Tomography scanning system and method for laser-modified regions

Abstract

This invention provides a tomographic scanning system and method for laser-modified regions. [Solution] The system comprises a light source 110, an objective lens 140, a filter 150a, a photodetector 160a, and a computing device 170. The light source generates fundamental frequency light to irradiate a solid material 200, and the solid material reflects, refracts, and scatters this light, generating nonlinear light in the laser-modified region. The objective lens is placed between the light source and the solid material and is used to adjust the position of the beam's focal plane and to scan the modified region along the thickness direction of the solid material by varying the focal length for each layer. The filter filters out the fundamental frequency light and retains the nonlinear light, and the photodetector detects the nonlinear light signal that has passed through the filter. The computing device processes and analyzes the collected signals to construct the three-dimensional geometric shape of the laser-modified region and obtain complete internal structure information.

Description

[[Technical Field]]

[0001] The present invention relates to a method and system for detecting a laser-modified region of a solid material. [[Background Art]]

[0002] With the rapid development of semiconductor packaging technology, the conventional Plated Through-Hole (PTH) technology has gradually become a bottleneck in high-frequency and high-density applications. Therefore, Through-Glass Via (TGV) technology has emerged as a new key technology. Since it can provide superior electrical properties, mechanical properties and thermal stability, it has become one of the key technologies for chip packaging in 5th / 6th generation mobile communication (5G / 6G), High-Performance Computing (HPC), 3D Integrated Circuit (3D-IC), Automotive Electronics, and Artificial Intelligence (AI).

[0003] As the core technology of the TGV process, the process includes Laser Modification, Wet Etching Formation, and Metallization Filling. Laser modification technology is a key process for forming high-precision through holes. By modifying the microstructure inside the glass substrate using a Femtosecond Laser (FL), the selectivity and accuracy of subsequent etching are improved.

[0004] Femtosecond laser technology uses ultrashort pulses (e.g., 10 -15The TGV technology is characterized by its ability to improve the quality and yield of through-hole processing by modifying the interior of the glass through a non-thermal effect resulting from the interaction of multiple photons between the glass material and the glass. The MHz / GHz pulse mode enables the laser modification technology to achieve extremely high processing efficiency. For example, in high-aspect-ratio (HAR, >1:80) through-hole structures, the processing time for a single hole can be reduced to 350 milliseconds. Furthermore, multi-beam parallel processing technologies such as Bessel beams and Acousto-Optic Deflectors (AODs) can increase production capacity to industrial-grade levels of 10,000 holes per second, giving TGV technology a further competitive edge in the market.

[0005] Another key effect of laser modification is the alteration of the chemical and physical properties of the glass. Irradiation with a femtosecond laser reduces the density of certain areas within the glass substrate, alters the refractive index, and redistributes stress. These changes improve the etching rate in the modified areas, resulting in etching selectivity of over 100:1 compared to the unmodified areas.

[0006] Incidentally, laser modification technology has been successfully extended not only to glass materials but also to high-hardness materials such as silicon carbide (SiC), and is just as key as it is in glass processing. Silicon carbide itself comes in various forms such as ingots, substrates, and bulk materials, and is widely applied in fields such as ingot cutting, semiconductor processes, pre-treatment for machining, and pre-treatment for chemical etching. To give an example of producing SiC wafers by cutting ingots, because SiC has extremely high hardness, conventional manufacturing processes have only been able to produce SiC wafers by cutting SiC ingots with a diamond wire saw. This not only reduces cutting efficiency but also wastes a large amount of material, resulting in continuously rising manufacturing costs.

[0007] To address the above challenges, a novel SiC ingot cutting technology has been developed that combines laser modification and external force separation. This technology utilizes an ultrafast laser (e.g., a femtosecond laser) to generate a multiphoton absorption effect within the silicon carbide, forming micro-explosion regions and micro-cracks. This significantly reduces the hardness and cohesive force of certain parts of the material, and by applying an external force, it becomes possible to rapidly peel the SiC ingot along the modified layer. This process significantly increases the cutting speed and effectively reduces material wear. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, conventional analysis of laser-modified regions remains limited by technical means. Currently, the only way to observe the cross-section of the laser-modified region of a SiC ingot is to use destructive techniques (e.g., scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), Raman spectroscopy, and nanoindentation techniques). It is difficult to non-destructively confirm the explosion region within the SiC ingot, as well as the extent and continuity of microcrack extension in three-dimensional space, making quality control of laser modification a technical bottleneck.

[0009] Therefore, increasing the selectivity of etching during the through-hole glass substrate (TGV) process, or achieving low wear and high-speed separation in SiC ingot processing, have both been essential elements for laser modification technology. However, whether applied to glass or silicon carbide materials, controlling the quality and uniformity of the laser-modified region remains a significant technical challenge to this day. For many years, inspection of laser-modified regions has relied mainly on automated optical inspection (AOI) systems, which can only perform two-dimensional image analysis of the material surface and cannot provide effective information about the three-dimensional structure of the laser-modified region located inside the material. When high aspect ratio through-holes or other three-dimensional contour laser-modified regions are formed inside the material, defects such as potential internal cracking, discontinuous stretching, and reduced chemical uniformity often occur, making immediate detection difficult and preventing accurate evaluation.

[0010] Currently, there is no inspection method on the market that can perform non-destructive, high-resolution 3D scanning of laser-modified areas. As a result, quality control of laser modification heavily relies on destructive analysis (e.g., SEM, Raman, EDS, nanoindentation), which is not only time-consuming and expensive but also cannot be applied to real-time or mass production flowchart quality control. This technical deficiency has limited the production capacity and yield of TGV and SiC laser processing, becoming a significant bottleneck.

