JP7262917B2 - aperture diaphragm - Google Patents

Description

[001] This application claims priority from U.S. Patent Application No. 15469578, filed March 17, 2017, and U.S. Provisional Patent Application No. , 315 Claiming priority from U.S. Patent Application Serial No. 15/158,632, filed May 19, 2016. All these applications are incorporated herein by reference.

[002] Two-dimensional defect detection has two main modes of specimen illumination. It is bright field, which is insensitive to wafer morphology, and dark field, which collects scattered light and is therefore sensitive to wafer morphology and is particularly useful for identifying flaws.

[003] All known dark field techniques illuminate the wafer at a large oblique angle. While suitable for a wide range of applications, these techniques fail to find the types of defects characterized by local low-angle tilt of the wafer. These types of defects include cracks and stresses that deform the surface.

[004] According to embodiments of the present invention, an aperture stop may be provided that may include a circular region that may include a plurality of points. The plurality of points includes a plurality of opaque region points that can span all polar angles and a plurality of aperture points that can span all polar angles, each aperture point being (a) associated with an illumination angle, and ( b) associated with a corresponding point within the corresponding opaque region associated with the specular angle from the illumination angle associated with the aperture point;

[005] Each opaque region point of the majority of opaque region points may belong to an opaque region associated with a small angular deviation from the specular angle in the virtual plane containing the propagation path of the specular reflection.

[006] A plurality of aperture points may be positioned within a majority distance from the center of the circular region.

[007] According to embodiments of the present invention, an aperture stop may be provided that may include a circular region that may include an opaque spiral area surrounded by one or more aperture areas, each aperture point corresponding to an illumination angle. and associated with the corresponding opaque area points of the opaque spiral area associated with the angle of specular reflection from the illumination angle associated with the aperture point.

[008] According to embodiments of the present invention, an aperture stop may be provided that may include a circular region including at least one opaque area and at least one aperture, for a plurality of distances from the center of the circular region and for each polar angle , there is a pair of points that may be located at a distance from the center of the circular region and may include an opaque region point and an aperture point that may belong to the diameter of the circular region oriented by a polar angle.

[009] Each aperture point may correspond to an illumination angle and each opaque area point may correspond to a specular angle.

[0010] The distance between each opaque region point and the nearest aperture point may correspond to a small angular deviation from the specular angle.

[0011] Small angular deviations shall not exceed 5 degrees.

[0012] The at least one opaque area may include a plurality of radially symmetrical opaque areas. Most opaque areas may be formed as segments of rings.

[0013] The at least one opaque area may include a plurality of radially symmetrical opaque areas. Most of the opaque areas extend along an angular range that does not exceed 90 degrees.

[0014] The at least one opaque area is a spiral opaque area.

[0015] The at least one opaque area approximates a spiral.

[0016] According to embodiments of the present invention, an inspection system may be provided that may include a light source, an objective lens, and an aperture stop. The light source is configured to illuminate an aperture stop, the aperture stop being positioned at the aperture of the objective lens; (i) the aperture stop may comprise a circular area that may comprise a plurality of points, and the plurality of points; may include a plurality of opaque region points that may span all polar angles and a plurality of aperture points that may span all polar angles, each aperture point being associated with (a) an illumination angle, and (b) an aperture (ii) an opaque spiral bounded by one or more aperture areas, where the aperture stop is Each aperture point is associated with an illumination angle and a corresponding opacity of the opaque spiral-shaped area associated with the angle of specular reflection from the illumination angle associated with the aperture point. and (iii) the aperture stop may comprise a circular region which may comprise at least one opaque area and at least one aperture, for a plurality of distances from the center of the circular region and for each polar angle , that there is a pair of points that may be located at a distance from the center of the circular region and may belong to the diameter of the circular region oriented by the polar angle and may include an opaque region point and an aperture point. .

[0017] According to an embodiment of the present invention, illuminating an aperture stop located at the aperture of the objective lens, illuminating the object with light passing through the aperture stop and the objective lens, and passing through the aperture stop collecting with an objective lens the reflected light, where the reflected light differs from the specular light; and directing the reflected light through the aperture stop toward the detector. A method may be provided wherein (i) the aperture stop may comprise a circular area which may include a plurality of points, the plurality of points may extend over all polar angles and a plurality of opaque area points which may extend over all polar angles. A plurality of aperture points may be included, each aperture point having a corresponding opaque region associated with (a) an illumination angle and (b) a specular angle from the illumination angle associated with the aperture point. (ii) the aperture stop may comprise a circular region which may comprise an opaque spiral area surrounded by one or more aperture areas, each aperture point being associated with an illumination angle; and (iii) an aperture stop defines at least one opaque area and at least one aperture. may comprise a circular region that may contain, may be positioned at a distance from the center of the circular region for a plurality of distances from the center of the circular region and for each polar angle may belong to the diameter of the circular region oriented by the polar angle A method wherein at least one of there is a pair of points that may include an opaque region point and an aperture point is true.

