JP5414743B2 - Macro inspection device - Google Patents

Description

  The present invention relates to a macro inspection apparatus that inspects a size variation of a concavo-convex pattern on a surface of an inspection object.

  One of inspections performed in the manufacturing process of semiconductors, liquid crystals, etc. is a macro inspection. The macro inspection is effective in that the surface state (flatness, pattern shape, presence / absence of defects, etc.) of a film or the like provided on the substrate can be visually grasped at once in a wide range.

  Japanese Patent Application Publication No. 2009-139333 discloses a macro inspection apparatus for inspecting the flatness of the surface of an object to be inspected. This macro inspection apparatus inspects the flatness of the surface of the inspection object by receiving reflected light from the edge of the light irradiation region on the surface of the inspection object with a line sensor.

  Published patent publication 2010-537219 discloses a dark field inspection apparatus. This dark field inspection apparatus inspects the surface state (defect, pattern shape) of an inspection object using scattered light from the inspection object.

JP 2009-139333 A Special table 2010-537219 gazette

  The macro inspection apparatus of Patent Document 1 is an effective apparatus in that the detection sensitivity is improved by using reflected light from the edge of a light irradiation region with high directivity in a bright field optical system. However, it is necessary to further improve the detection sensitivity in order to detect the size variation of the uneven pattern on the surface of the object to be inspected, particularly the fine pattern.

  The dark field inspection apparatus of Patent Document 2 is characterized in that in the dark field optical system, the collection efficiency of scattered light in the imaging unit is improved. However, since scattered light from the object to be inspected is used, it is not an effective device for detecting the size variation of the uneven pattern on the surface of the object to be inspected, particularly a fine pattern.

  Accordingly, an object of the present invention is to provide a macro inspection apparatus capable of detecting a concavo-convex pattern on the surface of an object to be inspected, in particular, a fine pattern size variation and its distribution with high sensitivity.

  The present invention is a macro inspection apparatus that inspects the size variation of the uneven pattern on the surface of an inspection object. The macro inspection apparatus includes a stage for placing an inspection object, a diffusion light source that irradiates light to the inspection object side from a predetermined angle direction with respect to the surface of the inspection object, and reflection from the surface of the inspection object. A line sensor that can receive light, and a reflected light beam that is provided between the object to be inspected and the line sensor, and that is caused by the light beam from the edge of the diffused light source among the reflected light, is provided on at least one of both ends of the line sensor. And an optical system for guiding the reflected light to the line sensor so that the light is received only in the predetermined region.

  According to the present invention, a reflected light beam reflecting the size variation of the uneven pattern on the surface of the object to be inspected is received in a predetermined region set at the end of the line sensor, thereby highly sensitive to the fine pattern size variation and its distribution. Can be detected.

  In one embodiment of the present invention, the optical system includes a lens, and the width (wt) of the predetermined region is determined by the product (wt = a × b) of the resolution (a) and the optical magnification (b) of the lens. Further, the optical system can include a knife edge for guiding the reflected light flux to a predetermined region.

  According to one embodiment of the present invention, it is possible to further improve the detection sensitivity of a fine pattern size variation by optimizing a predetermined region by setting a lens or knife edge of an optical system.

  In one embodiment of the present invention, the output of the line sensor changes linearly with respect to the size variation of the concavo-convex pattern according to the reflected light beam received in the predetermined region.

  According to one aspect of the present invention, it is possible to accurately detect a minute pattern size variation directly from an output of a line sensor or from an image processing result thereof.

It is a figure which shows the macro inspection apparatus of one Embodiment of this invention. It is a figure for demonstrating the method to detect the size variation of an uneven | corrugated pattern. It is a figure for demonstrating a transition area | region. It is a figure for demonstrating the change of the reflection angle in a periodic well structure. It is a figure which shows the test result by one Example of this invention.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a macro inspection apparatus 100 according to an embodiment of the present invention. In FIG. 1, an inspection object 2 is placed on a circular stage 1. The stage 1 is moved in the direction of rotation (θ), horizontal (X) or vertical (Y) by the linear motor 3 under the control of the stage controller 4. The diffused light source 5 is moved along the arc-shaped rail 6 by the stepping motor 7 under the control of the controller 8. The diffusion light source 5 is set at a predetermined angle with respect to the upper surface of the inspection object 2 on the stage 1. The predetermined angle can be arbitrarily set according to the measurement state. The brightness of the diffused light source 5 is adjusted by the light source 10.

