Detection structure and method of silicon nitride waveguide, semiconductor device and preparation method thereof
By setting a detection structure with grating couplers and mode field conversion units on silicon nitride waveguides, visible light is used to detect appearance defects in silicon nitride waveguides, solving the problems of low detection efficiency and high cost in existing technologies, and achieving low-cost and high-efficiency detection results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI INTEGRATED CIRCUIT RESEARCH & DEVELOPMENT CENTER CO LTD
- Filing Date
- 2024-12-31
- Publication Date
- 2026-06-30
AI Technical Summary
In the existing technology, silicon nitride waveguides have low detection efficiency and high cost, mainly because the detection method relies on infrared cameras, which makes it difficult to efficiently detect appearance defects such as surface depressions, cracks or breaks.
The detection structure employs a grating coupler and a mode field conversion unit, and utilizes visible light for detection. This includes directional coupling between the grating coupler and the silicon nitride waveguide, filling the cladding gap, and utilizing the scattering phenomenon of visible light to detect defects.
It reduces detection costs and improves detection efficiency. The location of defects is clearly displayed through the scattering of visible light, making it easy for the human eye or ordinary cameras to observe.
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Figure CN122307826A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of silicon-based optoelectronics technology, and in particular to a detection structure and method for a silicon nitride waveguide, a semiconductor device and its fabrication method. Background Technology
[0002] With the rapid development of silicon-based optoelectronic technology, the number of on-chip integrated photonic devices has also shown an exponential growth trend. However, unlike electronic devices such as transistors, photonic devices such as waveguides usually require a longer length (hundreds of micrometers or millimeters) to ensure stable transmission of optical modes, thereby realizing functions such as interference, polarization conversion, and coupling.
[0003] Due to their relatively long length, silicon nitride waveguides are prone to surface defects such as depressions, cracks, or breaks during manufacturing. Depressions or cracks cause scattering of light modes during transmission, increasing waveguide loss. Breaks prevent light modes from propagating within the waveguide, resulting in all light energy being scattered into the silicon dioxide. Effective failure analysis of these defects helps identify failed devices and pinpoint the causes of failures, enabling optimization of processes, designs, and products.
[0004] Currently, there is a relative lack of methods for detecting and analyzing surface defects (dents, cracks, or breaks) on waveguides. The primary method still relies on microscopic observation, such as using an infrared camera to capture scattered infrared light for defect detection and location, followed by specific failure analysis. However, due to the narrow width and long length of silicon nitride waveguides, this detection method is inefficient and requires high resolution from the infrared camera, resulting in both high cost and low efficiency for silicon nitride waveguide testing. Summary of the Invention
[0005] The purpose of this invention is to provide a detection structure and method for silicon nitride waveguides, a semiconductor device and its fabrication method, for low-cost and high-efficiency detection of the appearance of silicon nitride waveguides.
[0006] To solve the above-mentioned technical problems, the present invention provides a detection structure for a silicon nitride waveguide, wherein the two ends of the silicon nitride waveguide are an input optical coupling region and an output optical coupling region, respectively, and the detection structure includes:
[0007] A grating coupler is used to couple visible light.
[0008] A mode field conversion unit is connected to the grating coupler and arranged at one end of the silicon nitride waveguide near the input light coupling region. The mode field conversion unit and the adjacent silicon nitride waveguide form a directional coupler for coupling visible light into the adjacent silicon nitride waveguide and conducting it to the output light coupling region in the silicon nitride waveguide.
[0009] A cladding layer is used to cover the grating coupler and the mode conversion unit, and to fill the gap between the mode conversion unit and the silicon nitride waveguide.
[0010] Optionally, the grating coupler is made of silicon nitride, and the grating coupler has a grating duty cycle of 0.2 to 0.8, a grating depth of 100 nanometers to 500 nanometers, and a grating period of 200 nanometers to 500 nanometers.
