Optical inspection apparatus and its operating method

Abstract

This invention provides an optical inspection apparatus and a method for operating it. [Solution] An optical inspection apparatus comprising: a projection optical system arranged to acquire inclined projection images of multiple through-hole structures on a substrate; a digital microscope system arranged to acquire 2D interference images; and a computing unit arranged to analyze the 2D interference images to acquire stereoscope image data and to analyze the inclined projection images to acquire multiple parameters of the through-hole structures, and electrically connected to the projection optical system and the digital microscope system. The optical inspection apparatus can be used to acquire feedback in real time. Since multiple through-hole structures can be inspected simultaneously, the time required to scan the substrate is reduced.

Description

Technical Field

[0001] The present invention relates to an optical inspection apparatus. More specifically, the present invention relates to a non-contact and non-destructive inspection apparatus.

Background Art

[0002] In the field of semiconductor inspection, common inspection methods include, for example, laser confocal microscopy, color confocal microscopy, or white light scanning technology. However, with such methods, it is not possible to simultaneously inspect a plurality of through-holes. Also, these methods are time-consuming. For example, the conventional SEM scanning method requires about 30 minutes for the pretreatment process. Furthermore, with the current inspection methods, it is not possible to analyze the taper angle of the corners of the through-holes. However, with the miniaturization of the critical dimensions today, the taper angle of the corners of the through-holes has become extremely important for the metal plating process.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, shortening the processing time (for example, reducing it to about several seconds) and providing an optical inspection apparatus and an operation method for through-holes are still one of the urgently required development goals.

Means for Solving the Problems

[0004] One aspect of the present disclosure is an optical inspection apparatus.

[0005] In one embodiment, the optical inspection apparatus includes a projection optical system arranged to acquire an inclined projection image of a plurality of through-hole structures on a substrate, a digital microscope system arranged to acquire a 2D interference image, and a calculation unit arranged to analyze the 2D interference image to acquire stereoscopic image data and analyze the inclined projection image to acquire a plurality of parameters of the through-hole structure, and being electrically connected to the projection optical system and the digital microscope system.

[0006] In one embodiment, the projection optical system further includes a light source positioned to illuminate the back side of the substrate, a projection lens positioned on the front side of the substrate and positioned to acquire an inclined projection image of the through-hole structure, and an image sensor positioned to record the image formed from the projection lens.

[0007] In one embodiment, the projection lens of the projection optical system is a telecentric lens.

[0008] In one embodiment, the computing unit is configured to execute an extended depth of focus algorithm or an all-in-focus algorithm to obtain parameters of the through-hole structure.

[0009] In one embodiment, the through-hole structure is an etched through-hole, and the parameters include upper critical dimension, middle critical dimension, lower critical dimension, taper angle, pitch, diameter, roughness, height, and centerline.

[0010] In one embodiment, the through-hole structure is a laser-modified region, and the parameters include depth, angle, pitch, density, line width, and internal cracks.

[0011] In one embodiment, the digital microscope system further includes a laser light source arranged to emit incident light, and an image sensor arranged to record a 2D interference image formed from the incident light that has passed through a through-hole structure.

[0012] In one embodiment, the optical inspection apparatus further comprises a carrier on which a substrate is mounted and whose distance from the image sensor is adjustable.

[0013] In one embodiment, the computing unit is configured to perform a backpropagation reconstruction algorithm on a 2D interferometric image to obtain a 3D image stack of the through-hole structure.

[0014] In one embodiment, the computing unit is configured to execute a biimage removal algorithm on a 3D image stack.

[0015] In one embodiment, the computing unit is configured to execute a super-resolution algorithm on a 3D image stack.

[0016] In one embodiment, the through-hole structure is an etched through-hole, and the stereoscope image data includes upper critical dimension, middle critical dimension, lower critical dimension, taper angle, upper roundness, lower roundness, pitch, diameter, height, axis, surface roughness, cross-sectional view, and map scan.

[0017] In one embodiment, the through-hole structure is a laser-modified region, and the stereoscope image data includes laser modification accuracy and map scan.

[0018] Another aspect of this disclosure is a method for operating an optical inspection apparatus.

[0019] In one embodiment, the operation method of the optical inspection apparatus includes the steps of forming a plurality of etched through-holes in a substrate, acquiring a first inclined projection image of the etched through-holes from a projection optical system, acquiring a first 2D interference image of the etched through-holes using a digital microscope system, and analyzing the first inclined projection image with a computing unit to acquire a plurality of parameters, and analyzing the first 2D interference image to acquire stereoscope image data.

