Optical inspection system and method for semiconductor substrates

Abstract

The present invention relates to an optical inspection system and method for semiconductor substrates. [Solution] The optical inspection system and method for semiconductor substrates involves placing a sample at the inspection position and introducing an excitation light source into the sample for measurement. The excitation signal generated after the light source enters the sample in the forward direction is called the forward excitation signal, and the excitation signal generated after the light source enters the sample and is reflected by another interface of the sample is called the reverse excitation signal. The system collects the forward and reverse excitation signals and, through a signal processing and image generation module, generates high-resolution images of the via wall shape and defects of microvias, enabling accurate inspection of the internal structure of microvias.

Description

Technical Field

[0001] The technical field of the present invention relates to the optical inspection of semiconductor substrates.

Background Art

[0002] In conventional optical experiments or imaging, usually, after the excitation light is focused by an optical lens, it is irradiated onto the front surface (the surface facing the light) of the sample, enters slightly into the sample, and thereby causes corresponding optical reactions (such as scattering or reflection) on the sample surface or inside the surface layer. This type of excitation method mainly has the limitation that the excitation light is always irradiated onto the front surface of the sample and cannot irradiate the back surface or internal structure of the sample. However, the internal structure of some samples cannot be revealed by the front excitation light. In addition, since the excitation light can only irradiate the front surface of the sample, the structure or optical characteristics of the back surface of the sample cannot be effectively excited or measured. Thus, in situations where it is necessary to obtain data from different angles or depths, the measurement and inspection range are significantly limited. Therefore, the conventional excitation light irradiation method cannot provide comprehensive data, and there are certain deficiencies especially in the analysis of deep structures or the measurement and inspection of specific situations (such as high aspect ratio microvias).

Summary of the Invention

Problems to be Solved by the Invention

[0003] Based on the above problems, the present invention presents a solution. This solution is mainly used in the present invention to inspect high aspect ratio microvias, but when actually used, it can also be extended to the inspection of the inside or back surface of wafers or semiconductor substrates.

Means for Solving the Problems

[0004] The technical features of the present invention are as follows. The optical inspection system and method for semiconductor substrates involves placing a sample at the inspection position and introducing an excitation light source into the sample for measurement. The excitation signal generated after the light source enters the sample in the forward direction is called the forward excitation signal, and the excitation signal generated after the light source enters the sample and is reflected by another interface of the sample is called the reverse excitation signal. The system collects the forward and reverse excitation signals and, through signal processing and image generation modules, generates high-resolution images of the via wall shape and defects of microvias, enabling accurate inspection of the internal structure of microvias.

[0005] The optical inspection system and method for semiconductor substrates involves placing a sample at the inspection position, and excitation light provided from a light source module entering a designated area from the front of the sample to generate a forward excitation signal. Simultaneously, an interface on the back surface of the sample reflects this excitation light, becoming reverse excitation light, which then re-enters the interior of the designated area of ​​the sample from the back surface to generate a reverse excitation signal. The system collects the forward and reverse excitation signals, and further processes them through a signal processing and image generation module to generate highly discriminative images of the shape and defects of the designated area of ​​the sample, enabling accurate inspection of the internal structure of the designated area. [Effects of the Invention]

[0006] The effects of the present invention are as follows: For excitation in the reverse direction, some of the excitation light passes through the sample, then returns in the reverse direction from the back of the sample and re-enters the sample.

[0007] The system records forward and reverse excitation signals, thereby achieving bidirectional signal acquisition. By obtaining forward and reverse information about the sample, more complete sample characterization is provided. By analyzing the bidirectional signals, physical properties of the sample, such as thickness, depth, or other relevant information, can be inferred.

[0008] It accurately depicts the structure of microvias, clearly showing the via wall shape, size, and defects of microvias, providing highly accurate inspection results.

[0009] By combining signals excited by forward and reverse light, we can gain a more comprehensive understanding of the internal structure of microvias.

[0010] Optical inspection does not physically damage the sample and is applicable in situations where there is a high requirement for sample integrity.

[0011] The same sample can be tested multiple times, making comparative analysis convenient.

