JP4622007B2 - Defect inspection equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a defect inspection apparatus that inspects defects such as scratches, film thickness unevenness, and dust on a liquid crystal substrate or IC wafer having a predetermined circuit pattern.
[0002]
[Prior art]
For defect inspections such as film thickness unevenness and scratches on the surface of IC wafers and liquid crystal substrates, the illumination light of various light beams is irradiated from various angles, and the light from the test object is rotated or swung. In many cases, an observer observes directly by visual observation. Recently, with the quantification of defects, the labor saving of inspection, and the increase in speed, there has been a strong demand for automating defect inspection, and various apparatuses have been proposed in response to this request. For example, an image of a substrate is captured by diffracted light generated from a repetitive pattern on the substrate, image processing is performed, and defects are inspected.
[0003]
[Problems to be solved by the invention]
In a normal appearance inspection of the substrate visually observed by an observer, the substrate is irradiated with white light spotlight, and the quality of the substrate is judged by seeing how the reflected light is colored. Here, diffracted light is generated from the portion of the substrate where the repeated pattern is formed, and the observer observes the spectrum of the diffracted light. The exposure area (shot area) where defects such as defocus are present differs from the normal shot area where the surrounding defects do not exist and the coloration or intensity of the spectrum of the diffracted light is different. can do.
[0004]
When diffracted light is generated from a regular pattern, the following conditional expression (1) is satisfied.
(1) sinθd−sinθi = mλ / p
Here, θi represents an incident angle, θd represents a diffraction angle, m represents a diffraction order, λ represents a wavelength, and p represents a pitch. As is apparent from the above equation, it is understood that the order and wavelength should be reduced if diffracted light is generated from a pattern having a smaller pitch under the same angle condition.
[0005]
When visible light is used as the light source, the lower limit value of λ is almost in the vicinity of the h-line (405 nm), that is, about 400 nm, and the diffraction order of diffracted light other than zero-order light, that is, specularly reflected light is 1 in absolute value. Therefore, when the pitch falls below a predetermined value, diffracted light is not generated, and inspection cannot be performed.
[0006]
On the other hand, the automatic inspection apparatus uses the difference in the intensity of the diffracted light between the defective portion and the normal portion as in the visual inspection, and therefore has the above-mentioned problems as long as visible light is used as the light source.
[0007]
The present invention has been made in view of such problems, and an object of the present invention is to provide a defect inspection apparatus and an inspection method capable of performing good defect inspection on a substrate on which a repetitive pattern with a finer pitch is formed. .
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a defect inspection apparatus for inspecting a defect of the periodic pattern of a substrate to be tested on which a periodic pattern is formed, at least one of which is ultraviolet light shorter than 400 nm. A plurality of light sources that respectively supply light of different wavelengths, and one concave reflecting mirror that converts light emitted from each of the plurality of light sources into substantially parallel light, and through the concave reflecting mirror, An illumination optical system that irradiates the test substrate with parallel light at a predetermined angle, respectively, and only a desired order of diffracted light among a plurality of diffracted lights generated from the test substrate for each of the irradiated lights. There is provided a defect inspection apparatus comprising: one light receiving unit that receives light to form the periodic pattern image.
[0011]
Further, in a preferred aspect of the present invention, the light irradiated from each of the plurality of light sources is irradiated through the illumination optical system so that the incident angle to the test substrate differs according to the wavelength of the light. It is desirable.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a defect inspection apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
[0013]
(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of the defect inspection apparatus according to the first embodiment. The light emitted from the light source 11 as the light source unit passes through the relay lens 21 and enters the spherical reflecting mirror 31. Note that the light source unit is not limited to the configuration of the light source itself that emits light having a predetermined wavelength, but a light collecting member that collects the light from the light source and the light source (a reflecting mirror such as a condensing lens or an elliptical mirror). Etc.). The system from the relay lens 21 to the spherical reflecting mirror 31 constitutes the illumination optical system 1. The light source 11 uses, for example, a 365-nm i-line or 313-nm J-ray with a mercury lamp, 266 nm with a YAG laser 4th harmonic, 248 nm with a KrF excimer laser, and 193 nm with an ArF excimer laser. be able to. In addition, a variable aperture stop is provided at the emission end of the light source 11 to shield light unnecessary for defect inspection measurement. It is even more preferable that the light source 11 supplies light having a wavelength of 365 nm or less.
