JP6570084B2 - Macro inspection device for inspecting the upper surface of protrusions on the stage surface - Google Patents

Description

  The present invention relates to a macro inspection apparatus, and more specifically to a macro inspection apparatus that inspects the upper surfaces of a plurality of protrusions arranged on the surface of a stage on which a substrate is placed.

  One of inspections performed in the manufacturing process of semiconductors, liquid crystals, etc. is a macro inspection. Macro inspection means that the surface condition (flatness, unevenness, pattern shape, presence / absence of defects, etc.) of the film provided on the substrate can be visually recognized at once in a wide area including the entire substrate. It is an effective inspection.

  As the degree of integration of circuit patterns formed on a semiconductor wafer such as silicon (hereinafter simply referred to as a wafer) increases, warping and deflection of the wafer as a substrate are obstacles to further miniaturization of the circuit pattern. become. In the semiconductor manufacturing process, when a circuit pattern or the like is formed on the surface of a wafer, each process such as film formation is performed while the wafer is placed on a stage made of metal, ceramics, etc., and on that stage, The wafer needs to be firmly fixed and the flatness of the wafer surface must be ensured.

  In order to prevent the back surface of the wafer from coming into direct contact with the surface of the stage when the wafer is detachably mounted on the stage, it is usually arranged on the front surface of the stage. Projections such as prisms and cylinders are provided. As an example, the protrusion is a quadrangular prism with a side of about 200 μm. When the wafer is placed on the stage, the back surface of the wafer is in contact with the top surface of the protrusion (square column). A gap of about 200 μm is formed between them.

  If there is foreign matter such as dust on the upper surface of the projection on the stage, the wafer may crack or sometimes crack when the wafer is placed and fixed on the stage by electrostatic chucking or vacuuming. In addition, at least the flatness of the wafer surface is impaired. For example, in a wafer having a large diameter of 300 mm, the influence on the yield due to this problem becomes large. In addition, in the development (three-dimensionalization) of semiconductor substrates (wafers) that are being developed in recent years, each of a plurality of wafers after circuit formation is thinned and then laminated (bonded) on the stage. . In this case, since the thickness of each wafer is only about several tens of μm, cracks or the like are likely to occur, and since the circuit is formed, the adverse effect on the yield and the like becomes particularly serious.

When the wafer is first placed on the stage, the stage surface is cleaned / cleaned, but as the semiconductor manufacturing process progresses, various thin films formed on the wafer surface in each process separate from the edge of the wafer. May adhere to the stage surface. In that case, if it is possible to quickly inspect macroscopically whether the adhered matter (dust) that has detached in the middle of the process is on the upper surface of the projection, the stage surface can be cleaned more efficiently and efficiently. It becomes possible.

  Patent Document 1 (Japanese Patent No. 4792314) discloses a substrate inspection apparatus that performs a macro inspection on a defect of a substrate 1 levitated on a levitation holder 2 using a line illumination unit 3 (illumination unit) and a line sensor camera 6. However, this substrate inspection apparatus in Patent Document 1 inspects the surface of a semiconductor wafer or a liquid crystal substrate, and does not inspect the upper surface of a relatively fine protrusion on the stage, and such a fine protrusion. It is not possible to inspect the top surface of objects.

Japanese Patent No. 4792314

  An object of the present invention is to inspect the upper surface of a protrusion regularly provided on a stage on which a substrate such as a wafer is mounted at a macro speed at a high speed with a relatively simple and compact configuration in a manufacturing process of a semiconductor or the like. It is to provide a macro inspection apparatus capable of performing the above.

  Provided is a macro inspection apparatus for inspecting upper surfaces of a plurality of protrusions arranged on a surface of a stage on which a substrate is placed. The macro inspection apparatus is located obliquely upward in the range of 5 to 40 degrees from the surface of the stage, and obliquely in the range of 40 to 60 degrees from the surface of the stage and the line light source that irradiates the surface of the stage and the projections with light. Positioned above, the work distance (WD) is in the range of 9-20 mm, the line sensor camera that receives the reflected light from the surface of the stage and the projection, and the signal from the line sensor camera, the projection And a processing device for detecting the presence or absence of foreign matter on the upper surface of the substrate. The line light source and the line sensor camera are arranged at a position where adverse effects on the inspection of the upper surface of the protrusion due to halation caused by reflected light from other than the upper surface of the protrusion can be suppressed.

  According to the present invention, foreign matters such as dust on the upper surface of the protrusion while suppressing the adverse effect on the inspection of the upper surface of the protrusion due to halation caused by reflected light (scattered light) from other than the upper surface of the protrusion on the stage. It is possible to inspect at high speed in-line with a relatively simple and space-saving configuration over the entire stage.

