JP5636166B2 - Lighting device for surface inspection - Google Patents

Description

  The present invention relates to a wafer inspection illumination device for inspecting a substrate surface such as a semiconductor wafer for defects, dust, wrinkles and the like. In particular, the present invention relates to a lighting device for surface inspection suitable for inspecting the edge of a substrate such as a semiconductor wafer.

The outer peripheral portion (edge portion) of a semiconductor wafer may have defects such as chipping or cracking at the edge portion when the outer peripheral portion is chamfered or when handling the wafer for transporting or processing the wafer. . If these defects exist, wafer debris may enter the processing equipment during wafer polishing or when semiconductor chips or integrated circuits are formed on a semiconductor wafer, or these defects may cause semiconductor manufacturing. Fatal problems may occur in the process.
For example, if there are defects such as scratches, dents, cracks, etc. on the edge of the silicon wafer, when heat is applied to the silicon wafer during the heat treatment process, the semiconductor circuit of the silicon wafer is formed due to these defects. There is a risk that cracks may occur on the surface to be produced, resulting in a defective product. Moreover, a part of crack part may peel and may adhere to the process surface of a semiconductor wafer. Further, when particles are attached to the edge portion of the silicon wafer, the particles may be transferred and attached to the processed surface of the semiconductor wafer as the process proceeds.

  In order to prevent such problems from occurring, cracks and adhered particles generated on the mirror surface (processed surface) and edges of silicon wafers must be completely removed before proceeding to the next process, and strict inspection is performed. Is called.

  However, when the surface of the edge portion of the silicon wafer is minutely inspected, the edge portion is composed of several R (curved) portions, so that strict inspection is difficult.

  For this reason, several inspection methods have been proposed by the prior art. For example, in order to increase the inspection accuracy for defect detection even if dust or the like is present on the surface, the scattered light from the inspection object is detected by aligning the focal point inside the inspection object to increase the inspection accuracy of the defect. The inspection accuracy is improved by detecting minute irregularities on a three-dimensional surface or an irregular surface by illuminating the image pickup portion on the inspection object with a diffused light source in a band shape. The technique (patent document 2) to improve is proposed.

JP 2000-46537 A Japanese Patent No. 3709426

  However, in the conventional diffused (scattered) light illumination, even if the diffused light source is provided in a band shape, the illumination light spreads before reaching the inspection object, resulting in poor illumination efficiency. That is, in order to obtain sufficient illumination, if the illumination intensity from the light source is increased, the life of the illumination light source is shortened, and if the illumination intensity is weak, there is a problem that sufficient illumination cannot be performed. Accordingly, the present invention provides an illumination device for surface inspection that can efficiently illuminate a scanning region of an object to be inspected by securing a sufficient amount of light for illumination by condensing even a weak illumination light source. The purpose is to provide.

In order to solve the above problems, the illumination for surface inspection according to the first aspect of the present invention irradiates the surface of the edge portion of the substrate with illumination light and receives the reflected light, thereby receiving the edge portion of the substrate. In order to detect defects on the surface of the substrate, the inspection target portion is scanned by moving the substrate relative to the irradiation light irradiated on the inspection target portion at the edge portion of the substrate and its reflected light. In the inspection apparatus to be inspected, an illumination apparatus for illuminating the inspection target part,
A cross-section perpendicular to the scanning direction of the inspection target portion through which the edge portion of the substrate can rotate is passed, and the inspection target portion extends along the C shape of the concave portion. A light source block in which a plurality of light sources that output illumination light to be irradiated are arranged;
A cross section perpendicular to the scanning direction of the inspection target portion through which the edge portion of the substrate can rotate and pass is a C-shaped hollow portion, and between the light source through which the illumination light passes and the inspection target portion And a reflecting member having a reflecting surface in which a cross-sectional shape that reflects the illumination light output from the light source so as to be collected as parallel light on the inspection target portion of the substrate is a part of a parabola, and
With
The reflection surface of the reflection member is provided so that a cross-sectional shape including the scanning direction is a partial shape of a parabola along a C-shape of the hollow portion of the reflection member.
The recessed portion of the light source block and the recessed portion of the reflecting member are in the same recessed direction, and the irradiation light output from the light source of the light source block is reflected by the reflecting surface of the reflecting member. The light source block and the reflection member are arranged so as to reach the inspection target part as parallel light.