[0020] In one embodiment, the method of operating the optical inspection apparatus further comprises calculating the minimum pitch based on a predetermined diameter of the etching through-hole and the thickness of the substrate using a calculation unit before forming the etching through-hole in the substrate.

[0021] In one embodiment, the step of acquiring a first inclined projection image of an etched through-hole from a projection optical system further includes irradiating the back side of the substrate with a light source, acquiring a first inclined projection image of the etched through-hole with a projection lens, and recording the image formed by the projection lens with an image sensor.

[0022] In one embodiment, the step of obtaining a first 2D interference image of an etched through-hole by a digital microscope system further includes emitting incident light toward a substrate by a laser light source and recording an image formed from the incident light transmitted through the etched through-hole by an image sensor.

[0023] In one embodiment, the method of operating an optical inspection apparatus further includes a step of performing laser modification on a substrate to form a plurality of laser modification regions before forming etched through-holes in the substrate.

[0024] In one embodiment, the method of operating an optical inspection apparatus further includes calculating a minimum pitch by a calculation unit based on a predetermined line width of a laser modification region and the thickness of a substrate before performing laser modification on the substrate to form a laser modification region.

[0025] In one embodiment, the method of operating an optical inspection apparatus further includes a step of obtaining a second oblique projection image of a laser modification region by a projection optical system and a step of obtaining a second 2D interference image of the laser modification region by a digital microscope system.

Advantages of the Invention

[0026] In the above-described embodiment, since the optical inspection apparatus is a non-contact and non-destructive inspection method, feedback can be provided in real time. The shape and profile of the through-hole structure can be obtained from the oblique projection image from the projection optical system and the 2D interference image from the digital microscope system. Also, since a plurality of through-hole structures can be inspected simultaneously, the time required for scanning the substrate is shortened. The taper angles of the four corners of the through-hole structure can be inspected, so that a through-hole via (i.e., a metal conductor) having a much smaller critical dimension can be formed by applying a metal plating process.

Brief Description of the Drawings

[0027] The present invention can be more fully understood by referring to the accompanying drawings while reading the following detailed description of the embodiments. [Figure 1A] It is a schematic diagram of an optical inspection device according to an embodiment of the present disclosure. [Figure 1B] It is a projection optical system according to an embodiment of the present disclosure. [Figure 1C] It is a digital microscope system according to an embodiment of the present disclosure. [Figure 2] It is a schematic diagram of an image acquired by a projection optical system. [Figure 3A] It is an image of a laser-modified substrate acquired by a projection optical system. [Figure 3B] It is an image of a laser-modified substrate acquired by a projection optical system. [Figure 3C] It is an image of a laser-modified substrate acquired by a projection optical system. [Figure 3D] It is an image of a laser-modified substrate acquired by a projection optical system. [Figure 4] It is an image of an etched through-hole acquired by a projection optical system. [Figure 5] It is an image of an etched through-hole acquired by a projection optical system. [Figure 6] It is a 2D profile analyzed from an image acquired by a projection optical system. [Figure 7] It is a schematic diagram of parameters analyzed from an image acquired by a projection optical system. [Figure 8] It is a roughness profile analyzed from an image acquired by a projection optical system. [Figure 9] It is a schematic diagram of the generation of a 2D interference image according to an embodiment of the present disclosure. [Figure 10] It is a 2D interference image acquired by the digital microscope system of FIG. 9. [Figure 11] It is a 3D image stack acquired by the digital microscope system of FIG. 9. [Figure 12] It is a stereoscopic image reconstructed from the 3D image stack of FIG. 11. [Figure 13] This is an image of a laser-modified substrate acquired by a digital microscope system according to one embodiment of the present disclosure. [Figure 14A] This is an image of an etched through-hole acquired by a digital microscope system according to one embodiment of the present disclosure. [Figure 14B] This is an image of an etched through-hole acquired by a digital microscope system according to one embodiment of the present disclosure. [Figure 14C] This is an image of an etched through-hole acquired by a digital microscope system according to one embodiment of the present disclosure. [Figure 14D] This is an image of an etched through-hole acquired by a digital microscope system according to one embodiment of the present disclosure. [Figure 14E] This is an image of an etched through-hole acquired by a digital microscope system according to one embodiment of the present disclosure. [Figure 15] This is a schematic diagram illustrating the reconstruction of 3D point cloud data of a through-hole structure. [Figure 16A] This is a schematic diagram of the inspection angle according to one embodiment of the present disclosure. [Figure 16B] Figure 16A is a schematic diagram of the inspection image obtained at the inspection angle shown. [Figure 17A] This is a schematic diagram of an inspection image showing an overlapping through-hole structure. [Figure 17B] This is a schematic diagram of an inspection image showing an overlapping through-hole structure. [Figure 18] This is a schematic diagram of the rotation angle according to one embodiment of the present disclosure. [Figure 19] This is a diagram of the minimum pitch based on the minimum pitch equation. [Figure 20] This is a schematic diagram of an inspection image of a laser-modified substrate according to one embodiment of the present disclosure. [Figure 21] This is a flowchart showing how to operate an optical inspection device. [Modes for carrying out the invention]

