brightness different from the first brightness. The first level inspection image P1 is also called a bright condition inspection image, and the second level inspection image P2 is also called a dark condition inspection image.
More specifically, the imaging unit 2 includes an optical path branching unit 2S, a first imaging unit 2A, a second imaging unit 2B, a lens barrel 20, an objective lens 22, a revolver 23, an illumination unit 24, a half mirror 25, and the like. there is

The optical path branching unit 2S divides the imaging optical path into two systems, a first optical path LA and a second optical path LB, while sharing the optical axis with respect to the imaging region F. FIG.
Specifically, the optical path branching unit 2S directs the imaging optical path 2L guided into the lens barrel 20 through the objective lens 22 in two directions (in the figure, the first optical path LA is upward and the second optical path is rightward). LB).
More specifically, the optical path branching section 2S is composed of an optical element called a beam splitter, and directs a part (for example, 50%) of the light incident from below the optical path branching section 2S to travel upward to the first beam splitter. The light is emitted along the optical path LA, and the rest (for example, 50%) is reflected and emitted rightward as the second optical path LB.

The first image capturing section 2A captures an image of the image capturing area F via the first optical path LA. Also, the second imaging section 2B images the imaging region F via the second optical path LB. Furthermore, the first image pickup section 2A and the second image pickup section 2B are set under conditions in which the brightness of the images to be picked up is different.

Specifically, the first imaging unit 2A sets the imaging conditions (exposure time, shutter speed, gain, aperture, amount of light, etc.) related to the brightness of the image to be captured to a first level (also referred to as a bright condition). It captures an inspection image. More specifically, the first imaging section 2A includes an imaging camera 26A, an imaging lens 28A, an ND filter 29A, and the like.
The imaging camera 26A has an imaging element 27A, and outputs a captured image to the outside as a video signal or image data. Specifically, the imaging camera 26A can be exemplified by one having a CCD or CMOS type image sensor chip or the like as an imaging device 27A.
The imaging lens 28A forms an image on the imaging device 27A of the light flux incident through the first optical path LA.
The ND filter 29A attenuates the amount of light incident on the imaging element 27A via the first optical path LA. Specifically, the ND filter 29A absorbs part of the incident light and allows the rest of the light to pass through (also referred to as transmission). More specifically, the ND filter 29A has a transmittance of 99% (attenuation rate of 1%) in the wavelength band corresponding to the light sensitivity of the imaging device 27A.

Specifically, the second imaging section 2B sets the imaging condition to a second level (also referred to as a dark condition) different from the above-described first level and captures an inspection image. More specifically, the second imaging section 2B includes an imaging camera 26B, an imaging lens 28B, an ND filter 29B, and the like.
The imaging camera 26B has an imaging device 27B, and outputs a captured image to the outside as a video signal or image data. Specifically, the imaging camera 26B can be exemplified by one having a CCD or CMOS type image sensor chip or the like as the imaging device 27B.
The imaging lens 28B forms an image on the imaging device 27B of the light flux incident through the second optical path LB.
The ND filter 29B attenuates the amount of light incident on the imaging element 27B via the second optical path LB. Specifically, the ND filter 29B absorbs part of the incident light and allows the rest of the light to pass through (also referred to as transmission). More specifically, the ND filter 29B has a transmittance of 1% (attenuation rate of 99%) in the wavelength band corresponding to the light sensitivity of the imaging device 27B.

The imaging by the first imaging section 2A and the imaging by the second imaging section 2B are performed at the same time or in a short period of time. Specifically, when a light emission signal is output from the control unit CP to the illumination unit 24 to irradiate the illumination light L1, both the first imaging unit 2A and the second imaging unit 2B perform imaging. , the imaging trigger output to the first imaging section 2A and the imaging trigger output to the second imaging section 2B at the same time. The term "simultaneously" as used herein means not only a completely zero time lag, but also a delay time such as cycle processing of the control device, etc. Including when it is output. Also, before outputting the light emission signal to the illumination unit 24, both the first imaging unit 2A and the second imaging unit 2B are set in a state capable of imaging, and before the respective exposure times elapse, A case of outputting a light emission signal (that is, emitting the common illumination light L1) is also included in the “simultaneous imaging”. Also, "for a short period of time" means a permissible time lag to the extent that the inspection time is not greatly delayed.

