JP2006250843A - Surface inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection device capable of coping with micro-fineness in repetition pitches, without shortening a wavelength of illumination light. <P>SOLUTION: This device is provided with a light source means Ls for emitting a dispersed light beam for illuminating an inspected substrate 20, an irradiation member 35 for making the dispersed beam get incident to bring a principal light beam thereof into a prescribed incident angle, so as to be guided to the inspected substrate, image focusing means 36, 37 for converging light from the inspected substrate to image-focus an image of the inspected substrate, an imaging means 39 for picking up the focused image, the first polarization plate 34 provided in an optical path from the light source means to the irradiation member, the second polarization plate 38 provided in an optical path from the image focusing means to the imaging means, a turning means for turning at least one of the first polarization plate and the second polarization plate, within a plane perpendicular to an optical axis, and a detection means 15 for detecting a defect on a surface of the inspected substrate, based on the images obtained, by the imaging means, in a plurality of turn positions by the turning means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface inspection apparatus for inspecting the surface of a substrate such as a semiconductor element.

2. Description of the Related Art Conventionally, a device using diffraction is known as an inspection device for a defect of a repeated pattern formed on the surface of a wafer in a manufacturing process of a semiconductor circuit element or the like. In an apparatus using diffraction, it is necessary to adjust the tilt angle of the stage according to the pattern pitch. In order to cope with finer patterns, it is necessary to shorten the wavelength of illumination light.
Japanese Patent Laid-Open No. 10-232122

  However, in order to cope with repetitive pitch miniaturization (that is, line and space miniaturization of wiring patterns, etc.), when trying to shorten the wavelength of illumination light, the types of light sources are limited, which is expensive and large. It becomes a light source. Further, the material of the optical element constituting the illumination system and the light receiving system is also limited to an expensive material, which is not preferable.

  An object of the present invention is to provide a surface inspection apparatus that can reliably cope with repetitive miniaturization of the pitch without shortening the wavelength of illumination light.

In order to solve the above problems, the invention of claim 1
Light source means for emitting a divergent light beam for illuminating the substrate to be inspected;
An irradiating member that guides the divergent light beam so that a principal ray of the light beam has a predetermined incident angle and guides it to the test substrate;
Imaging means for condensing light from the test substrate and forming an image of the test substrate; Imaging means for capturing the image formed;
A first polarizing plate provided in an optical path from the light source means to the irradiation member;
A second polarizing plate provided in an optical path from the imaging means to the imaging means;
Rotating means for rotating at least one of the first polarizing plate and the second polarizing plate in a plane perpendicular to the optical axis;
And detecting means for detecting defects on the surface of the substrate to be inspected based on images obtained by the imaging means at a plurality of rotation positions by the rotation means.

The invention of claim 2
The surface inspection apparatus according to claim 1,
The rotating means can be rotated to a position where the first polarizing plate and the second polarizing plate are in a crossed Nicols state.

The invention of claim 3
Light source means for emitting a divergent light beam for illuminating the substrate to be inspected;
An irradiating member that guides the divergent light beam so that a principal ray of the light beam has a predetermined incident angle and guides it to the test substrate;
Imaging means for condensing light from the test substrate and forming an image of the test substrate; Imaging means for capturing the image formed;
A first polarizing plate provided in an optical path from the light source means to the irradiation member;
A second polarizing plate provided in an optical path from the imaging means to the imaging means and arranged to be in a crossed Nicols state with the first polarizing plate;
Moving means for moving the test substrate relative to a region illuminated by the irradiation member in a direction parallel to the surface of the test substrate;
And detecting means for detecting defects on the surface of the substrate to be inspected based on images obtained by the imaging means at a plurality of movement positions by the moving means.

  According to the present invention, it is possible to cope with inspection of a substrate having a repetitive fine pitch without shortening the wavelength of illumination light.