[0028] The present invention is now described in detail with reference to embodiments, and examples of these embodiments are shown in the accompanying drawings. Wherever possible, identical or corresponding parts in the accompanying drawings and description are given the same reference numerals.

[0029] Figure 1A is a schematic diagram of an optical inspection apparatus 10 according to one embodiment of the present disclosure. The optical inspection apparatus 10 comprises a projection optical system 100, a digital microscope system 200, a computing unit 300, and a carrier 400. The substrate 500 to be inspected is mounted on the carrier 400. The substrate 500 is transparent or translucent, and is, for example, a glass substrate, an acrylic substrate, or a silicon substrate. In this embodiment, the projection optical system 100 is a non-orthogonal projection optical system, but the present disclosure is not limited thereto.

[0030] The projection optical system 100 and the digital microscope system 200 are positioned to inspect multiple through-hole structures 510 within the substrate 500. Before the etching process and after the laser modification process, the through-hole structures 510 represent laser-modified regions. After the etching process, the through-hole structures 510 represent etched through-holes formed at the locations of the laser-modified regions. The etched through-holes are then filled with metal in a metal plating process to form through-hole vias (i.e., metal conductors).

[0031] The projection optical system 100 is configured to acquire an inclined projection image of the through-hole structure 510 of the substrate 500. The digital microscope system 200 is configured to acquire a 2D interference image of the through-hole structure 510 of the substrate 500. The computing unit 300 is electrically connected to the projection optical system 100 and the digital microscope system 200. The computing unit 300 is configured to analyze the inclined projection image from the projection optical system 100 to acquire several parameters of the substrate 500, and to analyze the 2D interference image from the digital microscope system 200 to acquire stereoscope image data of the substrate 500.

[0032] Figure 1B is a schematic diagram of a projection optical system 100 according to one embodiment of the present disclosure. The projection optical system 100 includes a light source 110, a projection lens 120, and an image sensor 130. The light source 110 is positioned to illuminate the back side 502 of the substrate 500. The projection lens 120 is positioned on the front side 504 of the substrate 500. The projection lens 120 is positioned to acquire an inclined projection image of the through-hole structure 510. The image sensor 130 is positioned to record the image formed by the projection lens 120.

[0033] The projection lens 120 of the projection optical system 100 is a telecentric lens. In this embodiment, there is an angle between the first optical axis AX1 of the projection lens 120 and the second optical axis AX2 of the planar diffuse light emitted from the light source 110. For example, this angle is 40 to 50 degrees. In this embodiment, the angle is 45 degrees. In some other embodiments, the optical axis of the projection lens 120 and the optical axis of the planar diffuse light emitted from the light source 110 are parallel to each other (for example, the embodiment in Figure 1A). In other words, the irradiation method may be dark-field irradiation or field irradiation. Also, the shape of the light beam emitted from the laser light source 210 is not limited.

[0034] Figure 1C is a schematic diagram of a digital microscope system 200 according to one embodiment of the present disclosure. The digital microscope system 200 includes a laser light source 210 and an image sensor 230. The laser light source 210 is a point light source and is arranged to emit incident light 212. The image sensor 230 is arranged to record a 2D interference image formed from the incident light 212 transmitted through a through-hole structure 510 of a substrate 500. In some embodiments, the distance between the carrier 400 and the image sensor 230 is adjustable to improve resolution. The digital microscope system 200 is a lensless system, such as a digital lensless holographic microscope or a digital axial holographic microscope, but is not limited thereto.

[0035] In some embodiments, the projection optical system 100 and the digital microscope system are available separately. Since the optical inspection device 10 is a non-contact and non-destructive inspection method, it can provide feedback in real time.

