JPH07107346A - Inspection device - Google Patents

Abstract

PURPOSE:To provide an inspection device which is capable of observing the state of the surface of a sample in real time and exactly. CONSTITUTION:The irradiating light from a light source 2 irradiates on the surface 4a of a sample after it is made a parallel luminous flux by an optical element 3. As for the reflected light from the surface 4a of the sample, a beam diameter is converged by the optical element 3 and the reflected light is branched from irradiating light at a half mirror 5. On the image space focal plane after the optical element 3 or in the vicinity of the plane, an aperture diaphragm 6 is arranged and the image of reflected light formed just after this aperture diaphragm 6 is detected by the detection surface provided on a detector 7. In this case, because a moving device 8 moving the detector 7 in a direction perpendicular to the optical axis of the optical element 3 is provided, a situation that stray light caused in the optical element 3 due to the entering of irradiating light is led to the detection surface of the detector 7 and becomes the hindrance of an observation is prevent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to the surface condition of a sample
The present invention relates to an inspection device for dimensional observation, and particularly to an inspection device suitable for detecting an index formed on a sample surface.

[0002]

2. Description of the Related Art As an inspection device for an index formed on a sample such as a mirror wafer used for manufacturing a semiconductor integrated circuit,
Conventionally, it is known to directly observe a sample illuminated by a fluorescent lamp or a halogen lamp with a CCD camera. Also known is an inspection device using a Schlieren optical system as an inspection device for detecting the surface condition (undulation, dimples, protrusions, poor cleaning, buff damage, etc.) of a sample.

The Schlieren optical system used in the latter inspection apparatus is one of the typical optical systems that expresses a change in refractive index and a change in reflectance due to unevenness of the sample surface as a difference in brightness.
This optical system collimates the light emitted from a point light source by an optical element (lens), irradiates the sample surface from its normal direction, focuses the reflected light by an optical element (lens), and then focuses on the image space. A part of scattered light is blocked by a knife edge installed on a flat surface,
The reflected image is observed with the naked eye or a camera after that.

According to this optical system, if the sample surface has irregularities, light is scattered at that portion, but the portion of the scattered light that hits the knife edge is blocked. As a result, behind the knife edge, the portion corresponding to the scattered light blocked by the knife edge becomes dark, and the other portion becomes bright. Since this light-dark pattern corresponds to the surface state of the sample, the surface state of the sample can be observed from the light-dark pattern.

By the way, in the Schlieren optical system, if the knife edge is not used and the scattered light component is not blocked at all, the entire light becomes bright when the light amount is large, and therefore the light amount is reduced to form a bright-dark pattern. Although it is designed to be exposed, the light-dark pattern has a problem that the light-dark pattern is extremely difficult to see because only a slight contrast can be obtained.

On the other hand, in the Schlieren optical system,
By setting the knife edge and shifting the focus slightly (when it is in focus, it is the same as when the knife edge is not provided in the Schlieren optical system).
There is also known an inspection device that observes the surface condition of a sample in a place with a relatively high contrast.

[0007]

However, these conventional inspection apparatuses have the following problems.

That is, it was extremely difficult to obtain a clear image with the inspection device which directly observes with the CCD camera.

In the former of the inspection devices using the Schlieren optical system, a bright / dark pattern corresponding to the surface condition of the sample can be formed behind the knife edge, but the bright / dark pattern was not blocked by the knife edge. The contrast is low because it contains a large amount of scattered light components.
Further, since the range that can be observed behind the knife edge is a part of the sample surface and not the entire sample surface, in order to observe the state of the entire sample surface, the sample should be centered around the optical axis by 1
Must rotate. On the other hand, the latter of the inspection devices using the Schlieren optical system only moves the observation point in the optical axis direction and hardly blocks the scattered light, so that the contrast is extremely low and unevenness occurs. Although the area can be roughly determined, there was a problem that it was not possible to determine how deep or high it was.

The present invention has been made in view of the above points, and an object thereof is to provide an inspection apparatus capable of accurately observing the state of a sample surface in real time.

[0011]

In order to achieve the above object, the invention according to claim 1 is to provide an optical element for guiding the irradiation light from the light source to the sample surface and converging the reflected light returning from the sample surface. , A branching means for branching the reflected light from the sample surface from the optical path of the irradiation light after the reflected light passes through the optical element, and a position corresponding to the focal plane of the rear image space of the optical element or in the vicinity thereof. An inspection apparatus having an aperture stop, comprising detection means for detecting an image of reflected light that has passed through the aperture stop, and moving means for moving the detection means in a direction perpendicular to the optical path of the reflected light. Is.

