JP2008051666A - Flaw inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a flaw inspection device which can stably carry out inspection of the flaws of a semiconductor wafer, a liquid crystal panel, etc. without being affected by the film thickness variations by preventing changes in the signal of a flaw detector even when the thickness of a transparent thin film formed on a surface is changed. <P>SOLUTION: The flaw inspection device includes a first illumination optical system for irradiating an inspection object with a light at a predetermined irradiation angle, and a second illumination optical system for further reflecting the reflected light from the inspection object irradiated with the light from the first illumination optical system, and to irradiate the same irradiation position as that of the inspection object irradiated, by using the light of the first illumination optical system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention detects and analyzes defects such as foreign matter generated in a manufacturing process in which a pattern is formed on a substrate, such as a semiconductor manufacturing process, a liquid crystal display element manufacturing process, and a printed circuit board manufacturing process. The present invention relates to a defect inspection apparatus for inspecting the occurrence of defects such as foreign matters in a manufacturing process for which countermeasures are taken.

  In a semiconductor manufacturing process, if foreign matter is present on a semiconductor substrate (wafer), it may cause defects such as wiring insulation failure or short circuit. Further, when fine foreign matter is present with the miniaturization of the semiconductor element, the finer foreign matter may cause defective insulation of the capacitor or damage to the gate oxide film. These foreign substances are mixed in various states, such as those generated from the moving parts of the transfer device, those generated from the human body, those generated by reaction in the processing apparatus by the process gas, and those containing chemicals and materials. Is done.

  Similarly, in the manufacturing process of the liquid crystal display element, if foreign matter on the pattern is mixed in or some kind of defect occurs, the liquid crystal display element cannot be used as a display element. The situation is the same in the manufacturing process of the printed circuit board, and the inclusion of foreign matter causes a short circuit of the pattern and a defective connection.

  Conventionally, as one of the techniques for detecting foreign matters on a semiconductor substrate of this type, as described in Patent Document 1, a laser is irradiated on a semiconductor substrate and the foreign matter adheres on the semiconductor substrate. By detecting the scattered light from the generated foreign material and comparing it with the inspection result of the same type semiconductor substrate that was inspected immediately before, it eliminates false information due to the pattern and enables highly sensitive and highly reliable inspection of foreign materials and defects Is disclosed. Further, as disclosed in Patent Document 2, the semiconductor substrate is irradiated with a laser to detect scattered light from the foreign matter generated when the foreign matter adheres to the semiconductor substrate, and the detected foreign matter is detected. Some are analyzed by an analysis technique such as laser photoluminescence or two-dimensional X-ray analysis (XMR).

  In addition, as a technique for inspecting the foreign matter, there is a method of irradiating the wafer with coherent light and removing light emitted from the repeated pattern on the wafer with a spatial filter to emphasize and detect the foreign matter or defect having no repeatability. It is disclosed. Further, the circuit pattern formed on the wafer is irradiated from a direction inclined 45 degrees with respect to the main straight line group of the circuit pattern, and the 0th-order diffracted light from the main straight line group enters the aperture of the objective lens. A foreign substance inspection apparatus which is not allowed to be used is known in Patent Document 3. This Patent Document 3 also describes that other straight line groups that are not main straight line groups are shielded by a spatial filter. Further, Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 7, Patent Document 8, and Patent Document 9 are known as conventional techniques related to a defect inspection apparatus and method for foreign matters. In particular, Patent Document 9 describes that the detection pixel size is changed by switching the detection optical system. Patent Document 10 and Patent Document 11 are disclosed for measuring the size of foreign matter. In Patent Document 12, as a defect detection technique on a thin film, a laser beam is narrowed down, a long and narrow beam is formed in a direction perpendicular to the stage moving direction, and detection is performed in a direction perpendicular to the illumination direction. Patent Document 13 proposes a method of detecting from the same direction.

