Visual inspection device of semiconductor wafer

Abstract

To create defect inspection recipe without making a semiconductor wafer having simulated defect.SOLUTION: A visual inspection device 100 comprises: a light source 106 for irradiating a semiconductor wafer 150 with light; a mirror 114 for directing light from the light source 106 toward the semiconductor wafer 150; a camera 118; a plate 108 arranged on an optical path from the light source 106 to the camera 118; and a control part 120 for creating defect inspection recipe of the semiconductor wafer 150. The plate 108 is provided with one or more shields 130 for blocking light from the light source 106 and is configured to transmit the light from the light source 106 through portions other than the one or more shields 130. The camera 118 images the semiconductor wafer 150 of which the simulated defect is projected by shadows of the one or more shields 130, and creates a plurality of inspection images including the simulated defect. The control part 120 adjusts parameters for inspection to create defect inspection recipe on the basis of an inspection result of the plurality of inspection images.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a technique for visually inspecting semiconductor wafers, and more particularly to a technique for creating a defect inspection recipe. [Background technology]

[0002] The manufacturing of semiconductor devices involves many processes. At each process, the semiconductor device is inspected for manufacturing defects (hereinafter referred to as "defects"). It is important to feed back the inspection results to the manufacturing process in order to improve the yield of semiconductor devices and prevent defective products from being shipped to customers.

[0003] As an example, visual inspection is widely used in the inspection of semiconductor wafers. Typically, a semiconductor wafer visual inspection device determines lighting conditions so that an image of a reference chip within the semiconductor wafer has a desired gray value. The semiconductor wafer visual inspection device then detects defects in the semiconductor wafer by comparing an inspection image captured by a camera with the reference image. Alternatively, the semiconductor wafer visual inspection device may process the captured image and detect defects in the semiconductor wafer based on the difference in brightness between each portion of the inspected surface of the semiconductor wafer.

[0004] Such semiconductor wafer visual inspection devices require a defect inspection recipe for inspecting semiconductor defects. The defect inspection recipe must be created before the inspection. As an example, a person in charge of creating the defect inspection recipe prepares a semiconductor wafer with simulated defects (hereinafter, also referred to as a "simulated defective wafer"). The person then adjusts the parameters of the defect inspection recipe so that the simulated defects in the simulated defective wafer can be detected. However, creating such a simulated defective wafer is time-consuming and labor-intensive. Therefore, a technology that makes it easier to create a defect inspection recipe is desired.

[0005] Regarding defect inspection recipe creation technology, for example, Japanese Patent Application Laid-Open No. 2001-337047 (Patent Document 1) discloses a defect inspection recipe creation method that "creates a provisional inspection recipe using a simulated defective wafer having a simulated defect pattern that has a change in height and a change in planar shape relative to a simulated normal pattern, performs defect inspection on the simulated defective wafer, verifies the defect detection sensitivity by comparing the detected defect data with simulated defect data of the simulated defective wafer obtained in advance, and creates a provisional inspection recipe by changing recipe parameters until a desired defect detection rate is obtained" (see [Abstract]). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-337047 Summary of the Invention [Problem to be solved by the invention]

[0007] According to the technology disclosed in Patent Document 1, an inspector needs to create a simulated defective wafer having simulated defect patterns with various variations in order to create a defect inspection recipe. Therefore, when the technology disclosed in Patent Document 1 is adopted, it takes time and effort to create the simulated defective wafer.

[0008] The present disclosure has been made in view of the above-described background, and an object of one aspect is to provide a technique for creating a defect inspection recipe without creating a simulated defective wafer. [Means for solving the problem]

[0009] According to one embodiment, a semiconductor wafer visual inspection apparatus is provided. The visual inspection apparatus includes a light source 106 for irradiating light onto a semiconductor wafer 150 to be inspected, a mirror 114 for refracting the light from the light source 106 and directing it toward the semiconductor wafer 150, a camera 118 for photographing the semiconductor wafer 150, a plate 108 disposed on an optical path from the light source 106 to the camera 118, and a control unit 120 for creating a defect inspection recipe for the semiconductor wafer 150. The plate 108 is configured such that one or more shields 130 are provided in a portion of the plate to block light from the light source 106, and portions other than the one or more shields 130 allow light from the light source 106 to pass through. The camera 118 photographs the semiconductor wafer 150 on which simulated defects caused by the shadows of the one or more shields 130 are projected, and generates a plurality of inspection images showing the simulated defects. The control unit 120 creates a defect inspection recipe by adjusting inspection parameters based on inspection results of the plurality of inspection images.

[0010] According to an embodiment, a defect inspection recipe can be created without creating a simulated defective wafer.

[0011] The above and other objects, features, aspects and advantages of the present disclosure will become apparent from the following detailed description of the disclosure taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of a configuration of a visual inspection apparatus 100 according to the present embodiment. [Figure 2] FIG. 1 is a diagram showing an example of a cross section of a semiconductor wafer to be inspected. [Figure 3] FIG. 1 is a diagram showing an example of the relationship between defects on a semiconductor wafer and the resulting images. [Figure 4] 10 is a diagram showing an example of an inspection image of a semiconductor wafer 150 onto which a shielding object 130 is projected. FIG. [Figure 5] FIG. 10 is a diagram showing an example of a procedure of a defect inspection recipe creation mode executed by the visual inspection apparatus 100. [Figure 6] It is a diagram showing a second example of the configuration of the appearance inspection device. [Figure 7] It is a diagram showing a third example of the configuration of the appearance inspection device. [Figure 8] It is a diagram showing a fourth example of the configuration of the appearance inspection device.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the technical idea according to the present disclosure will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Also, each embodiment, each modification, each software configuration, each hardware configuration, each function, and each process, etc. may be selectively combined as appropriate.

[0014] <A. Configuration of Appearance Inspection Device>

[0015] (a. Hardware)

[0016] FIG. 1 is a diagram showing an example of the configuration of an appearance inspection device 100 according to the present embodiment. The appearance inspection device 100 inspects the appearance of a semiconductor wafer. Also, the appearance inspection device 100 is configured to be able to create a defect inspection recipe without preparing a simulated defective wafer. The person in charge of inspecting the semiconductor wafer can save the labor and time required to prepare a simulated defective wafer by using the appearance inspection device 100. With reference to FIG. 1, the configuration and operation of the appearance inspection device 100 will be described. In a certain aspect, the appearance inspection device 100 may be any inspection device such as an optical defect inspection device using a laser beam or the like, or a charged particle beam defect inspection device using an electron beam or the like.

[0017] The visual inspection apparatus 100 includes a stage 102, a chuck 104, a light source 106, a plate 108, a plate holder 110, a drive unit 112, a mirror 114, an objective lens 116, a camera 118, a control unit 120, an output unit 122, an input unit 124, and a communication unit 126. The plate 108 is provided with one or more shields 130. The output unit 122 can be connected to one or more output devices 142. The input unit 124 can be connected to one or more input devices 144.

