Reticle inspection apparatus and projection aligner

Abstract

To inhibit or prevent a non-inspectable range when inspecting a foreign matter of a rectangular reticle.SOLUTION: A reticle inspection apparatus includes: an illumination part that irradiates light to a rectangular reticle; an imaging part that images the reticle; and an inspection part that inspects a foreign matter by inspecting an imaged image. The illumination part employs a whole area of an inspection surface for the reticle as a light irradiation range, and the imaging part employs the whole area of the inspection surface as a range of vision.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a reticle inspection apparatus and a projection exposure apparatus equipped with a reticle inspection apparatus. [Background technology]

[0002] Projection exposure equipment uses ultraviolet light to project and transfer the reticle pattern onto the substrate, but if there is a foreign object on the reticle, the image of the foreign object will also be transferred to the substrate, causing defects such as circuit breaks. For this reason, it is common to optically inspect the reticle for foreign objects such as dust before the exposure process. Reticle inspection is automated and is performed using a camera and image processing technology.

[0003] In order to shorten the reticle inspection time, it is desirable to image the entire reticle and inspect it all at once, unlike a method of scanning the reticle with spot light or line light. For example, Patent Document 1 discloses an embodiment capable of simultaneously inspecting both sides of a mask (reticle) substrate. Patent Document 1 describes that the front and back sides of a mask M supported only by its peripheral edge are photographed by television cameras 23 and 24, respectively, and the photographed images are displayed by television receivers 31 and 32, making it possible to simultaneously observe the front and back sides. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 58-154229 Summary of the Invention [Problem to be solved by the invention]

[0005] When the entire reticle is illuminated in order to image the entire reticle, scattered light occurs at the reticle edge. Since the scattered light at the reticle edge is stronger than the light scattered by foreign objects, when the scattered light enters the camera, halation occurs along the reticle edge. Due to the halation, there is a problem that foreign object inspection cannot be performed near the reticle edge. To avoid the effects of scattered light, it is possible to install a light-shielding member in front of the television camera, but this method requires strict alignment between the reticle edge and the television camera. Furthermore, since the light-shielding member cannot be installed at the focal position of the television camera, the light-shielding part is out of focus, which creates the problem that inspection near the edge is not possible.

[0006] Therefore, an object of the present invention is to provide a reticle inspection apparatus that is capable of illuminating the entire surface of a reticle having an edge and that can prevent the vicinity of the edge of the reticle from becoming impossible to inspect, and a projection exposure apparatus equipped with a reticle inspection apparatus. [Means for solving the problem]

[0007] The present invention provides a reticle inspection apparatus in which an illumination unit irradiates a rectangular reticle with light, an imaging unit images the reticle, and an inspection unit inspects the image to detect foreign objects, comprising: The illumination unit illuminates the entire inspection surface of the reticle. The imaging unit has a field of view covering the entire surface to be inspected. This is a reticle inspection apparatus in which the inspection unit inspects the image of the entire surface of the inspection surface. The present invention also provides a method for manufacturing a photolithography system comprising: a reticle stage for mounting a rectangular reticle thereon; a projection unit for projecting exposure light transmitted through the reticle onto a substrate; and a reticle inspection unit for inspecting the reticle, The reticle inspection unit is a reticle inspection unit according to any one of claims 1 to 7, This is a projection exposure apparatus in which the reticle is inspected in a reticle inspection section, and then the reticle is placed on the reticle stage and the exposure process is started. Effect of the Invention

[0008] According to at least one embodiment, the entire surface of the reticle can be inspected at once, and it is possible to prevent the vicinity of the reticle edge portion from becoming uninspectable due to halation. Note that the effects described herein are not necessarily limited to those described herein, and may be any of the effects described in this specification or effects different from those effects. [Brief description of the drawings]

[0009] [Figure 1] 1A and 1B are a plan view and a side view that show a schematic overall configuration of an exposure apparatus. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a reticle. [Diagram 3] FIG. 3 is a perspective view of one embodiment of a reticle inspection apparatus. [Figure 4] FIG. 4 is a perspective view of a reticle and a light source holding unit provided in the reticle inspection device. [Diagram 5] 5A and 5B are schematic diagrams for explaining the optical positional relationship between a light source and a reticle in one embodiment. [Figure 6] FIG. 6 is a flowchart for explaining the operation of the exposure apparatus. [Figure 7] FIG. 7 is a flowchart for explaining the operation of the reticle inspection apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are preferred specific examples of the present invention, and the content of the present invention is not limited to these embodiments.

