JP5648874B2 - Macro inspection device - Google Patents

Description

  The present invention relates to a macro inspection apparatus for inspecting a film thickness unevenness of a photoresist film forming a surface of a reticle substrate.

  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.

  A reticle is a photomask used to expose a highly integrated electric circuit pattern on a wafer in a semiconductor device manufacturing process. The reticle is created, for example, by drawing a circuit pattern directly on the photoresist forming the surface of the reticle substrate with an electron beam or the like.

  If the thickness of the photoresist film on the reticle substrate is uneven (variation, non-uniformity), there is a possibility that a defect is created in the circuit pattern after drawing. Therefore, it is necessary to inspect the unevenness of the film thickness of the photoresist forming the surface of the reticle substrate over the entire reticle substrate and grasp the distribution of the uneven film thickness as accurately as possible.

  Japanese Patent Application Publication No. 2009-139333 discloses a macro inspection apparatus that inspects the flatness (variation) of the surface of a reticle substrate. This macro inspection apparatus inspects the flatness of the surface of the reticle substrate by receiving the reflected light from the edge of the light irradiation region on the surface of the reticle substrate with a line sensor.

JP 2009-139333 A

  The macro inspection apparatus of Patent Document 1 is an effective apparatus in that, in a bright field optical system, detection sensitivity is improved by using reflected light from an edge of a light irradiation region with high directivity. However, in order to detect minute film thickness unevenness such as photoresist film thickness unevenness on the reticle substrate, further improvement in detection sensitivity is required.

  Accordingly, an object of the present invention is to provide a macro inspection apparatus capable of detecting the film thickness unevenness of the photoresist on the reticle substrate and its distribution with high sensitivity.

  The present invention provides a macro inspection apparatus for inspecting a film thickness unevenness of a photoresist film forming a surface of a reticle substrate. The macro inspection apparatus includes a stage for placing a reticle substrate, a line light source for irradiating the reticle substrate with light from a first angle direction with respect to the surface of the reticle substrate, and a first surface with respect to the surface of the reticle substrate. And a line sensor that receives reflected light from the surface of the reticle substrate from two angular directions. The second angle is such that when the line sensor is moved in a predetermined step within a predetermined angle range including the second angle, the mapping of the line light source reflected on the surface of the reticle substrate is the center of the surface of the reticle substrate. It is set as the angle when it is located in the part.

  According to the present invention, the angle of the line sensor that receives the reflected light from the surface of the reticle substrate is the angle when the mapping of the line light source that is reflected on the surface of the reticle substrate is located at the center of the surface of the reticle substrate. By setting, it is possible to receive more reflected light from the surface of the photoresist film, and to detect film thickness unevenness of the photoresist film with high sensitivity.

  In one aspect of the present invention, an image processing unit that receives an output signal of a line sensor and generates an image of a luminance distribution corresponding to a change in the amount of received light in the predetermined area of the line sensor, and an angle of the line light source A light source driving means, a line sensor driving means for changing the angle of the line sensor, and a movement capable of moving the stage at a predetermined interval in order to inspect film thickness unevenness in a predetermined area on the surface of the reticle substrate. Means.

  According to one embodiment of the present invention, the distribution of film thickness unevenness of a photoresist film in a predetermined region on the surface of a reticle substrate can be quickly grasped visually as an image.

It is a figure which shows the macro inspection apparatus of one Embodiment of this invention. It is a figure which shows the position (angle) of the line light source and line sensor of one Embodiment of this invention. It is explanatory drawing of the angle setting of the line sensor of one Embodiment of this invention. It is a figure which shows the test | inspection flow of this invention by one Example of this invention. It is a figure which shows the macro test | inspection 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, a reticle substrate 2 to be inspected is placed on a circular stage 1. The stage 1 is moved in the direction of rotation (α), horizontal (X) or vertical (Y) by the linear motor 3 under the control of the stage controller 4. The line light source 5 is moved along the arc-shaped rail 6 by the stepping motor 7 under the control of the controller 8. The line light source 5 is set at a predetermined angle with respect to the upper surface of the reticle substrate 2 on the stage 1. The predetermined angle can be arbitrarily set according to the measurement state. The brightness of the line light source 5 is adjusted by a power source 10 for the light source.

  Similarly to the line 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 the reflected light from the surface of the reticle substrate to the line sensor 9 is provided at the front portion of the line sensor camera 9. The optical system 12 may be provided between the reticle substrate 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 line light source 5. In FIG. 1, only one line light source 5 and one line sensor camera 9 are shown, but two or more line light sources 5 and line sensor cameras 9 may be arranged according to the size and shape of the reticle substrate. 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. The stage 1 desirably has a surface that is as flat as possible. The stage 1 preferably has a structure in which reflected light from other than the surface of the reticle substrate 2 is hardly generated.

As the reticle substrate 2 to be inspected, a reticle substrate having an arbitrary configuration (layer structure) can be selected as long as a photoresist film before patterning (exposure and development) is basically formed on the surface. it can. For example, a light shielding metal layer such as Cr or CrO ₂ and a photoresist layer formed on a glass substrate such as quartz, a multilayered light shielding metal layer, or a light shielding metal layer not including W or Mo. This corresponds to a case where only a photoresist layer made of an inorganic resist such as an oxide is formed on a glass substrate.

