Laser-modified zone tomography system and method

Abstract

A tomography system and method for laser-modified zone is provided. The system includes a light source, an objective lens, a filter, a light detector, and a computing device. The light source generates a fundamental light, which is irradiated to a solid material to be reflected, refracted, and scattered, and to generate a nonlinear light at a laser-modified zone. The objective lens is disposed between the light source and the solid material, and is configured to adjust a focal plane position of the light beam and to scan the laser-modified zone along a thickness direction of the solid material by changing the focal length layer by layer. The filter filters the fundamental light and retains the nonlinear light. The light detector detects a nonlinear light signal passing through the filter and transmits data to the computing device. The computing device processes and analyzes the collected signal to construct a three-dimensional geometry of the laser-modified zone to obtain complete internal structure information.

Description

Technical Field

[0001] This invention relates to a method and system for detecting laser-modified regions of solid materials. Background Technology

[0002] With the rapid development of semiconductor packaging technology, traditional plated through-hole (PTH) technology is gradually facing technical bottlenecks in high-frequency and high-density applications. Against this backdrop, through-glass via (TGV) technology has emerged as a new key technology, offering superior electrical, mechanical, and thermal stability. This makes it one of the key technologies for chip packaging in 5G / 6G mobile communications, high-performance computing (HPC), 3D integrated circuits (3D-IC), automotive electronics, and artificial intelligence (AI).

[0003] The core technologies of the TGV process include laser modification, wet etching formation, and metallization filling. Among them, laser modification is a key step to ensure the formation of high-precision vias. It can change the microstructure inside the glass substrate through femtosecond laser (FL) to improve the selectivity and accuracy of subsequent etching.

[0004] The characteristic of femtosecond laser technology lies in its ultrashort pulses (such as 10^6 pulses). -15 This technology enables non-thermal modification of the glass through the interaction between multiphotons and the glass material, improving the quality and yield of through-hole processing. Using MHz / GHz pulse modes, laser modification technology achieves extremely high processing efficiency, such as for high aspect ratio (HAR, >1:80) through-hole structures, with single-hole processing time reduced to as low as 350 milliseconds. Furthermore, multi-beam parallel processing technologies, such as Bessel beams or Acousto-Optic Deflectors (AOD), can increase throughput to industrial-grade levels of 10,000 holes per second, making TGV technology even more competitive in the market.

[0005] Another key effect of laser modification lies in the alteration of the chemical and physical properties of the glass. After femtosecond laser irradiation, localized areas within the glass substrate experience density reduction, refractive index changes, and stress redistribution. These changes increase the etching rate of the modified areas, resulting in an etching selectivity of over 100:1 compared to the unmodified areas.

[0006] It is worth mentioning that laser modification technology can be applied not only to glass materials but has also been successfully extended to high-hardness materials such as silicon carbide (SiC), demonstrating advantages as crucial as those in glass processing. Silicon carbide itself can exist in various forms, including ingots, substrates, and bulk materials, and is widely used in ingot cutting, semiconductor manufacturing processes, pre-processing for machining, and pre-processing for chemical etching. Taking the cutting of ingots to produce SiC wafers as an example, due to the extremely high hardness of SiC, traditional manufacturing processes can only rely on diamond wire saws to cut SiC ingots to produce SiC wafers. This not only results in low cutting efficiency but also generates a large amount of material waste, leading to a continuous increase in manufacturing costs.

[0007] To address the aforementioned issues, a novel SiC ingot cutting technology combining laser modification and external force separation has been developed. This technology utilizes ultrafast lasers (such as femtosecond lasers) to generate a multiphoton absorption effect within silicon carbide, inducing the formation of micro-explosion zones and microcracks. This significantly reduces the local hardness and cohesion of the material, allowing for rapid peeling of the SiC ingot along the modified layer by applying external force. This process significantly increases the cutting rate and effectively reduces material loss.

[0008] However, the analysis of laser-modified regions is currently limited by technical means. At present, only destructive techniques (such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy, and nanoindentation techniques) can be used to observe the cross-section of the laser-modified region of SiC ingots. It is difficult to non-destructively confirm the extension range and continuity of the explosion zone and microcracks in three-dimensional space in SiC ingots, which has become a technical bottleneck for the quality control of laser modification.

[0009] Therefore, laser modification technology plays an indispensable role in improving etch selectivity in through-glass via (TGV) processes or in achieving low-loss, high-speed separation in SiC ingot processing. However, regardless of its application to glass or silicon carbide materials, controlling the quality and uniformity of laser-modified regions remains a significant technical challenge. For a long time, the detection of laser-modified regions has primarily relied on Automated Optical Inspection (AOI) systems. These AOI systems can only perform two-dimensional image analysis on the material surface, providing almost no effective information about the three-dimensional structure of laser-modified regions located within the material. When high aspect ratio through-holes or other three-dimensional contours of laser-modified regions are formed within the material, potential defects such as internal cracks, discontinuous extension, and poor chemical homogeneity are often difficult to detect in real time, let alone accurately assess.

