JP2006017743A - Surface inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain sufficient irradiation light intensity and inspection precision, and to enhance a through-put, in a surface inspection device. <P>SOLUTION: In this surface inspection device for detecting scattered reflected lights due to laser beams 2 to detect a foreign matter, by irradiating a substrate 5 surface with the laser beams, a light source part 12 has a plurality of light emitting sources, one image focusing lens, and an optical member provided in each of the light emitting sources to make the laser beam from the each light emitting source get incident into the image focusing lens, and an irradiation optical system is provided to widen a scanning pitch by inclining an optical axis for incidence from the light emitting source into the image focusing lens with respect to an optical axis of the image focusing lens, and by irradiating the substrate surface with the beams shifted along a direction to cross each other irradiation points of the laser beams emitted from the respective light emitting sources with respect to a scanning direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface inspection apparatus for inspecting fine foreign matters on a surface of a substrate such as a semiconductor wafer or fine flaws such as crystal defects.

  The surface inspection apparatus irradiates the surface of a substrate with a laser beam and detects scattered / reflected light caused by foreign matter and scratches to detect the foreign matter and scratches. In addition, gas lasers (He, Ar, etc.) have been used as light emission sources in surface inspection apparatuses, but recently, laser diodes (LDs) have been used for reasons of easy handling, safety, and long life. Yes.

  FIG. 14 shows a conventional irradiation optical system in which a laser diode is used as a light source.

  The laser beam 2 emitted from the light source 1 is converted into a parallel light beam by the collimating lens 3 and is formed on the surface of the substrate 5 such as a wafer (irradiation point 18 at the condensing position f by the imaging lens 4) by the imaging lens 4. Focused. The irradiation light intensity distribution at the irradiation point 18 is shown in FIG.

  When the entire surface of the substrate 5 is inspected, the irradiation point 18 is moved from the center to the outer edge at a predetermined speed in the radial direction while rotating the substrate 5. FIG. 15 shows the irradiation light intensity distribution of the laser beam 2 at the irradiation point 18, and shows a state in which the substrate 5 is rotated from the scanning position u to the scanning position u + 1. The speed in the radial direction in this case is a speed that moves p in the radial direction per one rotation of the substrate 5.

  The amount of scattered reflected light generated by a foreign object or scratch is affected by the intensity of the irradiated laser beam, and the detection accuracy of the foreign object or scratch is also affected by the intensity of the irradiated laser beam. Therefore, a predetermined irradiation light intensity I or higher is required to maintain a predetermined detection accuracy. The amount of movement p per rotation shown in FIG. 15 is determined so that the necessary irradiation light intensity I is maintained.

  The surface inspection of the substrate 5 is necessary for quality control of the product, but when the surface inspection process of the substrate 5 is incorporated in the manufacturing process, the inspection time required for the surface inspection affects the throughput.

  In the conventional example described above, when the irradiation light intensity of the laser beam is increased, the peak value of the irradiation light intensity distribution is also increased. When it is not required to increase the inspection accuracy, if the necessary irradiation light intensity is not changed, the amount of movement at one time, that is, the scanning pitch p increases, and the number of rotations required for scanning the entire surface of the substrate 5 decreases. Therefore, the surface inspection time is shortened.

  However, when a laser diode is used as the light source, the laser diode has various advantages such as easy, safe, and long life, but there is a problem that the amount of emitted light is smaller than that of a gas laser, etc. There was a limit. Further, since the detection accuracy is improved when the wavelength of the laser beam to be irradiated is shorter, it is desired to use a laser diode that emits a blue laser beam having a shorter wavelength. However, the blue laser diode has a problem that the amount of emitted light is smaller than that of a red laser diode and the like, and a sufficient amount of light required for the surface inspection apparatus cannot be obtained. In order to shorten the inspection time, it is desirable that the irradiation range on the substrate surface is wide. However, if the irradiation range is widened, there is a problem that both the detection sensitivity and the detection accuracy are lowered because the intensity of the irradiation light beam is reduced.

Japanese Patent Application Laid-Open No. 7-243988

JP-A-5-273142

JP-A-9-161304

  In view of such circumstances, the present invention maintains sufficient irradiation light intensity and inspection accuracy in a surface inspection apparatus, and further improves the throughput.

