JP2009145307A - Surface inspection apparatus and surface inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface inspection apparatus which enables the surface inspection of high sensitivity. <P>SOLUTION: The surface inspection apparatus 1 is equipped with: an illumination system 30 for irradiating the surface of a wafer 10, which has a predetermined repeated pattern, with first linear polarized light L1; an analyzer 42 for extracting second linear polarized light component L3, which is different from the first linear polarized light L1 in vibration direction, from the oval polarized light L2 produced on the surface of the wafer 10; an imaging camera 44 for detecting a second linear polarized light component L3; a monitor 55 for displaying the shape change of the repeated pattern on the basis of the second linear polarized light component L3 detected by the imaging camera 44; and a rotary drive device 43 for setting the analyzer 42 so that the advance direction of the oval polarized light L2, the direction of an oval short axis within a vertical plane and the vibration direction of the second polarized light component L3 within the vertical plane almost coincide with each other. The analyzer 42 is set according to the repeated pattern. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface inspection apparatus and method for inspecting the surface of a semiconductor wafer, a liquid crystal substrate or the like.

  As a method for judging the quality of a pattern formed on the surface of a semiconductor wafer, various methods for measuring a cross-sectional shape by observation with a scanning electron microscope (SEM) have been proposed. Cross-sectional shape measurement by SEM scans the electron beam irradiated to the pattern on the test substrate in the cross-sectional direction of the pattern, detects and analyzes the reflected electrons and secondary electrons from the pattern, and cross-sectional shape of the scanned part It is done by the method to ask for. The above operation is performed at several points on the pattern, and the quality of the entire pattern is judged.

  It is also determined whether there is a problem in the exposure process or etching process in which the pattern is formed from the cross-sectional shape of the pattern, and whether appropriate process conditions are selected. For example, for the exposure process, a correlation between the exposure condition and the cross-sectional shape of the pattern is obtained in advance, and whether or not the exposure condition of the exposure apparatus can be corrected is determined from the cross-sectional shape of the inspected pattern. Appropriate exposure conditions are obtained based on the correlation. In the etching process, the correlation between the gas type, gas pressure, acceleration voltage, and other conditions and the cross-sectional shape of the pattern is obtained in advance, and the same conditions are determined.

  As described above, the measurement method using the SEM repeatedly performs the operation of irradiating and scanning the pattern with an electron beam many times, and therefore it takes an enormous time to obtain the pattern shape. Further, since the observation magnification is high, it is difficult to obtain all pattern shapes on the wafer, and the quality of the entire wafer is judged by sampling several points. As a result, even if there is a defect in a portion other than the sampled pattern, it is overlooked. In the resist pattern, when the electron beam is irradiated, the electron beam is absorbed and charged by the resist by the acceleration voltage, and the pattern is lost. In some cases, discharge occurs and the pattern collapses, resulting in inconvenience in subsequent processes. Therefore, optimum observation conditions are also obtained while changing the acceleration voltage and the observation magnification in various ways. Therefore, more time is required for measurement.

  In the measurement of the cross-sectional shape by the SEM, there arises a problem that the failure of the exposure apparatus or the etcher cannot be sufficiently grasped due to such oversight. In addition, since enormous amounts of time are required for measurement, there is a problem in that defects in the exposure apparatus and etcher obtained from the measurement results cannot be quickly reflected in those apparatuses.

In order to solve such a problem, a surface inspection apparatus and a surface inspection method have been devised that can determine whether a pattern shape on a substrate to be tested is good or not in a short time regardless of a resist pattern or a pattern after etching. (For example, see Patent Document 1). This surface inspection apparatus illuminates by setting the vibration direction of linearly polarized light obliquely with respect to the repeating direction of the resist pattern having periodicity formed on the test substrate, and among the regular reflection light from the test substrate, By picking up an image using the image forming means to extract a polarization component having a vibration plane perpendicular to the vibration plane of the linearly polarized light to be illuminated, the quality of the pattern shape on the test substrate can be processed in a short time. .
JP 2006-135211 A

  However, when the line width is 50 nm or less, the resist thickness is also reduced, and the change in the polarization state caused by the structural birefringence of the resist pattern having periodicity formed on the test substrate is reduced. For this reason, out of the specularly reflected light from the test substrate when the direction of vibration of the linearly polarized light is set obliquely with respect to the repeating direction of the resist pattern, the vibration surface perpendicular to the surface of the linearly polarized light to be illuminated is selected. Since the polarization component it has also attenuated, there was a problem that the detection sensitivity to the pattern shape change was lowered.

  The present invention has been made in view of such problems, and an object thereof is to provide a surface inspection apparatus and a surface inspection method capable of highly sensitive surface inspection.

  In order to achieve such an object, a surface inspection apparatus according to the present invention irradiates a surface of a test substrate having a predetermined repetitive pattern with a lighting unit that irradiates the surface of the test substrate with a first linearly polarized light. In addition, when the first linearly polarized light is reflected by the repetitive pattern, a second linearly polarized light component having a vibration direction different from that of the first linearly polarized light is extracted from elliptically polarized light generated by the structural birefringence of the pattern. A polarization element; a detection unit that detects the second linearly polarized light component; a display unit that displays a shape change of the repetitive pattern based on the second linearly polarized light component detected by the detection unit; A setting unit capable of setting the polarizing element such that the direction of the minor axis of the ellipse in a plane perpendicular to the traveling direction of the elliptically polarized light and the vibration direction of the second linearly polarized light component in the perpendicular plane substantially coincide with each other; The For example, so as to set the polarization element according to the repeating pattern.

