Apparatus and method for detecting defects in singulated semiconductor devices

Abstract

To provide an apparatus for detecting side defects and internal defects in a singulated workpiece with high resolution.SOLUTION: At least one light source 18 is provided, which generates illumination light in a wavelength range in which the workpiece 2 is transparent. The camera 6 images the light from at least one side of the workpiece 2 onto its detector 26 by means of a lens. The stage is used to move the workpiece 2 so that at least one surface of the workpiece 2 is fully imaged with the camera 6.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a workpiece defect detection apparatus. Further, the present invention relates to a workpiece defect detection method. Additionally, the present invention relates to a computer program product disposed on a non-transitory computer readable medium, in particular a product comprising computer-executable process steps operable to control a computer for defect detection in a workpiece. [Background technology]

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 088284, filed December 5, 2014, and U.S. Provisional Patent Application No. 62 / 154109, filed April 28, 2015, the entire contents of both of which are incorporated herein by reference.

[0003] For example, Patent Document 1 discloses an infrared test for semiconductor chips. This test is performed by radiating infrared light onto the bottom surface of the semiconductor chip, receiving the infrared light reflected from the bonding pads, and displaying an image of the bonding pads on a monitor. This infrared image contains information on whether there are defects in the bonding pads themselves or in the silicon substrate below the bonding pads, or whether there is any misalignment of the bonding pads relative to the bumps.

[0004] Patent Document 2 discloses a detection device that is mainly used to detect internal defects in semiconductor materials whose band gap is greater than 1.12 eV. This detection device for detecting internal defects in semiconductor materials is composed of an optical microscope, an infrared CCD camera, a video cable, a simulation image monitor, a digital image acquisition card, a computer, and software for analysis, processing, and display.

[0005] Additionally, Patent Document 3 discloses a photoelectric method for recording thermal diagrams of land temperature distribution, using an infrared line scanning system on an aircraft. This device utilizes a rotary scanning mirror system that receives thermal radiation through a window. The mirror system has four reflective sides and is rotated around an axis by an electric motor. The mirror directs the radiation to an IR lens and then to a row of photoelectric receiver elements. The row of receiver elements is parallel to the axis of rotation of the mirror system, and each receiver element is individually connected to a corresponding one of a plurality of light-emitting diodes by a lead wire and an amplification device.

[0006] Patent document 4 discloses an apparatus for analyzing wafer microstructured samples. The purpose of this apparatus is to increase the potential applications of the apparatus, in particular to show structural details of wafers that are structured on both sides but whose structure is not visible in VIS or UV due to non-transparent coatings or intervening materials. In particular, the sample can be shown simultaneously in reflected or transmitted IR light and reflected visible light by using IR light as reflected light while generating transillumination that significantly improves the contrast in the IR image.

[0007] Typical defects include side cracks caused by the dicing process and embedded cracks caused by internal stress between the dielectric layer and silicon structure within the device.

[0008] FIG. 1 shows a conventional method for detecting side defects 9 on a semiconductor device 2 by performing four-side or five-side inspection. The semiconductor device 2 has a first side 31, a second side 32, a third side 33, a fourth side 34, a top surface 4, and a bottom surface 5. In the setup shown in FIG. 1, a camera 6 with a lens 7 views the bottom surface 5 of the semiconductor device 2. Mirrors 8 are positioned at 45° with respect to the first side 31, the second side 32, the third side 33, and the fourth side 34 of the semiconductor device 2, respectively. In FIG. 1, only the mirrors 8 positioned with respect to the second side 32 and the fourth side 34 of the semiconductor device 2 are shown.

[0009] The setup shown in FIG. 1 provides images 10 (see FIG. 2) of the first side 31, the second side 32, the third side 33, the fourth side 34, and the bottom 5. Additionally, the setup shown in FIG. 1 has a major drawback: the optical length 11 of the bottom 5 view is different from the optical lengths 12 of the first side 31, the second side 32, the third side 33, and the fourth side 34 views. Therefore, focus is always traded off between focus on the bottom 5 side of the semiconductor device 2 and focus on each of the first side 31, the second side 32, the third side 33, and the fourth side 34. Additionally, resolving these four-side views requires a wide field of view, which would limit the available pixel resolution. For side views smaller than 10 μm, no working setup is available, even with a high-resolution camera with 20 or 25 megapixels. Therefore, it is not possible to achieve good focus and high resolution, thereby distinguishing real defects from non-critical contamination.

[0010] Figure 3 shows another example of a conventional setup, specifically for detecting internal defects 9 (side surface defects) by viewing the top surface 4 of a semiconductor device 2. No high-volume inspection strategy is suitable for detecting internal defects 9 (defects not visible from the outside). Existing methods rely on slower techniques, specifically using IR light 13 and optics 14 and viewing the backside of the semiconductor device 2 ("IR backside view"). A camera 6 detects IR light 15 returning from the semiconductor device 2. Figure 4 shows a schematic representation of an image 16 obtained with the setup shown in Figure 3. This "IR backside view" method of detecting internal defects 9 with IR light 13 also has drawbacks. First, the method is slow. Only manual, low-volume techniques exist. Automating and speeding up this method imposes significant limitations on the number of pixels and size of available IR cameras 6. Additionally, the set of devices that work well is limited to those with bare silicon side surfaces through which IR light can reach. The trend is for devices to have protective coatings that are not transparent to IR light. A further drawback is the signal-to-noise ratio. Since reflections also occur at the top surface 4 of the semiconductor device 2, it may be difficult to distinguish top surface defects from interior defects 9.