More specifically, the first level inspection image P1 and the second level inspection image P2 captured by the imaging cameras 26A and 26B are externally (in this embodiment, the inspection image acquisition unit 3) as video signals and video data. output to

The lens barrel 20 fixes the optical path branching section 2S, the first imaging section 2A, and the second imaging section 2B in a predetermined positional relationship.
Specifically, the lens barrel 20 has a substantially T-shaped interior so as to shield external light and guide the observation light L2 incident from the objective lens 22 to the first imaging section 2A and the second imaging section 2B. It has a hollow (also called hollow) cylindrical shape. A revolver 23 is attached to one end side (lower side in the drawing) of the lens barrel 20, and a first imaging section 2A and a second imaging section 2B are attached to the other end side (upper side and right side in the drawing). , an optical path branching portion 2S is attached inside the lens barrel 20. As shown in FIG. Further, the lens barrel 20 shown in this example has a double-branching structure, and an illumination section 24 and a half mirror 25 are attached between the revolver 23 and the optical path branching section 2S.
Further, the lens barrel 20 is attached to the apparatus frame 1f via a connecting metal fitting (not shown).

The objective lens 22 forms an image of the imaging area F on the wafer W on the imaging elements 27A and 27B of the imaging cameras 26A and 26B at different predetermined observation magnifications. Specifically, the objective lens 22 includes objective lenses 22a and 22b having different magnifications. The objective lens 22 is arranged at a predetermined working distance from the surface of the wafer W (that is, the surface on which the appearance of the portion to be inspected is formed).

The revolver 23 switches the magnification of the objective lens 22 to be used. Specifically, a plurality of objective lenses 22a and 22b with different magnifications are attached to the revolver 23, and the lens magnification can be changed by rotating and stopping by a predetermined angle manually or based on signal control from the outside. Can switch.

The illumination unit 24 emits illumination light L1 necessary for imaging.
Specifically, the illumination unit 24 can be exemplified by a laser diode, a metal halide lamp, a xenon lamp, an LED illumination, and the like, and switches between light emission and extinguishment based on signal control from the outside, and emits strobe light at a predetermined place and timing. let

The half mirror 25 reflects the illumination light L1 emitted from the illumination unit 24 to irradiate the wafer W side, and passes the observation light L2 incident from the wafer W side to the imaging unit 3 side.

Since the imaging unit 2 has such a configuration, the first level inspection image P1 captured under the bright condition and the second level inspection image P2 captured under the dark condition are inspected for one inspection target region Rx. Images can be captured simultaneously or within a short period of time.

The inspection image acquisition unit 3 acquires an appearance image of the inspection target region Rx as an inspection image. Specifically, the inspection image acquiring unit 3 captures a first level inspection image P1 obtained by imaging the appearance of the inspection target region Rx with a first brightness, A second level inspection image captured at a brightness of 2 is acquired at once as an inspection image. More specifically, the inspection image acquiring section 3 is configured by the input section of the computer CP. Here, "obtaining at once" means obtaining "simultaneously" or "within a short period of time" as described above.

FIG. 2 is a conceptual diagram showing how an appearance image is captured in an example of the embodiment of the present invention. FIG. 2 shows device chips C formed on a wafer W at a predetermined pitch in the XY directions while moving relative to the wafer W in the directions indicated by arrows Vs using the imaging cameras 26A and 26B of the imaging unit 2. A state in which the appearance of the device is successively captured is shown. The captured inspection images P1 and P2 are sequentially output from the imaging cameras 26A and 26B.

Specifically, during the relative movement of the relative movement section M (for example, movement in the direction of the arrow Vs), the illumination section 24 is caused to emit strobe light at a predetermined interval or position, and an exterior image similar to a still image is captured. Images are captured by the cameras 26A and 26B. Appearance images P1 and P2 output from the imaging cameras 26A and 26B are acquired from the input section of the inspection image acquiring section 3. FIG.