[0014]
When a mercury lamp is used, light in the ultraviolet region is extracted from white light emitted from the light source by an interference filter (not shown) and used as illumination light. More preferably, for example, a configuration in which a plurality of interference filters having different transmission wavelength ranges are provided on the revolver and the revolver is rotated by a motor so that the interference filter can be selectively inserted into and removed from the optical axis is desirable. When a laser is used as the light source 11, it is desirable to reduce the coherence of the laser light.
[0015]
The light reflected by the spherical reflecting mirror 31 enters the substrate 41 placed on the stage 51 as a substantially parallel light beam. The stage 51 can perform both rotation and tilt (tilt) about a predetermined axis. The diffracted light diffracted by the substrate 41 is reflected by the spherical reflecting mirror 32 and forms an image on the CCD image pickup surface of the image pickup device 71 by the camera lens 61. Here, the spherical reflecting mirror 32 and the camera lens 61 constitute the light receiving optical system 2, and the light receiving optical system 2 and the image sensor 71 constitute a light receiving unit. Since the diffraction angle of the diffracted light from the substrate 41 varies depending on the pattern pitch, the stage 41 is appropriately tilted by the stage 51 so that the diffracted light is incident on the light receiving optical system 2. Further, instead of tilting the stage, either one or both of the illumination optical system 1 and the light receiving optical system 2 may be rotated about the tilt axis.
[0016]
A variable aperture stop is provided in the camera lens 61 to block light unnecessary for measurement and at the same time determine the numerical aperture on the substrate side. If the numerical aperture is reduced by reducing the aperture stop, the depth of focus on the substrate side can be increased, so that peripheral images are not blurred even when tilted.
[0017]
The camera lens 61 is not limited to a single focal length lens. A plurality of lenses having different focal lengths can be exchanged, and it is desirable to change the imaging magnification by selecting a lens so that the size of the substrate image and the size of the imaging surface of the imaging device are substantially matched. Image processing efficiency can be improved by making the size of the substrate image substantially coincide with the size of the imaging surface of the imaging device. More preferably, if the camera lens 61 is a varifocal lens or a zoom lens, the magnification can be changed without replacing the lens. If it is desired to perform defect inspection in a short time, it is desirable to perform inspection without changing the magnification.
[0018]
The image processing apparatus 81 compares the image of the substrate 41 being inspected with the image of the non-defective substrate stored in advance, so that there is a part that is different from the feature of the non-defective substrate that has been subjected to pattern matching or learning in advance. Image processing such as NO is performed. For example, when a defect such as unevenness due to defocusing exists in a predetermined portion of the substrate, the defective portion is recognized and output based on information such as a difference in brightness or a difference in characteristics of the predetermined portion.
[0019]
For substrates with different pitch patterns, such as application specific ICs (hereinafter referred to as “ASIC”) or logic (logic) circuits, defect inspection is performed for each pattern region. Then, pass / fail judgment is performed for each pattern, and further logical OR is performed to determine final pass / fail.
[0020]
In general, defect inspection is performed on one pattern under one condition. However, even if a defect actually exists, the difference in brightness between the defective portion and the non-defective portion of the obtained image may not be clear due to the influence of thin film interference. For this reason, it is desirable to inspect a single pattern a plurality of times by changing the wavelength or changing the angle condition.
[0021]
The pitch of the pattern of the substrate 41 is p, the wavelength of the illumination light is λ, the diffraction order is m, the angle between the normal line of the substrate when the substrate 41 is held horizontally and the illumination light intersecting the substrate is θi, and similarly When the angle between the normal line and the diffracted light intersecting the substrate is θd and the tilt angle is θt, the following equation is established.
(2) sin (θd−θt) −sin (θi + θt) = mλ / p
Regarding the sign, as shown in FIG. 12, regarding the angle θi of the illumination light, the angle direction expected on the incident side is positive, the angle direction expected on the reflection side is negative, and regarding the angle θd and tilt angle θt of the diffracted light, The angle direction that is expected on the reflection side is negative, and the angle direction that is expected on the reflection side is positive. For the diffraction order m, the angle direction expected on the incident side with respect to the specularly reflected light of the incident light on the substrate is minus, and the angle direction expected on the reflection side is plus. The range of θi is a range from 0 degrees to 90 degrees.