[0012] This technology allows for the accurate localization and identification of various defects in microvias, such as roughness of the via wall and non-uniform via diameter. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram 1 of the sample configuration in the present invention. [Figure 2] Figure 2 shows a schematic representation of the sample configuration in this invention. [Figure 3] This is a block diagram of a first embodiment of the inspection system of the present invention. [Figure 4] This is a schematic diagram of a first embodiment of the inspection method of the present invention. [Figure 5] This is a block diagram of a second embodiment of the inspection system of the present invention. [Figure 6] This is a schematic diagram of a second embodiment of the inspection method of the present invention. [Figure 7] This is a schematic diagram of a third embodiment of the inspection method of the present invention. [Figure 8] This is a schematic diagram of a fourth embodiment of the inspection method of the present invention. [Figure 9] This is a two-dimensional image 1 of the microvia of the present invention. [Figure 10] This is a two-dimensional image 2 of the microvia of the present invention. [Figure 11] This is a three-dimensional image of the microvia of the present invention. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments for carrying out the present invention will be described with reference to the figures and examples. It should be noted that the figures provided in the following examples only provide a general overview of the basic concept of the present invention, and only show the components relevant to the present invention, and do not illustrate the number, shape, and size of elements when actually implemented.

[0015] As shown in Figure 1, in the case of Embodiment 1 of Sample 10 of the present invention, Sample 10 is a semiconductor 3D package structure and includes microvias 13 characterized by a high aspect ratio, including, but not limited to, through-silicon vias (TSVs) and through-glass vias (TGVs). Element reference numerals 21 and 22 represent non-metallic layers, which are usually insulating layers, photoresist layers, or other functional layers, and may be single-layer or multilayer structures. Element reference numeral 23 represents an electrode layer, which is usually a metal layer 23. Element reference numeral 24 represents a silicon-based layer. In the present invention, Sample 10 can use the electrode layer / metal layer 23 as an interface 31. In addition, different insulating boundary portions can also be used as interfaces 31 that reverse the direction of excitation light, or the interface may include structural layers fixed on the back surface of the sample or inside the sample that can reflect light rays.

[0016] As shown in FIG. 2, regarding Form 2 of the sample 10 of the present invention, the sample 10 is a semiconductor 3D package structure. The sample 10 includes microvias 13 characterized by a high aspect ratio, including but not limited to through-silicon vias (TSVs) and through-glass vias (TGVs). Element reference numeral 21 and element reference numeral 22 represent non-metal layers, usually an insulating layer, a photoresist layer, or other functional layers, and may be a single-layer structure or a multi-layer structure. A reflection layer 25 is separately provided on the back surface 12 of the sample 10, which can be selected from a high-reflection mirror surface, a reflective material, or a thin film having special optical properties. The reflection layer 25 is attached to the surface of a stage 50 for loading the sample 10, and further, the reflection layer 25 contacts the back surface 12 of the sample 10. The reflection layer 25 is used as an interface 31 in the present invention.

[0017] As shown in FIG. 3, regarding the inspection system, the first embodiment of the present invention includes a sample 10, a light source module 30, an interface 31, a photodetector 33, and a signal processing and image generation module 34.

[0018] The sample 10 is as shown in FIGS. 1 and 2 described above.

[0019] The light source module 30 provides excitation light 35, and the wavelength of the excitation light 35 is 1200 - 1800 nm. The excitation light is an ultra-fast laser. The excitation light 35 is focused and incident from the front surface 11 of the sample 10 into the interior of the microvia 13, generating a forward excitation signal. The focusing technique can employ one set or multiple sets of optical elements, including but not limited to lenses, mirrors, etc. The focusing position of the excitation light 35 can be precisely adjusted to ensure that the excitation light 35 is accurately incident into the microvia 13.

[0020] The interface 31 is provided on the back surface 12 of the sample 10, similar to the metal layer or reflective layer 25 of the sample 10 described above. The excitation light 35 incident on the microvia 13 is reflected to become reverse excitation light 36, which returns from the back surface 12 of the sample 10 to the interior of the microvia 13 and is used to generate a reverse excitation signal. Furthermore, the interface 31 can be designed to adjust its angle and change its reflectivity, thereby adjusting the reflection efficiency.