  Similarly to the light source 5, the line sensor camera 9 is moved along the arc-shaped rail 6 by the stepping motor 7 under the control of the controller 8. A predetermined optical system 12 for guiding reflected light from the surface of the inspection object to the line sensor 9 is provided at the front of the line sensor camera 9. The optical system 12 only needs to be between the inspection object and the line sensor, and may be integrated with the line sensor 9. The output of the line sensor camera 9 enters the image processing means 11. The image processing unit 11 controls the power supply 10 for the stage controller 4, the controller 8, the line sensor camera 9, and the diffused light source 5. In FIG. 1, only one diffusion light source 5 and one line sensor camera 9 are shown, but two or more may be arranged according to the size and shape of the object to be inspected. The above is the outline of FIG. Next, each configuration in FIG. 1 will be further described.

  The stage 1 can have any shape other than a circle. It is desirable that the stage 1 has a structure in which reflected light from other than the surface of the inspection object 2 is hardly generated as much as possible. Specifically, when the inspection object 2 is transparent and sufficiently scattered light is generated on the surface thereof, the stage 1 may be made of a material that becomes a mirror surface with respect to the light (wavelength) of the diffused light source 5. desirable. When the surface of the inspection object 2 is a mirror surface and no scattered light is generated on the surface, the stage 1 preferably absorbs the light (wavelength) of the diffused light source 5 and is made of a matte material.

  The inspection object 2 is, for example, a thin film on a semiconductor substrate (semiconductor wafer), a liquid crystal layer on a glass substrate, a hard disk, a patterned medium, etc., and has a concavo-convex pattern in at least a certain region on the surface thereof Is applicable. However, the object to be inspected 2 is not limited to these, and may basically be anything as long as it basically has a surface with a predetermined area and has an uneven pattern. The concavo-convex pattern referred to here means a periodic structure in which the concavo-convex is repeated. In addition, the size of the concave / convex pattern is used to mean one or more of the width of the convex portion, the width of the concave portion, or the pitch (width of one concave / convex portion) constituting the concave / convex pattern. The size includes, for example, any size from the nanometer (nm) range to the micrometer (μm) range.

  The diffused light source 5 only needs to emit substantially uniform light having no directivity over a predetermined area, and may be a so-called surface light source capable of emitting uniform light. As the diffused light source 5, the light source can be arbitrarily selected including a light bulb type such as an incandescent bulb or a halogen bulb, a fluorescent lamp type, or a light emitting element such as an LED or a laser diode arranged on an array. . In addition, an optical system (lens, diffuser plate, etc.) for obtaining a diffusion effect can be installed integrally with the light source or outside the output part of the light source. As the wavelength of the light source, a wide wavelength or a predetermined wavelength band can be selected. The selection is performed according to the state (material, optical characteristics, etc.) of the inspection object and the optical characteristics (wavelength characteristics, etc.) of the line sensor camera 9 and the optical system 12.

  The line sensor camera 9 only needs to be capable of acquiring an image for each dimension by arranging light receiving elements (pixels) in a line. The line sensor camera 9 includes, for example, a one-dimensional CCD. The number of pixels is selected according to the size of the inspection object 2. When the size of the inspection object 2 is large and cannot be covered by one line sensor camera 9, two or more line sensor cameras are used.

  The diffusion light source 5 and the line sensor camera 9 can vary the angle with respect to the surface of the inspection object 2 by a predetermined minimum control angle Δθ by the stepping motor 7. The minimum control angle Δθ by the stepping motor 7 is, for example, 1/1000 degrees or less. The minimum control angle is preferably as small as possible.

  The optical system 12 receives a reflected light beam caused by a light beam from the edge portion of the diffused light source 5 out of reflected light from the surface of the inspection object 2 only in a predetermined region provided at at least one of both ends of the line sensor 9. Configured to be. The optical system 12 includes an optical fixture for adjusting the trajectory of the reflected light beam such as a lens or a knife edge. The function of the optical system 12 will be further described later.