[0018] The stage 102 is a location on which the semiconductor wafer 150 to be inspected is placed. The stage 102 is configured to be freely movable in the horizontal direction (also called the X-axis direction and the Y-axis direction). As an example, the stage 102 includes two actuators for moving in each of the X-axis and Y-axis directions. The stage 102 may also have a function for adjusting the tilt of the semiconductor wafer 150. The visual inspection apparatus 100 can use the functions of the stage 102 to adjust the position and tilt of the semiconductor wafer 150 in the X-axis and Y-axis directions.

[0019] The chuck 104 secures the semiconductor wafer 150 to the stage 102. For example, the chuck 104 secures the semiconductor wafer 150 to the stage 102 by vacuum suction. In one aspect, the chuck 104 is connected to a compressor for creating a vacuum.

[0020] In one aspect, the visual inspection apparatus 100 may include a mechanism (not shown) that places an uninspected semiconductor wafer 150 on the stage 102 and moves an inspected semiconductor wafer 150 from the stage 102. In another aspect, the visual inspection apparatus 100 may be linked to a device (not shown) that places an uninspected semiconductor wafer 150 on the stage 102 and moves an inspected semiconductor wafer 150 from the stage 102.

[0021] The light source 106 is an illumination that irradiates light onto the semiconductor wafer 150 to be inspected. The light source 106 may be composed of an LED (Light Emitting Diode) or any other light emitting element. The light emitted from the light source 106 is reflected by a mirror 114 and directed toward the semiconductor wafer 150. The light then reaches the semiconductor wafer 150 via an objective lens 116. The light reflected from the surface of the semiconductor wafer 150 travels toward a camera 118 via the objective lens 116 and is projected onto an imaging surface of the camera 118. The objective lens 116 can adjust the focal length from the camera 118 to the semiconductor wafer 150.

[0022] The plate 108 projects simulated defects onto the surface of the semiconductor wafer 150. More precisely, the plate 108 projects the simulated defects onto the optical image of the semiconductor wafer 150 projected onto the camera 118. Hereinafter, an image corresponding to the optical image of the semiconductor wafer 150 projected onto the camera 118 will be referred to as an "inspection image." The plate 108 is configured to be movable by the plate holder 110. When creating a defect inspection recipe, the plate 108 is placed on the optical path of light emitted from the light source 106, as shown in FIG. 1 . The plate 108 is made of a material that transmits light. One or more shields 130 that block the light are provided on parts of the plate 108. The light is blocked in the parts of the plate 108 where the one or more shields 130 are provided. Meanwhile, the light can pass through other parts of the plate 108. As a result, the shadows of the one or more shields 130 are cast onto the surface of the semiconductor wafer 150. Each shadow of the one or more shields 130 becomes a simulated defect. In one aspect, it is assumed that one shield 130 is provided on the plate 108. In this case, the visual inspection apparatus 100 can acquire multiple inspection images with simulated defects at different positions by photographing each chip in the semiconductor wafer 150 while moving the plate 108 to change the position of the shadow. In another aspect, it is assumed that multiple shields 130 are provided on the plate 108. In this case, it is assumed that the visual inspection apparatus 100 can acquire multiple inspection images with simulated defects at different positions by photographing each chip in the semiconductor wafer 150 onto which each of the multiple shields 130 is projected.

[0023] In this way, the visual inspection apparatus 100 can create or project simulated defects onto the surface of the semiconductor wafer 150 by using the plate 108 including the shield 130. The visual inspection apparatus 100 can adjust the position and angle of the plate 108 and the stage 102 so that simulated defects of a desired size are displayed at a desired position in the inspection image. In addition, the visual inspection apparatus 100 may adjust the zoom magnification of the camera 118.

[0024] In one aspect, the plate 108 may be disposed between the mirror 114 and the camera 118. Since it is sufficient that the simulated defects are ultimately projected onto the image or video of the camera 118, the plate 108 may be disposed at any position on the optical path from the light source to the camera 118. In another aspect, the plate 108 may be circular, elliptical, rectangular, or any other shape.

[0025] In one aspect, one or more shields 130 may be provided on the surface of plate 108. In another aspect, one or more shields 130 may be provided inside plate 108. Furthermore, in another aspect, one or more portions of plate 108 may be replaced with one or more shields 130, respectively.

[0026] In one aspect, shields 130 of various shapes may be prepared for each type of known defect. As an example, shields 130 may be circular, elliptical, rectangular, or a combination thereof. Also, shields 130 of various sizes may be prepared for each type of known defect. As an example, the size of shield 130 may be determined so that the size of the simulated defect projected onto semiconductor wafer 150 is 1 to 20 μm (micrometers). In another aspect, shield 130 may be disposed at the center of plate 108. In this case, visual inspection apparatus 100 can project the shadow of shield 130 at any position on semiconductor wafer 150 by moving plate 108 on a plane perpendicular to the traveling direction of light. Also, visual inspection apparatus 100 can adjust the size of the shadow projected onto semiconductor wafer 150 by moving plate 108 in the traveling direction of light or the opposite direction.

[0027] In one aspect, one or more shields 130 may be arranged on the plate 108 so that the simulated defects are projected in a dispersed manner onto the semiconductor wafer 150. As an example, the one or more shields 130 are provided on the plate 108 so that the simulated defects are projected onto at least one of the center, the edge, or other positions of the semiconductor wafer 150.

[0028] The plate holding unit 110 holds the plate 108. The plate holding unit 110 is configured to be movable by a drive unit 112. As an example, the visual inspection apparatus 100 may be configured to be switchable between a defect inspection recipe creation mode and a normal inspection mode based on an operation from the input device 144. In this case, the plate holding unit 110 places the plate 108 on the optical path in the defect inspection recipe creation mode, and does not place the plate 108 on the optical path in the normal inspection mode.

[0029] In one aspect, the plate holder 110 may include multiple holders. The multiple holders may hold plates 108 in which at least a portion of the shape or position of one or more shields 130 differ from one another. The plate holder 110 may swap the plates 108 on the optical path based on an operation from the input device 144. The appearance inspection apparatus 100 may create multiple types of defect inspection recipes by swapping the plates 108 used. In another aspect, the plate holder 110 may be configured to hold multiple plates 108 stacked on top of one another. An inspector may create various types of defect inspection recipes by having the plate holder 110 hold combinations of different types of plates 108.

[0030] The driving unit 112 drives various actuators and the like of the visual inspection apparatus 100 based on commands received from the control unit 120. The driving unit 112 can individually drive the stage 102, the chuck 104, the light source 106, and the plate holder 110. More specifically, the driving unit 112 can control the motor of the stage 102 and the motor of the plate holder 110. The driving unit 112 can also control the compressor of the chuck 104. Furthermore, the driving unit 112 can turn the light source 106 on and off, adjust the brightness, and the like.

[0031] The mirror 114 reflects light from the light source 106 toward the semiconductor wafer 150 on the stage 102. As an example, the mirror 114 may be a half mirror or any other mirror. The objective lens 116 adjusts the zoom magnification of the camera 118. The appearance inspection apparatus 100 is configured so that the objective lens 116 is replaceable. An inspector can change the zoom magnification of the camera 118 by changing the objective lens 116.

[0032] The camera 118 converts the optical image of the surface of the semiconductor wafer 150 projected onto the camera 118 into an electrical image signal. The camera 118 also outputs the image signal to the control unit 120. In one aspect, the camera 118 may be an area camera or a line camera. In the defect inspection recipe creation mode, the semiconductor wafer 150 on which simulated defects are projected is projected onto the camera 118.