[0011] 1A and 1B are a schematic plan view and a side view showing an entire exposure apparatus, and Fig. 1A is a plan view looking downward from line AA in Fig. 1B. The present invention is applied to a reticle inspection apparatus 21 in Fig. 1A and Fig. 1B.

[0012] The exposure apparatus main body is equipped with a light source / illumination optical system 11 that irradiates (illuminates) the reticle with exposure light emitted from a light source, a reticle stage 12 that supports the reticle and positions it, a projection optical system 13 that projects the light that has passed through the reticle onto a substrate, and a substrate stage 14 on which the substrate is placed and which positions the substrate. The substrate is a semiconductor silicon wafer, a printed wiring board, etc. These components are mounted on a stand 15 by a frame (not shown).

[0013] A transfer robot 22 that transfers reticles and substrates is installed adjacent to the exposure apparatus body. A reticle inspection device 21, a reticle cassette 23, and a substrate cassette 24 are installed around the transfer robot 22. The exterior of the exposure apparatus is provided so as to contain all of the above-mentioned components. The exterior is an air-conditioned chamber equipped with a temperature and humidity adjustment unit (not shown).

[0014] 2 shows an example of a reticle R. The reticle R has a pattern surface PT in which a metallic reflective film such as chrome is formed on a rectangular plate-shaped quartz glass 31 substrate, and light-transmitting portions are provided in the reflective film so that light can pass through in the shape of the pattern to be exposed. The pattern surface PT is made to coincide with the focal point of the projection lens.

[0015] In order to prevent foreign matter from adhering to the pattern surface PT, a pellicle PE is installed via a spacer 32. The pellicle PE is a thin transparent film. The pellicle PE is installed at a distance of several mm from the pattern surface PT. Even if there is a foreign matter at a position away from the pattern surface PT, it will not be focused on the substrate and will not be considered a defect. However, if a relatively large foreign matter adheres to the pellicle PE, it will affect the exposure, so not only foreign matter on the glass surface PG of the quartz glass 31 but also foreign matter on the pellicle PE is inspected.

[0016] The light source / illumination optical system 11 of the exposure apparatus body has a light source (such as an LED light source or a mercury lamp) and a light amount equalizing means such as a fly-eye lens that equalizes the light from the light source. The reticle is uniformly illuminated by the light from the light source / illumination optical system 11.

[0017] The reticle stage 12 includes a reticle table on which the reticle is placed, and a movement mechanism for moving the reticle table in the x, y, and θ directions. The reticle table has an opening that allows the light that has passed through the reticle to pass through the projection optical system. The projection optical system 13 is a projection lens that projects the light that has passed through the reticle onto the surface of the substrate.

[0018] The substrate stage 14 includes a substrate table on which a substrate is placed, and a movement mechanism for moving the substrate table in the x, y, and θ directions. The substrate stage 14 may include lift pins and the like for transferring the substrate to and from a transfer robot.

[0019] The reticle cassette 23 is a cassette that stores multiple reticles with pellicles installed. The exposure tool selects and uses one reticle that matches the exposure conditions from the multiple stored reticles according to a recipe (production process information).

[0020] The substrate cassette 24 is a cassette that stores a plurality of substrates before and after exposure. A plurality of substrate cassettes 24 may be installed to store the substrates before and after exposure in separate cassettes. The substrate cassette 24 is transported to the exposure device by an AVG (Automatic Guided Vehicle: an unmanned autonomous transport robot) or the like. Note that, without providing a substrate cassette, substrates before exposure may be sequentially carried in from an upstream device to the exposure device and exposed substrates may be sequentially carried out to a downstream device by a conveyor or the like.