  The image processing means 11 processes the image information from the line sensor camera 9 based on a predetermined measurement program. The image processing means 11 controls the controllers 4 and 8 and the illumination power supply 10. The image processing means 11 includes a card (circuit board) for controlling the line sensor camera 9, a circuit board for controlling the controllers 4 and 8 or the power supply 10 for illumination, a memory for storing image data, and the like. The image processing means 11 corresponds to, for example, a personal computer (PC) having a display unit for displaying image processing results and the like, an input unit for inputting measurement conditions and the like.

  FIG. 2 is a diagram for explaining a method of detecting the size variation of the concavo-convex pattern in the macro inspection apparatus 100 of FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals. Note that FIG. 2 shows a case where the inspection object 2 is a substance that transmits light in order to facilitate understanding of the flow of the light beam. When the inspection object 2 is made of a material that reflects light, the diffused light source 5 is positioned on the right side of the inspection object 2, that is, on the line sensor camera side, more specifically, in a line-symmetrical position with respect to the inspection object 2. Placed in.

In FIG. 2, a lens 121 and a knife edge 122 are used as the optical system 12 in FIG. 1 to control the light flux toward the CCD 91 in the line sensor. The knife edge 122 may be provided only on one of the upper side and the lower side. The optical arrangement of FIG. 2 constitutes a kind of dark field optical system. That is, the diffused light source 5 is disposed outside the visual field range W1 of the CCD 91 on the diffused light source 5 side with respect to the inspection object 2, and the diffused light from the diffused light source 5, for example, the light beams L6 and L7 are outside the visual field range of the CCD 91. . In other words, only the light beams within the range of the light beams L1 and L4 constituting the visual field range W1 of the CCD 91 can enter the CCD 91. The luminous fluxes L1 and L4 are so-called luminous fluxes indicating the boundary between the dark field optical system and the bright field optical system with respect to the inspection object 2.

  In this state, unlike the general dark field optical system, the present invention is characterized in that the CCD 91 receives a part of the regular reflection light, that is, the light flux in the transition region. Here, the transition region means a predetermined region where the dark field optical system transitions to the bright field optical system, in other words, a boundary region between the two. The transition area is preset at the upper end or lower end of the pixel range of the CCD 91.

  FIG. 3 is a diagram for explaining the transition region. In FIG. 3, a predetermined area at the lower end of the pixel range W3 of the CCD 91 is a transition area W4. The transition region W4 may be provided at the upper end of the pixel range W3 of the CCD 91. In FIG. 3, the light beam L <b> 4 indicating the boundary between the dark field optical system and the bright field optical system, which is also shown in FIG. 2, is incident on the lower end of the pixel range W <b> 3 of the CCD 91. It is shown. As illustrated in FIG. 2, the light beam L4 corresponds to a reflected light beam L4 in which the light beam from the edge portion (lower end) of the diffused light source 5 is reflected from the surface of the inspection object 2. Therefore, the reflected light beam L4 reflects the size variation state of the uneven pattern on the surface of the inspection object 2, and the size variation state can be detected by detecting the reflected light beam L4.

  In the present invention, the reflected light beam L4, more specifically, the reflected light beam L4 reflected from the surface of the inspection object 2 by the light beam from the edge portion (lower end) of the diffused light source 5 is guided to the transition region W4. The state of the size variation of the uneven pattern on the surface of the inspection object 2 is detected. That is, by utilizing the fact that the light intensity (photosensitivity) 15 varies greatly depending on whether the reflected light beam L4 is incident on the transition region W4 or whether the amount of incident light is large or small, the surface of the inspection object 2 is changed. It is possible to detect the size variation state of the uneven pattern with high sensitivity. In FIG. 3, the broken line portion indicated by reference numeral 5 is an image of the appearance of the diffused light source 5, and the transition region W <b> 4 is based on whether or not the edge portion of the diffused light source 5 is reflected. The light intensity (light sensitivity) 15 changes greatly. The detection sensitivity becomes higher as the inclination angle of the light intensity (light sensitivity) 15 in the transition region W4 becomes steeper.

  The range of the transition area W4 depends on the resolution of the lens 121. For example, when the resolution of the lens 121 is 5 μm, the transition area W4 on the CCD 91 surface is 5-0 when the optical magnification M is 1 to 0.1 times. The range is 5 μm.

