High-Precision Inspection Apparatus for Wafer Defect Measurement

Abstract

The present invention relates to a high-precision inspection device for measuring wafer defects that enables the acquisition of a wafer image with high resolution. Since the present invention is formed to block light with unwanted angles using a slit and allow only light parallel to the optical axis to pass through, the light rays incident from the light source through the slit to the wafer are aligned uniformly and consistently, thereby enabling the camera to provide a wafer image with high resolution.

Description

Technology Field

[0001] The present invention relates to a high-precision inspection device for measuring wafer defects, and more specifically, to a high-precision inspection device for measuring wafer defects that enables the acquisition of a wafer image having high resolution by ensuring that light rays incident from a light source onto the wafer are aligned consistently and uniformly. Background Technology

[0003] In the semiconductor manufacturing process, thin film thickness directly affects device performance and production yield. Accurate measurement of thin film thickness is a key element of process control and quality assurance, and more precise measurement technology is required as wafer size increases and critical dimensions decrease.

[0004] Wafers are a core material for semiconductor devices and are essential for the manufacturing of integrated circuits (ICs). With the advancement of semiconductor technology, device sizes have shrunk while performance and integration density have increased, necessitating thinner and more precise wafers. Furthermore, as semiconductor devices become extremely integrated and miniaturized, the impact of microscopic particles that can impair device performance and reliability is becoming more significant. In particular, microscopic contaminant particles generated during thin film deposition and etching processes can cause defects; consequently, managing defects and surface flatness on the wafer surface has become an increasingly critical task.

[0005] In the semiconductor manufacturing process, wafer defect and flatness inspections are classified into point measurement and area measurement methods. Point measurement involves performing measurements at specific points, typically utilizing capacitive sensors. However, this method has limitations in evaluating the uniformity of the entire wafer as it can only measure specific areas. In contrast, area measurement measures the entire surface of the wafer, typically using optical interferometers. This method is preferred by semiconductor manufacturers due to its high precision and ability to measure large areas.

[0007] FIG. 1 is a drawing illustrating a conventional wafer thickness measuring device. Referring to FIG. 1, the conventional wafer thickness measuring device includes a light source unit (10), an objective lens (20), a beam splitter (30), a light receiving lens (40), a slit (50), and a light detection unit (60). The light source unit (10) emits white light, and the objective lens (20) focuses the white light emitted by the light source unit (10) onto a substrate at different focal points. The light focused onto the substrate is scattered or reflected by the substrate and the thin film applied to the substrate. The reflected light passes through the objective lens (20), the beam splitter (30), and the light receiving lens (40), and is then focused linearly at the slit (50). Only the focused light that passes through the slit (50) is detected by the light detection unit (60).

[0008] These conventional technologies are configured to have different focal points using objective lenses, which causes light to spread in multiple directions, making it difficult to accurately measure the thickness of the substrate, i.e., the wafer. Additionally, in conventional technologies, reflected light from the substrate is detected after passing through a slit; however, due to the position of the slit, the light cannot be aligned using the slit before being reflected from the substrate, resulting in a problem where the thickness of the substrate cannot be accurately detected. Prior art literature

[0010] Republic of Korea Published Patent Application No. 10-2021-0009727 The problem to be solved

[0011] The objective of the present invention, which aims to solve the problems of the prior art described above, is to provide a high-precision inspection device for measuring wafer defects that enables the acquisition of a wafer image with high resolution by ensuring that light rays incident from a light source to a wafer are aligned consistently and uniformly. means of solving the problem

[0013] To achieve the above objective, the present invention provides a high-precision inspection device for measuring wafer defects, comprising: a light source unit that irradiates light onto a wafer; a slit unit disposed between the light source unit and the wafer and selectively passing a portion of the light irradiated by the light source unit; and a camera that receives light that is refracted or proceeds as is without being blocked by the wafer among the slit light incident on the wafer through the slit unit, wherein the slit unit comprises a slit formed in a long horizontal shape so that a portion of the light irradiated by the light source unit selectively passes through.

