Patent Publication Number: US-2021185282-A1

Title: Substrate imaging apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/680,894, filed Nov. 12, 2019, which is a continuation of U.S. application Ser. No. 15/437,869, filed Feb. 21, 2017, now U.S. Pat. No. 10,523,905, issued Dec. 31, 2019, and claims the benefit of Japanese Patent Application No. 2016-031361, filed Feb. 22, 2016, the entireties of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a substrate imaging apparatus. 
     BACKGROUND OF THE INVENTION 
     At present, a photolithography technique is widely used to form a pattern (patterned projections/recesses) on a substrate in fine processing of substrates. For example, a process for forming a resist pattern on a semiconductor wafer includes forming a resist film on a surface of the wafer, exposing the resist film with a predetermined pattern, and allowing the exposed resist film to be reacted with a developer to develop the exposed resist film. 
     In recent years, a liquid immersion exposure technique has been proposed as a technique for obtaining a very fine resist pattern of about 40 nm to 45 nm in line width. When a resist film is subjected to a liquid immersion exposure, the resist film is exposed while an exposure liquid (e.g., deionized water or the like), which has a refractive index higher than that of air, is supplied to a space between a wafer and a projection lens for exposure. 
     In the course of processing the wafer surface, small particles (foreign matters) may adhere to the wafer surface (its central portion or peripheral portion) for various reasons. Most particles can be removed by cleaning the substrate surface with a cleaning liquid, but some particles may remain on the substrate surface. When a wafer having particles adhered thereto is loaded into an exposure device, the exposure device is contaminated. In this case, when a succeeding wafer is exposed, a particle shape as well as a desired pattern may be transferred. In addition, when the exposure device is contaminated with particles, it may take a long time to clean the exposure device, which seriously lowers productivity. Moreover, if a wafer has some defect in the vicinity of its periphery (for example, flaw, crack, scratch, etc.) the wafer cannot be properly processed. Thus, Patent Document 1 (JP2007-251143A), Patent Document 2 (JP2008-135583A) and Patent Document 3 (JP11-339042A) each disclose a wafer inspection method including a step of taking images of a peripheral portion of a wafer by means of a plurality of cameras, a step of processing the images, and a step of judging the condition of the peripheral portion of the wafer based on the processed images. 
     However, in order to inspect surfaces (e.g., upper surface and end face) near the periphery of a wafer, the checking method of Patent Documents 1 to 3 takes images the surfaces individually, with the use of the plurality of cameras. Thus, since a large space for installation of these cameras is needed, the wafer inspection apparatus may have a larger size as well as an increased cost of the apparatus. 
     It is conceivable that the plurality of surfaces near the peripheral portion of the wafer are inspected by moving one camera. However, since a space for installation of a mechanism for moving the camera is needed, the apparatus may have a larger size after all. In addition, since the moving speed of the camera is not so high, it takes a long time to inspect the wafer. 
     Further, if a plurality of cameras are used, a mechanism for assembling the cameras is needed in addition to these cameras, which complicates the structure. Also if one camera is moved, a mechanism for moving the camera is needed in addition to the camera, which complicates the structure. Thus, in the inspection method of Patent Documents 1 to 3, a malfunction of the equipment is more likely to occur, and there is a possibility that the inspection could not be efficiently performed. 
     SUMMARY OF THE INVENTION 
     The disclosure describes a substrate imaging apparatus achieving reduction in size and decrease in cost, while avoiding equipment failure. 
     A substrate imaging apparatus according to one aspect of the disclosure comprises: a rotary holding unit that holds and rotates a substrate; a mirror member having a reflecting surface that opposes an end face of the substrate and a peripheral portion of a back surface of the substrate held by the rotary holding unit, the reflecting surface being inclined with respect to a rotation axis of the rotary holding unit; and a camera having an imaging device that receives both first light and second light through a lens, the first light coming from a peripheral portion of a front surface of the substrate held by the rotary holding unit, and the second light being a reflected light of second light which comes from the end face of the substrate held by the rotary holding unit and is reflected by the reflecting surface. 
     In the substrate imaging apparatus according to the one aspect of the disclosure, the mirror member has the reflecting surface that opposes an end face of the substrate and a peripheral portion of a back surface of the substrate held by the rotary holding unit, the reflecting surface being inclined with respect to a rotation axis of the rotary holding unit. In addition, in the substrate imaging apparatus according to the one aspect of the disclosure, the imaging device receives both the first light and the second light through the lens, the first light coming from the peripheral portion of the front surface of the substrate held by the rotary holding unit, the second light being a reflected light of second light which comes from the end face of the substrate held by the rotary holding unit and is reflected by the reflecting surface. Thus, both the peripheral portion of the front surface of the substrate and the end face of the substrate are simultaneously imaged by the one camera. Thus, since plural cameras are no longer necessary, the space for installation of these cameras is no longer needed. In addition, since a mechanism for moving the camera is unnecessary, the space for installation of such a mechanism is not necessary. Namely, the substrate imaging apparatus according to the one aspect of the disclosure can have a significantly simplified structure. As a result, the substrate imaging apparatus can achieve reduction in size and decrease in cost, while avoiding equipment failure. 
     The reflecting surface may be a curved surface that is recessed away from the end face of the substrate held by the rotary holding unit. In this case, the size of a mirrored image of the end face of the substrate reflected on the reflecting surface is enlarged. Thus, a more detailed image of the end face of the substrate can be obtained. As a result, by processing the image, the end face of the substrate can be more precisely inspected. 
