Wafer crack defect system and detection method

Abstract

The application discloses a wafer hidden crack defect detection method, which comprises a prism camera; a microscopic imaging system is arranged below the prism camera; an illumination system is arranged on one side of the microscopic imaging system; a time modulation illuminator is arranged on one side of the illumination system; an object plane is arranged at the bottom of the microscopic imaging system; a fiber head is arranged at the end of the time modulation illuminator; and a color filter wheel is arranged at the end of the fiber head. By adopting the specially customized time modulation illuminator, light rays with different light incidence angles are color-coded, and the specially customized field stop of the imaging system is combined to complete the detection of different inclination angles of the upper surface of the wafer caused by the hidden crack defect, so that the wafer hidden crack defect detection is realized.

Description

Technical Field

[0001] This invention relates to the field of wafer defect detection technology, and more specifically, to a wafer microcrack defect system and detection method. Background Technology

[0002] The miniaturization of wafer feature sizes is a direct result of the rapid development in integrated circuit manufacturing. However, defects arise during processing due to incomplete processes and insufficient equipment maintenance, which can fatally impact wafer yield. Efficiently and accurately detecting these minute defects on wafers remains a challenge, making defect detection technology a key technology in the silicon semiconductor integrated circuit field.

[0003] Every die in a wafer needs to be tested to ensure the good performance of each chip manufactured. Defect detection includes visible and invisible defects (internal defects). Internal defects typically manifest as non-penetrating microcracks, which may be caused by cutting force damage during wafer dicing or uneven thermal stress within the die. Small microcracks render the die unusable for high-end chip manufacturing; more severe microcracks can lead to die breakage, causing process failures and significant cost losses. Existing detection technologies for microcrack defects in semiconductor wafers are generally divided into non-destructive and destructive methods, such as X-ray, UV, IR optical imaging, and scanning electron microscopy analysis after wafer dicing and grinding. Non-destructive microcrack defect detection is time-consuming and inefficient, while destructive microcrack defect detection is costly and inefficient. Summary of the Invention

[0004] To address at least one of the aforementioned technical problems, this invention proposes a wafer microcrack defect detection system and method.

[0005] The first aspect of this invention provides a wafer microcrack defect detection system, comprising: a prism camera;

[0006] A microscopic imaging system is provided below the prism camera, an illumination system is provided on one side of the microscopic imaging system, and a time-modulated illuminator is provided on one side of the illumination system.

[0007] The bottom of the microscopic imaging system is provided with an object surface;

[0008] The time-modulated illuminator is provided with an optical fiber head at one end, and a color filter wheel is provided at the other end of the optical fiber head.

[0009] In a preferred embodiment of the present invention, the microscopic imaging system includes a tube lens and a microscope objective lens, wherein an imaging field diaphragm is disposed below the tube lens and an illumination field diaphragm is disposed above the microscope objective lens.

[0010] In a preferred embodiment of the present invention, a relay lens and a beam splitter are disposed between the imaging field stop and the illumination field stop.

[0011] In a preferred embodiment of the present invention, a plurality of optical fibers are disposed inside the optical fiber head, and the plurality of optical fibers are evenly distributed along the circumference of the optical fiber head.

[0012] In a preferred embodiment of the present invention, the optical fiber includes at least one central optical fiber and a plurality of peripheral optical fibers, the angle between two adjacent peripheral optical fibers is the same, and the peripheral optical fibers are disposed outside the central optical fiber.

[0013] In a preferred embodiment of the present invention, the peripheral optical fibers are divided into at least two groups, with different groups of peripheral optical fibers interleaved, and the angle between two adjacent peripheral optical fibers in the same group is the same.

[0014] In a preferred embodiment of the present invention, the color filter wheel has a hole in the middle, and two sets of R color filters, G color filters and B color filters are arranged at intervals on the outside of the hole.

[0015] A second aspect of the present invention provides a method for detecting microcracks in wafers, the method comprising the following steps:

[0016] S1, sequentially illuminate the two sets of peripheral optical fibers of the time-modulated illuminator, and obtain R, G, and B spectral outputs at three different illumination azimuth angles through the color filter wheel;

[0017] S2, the imaging end corresponds to the R, G, and B prism camera sensor chips respectively, to obtain independent imaging of the R, G, and B light three channels;

[0018] S3, the central optical fiber of the time-modulated illuminator is lit, and independent imaging of the three channels of R, G and B light is obtained through the imaging end;

[0019] S4. Light from the upper surface of the wafer with hidden cracks is received through the imaging field stop, forming a bright field image; the image without hidden cracks forms a dark field image.