[0033] The control unit 120 controls the entire appearance inspection apparatus 100. The control unit 120 can also execute a program for a defect inspection recipe creation mode and a program for a normal inspection mode. By executing the program for the defect inspection recipe creation mode, the control unit 120 can create a defect inspection recipe using the plate 108. By executing the program for the normal inspection mode, the control unit 120 can inspect the appearance of the semiconductor wafer 150 using the created defect inspection recipe. The control unit 120 may include a processor (not shown), a random access memory (RAM) (not shown), and storage (not shown).

[0034] The processor may be configured with, for example, at least one integrated circuit. In one aspect, the integrated circuit may include at least one central processing unit (CPU), at least one graphics processing unit (GPU), at least one field programmable gate array (FPGA), at least one application specific integrated circuit (ASIC), at least one artificial intelligence (AI) chip, or a combination thereof.

[0035] The RAM functions as a workspace for the processor. The RAM stores programs executed by the processor and data referenced by the processor. In one aspect, the RAM can be realized by a dynamic random access memory (DRAM) or a static random access memory (SRAM), etc.

[0036] The storage is a non-volatile memory that stores programs executed by the processor and data referenced by the processor. The processor executes programs read from the storage to RAM and references data read from the storage to RAM. In one aspect, the storage can be realized by a hard disk drive (HDD), a solid state drive (SSD), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory, or the like.

[0037] The output unit 122 is configured to be connectable to an arbitrary output device 142. The appearance inspection apparatus 100 can display the operation interface of the appearance inspection apparatus 100, the inspection results, information on the defect inspection recipe, and the like on the output device 142. In one aspect, the output unit 122 may include the output device 142. In another aspect, the output unit 122 may be realized by a USB terminal, a D-sub terminal, a DVI (Digital Visual Interface) terminal, an HDMI (registered trademark) (High-Definition Multimedia Interface) terminal, a DisplayPort terminal, or the like. As an example, the output device 142 may be a cathode ray tube display, a liquid crystal display, an organic EL (Electro-Luminescence) display, or any other output device.

[0038] The input unit 124 is configured to be connectable to an arbitrary output device 142. The visual inspection apparatus 100 is configured to be able to receive, from the output device 142, an execution command for a defect inspection recipe creation mode and an execution command for a normal inspection mode. The visual inspection apparatus 100 is also configured to be able to receive, from the output device 142, an instruction to change the settings of various modes or any other instruction. In one aspect, the input unit 124 may include the output device 142. In another aspect, the input unit 124 may be realized by a USB terminal, a PS / 2 terminal, a Bluetooth (registered trademark) module, or the like. As an example, the output device 142 may be a keyboard, a mouse, a touchpad, or any other input device.

[0039] The communication unit 126 is connected to other devices via a wired network or a wireless network. The appearance inspection apparatus 100 may be configured to receive updates, etc. for various programs executed by the appearance inspection apparatus 100 via the communication unit 126. In one aspect, the communication unit 126 may be implemented by a wired LAN (Local Area Network) port, a Wi-Fi (registered trademark) (Wireless Fidelity) module, or the like. In another aspect, the communication unit 126 may send and receive data using a communication protocol such as TCP / IP (Transmission Control Protocol / Internet Protocol), UDP (User Datagram Protocol), or the like.

[0040] (b. Operation overview)

[0041] Next, an overview of the operation of the defect inspection recipe creation mode of the visual inspection apparatus 100 will be described. The control unit 120 receives an execution command for the defect inspection recipe creation mode via the input unit 124. Next, the control unit 120 sends a command to the drive unit 112 to adjust the position and angle of the semiconductor wafer 150. The control unit 120 also sends a command to the drive unit 112 to position the plate 108 on the optical path of the light emitted from the light source 106. Then, the control unit 120 sends a command to the drive unit 112 to emit light from the light source 106.

[0042] The light reaches the semiconductor wafer 150 via the plate 108, the mirror 114, and the objective lens 116. The light is then reflected from the surface of the semiconductor wafer 150 and reaches the camera 118 via the objective lens 116. An optical image of the semiconductor wafer 150, in which the shadow of the shielding object 130 is reflected, is projected onto the camera 118. That is, an optical image of the semiconductor wafer 150 in which the defect has been reproduced is projected onto the camera 118. The camera 118 outputs the image of the semiconductor wafer 150 in which the defect has been reproduced to the control unit 120.

[0043] The control unit 120 performs a visual inspection of the image using a provisional defect inspection recipe (hereinafter referred to as a provisional inspection recipe) prepared in advance. The parameters of the defect inspection recipe are adjusted based on the success rate of the visual inspection. The control unit 120 repeats the inspection of the image and the adjustment of the parameters of the defect inspection recipe until the defect detection rate reaches or exceeds a predetermined threshold. The control unit 120 saves the defect inspection recipe in storage based on the defect detection rate reaching or exceeding the predetermined threshold. In this way, the visual inspection apparatus 100 can create a defect inspection recipe simply by preparing a plate 108 for reproducing known defects on the surface of the semiconductor wafer 150. The visual inspection apparatus 100 can perform a visual inspection of the semiconductor wafer 150 using the created defect inspection recipe.

[0044] The visual inspection apparatus 100 is configured to allow various settings to be changed. As an example, the visual inspection apparatus 100 is configured to allow the inspection magnification to be adjusted by replacing the objective lens 116. The "inspection magnification" is the magnification at which the semiconductor wafer 150, which is the object of inspection, is enlarged. The visual inspection apparatus 100 performs site alignment by detecting marks set for each site on the semiconductor wafer 150, which has been divided according to the inspection magnification. As another example, the visual inspection apparatus 100 may adjust the brightness of the light source 106 so that a specified range on the semiconductor wafer 150 corresponds to a specified gray value. As another example, the visual inspection apparatus 100 may adjust the position of the semiconductor wafer 150 by driving the stage 102. The visual inspection apparatus 100 may also change the settings of the camera 118. For example, the camera 118 may be configured to output an inspection image expressed in 256 gray values.

[0045] As an example, the visual inspection apparatus 100 may perform an inspection using a reference image or an inspection using edge detection, etc. In an inspection using a reference image, the visual inspection apparatus 100 sets an average image of the semiconductor wafer 150 as the reference image. As an example, the reference image may be an image obtained by averaging the images of each chip in the semiconductor wafer 150. The visual inspection apparatus 100 compares the inspection image with the reference image and calculates the difference. If the difference is equal to or greater than a predetermined threshold, the visual inspection apparatus 100 determines that the semiconductor wafer 150 has a defect.

[0046] In an inspection using edge detection or the like, the visual inspection device 100 performs image processing such as edge detection on the inspection image. The visual inspection device 100 determines that the semiconductor wafer 150 has a defect based on the fact that the area of ​​the processed inspection image that is equal to or greater than a predetermined threshold has a gray value equal to or greater than a certain value.