[0022]
In FIG. 14, 546 nm light is used as visible light and 266 nm light is used as ultraviolet light. The illumination optical system and the light receiving optical system have an incident angle of +45 degrees and a diffraction angle of −10 degrees with respect to the horizontal position of the stage. FIG. 6 is a diagram showing the relationship between the tilt angle (horizontal axis) of the stage and the pattern pitch (vertical axis) to be inspected when arranged as described above. As is apparent from the figure, it can be seen that, when the same tilt angle, that is, the same angle condition is used, a defect inspection of a fine pitch pattern can be performed by using ultraviolet light.
[0023]
Further, the substrate 41 is arranged so as to substantially coincide with the focal plane of the spherical reflecting mirror 31. Further, in the illumination optical system 1, the light source 11 is disposed on the focal plane of the illumination optical system 1 , and in the light receiving optical system 2, the entrance pupil plane of the camera lens 61 is disposed on the focal plane of the spherical reflector 32. With this arrangement, the optical system of the apparatus of this embodiment forms a telecentric system. In the telecentric optical system, the appearance of the image captured by the image sensor 71 can be made the same over the entire surface of the substrate. In the non-telecentric optical system, the incident angle θi + θt to the substrate and the diffraction angle θd−θt in the above formula (2) differ depending on the position on the substrate. For this reason, since the intensity of the diffracted light changes depending on the incident angle of the incident light, the appearance of the same defect may differ depending on the position on the substrate. Since the defect inspection apparatus according to the present embodiment (FIG. 1) has a telecentric optical system, the incident angle θi + θt and the diffraction angle θd−θt can be made constant over the entire surface of the substrate. Therefore, since the appearance is the same for the same defect regardless of the position of the defect portion on the substrate, the detection sensitivity becomes equal, and the defect portion can be identified more quickly and accurately.
[0024]
Further, since the apparatus becomes large when a refractive telecentric optical system is used, downsizing of the apparatus is realized by adopting a reflective telecentric optical system using a spherical reflector. More preferably, since it is a decentered optical system, it is desirable to reduce the incident angle of the reflected light with respect to the spherical reflecting mirror in order to reduce astigmatism.
In this embodiment, the incident angle of the reflected light with respect to the spherical reflector is about 10 degrees.
[0025]
(Second Embodiment)
FIG. 2 is a diagram illustrating a schematic configuration of the defect inspection apparatus according to the second embodiment. In all the embodiments described below including this embodiment, the same portions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description of the overlapping portions is omitted.
[0026]
The present embodiment is a modification of the first embodiment, and is arranged so that the absolute value of the incident angle with respect to the inspection substrate 41 is slightly different from the absolute value of the diffraction angle, so that the illumination optics in the first embodiment is used. The spherical reflecting mirror constituting the system 1 and the light receiving optical system 2 is shared by one spherical reflecting mirror 31. With this configuration, it is possible to further reduce the size of the apparatus according to the first embodiment, and it is possible to inspect a pattern with a finer pitch.
[0027]
(Third embodiment)
FIG. 3 is a diagram showing a schematic configuration of the defect inspection apparatus according to the third embodiment. It is the structure which added the light source unit 12 and the illumination optical system 3 to the apparatus concerning 1st Embodiment. The illumination optical system 3 includes a relay lens 22 and a spherical reflecting mirror 33. Since the angle conditions of the illumination light from the illumination optical system 1 and the illumination light from the illumination optical system 3 are different from each other, the processing time can be shortened by simultaneously inspecting two types of pitch patterns. This is particularly effective when inspecting a Logic (logic) circuit pattern in which patterns having different pitches are mixed, an ASIC, or the like. In addition, by changing the wavelengths of the light source 11 and the light source 12, it is possible to inspect one pattern simultaneously under two conditions (fourth embodiment).