  Here, the illumination light includes not only the light directly radiated from the light source to the inspection target part, but also the light collected from the light source by the lens, the light irradiated through an optical fiber, and the light from the light source. Light that indirectly irradiates the inspection target part, such as light reflected by the reflecting surface, is also included.

When using a parallel light such as this as the irradiation light is hardly affected by the distance from the range light source is irradiated as compared with a case of using illumination light to a point condensing.

In this case, the light source is both multiple light source disposed blocks and the reflective member, the inspection inspection apparatus for an edge, such as a semi-conductor wafer has a shape to cover the edges of such C-shaped.

  According to the configuration of the present invention, the scattered light whose amount of light per unit area decreases as the distance increases is converted into parallel light by the reflecting member and irradiated, whereby the scattered light is efficiently used as irradiation light. It becomes possible. Even if the light amount of the light source is reduced, more accurate inspection is possible. When the light irradiated to the inspection target portion is constant, the life of the light source can be extended by suppressing the light amount of the light source.

It is a schematic diagram which shows the whole structure of the test | inspection apparatus concerning other embodiment using the illuminating device for test | inspection concerning one Embodiment of this invention. (A) is a perspective view which shows one Embodiment of the irradiation apparatus for test | inspection concerning this invention, (b) is a typical expanded sectional view for demonstrating the reflection of the irradiated light. (A) is a perspective view which shows other embodiment of the irradiation apparatus for test | inspection concerning this invention. (B) is a typical expanded sectional view for demonstrating the reflection of the irradiated light. (A) is a figure for demonstrating the position of the light source of the illuminating device for an inspection shown in FIG. 2, (b) is a figure for demonstrating the position of the light source of the illuminating device for an inspection shown in FIG. is there. (A) is a schematic diagram which shows the whole structure of the other test | inspection apparatus using the illuminating device for a test | inspection concerning one Embodiment of this invention. It is a perspective view which shows the use condition of the illuminating device for a test | inspection concerning other embodiment of this invention. (A) is a perspective view which shows one Embodiment of the light source block of the illumination device for an inspection shown in FIG. 6, (b) is another embodiment of the light source block of the illumination device for an inspection similarly shown in FIG. It is a perspective view shown. It is a conceptual diagram for demonstrating the inspection illuminating device when a part of ellipse is made into a reflective surface. It is a schematic diagram for demonstrating arrangement | positioning of an imaging means.

  Hereinafter, the basic concept of the present invention and preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram schematically showing an overall configuration of an inspection apparatus using an inspection illumination apparatus according to an embodiment of the present invention. 2A is a perspective view showing an inspection irradiation apparatus according to an embodiment of the present invention applicable to the inspection apparatus shown in FIG. 1, and FIG. 2B is an inspection illumination shown in FIG. It is a figure explaining the optical path of the irradiation light by an apparatus, and is an expanded sectional view of Fig.2 (a) AA 'direction.

As shown in FIG. 1, illumination light 90 is output from the inspection illumination device 10 and is irradiated onto a portion to be inspected (edge portion in FIG. 1) of a substrate (for example, a semiconductor wafer) 100. The irradiation light 90 is reflected by the edge of the substrate 100 to become reflected light 95 shown by a broken line, and is reflected by the reflecting plate 96 to the imaging means (CCD camera or line sensor) 97 connected to the image processing apparatus or the like. Irradiated. The reflected light 95 received by the image pickup means 97 is analyzed by an image processing device and inspected for the presence of scratches and other defects on the substrate.
In FIG. 1, the relationship between the irradiation light 90 and the reflected light 95 is shown in a simple manner for easy understanding, and the arrangement and shape of each of the constituent elements 10, 96, 97, 100, etc. are described later. Is different. In particular, the positional relationship between the inspection illumination device and the substrate in FIGS. 2 and 3 described later is different from that in FIG.