JP-A-62-89336 JP-A 63-135848 Japanese Patent Laid-Open No. 1-117024 JP-A-1-250847 JP-A-6-258239 JP-A-6-324003 JP-A-8-210989 JP-A-8-271437 JP 2000-105203 A JP 2001-60607 A JP 2001-264264 A JP 2004-177284 A Special table 2001-512237 gazette

  In the techniques described in Patent Documents 1 to 9, it is not possible to easily detect defects such as fine foreign matters on the substrate in which repeated patterns and non-repeated patterns are mixed with high sensitivity and at high speed. That is, there is a problem that the detection sensitivity is low in a portion other than a repeated portion such as a memory cell portion. In addition, there is a problem in that the detection sensitivity of a 0.1 μm level minute foreign matter or defect in a region having a high pattern density is low. In the techniques described in Patent Documents 10 and 11, there is a problem that the detection sensitivity of the foreign matter on the wafer surface on which the transparent thin film is formed is low. In the techniques described in Patent Documents 12 and 13, the illumination beam and the side detection optical system are in a plane perpendicular relationship to each other, and the detection optical system is equipped with a spatial filter. In this relationship, the signal of the pattern on the back surface of the transparent thin film cannot be erased. The technique described in Patent Document 13 does not use low-angle illumination and low-angle detection as a means, and the intention of erasing the back surface pattern is not seen.

  In order to solve the above problems, the first object of the present invention is not only a substrate to be inspected such as a wafer having a transparent thin film formed on the surface, but also a substrate to be inspected such as a wafer having a circuit pattern under the transparent film. In contrast, an object of the present invention is to provide a defect inspection apparatus and method capable of inspecting defects such as 0.1 μm level minute foreign matter and scratches with high sensitivity and high speed.

  Further, the second object of the present invention is that the signal of the defect detector does not fluctuate even when the thickness of the transparent thin film formed on the surface fluctuates. The realization of an apparatus capable of inspection.

  In the case of the conventional illumination optical unit and detection optical unit When detecting foreign matter existing on the upper surface of the transparent thin film, the scattered light of the foreign matter entering the detection optical unit arranged vertically above the film due to the influence of thin film interference Under the influence of, the intensity varies. When the illumination light is polarized, scattered light can be detected strongly, but at the same time, fluctuations in the intensity of the scattered light due to film thickness fluctuations cannot be avoided. Further, since the variation in the transparent film thickness is caused by being in the plane of one wafer, the variation in the in-plane sensitivity of the wafer is generated.

In order to achieve the above object, in the present invention, the scattering intensity distribution of a foreign substance such as PSL on the thin film is calculated, and the relationship between the polarization of the illumination light and the scattering intensity with respect to the film thickness variation of the thin film is obtained. As shown in FIG. 8, the thickness of the SiO ₂ thin film was determined on the horizontal axis, the total detected light amount on the vertical axis, and the polarized light as S-polarized light, P-polarized light, and circularly polarized light. Irradiation with circularly polarized light is good because the variation in the amount of light is small relative to the variation in film thickness, as compared with the case of other polarized light. However, since the detected amount of light itself is small, it is impossible to detect scattered light of a minute size. On the other hand, when P-polarized light and S-polarized illumination light is irradiated, the detected light quantity itself can be detected largely, but the detected light quantity varies with respect to the change in film thickness, and stable detection cannot be performed.

  When the polarization of the illumination light is switched and the inspection is performed a plurality of times, detection can be performed complementing each other, but the tact time of the apparatus becomes longer. That is, the throughput is lowered and the performance as an inspection apparatus is lowered.

  In order to solve the above problems, an illumination optical system capable of simultaneously illuminating polarized light of illumination light with S-polarized light and P-polarized light has been devised. That is, when the illumination light is irradiated with P-polarized light or S-polarized light, the light irradiated on the inspection target substrate is reflected by the surface, and the illumination light exits at the same reflection angle as the incident angle. This light is emitted while maintaining the same polarization state as the incident light. By arranging the lens and the total reflection mirror at the tip of the emitted light, the emitted light can be changed to illumination light for irradiating the inspection target substrate again. At this time, if a λ / 4 wavelength plate is disposed between the lens and the total reflection mirror so that the emitted light passes back and forth, the re-incident light can change the polarization direction. Therefore, when irradiated with P-polarized light, re-irradiation with S-polarized light is possible, and when irradiated with S-polarized light, re-irradiation with P-polarized light is possible. By using this mechanism, when the film thickness is small with P-polarized scattered light, strong scattered light can be obtained with the re-irradiated light with S-polarized light. In this case, strong scattered light can be obtained by the re-irradiated light of P-polarized light.

  When irradiating oblique illumination with an inspection apparatus, the lower the elevation angle, the higher the reflectivity of the substrate to be inspected, so the intensity of re-irradiated light does not decrease. It is possible to inspect at the same time.