[0011] This conventional method described above has significant drawbacks, especially when inspecting five sides of a workpiece (singulated semiconductor device). One drawback is the difference in focus between the side and bottom of the workpiece. Because the optical lengths are different for the bottom and side views, the focus is always a trade-off between focus on the bottom side of the workpiece and focus on the edge (side) side of the workpiece. Another drawback is image resolution. A four-side view requires a wide field of view, which may limit the available pixel resolution. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Patent No. 6,339,337 [Patent Document 2] Chinese Utility Model No. 2791639 [Patent Document 3] European Patent No. 2699071 [Patent Document 4] U.S. Patent No. 8,154,718 Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to provide an apparatus for detecting side and internal defects in singulated workpieces with high resolution, and for distinguishing between defects and contamination present on the surface of the workpiece, while requiring a high throughput for performing time-saving quality control on such workpieces. [Means for solving the problem]

[0014] The purpose of the above is to at least one light source that provides illumination light in a wavelength range that the workpiece is transparent to; a camera with a lens that images light from at least one side of the workpiece onto a detector of the camera; a stage for moving the workpiece and for completely imaging said at least one side of the workpiece; This is achieved by a workpiece defect detection apparatus comprising:

[0015] An advantage of the apparatus of the present invention is that it can reliably detect side and internal defects in singulated workpieces, such as semiconductor devices, also known as dies, and can be used to perform high-throughput quality control on such workpieces.

[0016] It is a further object of the present invention to provide a method for detecting side and internal defects in singulated workpieces with high resolution, allowing for differentiation between contamination on the surface of the workpiece and actual defects, and for the method to be scalable to a high throughput to perform quality control on such workpieces in a time period short enough to do so.

[0017] The purpose of this is to illuminating a portion of at least one surface of the workpiece with illumination light in a wavelength range through which the workpiece is transparent; imaging light from said portion of at least one surface of the workpiece onto a detector of a camera; performing relative movement of a stage holding the workpiece and the camera such that the at least one side of the workpiece is completely imaged by the camera; This is achieved by a workpiece defect detection method having:

[0018] An advantage of the method of the present invention is that it can reliably detect side and internal defects in singulated workpieces, such as semiconductor devices, also known as dies, and can be used to perform high-throughput quality control on such workpieces.

[0019] It is a further object of the present invention to provide a computer program product stored on a non-transitory computer-readable medium for automatically detecting side and internal defects in singulated workpieces (semiconductor devices) with high resolution, and thereby distinguishing between defects and contamination present on the surface of the workpiece. In addition, the computer program is required to have a high throughput to perform quality control on such workpieces in a sufficiently short time.

[0020] The object of the above is a computer program product disposed on a non-transitory computer readable medium for detecting defects in a workpiece, the computer program product controlling a computer to execute computer executable process steps constituting the product, Place the workpiece on the stage, illuminating at least one surface of the workpiece with illumination light in a wavelength range in which the workpiece is transparent; an optical setup for directing light from the at least one surface of the workpiece onto at least one line sensor in a camera to image a line of light from the at least one surface of the workpiece; and moving a stage holding the workpiece so that the at least one surface of the workpiece is completely imaged by the line sensor of the camera and is located at a focal point of the camera during movement of the stage; This is achieved by a computer program product that makes it possible to:

[0021] Typical defects that can be detected by the present invention include side cracks caused by the dicing process of the workpiece and embedded cracks caused by internal stress within the workpiece. If the workpiece is a semiconductor device, the internal stress may appear, for example, between a dielectric layer and a silicon structure. However, the present invention (apparatus, method, and computer program) is not limited to semiconductor devices and can be applied to side defects and internal defects in general.

[0022] Typically, infrared (IR) light will be used, which can penetrate silicon-based semiconductor devices, but the light source can be different depending on the wavelength range for which the workpiece material is transparent.

[0023] According to one aspect of the invention, the at least one illumination source is arranged such that illumination light is directed toward one side of the workpiece and the camera receives light from a far side of the workpiece, the far side being opposite the side of the workpiece that receives the illumination light, thereby providing backlight illumination.

[0024] Another approach is to orient the far side of the workpiece relative to the side that receives the illumination light so that a dark field image of the far side is obtained.

[0025] In a further aspect of the present invention, at least one illumination source as described above is arranged so that illumination light is directed onto the top surface of the workpiece and the camera receives light emitted from the top surface of the workpiece.

[0026] In a preferred embodiment of the present invention, the camera detector is a line sensor and the camera is configured as a line scan camera. This novel apparatus or method uses a line scan camera perpendicular to the side of the workpiece (semiconductor device) and generates an image by moving the workpiece on an XYθ stage. The optical setup of the present invention can generate simultaneous views of at least a portion of the top surface and at least one side of the workpiece. This optical setup also allows for coaxial illumination and external illumination, and the illumination can be the same or separate in these two modes.

[0027] A camera lens images a line of light emerging from the side of the workpiece onto a line sensor, the light originating from at least one illumination source arranged to provide backlight illumination.

[0028] A stage holding the workpiece is moved along a scan direction perpendicular to the line to be imaged, and this scan motion generates a complete image of at least one side of the workpiece.

[0029] A line of light from at least a portion of the workpiece's top surface adjacent to one of the workpiece's sides can be imaged onto a line sensor by a camera lens, and the at least one light source can be arranged so that the light from the top surface is coaxial with the light directed onto at least a portion of the workpiece's top surface. To generate an image of at least a portion of the workpiece, a stage holding the workpiece is moved along a scan direction perpendicular to the line to be imaged, thereby obtaining a complete image of at least a portion of the top surface adjacent to at least one of the workpiece's sides.

