Optical structure, preparation method and application
By converting the first nitride layer into a high nitrogen content in the silicon nitride photoelectric integrated structure, the second nitride region with high nitrogen content is solved, and the challenges of the traditional structure in interface smoothness and stress management are achieved, and the optical structure with different refractive indexes and periodic changes are improved, thereby improving the controllability of optical performance.
Patent Information
- Application Number
- CN202311760759.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-19
- Publication Date
- 2025-06-27
AI Technical Summary
Traditional silicon nitride photoelectric integrated structures have challenges in interface smoothness and stress management, resulting in an impact on optical performance.
By converting the first nitride at the target position in the nitride layer of the semiconductor element, a second nitride region with a nitrogen content higher than the first nitride is formed, and an optical structure with different refractive indices is formed. This method uses plasma-enhanced chemical vapor deposition process and decoupling plasma nitriding process to achieve quantitative and domain nitrogen doping to avoid the impact of etching quality on the optical properties of the structure.
An optical structure with different refractive indexes and periodic variations in a uniform silicon nitride layer is realized, which simplifies the process flow, reduces stress and thermal budget requirements, and improves the controllability of optical performance.
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Figure CN120215019A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of photon integration technology, and in particular, to an optical structure, a preparation method and an application thereof. Background Art
[0002] As a common optical thin film dielectric material with good compatibility, silicon nitride has a refractive index between that of silicon dioxide and silicon, with a low refractive index, a large band gap and a wide transparent optical window, and can achieve the function of broadband low loss in integrated photon devices. By adjusting relevant gas parameters during the preparation process, a silicon-rich silicon nitride thin film material with relatively high refractive index, which retains the optical properties of ordinary silicon nitride, can also be prepared, so that the refractive index range of silicon nitride material is extended to between 1.9 and 3.2, and the corresponding extinction coefficient and nonlinear coefficient also have a controllable range, which greatly enriches the degree of freedom of material selection in device design.
[0003] In traditional optoelectronic integration structures using silicon nitride materials, silicon dioxide is often used as a cladding layer or a substrate layer, on which silicon nitride is deposited, and then the corresponding optical structure is formed by etching; or trenches are first etched on silicon dioxide, then silicon nitride is deposited to fill the trenches, and the corresponding optical structure is formed therein. The above two methods both utilize the refractive index difference between silicon nitride and silicon dioxide to achieve the required optical effect, so certain requirements are imposed on the interface properties and quality of these two different materials. Especially the etching process when forming the sidewalls may cause the problem of poor interface smoothness, and a relatively rough interface may have a greater impact on the optical performance of its structure. Moreover, when two different materials are used as film layers, certain requirements are imposed on the stress problem that may be brought by deposition and the thermal budget of the overall device, thus increasing the process difficulty. Summary of the Invention
[0004] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art, and to provide an optical structure, a preparation method and an application thereof.
[0005] To achieve the above purpose, the technical solution of the present invention is as follows:
[0006] The present invention provides an optical structure, including:
[0007] A first nitride layer of a semiconductor element provided on a substrate;
[0008] A second nitride region of the same semiconductor element located in the first nitride layer, wherein the nitrogen content in the second nitride is higher than that in the first nitride, so that the second nitride region has a refractive index different from that of the first nitride layer, and the second nitride is formed by converting the first nitride at a target position.
[0009] Further, the second nitride region is exposed on the surface of the first nitride layer, or the second nitride region is completely embedded in the first nitride layer.
[0010] Further, there are one or more second nitride regions, and the plurality of second nitride regions form a repeating periodic structure.
[0011] Further, the semiconductor element includes silicon, the first nitride and the second nitride include silicon nitride, and the second nitride is formed by nitrogen addition to the first nitride at a target position to convert it.
[0012] Further, a dielectric layer is provided on the surface of the substrate, the first nitride layer is provided on the surface of the dielectric layer, the substrate includes a silicon substrate, and the dielectric layer includes a silicon dioxide layer.
[0013] The present invention also provides a method for preparing an optical structure, including:
[0014] Providing a substrate;
[0015] Forming a first nitride layer of a semiconductor element on the substrate;
[0016] Performing a conversion process on the first nitride at a target position in the first nitride layer to form a second nitride region with a nitrogen content higher than that of the first nitride.
[0017] Further, the forming a first nitride layer of a semiconductor element on the substrate specifically includes:
[0018] Forming a dielectric layer on the surface of the substrate;
[0019] Forming a silicon nitride layer on the surface of the dielectric layer as the first nitride layer;
[0020] The performing a conversion process on the first nitride at a target position in the first nitride layer to form a second nitride region with a nitrogen content higher than that of the first nitride specifically includes:
[0021] Forming a mask pattern for defining the target position on the surface of the first nitride layer;
[0022] Through the mask pattern, nitrogen doping is performed on the first nitride layer at the target position, so that the first nitride at the target position is converted into a second nitride with an increased nitrogen content, thereby forming a second nitride region with a nitrogen content higher than that of the first nitride at the target position.