According to the present invention, the illumination efficiency can be improved, and the scattered light generated from the foreign matter on the surface such as the LSI pattern is not affected by the circuit structure in the LSI pattern by optimizing the irradiation angle of the spatial filter and illumination. In addition, it is possible to avoid the influence of light intensity increase / decrease due to thin film interference of diffracted light generated due to the variation in the thickness of the transparent film such as SiO ₂ formed on the LSI surface, so that the defect detection signal can be detected stably. In addition, the detection threshold provided for detecting the surface foreign matter and separating the background light can be set low. Therefore, it is possible to detect even a very small surface foreign matter of about 0.1 μm, and it is possible to detect with high sensitivity and to prevent the detection of false information.

  Furthermore, the influence of the directionality with the illumination light due to the shape of the defect or the shape of the background pattern can be avoided. In other words, with the illumination optical system of the present invention that re-illuminates illumination light from the side opposite to the irradiation side, there is a foreign object or concave defect that is hidden behind the step of the circuit pattern and does not scatter light However, by irradiating illumination light from the opposite side, it is no longer a shadow of the pattern, so even if it is a foreign object or concave defect that does not emit scattered light with one-way illumination, it will generate scattered light, Its detection becomes easy. In other words, it is possible to increase the detection sensitivity.

  Even when focusing only on the amount of illumination light, the illumination light is irradiated and the reflected light from the surface of the substrate to be inspected is re-reflected by the total reflection mirror in the illumination optical unit to re-illuminate the surface of the inspected substrate. In addition, the same inspection area is illuminated twice, and the amount of irradiation light can be expected to be doubled at the maximum (when the substrate surface to be inspected is 100% reflective).

  First, the concept of the present invention will be described. The present invention is a method for extracting surface anomalies and features. A stage on which a substrate to be inspected is mounted and scanned in a predetermined direction is arranged along the stage traveling direction, and an elliptical illumination light beam that is long in a direction perpendicular to the stage traveling direction is parallel to the stage scanning direction. There is an illumination optical system (1) that irradiates at a predetermined irradiation angle from the normal direction of the substrate, and the illumination system is a plane at a predetermined irradiation angle from the normal direction from a direction of a predetermined inclination. There is an illumination optical system (2) that irradiates the same position as (1), and a predetermined direction from the normal direction to a predetermined direction on the opposite side to (1) with respect to the elliptical illumination light beam. There is an illumination optical system (3) that irradiates the same position as (1) at an irradiation angle. After each illuminating light is reflected by the substrate to be inspected, there is an illuminating optical unit that makes it possible to irradiate the same position in a long ellipse shape by turning the reflected light back by a total reflection mirror. Optical that enables the light reflected by the reflecting mirror to be linearly polarized light whose polarization plane is the same or 90 ° different from the initial polarization direction irradiated to the target substrate, or circularly polarized light or non-polarized light An objective lens for concentrating the upward reflected scattered light emitted in the vertical direction from the substrate to be inspected, and an upward imaging for forming an upward reflected scattered light image collected by the objective lens. An upper photodetector that receives an upper reflected scattered light image formed by the optical system and the upper imaging optical system and converts the image into an upper image signal. Further, it is preferable that the image signal is converted by an A / D converter, and a signal processing system for determining a defect based on each digital image signal is provided.

  In the configuration of the optical system, the illumination optical systems (1), (2), and (3) may be irradiated at the same time. However, in order to make defects appear, they are irradiated alone or several Whether to irradiate in combination can be selected from the defect detection condition table, and equipped with a detection optical unit provided that the illumination light from the reflective illumination optical unit can be irradiated alone or in combination Also good.

  In the configuration of the optical unit, whether the illumination optical system (1), (2), (3) is irradiated with S-polarized light, irradiated with P-polarized light, irradiated with circularly polarized light, or irradiated with non-polarized light. Whether the reflected illumination light is irradiated with the same polarized light as that of the incident light, irradiated with different polarized light, or irradiated with circularly polarized light is stored in the processing condition table of the apparatus. It is possible that optimum conditions can be set depending on the detection target.

  In the configuration of the optical system, the incident angle of the illumination light of the illumination optical unit may be a structure that can be automatically set according to the degree of the defect on the surface to be measured.

  In the configuration of the optical system, the angle in the planar direction of the illumination light of the illumination optical unit may be inclined at about 45 degrees with respect to the longitudinal direction of the slit beam.