[0010] Currently, there is a lack of non-destructive, high-resolution 3D scanning detection solutions for laser-modified areas. This means that laser modification quality monitoring heavily relies on destructive analysis (such as SEM, Raman spectroscopy, EDS, and nano-indentation) for post-processing assessment. This is not only time-consuming and labor-intensive but also unsuitable for real-time or mass production quality control. This technological gap has become a significant bottleneck limiting the production capacity and yield of TGV and SiC laser processing. Summary of the Invention

[0011] Therefore, if a three-dimensional scanning system with high penetration and high resolution can be introduced, it is expected to achieve complete structural analysis and evaluation of the modified region under non-destructive conditions, thereby further improving the reliability and mass production capability of TGV and SiC laser processing technologies.

[0012] As described above, one aspect of the present invention is to provide a tomographic scanning method for a laser-modified region, comprising the following steps: (a) placing a light source on a solid material having a laser-modified region, allowing the light source to generate a fundamental frequency light to scan the solid material, causing the solid material to reflect, refract, and scatter the fundamental frequency light, and causing the laser-modified region to generate nonlinear light through a nonlinear effect, wherein the wavelength of the fundamental frequency light is 1000-2200 nm and can penetrate the solid material. (b) placing an objective lens between the light source and the solid material. (c) placing a filter to retain the nonlinear light and filter out the fundamental frequency light. (d) placing a photodetector after the filter to receive a plurality of signals from the nonlinear light generated by the laser-modified region. (e) Adjust the distance between the objective lens and the solid material so that the focal plane of the fundamental light after passing through the objective lens falls on the solid material and covers the laser-modified region, allowing the nonlinear light to pass through the filter before reaching the photodetector to detect the signals of the nonlinear light. (f) Repeat step (e) and gradually change the distance between the objective lens and the solid material so that the focal plane of the fundamental light after passing through the objective lens gradually moves along the thickness direction of the solid material. Perform a tomographic scan on the laser-modified region and collect the signals of the nonlinear light generated at multiple resting positions of the laser-modified region on the focal plane to construct the three-dimensional geometry of the laser-modified 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 visible light at three times the frequency of the nonlinear light.

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

[0017] According to one embodiment of the present invention, the laser-modified region is formed in the solid material in order to prepare for forming a perforation in the solid material.

[0018] Another aspect of the present invention provides a tomographic scanning system for a laser-modified region, comprising a light source, an objective lens, a filter, a photodetector, and a computing device. The light source is disposed on a solid material having a laser-modified region, generating a 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 through a nonlinear effect. The fundamental frequency light has a wavelength of 1000-2200 nm and can penetrate the solid material. The objective lens is disposed between the light source and the solid material. The filter is used to retain the nonlinear light and filter out the fundamental frequency light. The photodetector is disposed after the filter and is used to detect a plurality of signals from the nonlinear light generated by the laser-modified region. The computing device is signal-connected to the photodetector to receive and process these signals. By gradually changing the distance between the objective lens and the solid material, the focal plane of the fundamental frequency light after passing through the objective lens is gradually moved along the thickness direction of the solid material to perform tomographic scanning. The light detector is used to collect the signals of the nonlinear light generated by the laser-modified region at multiple resting positions on the focal plane, and the computing device is used to construct a three-dimensional geometry 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 system of the laser modified region further includes a galvanometer scanning system, which allows the fundamental frequency light emitted by the light source to be reflected by the galvanometer scanning system before irradiating the solid material, thereby changing the scanning position of the fundamental frequency light on 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 at three times the frequency of the nonlinear light.

[0024] According to one embodiment of the present invention, the laser-modified region is formed in the solid material in order to prepare for forming a perforation in the solid material.

[0025] Based on the above, a tomographic scanning system and method for laser-modified regions are provided. This tomographic scanning system and method for laser-modified regions can perform real-time and non-destructive three-dimensional scanning, rapidly providing structural analysis results of the laser-modified regions for real-time quality monitoring.

[0026] The foregoing summary is intended to provide a simplified overview of the invention, enabling the reader to gain a basic understanding. This summary is not a complete overview of the invention, nor is it intended to identify key components of the embodiments or define the scope of the invention. Upon reviewing the following embodiments, those skilled in the art will readily understand the basic spirit and other objectives of the invention, as well as the technical means and implementation aspects employed. Attached Figure Description

[0027] To make the above and other objects, features, advantages and embodiments of the present invention more apparent and understandable, the accompanying drawings are described below.

[0028] Figure 1A This is a schematic diagram of the architecture of a laser-modified zone tomography system according to an embodiment of the present invention.

[0029] Figure 1B This is a schematic diagram of the architecture of a laser-modified zone tomography system according to another embodiment of the present invention.

[0030] Figure 2 This is a side view and cross-sectional image of a laser-modified region before glass perforation according to an embodiment of the present invention, and a schematic diagram of the detection results of the laser-modified region.

[0031] Figure 3 This is an example of the detection results of a normal laser-modified zone in a glass perforation precursor according to another embodiment of the present invention.

[0032] Figure 4 This is an example of the detection results of an abnormal laser-modified region in a glass perforation precursor according to another embodiment of the present invention.

[0033] Figure 5 This is a schematic diagram of the laser-modified region and microcracks of a silicon carbide ingot.