  FIG. 1 is a diagram showing a configuration of a surface inspection apparatus according to an embodiment of the present invention. In FIG. 1, the surface inspection apparatus includes a stage 11 that supports a semiconductor wafer 20 that is a substrate to be tested, an alignment system 12, an illumination optical system 13, a light receiving optical system 14, and an image processing apparatus 15. Yes. The surface inspection apparatus is an apparatus that automatically inspects the surface of the semiconductor wafer 20 in the manufacturing process of the semiconductor circuit element. After exposure / development of the uppermost resist film, the semiconductor wafer 20 is carried from a wafer cassette (not shown) or a developing device by a conveyance system (not shown) and is attracted to the stage 11.

  In FIG. 1, a lamp house LS includes a light source such as a halogen lamp, a metal halide lamp, and a mercury lamp (not shown), a wavelength selection filter, an ND filter for adjusting the amount of light, and the like. Only the light is extracted as illumination light L 1 and is incident on the light guide fiber 33. The illumination optical system 13 includes a light guide fiber 33, a polarizing plate 34, and a concave reflecting mirror 35. The illumination light L1 that is a divergent light beam emitted from the light guide fiber 33 is converted into substantially parallel light by the spherical concave reflecting mirror 35, and illuminates the wafer 20 placed on the stage 11.

  A polarizing plate 34 is disposed in the vicinity of the emission portion of the light guide fiber 33, and the illumination light L1 emitted from the light guide fiber 33 is linearly polarized. The light that has been linearly polarized by the polarizing plate 34 is collimated by the concave reflecting mirror 35, and the linearly polarized collimated light illuminates the wafer 20.

  In order to improve the throughput, it is extremely advantageous to collect images of the entire wafer surface in a lump. In this embodiment, as described above, the luminous flux from the light source is expanded and collimated by the concave reflecting mirror 35. The entire surface of the wafer can be illuminated.

  The linearly polarized collimated light L 1 incident on the wafer 20 is reflected by the wafer surface and enters the light receiving optical system 14. The light receiving optical system 14 includes a concave reflecting mirror 36, a polarizing plate 38, and a condenser lens 37. The light beam L2 reflected by the wafer 20 enters the concave reflecting mirror 36 and receives a condensing action. The condensed light beam reflected by the concave reflecting mirror 36 passes through a polarizing plate 38 disposed in a crossed Nicols relationship with the polarizing plate 34, and is imaged by the imaging lens 37 at a position conjugate with the surface of the wafer 20. An image of the surface of the wafer 20 is formed on the imaging surface 39.

  As shown in FIG. 2, a plurality of chip areas 21 are arranged in the XY direction on the surface of the semiconductor wafer 20, and a repeated pattern 22 is formed in each chip area 21. The arrangement direction (X direction) of the line portions of the repetitive pattern 22 is referred to as “repetitive direction of the repetitive pattern 22”.

  In the present embodiment, it is assumed that the pitch P of the repeating pattern 22 is sufficiently small as compared with the wavelength of illumination light with respect to the repeating pattern 22. For this reason, diffracted light is not generated from the repeated pattern 22. The principle of defect inspection in the present embodiment is described in Japanese Patent Application No. 2003-366255 already filed by the present applicant, so the principle will not be described in detail here.

  On the surface of the stage 11, the wafer 20 on which the above-mentioned pattern is formed is placed and fixed and held by vacuum suction or the like. Further, the stage 11 is configured to be rotatable around a predetermined rotation axis orthogonal to the stage surface by a stage rotation mechanism 16. With this stage rotation mechanism 16, the angle formed by the longitudinal direction of the repeated pattern formed on the surface of the wafer 20 with respect to the linearly polarized vibrating surface of the light beam L1 that illuminates the wafer 20 can be set to an arbitrary angle.