  In the surface inspection apparatus described above, the setting unit includes a vibration direction of the second linearly polarized light component in a plane perpendicular to the traveling direction of the elliptically polarized light and a traveling direction of the first linearly polarized light. An angle formed by an in-plane vibration direction can be changed by a predetermined angle, and based on the luminance of the second linearly polarized light component detected by the detection unit every time the angle is changed by the predetermined angle, It is preferable to select and set the angle at which the direction of the minor axis of the ellipse in the plane perpendicular to the traveling direction of the elliptically polarized light and the vibration direction of the second linearly polarized light component in the perpendicular plane substantially coincide.

  In the surface inspection apparatus described above, the abnormality detection unit further detects an abnormality of the repetitive pattern by comparing the luminance of the second linearly polarized light component detected by the detection unit with a preset threshold value. It is preferable to provide.

  In the surface inspection apparatus described above, it is preferable that the setting unit sets the polarizing element so that the second linearly polarized light component of the elliptically polarized light generated by the structural birefringence is most easily detected. .

  In the surface inspection apparatus described above, it is preferable that the setting unit performs the selection setting so that the angle is other than 90 degrees and an angle in the vicinity of 90 degrees.

  The surface inspection method according to the present invention includes an irradiation step of irradiating the surface of the test substrate having a predetermined repetitive pattern with the first linearly polarized light, and the first straight line irradiated on the surface of the test substrate. An extraction step of extracting a second linearly polarized light component having a vibration direction different from that of the first linearly polarized light from elliptically polarized light generated by the structural birefringence of the pattern when the polarized light is reflected by the repetitive pattern; A detection step for detecting two linearly polarized light components, a display step for displaying a shape change of the repetitive pattern based on the second linearly polarized light component detected in the detecting step, and a traveling direction of the elliptically polarized light, A setting step of setting a vibration direction of the extracted second linearly polarized light component in a vertical plane according to the repetitive pattern.

  In the setting step, a vibration direction of the second linearly polarized light component in a plane perpendicular to the traveling direction of the elliptically polarized light, and a vibration direction in a plane perpendicular to the traveling direction of the first linearly polarized light. An elliptical short axis in a plane perpendicular to the traveling direction of the elliptically polarized light based on the brightness of the second linearly polarized light component detected each time the angle formed is changed by a predetermined angle and the angle is changed by the predetermined angle. It is preferable to select and set the angle at which the orientation of the second linearly polarized light component in the vertical plane substantially coincides with the vibration direction of the second linearly polarized light component.

  In the setting step, it is preferable that the selection setting is performed so that the angle is other than 90 degrees and an angle close to 90 degrees.

  According to the present invention, a highly sensitive surface inspection can be performed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the surface inspection apparatus 1 according to the present embodiment includes a stage 20 that supports a semiconductor wafer 10 (hereinafter, referred to as a wafer 10) that is a substrate to be tested, an alignment system 25, an illumination system 30, And a light receiving system 40. In addition, the surface inspection apparatus 1 includes an image processing unit 50 that performs image processing of an image captured by the light receiving system 40, and a monitor 55 that displays an image captured by the light receiving system 40 and an image processing result by the image processing unit 50. It has. The surface inspection apparatus 1 is an apparatus that automatically inspects the surface of a wafer 10 in a manufacturing process of a semiconductor circuit element. After exposure / development of the uppermost resist film, the wafer 10 is carried from a wafer cassette (not shown) or a developing device by a conveyance system (not shown), and is sucked and held on the stage 20.

  As shown in FIG. 2, a plurality of chip regions 11 are arranged in the XY direction on the surface of the wafer 10, and a predetermined repetitive pattern 12 is formed in each chip region. As shown in FIG. 3, the repetitive pattern 12 is a resist pattern (for example, a wiring pattern) in which a plurality of line portions 2A are arranged at a constant pitch P along the short direction (X direction). Between adjacent line parts 2A is a space part 2B. The arrangement direction (X direction) of the line portions 2A is referred to as “repeating direction of the repeating pattern 12”.

Here, the design value of the line width D _A of the line portion 2A in the repetitive pattern 12 is set to ½ of the pitch P. If repeated pattern 12 is formed as the design value, the line width D _B of the line width D _A and the space portion 2B of the line portion 2A are equal, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: 1 In contrast, when the exposure focus at the time of forming the repeating pattern 12 deviates from a proper value, the pitch P does not change, with the line width D _A of the line portion 2A becomes different from a design value, of the space portion 2B It becomes different even with the line width D _B, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: deviates from 1.

  The surface inspection apparatus 1 of the present embodiment performs defect inspection of the repetitive pattern 12 by using the change in the volume ratio between the line portion 2A and the space portion 2B in the repetitive pattern 12 as described above. In order to simplify the explanation, the ideal volume ratio (design value) is 1: 1. The change in the volume ratio is caused by the deviation of the exposure focus from the appropriate state, and appears for each shot area of the wafer 10. The volume ratio can also be referred to as the area ratio of the cross-sectional shape.