  In the configuration of the optical system, the upper digital image processing signal and the oblique digital image processing signal may be merged with neighboring pixels, and a defect may be detected based on the merged image signal.

  In the configuration of the optical system, the feature determination of the defect may be performed by using the upper digital image processing signal and the oblique digital image processing signal simultaneously.

  In the upper detection optical system and the oblique detection optical system of the optical system, the optical system has a spatial filter that shields at least repetition of the circuit pattern existing on the substrate to be inspected. You may comprise so that a shape can be set automatically.

  The signal processing system may include classification means for classifying the detected defects by category.

  In the illumination optical system, the light source may be a laser light source.

  Next, an embodiment according to the present invention will be described with reference to the drawings.

  First, an inspection object 1 for inspecting a defect such as a foreign object according to the present invention will be described with reference to FIGS. As an inspection target object 1 for inspecting defects such as foreign matters, there is a semiconductor wafer 1a in which chips 1aa made of a memory LSI are two-dimensionally arranged at a predetermined interval, as shown in FIG. A chip 1aa made of a memory LSI is mainly formed with a memory cell area 1ab, a peripheral circuit area 1ac made up of a decoder, a control circuit, and the like, and another area 1ad. The memory cell region 1ab is formed by arranging (repeating) memory cell patterns regularly in two dimensions. However, the peripheral circuit region 1ac is formed with a non-repetitive pattern in which the patterns are not regularly arranged two-dimensionally.

As an inspection object 1 for inspecting a defect such as a foreign substance, there is a semiconductor wafer 1b in which chips 1ba made of LSI such as a microcomputer are two-dimensionally arranged at a predetermined interval as shown in FIG. A chip 1ba made of an LSI such as a microcomputer is mainly composed of a register group area 1bb, a memory area 1bc, a CPU core area 1bd, and an input / output area 1be. FIG. 9 conceptually shows the arrangement of the memory area 1bc, the CPU core area 1bd, and the input / output area 1be. The register group region 1bb and the memory portion region 1bc are regularly arranged (repeatedly) in two dimensions. The CPU core area 1bd and the input / output area 1be are formed with non-repeating patterns. As described above, the inspected object 1 for inspecting defects such as foreign matters has the chips regularly arranged even for the semiconductor wafer, but the minimum line width is different for each region in the chip, Moreover, the pattern repeats and does not repeat, and various forms are conceivable.

  The defect inspection apparatus and method for foreign matter or the like according to the present invention provides a zero-order diffracted light from a pattern (linear pattern) consisting of straight lines on a non-repeated pattern region in a chip in such an inspection object 1. The signal is detected from a defect such as a foreign substance by receiving the scattered light generated by the defect such as a foreign substance existing on the non-repetitive pattern area so that it does not enter the entrance pupil of the objective lens, and the position coordinates of the defect Can be calculated.

  Next, a first embodiment of a defect inspection apparatus for foreign matter or the like according to the present invention will be described with reference to FIG.

The first embodiment of a defect inspection apparatus for foreign matter or the like is configured by a stage unit 300 including xyz stages 301, 302, and 303, a theta stage 304, and a stage controller 305, a laser light source 101, a concave lens 102, and a convex lens 103. Beam expander, a beam shaping unit composed of an optical filter group 104 and a mirror 105, an optical branching element (or mirror) 106 that can be switched between a transparent glass plate, an illumination lens 107 having a cylindrical curved surface, and a mirror 108, An illumination optical system unit 100 including three beam spot image forming units 109 and a one-dimensional detector such as a detection lens 201, a spatial filter 202, an image forming lens 203, a zoom lens group 204, and a TDI sensor. (Image sensor) Detection optical system composed of 205 An oblique detection optical system 500 including a one-dimensional detector (image sensor) 501, an objective lens 502, a spatial filter 503, and an imaging lens 504, an A / D converter, a data memory that can be delayed, and a chip A difference processing circuit that takes a signal difference between them, a memory that temporarily stores a difference signal between chips, a threshold calculation processing unit that sets a pattern threshold, a signal processing system 402 configured by a comparison circuit, and a defect detection result such as a foreign object An output means for storing and outputting a defect detection result, a driving system such as a motor, coordinates, a control processing system 401 configured to control a sensor, a display system 403 and an input system 404 are configured.