  With reference to FIG. 2, the structure and function of the test | inspection illumination apparatus 10 concerning one Embodiment of this invention are demonstrated. As shown in FIG. 2 (a), the inspection illumination device 10 has a structure in which a C-shaped light source block 11 and a reflection block 15 are provided adjacent to each other. The edge portion of the substrate 100 is configured to rotate and pass.

  In the light source block 11, a plurality of light sources 12 such as optical fibers are arranged along a C-shaped holding block. The reflective block 15 is provided with a primary reflective surface 16 along the light source 12 at a position facing the light source 12. The light source block 11 and the reflection block 15 are arranged with an interval between them, and the reflection member that reflects the illumination light reflected from the primary reflection surface 16 of the reflection block 15 again and irradiates the part to be inspected of the substrate 100 between them. 17 is arranged. The reflection member 17 includes a curved reflection surface, and irradiates the irradiation light from the primary reflection surface by converting it into parallel light. Accordingly, the irradiation light that is output from the diffuse light source and spreads and scatters as it moves away from the light source is collected as parallel light to prevent diffusion and efficiently irradiate the inspection region of the inspection object. .

  The optical path of irradiation light is demonstrated using FIG.2 (b). Irradiation light 91 output from the light source 12 is reflected by the primary reflecting surface 16 to become primary reflected light 92. The primary reflected light 92 is further reflected by the curved reflecting surface 18 of the reflecting member 17 to become parallel irradiation light 90, and is irradiated onto the edge portion of the substrate 100 that is the object to be inspected.

  The curved reflecting surface 18 of the reflecting member 17 that reflects the primary reflected light 92 from the primary reflecting surface 16 again into the parallel irradiation light 90 has a parabolic cross section. The light emitted from the focal point of the parabola is characterized in that when reflected by the reflecting surface on the parabola, it becomes light parallel to the axis direction of the parabola. Accordingly, the light source 12 is disposed at the focal position of the parabola that forms the curved surface of the reflecting surface 18. In the embodiment shown in FIG. 2, the irradiation light 91 from the light source 12 is applied to the reflection surface 18 through the primary reflection surface 16, so that the focal position of the parabola that constitutes the reflection surface 18 with the primary reflection surface 16 as the symmetry line. By arranging the light source 12 at a line symmetrical position, the reflected light of the irradiation light 91 by the reflecting surface 18 is irradiated to the edge portion of the substrate 100 as parallel light 90.

FIG. 3A is a perspective view showing an inspection illumination device 20 according to the second embodiment of the present invention, and FIG. 3B is a diagram for explaining the reflection of the irradiated light, and FIG. It is a typical expanded sectional view seen from the BB 'line direction of).
In the inspection illumination device 20 according to the second embodiment, the curved reflecting surface of the reflecting member 27 provided at a position facing the light source block 21 with the irradiation light 91 from the light source 22 provided in the light source block 21. 28 is directly irradiated. Since the reflecting surface 28 of the reflecting member 27 is a parabola and the light source 22 is disposed at the focal position of the parabola that constitutes the reflecting surface 28, the reflected light of the reflecting surface 28 is irradiated as a parallel irradiation light 90 of the substrate 100. The edge is irradiated.

The arrangement of the light sources 12 and 22 of the inspection illumination devices 10 and 20 shown in FIGS. 2 and 3 will be described with reference to FIGS. Now, assuming that the parabola constituting the reflecting surface is y = ax ² , the focal point position f of this parabola is f = 1 / 4a. Since the light incident parallel to the axis of the parabola y is collected at the focal point f, the light emitted from the focal point f is reflected in a direction parallel to the axis of the parabola y.