[0011] Optionally, a connection unit is also provided to connect the grating coupler and the mode field conversion unit. The mode field conversion unit includes a first end and a second end opposite to each other. The first end is connected to the connection unit, and the portion of the mode field conversion unit located between the first end and the second end is optically coupled to the silicon nitride waveguide.
[0012] Optionally, the mode field conversion unit is a taper structure, with the width of the first end being greater than the width of the second end.
[0013] Optionally, the side facing the silicon nitride waveguide between the first end and the second end is the fourth side, and the side opposite to the fourth side in the taper structure is the third side. The fourth side is parallel to the adjacent silicon nitride waveguide, and the third side is inclined relative to the adjacent silicon nitride waveguide.
[0014] Optionally, the width of the first end is 200 nm to 1000 nm, the width of the second end is 70 nm to 150 nm, the length of the mode field conversion unit is 30 μm to 100 μm, and the gap between the fourth surface and the adjacent silicon nitride waveguide is 100 nm to 500 nm.
[0015] Optionally, the grating coupler and the mode field conversion unit are made of silicon nitride, and the filling cladding is made of silicon oxide.
[0016] Based on another aspect of the present invention, a method for detecting silicon nitride waveguides is also provided, comprising:
[0017] Provide the detection structure as described above;
[0018] Visible light matching the grating coupler is input into the grating coupler, and the presence of visible light scattering points on the surface of the silicon nitride waveguide is detected. If so, it is determined that there is an appearance defect at the location of the visible light scattering point in the silicon nitride waveguide; otherwise, it is determined that there is no appearance defect in the silicon nitride waveguide.
[0019] According to another aspect of the present invention, a semiconductor device is also provided, comprising:
[0020] Semiconductor device layer;
[0021] A silicon nitride waveguide is disposed on the semiconductor device layer;
[0022] The detection structure described above is disposed on the semiconductor device layer and close to the silicon nitride waveguide, and the detection structure is used to detect the silicon nitride waveguide.
[0023] According to another aspect of the present invention, a method for fabricating a semiconductor device is also provided, comprising:
[0024] Provide substrate;
[0025] A semiconductor device layer is formed on the substrate;
[0026] A silicon nitride waveguide and the detection structure described above are simultaneously formed on the semiconductor device layer.
[0027] In summary, this invention provides a detection structure and method for a silicon nitride waveguide, a semiconductor device, and a method for fabricating the same. The detection structure is used to detect surface defects in the silicon nitride waveguide. The detection structure includes a grating coupler, a mode conversion unit, and a cladding layer. The grating coupler is used to couple visible light. The mode conversion unit, connected to the grating coupler, is arranged parallel to the end of the silicon nitride waveguide near the input optical coupling region. The mode conversion unit and the adjacent silicon nitride waveguide form a directional coupler, used to couple visible light into the adjacent silicon nitride waveguide and conduct it to the output optical coupling region within the silicon nitride waveguide. The cladding layer covers the grating coupler and the mode conversion unit, and fills the gap between the mode conversion unit and the silicon nitride waveguide. In this application, the detection structure is positioned near the input optical coupling region of the silicon nitride waveguide to couple visible light into the adjacent silicon nitride waveguide, allowing the visible light to conduct to the output optical coupling region within the silicon nitride waveguide, thereby detecting surface defects on the surface of the silicon nitride waveguide. Compared to infrared light, which is costly and difficult to detect, the detection structure of this application uses visible light (e.g., 400 nm to 700 nm) as the detection light, thereby reducing detection costs. Furthermore, since visible light is easy to observe—for example, by the human eye or a regular camera—detection efficiency can be improved. Additionally, the wavelength of visible light is shorter than that of infrared light input from the input light coupling region, making the scattering phenomenon of visible light upon encountering surface defects more pronounced and thus more conducive to observation. Attached Figure Description
[0028] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention.