  The size of the reticle substrate 2 is set according to the specifications of the stepper used, for example, a 6-inch square size is used. The photoresist film is formed by spin-coating a liquid photoresist on the glass substrate so as to have a uniform thickness over the entire surface of the glass substrate. At this time, since the liquid photoresist is made of a polymer material, a slight difference in film thickness (variation) occurs depending on the position on the substrate in the photoresist film after spin coating. This is mainly caused by a slight misalignment when a liquid resist is discharged to the center of the substrate during spin coating. Or, depending on the stability of the viscosity of the liquid resist itself, the discharge amount, the substrate surface condition, etc., the way in which the discharged liquid resist spreads from the central part to the outer peripheral part is slightly different. . Therefore, it is difficult to form a photoresist film having a completely uniform thickness over the entire surface of the glass substrate, and a small variation in film thickness is locally formed in an arbitrary region on the surface of the glass substrate. .

  The line light source 5 includes a light emission source on the line and an optical system (lens, diffusion plate, etc.) for obtaining a diffusion effect thereon. In the line light source 5, for example, a plurality of light emitting elements are arranged in a line at a predetermined pitch L1 on a long substrate. The size of the substrate can be arbitrarily selected, and is, for example, 15 mm × 700 mm. The pitch L1 can be arbitrarily selected according to the size of the light emitting element. 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. The line light source 5 is set at a predetermined distance (for example, 40 to 45 cm) from the surface of the stage 1.

  An optical system (a lens, a diffusion plate, etc.) for obtaining a diffusion effect such as a diffusion plate 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 made according to the state of the reticle substrate (resist material, optical characteristics, etc.) and the optical characteristics (wavelength characteristics, etc.) of the line sensor camera 9 and the optical system. In the case of measuring a photoresist film that forms the surface layer of the reticle substrate 2, for example, blue-based visible light having a relatively short wavelength region is used.

  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 reticle substrate 2. If the reticle substrate 2 is large and cannot be covered by one line sensor camera 9, two or more line sensor cameras are used. The line sensor camera 9 is set at a predetermined distance (for example, 85 to 90 cm) from the surface of the stage 1.

  The line light source 5 and the line sensor camera 9 can vary the angle with respect to the surface of the reticle substrate 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 is configured such that reflected light from the surface of the reticle substrate 2 is received on the entire surface of the line sensor 9 or on a predetermined region. 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 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 showing positions (angles) of the line light source 5 and the line sensor camera 9 according to the embodiment of the present invention in the macro inspection apparatus 100 of FIG. FIG. 3 is a diagram for explaining a method of setting the angles of the line light source 5 and the line sensor camera 9 according to the embodiment of the present invention in the macro inspection apparatus 100 of FIG. As shown in FIG. 2, the angle referred to here means an angle θ <b> 1 of the line light source 5 with respect to the surface of the reticle substrate 2 on the stage 1 in FIG. 1 and an angle θ <b> 2 of the line sensor camera 9.

  In FIG. 3A, reference numeral 20 is a view of a circular wafer as viewed from above, and reference numeral 22 represents an image of the line light source 5 reflected on a plane including the surface of the wafer 20. Here, the wafer 20 is used as a member having a mirror surface, and may be another member such as a mirror as long as it has a mirror surface. Reference numeral 24 in FIG. 3B is a graph (line) showing the relationship between the angle θ2 of the line sensor camera 9 and the sensitivity (light reception amount).

  Now, in the macro inspection apparatus 100 of FIG. 1, the angle θ2 of the line sensor camera 9 is set to a predetermined angle with the line light source 5 that illuminates the plane including the surface of the wafer 20 of FIG. The range is varied by a predetermined step (angular displacement). Here, for example, the angle θ1 is approximately 63 degrees, the predetermined range is approximately 80 to 87 degrees, and the predetermined step (angular displacement) is an angle that is the predetermined minimum control angle Δθ unit described above or a multiple thereof. (NΔθ). The predetermined range of the angle θ2 and the angle θ1 are set according to the measurement object.

  As the line sensor camera 9 moves, the image 22 of the line light source 5 reflected on the plane including the surface of the wafer 20 moves in the direction indicated by the arrow A from the position P0 in FIG. The position P0 corresponds to a case where the angle θ2 is 80 degrees, for example. At the position P0, since the image 22 of the line light source 5 is not reflected on the surface (mirror surface) of the wafer 20, the sensitivity (light receiving amount) of the line sensor camera 9 is low, and is indicated by P0 in FIG. Indicates the sensitivity of the area. When the line sensor camera 9 is moved and the image 22 of the line light source 5 comes to the position P1, that is, when it reaches the center (center) of the wafer 20, the surface of the wafer 20 of the image 22 of the line light source 5 The amount (area) reflected in (mirror surface) is maximized.