The inspection illumination device of the embodiment of FIG. 2 corresponds to a case where a reflection surface is inserted between the parabola y and the focal point f and a light source is arranged on the parabola side as shown in FIG. In this case, disposing the light source 12 at a position symmetrical with the focal point f with the reflecting surface 16 as a symmetrical line is the same as disposing the light source 12 at the focal point f.
The inspection illumination device of the embodiment of FIG. 3 has a configuration in which a light source 22 is disposed at the focal position of a parabola y as shown in FIG.
By arranging the light source in this way, the light output from the light source 12 or 22 and reflected by the parabolic reflection surface becomes parallel light traveling in a direction parallel to the axis of the parabola y.

FIG. 5 is a schematic diagram showing an overall configuration of an inspection apparatus using the inspection illumination device 30 according to another embodiment of the present invention. Also here, the positions of the light source and the reflection block are not accurately drawn in order to show the optical path for simplicity.
In the inspection illumination device 30 of this embodiment, the light source 32 and the reflection block 35 are separated. The light source 32 is located at a position away from the reflection block 35, and irradiation light 91 is applied to the reflection block 35 therefrom. The reflection block 35 reflects the irradiation light 91 to irradiate the substrate 100 with the illumination light 90 converted into parallel light. The reflected light 95 from the substrate 100 is input to the image pickup means 97 through the reflecting plate 96 and the like, and the presence of defects such as scratches on the substrate surface is analyzed.

  FIG. 6 is a perspective view showing an inspection illumination device 40 according to another embodiment of the present invention. The first to third embodiments 10, 20, and 40 of the present invention shown in FIGS. 2, 3, and 5 show examples of inspecting the edge portion of the substrate 100. FIG. In these embodiments, the reflection plate or the like extends in the scanning direction (a direction orthogonal to the rotation direction of the substrate) in a C shape so as to cover the edge portion that is the inspection target portion of the substrate 100.

  In the embodiment shown in FIG. 6, an example of the inspection illumination device 40 that inspects the substrate surface is shown. The inspection illumination device 40 has a rectangular parallelepiped shape, and extends on the surface of the substrate 100 in the diametrical direction so as to cover a direction orthogonal to the scanning direction of the substrate surface that is an inspection target portion. The inspection illumination device 40 includes a light source block 41 in which a plurality of light sources 42 are arranged in a line in the longitudinal direction, and a reflection block 47 having a reflecting surface 48 with a parabolic cross section. . The plurality of light sources 42 are disposed at the focal position of the parabola of the reflecting surface 48. In this way, by irradiating the substrate surface with parallel light and rotating the substrate, the substrate surface can be scanned and inspected.

  FIGS. 7A and 7B are perspective views showing examples of light source blocks applicable to the inspection illumination device 40 of FIG. In the light source block 41 of FIG. 7A, a plurality of light sources 42 made of optical fibers or light emitting diodes are arranged in a horizontal row. In FIG. 7B, a plurality of light sources 52, 53, and 54 aligned in a line in the light source block 51 are arranged in three vertical rows (rows). By arranging the light sources in a plurality of stages (rows) in this way, it is possible to obtain an illumination light source with a larger amount of light.

  FIG. 8 illustrates a case where a part of an elliptical shape is used as the reflecting surface of the lighting device according to the present invention. The ellipse 18 has two focal points g and h, and the light output from one focal point g and reflected by the inner surface of the ellipse 18 is collected at the other focal point h. Accordingly, the light source (scattered light source) 12 is disposed at one focal point g, and the inspection target (for example, the substrate 100) is disposed near the other focal point h, whereby the light from the light source is inspected on the substrate 100. Can be condensed.

  In the above description, an example in which an optical fiber or a light emitting diode is used as the light sources 12, 22, 32, 42, 52, 53, 54 has been shown. However, one or a plurality of light sources such as halogen lamps are used. It can also be used as a light source for output of illumination light.