  In the surface inspection apparatus of FIG. 1, an alignment system for detecting the orientation of the pattern formed on the surface of the wafer 20 placed on the stage 11 between the concave reflecting mirror 35 and the concave reflecting mirror 36. 12 is arranged, and an angle formed by a preset linearly polarized vibrating surface of the light beam L1 and the longitudinal direction Y of the repeated pattern 22 is detected, and the stage rotating mechanism 16 is used to detect the illumination optical system 13 and the light receiving optical system 14. The direction of the longitudinal direction Y of the repeated pattern can be adjusted.

  The alignment system 12 illuminates the outer edge of the semiconductor wafer 20 when the stage 11 is rotating, detects the position in the rotation direction of an external reference (for example, a notch) provided on the outer edge, and moves the stage at a predetermined position. 11 is stopped. As a result, the repetitive direction (X direction in FIG. 2) of the repetitive pattern 22 of the semiconductor wafer 20 can be set to be inclined at an angle of 45 degrees with respect to the illumination light incident surface 3A (see FIG. 3) described later. it can.

  In the present embodiment, the linearly polarized light beam L1 is P-polarized light. That is, as shown in FIG. 4A, a plane including the traveling direction of the linearly polarized light L1 and the vibration direction of the vector (the vibrating surface of the linearly polarized light L1) is included in the incident surface (3A) of the linearly polarized light L1. . The vibration plane of the linearly polarized light L <b> 1 is defined by the transmission axis of the polarizing plate 34 disposed in front of the concave reflecting mirror 35.

  In this embodiment, since the linearly polarized light L1 incident on the semiconductor wafer 20 is P-polarized light (FIG. 4A), the repeat direction (X direction) of the repeat pattern 22 of the semiconductor wafer 20 is a straight line as shown in FIG. When the angle is set to 45 degrees with respect to the incident surface (3A) of the polarized light L1, the direction of the vibration surface of the linearly polarized light L1 on the surface of the semiconductor wafer 20 (the V direction in FIG. 5) and the repeated direction of the repeated pattern 22 The angle formed with the (X direction) is also set to 45 degrees.

  In other words, the linearly polarized light L1 has the repeating pattern 22 in a state where the direction of the vibration surface (the V direction in FIG. 5) on the surface of the semiconductor wafer 20 is inclined 45 degrees with respect to the repeating direction (X direction) of the repeating pattern 22. Is incident on the repetitive pattern 22 in a state of crossing diagonally.

  Such an angle state between the linearly polarized light L1 and the repeated pattern 22 is uniform over the entire surface of the semiconductor wafer 20. Note that the angle state between the linearly polarized light L1 and the repetitive pattern 22 is the same even if 45 degrees is replaced with any of 135 degrees, 225 degrees, and 315 degrees. The reason why the angle formed by the vibration plane direction (V direction) and the repeat direction (X direction) in FIG. 5 is set to 45 degrees is to maximize the sensitivity of the defect inspection of the repeat pattern 22.

  When the repeating pattern 22 is illuminated using the linearly polarized light L1, the elliptically polarized light L2 is generated from the repeating pattern 22 in the regular reflection direction (FIGS. 1 and 4B). In this case, the traveling direction of the elliptically polarized light L2 coincides with the regular reflection direction. The regular reflection direction is a direction that is included in the incident surface (3A) of the linearly polarized light L1 and is inclined with respect to the normal line 1A of the stage 11 by an angle equal to the incident angle of the linearly polarized light L1. As described above, since the pitch P of the repeated pattern 22 is sufficiently smaller than the illumination wavelength, no diffracted light is generated from the repeated pattern 22.

Next, the light receiving optical system 14 will be described. As shown in FIG. 1, the light receiving system 14 includes a concave reflecting mirror 36, an imaging lens 37, a polarizing plate 38, and an image sensor 39.
The concave reflecting mirror 36 is a reflecting mirror similar to the concave reflecting mirror 35 of the illumination optical system 13, and reflects the elliptically polarized light L2 toward the imaging lens 37 and cooperates with the imaging lens 37. The light is condensed on the imaging surface of the image sensor 39.