It is a figure which shows the structure of the macro inspection apparatus of one Embodiment of this invention. It is a figure which shows a part of test | inspection area | region of one Embodiment of this invention. It is a figure which shows the line light source of one Embodiment of this invention. It is a figure which shows the line light source of other one Embodiment of this invention. It is (a) sectional drawing and (b) bottom view which show the line camera of one Embodiment of this invention. It is a figure for demonstrating the mode of the reflected light in the protrusion and its vicinity of one Embodiment of this invention. It is a figure which shows the test | inspection flow of the protrusion surface of one Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the following description, a case where a stage for mounting a semiconductor wafer is used as a stage to be measured will be described. However, other substrates can be used as long as they have uneven portions such as relatively fine protrusions on the surface. The present invention can also be applied to a stage on which (for example, a thin plate material such as glass or metal) is placed.

  FIG. 1 is a diagram showing a macro inspection apparatus 100 according to an embodiment of the present invention. In FIG. 1, a semiconductor wafer or the like is later placed on a circular stage 1 which is an object to be inspected according to the present invention. The stage 1 may have not only a circular shape but also any other planar shape such as a square, a rectangle, and an ellipse. The stage 1 can be moved in the direction of rotation (α), horizontal (X) or vertical (Y) by the linear motor 2 under the control of the stage controller 3 on a support base (not shown).

  The line camera 5 is supported by a distance variable mechanism (not shown) and is disposed above the stage 1. The line camera 5 is arranged so as to receive reflected light from the surface of the stage 1 at a predetermined angle. As the predetermined angle, an arbitrary angle in the range of 40 to 60 degrees can be selected. As the line camera 5, for example, a contact image sensor (CIS) camera having a shallow depth of focus can be used. In this case, the CIS camera preferably has a relatively short work distance (WD), for example, a WD of about 9 to 20 mm, more preferably about 9 to 11 mm. In the macro inspection apparatus 100 according to the embodiment of the present invention, the line camera 5 (for example, CIS camera) having a relatively short work distance (WD) is used at an angle with respect to the surface of the stage 1 as described above. It is one feature. As a result, the size (arrangement) of the entire inspection apparatus can be kept small.

  The line light source 7 is supported by a distance variable mechanism (not shown) and is disposed above the stage 1. The line light source 7 is arranged so that the surface can be irradiated with light at an angle with respect to the surface of the stage 1 from above. As the predetermined angle, for example, an arbitrary angle in the range of 5 to 40 degrees, more preferably in the range of 5 to 20 degrees, for example, can be selected. The line light source 7 is set to be positioned at a predetermined distance from the optical axis of the line camera 5 on the surface of the stage 1. As the predetermined distance, for example, an arbitrary distance in the range of 100 to 300 mm can be selected. The brightness of the line light source 7 is adjusted by a power source 6 for the light source.

  The output of the line camera 5 is input to the processing device 4 for detecting the presence or absence of foreign matter on the upper surface of the projection on the surface of the stage 1. The processing device 4 can control the power supply 6 for the stage controller 3, the line camera 5, and the line light source 7. In FIG. 1, only one line light source 7 and one line camera 5 are shown, but two or more lines can be arranged at different positions. The above is the outline of FIG. Next, details of each component of FIG. 1 will be further described.

  FIG. 2 is an enlarged view (a) of a region A, which is a part of the inspection region on the surface of the stage 1 in FIG. 1, and a sectional view (b) showing a CC cross section thereof. In area A, it is a figure showing a part of inspection field of one embodiment of the present invention. Region A in FIG. 2 includes a plurality (12) of protrusions 10 regularly arranged on the surface of the stage 1. The protrusion 10 is a cylinder having a length that is substantially the same as the diameter and height of the upper bottom surface. The length is about several hundred μm (for example, about 200 μm). The plurality of protrusions 10 are arranged in a plurality of regions on the surface of the stage 1. The shape of the protrusion 10 is not limited to a cylinder, and an arbitrary shape having a flat upper surface and a height of a predetermined size such as a quadrangular prism and a mountain shape having a trapezoidal cross section can be selected. The size is not limited to about 200 μm.