FIG. 4 is a diagram showing a schematic configuration of the defect inspection apparatus according to the fourth embodiment. The present embodiment is a modification of the third embodiment, in which the spherical reflector 31 constituting the illumination optical system 1 and the illumination optical system 3 is also used as the spherical reflector 31. In other words, this is equivalent to a configuration in which a light source is newly added in the vicinity of the light source unit 11 of the apparatus according to the second embodiment. If the two light sources have the same wavelength, two types of pitch patterns can be inspected at the same time. If the wavelengths are different from each other, one pattern can be inspected at the same time under different conditions. It is.
[0028]
(Fifth embodiment)
FIG. 5 is a diagram showing a schematic configuration of a defect inspection apparatus according to the fifth embodiment of the present invention. This is a configuration in which a line type light guide fiber 101 and a cylindrical lens 111 are used in the illumination optical system 1 or the illumination optical system 3 in the third embodiment. The light from the light source 11 is bent by the reflecting mirror M. Note that with this configuration, it is possible to reduce the loss of illumination light amount even when the incident angle increases.
[0029]
(Sixth embodiment)
FIG. 6 is a diagram showing a schematic configuration of the defect inspection apparatus according to the sixth embodiment. It is the structure which added one set of the light reception optical system 4 to the apparatus concerning 1st Embodiment. The light receiving optical system 4 includes a spherical reflecting mirror 33 and a camera lens 62, and an image obtained by the light receiving optical system 4 is picked up by the image sensor 72. The light from the light source 11 is bent by the reflecting mirror M. Similar to the third and fourth embodiments, since the angle conditions are different, two types of pitch patterns can be inspected simultaneously, and the processing time can be shortened. Furthermore, if a light source that emits multiple spectral lines (wavelength light), such as a mercury lamp, is used, it is possible to inspect a test object simultaneously under two wavelength conditions for one pattern (test object). It becomes. This also applies to points that are particularly effective for Logic circuit patterns or ASICs.
[0030]
(Seventh embodiment)
FIG. 7 is a diagram showing a schematic configuration of the defect inspection apparatus according to the seventh embodiment. The present embodiment is a modification of the sixth embodiment, in which the spherical reflecting mirror 32 constituting the light receiving optical system 2 and the light receiving optical system 4 is also used as the spherical reflecting mirror 32. In other words, this is equivalent to a configuration in which a camera lens 62 and an image sensor 72 are newly added in the vicinity of the light receiving element of the first embodiment. Inspecting two types of pitch patterns at the same time, or using a light source that emits multiple spectral lines (wavelength light) such as a mercury lamp, the test object is simultaneously subjected to two wavelength conditions for one pattern (test object). This makes it possible to reduce the size of the apparatus.
[0031]
(Eighth embodiment)
FIG. 8 is a diagram showing a schematic configuration of a defect inspection apparatus according to the eighth embodiment. This embodiment is a modification of the sixth embodiment, in which the spherical reflecting mirror 31 constituting the illumination optical system 1 and the light receiving optical system 4 is also used as the spherical reflecting mirror 31. In other words, this is equivalent to a configuration in which a camera lens 62 and an image sensor 72 are newly added in the vicinity of the light source of the apparatus of the first embodiment. Inspecting two types of pitch patterns at the same time, or using a light source that emits multiple spectral lines (wavelength light) such as a mercury lamp, the test object is simultaneously subjected to two wavelength conditions for one pattern (test object). This makes it possible to reduce the size of the apparatus.
[0032]
(Ninth embodiment)
FIG. 9 is a diagram showing a schematic configuration of the defect inspection apparatus according to the ninth embodiment. Two sets of illumination optical systems 1 and 3 and two sets of light receiving optical systems 2 and 4 are provided. Both the illumination optical system and the light receiving optical system share the concave reflecting mirrors 31 and 32. The light source 11 and the light source 12 of the illumination optical system have different use wavelengths. At wavelengths shorter than 300 nm, it is difficult to achromatically correct the camera lens achromatically, so two sets of light receiving optical systems are provided, and inspection is performed using different wavelengths.