According to a second aspect of the present invention, an optical element for guiding the irradiation light from the light source to the sample surface and converging the reflected light returning from the sample surface, and the reflected light from the sample surface are A branching unit that branches the reflected light from the optical path of the irradiation light after passing through the optical element, and an aperture stop disposed at a position corresponding to the rear image space focal plane of the optical element or in the vicinity thereof. An inspection apparatus comprising: a detection unit that detects an image of the reflected light that has passed through and a moving unit that moves the light source in a direction perpendicular to the optical path of the irradiation light.

According to a third aspect of the present invention, the illumination optical system for guiding the irradiation light from the light source to the sample surface and the reflected light returned from the sample surface before the reflected light re-enters the illumination optical system. A diverging means for diverging from the optical path of the irradiation light, an observation optical system including an optical element for converging the reflected light diverged by the diverging means, and an optical element disposed at or near a position corresponding to the rear image space focal plane of the optical element An inspection apparatus comprising: an aperture stop provided.

[0014]

According to the first aspect of the invention, of the reflected light from the sample surface, the return light reflected in a predetermined direction opposite to the incident direction is at a position corresponding to the rear image space focal plane of the optical element. Most of the scattered light that passes through the aperture stop arranged in the vicinity thereof and is reflected in other directions is blocked by this aperture stop. Therefore, on the detection surface provided in the detection means, a two-dimensional bright-dark pattern reflecting the state of the sample surface such as unevenness and reflectance is formed by the return light of the reflected light. By detecting this bright and dark pattern, the two-dimensional state of the sample surface can be observed at one time. In this case, the sample can be focused and detected, and most of the scattered light can be removed by the aperture stop, so it is observed. The sharpness of the bright and dark pattern is significantly improved. Moreover, since the moving means for moving the detecting means in the direction perpendicular to the optical path of the reflected light is provided, it is possible to avoid the problem that unnecessary light (stray light) generated by the optical element hinders the observation of the light-dark pattern. That is, by appropriately adjusting the moving means and moving the detecting means in a direction perpendicular to the optical path of the reflected light, stray light generated in any part of the optical element due to incidence of the irradiation light passes through the aperture stop and is detected. It is possible to effectively prevent the light from being guided to the detection surface provided in the means, and it is possible to prevent a situation in which stray light is projected on a local region of the detection surface and hinders observation.

According to the second aspect of the invention, the presence of the aperture stop disposed at or near the position corresponding to the back image space focal plane of the optical element allows the two-dimensional state of the sample surface to be sharpened at one time. It can be observed in Moreover, since the moving means for moving the light source in the direction perpendicular to the optical path of the irradiation light is provided, stray light generated in the optical element due to the incidence of the irradiation light is guided to the detection surface provided in the detection means, which hinders observation. The situation is prevented.

According to the third aspect of the invention, the two-dimensional state of the sample surface can be sharpened at a time by the presence of the aperture stop disposed at a position corresponding to the rear image space focal plane of the optical element or in the vicinity thereof. It can be observed in Moreover, since the branching unit branches the reflected light from the sample surface from the optical path of the irradiation light before the reflected light re-enters the illumination optical system, the irradiation light does not directly enter the observation optical system, and the stray light is not generated. Is prevented from being guided to the detection surface provided in the detection means and obstructing the observation.

[0017]

Embodiments of the inspection apparatus according to the present invention will be described below.

FIG. 1 shows an inspection apparatus according to the first embodiment. Briefly explaining this device, the irradiation light emitted from the light source device 2 which is a point light source is deflected by the half mirror 5 in the orthogonal direction (lower side in the drawing), and the collimator lens 3 is irradiated.
After being made parallel to each other, the surface (hereinafter referred to as the sample surface) 4a of the plate-shaped sample 4 is irradiated from the normal direction. The reflected light from the sample surface 4a travels in the direction opposite to the irradiation light, is focused by the collimator lens 3, passes through the half mirror 5 having a function as a branching unit, and is branched from the optical path on the irradiation light side. , Collimating lens 3
The light enters the detection device 7 (detection means) having the aperture stop 6 at a position corresponding to the focal plane of the rear image space, and is detected as a projected image on the detection surface 71a behind the aperture stop 6. The detection device 7 is provided with a fine movement mechanism 8 which is a moving unit, and adjusts the position and inclination of the detection device 7.