[0021] The transport robot 22 includes a substrate robot that transports substrates between the substrate cassette 24 and the substrate stage 14, and a reticle robot that transports reticles between the reticle cassette 23, the reticle inspection device 21, and the reticle stage 12. A known SCARA robot or the like can be used as the transport robot 22.

[0022] An example of a reticle inspection apparatus 21 will be described with reference to Fig. 3. In this reticle inspection apparatus 21, an upper frame 42 is attached onto a lower frame 41. The lower frame 41 and the upper frame 42 are configured in a box shape with prismatic members connected to each side, and each side of the box shape is open.

[0023] A pellicle surface imaging device 43 is attached to the lower frame 41, and a glass surface imaging device 44 is attached to the upper frame 42. The pellicle surface imaging device 43 and the glass surface imaging device 44 each have an imaging section, for example a camera, and an inspection section 49 for processing the camera's image signal to inspect for the presence or absence of foreign matter. The camera is perpendicular to the inspection surface and is disposed on a central axis that passes through the center of the reticle. The camera's field of view covers the entire inspection surface.

[0024] A reticle and light source holding unit 45 is provided on the upper part of lower frame 41 adjacent to upper frame 42. As shown in Fig. 4, reticle and light source holding unit 45 includes an opening into which rectangular reticle R is set by a transfer robot, a support part 46 provided below this opening for supporting the periphery of reticle R from below so as not to touch the pellicle PE, and a light source support part 47 arranged outside the opening. For example, the transfer robot has a hand on which the reticle can be placed and carried in order to hand over the reticle.

[0025] An illumination unit consisting of a total of eight light sources 48 is attached to the light source support part 47 on the front and back of the reticle R. The light sources 48 are arranged in positions on the extension of the diagonal line of the reticle R, close to and away from the corners. The light sources 46 irradiate diffuse light from the four corners towards the center of the reticle, and the reticle R is set in the opening by the hand of the transfer robot. The light sources 48 are LED light sources that emit wavelengths to which the camera is sensitive, such as orange light of 600 nm or green light of 550 nm.

[0026] The illumination unit consisting of light sources 48 irradiates illumination light from the vicinity of the corners of the reticle R toward the center, illuminating the entire surface of the reticle R. Four light sources 48 are provided to illuminate the glass surface (top surface in FIG. 4) of the reticle R, and four light sources 48 are provided to illuminate the pellicle surface (bottom surface in FIG. 4) of the reticle R. Uniform illumination light can be formed by the four light sources 48 provided near each corner of the reticle R.

[0027] Figures 5A and 5B are schematic diagrams showing the optical positional relationship between the light source 48 and the reticle R. Figure 5A shows the optical positional relationship of one embodiment of the present invention, and Figure 5B explains the occurrence of scattered light at the edge of the reticle in a conventional reticle inspection device. Note that only one light source 48 out of four light sources that illuminate the glass surface PG is shown, and the light source 48 that illuminates the pellicle PE is not shown, and the pellicle PE is also not shown.

[0028] The diffused light generated by the light source 48 is incident obliquely in the x direction at a small angle of incidence, assuming that the glass surface PG is the xy plane and the plane perpendicular to the xy plane is the xz plane. The angle of incidence is set to an angle at which total reflection occurs (for example, 5°). This prevents images unnecessary for inspection, such as an image of the pattern surface of the reticle R, from being captured. Foreign matter adhering to the glass surface PG generates scattered light, and therefore appears as a high-luminance image in the captured image, making it possible to detect it. The optical relationship between the light source 48 and the pellicle PE is the same as the optical relationship between the light source 48 and the glass surface PG.

[0029] As described above, when the inspection surface of reticle R (glass surface PG and pellicle PE) is illuminated at a shallow angle and the camera is positioned vertically away from the center of the pellicle surface, if there is no foreign object, no illumination light enters the camera's field of view, resulting in a black screen. If there is a foreign object, some of the light diffusely reflected by the foreign object reaches the camera, and an image of the foreign object's white reflection appears on a black background. This camera image is processed by inspection unit 49 to determine the presence and position of a foreign object, and if a foreign object is detected, an alert is issued.