[0047] As described with reference to FIG. 1 , the visual inspection apparatus 100 includes a light source 106 for irradiating light onto a semiconductor wafer 150 to be inspected, a mirror 114 for refracting the light from the light source 106 and directing it toward the semiconductor wafer 150, a camera 118 for photographing the semiconductor wafer 150, a plate 108 disposed on an optical path from the light source 106 to the camera 118, and a control unit 120 for creating a defect inspection recipe for the semiconductor wafer 150. The plate 108 is configured such that one or more shields 130 are provided in a portion of the plate 108 to block light from the light source 106, and the portions other than the one or more shields 130 allow light from the light source 106 to pass through. The camera 118 photographs the semiconductor wafer 150 on which simulated defects caused by the shadows of the one or more shields 130 are projected, and generates a plurality of inspection images showing the simulated defects. The control unit 120 creates a defect inspection recipe by adjusting inspection parameters based on the inspection results of the plurality of inspection images.

[0048] In one aspect, as shown in FIG. 1, plate 108 is configured to be positionable on the optical path from light source 106 to mirror 114 .

[0049] (c. Effect)

[0050] As described above, the visual inspection apparatus 100 can create a defect inspection recipe without using a simulated defective wafer, thereby significantly reducing the burden on the inspector.

[0051] More specifically, if the inspection surface of the semiconductor wafer 150 is an oxide film, the gray value of the inspection image will vary depending on factors such as the thickness of the oxide film within the wafer. Furthermore, if the inspection surface of the semiconductor wafer 150 is a metal, the gray value of the inspection image will vary depending on factors such as the type of metal and its surface condition. For example, suppose an inspector creates a defect inspection recipe that can detect a desired defect at a certain position on the semiconductor wafer 150. However, the defect inspection recipe may not be able to detect the same type of defect at other positions on the semiconductor wafer 150. Therefore, the inspector needs to create artificial defects in multiple chips at different positions on the semiconductor wafer 150, such as the center or periphery.

[0052] However, creating simulated defects on a large number of chips is not easy and requires a great deal of time and money. For example, when creating concave simulated defects, the simulated defects must be created on the semiconductor wafer 150 in the desired shape and size by etching or other methods. Furthermore, it is necessary to devise process conditions to prevent the generation of foreign matter during processing of the semiconductor wafer 150. For another example, when creating convex simulated defects, a convex pattern formation process must be added to the manufacturing flow of a normal product. Furthermore, adding this process to the manufacturing flow may require further consideration of optimizing the formation conditions for the concave defect process.

[0053] (d.Term)

[0054] Next, various terms used in this specification will be explained. In this specification, a "visual inspection apparatus" refers to equipment for visual inspection of semiconductor wafers, which is composed of one or more devices. Because the visual inspection apparatus 100 may include one or more devices, it may also be called a visual inspection system.

[0055] In this specification, a "semiconductor wafer" is a material that serves as the base for semiconductors. The semiconductor wafer 150 includes a wafer before a semiconductor circuit is formed, a wafer during the formation of a semiconductor circuit, and a wafer after a semiconductor circuit is formed. Also, it can be said that the inspection target of the appearance inspection apparatus 100 is the semiconductor circuit formed for each site on the divided semiconductor wafer 150. Therefore, in this specification, the semiconductor wafer 150 that is the inspection target may be read as a semiconductor component, a semiconductor chip, a chip, a circuit, a circuit component, etc.

[0056] In this specification, an "inspection image" refers to an image output by the camera 118 after photographing the semiconductor wafer 150 that is the inspection target. The inspection image includes an image of the semiconductor wafer 150 including defects or simulated defects and an image of the semiconductor wafer 150 without defects.

[0057] In this specification, a "simulated defect" is a defect deliberately provided on the semiconductor wafer 150. The simulated defect includes a defect physically provided on the semiconductor wafer 150 and a defect (i.e., a shadow) projected onto the semiconductor wafer 150. Also, the simulated defect includes a defect (i.e., a shadow) projected onto the optical image of the semiconductor wafer 150 projected onto the camera 118 (see FIG. 6).

[0058] In this specification, an "optical path" is the path along which the light irradiated from the light source 106 travels. Taking FIG. 1 as an example, the optical path refers to the path along which the light travels from the lens of the light source 106, through the mirror 114, the objective lens 116, the surface of the semiconductor wafer 150, and the objective lens 116, and reaches the camera 118.

[0059] <B. Structure of Semiconductor>

[0060] FIG. 2 is a diagram showing an example of a cross section of a semiconductor wafer to be inspected. An example of the configuration of the semiconductor wafer to be inspected will be described with reference to FIG. 2. The configuration shown in FIG. 2 is a reverse conductive insulated gate bipolar transistor (RC-IGBT) 200. Note that the inspection target of the visual inspection device 100 is not limited to the RC-IGBT 200. The visual inspection device 100 can inspect IGBTs and any other semiconductor circuits.

[0061] (a. Circuit configuration example)

[0062] The RC-IGBT 200 has an IGBT and a diode built into the same semiconductor substrate. The IGBT region 202A is a region that houses the IGBT. The diode region 202B is a region that houses the diode. A plurality of IGBT cells are formed together in the IGBT region 202A, and a plurality of diode cells are formed together in the diode region 202B.

[0063] The RC-IGBT 200 includes, in the IGBT region 202A, an n-type drift layer 210, a p-type base layer 212, a p+-type base layer 216, an n+-type emitter layer 214, a gate insulating film 222, a gate electrode 218, an n-type buffer layer 208, a p-type collector layer 206, a barrier metal 226, a tungsten plug 242, and an interlayer insulating film 224.

[0064] In the IGBT region 202A, the p+ type base layer 216 and the n+ type emitter layer 214 are joined to a first electrode 240 via a barrier metal 226 and a tungsten plug 242. The first electrode 240 is shared by the IGBT region 202A and the diode region 202B. The first electrode 240 functions as an emitter electrode in the IGBT region 202A and as an anode electrode in the diode region 202B. An aluminum alloy is generally used for the first electrode 240.

[0065] In addition, in the IGBT region 202A, a second electrode 204 is formed on the lower surface of the p-type collector layer 206. The second electrode 204 is also formed in the diode region 202B and is shared by the IGBT region 202A and the diode region 202B. The second electrode 204 functions as a collector electrode in the IGBT region 202A and as a cathode electrode in the diode region 202B. An aluminum alloy is generally used for the second electrode 204.

[0066] The RC-IGBT 200 includes, in the diode region 202B, an n-type drift layer 210, a p-type anode layer 234, and an n+-type cathode layer 230. Furthermore, in the diode region 202B, the RC-IGBT 200 includes an n-type buffer layer 208 between the n-type drift layer 210 and the n+-type cathode layer 230, and a p+-type anode layer 236 on the p-type anode layer 234. The n-type drift layer 210 and the n-type buffer layer 208 are commonly used in the IGBT region 202A and the diode region 202B.

[0067] In the diode region 202B, a trench 220 is formed, which extends from the upper surface of the p+ type anode layer 236, through the p+ type anode layer 236 and the p-type anode layer 234, and reaches the n- type drift layer 210. A gate insulating film 222 and a dummy gate electrode 238 are formed on the inner wall of the trench 220. The dummy gate electrode 238 is generally floating or grounded to a first electrode 240.