[0023] Further, the silicon nitride layer is formed by a plasma enhanced chemical vapor deposition process and by changing the ratio of reactants; and / or, a mask pattern for defining one or more target positions is formed by a patterning process, and nitrogen doping is performed by a decoupled plasma nitridation process to correspondingly form one or more surface-exposed second nitride regions having different refractive indices from the first nitride layer at one or more target positions, and when forming a plurality of second nitride regions, a repetitive periodic structure is formed; and / or, further comprising: repeating the formation of another layer of the first nitride layer on the first nitride layer by the same process to cover the second nitride regions; and / or, the substrate comprises a silicon substrate, and the dielectric layer comprises a silicon dioxide layer.
[0024] The present invention also provides an application of the above optical structure or an optical structure prepared by the above method for preparing an optical structure in the field of photonic integration.
[0025] Further, the application includes forming a photonic integration device by the optical structure, and the photonic integration device includes a grating coupler or a photonic crystal.
[0026] It can be seen from the above technical solutions that the present invention forms a second nitride region (the silicon nitride in the second nitride region has a higher nitrogen content) with a nitrogen content higher than that of the first nitride in the first nitride layer at the target position, so that the second nitride region has a different refractive index from the first nitride layer, thereby forming an optical structure with different refractive indices and periodic changes in the uniform first nitride layer thin film. Further, the first nitride layer is formed by a plasma enhanced chemical vapor deposition process, and by utilizing its advantages of lower reaction temperature and smaller stress of the deposited thin film, controllability of the thermal budget and stress can be achieved; nitrogen doping is performed by a decoupled plasma nitridation process, and quantitative and localized nitrogen doping can be realized for the formed first nitride layer thin film to form silicon nitride thin film regions with different Si:N atomic number ratios, and a periodic optical structure with refractive index differences can be realized. At the same time, the problem of the influence of etching quality on the optical performance of the structure is avoided, providing a new technical idea for further developing a silicon nitride optoelectronic integration platform. The optical structure can be used to form photonic integration devices such as grating couplers or photonic crystals. The structure of the present invention is novel, simple to implement and compatible with existing processes, and has the advantages of controllability in terms of thermal budget and stress. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figures 1 - 2 It is a schematic diagram of an optical structure according to a preferred embodiment of the present invention.
[0028] Figures 3 - 7 It is a schematic diagram of the process steps of a method for preparing an optical structure according to a preferred embodiment of the present invention. Detailed implementation manners
[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The words such as "including" used herein mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects.
[0030] The following further elaborates on the detailed implementation manners of the present invention with reference to the accompanying drawings.
[0031] Reference Figure 1 An optical structure of the present invention includes a first nitride layer 11 disposed on a substrate 10 and formed by a nitride of a semiconductor element, and a second nitride region 12 located in the first nitride layer 11 and formed by a nitride of the same semiconductor element.
[0032] The second nitride of the second nitride region 12 is formed by the same element as the first nitride of the first nitride layer 11. The difference is that the nitrogen content in the second nitride is higher than that in the first nitride, that is, the ratio of the number of nitrogen atoms to the semiconductor element in the second nitride is higher than the ratio of the number of nitrogen atoms to the semiconductor element in the first nitride of the first nitride layer 11 outside the second nitride region 12. Therefore, the second nitride region 12 has a refractive index different from that of the first nitride layer 11, that is, a refractive index difference is formed between the second nitride region 12 and the surrounding first nitride layer 11. Thus, an optical structure with different refractive indices is formed in the uniform first nitride layer 11 film.
[0033] Among them, the second nitride is formed by converting the first nitride at a target position in the first nitride layer 11, so as to form the second nitride region 12 at the target position in the first nitride layer 11.
[0034] In some embodiments, the second nitride region 12 is exposed on the surface of the first nitride layer 11, as Figure 1 shown.
[0035] In other embodiments, the second nitride region 12 is completely buried in the first nitride layer 11, as Figure 2As shown. Further, the first nitride layer 11 includes a first sub-nitride layer 111 and a second sub-nitride layer 112 stacked in sequence; the second nitride region 12 is located below the surface of the first sub-nitride layer 111, and the second sub-nitride layer 112 covers the second nitride region 12 from above, so that the second nitride region 12 is completely buried in the first nitride layer 11.
[0036] Reference Figures 1 - 2 . In some embodiments, there are multiple second nitride regions 12.