[0018] An aperture stop may be provided that may include a non-circular region that may include a plurality of points. The plurality of points may include a plurality of opaque area points and a plurality of aperture points, each aperture point being (a) associated with an illumination angle, and (b) a positive angle from the illumination angle associated with the aperture point. Corresponding points within corresponding opaque regions may be associated with the reflection angles. A non-circular region may be elliptical (not circular), polygonal, or any other shape. A non-circular region may have a non-linear boundary portion, a combination of linear and non-linear boundary portions, and the like.

[0019] Each opaque region point of the majority of opaque region points is associated with a small angular deviation (eg, 2, 3, 4, 5 degrees, etc.) from the specular angle in the virtual plane containing the propagation path of the specular reflection. can belong to the opaque region obtained.

[0020] The plurality of aperture points may form at least one aperture, which may be polygonal.

[0021] The plurality of aperture points may form triangular shaped apertures and trapezoidal shaped apertures.

[0022] The plurality of opacity points may form triangular-shaped opaque regions and trapezoid-shaped opaque regions.

[0023] The non-circular region may have an asymmetric axis. The triangular aperture and trapezoidal opaque region may be positioned on one side of the asymmetric axis, and the triangular opaque region and trapezoidal aperture may be positioned on the other side of the asymmetric axis.

[0024] An aperture stop may be provided that may include a circular region that may include a plurality of points. The plurality of points may include a plurality of opaque area points and a plurality of aperture points, each aperture point being (a) associated with an illumination angle, and (b) a positive angle from the illumination angle associated with the aperture point. Corresponding points within corresponding opaque regions may be associated with the reflection angles. Multiple aperture points may form multiple apertures. The plurality of apertures may include particular apertures that may have boundaries that may include at least one linear boundary portion and at least one non-linear boundary portion.

[0025] Certain apertures may have shapes that differ from the combination of arcs.

[0026] The circular region may have an axis of symmetry. A plurality of apertures may be symmetrical with respect to an axis of symmetry.

[0027] The circular region may include an inner circular portion that may be surrounded by an outer ring. A plurality of inner openings may be positioned within the inner circular portion. A plurality of outer apertures may be positioned within the outer ring.

[0028] The aperture stop may further include at least one aperture in at least one of the inner circular portion and the outer ring.

[0029] The inner opening portions may each be bounded by at least one secant line and an end of the inner circular portion.

[0030] The outer opening portions may each be bounded by at least one radial line, an inner end, and an outer end of the outer ring.

[0031] Three outer openings and two outer openings may be located in the outer ring, and two inner openings may be located in the inner circular region.

[0032] An aperture stop may be provided that may include at least one opaque area and a region that may include at least one aperture. For multiple distances from the axis of the region, and for multiple distances positioned along the axis, there may be a pair of points that may include an opaque region point and an aperture point that may be positioned at that distance from the axis of the region.

[0033] In an aperture stop, the axis of the region may be selected from the axis of symmetry and the axis of asymmetry.

[0034] Each aperture point may correspond to an illumination angle and each opaque area point may correspond to a specular angle.

[0035] The distance between each opaque region point and the nearest aperture point may correspond to a small angular deviation from the specular angle.

[0036] Small angular deviations do not exceed 5 degrees.

[0037] An aperture stop may be provided that may include a circular region that may include at least one opaque region and at least one open region. Each point within the at least one aperture region is associated with (a) an illumination angle and (b) a specular angle within the at least one opaque region from the illumination angle associated with the aperture point. Associated with the corresponding points, the at least one aperture region includes a particular aperture region having a boundary that can include at least one linear boundary portion and at least one non-linear boundary portion.

[0038] For each point within the at least one aperture region, a corresponding point within the at least one opaque region is symmetrical with respect to the center of the non-circular region with respect to the point within the at least one aperture region . Symmetry is the same from the center of the non-circular area on opposite sides and along an imaginary line passing through the center of the non-circular area and the corresponding points in at least one open area and at least one opaque area. It can mean positioned at a distance.

[0039] An aperture stop may be provided that may include a non-circular region that may include at least one opaque region and at least one open region. Each point within the at least one aperture region is associated with (a) an illumination angle and (b) a specular angle within the at least one opaque region from the illumination angle associated with the aperture point. Associated with corresponding points.