[0014] In addition, the present invention provides a high-precision inspection device for measuring wafer defects, characterized in that the slit is configured to allow light parallel to the optical axis of the light irradiated by the light source to pass through.

[0015] In addition, the present invention provides a high-precision inspection device for measuring wafer defects, characterized in that the slit is formed such that the horizontal width parallel to the edge of the wafer is longer than the vertical width perpendicular to the edge of the wafer.

[0016] In addition, the present invention provides a high-precision inspection device for measuring wafer defects, characterized in that the slit portion comprises a transparent plate in the shape of a rectangular parallelepiped, a metal barrier film deposited on one surface of the transparent plate, and the slit patterned in a long shape along the longitudinal direction on the barrier film to allow light to pass through.

[0017] In addition, a high-precision inspection device for measuring wafer defects is provided, characterized by further including an alignment lens disposed between the slit portion and the wafer, which aligns the slit light passing through the slit portion into parallel light.

[0018] In addition, the present invention provides a high-precision inspection device for measuring wafer defects, characterized in that the alignment lens aligns the single-wavelength or multi-wavelength slit light passing through the slit portion in parallel so that they have the same focus.

[0019] In addition, the present invention provides a high-precision inspection device for measuring wafer defects, characterized in that the alignment lens is configured such that an aspherical lens that corrects spherical aberration or a bonded lens that reduces chromatic aberration is combined with a spherical lens.

[0020] In addition, the present invention provides a high-precision inspection device for measuring wafer defects, characterized by further including a correction lens disposed between the wafer and the camera, which collects parallel light parallel to the wafer among the light not blocked by the wafer into the camera.

[0021] In addition, the present invention provides a high-precision inspection device for measuring wafer defects, characterized in that the correction lens includes a telecentric lens that guides parallel light parallel to the wafer to be transmitted to the camera. Effects of the invention

[0023] The present invention utilizes a slit to block light at unwanted angles and is formed to allow only light parallel to the optical axis to pass through, so that light rays incident from the light source through the slit are aligned uniformly and consistently, thereby enabling the camera to provide a wafer image with high resolution.

[0024] In addition, since the vertical width of the slit is formed narrowly, the parallelism of light is improved, resulting in increased measurement precision. Furthermore, since the horizontal width of the slit is formed wide, a large amount of light can be secured, resulting in a stronger measurement signal.

[0025] In addition, by using patterning technology to form a fine structure on the barrier, it is possible to precisely form the vertical width of the slit to a small size.

[0026] In addition, parallel light aligned in the alignment lens is transmitted to the wafer while forming the same focal point, and since it is refracted at a specific angle within the wafer, it is possible to analyze only the desired light path, thereby enabling precise optical measurement.

[0027] In addition, the correction lens placed between the wafer and the camera is configured to exclude light generated from the upper and lower parts of the light being bent in the wafer and to selectively focus only parallel light parallel to the wafer onto the camera, thereby minimizing distortion of the wafer image captured by the camera and enabling the acquisition of a more precise image. Brief explanation of the drawing

[0029] Figure 1 is a drawing illustrating a conventional wafer thickness measuring device. FIG. 2 is a diagram illustrating the state of measuring the thickness of a wafer using a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention. FIG. 3(a) is a schematic diagram showing a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention in a vertical direction. FIG. 3(b) is a schematic diagram showing a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention in a horizontal direction. FIG. 4(a) is a plan view illustrating a slit portion according to a preferred embodiment of the present invention, FIG. 4(b) is a perspective view illustrating a slit portion according to a preferred embodiment of the present invention, and FIG. 4(c) is a vertical cross-sectional view illustrating a slit portion according to a preferred embodiment of the present invention. FIG. 5(a) is a diagram showing a light path with the slit portion omitted, and FIG. 5(b) is a diagram showing a light path with the slit portion provided according to a preferred embodiment of the present invention. Figure 6 (a) is a diagram showing the light path transmitted to the camera through a standard lens, and Figure 6 (b) is a diagram showing an image of a wafer captured through a standard lens. FIG. 7(a) is a diagram illustrating an optical path transmitted to a camera through a correction lens according to a preferred embodiment of the present invention, and FIG. 7(b) is a diagram illustrating an image of a wafer captured through a correction lens according to a preferred embodiment of the present invention. FIG. 8(a) is a drawing showing an image of a sample taken through a general lens, and FIG. 8(b) is a drawing showing an image of a sample taken through a correction lens according to a preferred embodiment of the present invention. FIG. 9 is a configuration diagram illustrating the operation of a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention. FIG. 10 (a) is a schematic diagram showing an image of a single wafer captured by a camera according to a preferred embodiment of the present invention, and FIG. 10 (b) is a schematic diagram showing an image of multiple wafers captured by a camera according to a preferred embodiment of the present invention. Specific details for implementing the invention