[0020] S5. Generate hidden crack defect detection information based on the contrast information of bright and dark gray levels of bright field and dark field.

[0021] In a preferred embodiment of the present invention, step S1, "obtaining R, G, and B spectral outputs at three different illumination azimuth angles through a color filter wheel," specifically includes:

[0022] By installing filters at the front end of the optical fiber head, the color of light at different illumination azimuth angles is encoded, and the color light at the optimal illumination azimuth angle is obtained based on wavelength reflectivity characteristics.

[0023] The technical solution of the present invention has the following advantages compared with the prior art:

[0024] Based on bright-field illumination, this invention employs a specially customized time-modulated illuminator, which uses a peripheral optical fiber with a small aperture and a six-color filter wheel to color-code light rays at different illumination azimuth angles with a large tilt angle θ1, and a central optical fiber with a large aperture to illuminate the azimuth angle of the microcrack defect with a small tilt angle θ2. Simultaneously, combined with a customized field-of-view aperture of the imaging system, this invention completes the detection of different tilt (protrusion) angles on the wafer's upper surface caused by microcrack defects, thereby achieving the detection of microcrack defects on the wafer. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the optical system of the wafer microcrack defect detection system according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the fiber optic head structure according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the color filter wheel structure according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the field stop of the imaging system according to an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of a microcrack inside a wafer according to an embodiment of the present invention;

[0031] Figure 6 This is a cross-sectional view of a microcrack inside a wafer according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram illustrating the detection principle of a large tilt angle θ1 according to an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram of the small tilt angle θ2 detection principle in an embodiment of the present invention.

[0034] In the figure, 1. Time-modulated illuminator, 2. Illumination system, 3. Microscopic imaging system, 4. Prism camera, 5. Fiber optic head, 6. Object plane, 7. Microscope objective, 8. Illumination field stop, 9. Beam splitter, 10. Relay lens, 11. Imaging field stop, 12. Tube lens. Detailed Implementation

[0035] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention.

[0037] However, the present invention may also be implemented in other ways different from those described herein.

[0038] Therefore, the scope of protection of this invention is not limited to the specific embodiments disclosed below.

[0039] Example 1

[0040] See Figure 1-8 As shown, the present invention proposes a wafer microcrack defect detection system, including: a prism camera 4;

[0041] A microscopic imaging system 3 is provided below the prism camera 4, an illumination system 2 is provided on one side of the microscopic imaging system 3, and a time-modulated illuminator 1 is provided on one side of the illumination system 2.

[0042] The bottom of the microscopic imaging system 3 is provided with an object surface 6;

[0043] The time-modulated illuminator 1 is equipped with an optical fiber head 5 at one end, and a color filter wheel is provided at the other end of the optical fiber head 5.

[0044] Specifically, the time-modulated illuminator 1 consists of a seven-hole optical fiber and a six-color filter wheel, as shown below. Figure 2 and Figure 3 As shown, after passing through the illumination system 2, the image reaches the object plane 6 via the entrance pupil position of the microscope objective lens 7 (i.e., the illumination field stop 8 of the illumination system 2) through the beam splitter 9. Then, the conjugate image of the field stop is imaged onto the imaging field stop 11 of the imaging system (e.g., the image of the object plane 6) by the relay lens 10. Figure 4 As shown), it finally reaches the target surface of the 3CMOS beam splitter camera 4 through the lens barrel 12.

[0045] According to an embodiment of the present invention, the microscopic imaging system 3 includes a tube lens 12 and a microscope objective lens 7. An imaging field stop 11 is provided below the tube lens 12, and an illumination field stop 8 is provided above the microscope objective lens 7.

[0046] According to an embodiment of the present invention, a relay lens 10 and a beam splitter 9 are disposed between the imaging field stop 11 and the illumination field stop 8.

[0047] According to an embodiment of the present invention, a plurality of optical fibers are disposed inside the optical fiber head 5, and the plurality of optical fibers are evenly distributed along the circumference of the optical fiber head 5.

[0048] According to an embodiment of the present invention, the optical fiber includes one central optical fiber and six peripheral optical fibers, the angle between two adjacent peripheral optical fibers is 60 degrees, and the peripheral optical fibers are disposed outside the central optical fiber.