[0034] Figure 6A The images are side and cross-sectional views of the laser-modified region and microcracks of a silicon carbide ingot according to an embodiment of the present invention.

[0035] Figure 6B This is a side view and cross-sectional image of a microcracked surface of a silicon carbide ingot according to an embodiment of the present invention.

[0036] Symbol Explanation

[0037] 100: Tomography System

[0038] 110: Light source

[0039] 120: Galvanometer Scanning System

[0040] 130: Dichroic mirror

[0041] 140: Objective lens

[0042] 150a, 150b: Filters

[0043] 160a, 160b: Light detector

[0044] 170: Computing device

[0045] 180, 180a, 180b: Fundamental frequency light

[0046] 190a, 190b: Nonlinear light

[0047] 200: Solid materials

[0048] 210, 280-290: Third harmonic optical images

[0049] 220: Glass substrate

[0050] 230-270: Laser Modification Zone

[0051] 300-330: Third harmonic optical imaging

[0052] 400-450: Third harmonic optical imaging

[0053] 500: Silicon carbide ingot

[0054] 510: Laser Modification Zone

[0055] 520: Microcracks

[0056] 530, 540: Areas

[0057] 600: Silicon carbide ingot

[0058] 610: Laser Modification Zone

[0059] 620: Microcracks

[0060] 630-650, 670-680: Third harmonic optical images

[0061] 660: White Light Optical Imaging Detailed Implementation

[0062] Based on the above, a tomographic scanning system and method for laser-modified regions of solid materials are provided. This tomographic scanning system and method for laser-modified regions can perform non-destructive real-time stereoscopic scanning of solid materials, quickly providing structural analysis results of the laser-modified regions. The following description will introduce an example structure of the tomographic scanning system for laser-modified regions and an example method for tomographic scanning of solid materials with laser-modified regions.

[0063] To facilitate understanding of the embodiments of the present invention, explanations of some technical details will be provided, accompanied by corresponding drawings. However, not all embodiments require these technical details. For some well-known structures or components, the drawings are presented schematically only to simplify the content. Terms such as "connected" or "set" indicate that a component may be directly located on another component, or that an intermediate component may connect the two. Conversely, terms such as "first," "second," and "third" are used only to distinguish components or parts and do not indicate a sequential order. Relative orientation terms such as "below" and...

[0064] "Above" describes the relationship between components and includes device orientations other than those shown in the diagram.

[0065] To provide a more comprehensive description of the embodiments of the present invention, illustrative descriptions are provided below for different aspects and specific implementations. This is not limited to a single form of implementation or application, but includes the features and method steps of multiple specific embodiments. Different embodiments can achieve the same or equivalent functions and steps, demonstrating the flexibility of the present invention.

[0066] For ease of description, the functions of the apparatus are described by dividing them into various functional units and / or functional modules. In implementing this invention, these functional units or modules can be implemented in the same or multiple software and / or hardware components. This invention is described using flowcharts and / or block diagrams of methods, apparatus, and computer program products according to embodiments. Computer program instructions are input into a processor, and by executing the instructions, means for implementing the functions are generated. These instructions can be executed in the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device.

[0067] Laser-modified zone tomographic scanning system

[0068] Figure 1A This is a schematic diagram of the architecture of a tomographic scanning system for a laser-modified region according to an embodiment of the present invention. The tomographic scanning system 100 for the laser-modified region is mainly used for precise non-destructive testing of laser-modified solid materials to establish their three-dimensional geometry, thereby improving process monitoring capabilities and the accuracy and reliability of subsequent etching steps. In Figure 1, the tomographic scanning system 100 for the laser-modified region includes 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 cooperation between these components ensures efficient optical signal screening and high-resolution scanning of the laser-modified region.

[0069] The light source 110 is disposed on a solid material 200 having a laser-modified region (not shown in Figure 1). Figure 1AThe substrate (displayed as a substrate) is responsible for generating fundamental frequency light 180 and irradiating the solid material 200 with this fundamental frequency light 180, causing reflection, refraction, and scattering phenomena within the solid material 200. Furthermore, when the fundamental frequency light 180 irradiates the laser-modified region, due to the nonlinear optical characteristics of the laser-modified region, it will generate nonlinear light 180a, further improving the detection sensitivity.

[0070] According to one embodiment of the present invention, the light source 110 can be an ultrashort pulse laser light source, such as a femtosecond or picosecond level laser light source, and its pulse width can be set in the range of 10. -15 Up to 10 -12 The light source 110 generates a fundamental frequency light 180 that is near-infrared (NIR) with a wavelength range of 1000-2200 nm, such as 1050 nm or 1560 nm. This wavelength range of laser light can effectively penetrate solid materials such as glass or silicon carbide, and also produce significant nonlinear optical phenomena, such as third-harmonic generation (THG), further enhancing the optical contrast between the laser-modified region and its surrounding unmodified region, thus facilitating the detection of the laser-modified region.