  However, a polarizing plate 38 is disposed between the imaging lens 37 and the concave reflecting mirror 36. The direction of the transmission axis of the polarizing plate 38 is set so as to be orthogonal to the transmission axis of the polarizing plate 34 of the illumination optical system 13 described above (crossed Nicol state). Therefore, the polarizing plate 38 can extract only the polarization component corresponding to the polarization component L3 of the elliptically polarized light L2 in FIG. As a result, a reflection image of the semiconductor wafer 20 is formed on the imaging surface of the imaging element 39 by the polarization component corresponding to the polarization component L3 in FIG.

  The image sensor 39 is, for example, a CCD image sensor or the like, photoelectrically converts a reflected image of the semiconductor wafer 20 formed on the imaging surface, and outputs an image signal to the image processing device 15. The brightness of the reflected image of the semiconductor wafer 20 is substantially proportional to the magnitude of the polarization component L3 in FIG. 4C, and the reflected image of the semiconductor wafer 20 is brightest when the repetitive pattern 22 has an ideal shape. It is. Note that the brightness of the reflected image of the semiconductor wafer 20 appears for each shot area.

  The image processing device 15 captures a reflected image of the semiconductor wafer 20 based on the image signal output from the image sensor 39. Note that the image processing apparatus 15 stores in advance a reflection image of a non-defective wafer for comparison. A non-defective wafer is one in which the repeated pattern 22 is formed on the entire surface in an ideal shape. It is considered that the luminance information of the reflected image of the non-defective wafer shows the highest luminance value.

  Therefore, when the image processing apparatus 15 captures the reflection image of the semiconductor wafer 20 that is the test substrate, the image processing apparatus 15 compares the luminance information with the luminance information of the reflection image of the non-defective wafer. Then, the defect of the repetitive pattern 22 is detected based on the amount of decrease in the luminance value in the dark part of the reflected image of the semiconductor wafer 20. For example, if the amount of decrease in luminance value is larger than a predetermined threshold (allowable value), it is determined as “defect”, and if it is smaller than the threshold, it is determined as “normal”.

  As described above, according to the surface inspection apparatus of the present embodiment, the linearly polarized light L1 is used, and the vibration surface direction (V direction) in FIG. 5 is inclined with respect to the repeating direction (X direction) of the repeating pattern 22. In order to illuminate the repetitive pattern 22 and detect defects in the repetitive pattern 22 based on the magnitude of the polarization component L3 in FIG. 4C among the elliptically polarized light L2 generated in the regular reflection direction, the illumination wavelength Even if the pitch P of the repeated pattern 22 is sufficiently small as compared with the above, the defect inspection can be surely performed. That is, even if the linearly polarized light L1 that is illumination light is not shortened in wavelength, it is possible to reliably cope with repetitive miniaturization of the pitch.

Next, the polarization state of the light beam incident on and reflected by the concave reflecting mirror 35 will be described.
In FIG. 1, with respect to the concave reflecting mirror 35, a plane including the principal ray AX1 of the linearly polarized light L1 incident on the concave reflecting mirror and parallel to the optical axis O35 of the concave reflecting mirror is incident on the incident surface of the linearly polarized light L1 incident on the concave reflecting mirror. It is. On the other hand, the illumination light L1 diverged in accordance with the numerical aperture of the light guide fiber 33 is converted into predetermined linearly polarized light by the polarizing plate 34 as described above, and the principal ray AX1 of the divergent light beam is the optical axis O35 of the concave reflecting mirror 35. In other words, it is a so-called off-axis optical system that is incident on a portion that is deviated from the above.

  Therefore, the light beam incident on the concave reflecting mirror 35 is not perpendicular to the concave reflecting mirror 35. Therefore, according to Frenel's reflection formula, a difference in transmittance occurs between the P component and S component of the polarized light, and as a result, the polarization plane rotates.