[0037] The multiple second nitride regions 12 form a repeating periodic structure. Figure 1 shows a case where multiple second nitride regions 12 (exemplarily 5) are arranged at intervals in sequence along the surface of the first nitride layer 11 to form a repeating periodic structure. Figure 2 shows a case where multiple second nitride regions 12 (exemplarily 5) are arranged at intervals in sequence in the first nitride layer 11 to form a repeating periodic structure.
[0038] In other embodiments, there may also be 1 second nitride region 12.
[0039] In some embodiments, the above semiconductor element includes silicon, the first nitride and the second nitride include silicon nitride, but the nitrogen content in the silicon nitride of the second nitride is higher than that in the silicon nitride of the first nitride.
[0040] Further, the second nitride is formed by nitriding a certain region of the first nitride at a target position in the first nitride layer 11, so that the first nitride at the target position undergoes a transformation with an increased nitrogen content.
[0041] In some embodiments, a dielectric layer 13 is provided on the surface of the substrate 10, and the first nitride layer 11 is provided on the surface of the dielectric layer 13.
[0042] Further, the substrate 10 includes a silicon substrate 10. The dielectric layer 13 includes a silicon dioxide layer.
[0043] The following further details a method for preparing an optical structure of the present invention through specific embodiments in conjunction with the drawings.
[0044] Reference Figures 3 - 7 . A method for preparing an optical structure of the present invention can be used to prepare an optical structure such as the above Figure 1 and includes the following steps:
[0045] Step S1: Provide a substrate 10.
[0046] As Figure 3As shown, a semiconductor silicon substrate 10 is employed to form an optical structure of the present invention on the silicon substrate 10.
[0047] Step S2: Form a first nitride layer 11 of semiconductor elements on the substrate 10.
[0048] As Figure 3 shown, a dielectric layer 13 may be first formed on the surface of the substrate 10, and the required first nitride layer 11 is further formed on the surface of the dielectric layer 13.
[0049] In some embodiments, the dielectric layer 13 may be a silicon dioxide layer. The semiconductor element is, for example, silicon to form a silicon nitride layer as the first nitride layer 11.
[0050] Then, a first nitride layer 11 of silicon nitride is formed on the surface of the dielectric layer 13.
[0051] In some embodiments, a uniform silicon nitride layer is formed as the first nitride layer 11 on the surface of the dielectric layer 13 by plasma-enhanced chemical vapor deposition process.
[0052] Furthermore, when performing the plasma-enhanced chemical vapor deposition process, by using the method of changing the reactant ratio (such as adjusting the relevant process gas parameters), a uniform thin film of the first nitride layer 11 of silicon-rich silicon nitride is formed, which can retain the optical properties of ordinary silicon nitride and has a relatively high refractive index. In this way, the refractive index range of the material of the first nitride layer 11 can be extended to between 1.9 and 3.2, and the corresponding extinction coefficient and nonlinear coefficient also have a controllable range, thus greatly enriching the degree of freedom of material selection in device design.
[0053] At the same time, using the plasma-enhanced chemical vapor deposition process, its reaction temperature is relatively low, and the film stress of the deposited first nitride layer 11 can be made smaller, so the thermal budget and stress are both relatively controllable.
[0054] Step S3: Perform a conversion process on the first nitride at the target position 16 in the first nitride layer 11 to form a second nitride region 12 with a nitrogen content higher than that of the first nitride.
[0055] As Figure 4 shown, then, a mask pattern 141 for defining the required target position 16 is formed on the surface of the first nitride layer 11.
[0056] In some embodiments, to form a pattern that matches Figure 1Taking the corresponding five second nitride regions 12 as an example, a mask layer 14 is first formed on the surface of the first nitride layer 11. Then, through photolithography and etching processes, the mask layer 14 is patterned to form a plurality of mask patterns 141 for defining five target positions 16 (where five second nitride regions 12 can be formed). An opening 15 is formed between two adjacent mask patterns 141, preparing for subsequent localized conversion processing (nitrogen doping).
[0057] As Figure 5 shown, then, through the mask pattern 141, the first nitride layer 11 at the target position 16 is subjected to nitrogen doping conversion processing.
[0058] In some embodiments, a decoupled plasma nitridation process (DPN) is adopted, and through the opening 15 of the mask pattern 141, nitrogen doping is carried out downward from the surface of the first nitride layer 11 located in the opening 15 to the target position 16 below the opening 15.
[0059] It can be understood that during nitrogen doping, due to the shielding effect of the patterned mask layer 14, there will be no doping of nitrogen atoms at the positions covered by the mask layer 14, while at the target positions 16 not covered by the mask layer 14, the nitrogen atom content will increase due to nitrogen incorporation. Thus, five second nitride regions 12 with exposed surfaces are correspondingly formed at the five target positions 16, and compared with the first nitride layer 11, they have a higher nitrogen content. As a result, the refractive indices of the five formed second nitride regions 12 are different from that of the first nitride layer 11, that is, it is necessary to make the refractive index of the second nitride region 12 less than that of the first nitride layer 11.