[0040] An inspection system may be provided that may include a light source, an objective lens, and an aperture stop. The light source may be configured to illuminate an aperture stop, which may be positioned at the aperture of the objective lens. Additionally, at least one of the following may be true.
a. The aperture stop may include a non-circular area that may include multiple points, and the multiple points may include multiple opaque area points and multiple aperture points. Each aperture point may be associated with a corresponding opaque area point that may be associated with (a) an illumination angle and (b) a specular angle from the illumination angle associated with the aperture point.
b. The aperture stop may include a circular area that may include multiple points. The multiple points may include multiple opaque area points and multiple aperture points. Each aperture point may be associated with a corresponding opaque area point that may be associated with (a) an illumination angle and (b) a specular angle from the illumination angle associated with the aperture point. Multiple aperture points may form multiple apertures. The plurality of apertures may include particular apertures that may have boundaries that may include at least one linear boundary portion and at least one non-linear boundary portion.
c. The aperture stop can include a region that can include at least one opaque area and at least one aperture. For multiple distances from the axis of the region, and for multiples positioned along the axis, there may be a pair of points that may include an opaque region point and an aperture point that may be positioned at a distance from the axis of the region.

[0041] (a) illuminating an aperture stop, which may be located at the aperture of the objective lens; (b) illuminating the object with light passing through the aperture stop and the objective lens; and (c) the aperture stop. (d) directing the reflected light through the aperture stop towards the detector; A method may be provided that may include: Additionally, at least one of the following may be true.
a. The aperture stop can include a circular area that can include at least one opaque area and at least one open area. Each point within the at least one aperture region is associated with (a) an illumination angle and (b) a specular angle within the at least one opaque region from the illumination angle associated with the aperture point. Associated with the corresponding points, the at least one aperture region includes a particular aperture region having a boundary that can include at least one linear boundary portion and at least one non-linear boundary portion.
b. The aperture stop may include a non-circular region that may include at least one opaque region and at least one open region, wherein each point within the at least one open region is associated with (a) an illumination angle, and (b) Associated with a corresponding point within at least one opaque region associated with the specular angle from the illumination angle associated with the aperture point.
c. The aperture stop may include a region that may include at least one opaque area and at least one aperture, for a plurality of distances from the region's axis and for a plurality positioned along the axis at a distance from the region's axis. There is a pair of points that may include a positioned opaque region point and an aperture point.

[0042] The present invention will be more fully understood and appreciated from the following detailed description in conjunction with the accompanying drawings.

1 shows an object, a light source, a beam splitter, an aperture stop, and a camera, according to embodiments of the invention. 4 shows an object, an objective lens, an aperture stop, and blocked rays according to an embodiment of the invention; 4 shows an object, an objective lens, an aperture stop, and unobstructed rays according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; Figure 3 shows an aperture stop and some blocked rays according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; The flat specular areas of two different dies and the gap between the dies with and without adjacent chipping and crack defects are shown. Fig. 2 shows an image of a flat specular reflection area consisting of two different dies and a gap between the dies where chipping and cracking defects are adjacent. FIG. 4 shows an image of a flat specular area from two different dies and a gap between the dies with adjacent chip and crack defects, according to an embodiment of the present invention. 1 illustrates a method according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; 4 shows an aperture stop according to an embodiment of the invention; FIG. 4 shows the relationship between the normalized power of the detected signal and the angular deviation from specular reflection, in accordance with an embodiment of the present invention; FIG.

[0060] Apparatuses implementing the present invention consist primarily of optical components and circuits well known to those skilled in the art and, therefore, details of the circuitry may not obscure the teachings of the present invention or In order not to deviate from the teachings of the invention, no further detail is provided than is deemed necessary for an understanding and appreciation of the underlying concepts of the invention as illustrated above.

[0061] In the following specification, the present invention will be described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes can be made without departing from the broader spirit and scope of the invention as set forth in the appended claims.

[0062] The term "specular reflection" refers to the specular reflection of light from a surface such that the direction of incident light (incident ray) and the direction of reflected outgoing light (reflected ray) are relative to the surface normal. form the same angle, thus (in the drawing) the angle of incidence is equal to the angle of reflection, meaning that the directions of incidence, normal, and reflection are co-angular (wikipedia.org).

[0063] Aperture stops have been provided that provide a means of modifying the microscope objective so that when used in brightfield, low angle darkfield illumination is produced, allowing detection of the types of defects described above. Become.

[0064] The aperture stop may include a shifted arc to block specular reflections from flat surfaces (where the angle of incidence equals the angle of reflection) while blocking low-angle specular reflections (between the angle of incidence and the angle of reflection). (there is a small angle difference of a small angle at ) to return to the camera. Thus, defects that appear as localized wafer tilt appear as bright, high-contrast features to their surroundings.