[0030] Also, relative motion can be performed by the stage and camera, for example, to capture a complete image of each side of the workpiece. Scanning of each side can be performed with various velocity profiles along the scan direction. A preferred embodiment is a constant velocity along the length of each side. Choosing a constant velocity requires less software effort and provides the best image quality. As will be apparent to those skilled in the art, the selection of a constant velocity does not preclude other velocity profiles. Another embodiment is to increase or decrease the velocity during the scan. This embodiment allows for a higher imaging velocity at the edges and a lower imaging velocity in the center of each side.

[0031] According to one embodiment of the present invention, an optical setup is provided that simultaneously generates a line of light image emerging from a side of a workpiece and a line of light image emerging from the top surface of the workpiece. The line of light image from the top surface is positioned adjacent to a line of light from each side of the workpiece. The leading edge of the optical setup carries an upper mirror and first and second lower mirrors. The upper mirror captures the line of light image from a portion of the top surface of the workpiece. The first and second lower mirrors capture the line of light image emerging from the side of the workpiece. The optical setup of the present invention is designed so that the line of light image emerging from the side of the workpiece and the line of light image emerging from the top surface of the workpiece are simultaneously in focus.

[0032] According to one embodiment of the present invention, light from at least one light source can be coupled separately into one side of the workpiece and into the top surface of the workpiece.

[0033] Advantageously, an optical waveguide is disposed between at least one of the light sources and the top surface and / or each side surface of the workpiece.

[0034] An example of a workpiece is a singulated semiconductor device, in which case the wavelength range of the illumination light is the wavelength range of IR light, since silicon-based semiconductor devices are transparent to IR light.

[0035] The device of the present invention has unique advantages: it can combine two views. It is not necessary to capture two images with separate cameras. By combining two views, it is possible to perform image processing based on the view that leads to a higher capture rate suitable for defects and the view that leads to a lower discomfort level suitable for noise, thereby correcting the information. The use of a line scan camera provides high-resolution images. Images can be generated with higher resolution than with a regular matrix camera. The use of IR light allows for the locating of internal defects and / or an improved signal-to-noise ratio for individual defects. It is also possible to perform a top view (image of a portion of the top surface) at a certain angle, creating an inspection mode similar to dark field.

[0036] The method of the present invention is beneficial when the workpiece is a semiconductor device, for example. It allows for the generation of images of defects by using IR light traveling through the semiconductor device under inspection and by viewing one side of the device directly. A vertical setup (viewing / illuminating the edge directly) or an angled setup can be used for both the light source and the camera. Due to the high refractive index of silicon (n=3.5 at λ=1200 nm) and the rough edges of the device, nearly all of the light will enter the device. The light will travel at a small angle through the device and exit the other side of the device as a diffused beam. In this way, the device itself behaves like diffuse illumination.

[0037] A method according to one embodiment of the present invention uses a physical property of silicon (which is the base material for all semiconductor devices) that makes it transparent to light with wavelengths above 1200 nm.

[0038] The method is also built for "IR backside view" with this in mind, but because the device itself acts like a diffuse illuminator, the method of the present invention increases the signal-to-noise ratio and opens the door to a high-speed inspection solution. Edge variations from the dicing process are typically smoothed out by the diffused light. Any material defects (such as cracks that need to be detected) will not receive light inside the semiconductor device and will appear as dark areas on the diffused light device side, resulting in high contrast.

[0039] One important technical aspect of the present invention is that the edges of semiconductor devices are not precise or clean (due to the dicing process of the semiconductor device); therefore, light will not travel in a straight line and predictably through the semiconductor device, but rather will be scrambled, resulting in a diffuse illuminator. Another important technical aspect is that by viewing only the side, the area to be inspected is significantly smaller than if the entire device were viewed (with an "IR backside view" or "five-sided solution"), providing the opportunity to improve resolution (capture smaller defects) and perform faster inspections (because the image is still significantly smaller than with other methods).

[0040] In one embodiment, illumination light is applied to one side of a semiconductor device; the light propagates through the device because the edge is bare silicon (from the dicing process). Because the edge of the device is rough (due to the dicing process), the light will not travel in a straight line through the device. Upon reaching the other side of the semiconductor device, the light incident at a small angle (less than approximately 17°) will be transmitted out of the semiconductor device. Light with angles of ±90° will cause the edge of the semiconductor device to shine like a diffuse illuminator. In contrast, when an internal defect or side crack is encountered, normal light propagation is blocked, resulting in a 'defect-like' area in the diffuse illuminator, which in turn appears as a high-contrast dark spot in the camera image. A typical example of a crack is a disturbance within the silicon structure. Light is reflected by this disturbance and does not propagate. Therefore, light passing through this area will not be captured by the camera.

[0041] The same principle is used in another embodiment for performing semiconductor device inspection. In this embodiment, IR light is illuminated within the semiconductor device to provide an "angled side view." The IR light is transmitted into the sample at an angle. The light is blocked by internal cracks, altering the normally diffuse illumination from rough edges. This angled side view not only provides high resolution, but also allows for faster inspection. Individual internal or side defects appear larger and with higher contrast because the defects block normal internal light propagation. The diffuse IR light emitted from the semiconductor device is less sensitive to external contamination, increasing the signal-to-noise ratio for any defects present.