  In the present embodiment, it is assumed that the pitch P of the repeating pattern 12 is sufficiently small compared to the wavelength of illumination light (described later) for the repeating pattern 12. For this reason, diffracted light is not generated from the repetitive pattern 12, and the defect inspection of the repetitive pattern 12 cannot be performed by diffracted light. The principle of defect inspection in the present embodiment will be described in order along with the configuration of the surface inspection apparatus (FIG. 1).

  The stage 20 of the surface inspection apparatus 1 supports the wafer 10 on the upper surface and fixes and holds the wafer 10 by, for example, vacuum suction. Further, the stage 20 is rotatable about the normal A1 at the center of the upper surface as a central axis. By this rotation mechanism, the repeating direction of the repeating pattern 12 on the wafer 10 (the X direction in FIGS. 2 and 3) can be rotated within the surface of the wafer 10. The stage 20 has a horizontal upper surface, and can always keep the wafer 10 in a horizontal state.

  The alignment system 25 illuminates the outer edge of the wafer 10 while the stage 20 is rotating, detects the position in the rotation direction of an external reference (for example, a notch) provided on the outer edge, and the stage 20 at a predetermined position. Stop. As a result, the repetitive direction (X direction in FIGS. 2 and 3) of the repetitive pattern 12 on the wafer 10 is set to be inclined at an angle of 45 degrees with respect to an illumination light incident surface A2 (see FIG. 4) described later. can do. The angle is not limited to 45 degrees, and can be set in an arbitrary angle direction such as 22.5 degrees or 67.5 degrees.

  The illumination system 30 is a decentered optical system that includes a light source 31, a polarizer 32, and an illumination lens 33. The illumination system 30 converts the repetitive pattern 12 of the wafer 10 on the stage 20 into linearly polarized light L1 (first linear line L1). Illuminate with polarized light. This linearly polarized light L1 is illumination light for the repeated pattern 12. The linearly polarized light L1 is irradiated on the entire surface of the wafer 10.

  The traveling direction of the linearly polarized light L1 (the direction of the principal ray of the linearly polarized light L1 reaching an arbitrary point on the surface of the wafer 10) passes through the center of the stage 20 and is a predetermined angle θ with respect to the normal A1 of the stage 20. Tilted. Incidentally, a plane including the traveling direction of the linearly polarized light L1 and parallel to the normal A1 of the stage 20 is an incident surface of the linearly polarized light L1. An incident surface A <b> 2 in FIG. 4 is an incident surface at the center of the wafer 10.

  In the present embodiment, the linearly polarized light L1 is p-polarized light. The vibration plane of the linearly polarized light L <b> 1 is defined by the transmission axis of the polarizer 32.

  The light source 31 of the illumination system 30 is an inexpensive discharge light source or LED. The polarizer 32 is disposed in the vicinity of the emission end of the light source 31, and its transmission axis is set to a predetermined direction, and the light from the light source 31 is converted into linearly polarized light L1 according to the transmission axis. The illumination lens 33 is disposed so that it substantially coincides with the emission end of the light source 31 and the rear focal point substantially coincides with the surface of the wafer 10, and guides light from the polarizer 32 to the surface of the wafer 10. That is, the illumination system 30 is an optical system telecentric with respect to the wafer 10 side.

  In the illumination system 30, the light from the light source 31 becomes p-polarized linearly polarized light L <b> 1 through the polarizer 32 and the illumination lens 33 and enters the entire surface of the wafer 10. The incident angle of the linearly polarized light L1 at each point of the wafer 10 is the same because of the parallel light flux, and corresponds to the angle θ formed by the optical axis and the normal line A1.

  In this embodiment, since the linearly polarized light L1 incident on the wafer 10 is p-polarized light, as shown in FIG. 4, the repeating direction (X direction) of the repeated pattern 12 is the incident surface A2 of the linearly polarized light L1 (the surface of the wafer 10). Is set to an angle of 45 degrees with respect to the linearly polarized light L1 traveling direction), the direction of the vibrating surface of the linearly polarized light L1 on the surface of the wafer 10 (the V direction in FIG. 5) and the repeating direction of the repeating pattern 12 (X The angle formed by (direction) is also set to 45 degrees.

  In other words, the linearly polarized light L1 is repeated with the vibration plane direction (V direction in FIG. 5) of the linearly polarized light L1 on the surface of the wafer 10 inclined by 45 degrees with respect to the repeating direction (X direction) of the repeating pattern 12. The light repeatedly enters the pattern 12 so as to cross the pattern 12 diagonally.

  The angle state between the linearly polarized light L1 and the repeated pattern 12 is uniform over the entire surface of the wafer 10. Note that the angle state between the linearly polarized light L1 and the repetitive pattern 12 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 direction of the vibration surface (V direction) and the repeat direction (X direction) in FIG. 5 is set to 45 degrees is to maximize the change in the polarization state due to the repeat pattern 12.

  When the repeating pattern 12 is illuminated using the linearly polarized light L1, elliptically polarized light L2 is generated from the repeating pattern 12 in the regular reflection direction. 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 A2 of the linearly polarized light L1 and is inclined with respect to the normal A1 of the stage 20 by an angle θ (an angle equal to the incident angle θ of the linearly polarized light L1). As described above, since the pitch P of the repeated pattern 12 is sufficiently shorter than the illumination wavelength, no diffracted light is generated from the repeated pattern 12.