  Next, detection of the size variation of the concavo-convex pattern on the surface of the inspection object by the macro inspection apparatus 100 according to an embodiment of the present invention will be described. A light beam reflected by an inspection object having a periodic structure such as an uneven pattern on the surface may slightly shift the reflection angle with respect to the incident angle on the periodic structure. The present invention utilizes the fact that the incident position (incident light amount) of the reflected light beam on the transition region W4 of the CCD 9 changes due to this slight deviation in the reflection angle. That is, the size variation state of the concavo-convex pattern is detected from the change in the amount of incident light (= change in the CCD output) to the transition region W4 caused by the deviation in the reflection angle.

  FIG. 4 is a diagram for explaining the change in the reflection angle in a periodic structure such as an uneven pattern. In FIG. 4, as an example, it is assumed that light (La, Lb) is incident from a point light source S to a fine periodic well (concave / convex) structure 16 having a depth h and a pitch p equal to or less than the light wavelength. . In such a fine periodic well structure, the equivalent height y of the reflective surface 18 with respect to the bottom surface of the well is expressed by the reflected light intensity from the top surface and the bottom surface as shown in the following formula (1). It can be determined by a weighted average of reflected light intensity.

That is, when the top surface reflectance is r1, the bottom surface reflectance is r2, the incident angle is a, the top surface width is w, and the pitch of the periodic structure is p,

y = h * r1 * w / (r1 * w + r2 * z) ------------ (1)
here,
z = max (0, p−w−2h * tan (a)) ------ (2)

In the case of incident light from a point light source, the incident angle a changes as shown in the following equation (3) depending on the incident position x. Therefore, from the above equations (1) and (2), it can be seen that the height y of the reflecting surface 18 is also a function of the position x, and the reflecting surface 18 has an inclination dy / dx equivalently. The inclination dy / dx of the reflecting surface 18 represents a slight deviation in the reflection angle.

x = R * tan (a) ---------- (3)
<=>
a = arctan (x / R) ------- (4)

Hereinafter, the equivalent inclination dy / dx of the reflecting surface 18 is obtained using the equations (1) to (4).

dz / da = 0 (z = 0) --------------------------------- (5)
dz / da = −2h / cos ² (a) (z> 0) ------------------ (5b)
dy / dz = −h * r1 * w / (r1 * w + r2 * z) ² * r2 ----------- (6)
da / dx = 1 / (dx / da) = 1 / (R / cos ² (a)) = cos ² (a) / R ----- (7)
dy / dx = 0 (z = 0) --------------------------------- (8a)
dy / dx
= dy / dz * dz / da * da / dx
= −h * r1 * w / (r1 * w + r2 * z) ² * r2 * {− h / cos ² (a)} * cos ² (a) / R
= 2h ² * r1 * r2 * w / (r1 * w + r2 * z) ² / R (z> 0) ------ (8b)

When the distance from the periodic well (concave / convex) structure 16 to the lens 121 is L, the change b of the incident position of the lens 121 due to the reflected light shift can be calculated by the following equation. This change b of the lens incident position causes a change in the incident position (incident light amount) of the reflected light beam to the transition region W4 of the CCD 9.

b = 0 (z = 0) --------- (9a)
b = L * dy / dx
= L * 2h ² * r1 * r2 * / R * w / (r1 * w + r2 * z) ²
(z> 0) --------- (9b)

  As a result of calculation using the model of the periodic well (concave / convex) structure 16 in FIG. 4, for example, when the difference in the line width (upper surface width w in FIG. 4) in the periodic structure is several nanometers, the reflection angle difference is about 0.1 radians. Occurs. In this case, in the line sensor 9 in which the distance from the periodic well (unevenness) structure 16 to the lens 121 is about 800 mm, an incident distance difference of about 100 nm is generated. In the present invention, by receiving this difference in incident distance of about 100 nm in the above-described transition region W4, it is possible to detect a size variation of a minute periodic well (unevenness) structure of several nm. That is, in the range of the transition region W4, a minute difference in reflection angle of the reflected light beam can be detected as a large difference in sensitivity.