  The present invention relates to a surface inspection apparatus that detects a foreign object by irradiating a laser beam onto a substrate surface and detecting scattered light reflected by the laser beam. And an optical member that is provided corresponding to each light source and that makes a laser beam from the light source incident on the imaging lens. The optical axis that is incident on the imaging lens from the light source Increasing the scanning pitch by inclining the optical axis of the lens and irradiating the surface of the substrate as a light beam that shifts the irradiation point of the laser beam from each light source in a direction crossing the scanning direction. The present invention relates to a surface inspection apparatus provided with an irradiation optical system, and more particularly to a surface inspection apparatus provided with an optical axis tilting unit that tilts at least one optical axis on an optical axis incident on an imaging lens from the light emitting source. Also, the light source is a matrix. Those of the scan shape disposed surface inspection apparatus.

  According to the present invention, in a surface inspection apparatus that detects a foreign object by irradiating a laser beam onto a substrate surface and detecting scattered light reflected by the laser beam, the light source unit includes a plurality of light sources. And an optical member that is provided corresponding to each light source and that makes a laser beam from the light source incident on the imaging lens, and an optical axis that is incident on the imaging lens from the light source. Inclining with respect to the optical axis of the imaging lens, irradiating the surface of the substrate as a light beam that shifts the irradiation point of the laser beam from each light source in a direction intersecting the scanning direction, and setting the scanning pitch Since it has a large irradiation optical system, it has excellent effects such as widening the irradiation range with the predetermined light intensity while maintaining the predetermined irradiation light intensity, increasing the scanning pitch, and shortening the surface inspection time. Demonstrate.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  The outline of the surface inspection apparatus will be described with reference to FIG.

  In the figure, reference numeral 5 denotes a substrate which is an object to be inspected such as a wafer, and the surface inspection apparatus mainly includes a scanning drive mechanism unit 6, an irradiation optical system 7, and a detection system 8.

  The scanning drive mechanism unit 6 includes a substrate holding unit 9 that holds the substrate 5. The substrate holding unit 9 is rotatably supported by a rotation driving unit 10, and the rotation driving unit 10 is a linear driving mechanism unit. 11 is linearly moved in a radial direction parallel to the rotation surface of the substrate 5.

  The irradiation optical system 7 includes a light source unit 12 that emits a laser beam 2 as inspection light, deflecting optical members 13 and 14 such as mirrors that direct the laser beam 2 from the light source unit 12 onto the substrate 5, and the laser beam 2 The lens group 15 and the like are focused on the surface of the substrate 5. The detection system 8 includes light receiving detectors 16 and 17 having detection optical axes that intersect the optical axis of the laser beam 2 irradiated on the surface of the substrate 5.

  In the surface inspection of the substrate 5, the laser beam 2 is irradiated onto the surface of the substrate 5 from the irradiation optical system 7 in a state where the substrate 5 is rotated by the rotation driving unit 10, and the linear drive mechanism unit 11, the rotational drive unit 10 is moved in the radial direction.

  Thus, the irradiation point 18 of the laser beam 2 is concentric, by step-feeding at a required pitch for each rotation of the substrate 5, or by continuously feeding the rotary drive unit 10 at a predetermined speed. Moves from the center of the substrate 5 to the outer edge while drawing the locus of the spiral circle, and the entire surface of the substrate 5 is scanned by the laser beam 2.

  In the process where the laser beam 2 scans the surface of the substrate 5, the laser beam 2 is scattered and reflected if there is a foreign object or a flaw. The scattered reflected light is detected by the light receiving detectors 16 and 17 of the detection system 8 arranged at a predetermined position, and the signals from the light receiving detectors 16 and 17 are signal processed by an arithmetic processing unit (not shown). Foreign matter and scratches are detected.

  FIG. 2 shows an outline of the irradiation optical system 7 of the surface inspection apparatus of the present invention, in which the deflection optical members 13 and 14 are omitted.

  The light source section 12 has two sets of light emitting sources 1a and 1b, and laser beams 2a and 2b from the light emitting sources 1a and 1b are individually converted into parallel light beams by collimating lenses 3a and 3b, respectively, and one imaging lens. 4 is focused on the surface of the substrate 5. The optical axes of the collimating lenses 3a and 3b and the imaging lens 4 are basically parallel to each other, and the laser beams 2a and 2b emitted from the light emitting source 1a and the light emitting source 1b are used as the imaging lens. 4, the light is condensed at the same irradiation point 18.

  The light emission sources 1a and 1b can be controlled independently, and the intensity of irradiation light of the laser beams 2a and 2b emitted from the light emission sources 1a and 1b can be changed. Further, the laser beams 2a and 2b may have the same wavelength or different wavelengths. In a transmissive film or the like, the detection sensitivity is affected because the reflectance of the surface changes depending on the wavelength. By changing the wavelength, the influence on the wavelength of the reflection state on the surface of the substrate 5 is reduced.