[0011] Therefore, if a 3D scanning system with high transparency and high resolution can be introduced, it may be possible to achieve complete structural analysis and evaluation of the modified region even under non-destructive conditions, further enhancing the reliability and mass production capacity of TGV and SiC laser processing technologies. [Means for solving the problem]

[0012] To solve the above problems, the present invention employs the following means. A tomographic scanning method for a laser-modified region according to one aspect of the present invention includes: step a, setting a light source on a solid material having a laser-modified region; the light source generating fundamental frequency light so as to scan the solid material; the solid material reflecting, refracting, and scattering the fundamental frequency light; and the laser-modified region generating nonlinear light due to a nonlinear effect, wherein the wavelength of the fundamental frequency light is in the range of 1000 to 2200 nm and is permeable to the solid material; step b, setting an objective lens between the light source and the solid material; step c, setting a filter to retain the nonlinear light and filter the fundamental frequency light; step d, setting a photodetector on the filter and then receiving a plurality of signals of the nonlinear light generated from the laser-modified region; and passing through the objective lens. The process includes: step e, which positions the focal plane of the fundamental frequency light on the solid material and adjusts the distance from the objective lens to the solid material so as to cover the laser modification region, so that the nonlinear light first passes through the filter before reaching the photodetector, thereby enabling the detection of these signals of the nonlinear light; and step f, which overlaps with step e and gradually alters the distance from the objective lens to the solid material, gradually moving the focal plane of the fundamental frequency light that has passed through the objective lens along the thickness direction of the solid material, performing a tomographic scan on the laser modification region to collect these signals of the nonlinear light generated from multiple stationary positions of the laser modification region at the focal plane, thereby constructing the three-dimensional geometric shape of the laser modification region.

[0013] According to one embodiment of the present invention, the light source is an ultrashort pulse laser light source.

[0014] According to one embodiment of the present invention, the solid material is a glass solid material or a silicon carbide solid material.

[0015] According to one embodiment of the present invention, the filter retains the visible light of the third harmonic generation in the nonlinear light.

[0016] According to one embodiment of the present invention, the fundamental frequency light is an infrared laser with a wavelength of 1560 nm.

[0017] According to one embodiment of the present invention, the laser-modified region is formed in the solid material in order to pre-form through holes in the solid material.

[0018] Furthermore, in order to solve the above-mentioned problems and achieve the objectives, another embodiment of the present invention, a tomographic scanning system for a laser-modified region, comprises a light source, an objective lens, a filter, a photodetector, and a computing device. The light source is placed on a solid material having a laser-modified region and generates fundamental frequency light to scan the solid material. The solid material reflects, refracts, and scatters the fundamental frequency light, and the laser-modified region generates nonlinear light due to a nonlinear effect. The wavelength of the fundamental frequency light is in the range of 1000 to 2200 nm and is penetrating the solid material. The objective lens is placed between the light source and the solid material. The filter is used to retain the nonlinear light and to filter the fundamental frequency light. The photodetector is placed on the filter and is used to detect multiple signals of the nonlinear light generated from the laser-modified region. The computing device receives and processes the signals connected to the photodetector. The distance from the objective lens to the solid material is gradually altered so that the focal plane of the fundamental frequency light transmitted through the objective lens is gradually moved along the thickness direction of the solid material, and a tomographic scan is performed. At the same time, the photodetector is used to collect the signals of the nonlinear light generated from multiple stationary positions of the laser-modified region at the focal plane, and the computing device is used to construct the three-dimensional geometric shape of the laser-modified region.

[0019] According to one embodiment of the present invention, the light source is an ultrashort pulse laser light source.

[0020] According to one embodiment of the present invention, the photodetector is a photodiode, an avalanche photodiode, a charge-coupled device, a photomultiplier tube, or any combination thereof.

[0021] According to one embodiment of the present invention, the tomographic scanning method for a laser-modified region further comprises a galvanometer scanning system. The fundamental frequency light generated by the light source is first reflected by the galvanometer scanning system and then irradiated onto the solid material, so that the fundamental frequency light is adjusted to be positioned at the scanning position of the solid material.

[0022] According to one embodiment of the present invention, the solid material is a glass solid material or a silicon carbide solid material.

[0023] According to one embodiment of the present invention, the filter retains visible light generated by third harmonic generation in the nonlinear light.

[0024] According to one embodiment of the present invention, the laser-modified region is formed in the solid material to preliminarily form a through hole in the solid material. Effects of the Invention

[0025] The tomographic scanning system and method for a laser-modified region according to the present invention can perform real-time, non-destructive three-dimensional scanning, quickly provide structural analysis results of the laser-modified region, and monitor quality in real time.

[0026] At least the following matters will become apparent from the description of the specification and drawings set forth below. Brief Description of the Drawings

[0027] [Figure 1A] It is a schematic configuration diagram showing a tomographic scanning system for a laser-modified region according to one embodiment of the present invention. [Figure 1B] It is a schematic configuration diagram showing a tomographic scanning system for a laser-modified region according to another embodiment of the present invention. [Figure 2] This diagram shows a side view and cross-sectional image of a laser-modified region preceding the formation of a glass substrate with through holes according to one embodiment of the present invention, as well as a schematic diagram showing the inspection results of the laser-modified region. [Figure 3] An example of inspection results for a conventional laser-modified region, a precursor to forming a glass substrate with through holes according to another embodiment of the present invention, is shown. [Figure 4] An example of inspection results for an abnormal laser-modified region preceding the formation of a glass substrate with through holes according to another embodiment of the present invention is shown. [Figure 5] This is a schematic diagram showing the laser-modified region and microcracked surface of a silicon carbide ingot according to one embodiment of the present invention. [Figure 6A] These are a side view and a cross-sectional image showing the laser-modified region and microcrack surface of a silicon carbide ingot according to one embodiment of the present invention. [Figure 6B] These are a side view and a cross-sectional image showing the surface of a silicon carbide ingot with microcracks according to one embodiment of the present invention. [Modes for carrying out the invention]