[0029] Figure 1 This is a top view schematic diagram of the detection structure of the silicon nitride waveguide provided in the embodiments of this application;
[0030] Figure 2 This is a cross-sectional schematic diagram of the grating coupler provided in the embodiments of this application;
[0031] Figure 3 A top view schematic diagram of the coupling between the mode field conversion unit and the silicon nitride waveguide provided in an embodiment of this application;
[0032] Figure 4 A flowchart illustrating the detection method for silicon nitride waveguides provided in this application embodiment;
[0033] Figure 5 A cross-sectional schematic diagram of a semiconductor device provided in an embodiment of this application;
[0034] Figure 6 A flowchart illustrating a method for fabricating a semiconductor device according to an embodiment of this application.
[0035] In the attached figures: 10-Silicon nitride waveguide; 11-Input optical coupling region; 12-Output optical coupling region; 20-Detection structure; 21-Grate coupler; 24-Directional coupler; 22-Connection unit; 23-Mode field conversion unit; 25-Covering cladding; 23a-First end; 23b-Second end; 23c-Third surface; 23d-Fourth surface; 31-SOI substrate; 32-Semiconductor device layer. Detailed Implementation
[0036] To make the objectives, advantages, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clarify the explanation of the embodiments of this invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and may sometimes use different scales.
[0037] As used in this invention, the singular forms “a,” “an,” and “the” include plural objects; the term “or” is generally used to mean “and / or”; the term “a number” is generally used to mean “at least one”; and the term “at least two” is generally used to mean “two or more”. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature, unless otherwise expressly indicated.
[0038] This application provides a detection structure for a silicon nitride waveguide.
[0039] Figure 1 This is a top view schematic diagram of the detection structure of the silicon nitride waveguide provided in the embodiments of this application.
[0040] like Figure 1 As shown, the detection structure of the silicon nitride waveguide provided in this embodiment includes a grating coupler 21, a mode conversion unit 23, and a cladding layer 25. The grating coupler 21 is used to couple visible light. The mode conversion unit 23 is connected to the grating coupler 21 and is arranged in parallel at one end of the silicon nitride waveguide 10 near the input light coupling region 11. The mode conversion unit 23 and the adjacent silicon nitride waveguide 10 form a directional coupler 24, used to couple visible light into the adjacent silicon nitride waveguide 10 and conduct it to the output light coupling region 12 within the silicon nitride waveguide 10. The cladding layer 25 covers the grating coupler 21 and the mode conversion unit 23, and fills the gap between the mode conversion unit 23 and the silicon nitride waveguide 10.
[0041] The silicon nitride waveguide 10 to be tested is disposed on the semiconductor device layer 32. The silicon nitride waveguide 10 is linear and protrudes from the surface of the semiconductor device layer 32. The two ends of the silicon nitride waveguide 10 are an input optical coupling region 11 and an output optical coupling region 12, respectively. The input optical coupling region 11 is used to couple input light (e.g., guiding light input from an optical fiber into the silicon nitride waveguide 10), and the output optical coupling region 12 is used to couple output light (e.g., guiding light from the silicon nitride waveguide 10 to another optical fiber). In one example, the width of the silicon nitride waveguide 10 can be 500 nm to 5000 nm, the thickness (height) can be 200 nm to 1000 nm, and the length can be determined according to requirements, such as hundreds of micrometers to thousands of micrometers.