[0036] Figure 2 is a schematic diagram of an image acquired by the projection optical system 100. Please refer to Figures 1B and 2 now. The projection optical system 100 scans the substrate 500 to acquire multiple tilt projection images IM1, IM2, and IM3. In this disclosure, the computing unit 300 is configured to execute an extended depth of field algorithm to acquire a processed image IM4. Extended depth of field is used to enhance the depth of field of the tilt projection image. Therefore, the profile of the through-hole structure 510 in the processed image IM4 is more accurate than the profile of the through-hole structure 510 in the tilt projection images IM1, IM2, and IM3.

[0037] Figures 3A to 3D are images of the laser-modified substrate acquired by the projection optical system 100. Please refer to Figures 1B and 3A to 3D now. These images of the laser-modified region 510 are processed, for example, by an extended depth of field algorithm to increase resolution. Subsequently, these images are analyzed by the computing unit 300 to obtain several parameters of the laser-modified region 510.

[0038] For example, the parameters of the laser-modified region 510 include, but are not limited to, depth, angle, pitch, density, line width, and internal cracks. These parameters are described in detail in Figures 3A to 3D.

[0039] Figure 3A is an image showing the coordinates of the laser-modified regions 510. Therefore, the pitch between the laser-modified regions 510 can be calculated. Figure 3B is an image showing internal cracks IC that have occurred around the laser-modified regions 510. Figure 3C is an image showing the dense P1 and dilute P2 areas of the laser-modified regions 510. Figure 3D is an image showing the depth DP, line width LW, and angle AN of the laser-modified regions 510. Angle AN is the angle between the vertical direction of the laser-modified regions 510 and the horizontal direction of the laser-modified substrate 500.

[0040] Based on the parameters inspected by the projection optical system 100, the quality of the laser modification can be determined and reported, and the laser modification process can be improved.

[0041] Figure 4 is an image of an etched through-hole acquired by the projection optical system 100. Please refer to Figures 1B and 4 now. In this embodiment, the image is an oblique projection image processed by an all-in-focus algorithm. In some other embodiments, the projection optical system 100 may be used in combination with other algorithms that can improve or extend the depth of field of the telecentric lens.

[0042] Figure 5 is an image of the etched through-hole acquired by the projection optical system 100. Please refer to Figures 1B and 5. The image of the etched through-hole 510 is processed and analyzed by the calculation unit 300 to obtain several parameters of the etched through-hole 510. The parameters analyzed from the inclined projection image are calibrated to obtain parameters corresponding to the orthogonal image of the etched through-hole 510. Thus, information on the left and right walls of the etched through-hole can be analyzed.

[0043] For example, the parameters of the etched through-hole 510 include, but are not limited to, the upper critical dimension, middle critical dimension, lower critical dimension, pitch, diameter, shape, roughness, height, and centerline. These parameters are described in detail in Figures 6 to 8.

[0044] Figure 6 shows the 2D profile analyzed from the image acquired by the projection optical system 100. Please refer to Figures 1B and 6 now. The 2D profile of the etched through-hole 510 shown in Figure 6 shows the left profile LP, the right profile RP, the left waveform intensity LW, the right waveform intensity RW, and the center line CL.

[0045] Figure 7 is a schematic diagram of parameters analyzed from images acquired by the projection optical system 100. Please refer to Figures 1B and 7 now. The schematic diagram of the etched through-hole has an hourglass shape in the cross-sectional view. The schematic diagram of the etched through-hole 510 shows the upper critical dimension TCD, the middle critical dimension MCD, the lower critical dimension BCD, the shape, the heights H1 and H2, and the central inclination angle CTA. The middle critical dimension MCD is half the height dimension. The narrowest critical dimension (NCD) is the dimension measured in the narrowest region of the etched through-hole. In this embodiment, the narrowest critical dimension NCD and the middle critical dimension MCD are in the same position. In an alternative embodiment, the position of the narrowest critical dimension NCD may be higher or lower than the position of the middle critical dimension MCD. The diameter of the etched through-hole 510 is substantially equal to the upper critical dimension TCD, or equal to the average of the upper critical dimension TCD, the middle critical dimension MCD, and the lower critical dimension BCD, but is not limited to these.

[0046] The shape parameters include, for example, the taper angles of the four corners: upper left taper angle LTA, upper right taper angle RTA, lower left taper angle LBA, and lower right taper angle RBA. The height includes a first height H1 and a second height H2. The first height H1 represents the distance from the top of the etched through-hole to the narrowest region. The second height H2 represents the distance from the narrowest region to the bottom of the etched through-hole. The height ratio between the first height H1 and the second height H2 can be determined. The thickness of the substrate 500 is substantially the sum of the first height H1 and the second height H2.