[0028] The present invention will be described below through embodiments of the invention, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0029] The present invention provides a method for tomographic scanning of a laser-modified region of a solid material and the method thereof. This method and method can perform non-destructive, real-time 3D scanning of a solid material and rapidly provide structural analysis results of the laser-modified region. In the following description, the structure of the above-described method for tomographic scanning of a laser-modified region and the method for tomographic scanning of a solid material of a laser-modified region are illustrated.

[0030] To facilitate the reader's further understanding of embodiments of the present invention, several technical details are described and accompanied by corresponding drawings. However, these technical details are not necessary for all embodiments. Some widely known structures and components are schematically illustrated in the drawings to simplify their content. Terms such as "connection" and "installation" may refer to components directly located on other components, or to the presence of intermediate components connecting them. Relatively, terms such as "first," "second," and "third" are used only to distinguish components or parts and do not indicate their order. The directional terms "down" and "up" describe the relationship between components and include orientations of devices other than those shown in the figures.

[0031] To further elaborate on the implementation of the present invention, different aspects and specific embodiments will be described below. This is not limited to a specific form of implementation or operation, but includes features and steps of multiple specific embodiments. Different embodiments can achieve the same or equivalent functions and steps, demonstrating the flexibility of the present invention.

[0032] To facilitate explanation, the functions of the device will be described by dividing them into various functional units and / or functional modules. When implementing the present invention, these functional units or functional modules may be implemented with the same or multiple software and / or hardware. The present invention will be described based on flowcharts and / or block diagrams of the methods, devices, and computer program products of the embodiments. A device for realizing the above functions is formed by inputting computer program instructions into a processing unit and executing the instructions. These instructions can be executed by a processing unit of a general-purpose computer, a dedicated computer, an embedded processing unit, or other programmable design data processing equipment.

[0033] <Tomography scanning system for laser-modified areas> Figure 1A is a schematic diagram showing a tomographic scanning system for a laser-modified region according to one embodiment of the present invention. The tomographic scanning method 100 for a laser-modified region is mainly used to perform accurate non-destructive testing on a laser-modified solid material to construct its three-dimensional geometric shape, improving process monitoring capabilities and enhancing the accuracy and reliability of subsequent etching processes. In the example shown in Figure 1, the tomographic scanning method 100 for a laser-modified region comprises a light source 110, a galvanometer scanning system 120, an objective lens 140, a filter 150a, a photodetector 160a, and a computing device 170. The combination of these components enables a highly efficient optical signal filter and high-resolution scanning of the laser-modified region.

[0034] The light source 110 is installed on a solid material 200 (shown as a substrate in Figure 1A) having a laser-modified region (not shown in Figure 1) and is used to generate fundamental frequency light 180. The fundamental frequency light 180 is irradiated onto the solid material 200, causing reflection, refraction, and scattering phenomena within the solid material 200. Furthermore, when the fundamental frequency light 180 is irradiated onto the laser-modified region, the nonlinear optical properties of the laser-modified region cause the laser-modified region to generate nonlinear light 180a, further increasing the inspection sensitivity.

[0035] According to one embodiment of the present invention, the light source 110 may be a short-pulse laser light source, for example, a femtosecond or picosecond laser light source, and the pulse width range is 10 -15 ~10 -12The wavelength is set to a range of seconds, ensuring high transmittance and precise temporal resolution, and is suitable for generating nonlinear optical effects. Furthermore, the fundamental frequency light 180 generated by the light source 110 is near-infrared (NIR), and the wavelength may be in the range of 1000 to 2200 nm, for example, 1050 nm or 1560 nm. Laser light in this wavelength range can not only effectively penetrate solid materials such as glass and silicon carbide, but can also generate remarkable nonlinear optical phenomena such as third-harmonic generation (THG), further enhancing the optical contrast between the laser-modified region and the surrounding unmodified region, and contributing to the inspection of the laser-modified region.

[0036] According to one embodiment of the present invention, the solid material 200 is, for example, a solid material, a silicon carbide solid material, or another insulating solid material, the glass solid material is, for example, a glass substrate, and the silicon carbide solid material is, for example, a silicon carbide ingot, a silicon carbide substrate, or a silicon carbide bulk material. When the solid material 200 is a glass substrate, its thickness is in the range of 5 to 3,000 μm to suit the needs of different packaging technologies. Furthermore, after laser modification, the physical and optical properties of the glass substrate change significantly, for example, the refractive index is altered, the density decreases, and the internal stress is redistributed. Since these changes affect subsequent etching, the process accuracy is improved by effectively monitoring these parameters using the tomographic scanning method 100 of the laser-modified region of the present invention.

[0037] The galvanometer scanning system 120 may be installed in the direction of the advance of the light beam emitted from the light source 110 and serves as a core component of the optical scanning control. Its main function is to adjust and guide the fundamental frequency light 180 from the light source 110, and to dynamically change the incident position on the solid material 200 during the scanning process, thereby increasing the flexibility and resolution of the overall optical inspection. As the fundamental frequency light 180 passes through the galvanometer scanning system 120, the galvanometer scanning system 120 rapidly adjusts its angle relative to the beam to ensure that the laser light scans the surface of the solid material 200 uniformly and to enable complete scanning of laser-modified regions in different areas of the solid material 200.