[0071] According to one embodiment of the present invention, the solid material 200 may be, for example, a solid material, a silicon carbide solid material, or other insulating solid materials. The glass solid material may be, for example, a glass substrate, while the silicon carbide solid material may be, 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 can be 5-3,000 μm to meet different packaging technology requirements. Furthermore, after laser modification, the physical and optical properties of the glass substrate undergo significant changes, such as changes in refractive index, decrease in density, and redistribution of internal stress. These changes will affect its subsequent etching behavior. Therefore, the tomographic scanning system 100 of the laser-modified region of the present invention can effectively monitor these parameters, improving process accuracy.

[0072] The galvanometer scanning system 120 can be positioned in the forward direction of the light emitted from the light source 110, serving as the core component for optical scanning control. Its main function is to adjust and guide the fundamental frequency light 180 from the light source 110, enabling it to dynamically change its incident position on the solid material 200 during the scanning process, thereby improving the overall flexibility and resolution of optical detection. When the fundamental frequency light 180 passes through the galvanometer scanning system 120, the system performs high-speed angle adjustment of the beam to ensure that the laser light can uniformly scan the surface of the solid material 200 and ensure complete scanning of the laser-modified regions in different areas of the solid material 200.

[0073] The galvanometer scanning system 120 operates primarily by using a high-speed oscillating galvanometer mirror to deflect the light beam at a high-precision angle, thereby altering the scanning position of the fundamental frequency light 180 on the solid-state material 200. This technology provides extremely high scanning speeds and very low latency, enabling the detection 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 repeatability, and scanning rate can be further improved to adapt to different types of solid-state materials and laser modification conditions.

[0074] Objective lens 140 can be positioned between galvanometer scanning system 120 and solid material 200, serving as a core component for optical signal collection and focusing. Its main function is to ensure that the fundamental frequency light 180a reflected from galvanometer scanning system 120 can be accurately focused onto solid material 200, while simultaneously enhancing the collection efficiency of nonlinear optical signal 190a from solid material 200, thereby improving overall detection performance.

[0075] According to one embodiment of the present invention, the objective lens 140 may have a high numerical aperture (NA), a design that helps to improve the generation efficiency of nonlinear optical signals. The high numerical aperture objective lens 140 can provide stronger light field focusing capability, enabling the fundamental frequency light 180a to generate stronger nonlinear effects within the solid material 200, such as third-harmonic generation (THG), thereby improving the optical signal contrast between the laser-modified and unmodified regions, making detection more sensitive.

[0076] According to another embodiment of the present invention, the high numerical aperture objective lens 140 can not only improve the generation efficiency of nonlinear light, but also optimize the collection performance of nonlinear light. This means that the objective lens 140 can also enhance the signal intensity collected by the photodetector 160a, improve the signal-to-noise ratio (SNR), and ensure high accuracy and stability of the optical signal. A high SNR can reduce the interference of background noise on the detection results, making the structure of the laser-modified region more clearly visible, and further improving the identification capability of the laser-modified region tomography system 100.

[0077] Furthermore, the choice of objective lens 140 also affects the system's resolution and depth of focus (DOF). Appropriate adjustment of the NA value ensures that the fundamental frequency light 180 can be accurately focused to different depths within the solid material 200, thereby ensuring the acquisition of accurate stereoscopic structural information during tomography.

[0078] By optimizing the optical characteristics of the objective lens 140, the tomographic scanning system 100 for the laser-modified region can effectively improve the imaging quality of the laser-modified region and ensure that the subsequent photodetector 160a can acquire high-resolution optical signals to facilitate the establishment of an accurate three-dimensional structural model.

[0079] Filter 150a is positioned below the solid-state material 200. Its main function is to selectively retain the nonlinear light 190a from the solid-state material 200 and effectively filter out the fundamental frequency light 180a, ensuring that the subsequent detection system only receives the nonlinear light signal from the laser-modified region. Because the optical properties of the laser-modified region change after being treated with femtosecond or picosecond lasers, such as the generation of refractive index gradients and changes in stress distribution within the laser-modified region, nonlinear optical phenomena occur in this region. Therefore, the design of filter 150a is crucial to ensuring the purity and accuracy of the detection signal.

[0080] According to one embodiment of the present invention, filter 150a selectively transmits nonlinear light 190a from solid material 200, particularly retaining the third-harmonic generation (THG) nonlinear optical signal of the fundamental frequency light 180a. Since the wavelength of the third-harmonic optical signal is one-third of the wavelength of the fundamental frequency light, for example, when the wavelength of the fundamental frequency light 180a is 1560 nm, the generated third-harmonic light is 520 nm in the visible light range. Filter 150a can precisely filter light within this wavelength range, ensuring that the photodetector 160a only receives valuable nonlinear light signals, thereby improving the sensitivity and accuracy of optical measurements.

[0081] By using a highly selective filter 150a, the background fundamental frequency light 180a from the solid material 200 can be effectively removed, reducing noise interference and improving the resolution of the laser-modified region by the tomographic scanning system 100. This design enables the photodetector 160a to obtain a clear, high-contrast image of the laser-modified region, which helps to accurately construct a three-dimensional structural model of the laser-modified region.