[0042] By moving the focal point into the semiconductor device, internal defects far from its edge can be resolved, even allowing scanning inside the completed semiconductor device.

[0043] According to the method of the present invention, illumination light from at least one light source is directed toward one side of the workpiece, and the light exiting the far side of the workpiece is imaged by a camera, preferably with a lens, onto a line sensor.

[0044] Another embodiment of the invention involves directing illumination light from at least one light source onto a top surface of a workpiece, and a camera using a lens to image the light emanating from the top surface of the workpiece, preferably using a lens to image the light emanating from the top surface of the workpiece onto a line sensor.

[0045] In a further embodiment of the present invention, an optical setup simultaneously generates a line image of light emerging from a side of a workpiece and a line image of light emerging from a portion of the top surface of the workpiece, the portions of the top surface being detected being adjacent to each side of the workpiece.

[0046] According to one embodiment of the method of the present invention, there is a way to move the stage to image separate portions of at least two side and top surfaces of the workpiece. a) performing a linear relative motion between the stage with the workpiece and the camera such that the image plane of the camera is parallel to one of the sides; b) rotating the stage together with the workpiece; c) repeating steps a) and b) until all sides of the workpiece have been imaged by the camera; It has.

[0047] The linear relative motion between the stage and the camera can be achieved by linear motion of the camera alone. The linear motion of the camera is directed in opposite directions between rotation steps.

[0048] According to a further embodiment of the method of the present invention, there is a way to move a stage to image separate portions of at least two side and top surfaces of a workpiece, the method including performing XY plane movement of the stage in parallel with rotating the stage so that the focal point of the camera remains on the separate side surfaces during the rotational movement of the stage.

[0049] According to a further aspect of the present invention, there is provided a computer program product disposed on a non-transitory computer-readable medium for detecting defects in a workpiece, the computer program product controlling a computer to execute computer-executable process steps constituting the product, the computer program product comprising: Place the workpiece on the stage, Illuminating at least one surface of the workpiece with illumination light in a wavelength range in which the workpiece is transparent; an optical setup directing light from at least one surface of the workpiece onto at least one line sensor in a camera to image a line of light from the at least one surface of the workpiece; and moving a stage holding the workpiece so that at least one side of the workpiece is completely imaged by the line sensor of the camera and is located at the focal point of the camera during the movement of the stage; What is possible is provided.

[0050] As described above, one embodiment of the method of the present invention uses a line scan camera perpendicular to the side of the semiconductor device. Images are generated by moving the semiconductor device on an XYθ stage. Custom optics are used to generate simultaneous views of at least a portion of the side and top of the semiconductor device. This optical setup also allows for coaxial and external illumination, with the illumination for these two modes being either identical or independent. The line scan camera setup ensures high-resolution images that would otherwise be impossible with an area scan camera. Combining these two views of at least one side and the top surface results in a significantly more informative image, one that can pinpoint the exact location and origin of defects on the semiconductor device. Integration onto a moving stage setup allows for high-speed inspection while receiving two high-resolution views.

[0051] The embodiment with a line sensor camera has a unique advantage: since two views are combined, there is no need to capture two images with separate cameras. Furthermore, by combining two views, the information can be corrected through image processing, taking into account the view that leads to a high capture rate suitable for defects and the view that leads to a low discomfort level suitable for noise. The use of a line scan camera allows the generation of images with a higher resolution than a regular matrix camera.

[0052] The semiconductor devices being tested are typically used in mobile devices. Because the sidewall cracks mentioned above result in customer returns and high costs for device manufacturers, device manufacturers are under strong customer pressure to perform automated testing to detect these sidewall defects. Furthermore, devices with such defects may pass electrical testing, but often fail prematurely in the field (e.g., when a mobile phone is dropped). As explained above, the current methodology is clearly inadequate because it can miss defects in semiconductor devices (which are a risk associated with customer returns) while rejecting good devices due to minor defects (which result in financial losses for manufacturers).

[0053] The present invention and its advantages will be further explained below with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0054] [Figure 1] FIG. 1 illustrates a conventional setup for detecting internal defects by viewing the side of a semiconductor device. [Figure 2] FIG. 2 is a schematic diagram of an image obtained with the setup shown in FIG. 1. [Figure 3] FIG. 1 illustrates a conventional setup for detecting internal defects by viewing onto the top surface of a semiconductor device. [Figure 4] FIG. 4 is a schematic diagram of an image obtained with the setup shown in FIG. 3. [Figure 5] 1 is a schematic diagram of an arrangement for performing inspection of semiconductor devices with IR illumination in a side view with backlight illumination. [Figure 6] 1 is a schematic diagram of an arrangement for performing inspection of a semiconductor device with IR illumination and a side view with dark field illumination. [Figure 7] FIG. 1 is a schematic diagram of an arrangement for inspecting semiconductor devices with IR illumination and angled side view with backlight illumination. [Figure 8]1 is a schematic diagram of an arrangement for performing edge inspection of a semiconductor device with IR illumination in a side view and performing a scanning motion of the semiconductor device. [Figure 9] 1 is a schematic diagram of an arrangement for performing edge inspection of a semiconductor device with IR illumination in a top view and performing a scanning motion of the semiconductor device. [Figure 10] 1A-1C illustrate an embodiment of an arrangement for simultaneously performing side and top views of a semiconductor device. [Figure 11] FIG. 2 is a perspective view of an arrangement implementing a side view of one side of a semiconductor device. [Figure 12] FIG. 1 is a detailed view of the opto-mechanical integration of side-view and top-view inspection of semiconductor devices. [Figure 13A] 1A-1C are schematic diagrams of embodiments of linear and rotational scan modes of a semiconductor device. [Figure 13B] 1A-1C are schematic diagrams of embodiments of linear and rotational scan modes of a semiconductor device. [Figure 13C] 1A-1C are schematic diagrams of embodiments of linear and rotational scan modes of a semiconductor device. [Figure 13D] 1A-1C are schematic diagrams of embodiments of linear and rotational scan modes of a semiconductor device. [Figure 13E] 1A-1C are schematic diagrams of embodiments of linear and rotational scan modes of a semiconductor device. [Figure 14] 1 is a schematic diagram of an embodiment of a linear-rotational combined scanning motion of a semiconductor device. DETAILED DESCRIPTION OF THE INVENTION