  For example, it is assumed that the polarization plate 34 generates linearly polarized light having a vibration surface (P-polarized light) parallel to the incident surface. In this case, assuming that the incident surface formed by the principal ray AX1 and the optical axis O35 is a reference incident surface, in the vicinity of the intersection of the concave reflecting mirror 35 including the optical axis O35 and a surface perpendicular to the incident surface, Although the polarization plane does not rotate, rotation occurs in other parts of the concave reflecting mirror 35. The plane of vibration of the polarized light rotates symmetrically with respect to the reference incidence plane in the plane of the concave reflecting mirror 35. The amount of this rotation is larger as the position is away from the optical axis O35 of the concave reflecting mirror. This is because the divergent light beam incident on the concave reflecting mirror 35 enters from a position deviated from the optical axis O35 of the concave reflecting mirror 35, and therefore the leftmost light of the light beam incident on the concave reflecting mirror 35 in FIG. This is because the incident angle is small and the rightmost light has an inclination that makes the incident angle largest (the incident angle is an angle between the incident light and the normal of the concave reflecting mirror surface).

As described above, since the incident angle of light with respect to the concave reflecting mirror is different (inclined) in the plane, a slight difference occurs in the rotation of the polarization plane in the plane, and unevenness of the extinction ratio in crossed Nicols occurs.
Further, the non-uniformity of the extinction ratio that occurs in the light receiving optical system 14 will be described. In FIG. 1, with respect to the concave reflecting mirror 36, a plane including the principal ray AX <b> 2 of the linearly polarized light L <b> 2 emitted from the concave reflecting mirror 36 and parallel to the optical axis O <b> 36 of the concave reflecting mirror The incident surface is a reference incident surface. On the other hand, the parallel light beam L2 reflected from the wafer 20 is incident on a portion of the concave reflecting mirror 36 that is off the optical axis O36 and receives a converging action, so that the light receiving optical system 14 is a so-called off-axis optical system. Yes.

  The rotation of the polarization plane of the convergent light beam emitted from the concave reflecting mirror 36 is the same as in the case of the illumination optical system 13 described above. In the concave reflecting mirror 36, the polarization vibration plane rotates in line symmetry with respect to the reference incident surface in the plane of the concave reflecting mirror 36. The amount of this rotation is larger as the distance from the optical axis O36 of the concave reflecting mirror increases. This is because the convergent light beam L2 emitted from the concave reflecting mirror 36 is emitted from a position shifted from the optical axis O36 of the concave reflecting mirror 36, and therefore the rightmost light of the light beam emitted from the concave reflecting mirror 36 in FIG. This is because the light having the smallest incident angle and the light on the leftmost side has an inclination that gives the largest emission angle (the incident angle is an angle between the incident light and the normal line of the concave reflecting mirror surface). As described above, since the light emission angle with respect to the concave reflecting mirror is different in the plane (has an inclination), a slight difference occurs in the rotation of the polarization plane in the plane, resulting in uneven extinction ratio in crossed Nicols.

  When a change in polarization due to structural birefringence is detected by the two polarizing plates 34 and 38 arranged in crossed Nicols as in the present embodiment, such slight polarization disturbance due to the device is noise. As a result, the detection accuracy is degraded.

  In order to eliminate such uneven rotation of the polarization plane in the plane of the illumination light due to the rotation of the minute polarization plane distributed with an inclination, in this embodiment, the polarizing plate 34 or the polarizing plate 38 is provided. It was set as the structure which moves a cross Nicol area | region by rotating.