[0021] The photodetector 33 receives the forward excitation signal and the reverse excitation signal and converts the signals into electrical signals. The photodetector 33 is one or a combination selected from a photodiode (PD), an avalanche photodiode (APD), a charge-coupled device (CCD), and a photomultiplier tube (PMT). In the figures of the present invention, the light source module 30 and the photodetector 33 are a coaxial system.

[0022] The signal processing and image generation module 34 is coupled with the photodetector 33 and used to receive and process the electrical signal to generate an image 41 of the geometric structure of the microvia 13. Due to its high resolution, the geometric structure image 41 reveals the two-dimensional shape of the via wall of the microvia 13 and its defects. As shown in Figures 9 and 10, the cross-sectional shape 43 of the microvia 13 is shown, and the high-brightness areas 44 are defects where the via wall is non-uniform. The signal processing and image generation module 34 includes a digital signal processor, a high-performance computer, or dedicated firmware, and can process the electrical signal from the photodetector 33 in real time. Furthermore, it can use algorithms to generate high-resolution images of the geometric structure, and can also perform defect identification and quantitative analysis. The generated image of the microvia can reveal the via wall shape of the microvia, identify defects in the via wall (e.g., cracks, weak areas, material non-uniformity, etc.), and provide accurate geometric structure information, including features such as via diameter, depth, and shape.

[0023] As shown in Figure 4, the present invention realizes an inspection method based on the first embodiment described above. The system provides excitation light 35, focuses the excitation light 35, and directs it into the interior of a microvia 13 having a high aspect ratio characteristic from the front surface 11 of the sample 10, thereby generating a forward excitation signal. The interface 31 on the back surface 12 of the sample 10 is provided, and the excitation light 35 incident on the microvia 13 is reflected to become reverse excitation light 36, which returns from the back surface 12 of the sample 10 to the inside of the microvia 13, thereby generating a reverse excitation signal. The forward excitation signal and the reverse excitation signal are received, and these signals are converted into electrical signals. This includes generating an image of the two-dimensional via wall shape of the microvia 13 and any defects therein based on the electrical signal.

[0024] As shown in Figure 5, a second embodiment of the present invention relates to the inspection system. The system includes sample 10, a light source module 30, an interface 31, a vertical axis propulsion module 32, a photodetector 33, and a signal processing and image generation module 34.

[0025] Sample 10 is as shown in Figures 1 and 2 above.

[0026] The light source module 30 provides excitation light 35, the wavelength of which is 1200-1800 nm. The excitation light is an ultrafast laser. The excitation light 35 is focused and incident on the inside of the microvia 13 from the front 11 of the sample 10 to generate a forward excitation signal. The focusing technique can employ one or more sets of optical elements, including but not limited to lenses and mirrors. The focusing position of the excitation light 35 can be precisely adjusted to ensure that the excitation light 35 is accurately incident on the inside of the microvia 13.

[0027] The interface 31 is provided on the back surface of the sample 10, similar to the metal layer 23 or reflective layer 25 of the sample 10 described above. The excitation light 35 incident on the microvia 13 is reflected to become reverse excitation light 36, which returns from the back surface 12 of the sample 10 into the interior of the microvia 13 and is used to generate a reverse excitation signal. Furthermore, the interface 31 is designed to be angle-adjustable and reflectivity-changeable so that the reflection efficiency can be adjusted.

[0028] The vertical axis propulsion module 32 controls one or a combination of the light source module 30, the photodetector 33 and its associated optical articles (articles enclosed by dotted lines in Figure 5), and the sample 10 to propel along the vertical axis, and generates the forward and reverse excitation signals of the microvia 13 layer by layer along the propulsion direction. The vertical axis propulsion module 32 includes a moving mechanism, a guidance system, and a precision position control device, enabling the precise vertical movement described above. A layer-by-layer scan is performed to generate multilayer forward and reverse optical signals to obtain a complete structural signal of the microvia 13.