[0068] The interlayer insulating film 224, the barrier metal 226, and the tungsten plug 242 are provided in the diode region 202B as well as in the IGBT region 202A. That is, the first electrode 240 contacts the p+ type anode layer 236 via the tungsten plug 242 and the barrier metal 226 in the diode region 202B.

[0069] (b. Timing of visual inspection)

[0070] As described with reference to FIG. 2, a semiconductor circuit is manufactured by forming various layers on a base wafer. As an example, the appearance inspection device 100 can inspect a semiconductor wafer 150 such as an RC-IGBT 200 in a state where a barrier metal 226 is formed. As another example, the appearance inspection device 100 may use, as an inspection target, a semiconductor wafer 150 such as an RC-IGBT 200 after a first electrode 240 is formed.

[0071] Assume that there is a defect under the oxide film or under the barrier metal 226 on a certain chip on the semiconductor wafer 150 before the first electrode 240 is formed. In this case, even if the chip passes the electrical characteristic test, it may fail the reliability test. That is, there may be a case where a defective chip is tested twice, and the inspection process is not efficient. Therefore, it is desirable to inspect the appearance of the semiconductor wafer 150 before the formation of the first electrode 240.

[0072] <C. Examples of defects in semiconductor wafers reproduced by an appearance inspection device>

[0073] FIG. 3 is a diagram showing an example of the relationship between defects in a semiconductor wafer and the obtained images. On the left side of FIG. 3, cross-sections of a defect-free semiconductor wafer 300A, defective semiconductor wafers 300B and 300C are shown. In the semiconductor wafer 300B, a foreign object 320B exists under the barrier metal 226. That is, the semiconductor wafer 300B has a defect under the barrier metal 226. In the semiconductor wafer 300C, a foreign object 320C exists on the barrier metal 226. That is, the semiconductor wafer 300B has a defect under the oxide film (that is, on the barrier metal 226).

[0074] Assume that the camera 118 photographs the defect-free semiconductor wafer 300A from above. In this case, the appearance inspection device 100 acquires an inspection image such as the image 310A. Referring to the image | 310A, the barrier metal 226 is formed uniformly on the semiconductor wafer 300A. Also, there is no part where the gray value becomes extremely high on the image 310A.

[0075] Assume that camera 118 captures an image of defective semiconductor wafer 300B from above. In this case, visual inspection apparatus 100 acquires an inspection image such as image 310B. Referring to image 310B, it can be seen that the location of foreign matter 320B appears as a black circle or sphere. In other words, the gray value of the defective location is higher than the surrounding area.

[0076] Assume that camera 118 captures an image of defective semiconductor wafer 300C from above. In this case, visual inspection apparatus 100 acquires an inspection image such as image 310C. Referring to image 310C, it can be seen that the location of foreign matter 320C appears as a black circle or sphere. In other words, the gray value of the defective location is higher than the surrounding area.

[0077] As described with reference to FIG. 3 , when light is irradiated onto a semiconductor wafer 150 having a concave defect, such as semiconductor wafer 300B, the light is diffused by the concave defect. As a result, the location of the concave defect has a high gray value and appears black in the inspection image. Similarly, when light is irradiated onto a semiconductor wafer 150 having a convex defect, such as semiconductor wafer 300C, the light is diffused by the convex defect. As a result, the location of the convex defect has a high gray value and appears black in the inspection image. In either case, defects on the semiconductor wafer 150 are generally circular or spherical, and appear as black circles or dots in the inspection image. The visual inspection apparatus 100 can reproduce defects by placing a plate 108 having one or more shields 130 in the light path to project black circles or spheres onto the surface of the semiconductor wafer 150.

[0078] If the barrier metal 226 is made of tungsten, there will be a large difference in brightness between different parts on the semiconductor wafer 150. In such a case, the visual inspection apparatus 100 is particularly effective in detecting defects in the semiconductor wafer 150 and creating a defect inspection recipe.

[0079] 4 is a diagram showing an example of an inspection image of semiconductor wafer 150 onto which shielding object 130 is projected. The procedure by which visual inspection apparatus 100 acquires an inspection image of semiconductor wafer 150 having simulated defects will be described with reference to FIG.

[0080] Inspection image 410 is an image obtained by photographing a normal semiconductor wafer 150. When a normal semiconductor wafer 150 is photographed without using plate 108, visual inspection device 100 acquires an image like inspection image 410. Inspection image 420, which shows simulated defect 430, is an image in which the shadow of shielding object 130 is projected onto normal semiconductor wafer 150. When a normal semiconductor wafer 150 is photographed using plate 108, visual inspection device 100 acquires an image like inspection image 420.

[0081] The procedure for acquiring the inspection image 420 is as follows: The visual inspection apparatus 100 moves one or both of the plate holder 110 and the stage 102. As a result, the visual inspection apparatus 100 can project the shadow of the shielding object 130 of any size at any position on the surface of the semiconductor wafer 150. Next, the visual inspection apparatus 100 turns on the light source 106. Light emitted from the light source 106 passes through the plate 108. However, some of the light is blocked by one or more shielding objects 130 attached to the plate 108. As a result, a circular or spherical shadow corresponding to the shielding object 130 is projected onto the surface of the semiconductor wafer 150. The camera 118 captures the surface of the semiconductor wafer 150 on which the shadow is projected. Through this series of procedures, the visual inspection apparatus 100 can acquire the inspection image 420 in which the simulated defect 430 is captured.

[0082] In one aspect, the plate holder 110 may be configured to allow the plates 108 to be detachably attached. Alternatively, the plate holder 110 may be configured to hold a stack of multiple different plates 108 provided with shields 130 of different shapes. This allows the inspector to replace or combine the plates 108 depending on the application.

[0083] In another aspect, the visual inspection apparatus 100 may change the position of the shadow of the shielding object 130 (i.e., the simulated defect) projected onto the semiconductor wafer 150 multiple times and acquire an inspection image for each position of the shadow of the shielding object 130. As an example, the visual inspection apparatus 100 may move the shadow to the center, near the edge, and other positions of the semiconductor wafer 150. The visual inspection apparatus 100 may then photograph the semiconductor wafer 150 with the shadow at each position and acquire an inspection image. In this manner, the visual inspection apparatus 100 may acquire a sample of inspection images of the semiconductor wafer 150 having defects at various positions. The visual inspection apparatus 100 may also photograph the simulated defect on a chip or site basis. For example, the visual inspection apparatus 100 may project simulated defects onto multiple chips or sites located at different positions on the semiconductor wafer 150 and photograph these chips or sites.

[0084] In another aspect, the visual inspection apparatus 100 may use a plate provided with multiple shields 130. In this case, the visual inspection apparatus 100 can project the shadows of the shields 130 (i.e., simulated defects) onto multiple positions on the semiconductor wafer 150 simultaneously.

[0085] In another aspect, the plate holding unit 110 may hold a plurality of different plates 108 provided with shields 130 of different shapes for each type of defect to be reproduced. In this case, the visual inspection apparatus 100 may select the plate 108 to be placed on the optical path based on receiving a selection input of the defect to be reproduced from the input device 144. As an example, the visual inspection apparatus 100 may be configured to be able to select between the plate 108 corresponding to a concave-type simulated defect and the plate 108 corresponding to a convex-type simulated defect.