  FIG. 9 is a schematic diagram illustrating an example of the arrangement of the imaging unit 97 with respect to the reflecting plate 96, and is a diagram illustrating a state viewed from the side surface of the substrate 100. In FIG. 9, three image pickup means 97 a, 97 b and 97 c are arranged above, on the side and below the substrate 100. Reference numerals 96a, 96b, and 96c denote reflecting plates corresponding to the respective imaging units 97a to 97c. Reference numerals 95a to 95c denote irradiation lights applied to the substrate 100, and reference numerals 95a to 95c denote reflected lights from the substrate 100, respectively.

  The imaging means 97 can be constituted by a sensor capable of acquiring an image such as a CCD camera or a line sensor. For example, the line sensor is a sensor array extending in a direction orthogonal to the traveling direction, and by measuring the length with this line sensor, connecting the length measurement data obtained in time series into an image, Detect scratches.

As shown in FIG. 9, the orientation of the image pickup means may be arranged so as to be shifted from the reflected light so as to have a predetermined angle, or may be arranged so as to receive the reflected light from the front and take an image. This differs depending on the inspection object and also differs depending on the way of imaging. By receiving the reflected light from the front, only the shadow of the wound can be raised. If an image is taken in a direction (for example, a position tilted by about 10 °) at a slight angle from the front with respect to the reflected light, an image in which only the edge of the scratch shines white can be obtained. In this way, it is possible to determine a scratch (including a defect or a foreign object).
Since the scattering state varies depending on the size of the scratch or foreign matter, the tilt angle can be changed according to the size of the scratch (defect or foreign matter) to be detected. Small scratches and foreign matter have unevenness in the scattering direction and may be strongly scattered in a specific direction. In order to detect such scratches and the like, as shown in FIG. 9, it is preferable that the image pickup means is inclined with respect to the irradiation direction, particularly in the scattering direction. This improves the detection efficiency of a specific size of scratches.

10, 20, 30, 40 Inspection illumination device according to the present invention
11, 21, light source block
12, 22, 32, 42, 52-54 Light source 15, 35 Reflection block 16 Primary reflection surface 17, 27, 47 Reflection member
18, 28, 48 Reflecting surface 90 Irradiation light 91, 92 Irradiation light (output light)
95 Reflected light (reflected light from the substrate)
97 Imaging means (CCD camera, line sensor, etc.)
100 substrate (wafer)
y: parabola, P: parabola axis, f: parabola focus

Claims (1)

In order to detect defects on the surface of the edge portion of the substrate by irradiating the surface of the edge portion of the substrate with illumination light and receiving the reflected light, the inspection target portion of the edge portion of the substrate is irradiated In an inspection apparatus that scans and inspects the inspection object part by moving the substrate relative to the irradiation light and the reflected light, the illumination apparatus illuminates the inspection object part,
A cross-section perpendicular to the scanning direction of the inspection target portion through which the edge portion of the substrate can rotate is passed, and the inspection target portion extends along the C shape of the concave portion. A light source block in which a plurality of light sources that output illumination light to be irradiated are arranged;
A cross section perpendicular to the scanning direction of the inspection target portion through which the edge portion of the substrate can rotate and pass is a C-shaped hollow portion, and between the light source through which the illumination light passes and the inspection target portion And a reflecting member having a reflecting surface in which a cross-sectional shape that reflects the illumination light output from the light source so as to be collected as parallel light on the inspection target portion of the substrate is a part of a parabola, and
With
The reflection surface of the reflection member is provided so that a cross-sectional shape including the scanning direction is a partial shape of a parabola along a C-shape of the hollow portion of the reflection member.
The recessed portion of the light source block and the recessed portion of the reflecting member are in the same recessed direction, and the irradiation light output from the light source of the light source block is reflected by the reflecting surface of the reflecting member. The illumination device for surface inspection is characterized in that the light source block and the reflecting member are arranged so as to reach the inspection object part as parallel light.

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