  Next, FIG. 3 shows a case where the optical axis of the collimating lens 3 is tilted with respect to the optical axis of the imaging lens 4.

  When the optical axis of the collimating lens 3 is tilted with respect to the optical axis of the imaging lens 4, the irradiation point 18 moves. Therefore, when the optical axes of the collimating lenses 3a and 3b are inclined as shown in FIG. 4, the irradiation points 18a and 18b by the light emitting sources 1a and 1b are shifted.

  The irradiation light intensity distribution at the irradiation point 18 under the optical conditions shown in FIG. 4 is the combined irradiation light intensity distribution of the laser beams 2a and 2b in FIG. 5, and has a substantially trapezoidal shape as indicated by the solid line in the drawing. In this case, when the necessary irradiation light intensity is I and the scanning pitch is obtained, it becomes p 'in FIG. As a reference, the scanning pitch when a single laser beam is irradiated is indicated by p in the figure.

  The direction in which the laser beams are combined is a direction intersecting the scanning direction, preferably a direction perpendicular to the scanning direction, that is, the horizontal axis in FIG.

  Thus, since the range (width) having the predetermined irradiation light intensity at the irradiation point 18 is widened, the amount of movement in the radial direction for each rotation when scanning can be increased, and the substrate when scanning the entire surface. The number of rotations of 5 can be reduced, and the surface inspection time can be shortened with the detection sensitivity stabilized.

  The optical axis of the collimating lens 3 is inclined with respect to the optical axis of the imaging lens 4 so that the optical axis of the collimating lens 3 itself is inclined with respect to the optical axis of the imaging lens 4. However, the collimating lens 3 may be provided with an optical axis tilting means, and the optical axis tilting means may tilt the optical axis of the collimating lens 3 with respect to the optical axis of the imaging lens 4.

  As an optical axis tilting means for tilting the optical axis of the collimating lens 3, a wedge prism 19 is inserted on the optical axis of the collimating lens 3 as shown in FIG. . Further, the laser beam 2 emitted from the light source 1 may be guided to the imaging lens 4 by using a deflecting unit such as a mirror, and the deflecting unit may function as an optical axis tilting unit.

  FIG. 7 shows a second embodiment, in which a plurality of light emitting sources 1a and 1b and collimating lenses 3a and 3b are arranged on radiation centering on the optical axis of the imaging lens 4, and are reflected by reflecting mirrors 21a and 21b. The laser beams 2 a and 2 b are deflected so as to enter the imaging lens 4. In the configuration of the irradiation optical system shown in FIG. 7, the optical axes of the laser beams 2 a and 2 b are inclined with respect to the optical axis of the imaging lens 4 by inclining the reflecting mirrors 21 a and 21 b. Can do.

  FIG. 8 shows a third embodiment, in which a large number of light emitting sources 1a... 1n are arranged on a straight line, and each light emitting source is provided with a collimating lens 3a. The laser beams 2a... 2n are incident on one imaging lens 4 through 3a... 3n, and the optical axis of the collimating lenses 3a. The wedge prism 19 shown in FIG. 6 is provided for each optical axis, although not shown.

  When the optical axes of the collimating lenses 3a... 3n are gradually tilted away from the optical axis of the imaging lens 4, the irradiation points 18 are irradiated with the laser beams 2a. Are shifted in the radial direction of the substrate 5 (direction orthogonal to the scanning direction), and a flat trapezoidal irradiation light intensity distribution as shown in FIG. 9 is obtained. Accordingly, the scanning pitch can be further increased and the number of rotations of the substrate 5 required for the entire surface scanning is further reduced.

  In the above embodiment, the laser beams 2a and 2b are made incident on the same imaging lens 4, but in the fourth embodiment shown in FIG. 10, the laser beams 2a and 2b emitted from the light emitting sources 1a and 1b are used. Are collimated into parallel light beams by the collimating lenses 3a and 3b, and the laser beams 2a and 2b are deflected by the reflecting mirrors 21a and 21b, respectively, and are individually focused on the irradiation point 18 through the imaging lenses 4a and 4b. It is a thing.

  Even in such an irradiation optical system, the reflecting positions 21a and 18b of the laser beams 2a and 2b can be shifted in the radial direction of the substrate 5 by the reflecting mirrors 21a and 21b, and the irradiation light intensity distribution shown in FIG. Obtainable.