     The substrate imaging apparatus according to the one aspect of the disclosure may further comprise a focus adjusting lens disposed in an optical path of the second light extending from the reflecting surface to the lens in order to adjust an image forming position, at which an image of the end face of the substrate is formed, onto the imaging device. As compared with the length of the optical path of the first light extending to the lens, the length of the optical path of the second light extending from the reflecting surface to the lens is longer because of the length of the second light reflected by the mirror member. However, in this case, since the image forming position of the end face of the substrate can be adjusted by the focus adjusting lens onto the imaging device, the images of the peripheral portion of the front surface of the substrate and the end face of the substrate are both clear. As a result, by processing the image thus taken according to the above, the end face of the substrate can be more precisely inspected. 
     The substrate imaging apparatus according to the one aspect of the disclosure may further comprise an illuminating unit including a light source and a light diffusing member that diffuses light from the light source toward a first direction perpendicular to an optical axis of the light from the light source in order to generate diffused light, wherein the illuminating unit irradiates the peripheral portion of the front surface of the substrate held by the rotary holding unit with the diffused light, and irradiates the reflecting surface of the mirror member with the diffused light in order to allow the diffused light reflected by the mirror member to fall on the end surface of the substrate held by the rotary holding unit. In this case, since the light from light source is diffused toward the first direction, the diffused light enters the end face of the substrate from various directions. Thus, the entire end face of the substrate can be uniformly illuminated. As a result, the end face of the substrate can be more clearly imaged. 
     The illuminating unit may further include: a light scattering member that scatters the light form the light source to generate scattered light; and a cylindrical lens that allows the scattered light from the light scattering member to pass through the light diffusing member, the cylindrical lens being convex toward the light diffusing member, wherein the cylindrical lens diffuses light coming into the cylindrical lens toward a second direction perpendicular to an optical axis of the light emitted from the light source and perpendicular to the first direction. In this case, since the scattered light is diffused toward the first and second directions, the diffused light enters the end face of the substrate from various directions. Thus, the end face of the substrate can be uniformly illuminated. As a result, the entire end face of the substrate can be more clearly imaged. 
     The substrate imaging apparatus according to the disclosure can achieve reduction in size and decrease in cost, while avoiding equipment failure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a substrate processing system. 
         FIG. 2  is a sectional view taken along the II-II line in  FIG. 1 . 
         FIG. 3  is a plan view showing unit processing blocks (BCT block, HMCT block, COT block and DEV block). 
         FIG. 4  is a sectional view of an inspection unit seen from above. 
         FIG. 5  is a sectional view of the inspection unit seen from the lateral side. 
         FIG. 6  is a perspective view showing the inspection unit. 
         FIG. 7  is a perspective view of a periphery imaging subunit seen from the front side. 
         FIG. 8  is a perspective view of the periphery imaging subunit seen from behind. 
         FIG. 9  is a plan view of the periphery imaging subunit. 
         FIG. 10  is a side view of a two-face imaging module. 
         FIG. 11  is an exploded perspective view showing an illuminating module. 
         FIG. 12  is a sectional view taken along the XII-XII line in  FIG. 11 . 
         FIG. 13  is a sectional view taken along the XIII-XIII line in  FIG. 11 . 
         FIG. 14A  is a picture showing a condition where light from a light source passed through a light scattering member. 
         FIG. 14B  is a picture showing a condition where the light from the light source passed through the light scattering member and the cylindrical lens. 
         FIG. 14C  is a picture showing a condition where the light from the light source passed through the light scattering member, the cylindrical lens and the light diffusing member. 
         FIG. 15A  is a diagram for explaining an optical path when there exists no focus adjusting lens. 
         FIG. 15B  is a diagram for explaining an optical path when there exists a focus adjusting lens. 
         FIG. 16  is a perspective view of a mirror member. 
         FIG. 17  is a side view of the mirror member. 
         FIG. 18A  is a diagram for explaining a condition where light from the illuminating module is reflected by the mirror member. 
         FIG. 18B  is a diagram for explaining a condition where light from a wafer is reflected by the mirror member. 
         FIG. 19A  shows an image that is taken when a front surface of a wafer is in focus without using focus adjusting lens. 
         FIG. 19B  shows an image that is taken when an end face of the wafer is in focus without using focus adjusting lens. 
         FIG. 19C  shows an image that is taken when both of the front surface of the wafer and the end face are in focus with the use of the focus adjusting lens. 
         FIG. 20  is a side view of a back surface imaging subunit. 
         FIG. 21  is a block diagram showing a main part of the substrate processing system. 
         FIG. 22  is a block diagram showing a hardware structure of a controller. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It should be firstly noted that the present invention is not limited to the below-described illustrative embodiments. In the below-described description, the same element or an element having the same function are designated by the same reference symbol, and overlapping description is omitted. 