[0038] The galvanometer scanning system 120 operates primarily by using a high-speed oscillating galvanometer mirror to precisely deflect the beam, thereby altering the scanning position of the fundamental frequency light 180 in the solid material 200. This technology provides extremely fast scanning speeds and minimal delay, allowing the inspection system to capture and analyze optical signals in real time. Furthermore, by adjusting the control parameters of the galvanometer scanning system 120, the scanning range, beam overlap accuracy, and scanning speed can be further improved, making it applicable to different types of solid materials and laser modification conditions.

[0039] The objective lens 140 is positioned between the galvanometer scanning system 120 and the solid material 200, serving as a core component for collecting and focusing optical signals. Its main function is to ensure that the fundamental frequency light 180a reflected from the galvanometer scanning system 120 is precisely focused onto the solid material 200, while also improving the collection efficiency of the nonlinear optical signal 190a from the solid material 200, thereby enhancing the overall inspection effect.

[0040] According to one embodiment of the present invention, the objective lens 140 has a high numerical aperture (NA), and this design enhances the efficiency of generating nonlinear optical signals. The objective lens 140 with a high numerical aperture can provide higher optical field focusing capability, and the fundamental frequency light 180a generates stronger nonlinear effects, such as third-harmonic generation (THG), within the solid material 200, thereby increasing the optical signal contrast between the laser-modified and unmodified regions and improving inspection sensitivity.

[0041] According to another embodiment of the present invention, the objective lens 140 with a high numerical aperture not only enhances the efficiency of generating nonlinear light but also optimizes the collection performance of nonlinear light. This means that the objective lens 140 can enhance the signal intensity collected by the photodetector 160a, thereby increasing the signal-to-noise ratio (SNR) and ensuring high accuracy and stability of the optical signal. The high SNR reduces the interference of background noise on the inspection results, further clarifies the visualization of the structure of the laser-modified region, and further improves the ability of the tomographic scanning method 100 to distinguish the modified region from the laser-modified region.

[0042] Furthermore, the selection of the objective lens 140 also affects the system's resolution and depth of focus (DOF). By appropriately adjusting the NA value, it is ensured that the fundamental frequency light 180 is precisely focused at different depths within the solid material 200, thereby obtaining accurate three-dimensional structural information during the tomographic scanning process.

[0043] Due to the optical properties of the optimized objective lens 140, the tomographic scanning method 100 of the laser-modified region effectively improves the imaging quality of the laser-modified region, and enables the subsequent photodetector 160a to acquire a high-resolution optical signal, making it suitable for constructing an accurate three-dimensional structural model.

[0044] The filter 150a is installed below the solid material 200, and its main function is to selectively retain the nonlinear light 190a from the solid material 200, while effectively filtering out the fundamental frequency light 180a, ensuring that the subsequent detection system receives only the nonlinear optical signal from the laser-modified region. After the laser-modified region is treated with a femtosecond or picosecond laser, its optical properties change, and nonlinear optical phenomena occur in the laser-modified region, such as the generation of a refractive index gradient or alteration of the stress distribution. Therefore, ensuring the purity and accuracy of the inspection signal is important when designing the filter 150a.

[0045] According to one embodiment of the present invention, the filter 150a selectively transmits nonlinear light 190a from the solid material 200, and in particular retains the nonlinear optical signal of the third harmonic generation (THG) of the fundamental frequency light 180a. The wavelength of the third harmonic generation optical signal is one-third of the wavelength of the fundamental frequency light. For example, if the wavelength of the fundamental frequency light 180a is 1560 nm, the generated third harmonic generation light is 520 nm, which is within the visible light range. The filter 150a precisely filters out light within this wavelength range, ensuring that the photodetector 160a receives only the valuable nonlinear light signal, thereby improving the sensitivity and accuracy of the optical measurement.

[0046] By using a highly selective filter 150a, the background fundamental frequency light signal 180a from the solid material 200 is effectively removed, reducing noise interference and improving the resolution of the tomographic scanning method 100 for the laser-modified region. This design enables the photodetector 160a to acquire clear, high-contrast images of the laser-modified region, helping to accurately construct a three-dimensional structural model of the laser-modified region.

[0047] The photodetector 160a is installed below the filter 150a, and its main function is to detect and record the nonlinear light 190a that has passed through the filter 150a, and to convert the collected optical signal into an analyzable electrical signal. Since the intensity of the nonlinear light 190a is usually lower than that of the fundamental frequency light 180a, the sensitivity of the photodetector 160a directly affects the inspection accuracy of the system and the quality of the signal. Therefore, a highly sensitive photodetector is selected to effectively capture even weak nonlinear optical signals and convert them into stable electronic data.

[0048] According to one embodiment of the present invention, the photodetector 160a can use a variety of highly efficient photoelectric sensors, such as photodiodes (PDs), avalanche photodiodes (APDs), charge-coupled devices (CCDs), photomultiplier tubes (PMTs), or any combination thereof. Photodiodes are applied to general optical detection applications and have high sensitivity and low noise characteristics. Avalanche photodiodes, through their internal gain mechanism, provide higher photoelectric conversion efficiency than general PDs, making them suitable for detecting low-intensity optical signals. Charge-coupled devices can be used for capturing high-resolution images and are suitable for optical tomography scanning applications. Photomultiplier tubes have extremely high photon gain capability and can detect extremely low-intensity optical signals, and are particularly applicable to the detection of high-precision nonlinear optical signals.