The operation of this device will be briefly described. Since the presence of the aperture stop 6 in the detection device 7 blocks most of the scattered light that has not been reflected by the sample surface 4a in the normal direction, the detection device 7 On the detection surface 71a of No. 7, a clear projection image of the return light (specular reflection light) reflected in the normal direction by the sample surface 4a is formed.
Since the light-dark pattern of this projected image reflects the state of the unevenness or the like of the sample surface 4a, by observing the image output of the detection device 7, the two-dimensional change of the state of the sample surface 4a is minute. Distribution can be observed. Furthermore, since the fine movement mechanism 8 for the detection device 7 is provided,
The detection device 7 can be in a state of being removed from the optical axis of the collimator lens 3. As a result, it is possible to avoid a situation in which stray light generated by the collimator lens 3 enters the detection device 7, passes through the aperture stop 6 and forms a light spot on the detection surface 71a, and such light spot hinders observation. Such a problem does not occur.

Next, the inspection apparatus of FIG. 1 will be described in detail.

The light source device 2 uses a halogen lamp 21 as a light emitting source. The light emitted from the halogen lamp 21 is an elliptical reflector 22 composed of a dichroic mirror.
After being reflected by, the light passes through the heat ray absorbing filter 23 and is focused on the pinhole 24 having a diameter of 2 mm. The pinhole 24 illuminates the sample surface 4a and serves as a point source of irradiation light. A turret-shaped wavelength selection filter 25 including a plurality of interference filters is provided in front of the pinhole 24, and it is possible to appropriately change the wavelength of irradiation light that illuminates the sample surface. This wavelength selection filter 25 is used to adjust the sensitivity of the optical system part of the inspection device, and
When the peak-to-valley of the unevenness of a is small, a region having a short wavelength is selected.

The irradiation light from the light source device 2 is reflected by the half mirror 5 and then enters the collimator lens 3. The collimator lens 3 is an apochromat lens having a diameter of 6 inches (F7.1) using a special low dispersion glass,
The irradiation light diffused from the pinhole 24 of the light source device 2 is converted into a parallel light flux and made incident on the sample surface 4a. That is,
The collimator lens 3 is installed so that the pinhole 24 is located at the position of the focal plane of the front image space.

The sample 4 on which the parallel light flux from the collimator lens 3 is incident is placed on the tilt stage 41. The tilt stage 41 finely adjusts the tilt of the sample 4 so that the parallel light flux of the irradiation light is vertically incident on the sample surface 4a. The reflected light from the sample surface 4a again enters the collimator lens 3 and the beam diameter is narrowed.

The reflected light whose beam diameter is narrowed by the collimator lens 3 passes through the half mirror 5 and is branched from the optical path of the incident light. The half mirror 5 is a flat plate beam splitter, but is a half mirror with a wedge in which a predetermined minute angle is provided between the two planes. Therefore, the unnecessary ghost light generated due to the reflection on the upper transparent surface is an optical path of the reflected light, that is, the collimator lens 3
Deviate from the optical axis of. As a result, the ghost light is detected by the detection device 7
Will not be detected in. The minute angle provided on the half mirror 5 is set, for example, so that ghost light does not enter the detection device 7 (so that the ghost light is blocked by the entrance pupil of the camera lens 72 of the detection device 7).

The necessary reflected light branched from the optical path of the irradiation light by the half mirror 5 enters a zoom type camera lens 72 provided in the detection device 7. Camera lens 72
An aperture stop 6 is arranged at a light collecting position inside. That is, the aperture stop 6 is arranged at the position corresponding to the rear image space focal plane of the collimator lens 3. Therefore, most of the scattered light scattered on the sample surface 4a is blocked by the aperture stop 6. The aperture stop 6 is an iris stop having 10 blades, and the diameter of the circular aperture can be continuously changed by moving the movable adjusting portion. By changing the diameter of the circular opening, an optical image suitable for the type of inspection (waviness inspection, dimple inspection, scratch inspection, etc.) can be obtained.

Sample surface 4a passing through the camera lens 72
The reflected light from the camera is a 1/2 inch type CCD camera 7.
It is projected on one detection surface 71a. The image signal from the CCD camera 71 is once converted into an electric signal, processed by an appropriate signal processing device, and then sequentially displayed on a monitor (not shown) as a reconstructed image. In this case, CCD
The image projected on the detection surface 71a of the camera 71 has a two-dimensional bright-dark pattern corresponding to the state of the sample surface 4a.