     &lt;Substrate Processing System&gt; 
     As shown in  FIG. 1 , a substrate processing system  1  (substrate processing apparatus) includes a coating and developing apparatus  2  (substrate processing apparatus) and a controller  10  (control unit). The substrate processing system  1  is equipped with an exposure apparatus  3 . The exposure apparatus  3  has a controller (not shown) capable of communicating with the controller  10  of the substrate processing system  1 . The exposure apparatus  3  is configured to send and receive a wafer W (substrate) to and from the coating and developing apparatus  2 , and to perform an exposure process (pattern exposure) of a photosensitive resist film formed on a front surface Wa of a wafer W (see  FIG. 10 ). To be specific, a part to be exposed of the photosensitive resist film (photosensitive coating film) is selectively irradiated with an energy beam (ray) using a suitable method such as liquid immersion exposure. The energy beam may be, for example, ArF excimer laser, KrF excimer laser, g-ray, i-ray or EUV (Extreme Ultraviolet) ray. 
     Before the exposure process by the exposure apparatus  3 , the coating and developing apparatus  2  performs a process for forming a photosensitive resist film or a non-photosensitive resist film (collectively referred to as “resist film” herebelow) on the front surface Wa of the wafer W. After the exposure process by the exposure apparatus  3 , the coating and developing apparatus  2  performs a process for developing the exposed photosensitive resist film. 
     The wafer W may have a circular plate shape or may have a plate shape other than the circular shape such as a polygonal shape. The wafer W may have a cutout formed by partially cutting out the wafer W. The cutout may be, for example, a notch (U-shape or V-shaped groove) or a linearly extending part (so-called orientation flat). The wafer W may be, for example, a semiconductor substrate, a glass substrate, a mask substrate, an FPD (Flat Panel Display) substrate, or other various substrates. A diameter of the wafer W may be, for example, about 200 mm to 450 mm. When an edge of the wafer W is beveled (chamfered), the “front surface” in this specification includes the beveled part when seen from the side of the front surface Wa of the wafer W. Similarly, a “back surface” in this specification includes a beveled part when seen from the side of a back surface Wb of the wafer W (see  FIG. 10 ). An “end face” in this specification includes a beveled part when seen from the side of an end face We of the wafer W (see  FIG. 10 ). 
     As shown in  FIGS. 1 to 3 , the coating and developing apparatus  2  includes a carrier block  4 , a processing block  5  and an interface block  6 . The carrier block  4 , the processing block  5  and the interface block  6  are arrayed horizontally. 
     As shown in  FIGS. 1 and 3 , the carrier block  4  includes a carrier station  12  and a loading and unloading unit  13 . The carrier station  12  supports thereon a plurality of carriers  11 . Each carrier  11  can sealingly contain at least one wafer W. A side surface  11   a  of the carrier  11  is provided with an opening and closing door (not shown) through which a wafer W is taken into and out from the carrier  11 . The carrier  11  is detachably installed on the carrier station  12  such that the side surface  11   a  faces the loading and unloading unit  13 . 
     The loading and unloading unit  13  is positioned between the carrier station  12  and the processing block  5 . The loading and unloading unit  13  has a plurality of opening and closing door  13   a.  When the carrier  11  is placed on the carrier station  12 , the opening and closing door of the carrier  11  faces the opening and closing door  13   a.  By simultaneously opening the opening and closing door  13   a  and the opening and closing door in the side surface  11   a,  the inside of the carrier  11  and the inside of the loading and unloading unit  13  communicate with each other. The loading and unloading unit  13  incorporates a delivery arm A 1 . The deliver arm A 1  takes a wafer W out from the carrier  11  and delivers it to the processing block  5 , as well as receives a wafer W from the processing block  5  and returns it into the carrier  11 . 
     As shown in  FIGS. 1 and 2 , the processing block  5  has unit processing blocks  14  to  17 . The unit processing blocks  14  to  17  are arranged such that the unit processing block  17 , the unit processing block  14 , the unit processing block  15  and the unit processing block  16  are aligned in this order from the floor surface side. As shown in  FIG. 3 , each of the unit processing blocks  14  to  17  has a liquid processing unit U 1 , a thermal processing unit U 2  and an inspection unit U 3 . 
     The liquid processing unit U 1  is configured to supply various process liquids to a front surface Wa of a wafer W. The thermal processing unit U 2  is configured to perform a thermal process by heating a wafer W by, e.g., a heat plate and cooling the heated wafer W by, e.g., a cooling plate. The inspection unit U 3  is configured to inspect respective surfaces (front surface Wa, back surface Wb and end face Wc) of a wafer W (which will be described in detail later). 
     The unit processing block  14  is a lower film forming block (BCT block) configured to form a lower film on a front surface Wa of a wafer W. The unit processing block  14  incorporates a transfer arm A 2  that transfers a wafer W to the respective units U 1  to U 3  (see  FIG. 2 ). The liquid processing unit U 1  of the unit processing block  14  forms a coating film by coating a front surface Wa of a wafer W with a coating liquid for forming the lower film. The thermal processing unit U 2  of the unit processing block  14  performs various thermal processes for forming the lower film. A concrete example of the thermal processes may be a heating process for hardening the coating film into the lower film. The lower film may be an antireflection (SiARC) film, for example. 
     The unit processing block  15  is an intermediate film (hard mask) forming block (HMCT block) configured to form an intermediate film on the lower film. The unit processing block  15  incorporates a transfer arm A 3  that transports a wafer W to the respective units U 1  to U 3  (see  FIG. 2 ). The liquid processing unit U 1  of the unit processing block  15  forms a coating film by coating the lower film with a coating liquid for forming the intermediate film. The thermal processing unit U 2  of the unit processing block  15  performs various thermal processes for forming the intermediate film. A concrete example of the thermal processes may be a heating process for hardening the coating film into the intermediate film. The intermediate film may be an SOC (Spin On Carbon) film or an amorphous carbon film, for example. 