[0047] Figure 8 shows the roughness profile analyzed from the image acquired by the projection optical system 100. Please refer to Figures 1B and 8 now. The roughness profile shows the left-side roughness LR and right-side roughness RR of the etched through-hole 510.

[0048] By scanning the substrate 500 with the projection optical system 100 and processing and analyzing the tilted projection image, the profile of the etched through-hole 510 from top to bottom can be inspected. Specifically, with conventional methods, only the upper or lower portion of the etched through-hole can be clearly inspected in the orthogonal image. Therefore, in the tilted projection image, any damaged or blocked portions of the through-hole structure 510 that cannot be seen in the orthogonal image can be clearly seen. In addition, since multiple through-hole structures can be inspected simultaneously, the time required to scan the substrate is reduced. Since the taper angles of the four corners of the through-hole structure can be inspected, a metal plating process can be applied to form through-hole vias (i.e., metal conductors) with much smaller critical dimensions (e.g., critical dimensions of less than 5 μm and taper angles of less than 8 degrees).

[0049] Figure 9 is a schematic diagram of the generation of a 2D interference image according to one embodiment of the present disclosure. Figure 10 is a 2D interference image IM5 acquired by the digital microscope system 200 of Figure 9. Please refer to Figures 1C, 9, and 10 now. The incident light 212 has a plane wave propagating toward the front side 504 of the substrate 500. The portion of the incident light 212 that is not disturbed by the through-hole structure 510 becomes undisturbed light 214. Another portion of the incident light 212 that is disturbed by the through-hole structure 510 becomes disturbed light 216. The undisturbed light 214 and the disturbed light 216 interfere with each other to form a 2D interference image IM5.

[0050] Figure 11 is a 3D image stack IM6 acquired by the digital microscope system 200 of Figure 9. Please refer to Figures 1C, 10, and 11 now. The computing unit 300 is configured to execute a backpropagation reconstruction algorithm on the 2D interferometric image IM5 to acquire the 3D image stack IM6 of the etched through-hole 510. The backpropagation reconstruction algorithm is used to calculate gradient information from the 2D interferometric image IM5 so that the details of the 3D structure can be reconstructed. Figure 12 is a 3D image IM7 reconstructed from the 3D image stack IM6 of Figure 11. In some other embodiments, the above-described extended depth of focus algorithm or other algorithms may be applied to the 2D interferometric image.

[0051] Figure 13 is an image of a laser-modified substrate acquired by a digital microscope system 200 according to one embodiment of the present disclosure. Please refer to Figures 1C and 13 now. The 3D image stack of the laser-modified substrate 500 is processed by a double-image removal algorithm and / or a super-resolution algorithm to increase resolution and is analyzed to acquire stereoscope image data of the laser-modified region 510 within the substrate 500. For example, the stereoscope image data of the laser-modified region 510 includes laser modification accuracy and map scan. As shown in Figure 13, the 3D image can disclose irradiation errors or double-irradiation DS of the laser modification operation. Thus, the laser modification and map scan accuracy can be determined and improved.

[0052] Figures 14A to 14E are images of etched through-holes 510 acquired by a digital microscope system 200 according to one embodiment of the present disclosure. Please refer now to Figures 1C and 14A to 14E. These images of the etched through-holes 510 are processed to increase resolution and analyzed by a computing unit 300 to acquire stereoscope image data of the etched through-holes 510. For example, the stereoscope image data of the etched through-holes 510 includes, but is not limited to, upper critical dimension, middle critical dimension, lower critical dimension, upper roundness, lower roundness, pitch, diameter, height, axis, surface roughness, cross-sectional view, and map scan. Furthermore, since multiple through-hole structures can be inspected simultaneously, the time required to scan the substrate is reduced. Since the taper angles of the four corners of the through-hole structure can be inspected, a metal plating process can be applied to form through-hole vias (i.e., metal conductors) with much smaller critical dimensions.

[0053] Figure 14A is an image of the surface of substrate 500, disclosing the surface roughness of substrate 500 affected during etching. This surface roughness needs to be within an appropriate range so that the subsequent metal plating process can be carried out successfully.

[0054] Figure 14B is a 3D image of the substrate 500. Figure 14C is a cross-sectional view along the axial direction of Figure 14B. Figure 14D is a cross-sectional view along the coronal direction of Figure 14B. Figure 14E is a cross-sectional view along the sagittal direction of Figure 14B.