  At this time, the graph 24 showing the sensitivity (light reception amount) of the line sensor camera 9 in FIG. 3B shows the maximum sensitivity S1 indicated by P1. In the present invention, the angle θ2m of the line sensor camera 9 when the maximum sensitivity S1 is shown is set as an angle for measuring the surface of the reticle substrate 2 on the stage 1 in the macro inspection apparatus 100 of FIG. In one embodiment, the angle θ2m is approximately 84 degrees. When the line sensor camera 9 is further moved, the amount (area) of the image 22 of the line light source 5 reflected on the surface (mirror surface) of the wafer 20 gradually decreases, as shown in the graph 24 of FIG. Sensitivity decreases.

  As described above, in the present invention, the position (angle) of the line light source is set first, and then the position of the image of the line light source reflected on the predetermined surface (mirror surface) is confirmed (detected), and the line sensor camera This is characterized in that the line sensor camera is set at the position (angle) when the sensitivity (the amount of received light) becomes the maximum. That is, instead of simply monitoring the sensitivity (light reception amount) of the line sensor camera and selecting the angle that maximizes the amount, the position of the image of the line light source is confirmed (detected) so that it can be detected from other than the inspection target. The feature is that the angle at which the amount of reflected light from the surface of the inspection object is maximized is detected and set while eliminating the increase in the amount of light received due to the light as much as possible. Note that the position of the image of the line light source reflected on the predetermined surface (mirror surface) is confirmed (detected) by placing the camera above the predetermined surface (mirror surface) and displaying the image of the line light source as an image. Or by visual observation or a combination of both.

  Next, an inspection flow for the film thickness unevenness of the photoresist film forming the surface of the reticle substrate of the present invention will be described. FIG. 4 is a diagram showing an inspection flow of the present invention. The flow of FIG. 4 is executed by the macro inspection apparatus 100 according to the embodiment of FIG.

  In step S11, the angles of the line light source 5 and the line sensor camera 9 already described above are set. In step S12, the reticle substrate 2 to be inspected is prepared on the stage 1, and the line sensor is detected for each predetermined region of the surface (photoresist film) of the reticle substrate 2 while moving the stage 1 in a predetermined step. The amount of reflected light (average luminance) is measured by the camera 9.

  In step S13, the average luminance data for each predetermined region of the surface of the reticle substrate 2 (photoresist film) obtained in step S12 is subjected to image processing, and the surface of the reticle substrate 2 (photoresist film) is processed. The luminance map is created by obtaining the entire area (or the designated area). The luminance map includes information such as average luminance and standard deviation of average luminance for each predetermined area. The standard deviation is calculated at the time of measuring the average luminance in step S12 or at the time of calibration of the average luminance that is performed as necessary at that time. In step S14, the obtained luminance map is displayed on the display device as an image.

  As an example of the present invention, FIG. 5 shows an image of a luminance map obtained by measuring the surface (photoresist film) of the reticle substrate 2. In the image of FIG. 5, enhancement processing such as light and dark is performed. The angle θ1 of the line light source 5 at the time of measurement is 63 degrees, and the angle θ2 of the line sensor camera 9 is 84 degrees. The line light source 5 is set at a position 40 cm away from the surface of the stage 1, and the line sensor camera 9 is set at a position 87 cm away from the stage 1 surface (more precisely, WD = 868 mm). In the image of FIG. 5, it can be seen that film thickness unevenness (variation) occurs in a spiral or convex region.

  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 Reticle Board 3 Linear Motor 4, 8 Controller 5 Line Light Source 6 Rail 7 Stepping Motor 9 Line Sensor Camera
10 Power source for line light source 11 Image processing device
100 Macro inspection equipment

Claims (6)

A macro inspection apparatus for inspecting a film thickness unevenness of a photoresist film forming a surface of a reticle substrate,
A stage for placing the reticle substrate;
A line light source for irradiating light to the reticle substrate from a first angular direction with respect to the surface of the reticle substrate;
A line sensor that receives reflected light from the surface of the reticle substrate from a second angle direction with respect to the surface of the reticle substrate;
When the line sensor is moved in a predetermined step within a predetermined angle range including the second angle, the mapping of the line light source reflected on the surface of the reticle substrate is the second angle. A macro inspection apparatus which is set as an angle when located at the center of the surface of the surface of the surface and is an angle at which the amount of reflected light received by the line sensor is maximized . The first angle is approximately 63 degrees, the second angle is approximately 84 degrees, macro inspection apparatus according to claim 1. The line light source comprises a plurality of LED arranged in a row, the output of each LED is adjusted to be uniform, macro inspection apparatus according to claim 1 or 2. The macro inspection apparatus according to claim 1, wherein the line sensor is a CCD or CMOS line sensor. Substrate The reticle includes a multilayer film for preventing stray light on the glass substrate, made of the photoresist on the multi-layer film, macro inspection apparatus according to any one of claims 1 to 4. 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 line light source;
Line sensor driving means for changing the angle of the line sensor;
A moving means capable of moving the stage at predetermined intervals in order to inspect the film thickness unevenness in a predetermined region of the surface of the reticle substrate;
Further comprising, macro inspection apparatus of any one of claims 1 to 5..

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