[0049] The computing unit 170 receives a signal from the photodetector 160a and is responsible for receiving, processing, and analyzing the nonlinear light signal 190a from the photodetector 160a. Since the laser modification region tomography scanning system 100 needs to perform high-resolution imaging of the modified region inside the solid material 200, the computing unit 170 needs to have powerful data processing capabilities in order to accurately reconstruct the three-dimensional geometric shape of the laser modification region.

[0050] For example, to provide a more precise structural analysis of the modified region, the tomographic scanning method 100 of the laser modified region employs Layered Focal Plane Scanning (FOP) technology to reconstruct a three-dimensional image of the laser modified region by collecting nonlinear optical signals from different focal layers. In this process, the computing unit 170 performs image stacking to increase image resolution and enhance edge contrast. This technology allows for precise visualization of the microstructure of the laser modified region, as well as identification of changes in refractive index, stress distribution, and structural integrity within the laser modified region. Furthermore, an image comparison algorithm enables the computing unit 170 to compare the laser modified region with its original design shape to evaluate whether the laser modification effect conforms to the expected specifications.

[0051] Figure 1B is another schematic diagram showing a tomographic scanning system for a laser-modified region according to another embodiment of the present invention. Compared to the structure shown in Figure 1A, this embodiment mainly adds a dichroic mirror 130 and modifies the layout of the filter 150b and photodetector 160b, providing a different optical signal acquisition method. In this design, the tomographic scanning method 100 for the laser-modified region still includes a light source 110, a galvanometer scanning system 120, an objective lens 140, a filter 150b, a photodetector 160b, and a computing device 170, and the combination of each component realizes a highly efficient optical signal filter and high-resolution scanning of the laser-modified region.

[0052] According to Figure 1B, this embodiment differs from Figure 1 in 53 points, in that a dichroic mirror 130 is added between the galvanometer scanning system 120 and the objective lens 140. Furthermore, the layout of the filter 150b and the photodetector 160b has been adjusted so that they are positioned above the solid material 200.

[0053] In the structure shown in Figure 1B, fundamental frequency light 180 is emitted from the light source 110 and adjusted by the galvanometer scanning system 120. The beam then first passes through the dichroic mirror 130 and is focused onto the solid material 200 by the objective lens 140. When the beam irradiates the laser-modified region of the solid material 200, a nonlinear optical effect occurs, generating nonlinear light 190b. The optical signal generated inside the solid material 200 (including fundamental frequency light 180b and nonlinear light 190b) propagates outward, is reflected by the dichroic mirror 130 located in the optical path, and is guided to the filter 150b located above. The filter 150b filters out the fundamental frequency light 180b and retains only the nonlinear light 190b, after which the photodetector 160b located behind it can receive only the nonlinear optical signal.

[0054] The remaining portion of Figure 1B is the same as Figure 1A, so its explanation is omitted here.

[0055] <Tomographic scanning method for laser-modified areas> To obtain a high-resolution 3D shape of the laser-modified region, the tomographic scanning method 100 of the laser-modified region employs sequential scanning technology and reconstructs a complete 3D image by adjusting the position of the focal plane. The scanning process is as follows:

[0056] First, the solid material 200 is placed below the objective lens 140 to ensure alignment and stability of the optical system. Next, the fundamental frequency light 180a generated from the light source 110 is first reflected by the galvanometer scanning system 120, then passes through the objective lens 140, and the focal plane of the fundamental frequency light is located on the upper surface of the solid material 200. At this point, the system begins sequential scanning of the laser-modified region to obtain complete structural information of the region.

[0057] During the scanning process, by gradually adjusting the distance between the objective lens 140 and the solid material 200, the focal plane of the fundamental frequency light 180 transmitted through the objective lens 140 gradually moves downward along the thickness direction of the solid material 200 and reaches the bottom surface of the solid material 200. As the focal plane moves, layers of different depths within the laser-modified region are sequentially excited by the fundamental frequency light 180, generating the corresponding nonlinear light 190a or 190b.

[0058] At each focal plane, a nonlinear optical signal 190a or 190b from the laser-modified region is received by a photodetector 160a or 160b, respectively. When the arrangement shown in Figure 1A is adopted for the tomographic scanning method 100 of the laser-modified region based on a different scanning structure, the photodetector 160a collects the nonlinear light 190a that has passed through the filter 150a. When the arrangement shown in Figure 1B is adopted for the system, the nonlinear light 190b is reflected by the dichroic mirror 130, passes through the filter 150b, and is detected by the photodetector 160b.

[0059] The collected optical signals are transmitted to the computing unit 170, where signal processing, image reconstruction, and 3D geometric shape analysis are performed. Using Layered Focal Plane Scanning technology, the computing unit 170 stacks the nonlinear optical signals acquired at different focal plane positions as a complete 3D structural image of the laser-modified region, further analyzing the structural characteristics and quality of the laser-modified region to ensure the accuracy of subsequent etching and processing steps.

[0060] Through the scanning method described above, the tomography scanning system 100 according to the present invention provides a high-resolution and non-destructive laser-modified region inspection technology, enabling accurate identification of structural changes within the laser-modified region and further improving the reliability and production efficiency of the TGV process and silicon carbide machining.

[0061] *Experimental Example 1: Inspection of laser-modified areas on a glass substrate Figure 2 is a schematic diagram showing a side view and cross-sectional image of a laser-modified region before forming a glass through-electrode according to one embodiment of the present invention, as well as the inspection results of the laser-modified region. In the third harmonic optical image 210 of the side view of the predecessor of the glass substrate with a through-hole in Figure 2, the laser-modified region 230 can be clearly observed, and is characterized by the presence of a region through which light is transmitted to the black glass substrate 220, indicating that the laser-modified region 230 has been subjected to laser modification treatment. This image shows the characteristic shape of the laser-modified region 230 and is useful in determining the integrity and uniformity of the laser-modified region 230.