Since the inspection image acquisition unit 3 is configured as described above, the first level inspection image P1 captured under the bright condition and the second level inspection image P2 captured under the dark condition are obtained for one inspection target region Rx. , can be acquired at once as an inspection image.

FIG. 3 is a schematic diagram showing a main part of an example of a form embodying the present invention.
FIG. 3A schematically shows a first level image P1 captured by the imaging unit 2 and acquired by the inspection image acquisition unit 3. As shown in FIG.
FIG. 3B schematically shows a second level image P2 captured by the imaging unit 2 and acquired by the inspection image acquiring unit 3. As shown in FIG.

The reference image registration unit 4 registers a reference image that serves as an inspection reference for inspection images.
Specifically, the inspection reference image registration unit 4 stores a first level reference image Pf1 corresponding to a first brightness that serves as an inspection reference for the first level inspection image P1 and an inspection reference for the second level inspection image P2. A second level reference image Pf2 corresponding to the second brightness is registered. The first level reference image Pf1 is also referred to as a bright condition reference image, and the second level reference image Pf2 is also referred to as a dark condition reference image.

More specifically, the inspection reference image registration unit 3 is composed of a storage unit and an auxiliary storage unit of the computer CP.

FIG. 4 is an image diagram showing an example of a reference image in an example of the mode embodying the present invention.
FIG. 4(a) shows an example of the first level reference image Pf1, and FIG. 4(b) shows an example of the second level reference image Pf2.

The first level reference image Pf1 serves as a reference for the inspection of the inspection target site Rx, and can be exemplified by imaging a site without scratches or the like under the same imaging conditions as the first level inspection image P1.

The second level reference image Pf2 serves as a reference for the inspection of the inspection target site Rx, and can be exemplified by imaging a site free of scratches or the like under the same imaging conditions as the second level inspection image P2.

The inspection unit 5 performs inspection by comparing the inspection image with a reference image.
Specifically, the inspection unit 5 compares the first level inspection image P1 with the first level reference image Pf1 for inspection, and compares the second level inspection image P2 with the second level reference image Pf2 for inspection. is.
More specifically, the inspection unit 5 is composed of a processing unit and an image processing unit of the computer CP and an execution program, and is configured to perform the following processing.
For example, the inspection unit 5 compares, for each pixel in the first level inspection image P1, the luminance value of the pixel in the first level reference image Pf1 corresponding to the position of the inspection target region Rx (for example, R1, R2). Then, it is determined whether or not the luminance difference is within a predetermined range (that is, within the acceptance criteria), and whether or not pixels with a large luminance difference are continuous or aggregated.
Furthermore, the inspection unit 5 compares the luminance values of the pixels in the first level reference image Pf2 corresponding to the positions of the parts to be inspected Rx (for example, R1 and R2) in the second level inspection image P2. Then, it is determined whether or not the luminance difference is within a predetermined range (that is, within the acceptance criteria), and whether or not pixels with a large luminance difference are continuous or aggregated.

FIG. 5 is an image diagram showing an example of an inspection result in an example of the mode embodying the present invention.
As an example of the inspection result, FIG. 5A shows an example of the luminance difference (difference) ΔP1 comparing the first level inspection image P1 with the first level reference image Pf1, and FIG. shows an example of a luminance difference (difference) ΔP2 in which the second level inspection image P2 is compared with the second level reference image Pf2. The difference ΔP1 contains information indicating that the flaw X1 exists in the region Ra with low reflectance, and the difference ΔP2 contains information indicating that the flaw X2 exists in the region Rb with high reflectance. It is included.

The wafer holder H holds the wafer W. As shown in FIG.
Specifically, the wafer holder H supports the wafer W from the bottom side while maintaining a horizontal state. More specifically, the wafer holder H has a mounting table H1 with a horizontal upper surface. The mounting table H1 is provided with grooves and holes in a portion that contacts the wafer W, and these grooves and holes are connected to negative pressure generating means such as a vacuum pump via switching valves and the like. The wafer holding part H can hold and release the wafer W by switching the grooves and holes to a negative pressure state or an atmospheric release state.