  FIG. 6 is a diagram showing a configuration of a support member for the polarizing plate 34 or 38. The polarizing plate 34 or 38 is fixed by annular support members 40 and 42. The support members 40 and 42 are overlapped with each other, and an annular rotary element member 41 is provided at the coupling portion, and the support members 40 and 42 are joined via the rotary element member 41. The polarizing plate 34 or 38 is fixed to the support member 40, and the support member 40 can rotate with respect to the support member 42 along the rotation element member 41. The gear 44 attached to the rotating shaft 43 a of the motor 43 is installed so as to mesh with the gear teeth provided on the outer peripheral portion of the support member 40. When the gear 43 is rotated by driving the motor 43, the support member 40 is also rotated accordingly. With such a configuration, the polarizing plate 34 or 38 can be rotated by driving and controlling the motor 43. The amount of rotation can be monitored by an encoder or the like, and can be set to a desired amount of rotation. Such a structure for rotating the polarizing plate may be provided in at least one of the polarizing plate 34 and the polarizing plate 38, but may be provided in both polarizing plates.

  By rotating the polarizing plate 34 or 38 and moving the crossed Nicols region of the two polarizing plates, a change occurs in the rotation position of the polarization plane as described above, and the position where the extinction ratio unevenness also changes. To do. In the present embodiment, the polarizing plate 34 or 38 is rotated to acquire an image a plurality of times in a state where the unevenness of the extinction ratio is changed, and by combining them, an image with reduced unevenness is obtained.

  FIG. 7 is a diagram showing the variation in the extinction ratio unevenness caused by rotating the polarizing plate 34 or 38. In FIG. 7A, a bare wafer (a wafer whose surface is not subjected to any processing) is placed on the stage 11 in a state where the polarizing plate 34 and the polarizing plate 38 are arranged in a crossed Nicols relationship. In this case, an image captured by the image sensor 39 is shown. Since this bare wafer has no pattern formed on its surface, the linearly polarized light L1 does not generate an elliptically polarized component even if it is irradiated onto the bare wafer. Therefore, theoretically, a light beam having the same polarization direction as that of the linearly polarized light L1 is incident on the polarizing plate 38, there is no polarization component transmitted through the polarizing plate 38, and no light is incident on the image pickup device 39. Become. However, as described above, when the plane of polarization is rotated by the concave reflecting mirrors 35 and 36, the polarized light component of the portion where the plane of polarization is rotated is incident on the image sensor 39, and the portion looks bright. . In FIG. 7A, there are a black belt-like region 51a and regions 51b and 51c that appear brighter than the region 51a. The regions 51b and 51c are portions where the polarization plane is rotated. In this way, the brightness is uneven (extinction ratio is uneven).

  FIG. 7B shows an image captured by the image sensor 39 when the polarizing plate 34 (or the polarizing plate 38) is rotated by an angle θ1 in one direction. Compared with FIG. 7A, the position of the black belt-like region 51a is moved by rotating the polarizing plate 34 (or the polarizing plate 38). At this time, an angle θ1 at which the black belt-like region 51a moves may be searched for in the region 51c in FIG. The state shown in FIG. 7B is that state.

  FIG. 7C shows an image picked up by the image pickup device 39 when the polarizing plate 34 (or the polarizing plate 38) is rotated by θ2 in the direction opposite to the case of FIG. 7B. Yes. Compared with FIG. 7A, by rotating the polarizing plate 34 or the polarizing plate 38, the position of the black belt-like region 51a moves in the direction opposite to that in FIG. 7B. At this time, an angle θ2 at which the black band-like region 51a moves may be searched for in the region 51b in FIG. The state shown in FIG. 7C is that state.

By synthesizing the three images obtained as described above, an image in which the black belt-like regions 51a are distributed over the entire surface can be obtained. Therefore, as shown in FIG. 7D, an image with reduced non-uniform extinction ratio can be obtained.
The image processing device 15 stores the angles θ1 and θ2 obtained as described above. When inspecting the wafer 20 to be inspected, first, as in FIG. 7A, an image is obtained by imaging in a state where the polarizing plate 34 and the polarizing plate 38 are arranged in a crossed Nicols relationship. Next, as in FIG. 7B, an image is obtained by capturing an image with the polarizing plate 34 (or the polarizing plate 38) rotated by an angle θ1. Next, as in FIG. 7C, the polarizing plate 34 (or the polarizing plate 38) is imaged by rotating the polarizing plate 34 (or the polarizing plate 38) in the direction opposite to that in the case of FIG. Then, by synthesizing the three obtained images, an image with reduced unevenness in the extinction ratio is obtained.