     The unit processing block  16  is a resist film forming block (COT block) configured to form a thermosetting resist film on the intermediate film. The unit processing block  16  incorporates a transfer arm A 4  that transfers a wafer W to the respective units U 1  to U 3  ( FIG. 2 ). The liquid processing unit U 1  of the unit processing block  16  forms a coating film by coating the intermediate film with a coating liquid (resist agent) for forming a resist film. The thermal processing unit U 2  of the unit processing block  16  performs various thermal processes for forming the resist film. A concrete example of the thermal processes may be a heating process (PAB: Pre Applied Bake) for hardening the coating film into the resist film. 
     The unit processing block  17  is a developing block (DEV block) configured to develop an exposed resist film. The unit processing block  17  incorporates a transfer arm A 5  that transfers a wafer W to the respective units U 1  to U 3 , and a direct transfer arm A 6  that transfers a wafer W without passing through these units (see  FIG. 2 ). The liquid processing unit U 1  of the unit processing block  17  develops the exposed resist film by supplying a developer to the resist film. The liquid processing unit U 1  of the unit processing block  17  supplies a rinse liquid to the developed resist film so as to rinse away dissolved components of the resist film together with the developer. Thus, the resist film is partly removed, so that a resist pattern is formed. The thermal processing unit U 2  of the unit processing block  16  performs various thermal processes for the developing process. A concrete example of the thermal processes may be a heating process before the developing process (PEB: Post Exposure Bake), a heating process after the developing process (PB: Post Bake) and the like. 
     As shown in  FIGS. 2 and 3 , a shelf unit U 10  is disposed in the processing block  5  on the side of the carrier block  4 . The shelf unit U 10  extends from the floor surface to the unit processing block  15 , and is divided into a plurality of cells aligned in the vertical direction. An elevation arm A 7  is provided near the shelf unit U 10 . The elevation arm A 7  moves a wafer W up and down among the cells of the shelf unit U 10 . 
     A shelf unit U 11  is disposed in the processing block  5  on the side of the interface block  6 . The shelf unit extends from the floor surface to an upper part of the unit processing block  17 , and is divided into a plurality of cells aligned in the vertical direction. 
     The interface block  6  incorporates a delivery arm A 8 , and is connected to the exposure apparatus  3 . The delivery arm A 8  is configured to take a wafer W from the shelf unit U 11  and deliver it to the exposure apparatus  3 , and is configured to receive a wafer W from the exposure apparatus  3  and return it to the shelf unit U 11 . 
     The controller  10  controls the substrate processing system  1  partly or entirely. Details of the controller  10  will be described later. The controller  10  can send and receive a signal to and from the controller of the exposure apparatus  3 . Due to the cooperation of the respective controllers, the substrate processing system  1  and the exposure apparatus  3  are controlled. 
     &lt;Structure of Inspection Unit&gt; 
     Next, the inspection unit U 3  is described in more detail with reference to  FIGS. 4 to 20 . As shown in  FIGS. 4 to 6 , the inspection unit U 3  includes a housing  100 , a rotary holding subunit  200  (rotary holding unit), a front surface imaging subunit  300 , a periphery imaging subunit  400  (substrate imaging apparatus) and a back surface imaging subunit  500 . The respective subunits  200  to  500  are accommodated in the housing  100 . A loading and unloading port  101  is formed in one end wall of the housing  100 , through which a wafer W is loaded to the inside of the housing  100  and unloaded to the outside of the housing  100 . 
     The rotary holding subunit  200  includes a holding table  201 , actuators  202 ,  203  and a guide rail  204 . The holding table  201  is structured as a suction chuck that substantially horizontally holds a wafer W by suction, for example. The shape of the holding table  201  (suction chuck) is not limited, and may be circular, for example. The size of the holding table  201  may be smaller than a wafer W. 
     The actuator  202  is, e.g., an electric motor that drives the holding table  201  for rotation. Namely, the actuator  202  rotates a wafer W held on the holding table  201 . The actuator  202  may include an encoder for detecting a rotating position of the holding table  201 . In this case, positions of the respective surfaces of a wafer W to be imaged by the respective imaging subunits  300 ,  400 ,  500  and the rotating position can be related to each other. If a wafer W has a cutout, the posture of the wafer W can be specified based on the cutout recognized by the respective imaging subunits  300 ,  400 ,  500 , and the rotating position detected by the encoder. 
     The actuator  203  is, e.g., a linear actuator that moves the holding table  201  along the guide rail  204 . Namely, the actuator  203  allows a wafer W held on the holding table  201  to be transferred between one end and the other end of the guide rail  204 . Thus, the wafer W held on the holding table  201  can be moved between a first position near the loading and unloading port  101 , and a second position near the periphery imaging subunit  400  and the back surface imaging subunit  500 . The guide rail  204  extends linearly (e.g., like a straight line) in the housing  100 . 
     The front surface imaging subunit  300  includes a camera  310  (imaging means) and an illuminating module  320 . The camera  310  and the illuminating module  320  constitute a set of imaging modules. The camera  310  includes a lens and one imaging device (e.g., CCD image sensor, CMOS image sensor, etc.). The camera  310  opposes the illuminating module  320  (illuminating unit). 