More specifically, the light-dark pattern of the image projected on the detection surface 71a of the CCD camera 71 is composed of only the reflected light from the sample surface 4a that has passed through the aperture stop 6. That is, most of the scattered light not reflected in the normal direction on the sample surface 4a is
The return light that is blocked by the aperture stop 6 and reflected in the normal direction of the sample surface 4 a passes through the aperture stop 6. In addition, the light projected on each position in the bright and dark pattern formed by such return light has a one-to-one correspondence with each position on the sample surface 4a. Therefore,
The light-dark pattern of the image projected on the detection surface 71a of the CCD camera 71 reflects minute changes such as unevenness of the sample surface 4a. By observing the image output of the CCD camera 71, the sample surface It is possible to accurately observe the two-dimensional distribution of minute changes in the state of 4a.

FIG. 2 shows a detection device 7 including a CCD camera 71 and a camera lens 72, and a fine movement device 8 for adjusting the position and inclination of the detection device 7. By this fine movement device 8, the light spot caused by the stray light from the collimator lens 3 can be removed from the image output of the CCD camera 71. The fine movement device 8 has a two-axis tilt mechanism that adjusts the detection device 7 to a desired tilt with respect to the optical axis 9 of the collimator lens 3, and a desired position of the detection device 7 in a plane perpendicular to the optical axis 9 of the collimator lens 3. Adjust to position 2
And an axis xy moving mechanism. By appropriately operating the two-axis tilt mechanism and the two-axis xy moving mechanism, the CCD camera 71, the camera lens 72, and the aperture stop 6 are appropriately tilted with respect to the optical axis 9 of the collimator lens 3, or in a direction perpendicular to the optical axis 9. It will be moved. If the movement amounts of the CCD camera 71 and the camera lens 72 are appropriate, the light source device 2
The stray light generated by the reflected light from the surfaces of the lenses forming the collimator lens 3 before being incident on the sample surface 4a is detected by the detection surface 71a of the CCD camera 71.
Can be effectively prevented from reaching. That is, since the stray light generated by the collimator lens 3 travels along the optical axis 9 of the collimator lens 3, the stray light is 2
By operation of a shaft tilt mechanism or the like, it reaches the outside of the detection surface 71a of the CCD camera 71, or is blocked by the aperture stop 6, the camera lens 72, etc. located at a position off the optical axis. As a result, it is possible to prevent a situation in which a light spot due to stray light from the collimator lens 3 is projected on the detection surface 71a and hinders observation.

The detection surface 7 is adjusted by using the fine movement device 8.
A specific method of removing the light spot for preventing the light spot from being projected on the surface 1a will be described.

FIG. 3A is a diagram showing an image output of the CCD camera 71 before adjustment using the fine movement device 8. An ID number 101, which is an index, is imprinted near the orientation flat of the semiconductor wafer 100. If the optical axis of the inspection device is accurate, the light spot 102 appears at the center of the screen. Therefore, it becomes difficult or impossible to identify the ID number 101.

FIG. 3B is a diagram showing the image output of the CCD camera 71 after the adjustment using the fine movement device 8. By tilting the detection device 7 to a desired angle by the two-axis tilting mechanism of the fine movement device 8, the optical axis of the detection device 7 is intentionally set from the optical axis of the collimator lens 3 which is the optical axis of the illumination optical system for irradiation light. Shift. As a result, the light spot 102 appearing in the center of the screen can be removed to the outside of the screen,
It becomes easy to identify the ID number 101. By enabling the biaxial tilt, the light spot 102 can be moved not only in the upward direction as shown, but also in the horizontal direction.

However, as shown in FIG. 3B, the optical axis of the camera lens 72 or the like is tilted only by the biaxial tilting mechanism, and vignetting may occur at the bottom of the screen. The biaxial xy moving mechanism is adjusted to prevent this vignetting. The problem of vignetting can be solved by moving the detection device 7 in a plane perpendicular to the optical axis of the collimator lens 3. However, since the light spot comes into the screen again, the biaxial tilt mechanism is readjusted. Further, if necessary, the tilt stage 41 is adjusted to obtain the desired brightness, contrast, etc. of the sample image.