[0065] Figure 1 illustrates an object 10, a light source 30, a beam splitter 40, an aperture stop 100, an objective lens 20, and a camera 50 according to an embodiment of the invention. Light from light source 30 passes through beamsplitter 40 and is partially blocked by one or more opaque blocks of aperture stop 100 . Light passing through one or more apertures in the aperture stop passes through objective lens 20 and is directed to object 10 .

[0066] Note that each incident light passing through each aperture point of the aperture of aperture stop 100 diverges and illuminates the entire field of view (object). Each point in the field receives contributions of incident light from all points in one or more apertures (this is due to the special location where the diaphragm is located and the design of typical microscope illumination, i.e. Koehler illumination). to cause).

[0067] Light reflected from object 10 is collected by objective lens 20 . A reflected ray, which is a specular reflection of any incident ray, is blocked by the aperture stop. Reflected rays, which are not specular reflections of any incident rays, pass through the aperture stop and are directed by the beamsplitter 40 toward the camera.

[0068] The aperture stop is located at the stop of the objective lens 20 . The objective lens 20 is normally mounted on the microscope.

[0069] Since the aperture stop is located at the object system stop, each point of the aperture stop is at an angle of incidence (for incident rays) or angle of reflection (for reflected rays) to illuminate the entire field of view. be associated. In particular, the center of the aperture stop can correspond to the normal angle of the incident light and the normal angle of the reflected light. The distance between any point on the aperture stop and the center of the aperture stop defines the value of the angle of incidence (angle of reflection).

[0070] The specularly reflected beam from the object is mapped to a field point at the aperture stop. This field point is symmetrical (with respect to the center of the aperture stop) with respect to the initial field point (incident beam).

[0071] An aperture stop is located at the objective stop. Its asymmetrical structure blocks the return path of specularly reflected rays from the object under normal conditions. FIG. 3 shows an incident ray 51 deflected to the right (arrow 52) and then to the left (arrow 53) within the objective lens and impinging on the (horizontal) object 10. FIG. The reflected ray (arrow 54 ), which is the specular reflection of ray 53 , deflects to the left and then to the right (ray 55 ) and is blocked by the opaque area of aperture stop 100 .

[0072] However, light from locally tilted regions of the object (wafer) is reflected at an offset angle to the optical axis. This light is further mapped to a point in the aperture that is not symmetrical with respect to the incident ray. These deflected rays are intentionally trapped by the asymmetry of the aperture stop. This is shown in FIG. 3 where ray 55 is not blocked by aperture stop 100 and ray 56 emerges from the objective lens.

[0073] Thus, the effect of this aperture stop is to focus on low angle surface tilts while reducing reflections from flat areas, resulting in high contrast of low angle defects. A fine aperture stop design allows optimization for the application based on the typical surface tilt shown.

[0074] The aperture stop may be a thin solid disk or may at least comprise a circular area that may be surrounded by a frame. Briefly, the aperture stop is assumed to be circular.

[0075] An aperture stop includes one or more opaque areas to light that have specific openings that allow light to pass through.

[0076] Figure 4 illustrates an aperture stop 100 according to an embodiment of the present invention. Within circular region 120 are opaque areas 101-107 and openings 111-117.

[0077] The bright areas are the apertures and the black voids are the material. The structure of the apertures has areas of alternating material and apertures when viewed in radial cross-section. Furthermore, at any given angle, each point equally spaced (i.e., same radius) from the center of the aperture stop is made from a mating material (one belonging to the aperture and the other belonging to the opaque area). there is It should be noted that there are several advantages to obtaining low specular reflectance for improved wafer map construction processes. This allows the wafer to be completely scanned. Die-to-die alignment, which can be improved by low specular reflection, etc., is required.

[0078] Figure 5 shows that for each incident point (141 and 142) in the aperture, there is a corresponding specular reflection point (121 and 122) blocked by an opaque area. The corresponding point and the incident point belong to the same virtual diameter (152 and 154). This is true for all polar angles (for any diameter in any orientation, including but not limited to diameters 151, 152, 153, and 154). Outside the opaque area 101, the opaque point and the open point are symmetrical.

[0079] Figure 5 further illustrates that each opaque area is radially narrow as it spans along a limited angular range. This allows reflected rays from surfaces with a low slope (relative to the horizontal) to pass through the aperture stop 100 . Typical values are peak response at 0.5 degrees, significant response between 0.3 and 1 degree, and very low specular reflection at 0 degrees.

[0080] The outer diameter of the aperture stop should match the diameter of the objective lens. The center of the aperture stop may be open or fully open.

[0081] FIG. 6 shows a correspondence between aperture points 141, corresponding opaque regions 121, and reflection angles that deviate slightly from the specular angle, according to an embodiment of the present invention.