  Next, in the configuration of the irradiation optical system in FIG. 2, when the light beams of the laser beams 2a and 2b are made parallel to the optical axis of the imaging lens 4, as shown in FIG. As shown by the solid line in FIG. 11, the irradiation light intensity is approximately doubled. In the configuration of the irradiation optical system of FIG. 8, if all the optical axes of the laser beams 2a... 2n are parallel to the optical axis of the imaging lens 4, all the laser beams 2a. As shown in FIG. 12, the distribution of the irradiation light intensity at the irradiation point 18 is obtained by adding the irradiation light intensities of the laser beams 2a... 2n.

  Furthermore, although the case where the light emitting sources 1a... 1n are arranged in a line on the straight line has been described with reference to FIG.

  In the case of the matrix shape, although not shown in particular, the irradiation light intensity distribution at the irradiation point 18 can be adjusted as follows.

  That is, when the optical axis of the collimating lens 3a... 3n is gradually inclined for each column and the optical axis of the collimating lens 3b... 3m is parallel for each row, the flat trapezoidal irradiation light shown in FIG. Since the intensity distribution is obtained and the light amounts of all the columns are collected at the same position, the irradiation light intensity distribution shown in FIG. 9 is polymerized by the number of rows, and the irradiation light intensity distribution as shown in FIG. Thus, a laser beam 2 having a desired irradiation light intensity and a wide irradiation range can be obtained.

  Since the increase in irradiation light intensity can improve the inspection accuracy, in the case of the present embodiment, the inspection accuracy can be improved, and the throughput can be improved at the same time.

  In addition, by using a plurality of light emitting sources 1 and deflecting the optical axis of the laser beam 2 by the optical axis tilting means, it is possible to obtain an arbitrary irradiation light intensity distribution or the shape of the light beam at the irradiation point.

  Thus, it is possible to obtain irradiation conditions according to the surface inspection situation, such as whether to give priority to throughput or to improve accuracy.

1 is a skeleton diagram showing a basic configuration of a surface inspection apparatus according to an embodiment of the present invention. It is explanatory drawing of the irradiation optical system of this surface inspection apparatus. It is explanatory drawing at the time of inclining an optical axis about the irradiation optical system in embodiment of this invention. It is explanatory drawing at the time of inclining an optical axis about the irradiation optical system in embodiment of this invention. It is a diagram which shows the irradiation light intensity distribution in the irradiation point in this irradiation optical system. It is explanatory drawing of the optical axis inclination means in this irradiation optical system. It is explanatory drawing of the irradiation optical system of the 2nd Embodiment of this invention. It is explanatory drawing of the irradiation optical system of the 3rd Embodiment of this invention. It is a diagram which shows the irradiation light intensity distribution in the irradiation point of the irradiation optical system of this 3rd Embodiment. It is explanatory drawing of the irradiation optical system of the 4th Embodiment of this invention. It is a diagram which shows the irradiation light intensity distribution in the irradiation point at the time of making an optical axis parallel about the irradiation optical system shown in FIG. It is a diagram which shows the irradiation light intensity distribution in the irradiation point at the time of making an optical axis parallel about the irradiation optical system shown in FIG. It is a diagram which shows the irradiation light intensity distribution in the irradiation point obtained by arrange | positioning a light emission source in matrix form. It is explanatory drawing which shows the irradiation optical system of the conventional surface inspection apparatus. It is a figure which shows the relationship between the irradiation light intensity and the scanning pitch in the surface inspection apparatus of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Laser beam 5 Substrate 6 Scanning drive mechanism part 7 Irradiation optical system 8 Detection system 12 Light source part 15 Lens group 18 Irradiation point 19 Wedge prism 21 Reflection mirror

Claims (3)

  In a surface inspection apparatus that detects a foreign object by irradiating a laser beam onto a substrate surface and detecting scattered light reflected by the laser beam, the light source section includes a plurality of light sources and a single imaging lens. An optical member that is provided corresponding to each light source and that makes a laser beam from the light source incident on the imaging lens; and an optical axis that is incident on the imaging lens from the light source is an optical axis of the imaging lens An irradiation optical system that irradiates the surface of the substrate as a light beam that shifts the irradiation point of the laser beam from each of the light emitting sources in a direction crossing the scanning direction, and increases the scanning pitch. A surface inspection apparatus characterized by comprising.   The surface inspection apparatus according to claim 1, further comprising an optical axis tilting unit configured to tilt at least one optical axis on an optical axis incident on the imaging lens from the light emitting source.   The surface inspection apparatus according to claim 1, wherein the light emitting sources are arranged in a matrix.

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