Although the present invention has been described with reference to the first embodiment, the present invention is not limited to the first embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the inspection device of the first embodiment,
As the fine movement device 8, a combination of a two-axis tilt mechanism and a two-axis xy movement mechanism was used, but the two-axis xy movement mechanism is provided in parallel to each of the CCD camera 71 and the camera lens 72 without using the two-axis tilt mechanism. It may be a moving optical system. FIG. 4A is a schematic view showing a basic arrangement before adjustment by such a parallel movement type fine movement device. In this basic arrangement, a light spot similar to the light spot 102 shown in FIG. 3A appears on the screen. FIG. 4B is a diagram showing the arrangement after adjustment using the fine movement device. In this arrangement, stray light from the collimator lens 3 does not enter the detection device, and the light spot does not appear in the center of the screen. In order to effectively eliminate the ghost light due to the back surface reflection of the wedge type half mirror 5 which is thickened in the upper right direction of the drawing, C
The moving directions of the CD camera 71 and the camera lens 72 are leftward in the drawing as illustrated.

When the parallel moving optical system as shown in FIG. 4B is used, there is a problem that vignetting occurs unless the detecting device 7 having a wide field angle range is used. This problem is solved, for example, by using a 1/2 inch CCD mounted on a camera having a larger 2/3 inch angle of view as the CCD camera 71. Alternatively, the camera lens 72
The problem is solved by using a 35 mm camera instead of a CCD.

Further, as the fine movement device 8, the one having only the two-axis tilt mechanism for the detection device 7 is used, and the rotation center of the tilt is set in advance at an appropriate position on the optical axis of the collimator lens 3. Thus, it is possible to remove the light spot outside the screen while preventing vignetting.

Further, a biaxial xy moving mechanism having only the aperture stop 6 or a biaxial xy moving mechanism having only the CCD camera 71 may be provided. That is, it is possible to use various mechanisms capable of moving the light spot relative to the required sample image.

Further, in the inspection device of the first embodiment,
Although the fine movement device 8 for adjusting the position and inclination of the detection device 7 is provided, a fine movement device for adjusting the position of the light source device 2 may be provided instead. By appropriately adjusting the fine movement mechanism for the light source device 2, the point light source can be placed in a state of being off the optical axis of the collimator lens 3.
As a result, it is possible to avoid a situation in which stray light generated by the collimator lens 3 enters the detection device 7 arranged on the optical axis of the collimator lens 3 and forms a light spot on the detection surface 71a. There is no problem that observation is obstructed by the light spot.

Various changes can be made to other parts. For example, the positional relationship between the light source device 2 and the detection device 7 can be replaced. That is, the irradiation light from the light source device 2 is guided to the collimator lens 3 after passing through the half mirror 5, and the reflected light from the sample surface 4a is focused by the collimator lens 3 and deflected by the half mirror 5, and then finely moved. It may be configured to lead to the detection device 7 including the device 8.

Further, in the inspection device of the first embodiment,
Although the case where the halogen lamp 21 is used as the light emitting source of the light source device 2 has been described, a xenon lamp or the like can be used as the light emitting source. What is used as the light emission source is determined by the property of the inspection object (sample 4).
For example, in the case of inspecting a semiconductor wafer having a relatively high reflectance, either a halogen lamp or a xenon lamp may be used, but a glass substrate having a relatively low reflectance may be used. When inspecting, it is preferable to use a xenon lamp with high brightness. Therefore, the light emitting source may be appropriately changed depending on the property of the inspection object.

Further, in the inspection device of the first embodiment,
Although the light source device 2 focuses light on the pinhole 24 by the elliptical reflector 22, a parabolic reflector may be used instead of the elliptic reflector 22. In this case, since the light emitted from the parabolic reflector travels in parallel to the optical axis, a collimator lens may be separately provided and focused by the collimator lens at the pinhole. A condenser lens is used instead of the elliptical reflector 22, and the condenser lens is used for the halogen lamp 2
It can also be arranged between 1 and the pinhole 24.

Further, the light source device 2 can be constructed by using a light guide fiber having a rod lens at the entrance and exit ends. In this case, the halogen lamp 21 is installed at one focus of the elliptical reflector 22 and
The end surface of the incident side rod lens is arranged at the other focal point of 2. The light emitted from the halogen lamp 21 is focused by the elliptical reflector 22 and is incident on the incident side rod lens.
It is coupled to the light guide fiber and transmitted to be coupled to the output side rod lens at the other end. The outgoing light from the outgoing rod lens is focused on the pinhole 24.