     The illuminating module  320  includes a half mirror  321  and a light source  322 . The half mirror  321  is disposed in the housing  100  such that it is inclined at substantially 45° with respect to the horizontal direction. The half mirror  321  is located above an intermediate portion of the guide rail  204  such that the half mirror  321  intersects the guide rail  204  when viewed from above. The half mirror  321  has a rectangular shape. The length of the half mirror  321  is larger than the diameter of a wafer W. 
     The light source  322  is located above the half mirror  321 . The light source  322  is longer than the half mirror  321 . Light emitted from the light source  322  passes through the whole half mirror  321  to travel downward (toward the guide rail  204 ). The light having passed through the half mirror  321  is reflected by an object located below the half mirror  321 , and is again reflected by the half mirror  321 . The light passes through the lens of the camera  310  and enters the imaging device of the camera  310 . Namely, the camera  310  can take an image of an object present in an irradiation area of the light source  322  through the half mirror  321 . For example, when the holding table  201  holding a wafer W is moved by the actuator  203  along the guide rail  204 , the camera  310  can take an image of the front surface Wa of the wafer W which passes through the irradiation area of the light source  322 . Data of the image taken by the camera  310  is transmitted to the controller  10 . 
     As shown in  FIGS. 4 to 10 , the periphery imaging subunit  400  includes a camera  410  (imaging means), an illuminating module  420  and a mirror member  430 . The camera  410 , the illuminating module  420  (illuminating unit) and the mirror member  430  constitute a set of imaging modules. The camera  410  includes a lens  411  and one imaging device  412  (e.g., CCD image sensor, CMOS image sensor, etc.). The camera  410  opposes the illuminating module  420 . 
     As shown in  FIGS. 7 to 13 , the illuminating module  420  is located above the wafer W held on the holding table  201 . The illuminating module  420  includes a light source  421 , a light scattering member  422  and a holding member  423 . As shown in  FIGS. 11 to 13 , the light source  421  is composed of, for example, a housing  421   a  and a plurality of LED point light sources  421   b  disposed in the housing  421   a.  These LED point light sources  421   b  are arranged in a line along the radial direction of the wafer W. 
     As shown in  FIGS. 7 to 13 , the light scattering member  422  is connected to the light source  421  so as to overlap with the light source  421 . As shown in  FIGS. 11 to 13 , the light scattering member  422  has a through-hole  422   a  that extends along the direction in which the light source  421  and the light scattering member  422  overlap with each other. An inner wall surface of the through-hole  422   a  is mirror finished. For the mirror finish, the inner wall surface may be plated with electroless nickel so as to form a plating film  422   b.  Thus, when light from the light source  421  enters the through-hole  422   a  of the light scattering member  422 , the incident light is irregularly reflected by the plating film  422   b,  as shown in  FIGS. 12 and 13 . Therefore, scattered light is generated in the light scattering member  422  (see  FIG. 14A ). 
     As shown in  FIGS. 7 to 13 , the holding member  423  is connected to the light scattering member  422  so as to overlap with the light scattering member  422 . As shown in  FIGS. 10 to 13 , the holding member  423  has a through-hole  423   a  and an intersection hole  423   b  that intersects the through-hole  423   a.  The through-hole  423   a  extends along a direction in which the light scattering member  422  and the holding member  423  are overlapped with each other. The intersection hole  423   b  extends from one side surface of the holding member  423  toward the through-hole  423   a  along a direction perpendicular to the through-hole  423   a.  The intersection hole  423   b  is connected to the through-hole  423   a.    
     As shown in  FIGS. 7 to 13 , the holding member  423  holds therein a half mirror  424 , a cylindrical lens  425 , a light diffusing member  426 , and focus adjusting lens  427 . As shown in  FIGS. 10 and 12 , the half mirror  424  is disposed on an intersection part of the through-hole  423   a  and the intersection hole  423   b  such that the half mirror  424  is inclined at substantially 45° with respect to the horizontal direction. The half mirror  424  has a rectangular shape. 
     As shown in  FIGS. 10 to 13 , the cylindrical lens  425  is disposed between the holding member  423  and the half mirror  424 . As shown in  FIGS. 10 to 12 , the cylindrical lens  425  is a convex cylindrical lens that is convex toward the half mirror  424 . An axis of the cylindrical lens  425  extends in a direction in which the plurality of LED point light sources  421   b  are aligned. When scattered light from the light scattering member  422  enters the cylindrical lens  425 , the scattered light is enlarged along a circumferential direction of the cylindrical surface of the cylindrical lens  425  (see  FIG. 14B ). 
     As shown in  FIGS. 10 to 13 , the light diffusing member  426  is disposed between the cylindrical lens  425  and the half mirror  424 . The light diffusing member  426  is a sheet-shaped member having a rectangular shape, and diffuses light having passed through the cylindrical lens  425 . Thus, diffused light is generated by the light diffusing member  426  (see  FIG. 14C ). For example, the light diffusing member  426  may have an isotropic diffusing function for diffusing incident light toward all the directions of the surface of the light diffusing member  426 , or may have an anisotropic diffusing function for diffusing incident light toward the axial direction of the cylindrical lens  425  (directions perpendicular to the circumferential direction of the cylindrical surface of the cylindrical lens  425 ). 
     As shown in  FIGS. 7, 8, 11 and 12 , the focus adjusting lens  427  is disposed in the intersection hole  423   b.  As long as the focus adjusting lens  427  is a lens having a function for varying a synthetic focal length with respect to the lens  411 , the configuration of the focus adjusting lens  427  is not limited. The focus adjusting lens  427  may be a lens having a parallelepiped shape, for example. 