  As shown in FIG. 1, the light receiving system 40 includes a light receiving lens 41, an analyzer 42, a rotation drive device 43, and an imaging camera 44, and the optical axis thereof is the center of the stage 20. And is arranged so as to be inclined by an angle θ with respect to the normal line A1 of the stage 20. The light receiving lens 41 condenses the elliptically polarized light L <b> 2 on the imaging surface of the imaging camera 44.

  The analyzer 42 is configured to be able to rotate the azimuth (polarization direction) of the transmission axis around the optical axis of the light receiving system 40 by using the rotation driving device 43. The azimuth of the transmission axis of the analyzer 42 is described above. It is set to be inclined at an inclination angle of about 90 degrees with respect to the transmission axis of the polarizer 32. That is, the crossed Nicols state can be intentionally broken. Therefore, when the elliptically polarized light L2 passes through the analyzer 42, its polarization component, that is, the linearly polarized light L3 (second linearly polarized light) from the analyzer 42 is condensed on the imaging surface of the imaging camera 44. As a result, a reflected image of the wafer 10 by the linearly polarized light L3 is formed on the imaging surface of the imaging camera 44.

  The imaging camera 44 is a CCD camera having a CCD imaging device (not shown), photoelectrically converts the reflected image of the wafer 10 formed on the imaging surface, and outputs an image signal to the image processing unit 50. The brightness of the reflected image of the wafer 10 is substantially proportional to the light intensity of the linearly polarized light L3 and changes according to the shape of the repeated pattern 12. The reflected image of the wafer 10 is brightest when the repeated pattern 12 has an ideal shape. The brightness of the reflected image of the wafer 10 appears for each shot area.

  When the reflection image of the wafer 10 as the test substrate is input, the image processing unit 50 compares the luminance information with the luminance information of the reflection image of the non-defective wafer stored in advance. At this time, the defect of the repetitive pattern 12 is detected based on the amount of decrease in luminance value (luminance change) in a dark portion in the reflected image of the wafer 10. For example, “defect (abnormal)” may be determined if the amount of decrease in luminance value is greater than a predetermined threshold (allowable value), and “normal” may be determined if it is less than the threshold. Then, the comparison result of the luminance information by the image processing unit 50 and the reflected image of the wafer 10 at that time are output and displayed on the monitor 55. In addition, the reflection image of the wafer 10 captured by the imaging camera 44 without using the image processing unit 50 may be displayed on the monitor 55, and the shape change of the repeated pattern on the wafer 10 may be confirmed visually. Further, the screen of the monitor 55 may be divided to display both a defect (abnormality) display and a reflected image of the wafer 10.

  As described above, the image processing unit 50 has a configuration in which the reflection image of the non-defective wafer is stored in advance and the array data of the shot area of the wafer 10 and the threshold value of the brightness value are stored in advance. Good. In this case, since the position of each shot area in the reflected image of the captured wafer 10 is known based on the array data of the shot area, the luminance value of each shot area is obtained. Then, a pattern defect is detected by comparing the brightness value with a stored threshold value. A shot area having a luminance value smaller than the threshold value may be determined as “defect (abnormal)”.

  As described above, the analyzer 42 is configured to be able to rotate the azimuth (polarization direction) of the transmission axis around the optical axis of the light receiving system 40 using the rotation driving device 43, and the transmission axis of the analyzer 42 is By rotating the analyzer 42 so as to be tilted by an inclination angle slightly deviated from 90 degrees with respect to the transmission axis of the polarizer 32 (that is, to slightly break the crossed Nicols state), the shape of the repeated pattern 12 can be changed. Detection sensitivity can be improved.

  Next, the reason will be described. FIG. 6 shows a state in which the incident linearly polarized light L1 is changed to the elliptically polarized light L2 due to the structural birefringence of the repetitive pattern 12. As shown in FIG. 6, the elliptically polarized light L2 does not necessarily have the azimuth angle of the major axis coincident with the angle of the linearly polarized light L1 (incident surface A2), and is inclined according to the shape of the repetitive pattern 12, the ground structure, etc. It becomes elliptically polarized light. The amount of inclination is actually only a few degrees, but is exaggerated in FIG.

  FIG. 7 is a diagram comparing a change in polarization state depending on a pattern between a non-defective shot and a defective shot. The long elliptical polarized light L2A with the short axis shows the elliptically polarized state changed by the non-defective shot, and the short elliptical polarized light L2B with the short axis shows the elliptically polarized state changed by the defective shot. The short-axis short elliptically polarized light L2B has a poor pattern, so that the change in the polarization state is small and the elliptical polarized light is less thick (the length of the short axis). In order to determine whether the pattern is good or bad, it is effective to look at the difference in the thickness of the ellipse.

At this time, in order to obtain a completely crossed Nicol state, when the transmission axis 42a of the analyzer 42 is arranged vertically (in a direction orthogonal to the linearly polarized light L1), the light transmitted through the ellipse has a long short axis. Light having the amplitude of the vertical vibration component B1 is transmitted from the polarized light L2A, and light having the amplitude of the vertical vibration component B2 is transmitted from the short elliptical polarized light L2B having a short axis. Since the light quantity is the square of the amplitude, the light quantity ratio at this time is (B1) ² : (B2) ² . What should be noted here is that both B1 and B2 include not only the vibration component in the short axis direction generated according to the thickness of the ellipse but also the vibration component in the long axis direction generated by the inclination of the ellipse. And B2 are small and the light quantity ratio is close to 1: 1, and the detection sensitivity of the pattern shape change is low.