In this case, it is also possible to use an optical waveguide rod rod in which the same glass material as the core of the light guide fiber is solidified into a rod shape having a circular cross section, without using the rod lens. By arranging this optical waveguide rod rod at the entrance and exit ends of the light guide fiber, the light emitted from the halogen lamp 21 can be coupled to the light guide fiber, and the pinhole 2 after being transmitted through the light guide fiber.
The irradiation light that has passed through 4 can be diverged with a sufficiently large divergence angle.

Further, a configuration in which the rod lens is replaced with a conical mirror is also possible. In this case, the light emitted from the light guide fiber is reflected by the conical mirror in the pinhole 2
It is focused on 4.

Further, it is possible to use a type in which the collimator lens 3 is directly irradiated from the exit side of the light guide fiber without using the rod lens.

Further, in the inspection device of the first embodiment,
Although the pinhole 24 is used for forming the point light source, it may be a slit. In this case, the emission angle of the irradiation light from the light source can be widened.

Further, in the inspection device of the first embodiment,
Although the case where the interference filter is used as the wavelength selection filter 25 has been described, for example, a colored glass filter can also be used. Further, the wavelength selection filter 25 is not an indispensable element, and its installation place is also arbitrary.

Furthermore, in the inspection apparatus of the first embodiment,
Although the case where only the wavelength selection filter 25 is used has been described, an ND filter may be installed together with the wavelength selection filter 25 or in place of the wavelength selection filter 25. The ND filter is used for the purpose of dimming the incident light without changing the spectral characteristics. The dimming in this case is necessary for detecting, for example, the undulation of the sample surface 4a. In the case of a gradual surface change such as undulation, the specular component of light is extremely large, so the brightness of the sample surface 4a is too high, and unless dimmed, the entire reflected image becomes too bright and difficult to observe. Is. In this case, the halogen lamp 21 may be replaced with one having a low brightness, but the work is easier by using the ND filter.

Furthermore, in the inspection device of the first embodiment,
Although a special device for keeping the output of the irradiation light from the light source device 2 constant was not provided, a part of the irradiation light from the light source device 2 that is not reflected by the wedge type half mirror 5 and passes through this By detecting with a photodiode or the like and controlling the power supply voltage of the halogen lamp 21 based on the detection output of this photodiode, the output of the irradiation light from the light source device 2 can be stabilized.

Further, in the inspection device of the first embodiment,
Although the case where the apochromat lens is used as the collimator lens 3 has been described, the achromat lens may be used as the collimator lens 3. However,
When inspecting using narrow band monochromatic light, achromaticity is not always necessary. However, it is preferable to use the collimator lens 3 having small aberrations in order to prevent light loss as much as possible.

Further, the collimator lens 3 having various apertures and focal lengths can be used depending on the use of the inspection device. However, for the purpose of detecting an index or the like formed on the surface of a semiconductor wafer or the like, it is generally preferable to use it in the range of F4 to F15.

Further, in the inspection device of the first embodiment,
The case of inspecting the flat plate-shaped sample 4 has been described, but in the case of surface inspection of a cylinder or the like, a cylindrical lens is used,
Further, in the case of inspecting the surface of a sphere or the like, a plano-convex lens may be used to irradiate the sample surface with light in the normal direction. Further, in some cases, even in the case of the flat plate-shaped sample 4, it is possible to use a cylindrical lens to emphasize the unevenness in a certain direction for observation.

Further, in the inspection device of the first embodiment,
The case where a flat plate beam splitter is used as the wedge type half mirror 5 has been described, but various flat plate or thin film half mirrors can be used. For example, a pellicle mirror may be used as the half mirror 5. Further, a cube type beam splitter can be used.

Further, in the inspection device of the first embodiment,
Although the CCD camera 71 is used for observation, an optical system for observation with a screen or a still camera may be used.
Furthermore, instead of the CCD camera 71, a photoelectric tube such as Photomal may be used.

Further, the video signal (original video signal) included in the video signal input from the CCD camera 71 is differentiated,
It is possible to display an image by emphasizing the weak contrast difference by a differentiating process such as adding the obtained differential signal and the original video signal to obtain a new video signal. Further, it is possible to provide a brightness adjusting circuit capable of arbitrarily setting the brightness of the added new video signal. By this brightness adjustment,
For example, when observing the inner state of the contour portion such as the uneven portion or the contour portion itself, the image can be observed with a brightness that is easy to see.

Further, in the inspection device of the first embodiment,
Although the iris diaphragm built in the zoom lens 72 is used as the aperture diaphragm 6, an aperture diaphragm having a fixed circular aperture is provided, and the aperture diaphragm is provided near the position corresponding to the rear image space focal plane in the optical axis direction. It may be used by moving it back and forth.