     Suppose that only the lens  411  is used. In this case, as shown in  FIG. 15A , light from point A nearer to the lens  411  passes through the lens  411  and focuses on the imaging device  412 , and light from point B farther from the lens  411  passes through the lens  411  and focuses on a point deviated from the imaging device  412  (behind the imaging device  412 ). Thus, the image of the point A taken by the imaging device  412  is clear (in focus), but the image of the point B taken by the imaging device  412  is likely to be unclear (out of focus). On the other hand, suppose that there is the focus adjusting lens  427 . In this case, as shown in  FIG. 15B , light from the point B farther from the lens  411  is refracted by the focus adjusting lens  427 , and then the light passes through the lens  411  and focuses on the imaging device  412 . Due to the existence of the focus adjusting lens  427 , when the image of the point B is seen through the focus adjusting lens  427 , the point B looks like as if the Point B was located at a C point coplanar with the point A. Thus, when seen from the lens  411 , the distance between the point A and the lens  411 , and a distance between the seeming position of the Point B (C point position) and the lens  411  are identical to each other. Accordingly, the light from the point A and the light from the Point B both focus on the imaging device  412 . As a result, the images of the point A and the point B taken by the imaging device  412  are both clear. The above explanation similarly applies also to a case in which the focus adjusting lens  427  is a bifocal lens which has two portions with different refractive powers. 
     As shown in  FIGS. 7, 10, 12, 13 and 16 , the mirror member  430  is disposed below the illuminating module  420 . As shown in  FIGS. 7, 10, 12, 13, 16 and 17 , the mirror member  430  includes a body  431  and a reflecting surface  432 . The body  431  is made of an aluminum block. 
     As shown in  FIGS. 7, 13 and 17 , when a wafer W held by the holding table  201  is located at the second position, the reflecting surface  432  opposes an end face We of the wafer W and a peripheral portion Wd of a back surface Wb of the wafer W. The reflecting surface  432  is inclined with respect to the rotary axis of the holding table  201 . The reflecting surface  432  is mirror finished. For example, a mirror sheet may be attached to the reflecting surface  432 . Alternatively, an aluminum plating may be provided to the reflecting surface  432 , or an aluminum material may be vapor-deposited on the reflecting surface  432 . 
     The reflecting surface  432  is a curved surface that is recessed away from the end face Wc of the wafer W held on the holding table  201 . Namely, the mirror member  430  is a concave mirror. Thus, a mirror image of the end face Wc of the wafer W reflected on the reflecting surface  432  is enlarged. A radius of curvature of the reflecting surface  432  may be about 10 mm to 30 mm, for example. A divergence angle θ (see  FIG. 17 ) of the reflecting surface  432  may be about 100° to 150°. The divergence angle θ of the reflecting surface  432  herein means an angle defined by two planes circumscribing the reflecting surface  432 . 
     In the illuminating module  420 , light emitted from the light source  421  is scattered by the light scattering member  422 , enlarged by the cylindrical lens  425 , and diffused by the light diffusing member  426 . Thereafter, the light passes through the whole half mirror  424  to travel downward. The diffused light having passed through the half mirror  424  is reflected by the reflecting surface  432  of the mirror member  430  located below the half mirror  424 . When a wafer W held on the holding table  201  is located at the second position as shown in  FIGS. 13 and 18A , the diffused light having been reflected by the reflecting surface  432  mainly reaches the end face Wc of the wafer W (if the periphery of the wafer W has a beveled part, particularly an upper end of the beveled part) and the peripheral portion Wd of the front surface Wa. 
     The light having been reflected from the peripheral portion Wd of the front surface Wa of the wafer W is not directed toward the reflecting surface  432  of the mirror member  430  but is reflected again by the half mirror  424  (see  FIG. 18B ). The light then passes through the lens  411  of the camera  410  to enter the imaging device  412  of the camera  410 , without passing through the focus adjusting lens  427 . On the other hand, the light having been reflected from the end face Wc of the wafer W is reflected sequentially by the reflecting surface  432  of the mirror member  430  and the half mirror  424 . The light then passes sequentially through the focus adjusting lens  427  and the lens  411  of the camera  410  to enter the imaging device  412  of the camera  410 . Thus, the optical path length of the light coming from the end face Wc of the wafer W to fall on the imaging device  412  of the camera  410  is longer than the optical path length of the light coming from the peripheral portion Wd of the front surface Wa of the wafer W to fall on the imaging device  412  of the camera  410 . The optical path difference between these optical paths may be about 1 mm to 10 mm, for example. Thus, the imaging device  412  of the camera  410  receives both the light which comes from the peripheral portion Wd of the front surface Wa of the wafer W and the light which comes from the end face Wc of the wafer W. Namely, when the wafer W held by the holding table  201  is located at the second position, the camera  410  can image both the peripheral portion Wd of the front surface Wa of the wafer W and the end face Wc of the wafer W. Data of the images taken by the camera  410  are transmitted to the controller  10 . 