[0062] The upper right of Figure 2 is a schematic diagram showing the side structure of a glass substrate 220 having a laser-modified region 230. The images of laser-modified regions 240-270 show a classification of different modification results. Laser-modified region 240 is a completely modified, successful, and normal laser-modified region, with a uniform shape and no defects. Laser-modified regions 250-260 are abnormal laser-modified regions where modification was unsuccessful in some areas, possibly due to uneven laser energy or incomplete modification due to defects within the substrate. Laser-modified region 270 shows an abnormal phenomenon where modification is uneven within the laser-modified region, which may affect the selectivity in the subsequent etching process and the quality of through-hole formation.

[0063] Furthermore, the example in Figure 2 also shows third-harmonic optical images 280-290 of the cross-section of the predecessor glass substrate with through holes. Third-harmonic optical image 290 of the cross-section of the predecessor glass substrate with through holes shows a normal laser-modified region, with a uniform cross-sectional shape and consistent optical characteristics. Third-harmonic optical image 280 of the cross-section of the predecessor glass substrate with through holes shows an abnormal laser-modified region, which may include fractures, voids, or other irregular shapes, and may have been subjected to internal stress in the substrate, a shift in the laser focus, or other fluctuations during the modification process.

[0064] Figure 3 shows an example of inspection results of a normal laser-modified region before forming a through-hole electrode according to another embodiment of the present invention. In the example of Figure 3, a third harmonic optical image 300 of the laser-modified region of the predecessor of the through-hole glass substrate is shown, and the uniformity and completeness of the laser-modified region are further analyzed by cross-sectional images at different depth positions. In the example of Figure 3, third harmonic optical images 310 to 330 are shown at depths of -60 μm, -300 μm, and -540 μm inside the glass substrate, and it is shown that the cross-sectional shape and number of laser-modified regions are maintained to a considerable extent even at different depths, indicating that the modification process is stable and has high reproducibility. Such a uniform laser-modified region can ensure consistency in through-hole formation in the subsequent wet etching process, and can further improve the reliability and yield of the TGV process.

[0065] Figure 4 shows an example of inspection results of an abnormal laser-modified region before forming a glass through-hole electrode according to another embodiment of the present invention. In the example of Figure 4, a third harmonic optical image 400 of the side of the laser-modified region of the predecessor of the glass substrate with through-holes is shown, and third harmonic optical images 410-450 of cross-sections at different depth positions are shown. In the example of Figure 4, analysis of the laser-modified region of the predecessor of the glass substrate with through-holes at different depths (0 μm, -402 μm, -524 μm, -580 μm, -700 μm) reveals that in the cross-sectional images at certain depths, the partial laser-modified region is not fully displayed, indicating that an interruption phenomenon is occurring.

[0066] Specifically, when the depth is 0 μm, the third harmonic optical image 440 shows an image of the top surface of the glass substrate. When the depth is -700 μm, the third harmonic optical image 450 shows an image of the bottom surface of the glass substrate. Third harmonic optical images 410-430 in the intermediate depth region do not show a continuous partial laser modification region, indicating that the laser modification region does not penetrate the entire glass substrate. This may be due to a shift in the laser focus, influence from internal stress in the material, or attenuation of laser energy, resulting in a non-uniform laser modification region. These abnormal phenomena may affect the uniformity of the subsequent wet etching process, leading to incomplete through-hole shapes and potentially impacting the electrical properties and structural strength of the TGV.

[0067] As described above, third-harmonic optical imaging technology allows for real-time inspection of the integrity of the laser-modified area before etching, enabling early detection and correction of process problems, thereby improving the yield and reliability of glass substrates with through holes.

[0068] *Experimental Example 2: Inspection of the laser-modified area of ​​a silicon carbide ingot Silicon carbide (SiC) is not easy to grow crystals, and its ingots typically have a diameter between approximately 4 and 8 inches (10 to 20 cm) and a thickness between approximately 10 and 25 mm. In practical applications, silicon carbide ingots need to be cut into wafers with a thickness between 150 and 350 μm. Because silicon carbide is extremely hard and conventional cutting methods are not easy, the industry has introduced "laser modification technology" to improve cutting efficiency and quality and reduce material wear.

[0069] Figure 5 is a schematic diagram showing the laser-modified region and microcrack surface of a silicon carbide ingot according to one embodiment of the present invention. The top schematic diagram of the silicon carbide ingot is shown above, and the side schematic diagram of the silicon carbide ingot is shown below. When modification is performed using a femtosecond laser, first the laser is concentrated on the laser-modified region 510 inside the silicon carbide ingot 500, and after a large amount of energy is absorbed, the silicon carbide dissociates first into amorphous silicon and amorphous carbon, forming an initial modified layer. Then, the continuously irradiated laser light is absorbed by the amorphous carbon that was generated earlier, causing a volume expansion and resulting in a micro-explosion, and internal stress is generated inside the ingot 500, forming a microcrack modified layer in the laser-modified region 510. Next, the silicon carbide ingot 500 is vibrated by ultrasound, and the vibration energy is transmitted to the laser-modified region 510, guiding the further growth of microcracks and connecting them to the previously formed discontinuous cracks, ultimately forming a nearly continuous microcrack surface 520 within the ingot 500. At this time, by combining it with a vacuum suction cup and applying only tensile force, the ingot is easily separated as a wafer along the modified layer, and damage caused by forcible separation is effectively prevented.