Further, in the inspection device of the first embodiment,
Although the case where the zoom type camera lens 72 is used has been described, a fixed focus lens may be used instead. For example, a commercially available single-lens reflex camera lens can be used.

FIG. 5 shows the inspection apparatus of the second embodiment. To briefly describe this device, the irradiation light emitted from the light source device 2 which is a point light source is once collimated by the elliptical mirror 30 which is an illumination optical system, and then reflected by the total reflection mirror 32 and the half mirror 50. The sample surface 4a is irradiated from the normal direction. This sample surface 4a
The reflected light from travels in the direction opposite to the irradiation light, passes through the half mirror 50 that is a branching unit, is branched from the optical path on the irradiation light side, and then is focused by the collimating lens 31 that is an optical element for observation. The collimator lens 31 is incident on a camera lens 72 having a built-in aperture stop 60 at a position corresponding to the focal plane of the rear image space, and is detected by a CCD camera 71 behind the camera lens 72.

The operation of this apparatus will be briefly described. Since the presence of the aperture stop 60 in the camera lens 72 blocks most of the scattered light which is not reflected in the normal direction of the sample surface 4a, a CCD camera is provided. A clear projection image is formed on the detection surface 71 by the specularly reflected light from the sample surface 4a. The bright and dark pattern of this projected image reflects the state of the unevenness or the like of the sample surface 4a. Therefore, by observing the image output of the CCD camera 71, a slight change in the state of the sample surface 4a can be detected.
The dimensional distribution can be observed. Further, the half mirror 50 is provided between the collimator lens 31 and the sample surface 4a.
Is provided, and strong irradiation light from the light source device 2 does not directly enter the collimator lens 31, so that generation of stray light can be suppressed. Therefore, there is no problem that stray light resulting from direct light from the light source passes through the aperture stop 60 to form a light spot on the detection surface of the CCD camera 71, and such light spot hinders observation. With such a configuration, the entire length of the optical system part,
Although the size such as the width is increased, a simple structure without the fine movement device as in the first embodiment can be provided, and the operation required for adjustment for removing the light spot can be omitted. You can

Next, the inspection device of FIG. 5 will be described in detail. The same parts as those in the first embodiment of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The irradiation light from the halogen lamp 21, which is the light source of the light source device 2, is reflected by the elliptical reflector 22.
The light passes through the heat ray absorbing filter 23 and is focused on the pinhole 24. The irradiation light that has passed through the pinhole 24 is diffused by the integrator 27.

The irradiation light emitted from the light source device 2 and diffused is reflected by the elliptical mirror 30 and converted into a parallel light beam.
After the optical path is deflected by the total reflection mirror 32, the light enters the half mirror 50. The irradiation light reflected and deflected by the half mirror 50 enters the sample surface 4a as a parallel light flux.

The reflected light reflected in the opposite direction on the sample surface 4a passes through the half mirror 50 and is branched from the optical path of the incident light, and then the apochromat type collimating lens 3 is formed.
Incident on 1. The half mirror 50 is a wedge type flat plate beam splitter in which a minute angle is provided between two planes. Therefore, the ghost light generated due to the reflection on the upper transparent surface deviates from the optical path of the reflected light, that is, the optical axis of the collimator lens 31. As a result, the ghost light is no longer detected on the detection device 7 side.

The reflected light whose beam diameter is narrowed by the collimator lens 31 is reflected by the camera lens 72 provided in the detection device 7.
Incident on. An aperture stop 60 is arranged at a light collecting position inside the camera lens 72. The aperture stop 60 is formed by arranging a pair of knife-edge type slits so as to be orthogonal to each other. As a result, the size of the opening can be easily adjusted, and the resolution can be improved by forming a minute opening.

The light emitted from the camera lens 72 is CCD
It is projected on the detection surface of the camera 71. The image projected on this detection surface has a two-dimensional bright-dark pattern corresponding to the state of the sample surface 4a. In this case, a light spot due to the collimator lens 31 or the like does not occur.

More specifically, the collimating lens 31
And a half mirror 50 between the sample surface 4a and
Since the irradiation light reflected by the half mirror 50 directly enters the sample surface 4a, the strong irradiation light from the light source device 2 does not directly enter the collimator lens 31, and the generation of stray light in the collimator lens 31 is suppressed. it can. That is, the light incident on the collimator lens 31 is reflected by the sample surface 4
Since only the relatively weak reflected light from a is generated, stray light is unlikely to be generated by the collimator lens 31, and even if stray light is generated, a light spot is not formed on the detection surface of the CCD camera 71, and such a light spot is generated. The problem that observation is obstructed does not occur.