[0082] A photodetector 160a is positioned below the filter 150a. Its main function is to detect and record the nonlinear light 190a passing through the filter 150a and convert the collected optical signal into an analyzable electrical signal. Since the intensity of the nonlinear light 190a is typically lower than that of the fundamental frequency light 180a, the sensitivity of the photodetector 160a directly affects the system's detection accuracy and signal quality. Therefore, a high-sensitivity photodetector is selected to ensure that even weak nonlinear light signals can be effectively captured and converted into stable electronic data.

[0083] According to one embodiment of the present invention, the photodetector 160a can use a variety of high-performance photoelectric sensing components, such as photodiodes (PDs), avalanche photodiodes (APDs), charge-coupled devices (CCDs), photomultiplier tubes (PMTs), or any combination thereof. Photodiodes are suitable for general optical detection applications, possessing high sensitivity and low noise characteristics. Avalanche photodiodes provide higher photoelectric conversion efficiency than general PDs through an internal gain mechanism, thus making them suitable for low-intensity light signal detection. Charge-coupled devices can be used for high-resolution image capture, suitable for applications requiring optical tomography. Photomultiplier tubes possess extremely high photon gain capabilities, enabling the detection of extremely low-intensity light signals, and are particularly suitable for the detection of high-precision nonlinear optical signals.

[0084] The computing device 170 is signal-connected to the photodetector 160a and is responsible for receiving, processing, and analyzing the signal from the nonlinear light 190a from the photodetector 160a. Since the laser-modified region tomography system 100 needs to perform high-resolution imaging of the modified region inside the solid material 200, the computing device 170 needs to have powerful data processing capabilities to ensure accurate reconstruction of the three-dimensional geometry of the laser-modified region.

[0085] For example, to provide more accurate structural analysis of the modified region, the tomographic scanning system 100 for the laser modified region employs layered focal plane scanning technology. This technology reconstructs a three-dimensional image of the laser modified region by collecting nonlinear light signals from different focal layers. During this process, the computing device 170 performs image stacking to improve image resolution and enhance boundary contrast. This technique ensures that the fine structure of the laser modified region is accurately represented and enables the identification of refractive index changes, stress distribution, and structural integrity within the region. Furthermore, through image comparison algorithms, the computing device 170 can also compare the image with the original design shape of the laser modified region to assess whether the laser modification effect meets the expected specifications.

[0086] Figure 1B This is a schematic diagram of another architecture of a tomographic scanning system for a laser-modified region according to another embodiment of the present invention. Figure 1A Compared to the architecture shown, this embodiment mainly adds a dichroic mirror 130 and changes the layout of the filter 150b and photodetector 160b to provide an alternative optical signal collection method. In this design, the tomographic scanning system 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. The cooperation between these components ensures efficient optical signal filtering and high-resolution scanning of the laser-modified region.

[0087] Figure 1B and Figure 1A The main difference is that a dichroic mirror 130 is added between the galvanometer scanning system 120 and the objective lens 140 in this embodiment. In addition, the layout of the filter 150b and the photodetector 160b has also been adjusted, and they are now positioned above the solid material 200.

[0088] exist Figure 1B In this architecture, when the fundamental frequency light 180 is emitted by the light source 110 and adjusted by the galvanometer scanning system 120, the beam first passes through the dichroic mirror 130 and is then 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 is generated, producing nonlinear light 190b. The optical signal generated inside the solid material 200 (including the fundamental frequency light 180b and the nonlinear light 190b) is reflected by the dichroic mirror 130 in the optical path as it propagates outward, and then guided to the filter 150b above. The filter 150b filters out the fundamental frequency light 180b, retaining only the nonlinear light 190b, so that the photodetector 160b subsequently placed thereafter can only receive the nonlinear light signal.

[0089] Figure 1B The rest of the part is due to and Figure 1A The same applies, so I will not elaborate further.

[0090] Tomographic scanning method for laser-modified regions

[0091] To obtain a high-resolution three-dimensional shape of the laser-modified region, the tomographic scanning system 100 for the laser-modified region employs a layer-by-layer scanning technique, performing complete three-dimensional image reconstruction by adjusting the focal plane position. The scanning process is as follows:

[0092] First, the solid material 200 is positioned below the objective lens 140 to ensure the alignment and stability of the optical system. Next, the fundamental frequency light 180a generated by the light source 110 is reflected by the galvanometer scanning system 120 and then passes through the objective lens 140, causing the focal plane of this fundamental frequency light to fall on the upper surface of the solid material 200. At this point, the system begins to scan the laser-modified region layer by layer to obtain complete structural information of the region.

[0093] 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 passing through the objective lens 140 gradually moves downward along the thickness direction of the solid material 200 until it reaches the lower surface of the solid material 200. As the focal plane moves, different depth layers inside the laser-modified region are sequentially excited by the fundamental frequency light 180, thereby generating corresponding nonlinear light 190a or 190b.

[0094] At each focal plane location, the nonlinear optical signal 190a or 190b from the laser-modified region is received by photodetectors 160a or 160b, respectively. Depending on the scanning architecture, when the laser-modified region tomography system 100 employs... Figure 1A When configured, the photodetector 160a collects the nonlinear light 190a after passing through the filter 150a; when the system adopts Figure 1B In this configuration, the nonlinear light 190b is reflected by the dichroic mirror 130 and then passes through the filter 150b before being detected by the photodetector 160b.