[0033]
(10th Embodiment)
10 and 11 are diagrams showing a schematic configuration of the defect inspection apparatus according to the tenth embodiment. The basic configuration is the same as that of the first embodiment, and the same reference numerals are used for the same parts, and duplicate descriptions are omitted. When light in the ultraviolet region, particularly light with a wavelength shorter than i-line, is used as the light source light, the ultraviolet light and impurities such as NH ₄ ⁺ and SO _X in the air cause a photochemical reaction, for example, (NH ₄ ) ² SO ₄ This occurs and adheres to the surface of the optical component, thereby causing fogging of the optical component. As a result, in the case of a reflective optical component (reflecting mirror or the like), the reflectance is lowered, and in the case of a refractive optical component (lens or the like), the transmittance is lowered. In addition, since the emission spectrum overlaps with the absorption spectrum region of oxygen in a light source such as an ArF excimer laser, a decrease in transmittance due to absorption of oxygen and a decrease in reflectance of additional reflective optical components due to ozone generation or This causes a decrease in the transmittance of refractive optical components (such as a lens) and environmental contamination in the apparatus due to a reaction with the surface of the optical components. The present embodiment has been made in view of such a problem. As shown in FIG. 10, the entire optical system is surrounded by a casing 101, and a window glass 102 is provided at a portion where light enters and exits the casing. Then, by filling the inside of the housing 101 with an inert gas such as nitrogen, it is possible to prevent environmental pollution caused by generation of (NH ₄ ) 2 SO ₄ and generation of ozone. Further, since the space between the glass window 102 and the substrate 41 is air, the above-described fogging occurs in the glass window 102. For this reason, it is desirable to replace the glass window 102 periodically. In addition, since it is not necessary to replace all the optical components, the cost can be reduced as a result. Further, in order to reduce the occurrence of fogging, it is desirable that the distance between the substrate 41 and the glass window 102 be as close as possible.
[0034]
FIG. 11 is a diagram showing a configuration of a modified example of the tenth embodiment, in which an air curtain 104 made of an inert gas is used instead of the window glass 102. The inert gas supplied from the inert gas supply unit G is ejected vigorously from the valve 103 to form the air curtain 104. This inert gas air curtain 104 prevents the air around the substrate 41 from entering the cylinder. An air curtain may be further formed on the window glass. At that time, it is not necessary to replace the above window glass. Of course, not only the optical system but also the entire apparatus may be filled with an inert gas. In this case, since the contaminated outside air may enter the device from the substrate entrance / exit when replacing the substrate, an air curtain with an inert gas is formed near the substrate entrance / exit to prevent the entry of air from the outside. Is desirable.
[0035]
In the first to tenth embodiments, the automated defect inspection apparatus using the image processing apparatus is shown. However, instead of the image processing apparatus 81, a monitor for displaying a substrate image is provided, and the inspector displays an image on the monitor. It is good also as a visual inspection machine which performs pass / fail judgment while watching. A configuration example of the visual inspection machine is shown in FIG. The image processing apparatus 81 of the defect inspection apparatus according to the first embodiment is replaced with a television monitor 91. An image of the substrate by the diffracted light is displayed on the monitor, and the inspector visually observes the substrate image to determine the quality of the substrate. An optical system from the light source to the CCD image sensor is surrounded by a casing (chamber) 101. This prevents ultraviolet rays from leaking out of the device and adversely affecting the human body. At the same time, as described above, the housing is filled with an inert gas such as chemically clean air or nitrogen, so that the optical components are clouded. There is also a role to prevent.
[0036]
Moreover, in the defect inspection apparatus according to the second to ninth embodiments, as in the tenth embodiment, the optical system is surrounded by the casing 101 and an inert gas is supplied to the interior thereof, so that Needless to say, the occurrence of fogging on the surface of the optical component due to the shorter wavelength can be reduced.
[0037]
In each of the above embodiments, a fine pitch pattern and a relatively coarse pitch pattern may coexist on a substrate such as a logic (logic) circuit or an ASIC, and two types of wavelengths are used, that is, two types of wavelengths. One of the above may use ultraviolet light as inspection light for fine pitches, and the other may use visible light as inspection light for coarse pitches. At that time, it is difficult to correct chromatic aberration (achromatization) in the light receiving optical system for both visible light and ultraviolet light. Therefore, a light receiving optical system dedicated to visible light and a light receiving optical system dedicated to ultraviolet light are respectively used. It is preferable to provide it.