[0042] The detection structure 20 is positioned adjacent to the silicon nitride waveguide 10 and is used to detect surface defects on the silicon nitride waveguide 10. Please refer to [link / reference needed]. Figure 1The grating coupler 21 can be positioned close to the input light coupling region 11. The parameters of the grating coupler 21 are matched with the wavelength of the light to be coupled into the silicon nitride waveguide 10 (i.e., the light used for detection) to provide high coupling efficiency. Compared to infrared light, which is costly and difficult to detect, the detection structure 20 of this application uses visible light (e.g., 400 nm to 700 nm) as the light used for detection to reduce detection costs. Moreover, since visible light is easy to observe, detection efficiency can also be improved. In this application, the grating coupler 21 is made of silicon nitride and can be formed synchronously with the coupling region structure of the silicon nitride waveguide 10. Therefore, except for parameters of the grating coupler 21 that are independent of the coupled light wavelength (e.g., grating depth), which can be set with reference to the coupling region structure of the silicon nitride waveguide 10, other parameters of the grating coupler 21 (e.g., grating period) can be matched with the coupled light wavelength. In one example, such as Figure 2 The diagram shows a cross-sectional view of the grating coupler 21, which is encased in a filling cladding 25. The grating duty cycle (W2 / W1) of the grating coupler 21 is 0.2 to 0.8, the grating depth h is 100 nm to 500 nm, and the grating period (W1) varies according to the wavelength of the coupled light, for example, 200 nm to 500 nm. In another example, the visible light used for detection is light in the 500 nm to 650 nm band (green / red light) to facilitate human eye recognition, and the grating period of the grating coupler is matched to the visible light in the aforementioned band.
[0043] The mode field conversion unit 23 is connected to the grating coupler 21 and is positioned near the input light coupling region 11 of the silicon nitride waveguide 10. The mode field conversion unit 23 and the adjacent silicon nitride waveguide 10 form an asymmetric directional coupler 24, which couples visible light into the adjacent silicon nitride waveguide 10 and conducts it to the output light coupling region 12 within the silicon nitride waveguide 10. The cladding layer 25 covers the grating coupler 21 and the mode field conversion unit 23, and fills the gap between the mode field conversion unit 23 and the silicon nitride waveguide 10. The cladding layer 25 also covers the outer wall of the silicon nitride waveguide 10. The mode field conversion unit 23 and the grating coupler 21 are made of the same material, for example, silicon nitride. The refractive index of the cladding layer 25 is lower than that of the grating coupler 21, and the material of the cladding layer 25 can be, for example, silicon oxide.
[0044] Please continue to refer to Figure 1A connecting unit 22 is also provided between the grating coupler 21 and the mode field conversion unit 23 for connecting the grating coupler 21 and the mode field conversion unit 23. The connecting unit 22 can be a waveguide with a width relatively narrower than the silicon nitride waveguide 10, used to guide visible light to the vicinity of the silicon nitride waveguide 10. The material of the connecting unit 22 can be the same as the material of the mode field conversion unit 23 and the grating coupler 21. The mode field conversion unit 23 includes a first end 23a and a second end 23b opposite to each other. The first end 23a is connected to the connecting unit 22 for receiving visible light. The first end 23a faces the input optical coupling region 11, and the second end 23b faces the output optical coupling region 12. In this application, the mode field conversion unit 23 can be a tapered structure (i.e., conical in shape). The portion of the tapered structure between the first end 23a and the second end 23b is optically coupled to the silicon nitride waveguide 10. The width of the first end 23a (top view) is greater than the width of the second end 23b to improve coupling efficiency and shorten the length of the mode field conversion unit 23 (i.e., coupling length), thereby relatively increasing the detection length of the silicon nitride waveguide 10. The side of the tapered structure 23 facing the silicon nitride waveguide 10 between the first end 23a and the second end 23b (i.e., the side closer to the silicon nitride waveguide 10) is the fourth surface 23d, and the side of the tapered structure 23 opposite to the fourth surface 23d (i.e., the side farther from the silicon nitride waveguide 10) is the third surface 23c. The fourth surface 23d and / or the third surface 23c are tilted relative to the adjacent silicon nitride waveguide 10.