     If the peripheral portion Wd of the front surface Wa of the wafer W is focused without the existence of the focus adjusting lens  427 , the image of the peripheral portion Wd of the front surface Wa of the wafer W, which is taken by the camera  410 , is clear, but the image of the end face Wc of the wafer W, which is taken by the camera  410 , is likely to be unclear (see  FIG. 19A ), because of the optical path difference. On the other hand, if the end face of the wafer W is focused without the existence of the focus adjusting lens  427 , the image of the end face Wc of the wafer W is clear, but the image of the peripheral portion Wd of the front surface Wa of the wafer W imaged by the camera  410  is likely to be unclear (see  FIG. 19B ), because of the optical path difference. However, since there actually exists the focus adjusting lens  427  in the optical path of the light extending from the reflecting surface  432  of the mirror member  430  to the lens  411 , an image forming position, at which an image of the end face Wc of the wafer W is formed, can be adjusted onto the imaging device  412 , even through there is the optical path difference (see  FIG. 15B ). Thus, both the images of the peripheral portion Wd of the front surface Wa of the wafer W and the end face Wc of the wafer W, which were imaged by the camera  410 , are clear (see  FIG. 19C ). 
     As shown in  FIGS. 4 to 9 and 20 , the back surface imaging subunit  500  includes a camera  510  (imaging means) and an illuminating module  520  (illuminating unit). The camera  510  and the illuminating module  520  constitute a set of imaging modules. The camera  510  includes a lens  511  and one imaging device  512  (e.g., CCD image sensor, CMOS image sensor, etc.). The camera  510  opposes the illuminating module  520  (illuminating unit). 
     The illuminating module  520  is located below the illuminating module  420 , and below the wafer W held by the holding table  201 . As shown in  FIG. 20 , the illuminating module  520  includes a half mirror  521  and a light source  522 . The half mirror  521  is inclined at substantially 45° with respect to the horizontal direction. The half mirror  521  has a rectangular shape. 
     The light source  522  is located below the half mirror  521 . The light source  522  is longer than the half mirror  521 . Light emitted from the light source  522  passes through the whole half mirror  521  to travel upward. The light having passed through the half mirror  521  is reflected by an object located above the half mirror  521 , and is again reflected by the half mirror  521 . Then, the light passes through the lens  511  of the camera  510  to enter the imaging device  512  of the camera  510 . Namely, the camera  510  can image an object present in an irradiation area of the light source  522  through the half mirror  521 . For example, when the wafer W held by the holding table  201  is located at the second position, the camera  510  can image the back surface Wb of the wafer W. Data of the image imaged by the camera  510  are transmitted to the controller  10 . 
     &lt;Structure of Controller&gt; 
     As shown in  FIG. 21 , the controller  10  includes, as functional modules, a reading unit Ml, a storage unit M 2 , a processing unit M 3  and an instruction unit M 4 . These functional modules merely correspond to the functions of the controller  10  for the sake of conveniences, and do not necessarily mean that a hardware constituting the controller  10  is divided into these modules. The respective functional modules are not limited to modules whose functions are realized by executing a program, but may be modules whose functions are realized by a dedicated electric circuit (e.g., logic circuit) or an integrated circuit (ASIC: Application Specific Integrated Circuit). 
     The reading unit M 1  reads out a program from a computer-readable recording medium RM. The recording medium RM records a program for operating respective units of the substrate processing system  1 . The recording medium RM may be, for example, a semiconductor memory, an optical memory disc, a magnetic memory disc, or a magneto optic memory disc. 
     The storage unit M 2  stores various data. The storage medium M 2  stores various data for processing a wafer W (so-called process recipes), set data inputted by an operator through an external input apparatus (not shown) and so on, in addition to a program read out by the reading unit M 1  from the recording medium RM and data of images imaged by the cameras  310 ,  410 ,  510 . 
     The processing unit M 3  processes various data. For example, the processing unit M 3  generates, based on various data stored in the storage unit M 2 , signals for operating the liquid processing unit U 1 , the thermal processing unit U 2  and the inspection unit U 3  (for example, the rotary holding subunit  200 , cameras  310 ,  410 ,  510 , illuminating modules  320 ,  420 ,  520 ). In addition, the processing unit M 3  processes data of images imaged by the cameras  310 ,  410 ,  510 , and judges whether a wafer W has a defect or not. If it is judged that the wafer W has a defect, the processing unit M 3  generates a signal for stopping the process to the wafer W. 
     The instruction unit M 4  transmits signals generated by the processing unit M 3  to the respective apparatuses. 
     A hardware of the controller  10  is formed of one or more control computer(s), for example. The controller  10  has a circuit  10 A as a hardware configuration, which is shown in  FIG. 22 , for example. The circuit  10 A may be formed of an electric circuitry. Specifically, the circuit  10 A includes a processor  10 B, a memory  10 C (storage unit), a storage  10 D (storage unit), a driver  10 E and an input and output port  10 F. The processor  10 B cooperates with at least one of the memory  10 C and the storage  10 D to execute a program, so that a signal is inputted and outputted through the input and output port  10 F, whereby the aforementioned respective functional modules are realized. The memory  10 C and the storage  10 D function as the storage unit M 2 . The driver  10 E is a circuit for driving the respective apparatuses of the substrate processing system  1 . Signals are inputted and outputted through the input and output port  10 F, between the driver  10 E and the various apparatuses of the substrate processing system  1  (for example, rotating unit  21 , holding unit  22 , pumps  32 ,  42 , valves  33 ,  42 , thermal processing unit U 2 , holding table  201 , actuators  202 ,  203 , cameras  310 ,  410 ,  510 , light sources  322 ,  421 ,  522 ). 