[0086] Furthermore, in another aspect, the visual inspection apparatus 100 may use a combination of these configurations or processes. In this way, the visual inspection apparatus 100 can reproduce desired simulated defects at any position on the semiconductor wafer 150 by using the plate 108 provided with one or more shields 130. Then, the visual inspection apparatus 100 can acquire one or more inspection images that serve as samples for adjusting the defect inspection recipe by photographing the semiconductor wafer 150 on which the simulated defects are reproduced.

[0087] As described with reference to Figure 4, by using the visual inspection apparatus 100, an inspector can obtain inspection images of semiconductor wafers with simulated defects without actually manufacturing semiconductor wafers with simulated defects.

[0088] To achieve this, the visual inspection apparatus 100 further includes a plate holding unit 110. The plate holding unit 110 may be configured to allow the plate 108 to be detachably attached. The plate holding unit 110 may also be configured to allow two or more plates 108 to be attached in a stacked manner.

[0089] The visual inspection apparatus 100 further includes a driving unit 112 that moves the plate holder 110. The driving unit 112 is configured to adjust the position of the shadow of the one or more shields 130 projected onto the semiconductor wafer 150 by moving the plate holder 110. More specifically, the plate holder 110 may be configured to be movable in the light traveling direction and the opposite direction. The plate holder 110 may also be configured to be movable on a plane perpendicular to the light traveling direction. The driving unit 112 can switch between using and not using the plate 108 by moving the plate holder 110. The driving unit 112 can adjust the position of the shadow of the shield 130 projected onto the semiconductor wafer 150 by moving the plate holder 110. The driving unit 112 can adjust the size of the shadow of the shield 130 projected onto the semiconductor wafer 150 by moving the plate holder 110.

[0090] Furthermore, the appearance inspection device 100 may be configured to selectively use a plurality of types of plates 108. In this case, the appearance inspection device 100 further includes an input unit 124 configured to receive a selection setting input for the plate 108. The plate holding unit 110 includes a plurality of plate holding units 110 that hold different plates 108 from each other. The driving unit 112 moves the plate holding unit 110 that holds the selected plate 108 so as to place the selected plate 108 on the optical path based on the selection setting input.

[0091] <D. Inspection Procedure of Appearance Inspection Device>

[0092] FIG. 5 is a diagram showing an example of the procedure of the process in the defect inspection recipe creation mode executed by the appearance inspection device 100. In a certain aspect, the processor of the control unit 120 may read a program for performing the process of FIG. 5 from the storage to the RAM and execute the program. In other aspects, part or all of the process may also be realized as a combination of circuit elements configured to execute the process. Furthermore, in other aspects, the following steps may be executed in a different order. The appearance inspection devices 600, 700, and 800 shown in FIGS. 6 to 8 described later also have the function of executing the series of processes shown in FIG. 5.

[0093] In step S505, the appearance inspection device 100 prepares the semiconductor wafer 150 on the stage 102. In a certain aspect, another machine may move the semiconductor wafer 150 from another location to the stage 102. In other aspects, the appearance inspection device 100 may include a mechanism for moving the semiconductor wafer 150 from another location to the stage 102.

[0094] In step S510, the visual inspection apparatus 100 selects the simulated defects to be projected. In one aspect, the visual inspection apparatus 100 may accept input of a selection setting for the simulated defects from the input device 144. In this case, the visual inspection apparatus 100 selects the simulated defects to be projected based on the selection setting. The process of selecting the simulated defects to be projected may include a process of selecting the plate 108 to be used from the multiple plates 108 held by the plate holder 110. The process of selecting the simulated defects to be projected may also include a process of determining the projection positions of the simulated defects on the semiconductor wafer 150. In this case, the visual inspection apparatus 100 may select the projection positions of the multiple simulated defects. In another aspect, the inspector may change the plate 108 attached to the plate holder 110.

[0095] In step S515, the visual inspection apparatus 100 selects parameters of the tentative inspection recipe. In one aspect, the parameters of the tentative inspection recipe may be stored in advance in a storage within the control unit 120. In this case, the visual inspection apparatus 100 reads the parameters of the tentative inspection recipe from the storage into RAM.

[0096] There may be many parameters depending on the inspection process and the type of semiconductor wafer 150 to be inspected. For example, the parameters may include the focal length in the optical system (i.e., the electron optical system), the pixel size of the defect image to be acquired, the amount of light to be irradiated, and the setting of the site alignment mark. In addition, the parameters may include an image processing filter such as smoothing or edge detection for removing noise, a gray value threshold for detecting a defect, an area threshold, and the like.

[0097] In step S520, the visual inspection apparatus 100 creates a tentative inspection recipe. More specifically, the visual inspection apparatus 100 selects the tentative inspection recipe including the multiple parameters acquired in step S515 as the recipe to be used for inspection. When control transitions from step S550 to S520, the visual inspection apparatus 100 selects the tentative inspection recipe including the adjusted parameters as the recipe to be used for inspection.

[0098] In step S525, the visual inspection apparatus 100 inspects the semiconductor wafer on which the simulated defects are projected. More specifically, when the light source 106 is turned on, light emitted by the light source 106 is directed toward the semiconductor wafer 150 via the mirror 114. A plate 108 is disposed on the optical path, and one or more shields 130 on the plate 108 block part of the light reaching the semiconductor wafer 150. As a result, shadows of the one or more shields 130, i.e., simulated defects, are projected onto the surface of the semiconductor wafer 150. The visual inspection apparatus 100 can acquire an inspection image showing the simulated defects by photographing the semiconductor wafer 150. The control unit 120 inspects the inspection image showing the simulated defects using the tentative inspection recipe.

[0099] In one aspect, visual inspection apparatus 100 may be configured to be able to specify the generation of simulated defects in multiple chips on semiconductor wafer 150. In this case, visual inspection apparatus 100 can perform visual inspection on the multiple chips.

[0100] In step S530, the visual inspection apparatus 100 compares the inspection results with the answers for the simulated defects prepared in advance. As an example, in step S510, the visual inspection apparatus 100 may determine settings such as the type and position of the simulated defects to be projected, and may also create answer data corresponding to the settings and store them in storage. As another example, the answer data may be pre-registered in the storage of the control unit 120. The answer data may include information such as the presence, type, and position of the simulated defects. The visual inspection apparatus 100 compares the inspection results obtained by inspection using the tentative inspection recipe with the answer data.

[0101] In one aspect, the processes of steps S525 to S530 may be repeatedly executed multiple times, and in doing so, visual inspection apparatus 100 may or may not change at least one of the type and position of the simulated defect to be projected.

[0102] In step S535, the visual inspection apparatus 100 calculates the defect detection rate. As an example, it is assumed that the visual inspection apparatus 100 repeatedly executes the processes of steps S525 and S530 N times (e.g., 100 times, 1000 times, etc.). In this case, the visual inspection apparatus 100 obtains N matching results. The visual inspection apparatus 100 calculates the percentage of matching results in which the inspection results match the answers to the simulated defects. As an example, if the inspection results match the answers to the simulated defects in 50 of the 100 matching results, the defect detection rate is 50%.