[0045] Figure 3 This is a top view schematic diagram showing the coupling between the mode field conversion unit and the silicon nitride waveguide provided in this embodiment. Figure 3 As shown, the third surface 23c is tilted relative to the adjacent silicon nitride wave, and the fourth surface 23d is parallel or nearly parallel to the adjacent silicon nitride wave to further improve the coupling efficiency of the directional coupler 24. The width of the first end 23a of the mode field conversion unit 23 is W3, the width of the second end 23b is W4, and the length is L (i.e., the coupling length between the mode field conversion unit 23 and the silicon nitride waveguide 10). The gap between the mode field conversion unit 23 and the silicon nitride waveguide 10 is W5. By adjusting W3, W4, W5, and L, the coupling length L can be shortened as much as possible while ensuring that the mode field conversion unit 23 achieves low insertion loss during mode field conversion (efficiently coupling visible light into the silicon nitride waveguide 10), thereby achieving the longest possible detection length for the silicon nitride waveguide 10. In one example, the width W3 of the first end 23a can be matched with the width of the connecting unit 22, and the width of the first end 23a can be, for example, 200 nm to 1000 nm. The width W4 of the second end 23b is 70 nm to 150 nm. The length L of the mode field conversion unit 23 is 30 μm to 100 μm. The gap W5 between the fourth surface 23d and the adjacent silicon nitride waveguide 10 is 100 nm to 500 nm.
[0046] In other examples of this application, the mode field conversion unit 23 may also be other structures that perform mode field conversion on visible light and achieve optical coupling (forming a directional coupler) with the adjacent silicon nitride waveguide. For example, the mode field conversion unit may also be rectangular (i.e., the width of the first end and the second end are the same or close), and the side of the mode field conversion unit close to the silicon nitride waveguide is not parallel to the adjacent silicon nitride waveguide (i.e., the fourth side is not parallel to the adjacent silicon nitride waveguide).
[0047] This application also provides a method for detecting silicon nitride waveguides.
[0048] Figure 4 A flowchart illustrating the detection method for silicon nitride waveguides provided in this application embodiment.
[0049] like Figure 4 As shown, the detection method for silicon nitride waveguides provided in this embodiment includes:
[0050] S01: Provide the detection structure as described above;
[0051] S02: Input visible light that matches the grating coupler into the grating coupler, and detect whether there is a visible light scattering point on the surface of the silicon nitride waveguide. If so, determine that there is an appearance defect at the location of the visible light scattering point of the silicon nitride waveguide. If not, determine that there is no appearance defect of the silicon nitride waveguide.
[0052] In step S02, visible light can be input through an optical fiber located above the grating coupler. The wavelength of the visible light matches that of the grating coupler. During the propagation of the visible light along the silicon nitride waveguide to the output optical coupling region, if it encounters surface defects (non-uniformity) such as depressions, cracks, or breaks on the silicon nitride waveguide surface, the visible light will exhibit significant Fresnel scattering at these defects, i.e., scattering points. Conversely, if the silicon nitride waveguide surface does not have these defects, no scattering points will appear. Compared to infrared light, which is costly and difficult to detect, the detection structure of this application uses visible light (e.g., 400 nm to 700 nm) as the detection light, thereby reducing detection costs. Furthermore, since visible light is easy to observe, such as by human observation or with a common camera (e.g., a standard resolution CCD camera), detection efficiency can be improved. In addition, the wavelength of visible light is shorter than that of infrared light input from the input optical coupling region, making the scattering phenomenon of visible light encountering surface defects more obvious, which is also beneficial for observation.
[0053] This application also provides a semiconductor device.
[0054] Figure 5 This is a cross-sectional schematic diagram of a semiconductor device provided in an embodiment of this application.
[0055] like Figure 5 As shown (its sectional view direction is, for example) Figure 1 The semiconductor device provided in this embodiment includes a semiconductor device layer 32, a silicon nitride waveguide 10, and a detection structure 20 (see the cross-sectional view AA in the figure).
[0056] The semiconductor device layer 32 can be disposed on a substrate, such as an SOI substrate 31 or a silicon wafer. The semiconductor device layer 32 contains semiconductor structures corresponding to the formed device, such as circuit structures, electronic device structures, photonic device structures, etc. Figure 5 In the example, the semiconductor device layer 32 is disposed on the SOI substrate 31 and is formed in the top silicon layer of the SOI substrate 31. The semiconductor device layer 32 may contain silicon-based photonic device structures, such as silicon-based waveguides, silicon-based grating couplers, silicon-to-silicon nitride adapters, etc. The surface of the semiconductor device layer 32 is a dielectric material that can be used as a cladding layer, such as silicon oxide.