[0029] The photodetector 33 receives the forward excitation signal and the reverse excitation signal and converts the signals into electrical signals. The photodetector 33 is one or a combination selected from a photodiode (PD), an avalanche photodiode (APD), a charge-coupled device (CCD), and a photomultiplier tube (PMT). In the figures of the present invention, the light source module 30 and the photodetector 33 are a coaxial system.

[0030] The signal processing and image generation module 34 is coupled with the photodetector 33 and used to receive and process the electrical signal to generate an image 42 of the geometric structure of the microvia 13. Due to its high resolution, the geometric structure image 42 reveals the three-dimensional via wall shape of the microvia 13 and its defects. As shown in Figure 11, the slight, high-brightness curve 45 in the figure represents the vertical shape of the via wall. The signal processing and image generation module 34 includes a digital signal processor, a high-performance computer, or dedicated firmware, and can process the electrical signal from the photodetector 33 in real time. Furthermore, it can use algorithms to generate high-resolution images of the geometric structure, and can also perform defect identification and quantitative analysis. The generated image of the microvia can reveal the via wall shape of the microvia, identify defects in the via wall (e.g., cracks, weak areas, material heterogeneity, etc.), and provide accurate geometric structure information, including features such as via diameter, depth, and shape.

[0031] As shown in Figure 6, the present invention realizes an inspection method based on the second embodiment described above. The system provides excitation light 35, focuses the excitation light 35, and directs it into the interior of a microvia 13 having a high aspect ratio characteristic from the front surface 11 of the sample 10, thereby generating a forward excitation signal. The interface 31 on the back surface 12 of the sample 10 is provided, and the excitation light 35 incident on the microvia 13 is reflected to become reverse excitation light 36, which returns from the back surface 12 of the sample 10 to the inside of the microvia 13, thereby generating a reverse excitation signal. Control the excitation light 35 and its associated optical articles, one or a combination of the sample 10, to propel along the vertical axis, thereby generating the forward and reverse excitation signals of the microvia 13 layer by layer. The forward excitation signal and the reverse excitation signal are received, and these signals are converted into electrical signals. This includes generating an image of the three-dimensional via wall shape of the microvia 13 and its defects based on the electrical signal.

[0032] As shown in Figure 7, in the third embodiment of the present invention, the sample 10 is a light-transmitting material and includes, but is not limited to, silicon. In this embodiment, the sample 10 is stacked on a stage 50, and an interface 31 that contacts the sample 10 is provided on the stage 50.

[0033] Based on a third embodiment, the present invention provides an inspection method for inspecting internal defects in a semiconductor substrate. The method is as follows: The method includes: providing excitation light 35, focusing the excitation light 35 and directing it onto a designated region 60 of the sample 10 from the front surface 11 of the sample 10, thereby generating a forward excitation signal for the designated region 60; the interface 31 reflecting the excitation light 35 that has passed through the sample 10 to become reverse excitation light 36, which returns to the designated region 60 of the sample 10 from the back surface 12 of the sample 10, thereby generating a reverse excitation signal for the designated region 60; receiving the forward excitation signal and the reverse excitation signal and converting the signals into electrical signals; and generating a two-dimensional image relating to the designated region 60 based on the electrical signals.

[0034] In the third embodiment, as shown in the figure, the excitation light 35 and the reverse excitation light 36 are coaxial.

[0035] As shown in Figure 8, in the fourth embodiment of the present invention, the sample 10 is a light-transmitting material and includes, but is not limited to, silicon. In this embodiment, the sample 10 is stacked on a stage 50, and an interface 31 that contacts the sample 10 is provided on the stage 50.

[0036] Based on a fourth embodiment, the present invention provides an inspection method for inspecting internal defects in semiconductor materials or package substrates. The method is as follows: The method includes: providing excitation light 35, focusing the excitation light 35 and directing it onto a designated region 60 of the sample 10 from the front surface 11 of the sample 10, thereby generating a forward excitation signal for the designated region 60; the interface 31 reflecting the excitation light 35 that has passed through the sample 10 to become reverse excitation light 36, which returns to the designated region 60 of the sample 10 from the back surface 12 of the sample 10, thereby generating a reverse excitation signal for the designated region 60; controlling one or a combination of the excitation light 35 and its associated optical articles and the sample 10 to propel along a vertical axis, thereby generating the forward and reverse excitation signals of the designated region 60 layer by layer; receiving the forward and reverse excitation signals and converting the signals into electrical signals; and generating a three-dimensional image of the designated region 60 based on the electrical signals.