     In this embodiment, although the substrate processing system  1  has one controller  10 , the substrate processing system  1  may have a group of controllers (control unit) formed of the plurality of controllers  10 . When the substrate processing system  1  has a group of controllers, the above-described functional modules may be respectively realized by the one controller  10 , or may be realized by a combination of two or more computers  10 . When the controller  10  is composed of a plurality of computers (circuits  10 A), the above-described functional modules may be realized by one computer (circuit  10 A), or may be realized by a combination of two or more computers (circuits  10 A). The controller  10  may have the plurality of processors  10 B. In this case, the above-described functional modules may be respectively realized by one processor  10 B, or may be realized by a combination of two or more processors  10 B. 
     &lt;Operation&gt; 
     In this embodiment, the mirror member  43  has the reflecting surface  432  that opposes the end face We and the peripheral portion Wd of the back surface Wb of the wafer W held by the holding table  201 , the reflecting surface  432  being inclined with respect to the rotation axis of the holding table  201 . In addition, in this embodiment, the imaging device  412  of the camera  410  receives, through the lens  411 , light which comes from the peripheral portion Wd of the front surface Wa of the wafer W held by the holding table  201 , and the reflected light which comes from the end face of the wafer W held by the holding table  201  and is reflected by the reflecting surface  432  of the mirror member  430 . Thus, both the peripheral portion Wd of the front surface Wa of the wafer W and the end face Wc of the wafer W are simultaneously imaged by the one camera  410 . Thus, since plural cameras are no longer necessary, a space for installation of such cameras is unneeded. In addition, since a mechanism for moving the camera  410  is unnecessary, a space for installation of such a mechanism is unneeded. Namely, in this embodiment, the inspection unit U 3  can have a significantly simplified structure. As a result, the inspection unit U 3  can achieve reduction in size and decrease in cost, while avoiding equipment failure. 
     In this embodiment, the reflecting surface  432  is a curved surface that is recessed away from the end face Wc of the wafer W held by the holding table  201 . Thus, a mirror image of the end face Wc of the wafer W reflected on the reflecting surface  432  is enlarged. For example, if the reflecting surface  432  is not a curved surface, the width of the end face Wc of the wafer W in the image on the imaging device is about 20 pixels. On the other hand, if the reflecting surface  432  is a curved surface as described above, the width of the end face Wc of the wafer W in the image on the imaging device is enlarged about 1.5 times in the thickness direction. Thus, a more detailed image of the end face Wc of the wafer W can be obtained. As a result, by processing the detailed image, the end face Wc of the wafer W can be more precisely inspected. 
     The optical path length of light, which comes from the end face Wc of the wafer W and is reflected by the reflecting surface  432  of the mirror member  430  to reach the lens  411 , is longer than the optical path length of light, which comes from the peripheral portion Wd of the front surface Wa of the wafer W to reach the lens  411 , because of the reflection by the mirror member  430 . However, in this embodiment, the focus adjusting lens  427  is disposed in the optical path of the light extending from the reflecting surface  432  of the mirror member  430  to the lens  411 . The focus adjusting lens  427  is configured to adjust an image forming position, at which the image of the end face Wc of the wafer W is formed, onto the imaging device  412 . Thus, owing to the focus adjusting lens  427 , the image forming position of the end face Wc of the wafer W can be adjusted onto the imaging device  412 , whereby both the images of the peripheral portion Wd of the front surface Wa of the wafer W and the end face Wc of the wafer W are clear. As a result, by processing the clear image, the end face Wc of the wafer W can be more precisely inspected. 
     In this embodiment, the illuminating module  420  irradiates the reflecting surface  432  of the mirror member  430  with diffused light in order to allow the diffused light from the illuminating module  420  which is reflected by the reflecting surface  432  of the mirror member  430 , to fall on the end face Wc of the wafer W held by the holding table  201 . Thus, the diffused light enters the end face Wc of the wafer W from various directions. Thus, the entire end face Wc of the wafer W can be uniformly illuminated. As a result, the end face Wc of the wafer W can be imaged more clearly. 
     In this embodiment, light emitted from the light source  421  is scattered by the light scattering member  422 , enlarged by the cylindrical lens  425  and further diffused by the light diffusing member  426 . Thus, the diffused light enters the end face Wc of the wafer W from various directions. Thus, the entire end face Wc of the wafer W can be uniformly illuminated. As a result, the end face Wc of the wafer W can be imaged more clearly. 
     &lt;Other Embodiments&gt; 
     The embodiment according to the disclosure has been described in detail, but the above embodiment can be variously modified within the scope of the present invention. For example, as long as the reflecting surface  432  is inclined with respect to the rotation axis of the holding table  201  and opposes the end surface Wc and the back surface Wb of the wafer W held by the holding table  201 , the reflecting surface  432  has another shape (e.g., flat shape) other than a curved face. 
     It is not necessary for the periphery imaging subunit  400  to include the focus adjusting lens  427 . 
     It is not necessary for the periphery imaging subunit  400  to include any of the light scattering member  422 , the cylindrical lens  425  and the light diffusing member  426 . 
     The inspection unit U 3  may be disposed in the shelf units U 10 , U 11 . For example, the inspection unit U 3  may be provided in the cells of the shelf units U 10 , U 11 , which are located correspondingly to the unit processing units  14  to  17 . In this case, a wafer W is directly delivered to the inspection unit U 3  by the arms A 1  to A 8  that transport the wafer W.