The relative movement part M relatively moves the wafer holding part H and the imaging part 3 .
Specifically, the relative movement section M is configured including an X-axis slider M1, a Y-axis slider M2, and a rotation mechanism M3.

The X-axis slider M1 is mounted on the device frame 1f, and moves the Y-axis slider M2 in the X direction at an arbitrary speed and stops at an arbitrary position. Specifically, the X-axis slider is composed of a pair of rails extending in the X direction, a slider portion that moves on the rails, and a slider driving portion that moves and stops the slider portion.

The Y-axis slider M2 moves the rotation mechanism M3 in the Y direction at an arbitrary speed and stops it at an arbitrary position based on a control signal output from the controller CN. Specifically, the Y-axis slider is composed of a pair of rails extending in the Y direction, a slider portion that moves on the rails, and a slider driving portion that moves and stops the slider portion.

The slider driving units of the X-axis slider M1 and the Y-axis slider M2 can be composed of a combination of a servomotor or a pulse motor and a ball screw mechanism that rotates and stops under signal control from the control unit CN, or a linear motor mechanism. can.

The rotating mechanism M3 rotates the mounting table H1 in the .theta. direction at an arbitrary speed and stops it at an arbitrary angle. Specifically, the rotation mechanism M3 can be exemplified by a direct drive motor or the like that rotates/stops at an arbitrary angle under signal control from an external device. A mounting table H1 of the wafer holder 2 is mounted on the member on the rotating side of the rotating mechanism M3.

Since the relative movement unit M has such a configuration, while holding the wafer W to be inspected, the wafer W can be moved independently in the XYθ direction with respect to the imaging unit 2 or in combination in a predetermined manner. It can be moved relative to each other by speed and angle, and can be stopped at any position and angle.

The computer CP inputs signals and data from the outside, performs predetermined arithmetic processing and image processing, and outputs signals and data to the outside. For example, it performs the following functions.
・Registration of pixel pitch and imaging magnification of imaging camera ・Registration of inspection recipe (imaging position, imaging order, imaging interval (pitch, interval), moving speed, etc.), switching of inspection recipe to be used, etc. ・Acquired inspection image P1, Image processing for P2, etc. ), an auxiliary storage device (HDD, SSD, etc.), etc. (that is, hardware), and its execution program, etc. (that is, software).

The controller CN inputs and outputs signals and data to and from external devices (devices such as the wafer holding unit 2, the imaging unit 3, the relative movement unit M, and the computer CP) and performs predetermined control processing. It performs the functions of
・A signal for holding/releasing the wafer W is output to the wafer holding unit 2. ・The revolver 23 is controlled to switch the objective lens 22 (imaging magnification) to be used. Outputs an imaging trigger to the imaging cameras 26A and 26B Inputs the inspection images P1 and P2 output from the imaging cameras 26A and 26B Drive control of the relative movement unit M: X-axis slider M1, Y-axis slider A function of outputting a drive signal while monitoring the current position of M2 and the rotation mechanism M3, and controlling this. The imaging trigger can be output to the imaging unit 2 while changing the location. Furthermore, it is possible to output the imaging trigger while switching the imaging magnification and the field size according to the inspection type and changing the imaging interval, thereby obtaining a desired image.

In addition, the following methods can be exemplified for the output of the imaging trigger.
A method in which the illumination light L1 is emitted for an extremely short period of time (so-called stroboscopic light emission) every time a predetermined distance is moved while scanning in the X direction.
A method of moving and stopping at a predetermined position and irradiating illumination light L1 to capture an image (so-called step & repeat method).

More specifically, the controller CN is composed of a part of the computer CP, a dedicated programmable logic controller, etc. (that is, hardware), and its execution program, etc. (that is, software).