[0082] Ray 161 passes through point 141 and has an angle of incidence 171 . If the illuminated object (the illuminated point of the object) is horizontal, the reflected ray 163 will reflect with an angle of reflection 172 equal to the angle of incidence 171 . Reflected light ray 163 is blocked by opaque area 121 . Width 135 of opaque area 121 is adjusted to block reflected rays subject to small angular deviations 173 from reflected angle 172 . Reflected rays 162 and 164 (reflected from tilted areas of the wafer illustrated as tilted boxes) are not blocked by opaque area 121 and pass near the boundaries of opaque area 121 .

[0083] Figure 7 illustrates an aperture stop 100 according to an embodiment of the present invention.

[0084] Aperture stop 100 includes an opaque spiral area 181 surrounded by one or more aperture areas 182 . Each aperture point (such as 143) is associated with an illumination angle and a corresponding opaque region point (such as point 123) of the opaque spiral area associated with the angle of specular reflection from the illumination angle associated with the aperture point. associated with. The width of the opaque spiral area 181 can be adjusted so as not to block reflections that are not specular and that deviate at small angles from the specular reflection.

[0085] Figure 8 shows a box 201 made up of two regions of two different dies and a gap 323 between these regions. Regions 211 and 213 may each belong to different dies.

[0086] Figure 8 shows a box 202 made up of two regions 211 and 213 (which are flat, horizontal, and specular) of two different dies, and a gap 212 between these regions. Regions 211 and 213 may each belong to different dies. Also shown in box 202 are chip defect 215 and crack defect 216 proximate gap 212 . An internal crack in the wafer may cause a portion of the wafer to rise (or tilt) slightly, resulting in a crack defect 216 having an upper surface slightly tilted with respect to horizontal.

[0087] FIG. 9 shows images 203, 204, and 205 of flat specular areas from two different dies and the gap between the dies with adjacent chip and crack defects.

[0088] Image 203 was obtained using bright field illumination. In image 203, the proper reflection of metal is bright. Dark areas indicate missing material. This is chipping defect 215 . No cracks are observable.

[0089] Image 204 was obtained using darkfield illumination. In image 204, the proper reflection of metal is dark. Missing material appears bright due to reflections from the edges. Missing defects 215 are detected as bright areas. Crack defects are not observable due to the low tilt angle.

[0090] Image 205 was obtained using a circular aperture stop with a diameter significantly smaller than the effective pupil diameter. A circular aperture stop is placed in the pupil of the objective lens. Such a circular aperture stop allows detection of crack defects, but crack defect 216 appears dark and is difficult to distinguish from chipping defect 215 .

[0091] FIG. 10 illustrates an image diagram 206 according to an embodiment of the present invention.

[0092] In image 206, the proper metal reflection is low (due to the blocking of the specular reflection) and chip defect 215 is much darker than crack defect 216, which is clearly visible. Crack defect 216 is brighter than chip defect 215 , region 211 and gap 212 .

[0093] FIG. 11 illustrates a method 300 according to an embodiment of the invention.

[0094] Method 300 may begin with step 310 of illuminating an aperture stop located at the stop of the objective lens.

[0095] Step 310 may be followed by step 320 of illuminating the object with light passing through an aperture stop and an objective lens.

[0096] Step 320 may be followed by step 330 of collecting the reflected light that passes through the aperture stop, which is different from the specular light, with an objective lens and directing the reflected light that passes through the aperture stop toward the detector.

[0097] The aperture stops referred to in steps 310 and 320 are any aperture stops described herein (including, but not limited to, FIGS. 4, 5, 7, and 12-16). good too.

[0098] With respect to the aperture stop, any description of aperture stops in the Summary of the Invention or elsewhere in the specification can be applied to the illuminated aperture stop in step 310 .

[0099] For example, at least one of the following is true:
(i) the aperture stop includes a circular region including at least one opaque region and at least one open region, wherein each point within the at least one open region (a) corresponds to an illumination angle; and (b) associated with corresponding points within at least one opaque region associated with a specular angle from an illumination angle associated with the aperture point, the at least one aperture region having at least one linear boundary portion and at least one non-linear boundary; including a specific open area with a boundary that includes the portion;
(ii) the aperture stop includes a non-circular area including at least one opaque area and at least one open area, each point within the at least one open area being associated with (a) an illumination angle; and (b) ) associated with corresponding points within at least one opaque region associated with the specular angle from the illumination angle associated with the aperture point;
(iii) the aperture stop comprises a region comprising at least one opaque area and at least one aperture, for a plurality of distances from the region axis and for a plurality positioned along the axis, the distance from the region axis; That there is a pair of points, including an opaque region point and an aperture point, located at .