  FIG. 8 is a diagram for explaining light transmitted through the analyzer 42 when the direction of the transmission axis 42a of the analyzer 42 is substantially coincident with the direction of the short axis of elliptically polarized light (substantially orthogonal to the direction of the long axis). . In FIG. 8, since the direction of the transmission axis 42a of the analyzer 42 is substantially coincident with the direction of the short axis of the elliptically polarized light, the light having the amplitude of the vibration component C1 is reflected from the long axis of the elliptically polarized light L2A. The light having the amplitude of the vibration component C2 is transmitted from the short elliptically polarized light L2B. By tilting the analyzer 42 in this way, it is possible to detect only the vibration component corresponding to the change in the ellipse thickness without transmitting the long-axis direction vibration component generated by the inclination of the ellipse.

The light quantity ratio at this time is that C1 and C2 are about twice as long, so the value of (B1) ² : (B2) ² is about 4: 1 and the two elliptically polarized lights L2A and L2B are thicker. It can be seen that there is a large difference in condition, and a change in the shape of the pattern can be detected with higher sensitivity.

  As described above, in an optical system that detects a change in the shape of a pattern from a change in the polarization state due to the pattern, a perfect crossed Nicol system is not necessarily the best form, and the analyzer has a function depending on the inclination of elliptically polarized light. It is effective to slightly tilt the angle.

  Therefore, a surface inspection method using the surface inspection apparatus 1 of the present embodiment will be described with reference to the flowchart shown in FIG. First, a recipe creation operation is performed before the wafer surface inspection. This is because it is necessary to determine an inspection condition in order to perform an optimal inspection in the wafer surface inspection. Therefore, the exposure is performed under the condition that the focus amount and the dose amount of the exposure device are previously shaken (changed) for each shot, and the developed wafer is transferred to the stage 20 (step S101).

  Such a conditionally adjusted wafer 10f (see FIG. 10) is prepared so that there is a best shot (non-defective shot) with an optimum focus amount and dose amount as a reference. At this time, the wafer is not limited to the conditionally adjusted wafer 10f but may be a wafer having defects due to omission. Alignment is performed so that the repeating direction of the repeated pattern 12 is inclined by 45 degrees with respect to the illumination direction (the traveling direction of the linearly polarized light L1 on the surface of the wafer 10) after the condition-wafer 10f is conveyed. The alignment angle is not limited to 45 degrees, and may be 67.5 degrees or 22.5 degrees.

  After transporting and aligning the conditioned wafer 10f, the surface of the conditioned wafer 10f is irradiated with the first linearly polarized light L1, and the specularly reflected light (elliptical polarized light L2) reflected by the surface of the conditioned wafer 10f is analyzed. The image is detected and imaged by the imaging camera 44 via 42 (step S102). At this time, the light from the light source 31 becomes the linearly polarized light L1 through the polarizer 32 and the illumination lens 33, and is irradiated on the surface of the conditioned wafer 10f. Then, the specularly reflected light (elliptical polarized light L2) reflected by the surface of the conditioned wafer 10f is collected by the light receiving lens 41, converted into the second linearly polarized light L3 by the analyzer 42, and then on the imaging surface of the imaging camera 44. The image is formed, and the imaging camera 44 photoelectrically converts the reflected image of the condition-controlled wafer 10f by the second linearly polarized light L3 formed on the imaging surface to generate an image signal, and outputs the image signal to the image processing unit 50 To do.

  When the image signal of the conditionally adjusted wafer 10f by the second linearly polarized light L3 is input to the image processing unit 50, it is stored in an internal memory (not shown) of the image processing unit 50 (step S103).

  As described above, the analyzer 42 is configured to be able to rotate the azimuth (polarization direction) of the transmission axis using the rotation driving device 43, and the azimuth of the transmission axis of the analyzer 42 is set to the transmission axis of the polarizer 32. On the other hand, while rotating by 90 degrees from 90 degrees to 3 degrees (87 degrees) to an inclination angle of 90 degrees +3 degrees (93 degrees) (steps S104 to S105), the imaging in step S102 and the image storage in step S103 are performed. Repeatedly, at this time, the brightness of the reference shot (best quality shot) position is calculated from the captured image, and the amount of illumination light is adjusted each time so that the brightness is constant. As a result, 30 images with the same brightness value as the reference shot and different orientations of the transmission axes of the analyzer 42 are stored.

  When 30 images with different transmission axis orientations of the analyzer 42 are captured and acquired, the conditionally adjusted wafer 10f is recovered (steps S104 to S106). Then, the image processing unit 50 reads 30 images from the internal memory, and performs image processing on an image having the largest difference between the luminance of the reference shot and the luminance of the shot with the focus amount and the dose amount changed (changed). Obtained (step S107). This process maximizes the luminance change between a defective shot and a non-defective shot for detecting a focus failure (defocus) that occurs when the exposure machine or film thickness is abnormal (ie, the direction of the transmission axis is the same). The direction of the transmission axis of the analyzer 42 (substantially coincident with the direction of the short axis of the elliptically polarized light L2) can be obtained. In addition, regarding the defect of the dose, the direction of the transmission axis of the analyzer 42 in which the luminance change between the defective shot and the non-defective shot becomes the largest can be obtained, which is optimum when detecting the focus defect and the dose defect. Each condition is determined. In the case of the same condition, there is one condition. At this time, the orientation of the obtained transmission axis of the analyzer 42 is registered in the recipe together with the illumination light quantity at that time.