[0030] Hereinafter, a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention will be described in more detail with reference to the attached drawings.

[0032] FIG. 2 is a diagram illustrating the state of measuring the thickness of a wafer using a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention, FIG. 3 (a) is a schematic diagram illustrating the high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention in a vertical direction, and FIG. 3 (b) is a schematic diagram illustrating the high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention in a horizontal direction.

[0033] Referring to FIGS. 2 and 3, a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention includes a light source unit (100), a slit unit (200), a camera (300), an alignment lens (400), and a correction lens (410).

[0034] The light source irradiates light onto the wafer (W) and may include, for example, a light-emitting diode (LED), a lamp, a laser, etc. Such a light source may include both a single-band light source and a broadband light source, so that it can be designed to enable wafer (W) inspection using various wavelength ranges.

[0035] The slit section (200) is positioned between the light source section (100) and the wafer (W) and is configured to selectively allow a portion of the light irradiated from the light source section (100) along the X-axis to pass through. The slit section (200) is configured to form a thin slit (230) through it, and the light irradiated from the light source is guided to pass through the slit (230). At this time, the slit (230) is designed to have a very narrow width in the vertical direction (Z-axis), i.e., the meridional plane, and a relatively wide width in the horizontal direction (Y-axis), i.e., the slit plane, so that the light passing through the slit (230) forms parallel slit light over a wide area.

[0036] Then, the slit light formed while passing through the slit (230) passes the side surface of the wafer (W), that is, the edge of the wafer (W), and reaches the camera (300) to form an image. At this time, the slit (230) is formed thinly so that light parallel to the optical axis of the light irradiated by the light source unit (100) passes through. Here, the optical axis refers to the path of the central ray among the light irradiated by the light source unit (100).

[0037] As such, the present invention is configured to block light with unwanted angles using a slit (230) and allow only light nearly parallel to the optical axis to pass through, so that light rays incident from the light source (100) through the slit (200) to the wafer (W) are aligned consistently and uniformly. As a result, the camera (300) has the effect of providing an edge image of the wafer (W) with high resolution.

[0038] If light irradiated from the light source (100) spreads in multiple directions without the slit section (200), it is difficult to precisely measure the thickness of the wafer (W). On the other hand, the present invention can clearly distinguish between the area covered by the wafer (W) and the area not covered by using the slit light formed through the slit section (200). The part blocked by the wafer (W) appears dark, and only the part through which the slit light passes is detected. Through this, the exact thickness of the wafer (W) can be clearly identified, and based on this, the thickness of the wafer (W) can be precisely measured.

[0039] The alignment lens (400) is positioned between the slit section (200) and the wafer (W) to align the slit light passing through the slit section (200) into parallel light. In this way, the alignment lens (400) serves to align light that has spread in multiple directions into one direction, thereby reducing light diffusion and maintaining directionality. That is, the alignment lens (400) aligns multiple slit lights of a single wavelength or multiple wavelengths passing through the slit section (200) so that they become parallel light with the same focus. This alignment lens (400) generally uses an aspherical lens or a spherical lens to correct spherical aberration, thereby minimizing light distortion. Additionally, the alignment lens (400) may further combine a bonding lens that reduces chromatic aberration with the aspherical lens or spherical lens, and the combined bonding lens corrects chromatic aberration so that light of various wavelengths is gathered at the same focus. In this way, the alignment lens (400) controls chromatic aberration and spherical aberration for the wavelength passing through the slit portion (200), thereby having the effect of maintaining the parallelism of the light.