  As described above, when the wafer is placed on the stage 1, the plurality of protrusions 10 come into contact with the upper surface 11 of the protrusion 10 so that a predetermined distance ( For example, a gap of about 200 μm is formed. Due to the presence of the protrusions, the back surface of the wafer can be prevented from coming into direct contact with the surface of the stage when the wafer is detachably mounted on the stage. Although not shown, the stage 1 is configured to be able to fix the wafer, for example, a jig provided on the surface that can restrain the outer periphery of the wafer 3 and 4 points from the outside to the inside. / Mechanism (clip part, chuck, etc.) can also be provided. The macro inspection apparatus 100 according to an embodiment of the present invention detects the presence or absence of foreign matter such as dust on the upper surface 11 of the plurality of protrusions 10.

  As a wafer to be mounted on the stage 1 to be inspected, any thin film pattern (circuit or wiring (semiconductor, conductor, insulator, etc.)) is basically formed on the surface by a conventional semiconductor process. A wafer having a configuration (layer structure) can be selected. The wafer can include either a state in which a number of IC chips before dicing are formed in a lattice shape, or a state in which the above-described various patterns are formed at an intermediate stage. The wafer can be made of any material such as, for example, Si alone, SOI, SiGe, or a compound semiconductor such as GaAs. As the wafer size (bore diameter), for example, an arbitrary size such as 200 mm or 300 mm can be used. In addition, the wafer can have a thickness of about several hundreds of μm or about several tens of μm for stacking (three-dimensional). The top surface 11 of the projection 10 of the stage 1 to be inspected according to the present invention may adhere to dust (thin film material or the like) that falls from the wafer (particularly the end portion) placed on the top surface 11. The macro inspection apparatus 100 according to the embodiment also detects the presence / absence of dust (foreign matter).

  FIG. 3 is a diagram showing a line light source 70 according to an embodiment of the present invention. (A) is a top view of the external shape of the line light source, (b) is a top view of the light emitting source section, and (c) is a cross-sectional view. As shown in the top view of (b), in the line light source 70, for example, a plurality of light emitting elements 72 are arranged in a line at a predetermined pitch L1 on a long substrate. The size of the substrate can be arbitrarily selected, but the length in the longitudinal direction needs to be at least approximately the same as or longer than the length in the longitudinal direction of the line camera 5. The pitch L1 can be arbitrarily selected according to the size of the light emitting element 72 and the like.

  In the cross-sectional view of FIG. 3C, the line light source 70 can include a light emitting source 72 on the line and an optical system (lens, diffuser plate, etc.) 74 for obtaining a diffusion effect thereon. The light emitting element can be basically arbitrarily selected from not only semiconductor elements such as currently available light emitting diodes (LEDs) and laser diodes (LD) but also light emitting elements newly appearing in the future.

  An optical system (lens, diffusing plate, etc.) 74 for obtaining a diffusing effect such as a diffusing plate is installed integrally with the light emitting source as shown in FIG. can do. A wide wavelength or a predetermined wavelength band can be selected as the wavelength of the light emitting source 72. The selection is performed according to the state of the stage 1 and the optical characteristics (wavelength characteristics, etc.) of the line camera 5 and the optical system.

  FIG. 4 is a diagram showing a line light source 80 according to another embodiment of the present invention. (A) is sectional drawing of a line light source, (b) is a bottom view. As shown in the sectional view of (a), the line light source 80 includes a light-emitting element 82 and an optical fiber bundle 86 for guiding the light from the light-emitting element 82 to a predetermined width via an optical system (lens) 84. And an optical system (lens, for example, a cylindrical lens) 88 for condensing the light from the optical fiber bundle 86 into a predetermined elongated (linear) range. The length of the line light source 80 and the optical system (lens) 88 in the bottom view of the line light source 80 in FIG. 4B can be set equal to or less than the size (width) of the stage to be measured. The light emitting element 82 may be, for example, one relatively large (high power) light emitting diode (LED). A wide wavelength or a predetermined wavelength band can be selected as the wavelength of the light emitting source 72. The selection is performed according to the surface state of the stage 1, the optical characteristics (wavelength characteristics, etc.) of the line camera 5 and the optical system. The line light source 80 of FIG. 4 has one feature in that one light emitting element 82 and an optical fiber bundle 86 are used in combination.

  FIG. 5 is a diagram showing a line camera 50 according to an embodiment of the present invention. (A) is sectional drawing of a line camera, (b) is a bottom view. The line camera 50 includes a light receiving unit 52 and a lens 54 for guiding light to the light receiving unit 52. The light receiving unit 52 may be anything that can acquire an image for each dimension by arranging light receiving elements (pixels) in a line. For the light receiving part 52, for example, a one-dimensional CCD image sensor or a CMOS image sensor can be used. The number of pixels is selected according to the size of the stage 1 to be inspected. For example, a pixel size of 43 μm × 86 μm can be used.