[0100] FIG. 12 shows an aperture stop 410 including a trapezoidal shaped aperture 422 and a non-circular area formed as a triangle 420 including a triangular shaped aperture 424 surrounded by an opaque area 412 .

[0101] Square 420 has an axis of symmetry 429 (oriented at -45 degrees) and an axis of asymmetry 428 oriented at 45 degrees.

[0102] The asymmetry axis 428 is referred to as the asymmetry axis because within square 420 each aperture point located on one side of the asymmetry axis is such that the corresponding opacity point is in a mirrored position (i.e., on the other side of the asymmetry axis). side).

[0103] A triangular shaped aperture 424 is “mirrored” by a triangular shaped opaque region 421 . Trapezoidal aperture 422 is “mirrored” by trapezoidal opaque region 423 .

[0104] Figure 13 shows three aperture points 431, 432, and 433 and corresponding opaque points 434, 435, and 436, respectively.

[0105] Points 431 and 434 are located on axis 438 , points 432 and 435 are located on axis 437 , and points 433 and 436 are located on axis 439 . Axes 437 and 438 are parallel to axis of symmetry 429 .

[0106] The axes of symmetry and asymmetry may be oriented in other manners (eg, not oriented at 45 degrees and/or -45 degrees). This orientation may be set according to the expected or actual orientation of the symmetrical defect.

[0107] For example, aperture stop 410 is designed to inspect defects expected to be oriented along the X-axis and/or Y-axis (corresponding to 0 degree and 90 degree orientations).

[0108] The shape and orientation of the triangular aperture 424 and the trapezoidal aperture 422 allow for non-specular reflection from horizontal or vertical defects.

[0109] Figures 14-16 illustrate an aperture stop 450 according to an embodiment of the present invention.

[0110] Aperture stop 450 is an embodiment of an aperture stop that is not spiral and differs from the approximation of a spiral.

[0111] Aperture stop 450 includes three apertures 461 , 462 , and 463 . Note that openings 463 and 462 may be combined and opening 465 (see FIG. 15) may be separated from the rest of opening 462 .

[0112] Aperture stop 450 has an axis of symmetry 491 and an axis of asymmetry 492 . This symmetry is approximate because aperture 463 and aperture 465 differ in their relationship to aperture 455 .

[0113] Aperture stop 450 is also designed to inspect defects expected to be oriented along the X-axis and/or Y-axis (corresponding to 0 degree and 90 degree orientations).

[0114] Aperture stop 450 (see FIG. 17) passes more (less attenuated) reflected signals with an angular deviation of 1 to 5 degrees (relative to specular reflection) than aperture stop 410. FIG. See curve 720 (related to aperture stop 450) versus curve 710 (related to aperture stop 410) in FIG.

[0115] A circular region 459 of the aperture stop may be formed from an inner circular portion 452 and an outer ring 451 surrounding the inner circular portion 452 .

[0116] The various openings and/or opening portions located within the inner circular portion 452 are referred to as inner openings and/or inner opening portions, respectively.

[0117] The various openings and/or opening portions located within the outer ring 451 are referred to as outer openings and/or outer opening portions, respectively.

[00118] Aperture 462 has linear edges 4621, 4623, 4625, 4627, 4629, 4651, 4652, 4653, 4654, 4656 and nonlinear edges 4622, 4624, 4626, 4628, 4655, and 4657.

[00119] The linear edges 4621, 4652 are parallel to the axis of asymmetry and are secant lines of the inner circular region 452.

[00120] Linear edges 4623, 2625, 4627, 4629, 4654, and 4656 are part of the virtual diameter of aperture stop 450. FIG.

[00121] Linear edges 4651 and 4653 are oriented (less than 90 degrees) with respect to the axis of asymmetry and are not part of any diameter of aperture stop 450 .

[00122] Aperture 461 has linear edges 4611, 4613, and 4615 and has non-linear edge 4614. FIG.

[00123] A linear edge 4611 is parallel to the axis of asymmetry and is a secant of the inner circular region 452 .

[00124] Linear edge 4613 is a portion of the virtual diameter of aperture stop 450 .

[00125] Linear edges 4612 and 4616 are oriented (less than 90 degrees) with respect to the axis of asymmetry and are not part of any diameter of aperture stop 450. FIG.

[00126] Edges 4614, 4624, 4628, and 4655 may be part of the outer end of outer ring 451. FIG.

[00127] Edges 4622, 4651, 4653, and 4657 may be portions of the inner end of outer ring 451 that are outside of inner circular region 452. FIG.