[0049] According to an embodiment of the present invention, the peripheral optical fibers are divided into two groups, and the two groups of peripheral optical fibers are staggered. The angle between the two peripheral optical fibers in the same group is 120 degrees.

[0050] Similarly, when the peripheral optical fibers are divided into two or more groups, the multiple groups of peripheral optical fibers are also interspersed, and the angle between the two peripheral optical fibers in the same group is the same.

[0051] Specifically, the seven-hole fiber optic connector 5 is a specially customized design, such as... Figure 2-3 As shown, fibers 1-1, 1-2, 1-3, 2-1, 2-2, and 2-3 are small-aperture white optical fibers used for modulation illumination of microcracks with a large tilt angle θ1. Furthermore, fibers 1-1, 1-2, and 1-3 are simultaneously illuminated, with R, G, and B color filters at the front end of fiber optic connector 5, producing corresponding R, G, and B spectra. Similarly, fibers 2-1, 2-2, and 2-3 are simultaneously illuminated, corresponding to another set of R, G, and B color filters, producing corresponding R, G, and B spectra. Fiber 3-1 is a large-aperture white optical fiber used for modulation illumination of microcracks with a small tilt angle θ2; fiber optic connector 5 has no color filter at its front end.

[0052] According to an embodiment of the present invention, a hole is provided in the middle of the color filter wheel, and two sets of R color filters, G color filters and B color filters are arranged at intervals on the outside of the hole of the color filter wheel.

[0053] A second aspect of the present invention provides a method for detecting microcracks in wafers, the method comprising the following steps:

[0054] S1, sequentially light up the two sets of peripheral optical fibers of time-modulated illuminator 1, and obtain R, G, B spectrum outputs at three different lighting azimuth angles through the color filter wheel;

[0055] S2, the imaging end corresponds to the R, G, B prism camera 4 sensing chips respectively, to obtain R, G, B light three-channel independent imaging;

[0056] S3, the central optical fiber of the time-modulated illuminator 1 is lit, and independent imaging of the three channels of R, G and B light is obtained through the imaging end;

[0057] S4. Light from the upper surface of the wafer with hidden cracks is received through the imaging field stop 11, forming a bright field; the imaging without hidden cracks forms a dark field.

[0058] S5. Generate hidden crack defect detection information based on the contrast information of bright and dark gray levels of bright field and dark field.

[0059] According to an embodiment of the present invention, step S1, "obtaining R, G, and B spectral outputs at three different illumination azimuth angles through a color filter wheel," specifically includes:

[0060] By installing a filter at the front end of the fiber optic head 5, the color of light at different illumination azimuth angles is encoded, and the color light at the optimal illumination azimuth angle is obtained based on the wavelength reflectivity characteristics.

[0061] Based on bright-field illumination, this invention employs a specially customized time-modulated illuminator 1, which includes a peripheral optical fiber with a small aperture and a six-color filter wheel to color-code light rays at different illumination azimuth angles with a large tilt angle θ1, and a central optical fiber with a large aperture to illuminate the azimuth angle of the microcrack defect with a small tilt angle θ2. Simultaneously, combined with a customized field-of-view aperture of the imaging system, this invention completes the detection of different tilt (protrusion) angles on the wafer's upper surface caused by microcrack defects, thereby achieving the detection of microcrack defects on the wafer.

[0062] Furthermore, Figure 6 The tilting protrusion on the upper surface caused by the microcrack will vary in tilt angle θ depending on the severity of the microcrack defect.

[0063] Optical systems using visible light wavelengths cannot observe the details inside a grain. Detection is achieved by observing the changes in the light reflection angle through tiny protrusions on the upper surface corresponding to microcrack regions. Furthermore, different materials on the grain's upper surface will have varying reflectivities to light sources of different colors and wavelengths.

[0064] (1) The method for detecting microcracks with a large tilt angle θ1 is as follows:

[0065] For the hidden crack defect with a large tilt angle θ1, six small-aperture white light fibers (1-1, 1-2, 1-3, 2-1, 2-2, and 2-3) in the seven-hole fiber of the time-modulated illuminator 1 can be used to illuminate the hidden crack defect at different azimuth angles. Since the defect characteristics show different sensitivities to different illumination azimuth angles, filters are installed at the front end of the six-hole fiber head 5 to achieve color coding of the light at different illumination azimuth angles. Finally, combined with wavelength reflectivity characteristics, the color light at the optimal illumination azimuth angle is obtained.