[0095] All collected optical signals are transmitted to the computing device 170 for signal processing, image reconstruction, and 3D geometry analysis. Through layered focal plane scanning, the computing device 170 stacks the nonlinear optical signals acquired at different focal plane positions into 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.

[0096] Through the above scanning method, the tomographic scanning system 100 of the present invention can provide high-resolution, non-destructive laser-modified zone detection technology, which can accurately grasp the internal structural changes of the laser-modified zone, and further improve the reliability and production efficiency of TGV process and silicon carbide machining.

[0097] Experimental Example 1: Detection of Laser-Modified Regions on Glass Substrates

[0098] Figure 2 This image shows a side view and cross-sectional view of the laser-modified region before glass perforation according to an embodiment of the present invention, and a schematic diagram of the detection results of the laser-modified region. Figure 2 In the third-harmonic optical image 210 on the side of the glass via, the laser-modified region 230 can be clearly observed. It is characterized by areas that emit light through the black glass substrate 220, indicating that the laser-modified region 230 has undergone laser modification. This image shows the morphological characteristics of the laser-modified region 230, which helps to determine its integrity and uniformity.

[0099] exist Figure 2 The upper right corner shows a side view of the glass substrate 220 with laser-modified regions 230. Furthermore, the images of laser-modified regions 240-270 show classifications of different modification results. Laser-modified region 240 shows a normal laser-modified region that has undergone complete and successful modification, with a uniform shape and no defects. Laser-modified regions 250-260 show abnormal laser-modified regions where some areas were not successfully modified, possibly due to uneven laser energy or internal substrate defects leading to incomplete modification. Laser-modified region 270 shows an abnormal phenomenon of uneven modification within the laser-modified region, which may affect the selectivity of subsequent etching steps and the quality of via formation.

[0100] In addition Figure 2 The image also shows third-harmonic optical images 280-290 of the cross-section of the glass via precursor. Third-harmonic optical image 290 shows a normal laser-modified region with a uniform cross-sectional shape and consistent optical characteristics. Third-harmonic optical image 280 shows an abnormal laser-modified region, which may contain fractures, hollow areas, or other irregular shapes, indicating that the modification process may be affected by internal substrate stress, laser focus drift, or other variables.

[0101] Figure 3 This is an example of the detection results of a normal laser-modified region in a glass perforation precursor according to another embodiment of the present invention. Figure 3 The image shows a side-view third-harmonic optical image 300 of the laser-modified region preceding the glass via, and further analyzes the uniformity and integrity of the laser-modified region through cross-sectional images at different depths. Figure 3In the images 310-330, third-harmonic optical images of the glass substrate at depths of -60μm, -300μm, and -540μm show that the cross-sectional shape and number of the laser-modified regions remain quite consistent at different depths, indicating that the modification process is stable and highly reproducible. These uniform laser-modified regions ensure consistent via formation in subsequent wet etching steps, further improving the reliability and yield of the TGV process.

[0102] Figure 4 This is an example of the detection results of an abnormal laser-modified region in a glass perforation precursor according to another embodiment of the present invention. Figure 4 The image shows a side-view third-harmonic optical image 400 of the laser-modified region preceding the glass via, and third-harmonic optical images 410-450 of cross-sections at different depths. Figure 4 In the analysis of the laser-modified regions preceding glass vias at different depths (0μm, -402μm, -524μm, -580μm, -700μm), it was found that some laser-modified regions were not fully presented in cross-sectional images at certain depths, showing an interruption phenomenon.

[0103] Specifically, at a depth of 0 μm, the third-harmonic optical image 440 shows the upper surface of the glass substrate; at a depth of -700 μm, the third-harmonic optical image 450 shows the lower surface of the glass substrate. In the third-harmonic optical images 410-430 at intermediate depths, some laser-modified areas are not continuously displayed, indicating that the laser modification did not penetrate the entire glass substrate. This may be due to laser focus drift, internal material stress, or laser energy attenuation, leading to uneven laser-modified areas. These anomalies may affect the uniformity of subsequent wet etching steps, resulting in incomplete via shapes, and consequently affecting the electrical properties and structural strength of the TGV.

[0104] As described above, frequency-triple harmonic optical imaging technology can be used to detect the integrity of the laser-modified region in real time before etching, allowing for early detection and correction of process problems, thereby improving the yield and reliability of glass vias. Experimental Example 2: Detection of the laser-modified region in a silicon carbide ingot.

[0105] Due to the difficulty in growing silicon carbide (SiC) crystals, its ingot diameter is typically about 4-8 inches (10-20 cm) and its thickness is about 10-25 mm. In practical applications, the silicon carbide ingots need to be further cut into wafers with a thickness of 150-350 μm. Because silicon carbide is extremely hard, traditional cutting methods are difficult. Therefore, the industry has introduced "laser modification technology" to improve cutting efficiency and quality, and reduce material waste.