[0128] Figure 16 shows five aperture points 471, 472, 473, 474, and 475 and corresponding opaque points 476, 477, 478, 479, and 480, respectively.

[0129] Each pair of aperture points and corresponding opacity points is positioned on the diameter of aperture stop 450 on opposite sides of each other at the same distance from the center of aperture stop 450 .

[00130] The axes of symmetry and asymmetry may be oriented in other manners (eg, not oriented at 45 degrees and/or -45 degrees). This orientation may be set according to the expected or actual orientation of the symmetrical defect.

[00131] Those skilled in the art will recognize that the boundaries between the functions of the operations described above are merely exemplary. The functionality of multiple actions may be combined into a single action and/or the functionality of a single action may be distributed among additional actions. Further, alternative embodiments may include multiple instances of particular acts, and the order of acts may be changed in various other embodiments.

[00132] Therefore, it should be understood that the structures shown herein are exemplary only, and that in practice many other structures may be implemented to achieve the same functionality. In an abstract, but still definite sense, effectively "associated" with any arrangement of components that accomplish the same function such that the desired function is achieved. Thus, any two components that combine to achieve a specified function, regardless of structure or intermediate components, are considered "associated" with each other such that the desired function is achieved. good too. Similarly, any two components so associated are further considered to be "operably connected" or "operably linked" to each other to accomplish the desired function. good too.

[00133] However, other modifications, variations, and alternatives are possible. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

[00134] The present application is not limited to two dimensions, but can be extended to three-dimensional inspection. The substrates to be inspected are not limited to wafers, but may include any kind of substrates, especially flat substrates such as printed circuit boards, solar panels, MEMS devices.

[00135] The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The terminology used in this way means that the embodiments of the invention described herein are operable in orientations different from those shown, for example, or otherwise described herein. As such, they are understood to be interchangeable under appropriate circumstances.

[00136] Further, as used herein, the indefinite articles (a or an) are defined as one or more than one. Also, the use of introductory phrases such as "at least one" and "one or more" in a claim is used to introduce an element of another claim by the indefinite article "a" or "an." However, any particular claim containing a claim element so introduced may be excluded even if the same claim includes the introductory phrases "one or more" or "at least one" and "a" or "an". The inclusion of any indefinite article such as , should not be construed as limiting the invention to the inclusion of only one such element. The same is true of the use of the definite article. Unless stated otherwise, expressions such as "first" and "second" are used to arbitrarily distinguish between the elements such expressions represent.

[00137] Accordingly, these representations are not necessarily intended to indicate temporal prioritization or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

Claims (39)