[0066] The modulated light emitted by the time-modulated illuminator 1 at a large tilt angle θ1 passes through the customized field aperture of the imaging system and receives the light from the upper surface of the wafer where the hidden crack region exists. The imaging forms a bright field, while the imaging without the hidden crack region forms a dark field. Finally, the contrast between the bright and dark gray levels is displayed, and the detection of hidden crack defects at a large tilt angle θ1 is completed.

[0067] (2) The method for detecting microcracks with a small tilt angle θ2 is as follows:

[0068] For microcracks with a small tilt angle θ2, the azimuth angle of the microcracks with a small tilt angle θ2 can be illuminated by using the 3-1 large aperture white optical fiber of the time-modulated illuminator 1.

[0069] The modulated light emitted by the time-modulated illuminator 1 at a small tilt angle θ2 passes through the customized field aperture of the imaging system and receives the light from the upper surface of the wafer where the hidden crack region exists. The imaging forms a bright field, while the imaging without the hidden crack region forms a dark field. Finally, the contrast between the bright and dark gray levels is displayed, and the detection of the hidden crack defect at a small tilt angle θ2 is completed.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the above embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0072] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A wafer crack detection system, comprising: The prism camera is characterized in that, A microscopic imaging system is arranged below the prism camera, one side of the microscopic imaging system is provided with an illumination system, and one side of the illumination system is provided with a time-modulated illuminator; A subject plane is arranged at the bottom of the microscopic imaging system; An optical fiber head is arranged at the end of the time-modulated illuminator, and a color filter wheel is arranged at the end of the optical fiber head; A plurality of optical fibers are arranged in the optical fiber head, and the plurality of optical fibers are uniformly distributed along the circumference of the optical fiber head; The optical fibers include at least one central optical fiber and a plurality of peripheral optical fibers, the angle between any two adjacent peripheral optical fibers is the same, and the peripheral optical fibers are arranged outside the central optical fiber; The peripheral optical fibers are divided into at least two groups, the peripheral optical fibers in different groups are staggered, and the angle between any two adjacent peripheral optical fibers in the same group is the same; A hole is arranged in the color filter wheel, and two groups of R color filters, G color filters and B color filters are arranged outside the hole at intervals; The first group of peripheral optical fibers corresponds to one group of R color filters, G color filters and B color filters, and the second group of peripheral optical fibers corresponds to another group of R color filters, G color filters and B color filters.

2. The wafer crack defect detection system of claim 1, wherein The microscopic imaging system includes a barrel lens and a microscope objective, an imaging field stop is arranged below the barrel lens, and an illumination field stop is arranged above the microscope objective.

3. The wafer crack defect detection system of claim 2, wherein A relay lens and a beam splitter are arranged between the imaging field stop and the illumination field stop.

4. A wafer crack defect detection method characterized by, The wafer hidden crack defect detection method is applied to the wafer hidden crack defect detection system of claim 1, and the wafer hidden crack defect detection method comprises the following steps: S1, sequentially lighting two groups of peripheral optical fibers of the time-modulated illuminator, and obtaining R, G and B spectral outputs of three different light orientation angles through the color filter wheel; S2, the imaging end corresponds to R, G and B prism camera sensing chips respectively, and R, G and B light three-channel independent imaging is obtained; S3, lighting the central optical fiber of the time-modulated illuminator, and obtaining R, G and B light three-channel independent imaging through the imaging end; S4, receiving light rays on the upper surface of the wafer with hidden cracks through the imaging field stop, and forming a bright field by imaging, and forming a dark field by imaging without hidden cracks; S5, based on the bright and dark gray scale contrast information of the bright field and the dark field, hidden crack defect detection information is generated.

5. The method of claim 4, wherein the step of detecting the crack defect is performed by using a method of detecting a crack defect in a wafer by using a light source, a light detector, and a computer. In step S1, the R, G and B spectral outputs of three different light orientation angles are obtained through the color filter wheel, which specifically includes: By installing a filter at the front end of the optical fiber head, the colors of light rays of different light orientation angles are coded, and based on the wavelength reflectivity characteristics, the color light of the best light orientation angle is obtained.

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