  As described above, according to the present embodiment, the concave reflecting mirrors 35 and 36 are obtained by rotating the polarizing plate 34 (or the polarizing plate 38), imaging the wafer 20 a plurality of times, and synthesizing those images. It is possible to correct unevenness in image brightness due to the inclination of the rotation amount of the polarization plane in the cross-sectional direction of the light beam. Therefore, the detection accuracy of defect detection on the wafer is not deteriorated.

  Next, a surface inspection apparatus according to another embodiment of the present invention will be described. The configuration of the surface inspection apparatus of the present embodiment is the same as that of FIG. 1, but the polarizing plate 34 or the polarizing plate 38 does not have a support member for rotation as in the above-described embodiment, and the polarizing plate 34 and the polarizing plate The plate 38 is fixed in a state of being arranged in a crossed Nicols relationship. The stage 11 is configured to be able to move the wafer 20 in a direction parallel to the surface of the wafer 20. This is an XY stage movable in a so-called XY direction, and can be realized by a known stage.

FIG. 8 is a diagram showing the relationship between the wafer 20 surface and the extinction ratio unevenness when the stage 11 is moved and the wafer 20 is moved in a direction parallel to the surface of the wafer 20.
FIG. 8A shows an image picked up by the image pickup device 39 when the bare wafer is placed on the stage 11 with the center of the illumination area by the illumination optical system 13 and the center of the stage 11 substantially matched. Is shown. This state is the same as that in FIG. For the same reason as in FIG. 7A, there are a black belt-like region 51a and regions 51b and 51c that appear brighter than the region 51a. The regions 51b and 51c are portions where the polarization plane is rotated. In this way, the brightness is uneven (extinction ratio is uneven).

  FIG. 8B shows a state in which the image of the wafer is moved in the lower right direction by moving the stage 11. Since the illumination optical system 13 and the light receiving optical system 14 are fixed, the position of the black belt-like region 51a does not change. Since the wafer has moved, the positional relationship between the wafer surface and the black belt-like region 51a changes, and the black belt-like region 51a comes to the region 51b in FIG. 8A on the wafer.

  FIG. 8C shows a state in which the image of the wafer is moved in the upper left direction by moving the stage 11 in the direction opposite to that in the case of FIG. 7B. Since the illumination optical system 13 and the light receiving optical system 14 are fixed, the position of the black belt-like region 51a does not change. Since the wafer has moved, the positional relationship between the wafer surface and the black belt-like region 51a changes, and the black belt-like region 51a comes to the region 51c in FIG. 8A on the wafer.

By synthesizing the three images obtained as described above, an image in which the black belt-like regions 51a are distributed over the entire surface can be obtained. Therefore, as shown in FIG. 8D, an image with reduced non-uniform extinction ratio can be obtained.
The image processing apparatus 15 stores the amount of movement of the stage as shown in FIGS. 8B and 8C. When inspecting the wafer 20 to be inspected, first, an image is obtained by imaging at the same position of the stage 11 as in FIG. Next, the stage 11 is moved, and an image is obtained by taking an image at the same position as in FIG. Next, the stage 11 is moved, and an image is obtained by taking an image at the same position as in FIG. Then, by synthesizing the three obtained images, an image with reduced unevenness in the extinction ratio is obtained.