[0055] In the figures, like or similarly functional elements are designated by like reference numerals. Furthermore, for clarity, only the reference numerals necessary to discuss each figure are shown in that figure. The methods and apparatus described herein are advantageously employed in conjunction with IR light for defect inspection in semiconductor devices. Typically, IR light will be used so that it can penetrate into the silicon of the semiconductor device. Other light source wavelengths may be used in other embodiments of the invention. The only prerequisite is that the material of the workpiece (semiconductor device) being inspected must be transparent in the wavelength range used. While the following description refers to semiconductor devices, this should not be understood as a limitation of the invention. As will be apparent to those skilled in the art, the principles and concepts of the invention are applicable to any inspection of workpieces for internal or side defects. The application of the invention to semiconductor devices should not be considered a limitation.

[0056] FIG. 5 shows a schematic representation of an array 20 for performing inspection of a semiconductor device 2 with IR light 13. The array 20 is a backlit, side-view array. IR light 13 generated by a light source 18 is normally incident on one selected side surface 31, 32, 33, or 34 of the semiconductor device 2. The IR light 13 may be non-collimated or non-normally incident on one selected side surface 31, 32, 33, or 34 of the semiconductor device 2. With the illustrated array 20, the IR light 13 traveling within the semiconductor device 2 can be used to generate an image of the defects 9. An advantage of using IR light 13 is that it can locate internal defects 9 and / or improve the signal-to-noise ratio for individual defects 9 in the semiconductor device 2.

[0057] Camera 6 uses its lens 7 to directly view one selected side surface 31, 32, 33, or 34 of semiconductor device 2. Due to the high refractive index of silicon (n=3.5 at λ=1200 nm) and the rough edges of semiconductor device 2, nearly all of the IR light 13 will be incident on semiconductor device 2. The IR light 13 rays will travel at a small angle through semiconductor device 2 and emerge as diffused rays 21 at the opposite side surface 31, 32, 33, or 34. In this configuration, semiconductor device 2 itself acts like a diffuse illuminator. However, upon reaching an internal defect 9 or a side crack, normal light propagation is blocked, resulting in a 'defect-like' area in the diffused illumination. The blocked IR light 13 is indicated by dashed arrows 22. When each of the side surfaces 31, 32, 33, and 34 is imaged by the lens 7 and camera 6, the internal defect 9 appears as a high-contrast dark section in the camera image. The crack or internal defect 9 is typically a disturbance within the silicon structure of the semiconductor device 2. The IR light 13 is reflected by the disturbance and does not propagate. Therefore, light passing through the site of the internal defect 9 will not be captured by the detector 26 in the camera 6.

[0058] 6 shows another embodiment of an arrangement 20 for inspecting a semiconductor device 2 with IR light 13. In this embodiment, inspection of the semiconductor device 2 is performed with IR light 13 from a light source 18. A camera 6 and associated lens 7 are arranged such that a dark field image of each side 31, 32, 33 or 34 of the semiconductor device 2 is aligned and recorded by the camera 6. At the second surface 32, the direction 23 of IR light propagation is perpendicular to the optical axis 24 of the lens 7 of the camera 6.

[0059] FIG. 7 illustrates a further embodiment of an array 20 of the present invention. IR light 13 is transmitted from a light source 18 to the top surface 4 of a semiconductor device 2 and into the interior of the semiconductor device 2 at an angle α. The IR light 13 propagates through the semiconductor device 2 and is focused onto one of the side surfaces 31, 32, 33, and 34 of the semiconductor device 2, respectively. An internal crack or defect 9 blocks the IR light 13 and alters the normally diffuse illumination from one of the rough side surfaces 31, 32, 33, and 34 (see FIG. 5 ). The array illustrated in FIG. 7 not only provides high resolution but also enables rapid inspection of one of the side surfaces 31, 32, 33, and 34 of the semiconductor device 2 (here, the fourth side surface 34 is being inspected). Individual internal or side surface defects 9 appear larger and with higher contrast in the image captured by the camera 6 because they block normal internal light propagation. The diffuse IR light 33 emitted from the semiconductor device 2 is less sensitive to external contamination of the semiconductor device 2, thereby increasing the signal to noise ratio for any defects 9 present.

[0060] As a useful alternative, the focus of the IR light 13 can be moved into the semiconductor device 2, making it possible to resolve internal defects 9 that are far away from the sides 31, 32, 33 and 34 of the semiconductor device 2. This may even allow scanning into the completed semiconductor device 2.