  The lens 54 is a cylindrical lens generally called a rod lens, a cell hook lens, or a GRIN lens having a refractive index distribution with a secondary distribution in the radial direction (hereinafter referred to as a rod lens). In the rod lens, since the light incident from the lens end face travels while drawing a sine curve, an equal-magnification erect image can be obtained by setting an appropriate lens length. The plurality of rod lenses are arranged in a row (one-dimensionally) along the light receiving unit 52 in the longitudinal direction of the line camera 50. FIG. 5B shows the bottom surface of one rod lens 54 that is continuous as an assembly of a plurality of rod lenses. The reflected light received by the lower end portion of each rod lens exits from the upper end portion and is condensed on each corresponding light receiving element (pixel).

  The processing device 4 in FIG. 1 processes a detection signal (luminance information) received from the line camera 5 based on a predetermined measurement program. The processing device 4 controls the controller 3 and the illumination power supply 6. The processing device 4 includes a card (circuit board) for controlling the line camera 5, a controller 3, a circuit board for controlling the illumination power supply 6, a memory for storing image data, and the like. The processing device 4 corresponds to, for example, a personal computer (PC) having a display unit that displays image processing results and the like, and an input unit that inputs measurement conditions and the like.

  Next, the detection principle of the foreign matter on the protrusion 10 by the macro inspection apparatus 100 according to the embodiment of the present invention will be described with reference to FIG. FIG. 6 is a view for explaining the cylindrical projection 10 according to the embodiment of the present invention and the state of reflected light in the vicinity thereof. (A) shows a state in which light is incident from the upper left line light source 7 with fine beads (balls) 20 assuming dust attached to the upper surface 11 of the protrusion 10. Incident light is incident on the stage surface in front of the protrusion 10 and the left and upper surfaces 11 of the protrusion 10 as exemplified by light rays a, b, and c. The line light source 7 is placed at a relatively low angle (in the range of 5 to 40 degrees described above) with respect to the stage surface so that it does not directly enter the right side surface of the protrusion 10 and the nearby stage surface.

  Incident light from the line light source 7 is reflected from each incident surface. For example, incident light rays a, b, and c are reflected upward as reflected light indicated by Ra, Rb, Rc1, and Rc. Of these, Rc1 assumes reflection from the surface of the bead 20. FIG. 5B shows an image of light shadow (shadow) in the state of FIG. A region 21 on the left side of the bead 10 indicates a region in which the reflected light is further reflected and becomes scattered light. A region 22 on the right side of the bead 10 indicates a dark shadow region that is behind the protrusion 10 and does not receive scattered light.

In the present invention, since it is necessary to detect the reflected light from the upper surface 11 of the protrusion 10, the scattered light region 21 of (b) does not cover (cover) the upper surface of the protrusion, in other words, the protrusion The line light source 7 and the line are arranged so that the top surface of the protrusion cannot be inspected due to halation (becomes white and blurred) caused by reflected light (scattered light, stray light) from other than the top surface 11 of the object 10. It is necessary to set the arrangement of the sensor 5. The arrangement conditions are the ranges of the following parameters already described above.
Line sensor angle: 40-60 degrees (WD: 9-20 mm)
-Angle of line light source: 5 to 40 degrees, distance from optical axis: 100 to 300 mm

  Next, a macro inspection flow according to an embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram showing a macro inspection flow according to an embodiment of the present invention. The flow of FIG. 7 is executed by the inspection apparatus 100 of the embodiment of FIG.

  In step S11, the stage 1 to be measured is set on a support base (not shown). As already described, the stage 1 can include a stage having a plurality of protrusions 10 on the surface. In step S12, the line light source 7 and the line camera 5 are set at predetermined positions on the stage 1. Each placement to be set is performed according to the placement conditions described above. In step S <b> 13, light is irradiated from the line light source 7 to the inspection area on the surface of the stage 1. As the inspection area, a predetermined area including the projection 10 of the stage 1 is selected.

  In step S <b> 14, the line camera 5 receives reflected light from the surface of the stage 1 (including the upper surface of the protrusion 10). The reflected light is received in units of pixels of the line camera 5 and sent to the processing device 4 as luminance values in units of pixels. The processing device 4 stores the brightness value data in the memory. In step S15, the above-described steps S13 and S14 are repeated while changing the measurement area by moving the stage 1, and the luminance value data corresponding to the reflected light in each measurement area is acquired.