[0055] Figure 15 is a schematic diagram of the reconstructed 3D point cloud data of the etched through-hole 510. Point cloud data (PCD) can be obtained by processing and analyzing multiple images in a 3D image stack corresponding to different heights of the etched through-hole. Therefore, the point cloud data can be reconstructed to show the 3D profile of the etched through-hole 510.

[0056] By inspecting the substrate 500 with a digital microscope system 200 and processing and analyzing 2D interference images, the 3D profile of the etched through-holes 510 can be determined. In some embodiments, if the through-hole structure 510 has an elliptical shape that is unclear in the inclined projection image, it can be clearly seen in the stereoscopic image data or 3D point cloud data.

[0057] Figure 16A is a schematic diagram of an inspection angle according to one embodiment of the present disclosure. By inspecting the substrate 500a at inspection angle α, the sidewall shape (see Figure 7), diameter (see Figure 7), profile (see Figures 6 and 8), or defects can be inspected. Figure 16B is a schematic diagram of an inspection image obtained at the inspection angle shown in Figure 16A. In this embodiment, the through-hole structures 510a do not overlap each other. In some embodiments, the inspection angle α is between 15 and 65 degrees. In some preferred embodiments, the inspection angle α is between 40 and 45 degrees, but the present disclosure is not limited thereto.

[0058] Figures 17A and 17B are schematic diagrams of inspection images with overlapping through-hole structures. Compared to Figure 16B, the density of through-hole structures 510b in Figure 17A is higher (i.e., the pitch p between through-hole structures 510b is smaller), and the diameter d of through-hole structures 510c in Figure 17B is larger. Consequently, overlap occurs between adjacent through-hole structures 510b and 510c, and it is not possible to completely inspect the through-hole structures.

[0059] Figure 18 is a schematic diagram of the rotation angle according to one embodiment of the present disclosure. By inspecting the substrate 500b in Figure 17A with inspection angle α and rotation angle ψ, the problems in Figures 17A and 17B can be solved. In some embodiments, the rotation angle ψ is between 0 and 50 degrees. In some preferred embodiments, the rotation angle ψ is between 15 and 45 degrees, but the present disclosure is not limited thereto.

[0060] For example, if the inspection angle α is 45 degrees and the rotation angle ψ is 15 degrees, the relationship between the minimum pitch p, the substrate thickness t, and the diameter d is as follows: This is explained by the minimum pitch equation JPEG2026047207000002.jpg14151. Figure 19 is a diagram of the minimum pitch based on the minimum pitch equation.

[0061] For example, coefficient A is in the range of -0.000415484 to -0.000375915, coefficient B is in the range of 0.00224595 to 0.00203205, coefficient C is in the range of -0.00077763 to -0.00070357, coefficient D is in the range of 0.526785 to 0.476615, coefficient E is in the range of 1.677795 to 1.518005, and coefficient F is in the range of -15.46797 to -13.99483. Coefficients A to F are not limited to the above ranges.

[0062] According to the minimum pitch equation, users of optical inspection equipment can avoid overlaps by calculating the appropriate pitch of through-hole structures in the substrate using a calculation unit. For example, if the thickness t is 1000 μm and the diameter d is 100 μm, the pitch may be approximately 434 to 480 μm.

[0063] Figure 20 is a schematic diagram of an inspection image of a laser-modified substrate 500d according to one embodiment of the present disclosure. The minimum pitch equation can be applied before the substrate is laser-modified. In the minimum pitch equation, the diameter d represents the line width LW of the laser-modified region 510d. Therefore, the user of the optical inspection apparatus can avoid overlap by calculating the appropriate pitch for the laser-modified region 510d on the laser-modified substrate 500d using a calculation unit.

[0064] Figure 21 is a flowchart of the operation method 600 of the optical inspection apparatus. The operation method 600 of the optical inspection apparatus begins with step S1, in which the calculation unit (see Figure 1A) calculates the minimum pitch based on a predetermined line width LW and substrate thickness of the laser-modified region. As shown in Figure 20, before performing laser modification, the appropriate pitch p of the laser-modified region 510d can be determined by the predetermined line width LW and thickness t of the laser-modified substrate 500d. The operation method 600 of the optical inspection apparatus proceeds to step S2, in which laser modification is performed on the substrate to form multiple laser-modified regions.