[0106] Figure 5This diagram illustrates the laser-modified region and microcracks of a silicon carbide ingot. The upper view is a top view of the silicon carbide ingot, and the lower view is a side view. When using an ultrafast laser (femtosecond laser) for modification, the laser is first focused on the laser-modified region 510 inside the silicon carbide ingot 500. After significant energy absorption, the silicon carbide dissociates into amorphous silicon and amorphous carbon, forming an initial modified layer. Subsequently, the continuously irradiated laser light is absorbed by the previously generated amorphous carbon, causing micro-explosions due to volume expansion and generating internal stress within the ingot 500, forming a microcracked modified layer in the laser-modified region 510. Next, ultrasonic vibration is applied to the silicon carbide ingot 500, allowing the vibrational energy to be transferred to the laser-modified region 510, guiding the microcracks to grow further and connecting previously discontinuous cracks, ultimately forming a nearly continuous microcrack surface 520 within the ingot 500. At this point, by simply applying tensile force with a vacuum chuck, the ingot can be easily separated into wafers along the modified layer, effectively avoiding damage caused by hard separation.

[0107] Figure 6A This is a side view and cross-sectional image of a silicon carbide ingot according to an embodiment of the present invention, the image being mapped to... Figure 5 Area 530. In Figure 6A In the process, the laser modification depth of silicon carbide ingot 600 is 180 μm. Located in... Figure 6A The white light optical image 660 below is an image obtained at a focusing depth of 50 μm below the surface of the ingot 600 under a general optical microscope and white light illumination. Since this method cannot distinguish between laser-modified regions 610 and microcracks 620 at different depths, observation using third-harmonic light is required to obtain more accurate information.

[0108] Figure 6A The upper right image shows a third-harmonic optical image 630 of the silicon carbide ingot 600 viewed from the side. The upper left images show third-harmonic optical images 640 and 650, respectively, showing cross-sectional views at a depth of 170 μm below the surface. In the third-harmonic optical image 650, the intensity of the third-harmonic light generated on both sides of the laser-modified region 610 is different, confirming that there is a depth difference in the microcracks 620 on both sides of the laser-modified region 610, similar to... Figure 5 The microcrack 520 is shown in the lower side view.

[0109] Figure 6B This is a side view and cross-sectional image of a silicon carbide ingot according to an embodiment of the present invention, and Figure 6A The image shown can be corresponded to Figure 5 The area shown is 540. Figure 6BThe image on the right is a third-harmonic optical image 670 of the silicon carbide ingot 600 viewed from the side. The images on the left are a third-harmonic optical image 680, a top-view image at a depth equal to the surface, and a third-harmonic optical image 690, a cross-sectional image at a depth of 180 μm below the surface. By comparing third-harmonic optical images at different depths, the formation and extension of microcracks in the laser-modified region and its surrounding areas can be observed more clearly.

[0110] Advanced optical detection techniques such as tomography can clearly identify the micro-explosion zones and micro-crack development caused by laser modification within silicon carbide ingots, and further determine the depth and structural characteristics of the modified zones. These observations not only help optimize laser processing parameters and improve cutting efficiency and quality, but also provide more accurate evaluation and technical support for subsequent applications of laser modification in glass substrates and silicon carbide materials.

[0111] This invention provides a tomographic scanning system and method for laser-modified regions. Addressing the limitations of traditional detection methods, this technology proposes a high-resolution, non-destructive, real-time three-dimensional scanning technique capable of accurately observing and evaluating the quality of laser-modified regions within solid materials (including glass substrates and silicon carbide ingots). This tomographic scanning system for laser-modified regions can be applied not only to the detection of laser-modified regions preceding glass vias in glass substrates, but also further extended to observing micro-explosion zones and micro-cracks formed in laser-modified regions of silicon carbide materials, comprehensively improving the reliability and yield of the overall process.

[0112] The aforementioned tomographic scanning system employs fundamental frequency light excitation and nonlinear optical effects to establish a three-dimensional structural model of the laser-modified region through layer-by-layer scanning technology. This provides complete and detailed internal modification information without causing any damage to the glass substrate or silicon carbide ingot, ensuring sample integrity. Through high numerical aperture objectives and ultrashort pulse lasers, the scanning system achieves sub-micron resolution (<0.5 μm), enabling precise detection of the three-dimensional structure of the laser-modified region and the distribution of defects generated by micro-explosions in the silicon carbide material.

[0113] When applied to glass through-hole processes, this system allows for real-time monitoring of the laser-modified region after the laser modification step and before the wet etching step, preventing abnormal modification from affecting the quality of subsequent etching steps. Compared to traditional automated optical inspection (AOI), which can only observe the substrate surface, this scanning system can deeply inspect the laser-modified region inside the material, quickly identifying whether the laser modification is complete and detecting abnormal areas that may affect the etching step or machining, such as incomplete modification, uneven modification areas, or cracks. For the laser-modified region of silicon carbide ingots, this system can also detect the direction and depth of microcracks caused by micro-explosions, helping to optimize cutting parameters and reduce material loss.