[0040] The correction lens (410) is positioned between the wafer (W) and the camera (300) and collects parallel light that is parallel to the wafer (W) among the light that is not blocked by the wafer (W) to the camera (300). The correction lens (410) adjusts the angle of incidence when light is refracted on the surface of the wafer (W) and guides it in an optimal direction so that it is accurately transmitted to the camera (300). This increases the accuracy of the light collected by the camera (300) and optimizes the path of the light to prevent unnecessary distortion, such as focus flow or chromatic aberration.

[0041] These corrective lenses (410) may include a telecentric lens that guides parallel light to be transmitted to the camera (300). The telecentric lens can prevent distortions such as focus flow and chromatic aberration by optimizing the angle of the incident light and optimizing the light path. That is, it guides the refracted light generated from the surface of the wafer (W) in an optimal direction to ensure accurate light collection by the camera (300).

[0042] The camera (300) receives light that is refracted or continues as is without being blocked by the wafer (W) among the parallel light incident on the wafer (W) after passing through the slit section (200) and the alignment lens (400). At this time, the parallel light is corrected by the correction lens (410) and then guided to the camera (300). The camera (300) may use an image sensor such as a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, and may select a monochrome or color sensor as needed to analyze the characteristic response of a specific light source. The light signal collected by the camera (300) is converted into a digital image in a separate signal processing unit (not shown), and then the pattern is analyzed to calculate the thickness, refractive index, surface shape, etc. of the wafer (W), and may also perform automatic defect detection and data analysis by applying algorithms such as machine learning.

[0044] FIG. 4(a) is a plan view illustrating a slit portion according to a preferred embodiment of the present invention, FIG. 4(b) is a perspective view illustrating a slit portion according to a preferred embodiment of the present invention, and FIG. 4(c) is a vertical cross-sectional view illustrating a slit portion according to a preferred embodiment of the present invention.

[0045] Referring to FIGS. 3 and 4, the slit portion (200) includes a transparent plate (210), a blocking film (220), and a slit (230). The transparent plate (210) is formed, for example, as a rectangular prism, a polyhedron, a circle, a column, etc., and is formed of a transparent material that transmits light well, such as quartz or optical glass. The size of the transparent plate (210) may be, for example, 40 mm in width, 10 mm in length, and 1 mm in height, and it is obvious that the present invention is not limited thereto. The blocking film (220) is deposited on one surface of the transparent plate (210) and is deposited in the form of a thin film capable of blocking light. This blocking film (220) may be formed of a metal film such as chrome or a material other than metal.

[0046] A slit (230) is patterned in a long shape along the longitudinal direction on a blocking film (220) to allow light to pass through. The slit (230) is formed such that the horizontal width parallel to the edge of the wafer (W) is longer than the vertical width perpendicular to the edge of the wafer (W). The horizontal width of the slit (230) is formed long enough to correspond to the horizontal length of the transparent plate (210), and the vertical width of the slit (230) can be formed short, approximately 10 μm. Representative patterning methods that can form a precise slit (230) pattern on the blocking film (220) include lithography and electron beam lithography. As such, the present invention can form a fine structure on the blocking film (220) using patterning technology, thereby having the effect of precisely forming the vertical width of the slit (230) to a small size.

[0047] Meanwhile, if the vertical width of the slit (230) is made very narrow and the horizontal width is made wide, a large amount of light can enter while maintaining a constant directionality, thereby obtaining a selective light filtering effect. That is, since the vertical width of the slit (230) is formed narrowly in the present invention, the parallelism of light is improved, and the measurement precision is increased. In addition, since the horizontal width of the slit (230) is formed wide, a large amount of light can be secured, and the measurement signal becomes stronger.

[0049] FIG. 5(a) is a diagram showing a light path with the slit portion omitted, and FIG. 5(b) is a diagram showing a light path with the slit portion provided according to a preferred embodiment of the present invention.