[0030] Unlike one embodiment of the present invention, when reticle R is illuminated at a shallow angle of incidence by a linear LED light source parallel to one side of the reticle R, halation occurs in the image captured by the camera near the edge of the side farthest from the incident side of the reticle. In the area where halation occurs, there is an area that cannot be inspected for foreign objects, and there is a problem that it is impossible to inspect for the presence or absence of foreign objects. One embodiment of the present invention suppresses such halation.

[0031] As shown in Fig. 5B, in the xy plane, when the optical axis of light source 48 is nearly perpendicular to the side surface of the edge of reticle R on the incident side, light enters the inside of the reticle from the side of reticle R and reaches the side surface of the edge opposite the incident surface due to internal reflection. Part of the illumination light passes through the side surface as is, while the other part is reflected by the inner surface of the side surface, and the reflected light is emitted from the chamfered portion and observed as scattered light from the reticle edge. This scattered light causes halation.

[0032] In one embodiment of the present invention, the optical axis of the light source 48 is inclined with respect to the side surface of the reticle R in the xy plane. That is, since the illumination light is incident from the corner of the reticle R, most of the light is reflected by the side surface of the reticle R, and the amount of light propagating inside the reticle R is reduced. As a result, scattered light is less likely to occur at the edge of the reticle R, halation is suppressed, and it is possible to prevent the vicinity of the edge of the reticle from becoming an uninspectable area.

[0033] The operation of the exposure apparatus shown in FIG. 1 will be described with reference to the flow chart of FIG. Step S1: Load a recipe and select a reticle. Step S 2 : The transfer robot 22 takes out the reticle from the reticle cassette 23 , and sets the reticle in the reticle inspection device 21 . Step S3: The reticle inspection device 21 inspects the glass surface and the pellicle surface of the reticle. If a foreign object is detected by the inspection, the operator is notified and the process is interrupted.

[0034] Step S 4 : If no foreign matter is detected on the reticle, the transfer robot 22 removes the reticle from the reticle inspection device 21 and sets it on the reticle stage 12 . Step S5: The transfer robot 22 removes the substrate from the substrate cassette 24 and places it on the substrate stage 14. Step S6: The exposure apparatus main body exposes the substrate. Step S7: The transfer robot 22 removes the substrate from the substrate stage 14 and stores it in the substrate cassette 24.

[0035] Step S8: It is determined whether or not it is the rod end. If it is not the rod end, the process returns to step S5 (the substrate is placed on the substrate stage 14). Step S9: If it is determined in step S8 that the rod end has occurred, the transfer robot 22 removes the reticle from the reticle stage 12 and stores it in the reticle cassette 23, and the process ends.

[0036] The above-mentioned processes from step S1 to step S4 are processes related to the reticle inspection apparatus 21. An example of the process of this reticle inspection apparatus 21 will be described with reference to the flowchart of FIG.

[0037] Step S11: The hand of the transfer robot inserts the reticle into the side opening above the reticle and light source holding portion 45 (simply referred to as the reticle support portion in FIG. 7) of the reticle inspection device 21. Step S12: The hand of the transfer robot 22 descends, and the reticle is placed on the reticle support. Step S13: The hand of the transfer robot 22 retreats from the reticle support portion. The processes in steps S11, S12 and S13 correspond to step S2 in FIG. 6 (setting the reticle in the reticle inspection apparatus).

[0038] Step S14: The light source 48 for illuminating the reticle of the reticle inspection device 21 is turned on. Step S15: The glass surface and the pellicle surface are imaged by the camera.

[0039] Step S16: The light source 48 (reticle illumination) of the reticle inspection device 21 is turned off. Step S17: The inspection unit 49 acquires the image captured by the camera. Step S18: The inspection unit 49 processes the image to determine whether or not there is a foreign object, and if there is a foreign object, obtains information about the position of the foreign object. Step S19: If a foreign object is present, the inspection unit 49 notifies the operator.