[0070] Figure 6A is a side view and a cross-sectional image showing the laser-modified region and microcrack surface of a silicon carbide ingot according to one embodiment of the present invention. This image corresponds to region 530 in Figure 5. In the example of Figure 6A, the laser modification depth of the silicon carbide ingot 600 is 180 μm. The white light optical image 660 located below Figure 6A is an image obtained at a focal depth of 50 μm on the surface of the ingot 600 using a general optical microscope and white light illumination. Since the above method cannot distinguish between the laser-modified region 610 and the microcrack surface 620 at different depths, it is necessary to obtain more accurate information by observing the third harmonic generated light.

[0071] In the upper right of Figure 6A, a third harmonic optical image 630 of the side view of the silicon carbide ingot 600 is shown, and in the upper left, a third harmonic optical image 640 of a cross-sectional image of the surface at a depth of 170 μm and a third harmonic optical image 650 of a cross-sectional image of the surface at a depth of 180 μm are shown, respectively. In the third harmonic optical image 650, it can be seen that the intensity of the third harmonic generated light from both sides of the laser-modified region 610 is different, proving that there is a difference in depth between the microcrack surfaces 620 on both sides of the laser-modified region 610, which is the same as the microcrack surface 520 shown in the lower side view of Figure 5.

[0072] Figure 6B is a side view and a cross-sectional image showing the microcrack surface of a silicon carbide ingot according to one embodiment of the present invention, where the image shown in Figure 6A corresponds to region 540 shown in Figure 5. The right side of Figure 6B shows a third harmonic optical image 670 of the side of the silicon carbide ingot 600, and the left side shows a third harmonic optical image 680 of the top view at the depth of the surface, and a third harmonic optical image 690 of the cross-sectional image at a depth of 180 μm of the surface, respectively. By comparing third harmonic optical images at different depth positions, the formation and extension of the laser-modified region and the surrounding microcrack surface can be observed more clearly.

[0073] Advanced optical inspection techniques, such as tomography scanning, allow for clear identification of micro-explosion regions and micro-crack development caused by laser modification within silicon carbide ingots, and further determination of the depth and structural characteristics of the modified regions. These observations not only assist in optimizing laser processing parameters but also improve cutting efficiency and quality, providing more accurate evaluation and technical support for subsequent applications of laser modification to glass substrates and silicon carbide materials.

[0074] The tomographic scanning method for laser-modified regions according to the present invention provides a high-resolution, non-destructive, real-time three-dimensional scanning technology that can accurately observe and evaluate the quality of laser-modified regions within solid materials (including glass substrates and silicon carbide ingots), overcoming the limitations of conventional inspection methods. This tomographic scanning method for laser-modified regions is not only applicable to the inspection of laser-modified regions of glass substrates with through-holes, but can also be further extended to the observation of micro-explosion areas and micro-crack surfaces formed in laser-modified regions of silicon carbide materials, comprehensively improving the reliability and yield of the entire process.

[0075] The tomography scanning system employs fundamental frequency optical excitation and nonlinear optical effects, and uses sequential scanning technology to construct a three-dimensional structural model of the laser-modified region, providing complete and detailed internal modification information while maintaining sample integrity without damaging the glass substrate or silicon carbide ingot. A high numerical aperture objective lens and ultrashort pulse laser enable the scanning system to achieve submicron level resolution (<0.5 μm), allowing for accurate detection of the three-dimensional structure of the laser-modified region and the defect distribution generated by micro-explosions within the silicon carbide material.

[0076] When applied to glass substrate processes with through-holes, real-time monitoring of laser modification after the laser modification process and before the wet etching process prevents abnormal modifications from affecting the quality of the subsequent etching process. Unlike conventional automated optical inspection (AOI), which can only observe the surface of the substrate, this scanning system can inspect deeply into the laser-modified region within the material, quickly identifying whether the laser modification is complete and detecting abnormal areas that may affect the etching or machining process, such as incomplete modification, non-uniformity of the modified region, and cracking problems. For laser-modified silicon carbide ingots, this system can also detect the direction and depth of microcracks caused by micro-explosions, contributing to the optimization of cutting parameters and reducing material wear.

[0077] The tomography scanning system according to the present invention is particularly applicable to high aspect ratio through-hole processes, and especially to glass substrates with through-holes having an aspect ratio exceeding 1:80. Image stacking technology allows for consistent shape and quantity of laser-modified regions at different depths, improving the stability of subsequent wet etching processes and further enhancing the uniformity of through-holes. Furthermore, this system can perform three-dimensional scanning of laser-modified regions in thicker or differently shaped silicon carbide ingots, maintaining the continuity and integrity of the modified regions and further improving the efficiency and yield of silicon carbide material processing.

[0078] In summary, the present invention provides a high-resolution, real-time, and non-destructive laser modification region inspection technology, enabling the resolution of inspection bottlenecks in glass substrate TGV processes and silicon carbide ingot machining. Through nonlinear optical effects and optical signal filtering technology, the tomographic scanning system according to the present invention can accurately scan laser modification regions within solid materials and monitor quality in real time. Whether it be the pre-modified region of a glass substrate with through holes, or modified regions and microcracks formed by micro-explosions in a silicon carbide ingot, all are completely reconstructed and measured, ensuring process stability and the reliability of the final product.