[0114] The tomographic scanning system of this invention is particularly suitable for through-hole processes with high aspect ratios, especially glass through-holes with aspect ratios exceeding 1:80. Through image stacking technology, it ensures that the shape and number of laser-modified regions remain consistent at different depths, improving the stability of subsequent wet etching steps and resulting in higher through-hole uniformity. Simultaneously, this system can also perform three-dimensional scanning of silicon carbide laser-modified regions in ingots of greater thickness or different shapes, ensuring the continuity and integrity of the modified regions, further improving the efficiency and yield of silicon carbide material processing.

[0115] In summary, this invention provides a high-resolution, real-time, non-destructive laser-modified region detection technology that effectively solves the detection bottlenecks in the TGV process of glass substrates and the machining of silicon carbide ingots. Through nonlinear optical effects and optical signal screening technology, the tomographic scanning system proposed in this invention can accurately scan the laser-modified regions inside solid materials and perform real-time quality monitoring. Whether it's the modified region preceding a glass through-hole or the modified region and microcracks formed by micro-explosions in silicon carbide ingots, both can be completely reconstructed and measured, thereby ensuring process stability and the reliability of the final product.

[0116] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A tomographic scanning method for a laser-modified region, comprising the following steps: (a) A light source is placed on a solid material having a laser-modified region, and the light source generates a fundamental frequency light to scan the solid material, so that the solid material reflects, refracts and scatters the fundamental frequency light, and the laser-modified region generates nonlinear light through a nonlinear effect, wherein the wavelength of the fundamental frequency light is 1000-2200nm and can penetrate the solid material. (b) A lens is positioned between the light source and the solid material; (c) A filter is provided to retain the nonlinear light and filter out the fundamental frequency light; (d) A photodetector is placed after the filter to receive multiple signals from the nonlinear light generated by the laser-modified region; (e) Adjust the distance between the objective lens and the solid material so that the focal plane of the fundamental frequency light after passing through the objective lens falls on the solid material and covers the laser-modified region, so that the nonlinear light can pass through the filter first and then reach the photodetector to detect these signals of the nonlinear light; (f) Repeat step (e) and gradually change the distance between the objective lens and the solid material, so that the focal plane of the fundamental frequency light after passing through the objective lens gradually moves along the thickness direction of the solid material, perform tomographic scanning on the laser-modified region, and collect the signals of the nonlinear light generated by the laser-modified region at a plurality of dwell positions on the focal plane, so as to construct the three-dimensional geometry of the laser-modified region.

2. The tomographic scanning method for the laser-modified region as described in claim 1, wherein the light source is an ultrashort pulse laser light source.

3. The tomographic scanning method for the laser-modified region as described in claim 1, wherein the solid material is a glass solid material or a silicon carbide solid material.

4. The tomographic scanning method for the laser-modified region as described in claim 3, wherein the filter retains visible light at three times the frequency of the nonlinear light.

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

6. The tomographic scanning method for a laser-modified region as described in any one of claims 1-5, wherein the laser-modified region is formed in the solid material in preparation for forming a perforation in the solid material or for preparing to cut the solid material.

7. A tomographic scanning system for laser-modified regions, comprising: A light source is disposed on a solid material having a laser-modified region, and generates a fundamental frequency light to scan the solid material, causing the solid material to reflect, refract, and scatter the fundamental frequency light, and causing the laser-modified region to generate nonlinear light through a nonlinear effect, wherein the wavelength of the fundamental frequency light is 1000-2200nm and can penetrate the solid material. An objective lens is disposed between the light source and the solid material; A filter that retains the nonlinear light and filters out the fundamental frequency light; A photodetector, disposed after the filter, is used to detect a plurality of signals from the nonlinear light generated by the laser-modified region; and A computing device, signal-connected to the photodetector, to receive and process these signals; The distance between the objective lens and the solid material is gradually changed, causing the focal plane of the fundamental frequency light after passing through the objective lens to gradually move along the thickness direction of the solid material to perform tomographic scanning. The photodetector is used to collect the signals of the nonlinear light generated by the laser-modified region at a plurality of resting positions on the focal plane, and the computing device is used to construct a three-dimensional geometry of the laser-modified region.

8. The tomographic scanning system for the laser-modified region as described in claim 7, wherein the light source is an ultrashort pulse laser light source.

9. The tomographic scanning system for the laser-modified region as described in claim 7, wherein the photodetector is a photodiode, an avalanche photodiode, a charge-coupled device, a photomultiplier tube, or any combination thereof.

10. The tomographic scanning system for the laser-modified region as described in claim 7 further includes a galvanometer scanning system disposed in front of the light source, such that the fundamental frequency light emitted by the light source is first reflected by the galvanometer scanning system and then irradiates the solid material, thereby changing the scanning position of the fundamental frequency light falling on the solid material.

11. The tomographic scanning system for the laser-modified region as described in claim 7, wherein the solid material is a glass solid material or a silicon carbide solid material.

12. The tomographic scanning system for the laser-modified region as claimed in claim 11, wherein the filter retains visible light at three times the frequency of the nonlinear light.

13. The tomographic scanning system for a laser-modified region as claimed in any one of claims 7-12, wherein the laser-modified region is formed in the solid material in preparation for forming a perforation in the solid material or for preparing to cut the solid material.

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