[0061] 8 shows a schematic representation of a further embodiment of the array 20 of the present invention. The camera 6 has a line sensor 36, and a line 35 of one of the sides 31, 32, 33, or 34 is imaged onto the line sensor 36 by the lens 7. The camera 6 is configured as a line scan camera. The camera 6 is moved along a scanning direction 37. This movement can be achieved by relative movement between the respective side 31, 32, 33, or 34 of the semiconductor device 2 and the camera 6, in particular, along the scanning direction 37 perpendicular to the line 35 to be imaged on the line sensor 36. This relative movement between the respective side 31, 32, 33, or 34 of the semiconductor device 2 and the camera 6 should not be construed as a limitation of the present invention. It will be apparent that only the camera or only the semiconductor device may be moved.

[0062] The semiconductor device 2 is placed on an XYθ stage (not shown). This XYθ stage is moved so that images of all four sides 31, 32, 33, or 34 are generated by the line sensor 36 of the camera 6. In the embodiment shown, the semiconductor device 2 is composed of an additional bulk semiconductor layer 40 (BSL), a silicon substrate 41, a dielectric layer 42, and a metal layer 43. The line scan camera setup allows for high-resolution images that would otherwise be impossible with an area scan camera. For a side view (similar to the arrangement of FIG. 5 ), external IR light 13 is shone into the semiconductor device 2 (die) from a light source 18. This IR light 13 arrives from one side 31, 32, 33, or 34 of the semiconductor device 2 and is captured by the line scan camera 6 at the opposite side 31, 32, 33, or 34 of the semiconductor device 2. A high-resolution image is generated from each side 31, 32, 33, or 34 of the semiconductor device 2. A wavelength range is used to illuminate the interior of the semiconductor device 2, which is transparent to the semiconductor device 2. In a typical semiconductor device 2 (or die) this would be IR light 13.

[0063] FIG. 9 is a schematic diagram of an arrangement 20 for performing edge inspection of a semiconductor device 2 with IR illumination from a side view and for performing a scanning motion of the semiconductor device 2. In this arrangement, the camera 6 also includes a line sensor 36, and a line 35 on the top surface 4 near one of the sides 31, 32, 33, or 34 is imaged onto the line sensor 36 by a lens 7. A beam splitter 27 directs IR light 13 from the light source 18 onto the top surface 4 of the semiconductor device 2. Coaxially returned IR light 34 from the top surface 4 of the semiconductor device 2 is captured by the line sensor 36 of the camera 6. Again, the motion of the semiconductor device 2 along the scanning direction 37 is perpendicular to the line 35 imaged on the line sensor 36 of the camera 6. This motion of the semiconductor device 2 allows a top view of an edge portion 30 of the top surface 4 of the semiconductor device 2, i.e., a portion near one of the sides 31, 32, 33, or 34, to be generated. In FIG. 9, an edge portion 30 of the top surface 4 is adjacent to a fourth side 34 of the semiconductor device 2 .

[0064] The embodiment shown in Figure 10 illustrates an arrangement 20 for simultaneous side view and top view inspection of a semiconductor device 2. A special optical setup 25 is provided that allows simultaneous viewing of one of the side surfaces 31, 32, 33 or 34 and the top surface 4 of the semiconductor device 2. The optical setup 25 also allows illumination of one of the side surfaces 31, 32, 33 or 34 (external illumination) and illumination of the top surface 4 (coaxial illumination) of the semiconductor device 2. The light sources for the two illumination modes (coaxial illumination and external illumination) can be the same or separate.

[0065] By combining views of the side surface 31, 32, 33 or 34 and the top surface 4 of the semiconductor device 2, the exact location and origin of the defect can be extracted, since the image of the top surface 4 and the image of the side surface 31, 32, 33 or 34 contain significantly more information. Integration onto a moving stage setup allows for high speed inspection as well as two high resolution views.

[0066] The array 20 and special optical setup 25 can generate a simultaneous view of one side 31, 32, 33 or 34 of the semiconductor device 2 and an edge portion 30 of the top surface 4 (see FIG. 9), as shown in FIG. 10. In addition, two separate line sensors 36 are provided: one is used to capture an image of a portion of the top surface 4, and the other is used to capture an image of one of the side surfaces 31, 32, 33 or 34 adjacent to the top surface 4.

[0067] According to the embodiment shown, light guides 50 are used to carry IR light 13. The light guides 50 are positioned as close as possible to the semiconductor device 2 so as to illuminate the edge portion 30 of the top surface 4 and one of the adjacent side surfaces 31, 32, 33 or 34 with IR light 13.

[0068] FIG. 11 shows a perspective view of an apparatus for performing a side view of at least one of the sides 31, 32, 33, or 34 of a semiconductor device 2. The semiconductor device 2 (not shown here) is placed on a holder with a chuck 45. The chuck 45 is mounted on a θ stage 38, which can move linearly at least along the X coordinate direction X and the Y coordinate direction Y. In addition, the θ stage 38 can be tilted. Linear movement along the Z coordinate direction Z can also be integrated. The light source 18 directs illumination light 13 toward the semiconductor device 2 on the chuck 45. In the embodiment shown here, the light sources 18 are arranged so that one side 31, 32, 33, or 34 of the semiconductor device 2 is illuminated. This arrangement of the light sources 18 is called a backlight arrangement.

[0069] Opposite the light source 18, an array 20 with an optical setup 25 is arranged to receive light emitted from one side 31, 32, 33 or 34 of the semiconductor device 2, in particular from the side of the semiconductor device 2 opposite the illuminated side 31, 32, 33 or 34. The optical setup 25 is located at a tip 39 of the array 20. The array 20 is connected to a computer 32 which receives image data from the array 20. In addition, the computer 32 is connected to a controller 31 which moves a stage 38 so that each side 31, 32, 33 or 34 can be scanned by the array 20.