[0050] Referring to FIG. 5(a), when the slit portion (200) is omitted while the light source portion (100) is designed to be large, the light irradiated from the light source portion (100) spreads widely, reducing the resolution, and unnecessary light is mixed in, increasing the noise of the signal. Consequently, it becomes difficult to selectively measure only the light at a specific angle, and there is a problem in that the analysis accuracy is lowered as light reflected and scattered from the wafer (W) is mixed.

[0051] Referring to FIG. 5(b), the present invention is provided with a slit portion (200), so that even if the size of the light source portion (100) is large, only light in a specific area, that is, light parallel to the optical axis, can be selectively passed through. The alignment lens (400) aligns the slit light that has passed through the slit portion (200) into parallel light so that it is uniformly incident on the wafer (W). This reduces unnecessary scattered light and increases resolution. In addition, the parallel light aligned by the alignment lens (400) is transmitted to the wafer (W) while forming the same focal point, and since it is refracted at a specific angle on the wafer (W), only the desired light path can be analyzed, thereby enabling precise optical measurement.

[0053] Figure 6 (a) is a diagram showing the light path transmitted to the camera through a standard lens, and Figure 6 (b) is a diagram showing an image of a wafer captured through a standard lens.

[0054] Referring to FIG. 6(a) and FIG. 6(b), when a standard lens (N) is placed between the wafer (W) and the camera (300), the light bent from the wafer (W) is transmitted directly to the camera (300), increasing unnecessary noise and reducing the accuracy of the measurement signal. That is, light at other angles (L2, L3) other than the parallel light (L1) is also received by the camera (300), which can cause distortion. As a result, there is a problem in that the accuracy of the wafer (W) image captured by the camera (300) is reduced and the resolution is decreased.

[0056] FIG. 7(a) is a diagram illustrating an optical path transmitted to a camera through a correction lens according to a preferred embodiment of the present invention, and FIG. 7(b) is a diagram illustrating an image of a wafer captured through a correction lens according to a preferred embodiment of the present invention.

[0057] Referring to FIG. 7(a) and FIG. 7(b), when a correction lens (410) is placed between the wafer (W) and the camera (300), light generated from the upper and lower parts of the light being bent in the wafer (W) is excluded, and only parallel light (L1) parallel to the wafer (W) is selectively focused to the camera (300). Through this, an accurate light path is secured, and distortion of the wafer (W) image captured by the camera (300) is minimized, thereby allowing for the acquisition of a more precise image and an effect of improved resolution.

[0059] FIG. 8(a) is a drawing showing an image of a sample taken through a general lens, and FIG. 8(b) is a drawing showing an image of a sample taken through a correction lens according to a preferred embodiment of the present invention.

[0060] Referring to Fig. 8 (a), the sample (S) captured through a standard lens has its image distorted in three dimensions due to light transmitted from various angles.

[0061] On the other hand, referring to Fig. 8(b), the correction lens (410) selectively focuses only parallel light to the camera (300), so the sample (S) captured through the correction lens (410) appears clear and distinct in a flat plane.

[0063] Hereinafter, the operation of a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention will be described.

[0065] FIG. 9 is a configuration diagram illustrating the operation of a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention.

[0066] Referring to the drawings, a high-precision inspection device for measuring wafer defects according to a preferred embodiment of the present invention comprises a light source unit (100), a slit unit (200), and an alignment lens (400) formed as one module, and a correction lens (410) and a camera (300) formed as another module. A measurement target, i.e., a wafer (W), is placed between these modules.

[0067] The light source unit (100) irradiates light onto the slit unit (200), and the slit unit (200) forms slit light by allowing a portion of the light irradiated from the light source unit (100) to pass through. The slit light is aligned to become parallel light as it passes through the alignment lens (400). The parallel light aligned in this way is irradiated onto the wafer (W). Afterward, the path of the refracted light that is refracted by the wafer (W) or the parallel light that passes through the wafer (W) without being refracted is optimized as it passes through the correction lens (410). That is, the correction lens (410) guides the refracted light generated from the surface of the wafer (W) to the optimal direction desired by the camera (300). Then, the refracted light or the parallel light that passes through the camera (300) is converted into a digital image by a separate signal processing unit (not shown), and the pattern is analyzed to calculate the thickness, refractive index, surface shape, etc. of the wafer (W).