[0037] In the fourth embodiment, as shown in the figure, the excitation light 35 and the reverse excitation light 36 are coaxial. [Explanation of Symbols]

[0038] 10 samples 11 Front 12 Back side 13 Microvias 21 Non-metallic layer 22 Non-metallic layer 23 Electrode layer / metal layer 24 Silicon base layer 25 Reflective layer 30 Light Source Modules 31 Interface 32 Vertical Axis Propulsion Module 33 Photodetector 34 Signal Processing and Image Generation Module 35 Excitation light 36 Reverse excitation light 41 Images of geometric structures 42 Images of geometric structures 43 Cross-sectional shape of microvias 44 High-brightness section 45 High-brightness slight curve 50 stages 60 Designated Areas

Claims

1. The sample is positioned at the examination location, A light source module that provides excitation light, causes the excitation light to enter the interior of a microvia having a high aspect ratio from the front of the sample, thereby generating a forward excitation signal, The interface used to generate a reverse excitation signal is one in which the excitation light incident on the microvia is reflected to become reverse excitation light, which returns to the interior of the microvia from the back surface of the sample, A photodetector that receives the forward excitation signal and the reverse excitation signal and converts the signals into electrical signals, A signal processing and image generation module coupled with the aforementioned photodetector is used to receive and process the electrical signal to generate an image of the geometric structure of the microvia, wherein the image of the geometric structure has the characteristic of high resolution to represent the two-dimensional shape in the forward and reverse directions of the via wall of the microvia and its defects, An optical inspection system for semiconductor substrates, including...

2. The optical inspection system for a semiconductor substrate according to claim 1, characterized in that the interface is a reflective layer provided in the sample structure.

3. The optical inspection system for a semiconductor substrate according to claim 1, characterized in that the interface is a reflective layer, the reflective layer is provided on the surface of a stage, and the reflective layer supports the back surface of the sample.

4. The optical inspection system for a semiconductor substrate according to claim 1, characterized in that the interface includes a structural layer fixed to the back surface of the sample or inside the sample and capable of reflecting light rays.

5. The optical inspection system for a semiconductor substrate according to claim 1, characterized in that the detector is one or a combination selected from a photodiode (PD), an avalanche photodiode (APD), a charge-coupled device (CCD), and a photomultiplier tube (PMT).

6. The optical inspection system for a semiconductor substrate according to claim 1, characterized in that the wavelength of the excitation light is 1200 to 1800 nm.

7. The optical inspection system for a semiconductor substrate according to claim 1, characterized in that the excitation light is an ultrafast laser.

8. The optical inspection system for a semiconductor substrate according to claim 1, characterized in that the light source module and the photodetector are a coaxial system.

9. The sample is positioned at the examination location, A light source module that provides excitation light, causes the excitation light to enter the interior of a microvia having a high aspect ratio from the front of the sample, thereby generating a forward excitation signal, An interface used to generate a reverse excitation signal by reflecting the excitation light incident on the microvia back into the microvia as reverse excitation light, A photodetector used to receive the forward excitation signal and the reverse excitation signal and to convert the signals into electrical signals, A vertical axis propulsion module controls one or a combination of the light source module, the photodetector and associated optical articles, and the sample to propel along the vertical axis, and generates the forward excitation signal and the reverse excitation signal of the microvia layer by layer along the propulsion direction, Coupled with the aforementioned photodetector, the electrical signal is received and processed to generate an image of the geometric structure of the microvia, and the image of the geometric structure, due to its high resolution, represents the three-dimensional via wall shape of the microvia and its defects. An optical inspection system for semiconductor substrates, including...