<Operation flow>
FIG. 6 is a flow diagram of one example of embodying the present invention.
FIG. 6A shows a series of flow for capturing and registering an image (that is, a reference image) that serves as an inspection reference for device chips C arranged on a wafer W using the visual inspection apparatus 1. Each operation step is shown in FIG. shown in This is referred to as a reference image registration flow, and the operation flow described below is the reference image registration mode.

First, in order to register a reference image, the wafer W is mounted on the mounting table H1 of the visual inspection apparatus 1 (step s1). This wafer W includes device chips C (so-called non-defective chips) that serve as a reference for judging quality.

Subsequently, the wafer W is aligned by reading the alignment marks formed on the wafer W (step s2).

Subsequently, the relative movement unit M is controlled to move the wafer W to a position (that is, an imaging position) where the imaging unit 2 can image the device chip C set as the reference image (step s3).

Subsequently, the first imaging unit 2A captures the first level reference image Pf1, the second imaging unit 2B captures the second level reference image Pf2, and registers these as reference images in the inspection reference image registration unit 3 ( step s4).

Further, it is determined whether or not the reference image should be captured/registered (step s5), and if the reference image should be captured/registered, the above-described steps s3 to s5 are repeated. On the other hand, if there is no need to pick up and register another reference image, the wafer W is delivered (step s6).

Then, it is determined whether or not another reference image is to be imaged and registered using another wafer W (step s7), and the above steps s1 to s7 are repeated when imaging and registration are to be continued. On the other hand, if there is no need to continue capturing and registering the reference image, the series of flow ends.

FIG. 6(b) shows a series of flow steps in which an appearance image of the device chips C arranged on the wafer W is captured using the appearance inspection apparatus 1 and inspected based on the image. ing. This is called an inspection flow, and the inspection mode is a mode in which operation is performed according to the operation flow described below.

First, an inspection recipe is set by new registration or selected from inspection recipes registered in advance, and the wafer W is mounted on the mounting table H1 (step s11).

Subsequently, the wafer W is aligned by reading the alignment marks formed on the wafer W (step s12).

Subsequently, the relative movement unit M is controlled to move the wafer W while the image pickup unit 2 picks up an image of the device chip C, the first image pickup unit 2A picks up the first level inspection image P1, and the second image pickup unit 2B. The second level inspection image P2 is picked up at step s13, and these images P1 and P2 are acquired as inspection images at once by the inspection image acquiring unit 3 (step s13).

Subsequently, the acquired first level inspection image P1 and the pre-registered first level reference image Pf1 are compared for inspection, and the acquired second level inspection image P2 and the pre-registered second level reference image are inspected. Pf2 is compared to check (step s14).

Subsequently, another inspection image is obtained to determine whether or not to continue the inspection (step s15). If the inspection is to be continued, the above steps s13 to s15 are repeated.
On the other hand, if there is no need to continue the inspection, etc., the wafer W is delivered (step s16).

Then, it is determined whether or not inspection images are to be obtained and inspected for other wafers (step s17), and the above-described steps s11 to s17 are repeated when further inspections are to be performed. On the other hand, if there is no need for further inspection or the like, the series of flows is terminated.

Since the appearance inspection apparatus 1 according to the present invention has such a configuration, the first level inspection image and the second level inspection image captured under mutually different imaging conditions are acquired at once, and each is acquired as a second level inspection image. Inspection can be performed by comparing with a 1st level reference image or a 2nd level reference image. Therefore, even if an inspection image includes both high and low reflectance sites, a desired inspection can be quickly performed on both the high reflectance sites and the low reflectance sites.

(another form)
In the above description, the appearance inspection apparatus 1 includes the imaging unit 2, and the inspection image acquisition unit 3 acquires the first level inspection image P1 and the second level inspection image P2 having different brightnesses captured by the imaging unit 2. did.
With such a configuration, it is only necessary to complete the operation of sequentially imaging the inspection target region Rx while relatively moving the wafer W and the imaging unit 3, and the inspection images P1 and P2 are acquired at each imaging location at once. be able to. That is, there is no need to change the imaging conditions and perform the second round of imaging (perform imaging in two steps) for the same examination target region Rx as in the conventional technique.
Therefore, the inspection time can be shortened, and the number of wafers processed per unit time can be improved.