  In step S <b> 16, the processing device 4 detects the presence or absence of foreign matter on the upper surface of the protrusion 10 on the stage 1 from the acquired luminance value data, and creates a luminance distribution (macro image) of a part or the whole of the measurement region. The presence / absence of a foreign object is detected by comparing the luminance value of each pixel with a predetermined threshold value obtained in advance, and detecting the presence / absence of a foreign object from the magnitude relationship, the difference amount, and the like. For example, when the luminance value is larger than the threshold value, there can be no foreign matter, and when the luminance value is small, there can be foreign matter. In the determination of the magnitude relationship, it is possible to set a condition such that the determination (determination of presence / absence) is performed when the difference value from the threshold value is equal to or greater than a predetermined value. The predetermined threshold value is, for example, a comparison between an average luminance value measured by attaching a foreign object in advance to the upper surface of the protrusion of the stage 1 and an average luminance value measured by measuring the upper surface of the cleaned protrusion without foreign material. Can be set from

The presence or absence of spherical particles aggregated by spraying polystyrene latex (PSL) on the surface of a metal stage and the upper surface of protrusions on the stage using the macro inspection apparatus 100 having the configuration shown in FIG. Whether or not can be detected was examined. The measurement conditions at that time are as follows.
(1) Protrusions: cylindrical shape with an upper surface diameter of about 200 μm
(2) PSL spherical particles: the average diameter is about 20 μm
(3) Line light source: The line light source of the type shown in FIG. 4 is arranged at an angle of about 10 degrees from the stage surface, and the distance from the optical axis of the line sensor is about 200 mm.
(4) Line camera: CIS camera, WD is 9.9 mm, pixel size is 43 μm × 86 μm, resolution including rod lens is 89 μm

  It was confirmed by a CCD camera and a microscope that spherical particles of PSL adhered to two of the ten protrusions and did not adhere to the remaining eight. Next, as a result of inspecting the area including the ten protrusions with the macro inspection apparatus, there are spherical particles on the upper surface of the two protrusions and no spherical particles on the upper surface of the eight protrusions. Could be detected. This result means that according to the macro inspection apparatus of the present invention, foreign matter (PSL particles) having a size of about 20 μm can be detected with a line camera having a resolution of 89 μm.

  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.

1 Stage 2 Linear motor 3 Stage controller 4 Processing unit (PC)
5, 50 Line camera 6 Power source for light source 7, 70, 80 Line light source 10 Projection 11 Top surface 20 of projection
21 Bright area with scattered light 22 Dark shadow area where scattered light does not enter 52 Light receiving element 54 Lens 74 Optical system (lens, diffuser plate, etc.)
82 Light Emitting Element 84 Optical System (Lens)
86 Optical fiber bundle 88 Optical system (lens)
100 Macro inspection equipment

Claims (5)

A macro inspection apparatus for inspecting the upper surfaces of a plurality of protrusions arranged on the surface of a stage on which a substrate is placed,
A line light source that is located obliquely above in the range of 5 to 40 degrees from the surface of the stage, and that irradiates light on the surface of the stage and the protrusions;
A line sensor camera that is positioned obliquely above in the range of 40 to 60 degrees from the surface of the stage, has a work distance (WD) in the range of 9 to 20 mm, and receives reflected light from the surfaces of the stage and the projections When,
A processing device for processing a signal from the line sensor camera and detecting the presence or absence of foreign matter on the upper surface of the protrusion,
The line light source is located at a distance in the range of 100 to 300 mm from the optical axis of the line sensor camera on the surface of the stage ,
The angle from the surface of the stage of the line light source and the line sensor camera has an adverse effect on the inspection of the upper surface of the protrusion due to halation caused by reflected light from other than the upper surface of the protrusion within the respective ranges. Macro inspection device set to an angle that can suppress   The macro inspection apparatus according to claim 1, wherein the line sensor camera is a contact image sensor (CIS) camera including a rod lens that guides the reflected light to a line sensor.   The macro inspection apparatus according to claim 1, wherein the line light source includes a light emitting element and an optical fiber bundle for spreading light from the light emitting element to a predetermined width.   The processing device obtains a luminance value for each pixel of the line sensor from a signal from the line sensor camera and compares the luminance value with a predetermined threshold value to detect the presence or absence of foreign matter on the upper surface of the protrusion. The macro inspection apparatus as described in any one of Claims 1-3. It further comprises moving means capable of moving the stage at a predetermined interval,
The processing device receives a signal from a line sensor obtained while the stage moves, and generates an image of a luminance distribution on the surface of the stage and the upper surface of the protrusion from the luminance value for each pixel of the line sensor. The macro inspection apparatus according to claim 4.

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