  As described above, according to this embodiment, the stage 11 is moved, the wafer 20 is imaged a plurality of times, and these images are combined, whereby the polarization in the cross-sectional direction of the light flux by the concave reflecting mirrors 35 and 36 is performed. It is possible to correct unevenness in the brightness of the image due to the inclination of the rotation amount of the surface. Therefore, the detection accuracy of defect detection on the wafer is not deteriorated.

  In the above embodiment, as shown in FIGS. 7 and 8, the images obtained by three times of imaging are combined. However, the number of times of imaging is determined by the size of the black belt-like region 51 a. You can decide by. When the black belt-like region 51a is large, an image obtained by two times of imaging may be synthesized. When the black belt-like region 51a is small, an image obtained by four or more times of imaging may be synthesized.

It is a figure which shows the whole structure of the surface inspection apparatus by embodiment of this invention. 2 is an external view of the surface of a semiconductor wafer 20. FIG. It is a figure explaining the inclination state of the incident surface (3A) of the linearly polarized light L1 and the repeating direction (X direction) of the repeating pattern 22. FIG. It is a figure explaining the vibration direction of linearly polarized light L1 and elliptically polarized light L2. It is a figure explaining the inclination state of the direction (V direction) of the vibration surface of the linearly polarized light L1, and the repeating direction (X direction) of the repeating pattern 22. FIG. It is a figure which shows the structure of the supporting member of the polarizing plate 34 or 38. FIG. It is a figure which shows the change of the nonuniformity of an extinction ratio by rotating the polarizing plate 34 or 38. FIG. It is a figure which shows the relationship between the wafer 20 surface and the nonuniformity of an extinction ratio when the stage 20 is moved and the wafer 20 is moved.

Explanation of symbols

11: Stage, 12: Alignment system, 13: Illumination optical system, 14: Light receiving optical system, 15: Image processing device, 16: Stage rotation mechanism, 20: Semiconductor wafer, 21: Chip area, 22, 25, 26: Repetition Pattern, 33: light guide fiber, 34, 38: polarizing plate, 35, 36: concave reflecting mirror, 37: imaging lens, 39: imaging element, 40, 42: support member, 41: rotating element member, 43: motor 44: gear, L1: illumination light, L2: reflected light, LS: lamp house.

Claims (3)

Light source means for emitting a divergent light beam for illuminating the substrate to be inspected;
An irradiating member that guides the divergent light beam so that a principal ray of the light beam has a predetermined incident angle and guides it to the test substrate;
Imaging means for condensing light from the test substrate and forming an image of the test substrate; Imaging means for capturing the image formed;
A first polarizing plate provided in an optical path from the light source means to the irradiation member;
A second polarizing plate provided in an optical path from the imaging means to the imaging means;
Rotating means for rotating at least one of the first polarizing plate and the second polarizing plate in a plane perpendicular to the optical axis;
A surface inspection apparatus comprising: detection means for detecting defects on the surface of the substrate to be inspected based on images obtained by the imaging means at a plurality of rotation positions by the rotation means. The surface inspection apparatus according to claim 1,
The surface inspection apparatus characterized in that the rotating means can be rotated to a position where the first polarizing plate and the second polarizing plate are in a crossed Nicols state. Light source means for emitting a divergent light beam for illuminating the substrate to be inspected;
An irradiating member that guides the divergent light beam so that a principal ray of the light beam has a predetermined incident angle and guides it to the test substrate;
Imaging means for condensing light from the test substrate and forming an image of the test substrate; Imaging means for capturing the image formed;
A first polarizing plate provided in an optical path from the light source means to the irradiation member;
A second polarizing plate provided in an optical path from the imaging means to the imaging means and arranged to be in a crossed Nicols state with the first polarizing plate;
Moving means for moving the test substrate relative to a region illuminated by the irradiation member in a direction parallel to the surface of the test substrate;
A surface inspection apparatus comprising: detection means for detecting defects on the surface of the substrate to be inspected based on images obtained by the imaging means at a plurality of movement positions by the movement means.

Images