[0040] Step S20: The hand of the transfer robot 22 moves forward and stops at a position below the reticle. Step S21: The hand of the transfer robot 22 rises and receives the reticle from the reticle support (the reticle is placed on the hand). Step S 22 : The transfer robot 22 removes the reticle from the reticle inspection device 21 and transfers it to the reticle stage 12 . The process of step S22 corresponds to step S4 in FIG. 6 (taking out the reticle from reticle inspection apparatus 21 and setting the reticle on reticle stage 12).

[0041] As described above, the exposure apparatus inspects the reticle using reticle inspection apparatus 21 as a preliminary step to the exposure process, and places the inspected reticle directly on reticle stage 12. Then, a substrate is placed on substrate stage 14, and the exposure operation of the substrate is repeated for a determined number of substrates (e.g., one lot). When the exposure process is completed, the reticle is removed from reticle stage 12 and stored in reticle cassette 23.

[0042] Although one embodiment of the present technology has been specifically described above, the present invention is not limited to the above-mentioned embodiment, and various modifications based on the technical idea of ​​the present invention are possible. For example, the present invention is also applicable to the inspection of a reticle that does not have a pellicle. The present invention is also applicable to a laser processing device. Moreover, the configurations, methods, processes, shapes, materials, and values ​​given in the above-mentioned embodiment are merely examples, and configurations, methods, processes, shapes, materials, and values ​​different from these may be used as necessary. [Explanation of symbols]

[0043] R... reticle, PG... glass surface, PE... pellicle, 11... light source and illumination optical system, 12... reticle stage, 14... substrate stage, 21... reticle inspection device, 22... transfer robot, 23... reticle cassette, R... reticle, 43... pellicle surface imaging device, 44... glass surface imaging device, 45... reticle and light source holding section, 48... light source

Claims

1. A reticle inspection apparatus including an illumination unit that irradiates a rectangular reticle with light, an imaging unit that images the reticle, and an inspection unit that detects foreign objects by inspecting the captured image, the illumination unit illuminates the entire inspection surface of the reticle with light; The imaging unit has a field of view covering the entire surface of the inspection surface. Reticle inspection equipment.

2. The illumination unit and the imaging unit are located in a positional relationship such that no area in which foreign matter cannot be inspected is generated due to scattered light generated at a reticle edge when the inspection unit inspects an image of the entire surface of the inspection surface.

2. The reticle inspection apparatus according to claim 1.

3. 2. The reticle inspection apparatus according to claim 1, wherein the illumination unit has a light source that is disposed near a corner of the reticle and that irradiates diffuse light toward a center of the reticle.

4. 4. The reticle inspection apparatus according to claim 3, wherein the light sources of said illumination unit are installed in the vicinity of all corners of said reticle and illuminate the entire inspection surface from four directions.

5. 2. The reticle inspection apparatus according to claim 1, wherein the imaging unit is disposed on a central axis that is perpendicular to the inspection surface and passes through a center of the reticle.

6. 2. The reticle inspection apparatus according to claim 1, wherein another illumination unit irradiates an opposing surface of said reticle opposite to said inspection surface with illumination light, another imaging unit images said opposing surface, and an inspection unit inspects the image thus captured.

7. A pellicle is provided at a distance from the opposing surface; 7. The reticle inspection apparatus according to claim 6, wherein the other illumination unit irradiates the pellicle with illumination light, the other imaging unit images the pellicle, and an inspection unit inspects the image thus captured.

8. The apparatus includes a reticle stage on which a rectangular reticle is placed, a projection unit that projects exposure light that has passed through the reticle onto a substrate, and a reticle inspection unit that inspects the reticle, The reticle inspection unit is a reticle inspection unit according to any one of claims 1 to 7, A projection exposure apparatus in which the reticle is placed on the reticle stage after inspection by the reticle inspection unit and an exposure process is started.

Images