[0065] Please refer to Figures 1A and 21. The operation method 600 of the optical inspection apparatus proceeds to step S3, in which the projection optical system 100 acquires an oblique projection image of the laser-modified region 510. The operation method 600 of the optical inspection apparatus proceeds to step S4, in which the digital microscope system 200 acquires a 2D interference image of the laser-modified region. In some embodiments, the order of steps S3 and S4 may be reversed.

[0066] The operation method 600 of the optical inspection apparatus proceeds to step S5, in which the calculation unit 300 analyzes the tilt projection image to obtain multiple parameters of the laser modification region 510, and also analyzes the 2D interferometric image to obtain stereoscope image data of the laser modification region 510 (i.e., Figures 3A to 3D and Figure 13).

[0067] The operation method 600 of the optical inspection apparatus proceeds to step S6, in which the calculation unit 300 calculates the minimum pitch based on a predetermined diameter of the etching through-hole and the thickness of the substrate. As shown in Figure 18, before performing the etching process, a predetermined diameter d and thickness t of the substrate 500b can be used to determine the appropriate pitch p of the etching through-hole 510b.

[0068] The optical inspection apparatus operation method 600 proceeds to step S7, in which a plurality of etched through-holes 510 are formed in the substrate 500. The optical inspection apparatus operation method 600 proceeds to step S8, in which an inclined projection image of the etched through-holes 510 is acquired by the projection optical system 100. The optical inspection apparatus operation method 600 proceeds to step S9, in which a 2D interference image of the etched through-holes is acquired by the digital microscope system 200. In some embodiments, the order of steps S8 and S9 may be reversed.

[0069] The operation method 600 of the optical inspection apparatus proceeds to step S10, in which the calculation unit 300 analyzes the inclined projection image to obtain multiple parameters of the etched through-hole 510, and also analyzes the 2D interference image to obtain stereoscope image data of the etched through-hole 510 (i.e., Figures 4-5, 11-12, 14A-14E, and 15).

[0070] In summary, the optical inspection device is a non-contact and non-destructive inspection method, allowing for real-time feedback. The overall shape and profile of the through-hole structure can be acquired by inclined projection images from the projection optical system and 2D interferometric images from the digital microscope system. Furthermore, multiple through-hole structures can be inspected simultaneously, reducing the time required to scan the substrate. The taper angles of the four corners of the through-hole structure can be inspected, allowing for the application of metal plating processes to form through-hole vias (i.e., metal conductors) with much smaller critical dimensions. Overlaps can be avoided by calculating the appropriate pitch of the through-hole structure according to the minimum pitch equation before performing laser modification or etching processes.

[0071] Although the present invention has been described in considerable detail with reference to certain embodiments, other embodiments are also possible. Accordingly, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.

[0072] Those skilled in the art will understand that various modifications and changes may be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, the present invention is intended to include modifications and variations of the present invention, insofar as they fall within the scope of the appended claims. [Explanation of Symbols]

[0073] 10: Optical inspection equipment 100: Projection optical system 110: Light source 120: Projection lens 130: Image sensor 200: Digital Microscope System 210: Laser light source 212: Incident light 230: Image sensor 300: Computation Unit 400: Carrier 500: Circuit board 500b: Circuit board 502: Reverse side 504: Front 510:Through hole structure 510a: Through-hole structure 510b: Through-hole structure 510c: Through-hole structure 510d: Laser modification region 600: Operation method of optical inspection equipment S1~S10: Process d: Diameter t: thickness AX1: First optical axis AX2: Second optical axis IM1: Oblique projection image IM2: Oblique projection image IM3: Oblique projection image IM4: Processed image IM5: 2D Interferometry IM6: 3D Image Stack IM7: 3D image IC: Internal crack DP: Depth LW: line width AN:Angle p: pitch TCD: Upper critical dimension MCD: Central Critical Dimension BCD: Lower critical dimension H1: First height H2: Second height CTA: Center tilt angle NCD: Narrowest critical dimension LTA: Upper left taper angle RTA: Right upper taper angle LBA: Lower left taper angle RBA: Lower right taper angle LR: Left side roughness RR: Right side roughness DS: Irradiation error or double irradiation PCD: Point Cloud Data α: Inspection angle P1: Crowded area P2: Dilute area

Claims

1. A projection optical system arranged to acquire inclined projection images of multiple through-hole structures in a substrate, A digital microscope system arranged to acquire 2D interferometric images, A computing unit is arranged to analyze the 2D interferometric image to acquire stereoscope image data and to analyze the tilted projection image to acquire multiple parameters of the multiple through-hole structures, and is electrically connected to the projection optical system and the digital microscope system. An optical inspection device equipped with the following features.