[0079] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention. [Explanation of Symbols]

[0080] 100 Tomography Scanning System 110 Light source 120 Galvanometer Scanning System 130 Dichroic Mirror 140 objective lens 150a filter 150b filter 160a photodetector 160b photodetector 170 Arithmetic equipment 180 fundamental frequency light 180a fundamental frequency light 180b fundamental frequency light 190a Nonlinear light 190b Nonlinear light 200 solid materials 210 Third harmonic optical image 280 Third harmonic optical image 290 Third harmonic optical image 220 glass substrates 230 Laser modification area 240 Laser modification area 250 Laser Modification Areas 260 Laser modification area 270 Laser modification area 300 Third harmonic optical image 310 Third harmonic optical image 320 Third harmonic optical image 330 Third harmonic optical image 400 Third harmonic optical image 410 Third harmonic optical image 420 Third harmonic optical image 430 Third harmonic optical image 440 Third harmonic optical image 450 Third harmonic optical image 500 silicon carbide ingots 510 Laser modification area 520 Microcracked surface 530, 540 area 600 silicon carbide ingots 610 Laser modification area 620 Microcracked surface 630 Third harmonic optical image 640 Third harmonic optical image 650 Third harmonic optical image 660 White Light Optical Image 670 Third High-Mode Optical Image 680 Third High-Mode Optical Image

Claims

1. Step a comprises:

1. Setting a light source on a solid material having a laser-modified region; 2. The light source generates fundamental frequency light so as to scan the solid material; 3. The solid material reflects, refracts, and scatters the fundamental frequency light; 4. The laser-modified region generates nonlinear light due to a nonlinear effect; 5. The wavelength of the fundamental frequency light is in the range of 1000 to 2200 nm and is permeable to the solid material. Step b involves placing the objective lens between the light source and the solid material, Step c includes setting up a filter to retain the nonlinear light and filter out the fundamental frequency light, Step d involves installing a photodetector on the filter and then receiving multiple signals of the nonlinear light generated from the laser modification region. Step e involves positioning the focal plane of the fundamental frequency light transmitted through the objective lens on the solid material and adjusting the distance from the objective lens to the solid material so as to cover the laser modification region, thereby enabling the detection of these signals of the nonlinear light by first passing through the filter before reaching the photodetector. A method for tomographic scanning of a laser-modified region, characterized by including step f, which overlaps with step e, and further includes step f, which involves gradually changing the distance from the objective lens to the solid material, gradually moving the focal plane of the fundamental frequency light transmitted through the objective lens along the thickness direction of the solid material, performing tomographic scanning of the laser-modified region, and collecting the signals of the nonlinear light generated from multiple stationary positions of the laser-modified region at the focal plane to construct the three-dimensional geometric shape of the laser-modified region.

2. The tomographic scanning method for a laser-modified region according to claim 1, characterized in that the light source is an ultrashort pulse laser light source.

3. The method for tomographic scanning of a laser-modified region according to claim 1, characterized in that the solid material is a glass solid material or a silicon carbide solid material.

4. The tomographic scanning method for a laser-modified region according to claim 3, characterized in that the filter retains visible light from the third harmonic generation in the nonlinear light.

5. The tomographic scanning method for a laser-modified region according to claim 3, characterized in that the fundamental frequency light is an infrared laser with a wavelength of 1050 nm or 1560 nm.

6. A tomographic scanning method for a laser-modified region according to any one of claims 1 to 5, characterized in that a through hole is formed in the solid material, or the solid material is cut in a preliminary manner to form the laser-modified region in the solid material.

7. A light source installed on a solid material having a laser-modified region, which generates fundamental frequency light for scanning the solid material, wherein the solid material reflects, refracts, and scatters the fundamental frequency light, and the laser-modified region generates nonlinear light due to a nonlinear effect, wherein the wavelength of the fundamental frequency light is in the range of 1000 to 2200 nm, and the light source is capable of penetrating the solid material. An objective lens is installed between the light source and the solid material, A filter that retains the aforementioned nonlinear light and filters out the aforementioned fundamental frequency light, A photodetector, which is installed in the filter, is used to detect multiple signals of the nonlinear light generated from the laser-modified region, The photodetector is connected to a arithmetic unit that receives and processes these signals, A tomographic scanning system for a laser-modified region, characterized by gradually changing the distance from the objective lens to the solid material so as to gradually move the focal plane of the fundamental frequency light transmitted through the objective lens along the thickness direction of the solid material, performing tomographic scanning, collecting the signals of the nonlinear light generated from multiple stationary positions of the laser-modified region at the focal plane using the photodetector, and constructing the three-dimensional geometric shape of the laser-modified region using the computing device.

8. The tomographic scanning system for a laser-modified region according to claim 7, characterized in that the light source is an ultrashort pulse laser light source.

9. The tomographic scanning system for a laser-modified region according to claim 7, characterized in that the photodetector is a photodiode, an avalanche photodiode, a charge-coupled element, a photomultiplier tube, or any combination thereof.

10. The tomography scanning system for a laser-modified region according to claim 7, further comprising a galvanometer scanning system installed in front of the light source, wherein the fundamental frequency light generated by the light source is first reflected by the galvanometer scanning system and then irradiated onto the solid material, thereby modifying the fundamental frequency light to be located at the scanning position of the solid material.

11. The tomographic scanning system for a laser-modified region according to claim 7, characterized in that the solid material is a glass solid material or a silicon carbide solid material.

12. The tomography scanning system for a laser-modified region according to claim 11, characterized in that the filter retains visible light from the third harmonic generation in the nonlinear light.

13. A tomographic scanning system for a laser-modified region according to any one of claims 7 to 12, characterized in that a through hole is formed in the solid material, or the solid material is cut in order to form the laser-modified region in the solid material.

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