[0103] In step S540, the visual inspection apparatus 100 determines whether the defect detection rate exceeds a predetermined threshold (or is equal to or greater than the predetermined threshold). The threshold may be set to any value, such as 80%, 90%, or 99%. If the visual inspection apparatus 100 determines that the defect detection rate exceeds the predetermined threshold (or is equal to or greater than the predetermined threshold) (YES in step S540), the visual inspection apparatus 100 transfers control to step S545. If not (NO in step S540), the visual inspection apparatus 100 transfers control to step S550.

[0104] In step S545, the visual inspection apparatus 100 determines whether or not there has been a false detection of a defect. A false detection of a defect is when the semiconductor wafer 150 is determined to have a defect even though there is no defect in the semiconductor wafer 150. The false detection is mainly caused by noise. As one example, an optical defect inspection apparatus is affected by noise in the light intensity profile of reflected light from the semiconductor wafer 150. As another example, a charged particle beam defect inspection apparatus is affected by noise in the grayscale profile of an electron beam image formed by secondary electrons detected from the semiconductor wafer 150. If the visual inspection apparatus 100 determines that there has been a false detection of a defect (YES in step S545), it transfers control to step S550. If not (NO in step S545), the visual inspection apparatus 100 transfers control to step S555.

[0105] In step S550, the appearance inspection apparatus 100 adjusts the parameters of the defect inspection recipe. The parameters of the defect inspection recipe vary depending on the defect detection method. As an example, the appearance inspection apparatus 100 may use pattern comparison inspection or image processing inspection for defect detection. Furthermore, the appearance inspection apparatus 100 may use a combination of pattern comparison inspection and image processing inspection. Combining these inspection methods may improve inspection accuracy.

[0106] Pattern comparison inspection is a method for detecting defects by calculating the difference between an inspection image and a non-defective image. Pattern comparison inspection is effective when there is little variation in inspection images between chips in the semiconductor wafer 150. Parameters for pattern comparison inspection may include parameters related to the gray value (brightness) at which a pixel is detected as defective, and the minimum area (or number of pixels) to be detected as defective.

[0107] The gray value (brightness) parameter indicates the threshold for the absolute value of the difference between an inspection image and a good image for a pixel at the same location. For example, for a pixel at a certain location in an image, the gray value of the good image is 80, while the gray value of the inspection image is 20. In this case, the absolute value of the difference between the inspection image and the good image is 60. Also, assume that the gray value (brightness) parameter is 50. In this case, the absolute value of the difference between the inspection image and the good image (60) is greater than the gray value setting (50), so the visual inspection apparatus 100 determines that the inspection image contains a defect. The minimum area parameter indicates the threshold for the area (or number) of pixels detected as a defect. If only one pixel is detected as a defect, this detection result may be noise. Therefore, as an example, the minimum area parameter may be set to a number of pixels greater than or equal to two. The visual inspection apparatus 100 can individually adjust each setting of the pattern comparison inspection to detect the desired defect.

[0108] Image processing inspection is a method of detecting defects from the edge intensity between pixels after image processing. Image processing inspection is effective when there is a large variation in inspection images between chips in the semiconductor wafer 150. Parameters for image processing inspection may include parameters related to image pre-processing, image edge extraction, image post-processing, and the minimum area (or number of pixels) to be determined as a defect.

[0109] The pre-processing parameters relate to smoothing processing of the inspection image. A moving average filter, a Gaussian filter, or the like may be used for the smoothing processing. The edge extraction parameters relate to a horizontal differential filter, a vertical differential filter, or the like. The post-processing parameters relate to smoothing processing of the image after the edge extraction processing. A moving average filter, a Gaussian filter, or the like may be used for the smoothing processing. The minimum area parameter indicates a threshold value for the area (or number) of pixels detected as a defect. As an example, the minimum area parameter may be set to a number of pixels greater than or equal to two. The visual inspection apparatus 100 may individually adjust each setting of the image processing inspection so that the desired defect can be detected.

[0110] In step S555, the appearance inspection apparatus 100 determines the parameters of the defect inspection recipe. More specifically, the appearance inspection apparatus 100 selects the parameters of the current tentative inspection recipe as the parameters to be used in the actual inspection.

[0111] In step S560, the visual inspection apparatus 100 registers the parameters of the defect inspection recipe determined in step S555 in a database. The database may be located in the storage of the control unit 120. The database may be configured to allow multiple defect inspection recipes to be registered for each type of semiconductor wafer 150. In this case, the visual inspection apparatus 100 can select a defect inspection recipe to use from the database based on receiving a selection input of the defect inspection recipe via the input unit 124.

[0112] In step S565, the visual inspection apparatus 100 registers the determined defect inspection recipe in the visual inspection apparatus 100. The processing of this step may be processing of setting the determined defect inspection recipe as a defect inspection recipe to be used by default. Alternatively, the processing of this step may be processing of selecting the determined defect inspection recipe from within a database based on a user input.

[0113] As described above, by using the visual inspection apparatus 100, an inspector can create a defect inspection recipe without using a simulated defective wafer. Furthermore, by simply changing the type of shield 130, an inspector can create a defect inspection recipe that can detect desired defects. The type of shield 130 includes at least one of the position, size, and shape of the shield 130. For example, an inspector can change the type of shield 130 by replacing the plate 108 attached to the plate holder 110. Furthermore, the visual inspection apparatus 100 actually performs defect inspection using the semiconductor wafer 150 to be inspected. This allows the visual inspection apparatus 100 to verify the presence or absence of false positives (i.e., noise, etc.) and optimize the parameters of the defect inspection recipe. Furthermore, depending on the plate 108 used, the visual inspection apparatus 100 can create defect inspection recipes for detecting defects of various sizes. Therefore, by using the visual inspection apparatus 100, an inspector can also perform tests to detect defects above a certain size.

[0114] To achieve these effects, the control unit 120 can be configured to use the created defect inspection recipe to inspect multiple inspection images linked to the answers, refer to each of the multiple answers linked to each of the simulated defects in the multiple inspection images, calculate the detection rate of the simulated defects, and, based on the defect detection rate not exceeding a predetermined threshold, change at least a portion of the multiple parameters included in the defect inspection recipe and re-inspect the semiconductor wafer 150.

[0115] Further, in the inspection of a plurality of inspection images, the control unit 120 determines whether or not a semiconductor wafer 150 without defects is determined to have defects, and based on determining that the semiconductor wafer 150 without defects has defects, at least a part of a plurality of parameters included in the defect inspection recipe is changed, and the semiconductor wafer 150 may be configured to be reinspected.

[0116] <E. Other Configuration Examples of Appearance Inspection Device>

[0117] Next, referring to FIGS. 6 to 8, variations of the appearance inspection device according to the present embodiment will be described. The same components as those described with reference to FIG. 1 are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Also, in each of the various variations shown in FIGS. 6 to 8, variations of the various configurations and processes described with reference to FIGS. 1 to 5 can be applied.

[0118] FIG. 6 is a diagram showing a second example of the configuration of the appearance inspection device. The appearance inspection device 600 has a different position of the plate 108 compared to the appearance inspection device 100. The plate holding unit 110 is configured to be able to arrange the plate 108 between the mirror 114 and the camera 118.