2. The aforementioned projection optical system is A light source is positioned to illuminate the back side of the substrate, A projection lens is positioned on the front side of the substrate and is arranged to acquire the inclined projection image of the plurality of through-hole structures, An image sensor arranged to record the image formed from the projection lens, The optical inspection apparatus according to claim 1, further comprising:

3. The optical inspection apparatus according to claim 2, wherein the projection lens of the projection optical system is a telecentric lens.

4. The optical inspection apparatus according to claim 1, wherein the calculation unit is arranged to execute an extended depth of focus algorithm or an all-in-focus algorithm to obtain the parameters of the plurality of through-hole structures.

5. The optical inspection apparatus according to claim 1, wherein the plurality of through-hole structures are etched through-holes, and the parameters include an upper critical dimension, a middle critical dimension, a lower critical dimension, a taper angle, a pitch, a diameter, a roughness, a height, and a center line.

6. The optical inspection apparatus according to claim 1, wherein the plurality of through-hole structures are laser-modified regions, and the parameters include depth, angle, pitch, density, line width, and internal cracks.

7. The aforementioned digital microscope system A laser light source positioned to emit incident light, An image sensor is arranged to record the 2D interference image formed from the incident light that has passed through the plurality of through-hole structures, The optical inspection apparatus according to claim 1, further comprising:

8. The optical inspection apparatus, The optical inspection apparatus according to claim 7, further comprising a carrier on which the substrate is mounted and whose distance from the image sensor is adjustable.

9. The optical inspection apparatus according to claim 1, wherein the calculation unit is arranged to execute a backpropagation reconstruction algorithm on the 2D interferometric image to obtain a 3D image stack of the plurality of through-hole structures.

10. The optical inspection apparatus according to claim 9, wherein the calculation unit is arranged to execute a double image removal algorithm on the 3D image stack.

11. The optical inspection apparatus according to claim 9, wherein the calculation unit is arranged to execute a super-resolution algorithm on the 3D image stack.

12. The optical inspection apparatus according to claim 1, wherein the plurality of through-hole structures are etched through-holes, and the stereoscope image data includes upper critical dimension, middle critical dimension, lower critical dimension, taper angle, upper roundness, lower roundness, pitch, diameter, height, axis, surface roughness, cross-sectional view, and map scan.

13. The optical inspection apparatus according to claim 1, wherein the plurality of through-hole structures are laser-modified regions, and the stereoscope image data includes laser modification accuracy and map scanning.

14. A process of forming multiple etched through-holes in a substrate, A step of acquiring a first inclined projection image of the plurality of etching through holes from the projection optical system, A step of acquiring a first 2D interference image of the plurality of etched through holes using a digital microscope system, The process involves analyzing the first tilt projection image using a computing unit to obtain multiple parameters, and analyzing the first 2D interferometric image to obtain stereoscope image data, A method for operating an optical inspection device equipped with the following features.

15. The method for operating an optical inspection apparatus according to claim 14, further comprising calculating the minimum pitch based on a predetermined diameter of the etching through-holes and the thickness of the substrate by the calculation unit before forming the plurality of etching through-holes in the substrate.

16. The step of acquiring the first inclined projection image of the plurality of etching through holes from the projection optical system is: Illuminating the back side of the substrate with a light source, The first inclined projection image of the plurality of etched through holes is obtained using a projection lens, The image formed by the projection lens is recorded by an image sensor, A method for operating an optical inspection apparatus according to claim 14, further comprising:

17. The step of acquiring the first 2D interference image of the plurality of etched through holes using the digital microscope system is as follows: The laser light source emits incident light toward the substrate, The image sensor records the image formed from the incident light that has passed through the plurality of etching through holes, A method for operating an optical inspection apparatus according to claim 14, further comprising:

18. The method for operating an optical inspection apparatus according to claim 14, further comprising the step of performing laser modification on the substrate to form a plurality of laser-modified regions before forming the plurality of etching through holes on the substrate.

19. The method for operating an optical inspection apparatus according to claim 18, further comprising: before performing the laser modification on the substrate to form the plurality of laser-modified regions, the calculation unit calculates the minimum pitch based on a predetermined line width of the laser-modified region and the thickness of the substrate.

20. A step of acquiring a second tilt projection image of the plurality of laser modification regions using the projection optical system, The process of acquiring a second 2D interference image of the plurality of laser-modified regions using the digital microscope system, A method for operating an optical inspection apparatus according to claim 19, further comprising:

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