Although the present invention has been described with reference to the second embodiment, the present invention is not limited to the second embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the inspection device of the second embodiment,
Although the irradiation light from the light source device 2 is converted into the parallel light flux using the elliptical mirror 30, the irradiation light from the light source device 2 may be converted into the parallel light flux using another collimator lens. Figure 6
Shows the configuration example. Light emitted from the halogen lamp 21 of the light source device is reflected by the total reflection mirror 32 while being diffused through a pinhole (not shown), and then collimated by the collimating lens 33 for illumination below the light shielding wall 34. It
The irradiation light is reflected by the half mirror 50, and then is irradiated onto the sample surface 4a from the normal direction thereof. The reflected light from the sample surface 4a travels in the direction opposite to the irradiation light, passes through the half mirror 50, is branched from the optical path on the irradiation light side, and is then focused by the collimating lens 31 for observation. The reflected light enters a camera lens 72 having an aperture stop at a position corresponding to the focal plane of the rear image space of the collimator lens 31, and is detected as a projected image on the detection surface of the CCD camera 71 behind the collimator lens 31.

Further, instead of the elliptical mirror 30 and the collimating lens 33 for illumination, a parabolic mirror or a spherical mirror can be used. By arranging the pinhole 24 of the light source device 2 at the focal point of the parabolic mirror, it is possible to obtain irradiation light of a perfect parallel light flux.

[0070]

According to the present invention, a two-dimensional state of a sample surface can be clearly observed at a time by the presence of an aperture stop arranged at a position corresponding to the focal plane of the rear image space of an optical element or in the vicinity thereof. it can. Here, a detecting means or a moving means for moving the light source is provided, or a branching means is provided for branching the reflected light from the sample surface from the optical path of the irradiation light before the reflected light re-enters the illumination optical system. Therefore, it is possible to prevent a situation in which the stray light generated in the optical element due to the direct incidence of the irradiation light passes through the aperture stop and is guided to the detection surface provided in the detection means to hinder the observation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inspection device according to a first embodiment.

FIG. 2 is a partially enlarged view of the inspection device according to the first embodiment.

FIG. 3 is a diagram showing a specific method of removing a light spot.

FIG. 4 is a schematic configuration diagram showing a modified example of the inspection apparatus of the first embodiment.

FIG. 5 is a configuration diagram of an inspection device according to a second embodiment.

FIG. 6 is a schematic configuration diagram showing a modified example of the inspection apparatus of the second embodiment.

[Explanation of symbols]

 2 light source 3 optical elements 30, 32, 33 illumination optical system 31 observation optical system 4a sample surface 5, 50 branching means 6, 60 aperture stop 6, 7, 60 detecting means 8 moving means

Claims (3)

[Claims] 1. An optical element that guides the irradiation light from a light source to the sample surface and focuses the reflected light returning from the sample surface; and the reflected light from the sample surface, which reflects the optical element. The reflection means having branching means for branching from the optical path of the irradiation light after passing and an aperture stop arranged at a position corresponding to the rear image space focal plane of the optical element or in the vicinity thereof, and having passed through the aperture stop. An inspection apparatus comprising: a detection unit that detects a light image; and a moving unit that moves the detection unit in a direction perpendicular to the optical path of the reflected light. 2. An optical element which guides the irradiation light from a light source to the sample surface and focuses the reflected light returning from the sample surface; and the reflected light from the sample surface, which reflected light causes the optical element to The reflection means having branching means for branching from the optical path of the irradiation light after passing and an aperture stop arranged at a position corresponding to the rear image space focal plane of the optical element or in the vicinity thereof, and having passed through the aperture stop. An inspection apparatus comprising: a detection unit that detects an image of light; and a moving unit that moves the light source in a direction perpendicular to the optical path of the irradiation light. 3. An illumination optical system for guiding irradiation light from a light source to a sample surface, and reflected light returning from the sample surface from an optical path of the irradiation light before the reflected light re-enters the illumination optical system. An observing optical system including a branching unit for branching, an optical element for focusing the reflected light branched by the branching unit, and an aperture arranged at a position corresponding to a rear image space focal plane of the optical element or in the vicinity thereof. An inspection apparatus comprising: a diaphragm.