  After the recipe is created, the surface of the wafer 10 that is the test substrate is inspected (step S108). At this time, the first linearly polarized light L1 is irradiated on the surface of the wafer 10 according to the direction of the transmission axis of the analyzer 42 determined in the previous step and the amount of illumination light, and the specularly reflected light (elliptical polarized light) reflected on the surface of the wafer 10 is irradiated. L2) is detected by the imaging camera 44 via the analyzer 42 and imaged. Therefore, in the reflected image of the wafer 10 by the second linearly polarized light L3 imaged by the imaging camera 44, when there is a focus defect and a dose defect, the luminance change between the defective shot and the non-defective shot increases. Since the image processing unit 50 detects a defect in the repeated pattern 12 based on the luminance change, it is possible to inspect the repeated pattern 12 with high sensitivity.

  As a result, according to the surface inspection apparatus 1 and method of the present embodiment, the vibration direction (the direction of the transmission axis of the analyzer 42) in the plane perpendicular to the traveling direction of the second linearly polarized light L3 is the traveling of the elliptically polarized light L2. Since the setting is made so as to substantially coincide with the direction of the minor axis of the ellipse in a plane perpendicular to the direction, a highly sensitive surface inspection can be performed.

  Further, as described above, the second time based on the brightness of the second linearly polarized light L3 detected by the imaging camera 44 every time the tilt angle of the transmission axis of the analyzer 42 is changed by a predetermined angle (0.2 degrees). By simply setting and setting the inclination angle of the analyzer 42 in which the vibration direction of the linearly polarized light L3 (the direction of the transmission axis of the analyzer 42) substantially coincides with the direction of the elliptical short axis of the elliptically polarized light L2, Can perform highly sensitive surface inspection.

  At this time, by selecting and setting so that the inclination angle of the analyzer 42 is an angle in the vicinity of 90 degrees, it is possible in a relatively short period of time to reduce light that is regularly reflected without being affected by structural birefringence. The analyzer 42 can be set.

  Next, a modification of the surface inspection method using the surface inspection apparatus 1 of the present embodiment will be described with reference to the flowchart shown in FIG. First, a recipe creation operation is performed before the wafer surface inspection. This is because it is necessary to determine an inspection condition in order to perform an optimal inspection in the wafer surface inspection. Therefore, exposure is performed with the best shot (non-defective shot) based on the optimum focus amount and dose as a reference, and the developed non-defective wafer is transferred to the stage 20 (step S201). A non-defective wafer is prepared for each wafer manufacturing process. Then, after the non-defective wafer is transferred, alignment is performed such that the repeating direction of the repeating pattern 12 is inclined by 45 degrees with respect to the illumination direction (the traveling direction of the linearly polarized light L1 on the surface of the wafer 10). The alignment angle is not limited to 45 degrees, and may be 67.5 degrees or 22.5 degrees.

  After transporting and aligning the non-defective wafer, the first linearly polarized light L1 is irradiated on the surface of the non-defective wafer, and the specularly reflected light (elliptical polarized light L2) reflected by the surface of the non-defective wafer is imaged through the analyzer 42. The image is detected and imaged at 44 (step S202). At this time, the light from the light source 31 becomes linearly polarized light L1 through the polarizer 32 and the illumination lens 33, and is irradiated on the surface of the non-defective wafer. Then, the specularly reflected light (elliptical polarized light L2) reflected by the surface of the non-defective wafer is collected by the light receiving lens 41, converted into the second linearly polarized light L3 by the analyzer 42, and formed on the imaging surface of the imaging camera 44. Then, the imaging camera 44 photoelectrically converts the reflected image of the non-defective wafer formed by the second linearly polarized light L3 formed on the imaging surface to generate an image signal, and outputs the image signal to the image processing unit 50.

  When the image signal of the non-defective wafer by the second linearly polarized light L3 is input to the image processing unit 50, it is stored in an internal memory (not shown) of the image processing unit 50 (step S203).

  Similarly to the above-described embodiment, the orientation of the transmission axis of the analyzer 42 is inclined from 90 degrees to 3 degrees (87 degrees) to 90 degrees +3 degrees (93 degrees) with respect to the transmission axis of the polarizer 32. While rotating by 0.2 degrees to the angle (steps S204 to S205), the imaging in step S202 and the image storage in step S203 are repeated, and at this time, the luminance of the reference shot (best shot) position is calculated from the captured image. The amount of illumination light is adjusted every time so that the brightness is constant. As a result, 30 images with the same brightness value as the reference shot and different orientations of the transmission axes of the analyzer 42 are stored.

  When 30 images with different transmission axis orientations of the analyzer 42 are captured and acquired, the non-defective wafers are collected (steps S204 to S206). Then, the image processing unit 50 registers the orientation of the transmission axis of the thirty kinds of analyzers 42 and the amount of illumination light at that time in the recipe (step S207).