[0057] Both the silicon nitride waveguide 10 and the detection structure 20 are disposed on the semiconductor device layer 32. The two ends of the silicon nitride waveguide 10 are an input optical coupling region 11 and an output optical coupling region 12, respectively. The detection structure 20 is positioned close to the input optical coupling region 11 of the silicon nitride waveguide 10 to couple visible light into the adjacent silicon nitride waveguide 10, allowing the visible light to propagate through the silicon nitride waveguide 10 to the output optical coupling region 12, thereby detecting surface defects on the silicon nitride waveguide 10. The specific configuration of the detection structure 20 can be found in the aforementioned embodiments and will not be repeated here.
[0058] This application also provides a method for fabricating a semiconductor device, for example, the semiconductor device described above.
[0059] Figure 6 A flowchart illustrating a method for fabricating a semiconductor device according to an embodiment of this application.
[0060] like Figure 6 As shown, the method for fabricating the semiconductor device provided in this embodiment includes:
[0061] S01: Provide substrate;
[0062] S02: A semiconductor device layer is formed on the substrate;
[0063] S03: A silicon nitride waveguide and the detection structure as described above are simultaneously formed on the semiconductor device layer.
[0064] In step S01, the substrate may be an SOI substrate or a silicon wafer.
[0065] In step S02, taking an SOI substrate as an example, the step of forming a semiconductor device layer in the top silicon layer of the SOI substrate includes: First, performing processes such as photolithography, etching, ion implantation, chemical vapor deposition, and chemical mechanical polishing on a portion of the top silicon layer to form circuit structures and electronic device structures in the top silicon layer. Then, forming photonic device structures, such as silicon waveguides, silicon grating couplers, and silicon-silicon nitride adapters, in the remaining portion of the top silicon layer. Finally, forming a cladding layer (the material of which includes, for example, silicon oxide) to cover the surface of the above device structures, fill the gaps between the above device structures, and make the semiconductor device layer have a relatively flat surface.
[0066] In step S03, for example, the material of the detection structure can be the same as that of the silicon nitride waveguide. First, a silicon nitride layer can be formed on the semiconductor device layer using PECVD or LPCVD processes. Then, photolithography and etching processes are performed on the silicon nitride layer to simultaneously form the silicon nitride waveguide and detection structure. Next, a cladding layer (materials such as silicon oxide) is formed to cover the surface of the silicon nitride waveguide and detection structure, filling the gap between the detection structure and the silicon nitride waveguide. Of course, during the photolithography and etching processes on the silicon nitride layer, other silicon nitride-based photonic device structures can also be formed simultaneously, such as the input optical coupling region and output optical coupling region on both sides of the silicon nitride waveguide.
[0067] In summary, this invention provides a detection structure and method for a silicon nitride waveguide, a semiconductor device, and a method for fabricating the same. The detection structure is used to detect surface defects in the silicon nitride waveguide. The detection structure includes a grating coupler, a mode conversion unit, and a cladding layer. The grating coupler is used to couple visible light. The mode conversion unit, connected to the grating coupler, is arranged parallel to the end of the silicon nitride waveguide near the input optical coupling region. The mode conversion unit and the adjacent silicon nitride waveguide form a directional coupler, used to couple visible light into the adjacent silicon nitride waveguide and conduct it to the output optical coupling region within the silicon nitride waveguide. The cladding layer covers the grating coupler and the mode conversion unit, and fills the gap between the mode conversion unit and the silicon nitride waveguide. In this application, the detection structure is positioned near the input optical coupling region of the silicon nitride waveguide to couple visible light into the adjacent silicon nitride waveguide, allowing the visible light to conduct to the output optical coupling region within the silicon nitride waveguide, thereby detecting surface defects on the surface of the silicon nitride waveguide. Compared to infrared light, which is costly and difficult to detect, the detection structure of this application uses visible light (e.g., 400 nm to 700 nm) as the detection light, thereby reducing detection costs. Furthermore, since visible light is easy to observe—for example, by the human eye or a regular camera—detection efficiency can be improved. Additionally, the wavelength of visible light is shorter than that of infrared light input from the input light coupling region, making the scattering phenomenon of visible light upon encountering surface defects more pronounced and thus more conducive to observation.