[0070] FIG. 12 shows a detailed view of the optical setup 25 of the array 20. This optical setup 25 enables simultaneous side-view and top-view inspection of the semiconductor device 2. In the illustrated embodiment, the optical setup 25 simultaneously generates a line-of-light image emerging from the side surface 31, 32, 33, or 34 of the semiconductor device 2 and a line-of-light image emerging from at least a portion of the top surface 4 of the semiconductor device 2. As previously mentioned, the line-of-light from the top surface 4 is located adjacent to the line-of-light from each of the side surfaces 31, 32, 33, or 34 of the semiconductor device 2. The top end 39 of the optical setup 25 carries an upper mirror 51, a first lower mirror 52, and a second lower mirror 53. The upper mirror 51 captures a line-of-light image from a portion of the top surface 4 of the semiconductor device 2. The first lower mirror 52 and the second lower mirror 53 are arranged at the top end 39 of the optical setup 25 so as to capture the line-of-light image emerging from the side surface of the semiconductor device 2. The optical setup 25 is designed so that the line of light image emitted from the side surface 31, 32, 33 or 34 of the semiconductor device 2 and the line of light image from the top surface 4 of the semiconductor device 2 are simultaneously in focus. The optical coupling is such that the light path 54 via the upper mirror 51 and the light path 55 via the first lower mirror 52 and the second lower mirror 53 can be illuminated separately.

[0071] 13A-13E show a process for inspecting the four side surfaces 31, 32, 33, and 34 and / or the edge portion 30 of the top surface 4. When inspecting the four side surfaces 31, 32, 33, and 34 and the edge portion 30 of the top surface 4, i.e., the portion adjacent to each side surface 31, 32, 33, or 34, a combined side view and top view image is obtained. The stage 38 executes a motion profile as described in the embodiment of FIGS. 13A-13E. In FIG. 13A, a semiconductor device 2 is placed on the stage 38. As described above, the semiconductor device 2 may also be held by a chuck (not shown here) that is itself mounted on the stage 38 (the θ stage).

[0072] In FIG. 13B , the first side surface 31 is parallel to the image plane 44 of the camera 6. A linear relative motion 46 is performed between the stage 38 carrying the semiconductor device 2 and the camera 6. During this motion 46, the image plane 44 of the camera 6 is kept parallel to the first side surface 31. After scanning of the first side surface 31 is completed, the stage 38 is rotated 90° clockwise, so that the second side surface 32 of the semiconductor device 2 becomes parallel to the image plane 44 of the camera 6 (see FIG. 13C ). As shown in FIG. 13C , a linear relative motion 46 in the opposite direction is performed between the stage 38 carrying the semiconductor device 2 and the camera 6. During this motion 46, the image plane 44 of the camera 6 remains parallel to the second side surface 32. After scanning of the second side surface 32 is completed, the stage 38 is rotated 90°, so that the third side surface 33 of the semiconductor device 2 becomes parallel to the image plane 44 of the camera 6 (see FIG. 13D ). As shown in Figure 13D, a linear relative motion 46 is performed between the stage 38 carrying the semiconductor device 2 and the camera 6. During this motion 46, the image plane 44 of the camera 6 is parallel to the third side surface 33. After scanning of the third side surface 33 is completed, the stage 38 is rotated by 90°, and the fourth side surface 34 of the semiconductor device 2 becomes parallel to the image plane 44 of the camera 6 (see Figure 13E). As shown in Figure 13E, a linear relative motion 46 in the opposite direction is performed between the stage 38 carrying the semiconductor device 2 and the camera 6. During this motion 46, the image plane 44 of the camera 6 is parallel to the fourth side surface 34.

[0073] As mentioned above, the array 20 and the special optical setup 25 can also image the edge portions 30 of the top surface 4 of the semiconductor device 2, i.e., the edge portions 30 adjacent to each side surface 31, 32, 33 or 34 of the semiconductor device 2 (see Figure 9).

[0074] 14A-14F illustrate a further embodiment of a process for scanning at least four sides 31, 32, 33, and 34 of a semiconductor device 2. The motion of the stage (not shown) and the semiconductor device 2 respectively comprises a rotational motion 56 about a center 58 of the semiconductor device 2 and a linear motion 57 of the semiconductor device 2 in an XY plane defined by an X coordinate direction X and a Y coordinate direction Y. FIG. 14A illustrates the start of the process for scanning the four sides 31, 32, 33, and 34 of the semiconductor device 2. A focal point 59 of a camera (not shown) is located on the first side 31. FIG. 14B illustrates the beginning of the rotational motion 56. The center 58 of the semiconductor device 2 is simultaneously subjected to a motion 57 in the XY plane, and the focal point 59 remains on the first side 31 during the rotational motion 56. FIGS. 14C-14E ​​illustrate various stages of the rotational motion 56 of the semiconductor device 2, during which the focal point 59 remains on the second side 32. FIG. 14F shows the situation where the focal point 59 reaches the third side surface 33, and the focal point 59 remains on the third side surface 33 during the rotational movement 56 of the semiconductor device 2.

[0075] 11 coordinates rotational motion 56 with simultaneous XY plane motion 57 so that when semiconductor device 2 has completed a 360° rotation, all four sides 31, 32, 33, and 34 have been imaged by array 20. Furthermore, computer 32 ensures that focal point 59 remains on all four sides 31, 32, 33, and 34 during the full 360° rotation, thereby providing high quality images of all four sides 31, 32, 33, and 34.