  After the recipe is created, the surface of the wafer 10 that is the test substrate is inspected (step S208). At this time, the first linearly polarized light L1 is irradiated on the surface of the wafer 10 and reflected by the surface of the wafer 10 according to the azimuth of the transmission axis of the 30 kinds of analyzers 42 registered in the previous step and the amount of illumination light, respectively. Light (elliptical polarization L2) is detected by the imaging camera 44 via the analyzer 42 and imaged. Then, the image processing unit 50 compares the images of the 30 wafers 10 captured by the imaging camera 44 with the images of 30 non-defective wafers captured under the same conditions, and when the luminance change is larger than a predetermined threshold value. It is determined that the repeated pattern 12 has a defect. As a result, in the 30 wafers 10 images picked up by rotating the analyzer 42 by 0.2 degrees, the luminance change between the defective shot and the non-defective shot is large when there is a focus defect and a dose defect. Therefore, it is possible to inspect the repetitive pattern 12 with high sensitivity.

  As a result, the surface inspection method (and apparatus) according to the modification can obtain the same effects as those of the above-described embodiment.

  In the above-described embodiment, the analyzer 42 is configured to be able to rotate the azimuth of the transmission axis around the optical axis of the light receiving system 40 using the rotation driving device 43, but is not limited thereto. . For example, as shown in FIG. 12, a ½λ plate 45 is disposed between the light receiving lens 41 and the analyzer 42, and the direction of the slow axis of the ½λ plate 45 is received using a rotary drive device 49. It may be rotated about the optical axis of the system 40. For example, the 1 / 2λ plate 45 is arranged so that the slow axis 45a is in the vertical direction in FIG. 13. When elliptically polarized light 46 is incident on such a 1 / 2λ plate 45, the light passing therethrough is the slow axis 45a. Is converted into elliptically polarized light 47 having a symmetrical shape. Utilizing this phenomenon, if the 1 / 2λ plate 45 is arranged in front of the analyzer 42 and the angle of the slow axis 45a is appropriately set, the orientation of the minor axis of the elliptically polarized light is changed to the transmission axis of the analyzer 42. Therefore, it is possible to obtain the same effect as the analyzer 42 is tilted. Further, since the elliptically polarized light can be rotated by an angle twice the rotation angle of the slow axis 45a, the rotation control can be performed at a higher speed than when the analyzer 42 is directly rotated.

  In this case, the major axis azimuth angle of the elliptically polarized light of the non-defective shot and the elliptically polarized light of the defective shot may not match. In this case, the intermediate angle between them and the direction of the transmission axis of the analyzer 42 are substantially orthogonal. It is considered that it is preferable to make it substantially coincide with the intermediate angle of the short axis azimuth, but more realistically, the angle of the analyzer 42 is actually changed little by little, and the measurement passes through the analyzer 42. It is preferable to find an angle at which the luminance change between the non-defective shot and the defective shot to be maximized is found and set to that angle.

  Moreover, in the surface inspection apparatus 1 of this embodiment, the pitch P of the repeating pattern 12 is not limited to the case where the pitch P of the repeating pattern 12 is sufficiently small compared to the illumination wavelength. The defect inspection of the repeated pattern 12 can be performed in the same manner, even when it is equal to or larger than the illumination wavelength. That is, the defect inspection can be surely performed regardless of the pitch P of the repeated pattern 12. This is because the ellipticalization of the linearly polarized light L1 by the repeating pattern 12 changes depending on the volume ratio between the line portion 2A and the space portion 2B of the repeating pattern 12.

  In the above-described embodiment, the reflection image of the wafer 10 captured by the imaging camera 44 is displayed on the monitor 55 without using the image processing unit 50, and the defect of the repeated pattern 12 on the wafer 10 is detected visually. You may do it. Even if it does in this way, the effect similar to the above-mentioned embodiment can be acquired.

  In the above-described embodiment, the example in which the linearly polarized light L1 is p-polarized light has been described. However, the present invention is not limited to this. For example, s-polarized light instead of p-polarized light may be used. The s-polarized light is linearly polarized light having a component perpendicular to a virtual plane including both incident light and reflected light. For this reason, as shown in FIG. 4, when the repetitive direction (X direction) of the repetitive pattern 12 on the wafer 10 is set at an angle of 45 degrees with respect to the incident surface A2 of the linearly polarized light L1 that is s-polarized light, The angle formed by the direction of the vibrating surface of the s-polarized light on the surface 10 and the repeating direction (X direction) of the repeating pattern 12 is also set to 45 degrees. The p-polarized light is advantageous for acquiring defect information related to the edge shape of the line portion 2A of the repeated pattern 12. Further, the s-polarized light is advantageous for efficiently capturing defect information on the surface of the wafer 10 and improving the SN ratio.

  Furthermore, not only p-polarized light and s-polarized light, but also linearly polarized light whose vibration surface has an arbitrary inclination with respect to the incident surface may be used. In this case, the repetitive direction (X direction) of the repetitive pattern 12 is set to an angle other than 45 degrees with respect to the incident surface of the linearly polarized light L1, and the direction of the vibration surface of the linearly polarized light L1 on the surface of the wafer 10 and the repetitive pattern 12 It is preferable to set the angle formed by the repeat direction (X direction) to 45 degrees.