  For example, when the pixel size of the CCD 9 is 50 μm and the pixel size is 14 μm, the optical magnification is 0.28 times. At this time, assuming that the resolution of the lens is 5 μm, the range of the transition region W4 on the surface of the CCD 9 is 5 × 0.28, which is 1.4 μm. It can be seen that the incident distance difference around 100 nm (0.1 μm) has a weight of about 7% at (0.1 / 1.4). Therefore, when the difference in line width (upper surface width w in FIG. 4) is several nm, it is possible to detect the contrast as about 255 × 0.07 = 18 luminance.

As an example of the present invention, one substrate was divided into six regions, and uneven patterns having different line widths (convex portion widths) were formed in each region, and the uneven patterns in each region were inspected. The concavo-convex pattern was made of a photoresist, and the line width was changed in six steps in the range of 60 to 90 nm. The inspection conditions at this time are shown below.

・ Distance L from the substrate to the lens: 1m
・ CCD pixel size: 150μm
・ Pixel size: 14μm
・ Optical magnification: 0.0933
・ Lens resolution: 5μm
・ Width of transition region W4: 0.465 μm

  FIG. 5 is a diagram showing a test result according to an embodiment of the present invention. The vertical axis in FIG. 5 is the pattern line width (convex part width) of the concave-convex pattern, and the horizontal axis is the reflected light intensity (relative luminance). The reflected light intensity (relative luminance) is a relative value calculated based on the output of the line sensor 9 corresponding to the reflected light beam received in the predetermined area W4. The six black circles 19 in FIG. 5 are measurement results of the concavo-convex pattern having six line widths. As is apparent from the graph 20 obtained by extrapolating the measurement results, it can be seen that according to one embodiment of the present invention, the pattern line width and the reflected light intensity are in a substantially linear relationship. . Therefore, according to one embodiment of the present invention, the fluctuation of the line width of the concavo-convex pattern can be detected as the reflected light intensity, in other words, the luminance value or the gray scale after image processing.

  The embodiment of the present invention has been described with reference to FIGS. However, the present invention is not limited to these embodiments. The present invention can be implemented in variously modified, modified, and modified embodiments based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Stage 2 Inspected object 3 Linear motor 4, 8 Controller 5 Light source 6 Rail 7 Stepping motor 9 Line sensor camera
DESCRIPTION OF SYMBOLS 10 Power supply 11 for light sources Image processing apparatus
15 Light intensity (light sensitivity)
16th well structure 18 Virtual reflection surface 100 Black inspection device

Claims (5)

A macro inspection device for inspecting the size variation of the uneven pattern on the surface of the object to be inspected,
A stage for placing the object to be inspected;
A diffusion light source that irradiates light on the inspection object side from a predetermined angle direction with respect to the surface of the inspection object;
A line sensor capable of receiving reflected light from the surface of the inspection object;
A predetermined region provided between at least one of the both ends of the line sensor, which is provided between the object to be inspected and the line sensor, and a reflected light beam caused by a light beam from an edge portion of the diffused light source among the reflected light. only as received by, and an optical system for guiding the reflected light to the line sensor,
A macro inspection apparatus , wherein the diffused light source is arranged such that an edge portion of the diffused light source is located in a boundary region between a dark field optical system and a bright field optical system with respect to the inspection object. The optical system includes a lens;
The macro inspection apparatus according to claim 1, wherein the width (wt) of the predetermined region is determined by a product (wt = a × b) of the resolution (a) of the lens and the optical magnification (b).   The macro inspection apparatus according to claim 1, wherein the optical system includes a knife edge for guiding the reflected light beam to the predetermined region.   The macro inspection apparatus according to claim 1, wherein an output of the line sensor according to the reflected light beam received in the predetermined area changes linearly with respect to a size variation of the uneven pattern. Image processing means for receiving an output signal of the line sensor and generating an image of a luminance distribution corresponding to a change in received light amount in the predetermined area of the line sensor;
Light source driving means for changing the angle of the diffused light source;
Line sensor driving means for changing the angle of the line sensor;
A moving means capable of moving the stage at a predetermined interval in order to inspect a size variation of the uneven pattern in a predetermined region of the surface of the inspection object;
The macro inspection apparatus according to claim 1, further comprising:

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