The three illumination optical system units 100 pass the light emitted from the laser light source 101 through a beam expander composed of a concave lens 102 and a convex lens 103 and an illumination lens 107 having a cylindrical curved surface as shown in FIG. The beam 3 is illuminated from the three directions 10, 11, 12 so that the longitudinal direction of the slit-shaped beam 3 is directed to the chip arrangement direction from the three directions 10, 11, 12 in a plane. . The reason why the slit beam 3 is used as the illumination light is that the inspection of defects such as foreign matters has been speeded up. That is, as shown in FIG. 3, the beam 3 illuminated on the wafer 1 on which the chips 2 are arranged in the x direction in the scanning direction of the x stage 301 and the y direction in the scanning direction of the y stage 302, Is illuminated with a slit beam that is narrow in the scanning direction y and wide in the vertical direction x (scanning direction of the x stage 301). The slit-shaped beam 3 is illuminated so as to be parallel light in the x direction so that an image of a light source is formed in the y direction. The illumination of the slit-shaped beam 3 from the three directions 10, 11, and 12 is selected individually by switching the beam splitter or mirror 106 to a through-glass plate of the same thickness, or simultaneously from the two directions 10, 12. Can be illuminated.

  By making the longitudinal direction of the slit-shaped beam 3 in the chip arrangement direction with respect to the wafer (substrate to be inspected) 1 and at a right angle to the scanning direction y of the y stage 302, between the chips of the image signal The comparison can be simplified, and the defect position coordinates can be easily calculated. As a result, it is possible to increase the speed of defect inspection for foreign matters and the like.

3 and 4 show an illumination lens 104 having a conical shape and a cylindrical curved surface. The conical illumination lens 104 is a lens in which the focal length is different at a position in the longitudinal direction of the cylindrical lens and the focal length is linearly changed. With this configuration, as shown in FIG. 4, even when illuminated obliquely (with both α1 and φ1 tilts compatible), illumination can be performed with a slit-shaped beam 3 that is narrowed down in the y direction and collimated in the x direction. In other words, the illumination lens 104 allows for FIG.
It is possible to realize illumination having parallel light in the x direction as shown in FIG. In particular, as shown in FIG. 3A, by making the slit-shaped beam 3 parallel light in the x direction, a diffracted light pattern is obtained from a circuit pattern in which main straight line groups are directed in the x direction and the y direction. The light can be shielded by the spatial filter 202.

  Next, the illumination lens 104 having a cylindrical curved surface can form the slit beam 3 shown in FIG.

  FIG. 10 is a plan view showing the illumination optical system unit 100 having the three beam spot imaging units in FIG. A laser beam emitted from the laser light source 101 is branched into two optical paths by a branching optical element 11 such as a half mirror, one of which is reflected by mirrors 111 and 112, and is made to enter the concave lens 102 downward by a mirror 113. Can be obtained, and the other travels to a branching optical element 114 such as a half mirror. One of the beams branched by the branching optical element 114 is reflected by the mirror 115 and incident downward on the concave lens 102 by the mirror 117, whereby an illumination beam from 10 directions can be obtained. By making it enter the concave lens 102 downward, an illumination beam from 10 directions can be obtained. By the way, when illuminating only from 11 directions, it can implement | achieve by switching from the branch optical element 150 to the mirror element 118. FIG. Further, in the case of illuminating only from the directions of 10 and 12, it can be realized by leaving the branching optical element 150 from the optical path or switching to a normal optical element. Further, in the case of illumination from only the 12 directions among the illuminations from the 10 and 12 directions, it can be realized by switching from the branch optical element 114 to the mirror element 119.

As the laser light source 101, it is preferable to use the third harmonic THG of a high-power YAG laser and a wavelength of 355 nm because of the branching relationship, but it is not necessarily required to be 355 nm. Further, the laser light source 101 does not need to be YAGTHG. That is, the laser light source 101 may be another light source such as an Ar laser, a nitrogen laser, a He—Cd laser, or an excimer laser.

  The detection optical system unit 200 includes a detection lens (objective lens) 201 for light emitted from the wafer 1, a spatial filter 202 for shielding a Fourier transform image by reflected diffracted light from a repetitive pattern, an imaging lens 203, a TDI sensor, and the like. A one-dimensional detector 205 is configured to detect. The spatial filter 202 is placed at the spatial frequency region of the objective lens 201, that is, at the imaging position of the Fourier transform (corresponding to the exit pupil) so as to shield the Fourier transform image by the reflected diffracted light from the repetitive pattern. Here, the illumination area 3 on the wafer 1 shown in FIG. 10 is imaged on the detector 205 by the objective lens 201 and the imaging lens 203 constituting the relay lens. Reference numeral 4 denotes a light receiving area of a one-dimensional detector 205 such as a TDI sensor.