[0068] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.
Claims
1. A detection structure of a silicon nitride waveguide, two ends of the silicon nitride waveguide are respectively an input light coupling region and an output light coupling region, characterized in that, The detection structure includes: A grating coupler is used to couple visible light. A mode field conversion unit is connected to the grating coupler and arranged at one end of the silicon nitride waveguide near the input light coupling region. The mode field conversion unit and the adjacent silicon nitride waveguide form a directional coupler for coupling visible light into the adjacent silicon nitride waveguide and conducting it to the output light coupling region in the silicon nitride waveguide. A cladding layer is used to cover the grating coupler and the mode conversion unit, and to fill the gap between the mode conversion unit and the silicon nitride waveguide.
2. The detection structure of the silicon nitride waveguide according to claim 1, characterized in that, The grating coupler is made of silicon nitride, and has a grating duty cycle of 0.2 to 0.8, a grating depth of 100 nanometers to 500 nanometers, and a grating period of 200 nanometers to 500 nanometers.
3. The detection structure of the silicon nitride waveguide according to claim 1, characterized in that, The device also includes a connection unit that connects the grating coupler and the mode field conversion unit. The mode field conversion unit includes a first end and a second end that are opposite each other. The first end is connected to the connection unit. The portion of the mode field conversion unit located between the first end and the second end is optically coupled to the silicon nitride waveguide.
4. The detection structure of the silicon nitride waveguide according to claim 3, characterized in that, The mode field conversion unit is a taper structure, and the width of the first end is greater than the width of the second end.
5. The detection structure of the silicon nitride waveguide according to claim 4, characterized in that, The side facing the silicon nitride waveguide between the first end and the second end is the fourth side, and the side opposite the fourth side in the taper structure is the third side. The fourth side is parallel to the adjacent silicon nitride waveguide, and the third side is inclined relative to the adjacent silicon nitride waveguide.
6. The detection structure of the silicon nitride waveguide according to claim 5, characterized in that, The width of the first end is 200 nm to 1000 nm, the width of the second end is 70 nm to 150 nm, the length of the mode field conversion unit is 30 μm to 100 μm, and the gap between the fourth surface and the adjacent silicon nitride waveguide is 100 nm to 500 nm.
7. The detection structure of the silicon nitride waveguide according to claim 1, characterized in that, The grating coupler and the mode field conversion unit are made of silicon nitride, and the filling cladding is made of silicon oxide.
8. A method for detecting silicon nitride waveguides, characterized in that, include: Provide a detection structure as described in any one of claims 1 to 7; Visible light matching the grating coupler is input into the grating coupler, and the presence of visible light scattering points on the surface of the silicon nitride waveguide is detected. If so, it is determined that there is an appearance defect at the location of the visible light scattering point in the silicon nitride waveguide; otherwise, it is determined that there is no appearance defect in the silicon nitride waveguide.
9. A semiconductor device, characterized in that, include: Semiconductor device layer; A silicon nitride waveguide is disposed on the semiconductor device layer; The detection structure according to any one of claims 1 to 7 is disposed on the semiconductor device layer and close to the silicon nitride waveguide, and the detection structure is used to detect the silicon nitride waveguide.
10. A method for fabricating a semiconductor device, characterized in that, include: Provide substrate; A semiconductor device layer is formed on the substrate; A silicon nitride waveguide and a detection structure as described in any one of claims 1 to 7 are simultaneously formed on the semiconductor device layer.