However, in embodying the present invention, the imaging unit 2 is not essential. The configuration may be such that comparison/inspection is performed with the images Pf1 and Pf2.

(Regarding the reference image and inspection unit)
In the above description, the inspection unit 5 compares the first level inspection image P1 captured with the first brightness (bright condition) and the first level reference image Pf1 corresponding to the first brightness (bright condition). , compares a second level inspection image P2 captured with a second brightness (dark condition) and a second level reference image Pf2 corresponding to the second brightness (dark condition) to perform an inspection. did. In this case, the luminance differences (differences) ΔP1 and ΔP2 of the compared pixels may be separately output as inspection results, or may be added together and output as an inspection result.

However, the appearance inspection apparatus 1 is not limited to such a configuration, and the present invention can be embodied even with other configurations.
For example, among the parts to be inspected Rx, a part to be inspected based on an image acquired with a first brightness (bright condition) and a part to be inspected based on an image acquired with a second brightness (dark condition). is defined in advance.
In particular,
Position information of a portion to be inspected with the first brightness among the inspection target portions Rx is defined in association with the first level reference image,
The position information of the part to be inspected with the second brightness among the parts to be inspected Rx is defined in association with the second level reference image.
Between the first level inspection image P1 and the first level reference image Pf1, parts to be inspected with the first brightness (in this example, parts Ra with low reflectance) are compared and inspected,
Of the second level inspection image P2 and the second level reference image Pf2, the parts to be inspected with the second brightness (in this example, the parts Rb with high reflectance) are compared and inspected.

The positional information of the part to be inspected with the first brightness indicates which part is to be compared between the inspection image and the reference image, and the coordinates (image relative coordinates from the corner of the image, relative coordinates from a mark or the like that serves as a positioning reference in the image, etc.). On the other hand, the positional information of the part to be inspected with the second brightness indicates which part is to be compared between the inspection image and the reference image, and the coordinates (image relative coordinates from the corner of the image, relative coordinates from a mark or the like that serves as a positioning reference in the image, etc.).

With such a configuration, it is possible to omit a portion of the first-level inspection image that has blown-out highlights and a portion of the second-level inspection image that has blown-out shadows from objects to be compared with the reference image. Therefore, the area of the part to be inspected for comparison processing can be reduced, and the inspection time can be shortened, which is preferable.

In the above description, the configuration in which the first level reference image Pf1 and the second level reference image Pf2 are separately registered in the reference image registration unit 4 is illustrated.
With such a configuration, the inspection unit 5 compares the first level inspection image P1 with the first level reference image Pf1 for inspection, and compares the second level inspection image P2 with the second level reference image Pf2. A desired inspection can be performed by performing inspection by
With such a configuration, the main processing in the inspection unit 5 is only the comparison processing for calculating the luminance difference, so the processing time can be shortened, which is preferable.

However, the appearance inspection apparatus 1 may have a configuration as described below.
For example, a portion Ra serving as an inspection reference under a first brightness (bright condition) and a portion Rb serving as an inspection reference under a second brightness (dark condition) are combined into one image as a reference image Pfz. A region Ra to be inspected under the first brightness (bright condition) and a region Rb to be inspected under the second brightness (dark condition) are registered as inspection images Pz. In this configuration, the images are synthesized into one image and compared/inspected with the reference image Pfz.

Specifically, the appearance inspection apparatus 1 has a configuration including an inspection image synthesizing unit 6 in addition to the configuration described above (see FIG. 1).

FIG. 7 is an image diagram showing an example of an inspection image and a reference image in another example of the mode embodying the present invention. FIG. 7A shows an example in which a region Ra to be inspected under bright conditions and a region Rb to be inspected under dark conditions are combined into one image as inspection image Pz and registered. It is shown. FIG. 7B shows an example in which a portion Ra serving as an inspection reference under bright conditions and a portion Rb serving as an inspection reference under dark conditions are combined into one image as a reference image Pfz and registered. It is shown.