[0038]
In addition, by inspecting an object to be inspected using the inspection apparatus according to each of the above embodiments, a fine pattern formed on the substrate to be inspected is good or bad (pass / fail judgment). As a result, only the non-defective test substrate is transferred (shifted) to the next processing step to complete the device, etc., and the defective test substrate is reconstructed, regenerated or discarded. Etc.
[0039]
Therefore, by executing the inspection process using the inspection apparatus according to each of the above embodiments, it is possible to accurately inspect a minute pattern with high accuracy and reliably inspect an object to be inspected (photosensitive substrate such as a wafer). Therefore, a favorable semiconductor device (semiconductor device, liquid crystal display device, thin film magnetic head, etc.) can be manufactured.
[0040]
In addition, this invention can also be set as the invention of the description shown below, without restricting to what was described in said each claim. That is, for example, the present invention provides a semiconductor device manufacturing method including an inspection step of inspecting a photosensitive substrate, wherein the inspection step includes an illumination step of illuminating the substrate to be tested with light having a wavelength shorter than 400 nm, and A method of manufacturing a semiconductor device, comprising: a light receiving step for receiving light from a test substrate; and a processing step for detecting a surface state of the test substrate by performing photoelectric detection in the light receiving step. It can also be provided. In this case, it is preferable to use the illumination optical system in the illumination process, and to use the light reception optical system in the light reception process, and further includes a fog prevention process for preventing a decrease in fogging of at least one of the illumination optical system and the light reception optical system. More desirable.
[0041]
【The invention's effect】
As described above, in the present invention, it is possible to inspect a fine pitch by using ultraviolet rays as a light source. Further, fogging can be removed by enclosing the optical system in a casing and supplying an inert gas therein.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a defect inspection apparatus according to a first embodiment.
FIG. 2 is a diagram showing a schematic configuration of a defect inspection apparatus according to a second embodiment.
FIG. 3 is a diagram showing a schematic configuration of a defect inspection apparatus according to a third embodiment.
FIG. 4 is a diagram showing a schematic configuration of a defect inspection apparatus according to a fourth embodiment.
FIG. 5 is a diagram showing a schematic configuration of a defect inspection apparatus according to a fifth embodiment.
FIG. 6 is a diagram showing a schematic configuration of a defect inspection apparatus according to a sixth embodiment.
FIG. 7 is a diagram showing a schematic configuration of a defect inspection apparatus according to a seventh embodiment.
FIG. 8 is a diagram showing a schematic configuration of a defect inspection apparatus according to an eighth embodiment.
FIG. 9 is a diagram showing a schematic configuration of a defect inspection apparatus according to a ninth embodiment.
FIG. 10 is a diagram showing a schematic configuration of a defect inspection apparatus according to a tenth embodiment.
FIG. 11 is a diagram showing a modification of the tenth embodiment.
FIG. 12 is a diagram showing the sign of a sign.
FIG. 13 is a diagram showing a modification of the first embodiment.
FIG. 14 is a diagram illustrating a relationship between a tilt angle and a pitch to be inspected.
[Explanation of symbols]
1, 3 Illumination optical system 2, 4 Light receiving optical system 11 Light source 31, 32, 33 Concave reflector 41 Substrate 51 Stage 61 Camera lens 71 Image sensor 81 Image processing device 91 Monitor 101 Case 102 Window 103 Valve 104 Air curtain G Not Active gas supply unit M Reflector

Claims (2)

A defect inspection apparatus for inspecting a defect of the periodic pattern of a test substrate on which a periodic pattern is formed,
A plurality of light sources each supplying at least one light having a wavelength different from each other, wherein at least one is ultraviolet light shorter than 400 nm;
Illumination that includes one concave reflecting mirror that converts light emitted from each of the plurality of light sources into substantially parallel light, and that irradiates the substantially parallel light at a predetermined angle through the concave reflecting mirror, respectively. Optical system,
One light receiving unit that receives only the diffracted light of a desired order among the plurality of diffracted lights generated from the test substrate for each of the irradiated light, and forms the periodic pattern image,
A defect inspection apparatus comprising:   The light emitted from each of the plurality of light sources is emitted so as to have different incident angles to the test substrate via the illumination optical system according to the wavelength of the light. Defect inspection equipment.

Images