  As described above, when the slit-shaped beam 3 is illuminated on the wafer (substrate) 1 on which various types of circuit patterns are formed, this reflected diffracted light (or scattered light) is reflected on the wafer surface, circuit pattern. Injecting from defects such as foreign matter. The emitted light is received by the detector 205 through the detection lens 201, the spatial filter 202, and the imaging lens 203, and is photoelectrically converted. However, the illuminance (power) of the beam emitted from the illumination optical system such as the laser light source 101 can be changed by controlling the illumination lens 104 or laser power to change the dynamic range.

Further, it is necessary to inspect a foreign object or a defect that has entered a recess between wirings, an etching residue, and the like with respect to the inspection target substrate (wafer) 1. However, there is a non-repeated pattern on the substrate 1 to be inspected, and in order to prevent 0th-order diffracted light from the non-repeated pattern from entering the objective lens 201, as described above, On the other hand, when the slit-shaped beam 3 having the longitudinal direction in the x direction from the directions 10 and 12 at an angle of approximately 45 degrees is illuminated on the substrate 1, the wirings which are convex portions obstruct the concave portions sufficiently. It becomes difficult to illuminate.

  Therefore, in many cases, the wiring pattern is formed in a right angle and parallel direction, and therefore, by illuminating the slit-shaped beam 3 on the substrate 1 from the direction 11 parallel to the y axis, the wiring pattern between It becomes possible to sufficiently illuminate the recess. In particular, the wiring pattern of the memory LSI is often a linear pattern having a length of several millimeters, and can often be inspected by illumination from this direction 11. Further, depending on the pattern, in the case of the 90-degree direction, the inspection can be performed by rotating the wafer by 90 degrees or changing the illumination direction to the x direction.

  Next, the spatial filter 202 will be described. In the chip 2, there are repeated patterns such as a memory cell area 1ab in the memory LSI 1aa and a register group area 1bb and a memory section area 1bc in the LSI 1ba such as a microcomputer. It is required to shield (diffraction interference light fringes) by the spatial filter 202. In short, in the chip 2, a repetitive pattern, a non-repetitive pattern, and a non-pattern are mixed, and the line widths are also different from each other. The light shielding pattern of the spatial filter 202 is set so as to be erased. As the spatial filter 202, as described in JP-A-5-218163 and JP-A-6-258239, the. If what can change the light shielding pattern is used, it may be changed according to the circuit pattern in the chip 2. Alternatively, a spatial filter 202 having a different light shielding pattern may be prepared and switched according to the circuit pattern in the chip 2. However, when the slit-shaped beam 3 is illuminated from the direction 11, it is necessary to erase the 0th-order diffracted light by shielding it with the spatial filter 202. At this time, naturally, higher-order diffracted light can be eliminated by being shielded by the spatial filter 202. The diffracted light erasing method in the case of repeating and non-repeating patterns existing in the chip 2 on the substrate 1 to be inspected has been described above.

Next, detection sensitivity adjustment according to the defect size of a foreign substance or the like to be detected will be described. That is, when the detection pixel size on the inspection object 1 of the one-dimensional detector (image sensor) 205 such as a TDI sensor is reduced, the detection sensitivity can be improved although the throughput is lowered. Therefore, when detecting defects such as foreign matters having a size of about 0.1 μm or less, it is preferable to switch to the detection optical system 200 that reduces the pixel size. Specifically, it is preferable to have three types of detection optical systems 200 that can change the size of an image on the wafer 1 for pixels such as TDI sensors. As a method of realizing this configuration, the lens group 204 is switched. At this time, from the wafer 1,
It is preferable to design the lens configuration so that the optical path length to the one-dimensional detector 205 such as a TDI sensor does not need to be changed. Of course, if such a design is difficult, a mechanism that can change the distance to the sensor in conjunction with the switching of the lens may be used. Moreover, you may switch what changed the pixel size of sensor itself.