[0076] It is believed that the disclosed apparatus, method, and computer program, and many of its attendant advantages, will be understood from the foregoing description, and it will be apparent that various changes can be made in the form, construction, and arrangement of the elements without departing from the disclosed subject matter or sacrificing all of its important advantages. The described forms are merely examples.

[0077] The above description sets forth numerous specific details to provide a thorough understanding of embodiments of the present invention. However, the above description of exemplary embodiments of the present invention is not intended to be exhaustive or to limit the present invention to the precise form disclosed. Those skilled in the relevant art will recognize that the present invention can be practiced without one or more specific details or with other methods, components, etc. Additionally, well-known structures or operations have not been shown or described to avoid obscuring aspects of the present invention. While specific embodiments and examples of the present invention have been described herein for illustrative purposes, those skilled in the art will recognize that various equivalent modifications are possible within the scope of the present invention.

[0078] Such modifications can be made to the present invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the present invention is to be defined by the following claims, which are to be interpreted in accordance with established doctrines of claim interpretation. [Explanation of symbols]

[0079] 2 Workpiece, semiconductor device, 31 First side, 32 Second side, 33 Third side, 34 Fourth side, 4 Top surface, 5 Bottom surface, 6 Camera, 7 Lens, 8 Mirror, 9 Defect, internal defect, 10 Image, 11 Optical length, 12 Optical length, 13 IR light, illumination light, 14 Optical system, 15 Returned IR light, 16 Schematic image, 18 Light source, 19 Defect, 20 Array, 21 Diffused light beam, 22 Dashed arrow, 23 Direction of light propagation, 24 Optical axis, 25 Special optical setup, 26 Detector, 27 Beam splitter, 30 Edge portion, 31 Controller, 32 Computer, 33 Diffused IR light, 34 Returned IR light, 35 Line, 36 Line sensor, 37 Scan direction, 38 Stage, θ stage, 39 Tip, 40 Bulk semiconductor layer, 41 Silicon substrate, 42 dielectric layer, 43 metal layer, 44 image plane, 45 chuck, 46 linear relative motion, 50 optical waveguide, 51 upper mirror, 52 first lower mirror, 53 second lower mirror, 54 optical path, 55 optical path, 56 rotational motion (note Figure 10), 57 motion, 58 center, 59 focus, XX coordinate direction, YY coordinate direction, ZZ coordinate direction, α angle.

Claims

1. 1. A method for detecting defects in a semiconductor device, comprising: generating illumination in a wavelength range; directing a portion of the illumination through a top surface of the semiconductor device at an oblique angle relative to the top surface of the semiconductor device, wherein the illumination propagates within the semiconductor device toward a side surface of the semiconductor device, and the side surface is inspected for one or more defects; collecting, by a camera, illumination emitted from the semiconductor device; A method comprising:

2. The method of claim 1 , wherein the camera comprises a lens and a detector.

3. 3. The method of claim 2, wherein the detector includes one or more sensors, and the camera images the illumination emitted from the top surface of the semiconductor device through the lens onto the one or more sensors.

4. 10. The method of claim 1, The method further includes generating, with an optical system, an image of illumination emerging from a side of the semiconductor device.

5. 5. The method of claim 4, wherein the optical system is configured such that an image captured from the side of the semiconductor device and an image from the top surface of the semiconductor device are simultaneously in focus.

6. 10. The method of claim 1, The method further comprising coupling illumination from at least one light source separately into a side surface of the semiconductor device and a top surface of the semiconductor device.

7. 10. The method of claim 1, wherein an optical waveguide is disposed between a light source and at least one of a top surface and a side surface of the semiconductor device.

8. The method of claim 1 , wherein the wavelength range of the illumination includes infrared light.

9. The method of claim 1 , wherein the semiconductor devices comprise singulated semiconductor devices.

10. 1. An apparatus for detecting defects in a semiconductor device, comprising: at least one light source configured to provide illumination in a wavelength range, the at least one light source configured to direct a portion of the illumination through a top surface of the semiconductor device at an oblique angle relative to the top surface of the semiconductor device, the illumination propagating within the semiconductor device toward a side surface of the semiconductor device, the side surface being inspected for one or more defects; an optical system including a camera configured to collect the illumination emitted from the semiconductor device; An apparatus comprising:

11. 11. The apparatus of claim 10, wherein the camera is configured to image one or more defects in the semiconductor device based on the collected illumination emitted through the top surface of the semiconductor device.

12. 11. The apparatus of claim 10, wherein the at least one light source is arranged such that the illumination emitted from the top surface of the semiconductor device is coaxial with the illumination directed toward the top surface of the semiconductor device.

13. 11. The apparatus of claim 10, further comprising a light guide configured to guide the illumination from the at least one light source to each side of the semiconductor device.

14. 11. The apparatus of claim 10, wherein the camera comprises a lens and one or more sensors.

15. 11. The apparatus of claim 10, further comprising an optical system configured to form one or more images with illumination emitted from a side of the semiconductor device.

16. 16. The apparatus of claim 15, wherein a tip of the optical system includes one or more mirrors that collect illumination from a portion of the top surface of the semiconductor device and illumination emitted from a side of the semiconductor device.

17. 11. The apparatus of claim 10, wherein the semiconductor devices comprise singulated semiconductor devices.

18. 11. The apparatus of claim 10, wherein the wavelength range of the illumination includes infrared light.

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