The inspection image synthesizing unit 6 acquires the inspection image with the inspection image acquiring unit 3 based on the preset position information of the part to be inspected with the first brightness and the position information of the part to be inspected with the second brightness. Then, the part to be inspected (for example, the part Ra with low reflectance) in the first level inspection image P1 and the part to be inspected (for example, the part Rb with high reflectance) in the second level inspection image P2 are combined into an inspection image Pz are combined into one image. Specifically, the inspection image synthesizing section 6 is composed of a processing section and an image processing section of the computer CP and an execution program.

Furthermore, in the reference image registration unit 4,
Based on the position information of the part to be inspected with the first brightness and the position information of the part to be inspected with the first brightness, the part to be inspected with the first brightness in the first level reference image Pf1 (in this example, A portion Ra with a low reflectance) and a portion to be inspected with the second brightness in the second level reference image Pf2 (a portion Rb with a high reflectance in this example) are combined into one image as a reference image Pfz. The configuration shall be registered with
With such a configuration, the reference images Pfz can be collectively managed. By doing so, it is possible not only to reduce the number of images to be registered in advance (that is, storage capacity), but also to have excellent listability, which is preferable. In addition, although the process of synthesizing the acquired first level inspection image P1 and second level inspection image P2 into one inspection image Pz is increased, the comparison process between the inspection image Pz and the reference image Pfz is sufficient. , the overall inspection time is not significantly delayed. Therefore, the desired inspection can be performed quickly.

<Regarding the light intensity difference of the image>
In the above description, the optical path branching section 2S causes a portion (eg, 50%) of the light incident from below the optical path branching section 2S to travel straight and be emitted upward as the first optical path LA, and the rest (eg, 50%) is reflected. A configuration provided with a beam splitter is shown as an example for allowing the light to be rotated and emitted to the right as the second optical path LB. The ND filter 29A has a transmittance of 99% (attenuation rate of 1%) and the ND filter 29B has a transmittance of 1% (attenuation rate of 99%).

However, the transmittance (attenuation rate) of these ND filters 29A, 29A is merely an example, and may be appropriately determined according to the brightness (reflectance, transmittance, etc.) of the object to be inspected.

Further, in the above description, the configuration in which the ND filters 29A and 29B are provided in both the first imaging unit 2A and the second imaging unit 2B is illustrated, but one of them (for example, the ND filter 29A) is omitted, and the other (For example, a configuration including only the ND filter 29B) may be used.

Alternatively, the ND filters 29A and 29B may be omitted by adopting a configuration in which the reflectance and transmittance of the beam splitter are distributed to produce a difference in the amount of light.
Alternatively, the exposure time (shutter time) of the imaging cameras 26A and 26B and the aperture ratio of the diaphragm may be set to different conditions.

<Regarding the number of optical path branches>
In the above description, the optical path branching unit 2S branches the imaging optical path into two systems, the first optical path LA and the second optical path LB, while sharing the optical axis with respect to the imaging region F, and passes through the branched optical paths to the first optical path. The configuration for imaging with the imaging unit 2A and the second imaging unit 2B is illustrated.

However, in embodying the present invention, the number of branches is not limited to two, and may be three or more. In this case, according to the number of branched optical paths, a third imaging section having the same configuration as the first imaging section 2A and the second imaging section 2B, a fourth imaging section, and the like are provided. In this case, the amount of light captured by the first imaging section 2A, the second imaging section 2B, the third imaging section, etc. is 99% (first brightness), 0.9% (second brightness), 0 The light branching unit 2S and the ND filter are set so that the brightness becomes .09% (third brightness), . Then, the inspection image acquiring unit 3 acquires a second level inspection image captured by the first imaging unit 2A at the first brightness, a second level inspection image captured by the second imaging unit 2B at the second brightness, A third level inspection image or the like captured with a third brightness by a third imaging unit or the like is configured to be acquired at once as an inspection image. Further, the reference image registration unit 4 is provided with first to third level reference images corresponding to the first to third brightnesses, etc., which serve as inspection references for the first to third level inspection images. The unit 5 is configured to compare the first to third level inspection images and the like with the first to third level reference images and the like for inspection.