[0119] The appearance inspection device 600 blocks a part of the light traveling toward the camera 118 by arranging the plate 108 on the optical path of the light reflected by the semiconductor wafer 150 and traveling toward the camera 118. By doing so, the appearance inspection device 600 can acquire an image similar to the image obtained when photographing a semiconductor wafer 150 with simulated defects.

[0120] 7 is a diagram showing a third example of the configuration of an appearance inspection apparatus. Appearance inspection apparatus 700 differs from appearance inspection apparatus 100 in that it further includes a second camera 702 with a higher magnification than camera 118. Appearance inspection apparatus 700 also includes a second mirror 704 and a third mirror 706 for directing light reflected from semiconductor wafer 150 toward second camera 702. In the example of FIG. 7, second mirror 704 and third mirror 706 are present, but depending on the position of second camera 702, appearance inspection apparatus 700 may include only second mirror 704.

[0121] The second camera 702 outputs an image or video to the control unit 120 for visual review by the inspector. The control unit 120 outputs the acquired image or video to the output device 142 such as a display via the output unit 122. The inspector can check in detail how the simulated defects are arranged on the semiconductor wafer 150 by referring to the image or video displayed on the output device 142.

[0122] In one aspect, the appearance inspection apparatus 700 may inspect the entire semiconductor wafer 150 and then sequentially photograph the detected defects with the second camera 702. In this way, the appearance inspection apparatus 700 can reduce the time required to adjust the illumination light and focus for the second camera 702.

[0123] 7, the appearance inspection apparatus 700 may include a second camera 702 with a higher magnification than the camera 118, and at least one other mirror (a second mirror 704, a third mirror 706) for refracting light reflected by the semiconductor wafer 150 and directing it toward the second camera 702. The control unit 120 may be configured to be able to output the image output by the second camera 702 to the output device 142.

[0124] FIG. 8 is a diagram showing a fourth example of the configuration of the appearance inspection apparatus. The appearance inspection apparatus 800 is a combination of the appearance inspection apparatuses 600 and 700. As shown in FIGS. 1 and 6 to 8, the plate 108 can be placed at any position on the optical path as long as the simulated defects can be projected onto the inspection image. The appearance inspection apparatus can also be equipped with a second high-magnification camera 702 for review, if necessary.

[0125] <F.まとめ>

[0126] As described above, the visual inspection apparatus according to this embodiment can create a defect inspection recipe without using a simulated defective wafer. This significantly reduces the burden on the inspector. Furthermore, the inspector can create a defect inspection recipe that can detect desired defects simply by changing the type of shielding object 130 (at least one of the position, size, and shape). Furthermore, the visual inspection apparatus 100 actually performs defect inspection using the semiconductor wafer 150 to be inspected. This allows the visual inspection apparatus 100 to verify the presence or absence of false detections (i.e., noise, etc.) and optimize the parameters of the defect inspection recipe. Furthermore, the visual inspection apparatus 100 can create defect inspection recipes for detecting defects of various sizes, depending on the plate 108 used. Therefore, the inspector can use the visual inspection apparatus 100 to perform tests to detect defects of a certain size or larger.

[0127] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims. Furthermore, the disclosures described in the embodiments and each modification are intended to be implemented, as far as possible, either alone or in combination. [Explanation of symbols]

[0128] 100, 600, 700, 800 Visual inspection apparatus, 102 Stage, 104 Chuck, 106 Light source, 108 Plate, 110 Plate holder, 112 Drive unit, 114 Mirror, 116 Objective lens, 118 Camera, 120 Control unit, 122 Output unit, 124 Input unit, 126 Communication unit, 130 Shield, 142 Output device, 144 Input device, 150, 300A, 300B, 300C Semiconductor wafer, 200 RC-IGBT, 202A IGBT region, 202B Diode region, 204 Second electrode, 206 P-type collector layer, 208 N-type buffer layer, 210 N-type drift layer, 212 P-type base layer, 214 N+-type emitter layer, 216 P+-type base layer, 218 Gate electrode, 220 trench, 222 gate insulating film, 224 interlayer insulating film, 226 barrier metal, 230 n+ type cathode layer, 234 p-type anode layer, 236 p+ type anode layer, 238 dummy gate electrode, 240 first electrode, 242 tungsten plug, 310A, 310B, 310C images, 320B, 320C foreign matter, 410, 420 inspection image, 430 simulated defect, 702 second camera, 704 second mirror, 706 third mirror.

Claims

1. a light source for irradiating light onto a semiconductor wafer to be inspected; a mirror for refracting light from the light source toward the semiconductor wafer; a camera for photographing the semiconductor wafer; a plate disposed on an optical path from the light source to the camera; a control unit that creates a defect inspection recipe for the semiconductor wafer, The plate is One or more shields are provided on a portion of the plate to block light from the light source; The light source is configured to transmit light from the light source in a portion other than the one or more shielding members, the camera captures an image of the semiconductor wafer on which the simulated defects caused by the shadows of the one or more obstructions are projected, and generates a plurality of inspection images showing the simulated defects; The control unit creates the defect inspection recipe by adjusting parameters related to inspection based on inspection results of the plurality of inspection images.

2. The visual inspection apparatus according to claim 1 , wherein the plate is configured to be able to be placed on an optical path from the light source to the mirror.

3. The visual inspection apparatus according to claim 1 , wherein the plate is configured to be able to be placed on an optical path from the mirror to the camera.

4. a second camera having a higher magnification than the first camera; and at least one other mirror for refracting light reflected by the semiconductor wafer toward the second camera.

4. The visual inspection device according to claim 1, wherein the control unit is configured to be able to output the image output by the second camera to an output device.

5. Further comprising a plate holder, 4. The visual inspection device according to claim 1, wherein the plate holding section is configured to allow the plate to be attached and detached.

6. Further, a drive unit that moves the plate holder is provided.

6. The visual inspection apparatus according to claim 5, wherein the drive unit is configured to be able to adjust the position of a shadow cast by the one or more shielding objects onto the semiconductor wafer by moving the plate holder.

7. further comprising an input unit configured to be able to receive input for selecting and setting the plate; the plate holder includes a plurality of plate holders each holding a different plate, 7. The visual inspection apparatus according to claim 6, wherein the driving section moves the plate holding section that holds the selected plate so as to position the selected plate on the optical path based on the selection setting input.

8. 6. The visual inspection device according to claim 5, wherein the plate holding section is configured so that two or more of the plates can be attached in a stacked manner.

9. The control unit Inspecting the plurality of inspection images associated with the solutions using the defect inspection recipe; referencing each of a plurality of answers associated with each of the simulated defects in the plurality of inspection images; Calculating the detection rate of the simulated defects; determining whether or not a defect detection rate in the inspection of the simulated defects exceeds a predetermined threshold; 4. The visual inspection apparatus according to claim 1, configured to change at least a portion of a plurality of parameters included in the defect inspection recipe and re-inspect the semiconductor wafer based on the defect detection rate not exceeding the predetermined threshold.

10. The control unit determining whether or not the semiconductor wafer having no defects has been determined to have defects in the inspection of the plurality of inspection images; 10. The visual inspection apparatus according to claim 9, configured to change at least a portion of the plurality of parameters included in the defect inspection recipe and re-inspect the semiconductor wafer based on determining that the semiconductor wafer is defective even though it is not.

Images