  Next, the effect of reflected illumination will be described. FIG. 6 shows the state of scattered light of PSL on a transparent oxide film having a film thickness on the substrate to be inspected. FIG. 7 shows a graph plotting the detected light amount when the detected light amount is simulated for each polarization state of the illumination light, where the horizontal axis is the film thickness of the transparent oxide film and the vertical axis is the detected light amount. The amount of detected light varies depending on the type of polarized light as the film changes.

  For example, when the film thickness is weak with S-polarized light, the amount of detected light is large with P-polarized light. The reverse is also true. From this situation, it can be seen that if two types of polarized light are prepared, the amount of detected light does not fluctuate with respect to the film thickness. FIG. 5 shows this mechanism in the configuration of the illumination optical unit. For example, when illumination light incident as S-polarized light is reflected on the surface of the substrate to be inspected, the reflected light is totally reflected by placing a condenser lens, a λ / 4 (wavelength) plate, and a total reflection mirror ahead. If an illumination optical system that returns the polarization direction to P-polarized light is constructed, the detection effect can be realized as in the illumination described above.

1 is an overview of an inspection apparatus according to an embodiment of the present invention. The figure explaining an irradiation light spot. The figure explaining an optical system. The figure explaining an optical system. The figure which shows the optical system which concerns on this invention. The figure which shows scattering of light in case a thin film is attached on the wafer surface. The figure which shows the difference in the scattering characteristic by the difference in film thickness. The figure explaining the pattern of a wafer. The figure explaining the pattern of a wafer. The top view which shows the illumination optical system part 100 which has the three beam spot image formation parts of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Test target substrate (wafer), 1a, 1b ... Semiconductor wafer, 1aa ... Memory LSI, 1ab ... Memory cell area, 1ac ... Peripheral circuit area, 1ad ... Other area, 1ba ... LSI such as microcomputer, 1bb ... Register Group area, 1bc ... memory area, 1bd ... CPU core area, 1be ... input / output area, 2 ... chip, 3 ... slit beam (illumination area), 4 ...
Detection area of an image sensor such as a TDI sensor, 100 ... illumination optical system, 101 ... laser light source, 102 ... concave lens, 103 ... convex lens, 104 ... illumination lens, 110 ... 0 degree illumination beam spot imaging unit, 120 ... 45 degree illumination Beam spot imaging unit (11 direction), 130... 45 degree illumination beam spot imaging unit (12 direction), 200... Upper detection optical system, 201... Objective lens (detection lens), 202 and 503. 504 ... imaging lens, 204 ... zoom lens group, 205 ... one-dimensional detector such as a TDI sensor, 207 ... spatial filter control, 208 ... zoom lens control, 300 ... stage system, 301 to 304 ... xyz [theta] stage, 305 ... stage Control, 400 ... arithmetic processing circuit (signal processing system), 401 ... control CPU section, 402 ... signal processing section, 403 Display unit 404 Input unit 500 Oblique detection system 501 Detection sensor 502 Objective lens

Claims (6)

A first illumination optical system that irradiates the inspection object at a predetermined irradiation angle;
A second light that irradiates the same irradiation position as the inspection object irradiated by the first illumination optical system by further reflecting the reflected light reflected by the inspection object by the irradiation light from the first illumination optical system. Illumination optics,
A defect inspection apparatus comprising: The defect inspection apparatus according to claim 1,
The defect inspecting apparatus, wherein the light irradiated by the second illumination optical system is polarized light different from a deflection direction of the light irradiated by the first illumination optical system. The defect inspection apparatus according to claim 1 or 2,
A defect inspection apparatus comprising a control mechanism capable of selecting whether to irradiate light emitted from the first illumination optical system and the second illumination optical system simultaneously or separately. In the defect inspection apparatus in any one of Claims 1-3,
A mechanism is provided that allows selection of irradiation light from the first illumination optical system as S-polarized light, P-polarized light, circularly polarized light, or non-polarized light. A feature defect inspection device. In the defect inspection apparatus in any one of Claims 1-4,
The second illumination optical system includes a mechanism that can select whether to irradiate with the same polarized light as the incident light, irradiate with different polarized light, or irradiate with circularly polarized light. Defect inspection equipment. The defect inspection apparatus according to claim 4 or 5,
What kind of light is irradiated by the first illumination optical system and the second illumination optical system can be stored in the processing condition table of the apparatus, and a mechanism for selecting the condition depending on the detection target is provided. A defect inspection apparatus characterized by that.

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