REFERENCE SIGNS LIST 1 appearance inspection device 2 imaging unit 3 inspection image acquisition unit 4 reference image registration unit 5 inspection unit 6 inspection image synthesizing unit H wafer holding unit C imaging unit M relative movement unit CP computer CN controller 1f device frame 2A first imaging unit 2B th 2 imaging unit 2S optical path branching unit 2L imaging optical path 20 lens barrel 22 objective lens (22a, 22b)
23 Nosepiece 24 Illumination unit 25 Half mirror 26A, 26B Imaging camera 27A, 27B Imaging device 28A, 28B Imaging lens 29A, 29B ND filter H1 Mounting table M1 X-axis slider M2 Y-axis slider M3 Rotation mechanism W Wafer C Device chip (chip parts)
F imaging area (field of view)
Rx Site to be inspected Ra Site with low reflectance Rb Site with high reflectance P1 First level inspection image P2 Second level inspection image Pz Combined inspection image Pf1 First level reference image Pf2 Second level reference image Pfz Combined Reference image L1 Illumination light L2 Light incident from the wafer side (reflected light, scattered light)

Claims (4)

An appearance inspection apparatus for inspecting an appearance of a part to be inspected based on an image obtained by capturing the appearance,
an inspection image acquisition unit that acquires an image obtained by imaging the appearance of the inspection target site as an inspection image;
a reference image registration unit for registering a reference image serving as an inspection reference for the inspection image;
an inspection unit that inspects the inspection image by comparing it with the reference image;
The inspection image acquisition unit obtains at least a first level inspection image obtained by imaging the appearance of the inspection target site with a first brightness, and an inspection image of the appearance of the inspection target site at a second brightness different from the first brightness. Acquire the second level inspection image captured in and at once as the inspection image,
The reference image registration unit stores the first level reference image corresponding to the first brightness as an inspection reference for the first level inspection image and the second level reference image as an inspection reference for the second level inspection image. A second level reference image corresponding to brightness is registered as the reference image,
The inspection unit compares the first level inspection image with the first level reference image for inspection, and compares the second level inspection image with the second level reference image for inspection. Appearance inspection device. An imaging unit for imaging the appearance of the inspection target site,
The imaging unit is
an optical path branching unit that branches the imaging optical path into at least two systems including a first optical path and a second optical path while sharing an optical axis with respect to the imaging area;
a first imaging unit that images the imaging region with the first brightness via the first optical path;
A second imaging unit that images the imaging region with the second brightness via the second optical path,
The inspection image acquisition unit includes:
obtaining an image captured by the first imaging unit as the first standard inspection image;
2. The visual inspection apparatus according to claim 1, wherein an image captured by said second imaging unit is acquired as said second level inspection image. position information of a portion to be inspected with the first brightness among the inspection target portions is defined in association with the first level reference image;
Position information of a portion to be inspected with the second brightness among the inspection target portions is defined in association with the second level reference image,
The inspection unit
comparing and inspecting portions to be inspected with the first brightness in the first level inspection image and the first level reference image;
3. The appearance according to claim 1, wherein parts to be inspected with the second brightness are compared and inspected in the second level inspection image and the second level reference image. inspection equipment. Based on the positional information of the part to be inspected with the first brightness and the positional information of the part to be inspected with the second brightness, the part to be inspected with the first brightness in the first level inspection image and the an inspection image synthesizing unit that synthesizes the part to be inspected with the second brightness in the second level inspection image into one image as the inspection image,
The reference image registration unit includes:
Based on the position information of the part to be inspected with the first brightness and the position information of the part to be inspected with the second brightness, the part to be inspected with the first brightness in the first level reference image and the 4. The visual inspection apparatus according to claim 3, wherein the part to be inspected with the second brightness in the second-level reference image is combined into one image as the reference image and registered.

Images