[0069] FIG. 10 (a) is a schematic diagram showing an image of a single wafer captured by a camera according to a preferred embodiment of the present invention, and FIG. 10 (b) is a schematic diagram showing an image of multiple wafers captured by a camera according to a preferred embodiment of the present invention.

[0070] Referring to FIG. 10 (a), the side image of a single wafer (W) captured by the camera (300) shows a high contrast and a clear boundary formed between the wafer (W) and the background, as the error caused by unnecessary light refraction is reduced. In addition, the outline of the wafer (W) is accurately represented, and the illumination is uniform so that no specific area is excessively bright or dark, and the shape is not distorted. Furthermore, unnecessary reflections and optical noise are reduced, resulting in a cleaner image. Due to these characteristics, the thickness of the wafer (W) can be measured more accurately, and reliable analysis becomes possible.

[0071] Referring to FIG. 10(b), even when multiple wafers (W) are stacked and bonded, the boundary between the wafer (W) and the background is clearly formed, just like with a single wafer (W), and the border contour is accurately expressed. In addition, optical noise is reduced so that a clean image is obtained, allowing for precise measurement of the shape and thickness of the stacked wafers (W). This enables reliable analysis. Furthermore, the size of the gap between two wafers (W) stacked together can also be measured.

[0073] Although the present invention has been described in detail in the above embodiments, it is obvious that the present invention is not limited thereto, and it is obvious to those skilled in the art that various modifications and variations are possible within the scope of the technical spirit of the present invention, and if such modifications and variations fall within the scope of the appended claims, the technical spirit thereof should also be considered to be within the scope of the present invention. Explanation of the symbols

[0075] 100: Light source 200: Slit section 210: Transparent plate 220: Barrier 230: Slit 300: Camera 400: Alignment lens 410: Correction lens

Claims

Claim 1 A high-precision inspection device for measuring wafer defects, comprising: a light source unit that irradiates light onto a wafer; a slit unit disposed between the light source unit and the wafer and selectively passing a portion of the light irradiated by the light source unit; and a camera that receives light that is refracted or proceeds as is without being blocked by the wafer among the slit light incident on the wafer through the slit unit, wherein the slit unit includes a slit formed in a long horizontal shape so that a portion of the light irradiated by the light source unit selectively passes through. Claim 2 A high-precision inspection device for measuring wafer defects according to claim 1, wherein the slit is configured to allow light parallel to the optical axis of the light irradiated by the light source to pass through. Claim 3 A high-precision inspection device for measuring wafer defects according to claim 1, wherein the slit is formed such that the width in the horizontal direction parallel to the edge of the wafer is longer than the width in the vertical direction perpendicular to the edge of the wafer. Claim 4 A high-precision inspection device for measuring wafer defects according to claim 1, wherein the slit portion comprises a transparent plate made of a transparent material, a blocking film deposited on one surface of the transparent plate, and the slit patterned in a long shape along the longitudinal direction on the blocking film to allow light to pass through. Claim 5 A high-precision inspection device for measuring wafer defects according to claim 1, further comprising an alignment lens disposed between the slit portion and the wafer and aligning the slit light passing through the slit portion in parallel with the parallel light. Claim 6 A high-precision inspection device for measuring wafer defects according to claim 5, wherein the alignment lens is characterized by aligning the single-wavelength or multi-wavelength slit light passing through the slit portion in parallel so that it has the same focus. Claim 7 A high-precision inspection device for measuring wafer defects according to claim 5, wherein the alignment lens is configured such that an aspherical lens that corrects spherical aberration or a bonded lens that reduces chromatic aberration is combined with a spherical lens. Claim 8 A high-precision inspection device for measuring wafer defects according to claim 1, further comprising a correction lens disposed between the wafer and the camera and focusing parallel light parallel to the wafer among the light not blocked by the wafer to the camera. Claim 9 A high-precision inspection device for measuring wafer defects according to claim 8, characterized in that the correction lens includes a telecentric lens that guides parallel light parallel to the wafer to be transmitted to the camera.

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