10. The optical inspection system for a semiconductor substrate according to claim 9, characterized in that the interface is a reflective layer provided in the structure of the sample.

11. The optical inspection system for a semiconductor substrate according to claim 9, characterized in that the interface is a reflective layer, the reflective layer is provided on the surface of a stage, and the reflective layer supports the back surface of the sample.

12. The optical inspection system for a semiconductor substrate according to claim 9, characterized in that the interface includes a structural layer fixed to the back surface or inside the sample and capable of reflecting light rays.

13. The optical inspection system for a semiconductor substrate according to claim 9, characterized in that the photodetector is one or a combination selected from a photodiode (PD), an avalanche photodiode (APD), a charge-coupled device (CCD), and a photomultiplier tube (PMT).

14. The optical inspection system for a semiconductor substrate according to claim 9, characterized in that the wavelength of the excitation light is 1200 to 1800 nm.

15. The optical inspection system for a semiconductor substrate according to claim 9, characterized in that the excitation light is an ultrafast laser.

16. The optical inspection system for a semiconductor substrate according to claim 9, characterized in that the light source module and the photodetector are a coaxial system.

17. The system provides excitation light, and causes the excitation light to enter the interior of a microvia having a high aspect ratio from the front of the sample, thereby generating a forward excitation signal. The objective is to provide an interface used to generate a reverse excitation signal by reflecting the excitation light incident on the microvia back into the microvia as reverse excitation light, The forward excitation signal and the reverse excitation signal are received, and the signals are converted into electrical signals. Based on the aforementioned electrical signal, an image relating to the two-dimensional via wall shape of the microvia and its defects is generated. An optical inspection method for semiconductor substrates, including [the specified component].

18. The optical inspection method for a semiconductor substrate according to claim 17, characterized in that the excitation light and the reverse excitation light are coaxial.

19. The system provides excitation light, and causes the excitation light to enter the interior of a microvia having a high aspect ratio from the front of the sample, thereby generating a forward excitation signal. The objective is to provide an interface used to generate a reverse excitation signal by reflecting the excitation light incident on the microvia back into the microvia as reverse excitation light, Control the excitation light and its associated optical articles, one or a combination of the samples, to propel along the vertical axis, thereby generating the forward excitation signal and the reverse excitation signal of the microvia layer by layer. The forward excitation signal and the reverse excitation signal are received, and the signals are converted into electrical signals. Based on the aforementioned electrical signal, an image relating to the three-dimensional via wall shape of the microvia and its defects is generated. An optical inspection method for semiconductor substrates, including [the specified component].

20. The optical inspection method for a semiconductor substrate according to claim 19, characterized in that the excitation light and the reverse excitation light are coaxial.

21. The system provides excitation light, causes the excitation light to be incident on a designated area of ​​the sample from the front of the sample, thereby generating a forward excitation signal for the designated area. The interface is provided, and the excitation light is reflected back to the designated region as reverse excitation light, thereby generating a reverse excitation signal for the designated region. The forward excitation signal and the reverse excitation signal are received, and the signals are converted into electrical signals. Based on the aforementioned electrical signal, an image relating to the specified region is generated. An optical inspection method for semiconductor substrates, including [the specified component].

22. The optical inspection method for a semiconductor substrate according to claim 21, characterized in that the excitation light and the reverse excitation light are coaxial.

23. The system provides excitation light, causes the excitation light to be incident on a designated area of ​​the sample from the front of the sample, thereby generating a forward excitation signal for the designated area. The interface is provided, and the excitation light is reflected back to the designated region as reverse excitation light, thereby generating a reverse excitation signal for the designated region. Control the excitation light and its associated optical articles, one or a combination of the samples, to propel along the vertical axis, thereby generating the forward excitation signal and the reverse excitation signal for each layer in the designated region. The forward excitation signal and the reverse excitation signal are received, and the signals are converted into electrical signals. Based on the aforementioned electrical signal, a three-dimensional image relating to the specified region is generated. An optical inspection method for semiconductor substrates, including [the specified component].

24. The optical inspection method for a semiconductor substrate according to claim 23, characterized in that the excitation light and the reverse excitation light are coaxial.

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