an aperture stop comprising a circular region comprising at least one opaque region and at least one open region;
Each point within the at least one aperture region is associated with (a) an illumination angle and (b) the at least one opacity associated with a specular angle from the illumination angle associated with the aperture point. Associated with corresponding points in the region,
wherein the at least one aperture region comprises a first aperture region having a boundary comprising at least one linear boundary portion and at least one non-linear boundary portion;
said circular region comprising an inner circular portion surrounded by an outer ring;
a plurality of inner openings positioned within the inner circular portion;
An aperture stop having a plurality of outer apertures positioned within said outer ring. 2. The aperture stop of claim 1, wherein said first aperture region has a shape different from a combination of arcs. 2. The aperture stop of claim 1, wherein said circular region has an axis of symmetry and said plurality of said aperture regions are symmetrical with respect to said axis of symmetry. 2. The aperture stop of claim 1, further comprising at least one aperture region in at least one of said inner circular portion and said outer ring. 2. The aperture stop of claim 1, wherein each of said inner aperture portions is bounded by at least one secant line and an edge of said inner circular portion. 2. The aperture stop of claim 1, wherein each of said outer aperture portions is bounded by at least one radial line of said outer ring, an inner edge and an outer edge. 2. The aperture stop of claim 1, wherein three said outer aperture portions are located within said outer ring and two inner aperture portions are located within an inner circular region. 2. The method according to claim 1, wherein the at least one linear boundary section consists of a radial linear boundary section and a linear boundary section which does not belong to any diameter of the aperture stop towards the axis of symmetry of the aperture stop. Aperture stop as stated. 9. The aperture stop of claim 8, wherein the aperture stop has a first axis of symmetry and a second axis of symmetry. 2. The aperture stop of claim 1, wherein the first aperture region includes five linear boundary portions and one non-linear boundary portion. 2. The aperture stop of claim 1, wherein the first aperture region includes a plurality of linear boundary portions and a plurality of non-linear boundary portions. 2. The aperture stop of claim 1, wherein said at least one aperture region includes a second aperture region having a boundary comprising one or more linear boundary portions and one or more non-linear boundary portions. 13. The aperture stop of claim 12, wherein said second aperture region includes three outer aperture portions and one inner aperture portion. 14. The aperture stop of claim 13, wherein said one inner aperture portion has an axis of symmetry and two of said three outer aperture portions are symmetrically arranged with respect to said axis of symmetry. 13. The aperture stop of claim 12, wherein said at least one aperture region includes a third aperture region having a boundary consisting of one or more linear boundary portions and one or more non-linear boundary portions. 16. The aperture stop of claim 15, wherein said third aperture region has one outer aperture portion. An inspection system comprising a light source, an objective lens, and an aperture stop,
wherein the light source is configured to illuminate the aperture stop;
the aperture stop is positioned at the aperture of the objective lens;
said aperture stop comprising a circular region comprising at least one opaque region and at least one open region;
Each point within the at least one aperture region is associated with (a) an illumination angle and (b) the at least one opacity associated with a specular angle from the illumination angle associated with the aperture point. Associated with corresponding points in the region,
wherein the at least one aperture region comprises a first aperture region having a boundary comprising at least one linear boundary portion and at least one non-linear boundary portion;
the circular region includes an inner circular portion surrounded by an outer ring;
a plurality of inner openings positioned within the inner circular portion;
A system, wherein a plurality of outer openings are positioned within said outer ring. 18. The inspection system of claim 17, wherein the first open area has a shape different than a combination of arcs. 18. The inspection system of claim 17, wherein the circular area has an axis of symmetry and the plurality of open areas are symmetrical with respect to the axis of symmetry. 18. The inspection system of claim 17, wherein said aperture stop further includes at least one open area in at least one of said inner circular portion and said outer ring. 18. The inspection system of claim 17, wherein each of said inner opening portions is bounded by at least one secant line and an end of said inner circular portion. 18. The inspection system of claim 17, wherein each of said outer opening portions is bounded by at least one radial line, an inner end and an outer end of said outer ring. 18. The inspection system of claim 17, wherein four outer openings are located within said outer ring and two inner openings are located within said inner circular portion . illuminating an aperture stop located at the stop of the objective lens;
illuminating an object with light passing through the aperture stop and the objective lens;
condensing the reflected light passing through the aperture stop by the objective lens, the reflected light being different from specularly reflected light;
directing the reflected light through the aperture stop toward a detector;
a method comprising
said aperture stop comprising a circular region comprising at least one opaque region and at least one open region;
Each point within the at least one aperture region is associated with (a) an illumination angle and (b) the at least one opacity associated with a specular angle from the illumination angle associated with the aperture point. Associated with corresponding points in the region,
wherein the at least one aperture region comprises a first aperture region having a boundary comprising at least one linear boundary portion and at least one non-linear boundary portion;
said circular region comprising an inner circular portion surrounded by an outer ring;
a plurality of inner openings positioned within the inner circular portion;
A method, wherein a plurality of outer openings are positioned within said outer ring. 25. The method of claim 24, wherein the first open area has a shape different from a combination of arcs. 25. The method of claim 24, wherein the circular area has an axis of symmetry and the plurality of open areas are symmetrical with respect to the axis of symmetry. 25. The method of claim 24, wherein said aperture stop further comprises at least one open area in at least one of said inner circular portion and said outer ring. 25. The method of claim 24, wherein each of said inner opening portions is bounded by at least one secant line and an end of said inner circular portion. 25. The method of claim 24, wherein each of said outer opening portions is bounded by at least one radial line, an inner end and an outer end of said outer ring. 25. The method of claim 24, wherein four outer openings are located within said outer ring and two inner openings are located within said inner circular portion . 25. The method of claim 24, wherein the at least one linear boundary section comprises a radial linear boundary section and a linear boundary section directed to the axis of symmetry of the aperture stop and not belonging to any diameter of the aperture stop. . 32. The method of claim 31, wherein the aperture stop has a first axis of symmetry and a second axis of symmetry. 25. The method of claim 24, wherein the first open area includes five linear boundary portions and one non-linear boundary portion. 25. The method of claim 24, wherein the first open area includes a plurality of linear boundary portions and a plurality of non-linear boundary portions. 25. The method of claim 24, wherein the at least one aperture region includes a second aperture region having boundaries that include one or more linear boundary portions and one or more non-linear boundary portions. 36. The method of claim 35, wherein said second open area includes three outer openings and one inner opening. 37. The method of claim 36, wherein the one inner opening portion has an axis of symmetry and two of the three outer opening portions are symmetrically arranged about the axis of symmetry. 36. The method of claim 35, wherein the at least one aperture region includes a third aperture region having boundaries that include one or more linear boundary portions and one or more non-linear boundary portions. 39. The method of claim 38, wherein said third open area has one outer open portion.

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