  In the above embodiment, the light source 31 and the polarizer 32 are used to generate the linearly polarized light L1. However, the present invention is not limited to this. If a linearly polarized laser is used as the light source, the light is polarized. The child 32 is not necessary.

It is a figure showing the whole surface inspection device composition concerning the present invention. It is an external view of the surface of a semiconductor wafer. It is a perspective view explaining the uneven structure of a repeating pattern. It is a figure explaining the inclination state of the entrance plane of a linearly polarized light and the repeating direction of a repeating pattern. It is a figure explaining the inclination state of the direction of the vibration surface of linearly polarized light, and the repeating direction of a repeating pattern. It is a figure which shows the state which the incident linearly polarized light changed to the elliptically polarized light by the structural birefringence of the pattern. It is the figure which compared the change of the polarization state by a pattern with a non-defective shot and a defective shot. It is a figure explaining the light which permeate | transmits an analyzer when the direction of the transmission axis of an analyzer is made to correspond substantially with the direction of the short axis of elliptically polarized light. It is a flowchart which shows the surface inspection method which concerns on this invention. It is a schematic diagram which shows a condition swing wafer. It is a flowchart which shows the modification of a surface inspection method. It is a figure which shows the modification of a surface inspection apparatus. It is a schematic diagram which shows a 1/2 (lambda) board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface inspection apparatus 10 Wafer (board to be tested) 12 Repeat pattern 30 Illumination system (illumination part)
40 Light receiving system 42 Analyzer (polarizing element)
43 Rotation Drive Device (Setting Unit) 44 Imaging Camera (Detection Unit)
45 1 / 2λ plate (modified example of setting unit) 49 Rotation drive device (modified example of setting unit)
50 Image processing unit (abnormality detection unit) 55 Monitor (display unit)
L1 First linearly polarized light L2 Elliptical polarized light L3 Second linearly polarized light

Claims (8)

An illumination unit that irradiates the surface of the test substrate having a predetermined repeating pattern with the first linearly polarized light;
The vibration direction of the first linearly polarized light is different from the elliptically polarized light generated by the structural birefringence of the pattern when the first linearly polarized light irradiated on the surface of the test substrate is reflected by the repetitive pattern. A polarizing element for extracting a second linearly polarized light component;
A detector for detecting the second linearly polarized light component;
A display unit that displays a shape change of the repetitive pattern based on the second linearly polarized light component detected by the detection unit;
A setting unit capable of setting the polarizing element such that the direction of the minor axis of the ellipse in a plane perpendicular to the traveling direction of the elliptically polarized light and the vibration direction of the second linearly polarized light component in the perpendicular plane substantially coincide with each other. And
A surface inspection apparatus, wherein the polarizing element is set according to the repetitive pattern. The setting unit includes an angle formed by a vibration direction of the second linearly polarized light component in a plane perpendicular to the traveling direction of the elliptically polarized light and a vibration direction in a plane perpendicular to the traveling direction of the first linearly polarized light. Can be changed by a predetermined angle,
Based on the luminance of the second linearly polarized light component detected by the detection unit every time the angle is changed by the predetermined angle, the direction of the elliptical short axis in the plane perpendicular to the traveling direction of the elliptically polarized light and the vertical The surface inspection apparatus according to claim 1, wherein the angle at which the vibration direction of the second linearly polarized light component substantially coincides with the vibration direction is selected and set.   2. The apparatus according to claim 1, further comprising: an abnormality detecting unit that detects an abnormality of the repetitive pattern by comparing the brightness of the second linearly polarized light component detected by the detecting unit with a preset threshold value. Or the surface inspection apparatus of Claim 2.   The said setting part sets the said polarizing element so that the said 2nd linearly polarized light component of the said elliptically polarized light produced by the said structural birefringence may be detected most easily. The surface inspection apparatus as described in any one of these.   The surface setting apparatus according to claim 2, wherein the setting unit performs the selection setting so that the angle is other than 90 degrees and an angle close to 90 degrees. An irradiation step of irradiating the surface of the test substrate having a predetermined repeating pattern with the first linearly polarized light;
The vibration direction of the first linearly polarized light is different from the elliptically polarized light generated by the structural birefringence of the pattern when the first linearly polarized light irradiated on the surface of the test substrate is reflected by the repetitive pattern. An extraction step of extracting a second linearly polarized component;
A detecting step for detecting the second linearly polarized light component;
A display step for displaying a change in shape of the repetitive pattern based on the second linearly polarized light component detected in the detection step;
A surface inspection method comprising: setting a vibration direction of the extracted second linearly polarized light component in a plane perpendicular to the traveling direction of the elliptically polarized light according to the repetitive pattern. In the setting step, an angle formed by a vibration direction of the second linearly polarized light component in a plane perpendicular to the traveling direction of the elliptically polarized light and a vibration direction in a plane perpendicular to the traveling direction of the first linearly polarized light. Is changed by a predetermined angle,
Based on the brightness of the second linearly polarized light component detected each time the angle is changed by the predetermined angle, the direction of the minor axis of the ellipse in the plane perpendicular to the traveling direction of the elliptically polarized light and the perpendicular plane The surface inspection method according to claim 6, wherein the angle at which the vibration direction of the second linearly polarized light component substantially matches is selectively set.   8. The surface inspection method according to claim 7, wherein in the setting step, the selection setting is performed so that the angle is other than 90 degrees and is an angle close to 90 degrees.

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