[0060] After nitrogen doping, the first nitride at the five target positions 16 will be converted into a second nitride with an increased nitrogen content, thus forming five second nitride regions 12 arranged in a repeated periodic structure in sequence below the surface of the first nitride layer 11, and the nitrogen content of the second nitride region 12 at the target position 16 is higher than that of the surrounding first nitride layer 11, as Figure 6 shown.
[0061] By performing nitrogen doping on the first nitride layer 11, using the characteristic that the refractive index can vary widely between 1.9 and 3.2 due to the change of coefficients x and y in Si x N y an optical structure with different refractive indices / periodic changes can be formed in the uniform first nitride layer 11 thin film.
[0062] The method for forming one second nitride region with a different refractive index can be implemented with reference to the above steps. The difference is only that one second nitride region does not form a repeated periodic structure, so it will not be elaborated here.
[0063] The structure after removing the mask pattern 141 is as Figure 7 shown. Thus, an optical structure consistent with Figure 1 is formed.
[0064] Furthermore, through the same plasma-enhanced chemical vapor deposition process, a second layer of the first nitride layer can be repeatedly formed on the already formed first nitride layer 11 of the first layer to cover the second nitride region 12. Thus, an optical structure consistent with Figure 2 is formed (in this embodiment, the first nitride layer 11 of the first layer corresponds to Figure 2 the first sub-nitride layer 111 in Figure 2 and the second layer of the first nitride layer corresponds to
[0065] Compared with the traditional silicon nitride optical device with silica as the cladding, such as a grating coupler, in the second nitride region 12 where nitrogen doping is carried out by the DPN process in the present invention, since the nitrogen / silicon atomic ratio is higher than that of the surrounding first nitride layer 11, the second nitride region 12 can also form a refractive index difference with the surrounding first nitride layer 11, and then a periodic structure with different refractive indexes is formed. Therefore, optical properties similar to those of a conventional silicon nitride grating coupler with silica as the cladding can be achieved. Moreover, the method of the present invention can avoid the stress problem during the deposition of silicon nitride in the past, effectively reduce the thermal budget, and does not need to consider the influence of etching quality on the optical properties of the structure.
[0066] The present invention adopts the DPN technology to realize quantitative and localized nitrogen doping of the deposited first nitride layer 11 thin film to form a second nitride region 12 with different Si:N ratios, and a periodic structure with different refractive indexes can be realized. Furthermore, by using the silicon nitride thin film with a controllable Si:N ratio distribution and uneven refractive index distribution, an optical structure or device with certain functions can be formed, providing a new technical idea for the further development of the silicon nitride optoelectronic integration platform, so that the above optical structure of the present invention or the optical structure prepared by the above optical structure preparation method can be applied in the field of photon integration.
[0067] In some embodiments, the application of the above optical structure of the present invention in the field of photon integration may include forming a photon integration device through the optical structure. For example, the photon integration device includes a grating coupler or a photonic crystal.
[0068] In summary, in the present invention, the first nitride (silicon nitride) in the first nitride layer 11 at the target position 16 is subjected to a conversion process to form a second nitride region 12 with a nitrogen content higher than that of the first nitride (the nitrogen content of the silicon nitride in the second nitride region 12 is higher), so that the second nitride region 12 has a refractive index different from that of the first nitride layer 11. Thus, an optical structure with different refractive indices and periodic variations can be formed in the uniform first nitride layer 11 thin film. Further, the first nitride layer 11 is formed by a plasma-enhanced chemical vapor deposition process. By utilizing its advantages of lower reaction temperature and smaller stress of the deposited thin film, the controllability of the thermal budget and stress can be achieved. Through a decoupled plasma nitridation process for nitrogen doping, quantitative and localized nitrogen doping can be carried out on the formed first nitride layer 11 thin film to form silicon nitride thin film regions with different Si:N atomic number ratios, enabling a periodic optical structure with refractive index differences. At the same time, the problem of considering the influence of etching quality on the optical performance of the structure is avoided, providing a new technical idea for the further development of a silicon nitride optoelectronic integration platform. The optical structure can be used to form photonic integration devices such as grating couplers or photonic crystals. The structure of the present invention is novel, simple to implement and compatible with existing processes, and has the advantages of controllability in terms of thermal budget and stress.
[0069] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.
Claims
1. An optical structure, characterized in that, Comprising: A first nitride layer of a semiconductor element provided on a substrate; A second nitride region of the same semiconductor element located in the first nitride layer, the nitrogen content in the second nitride being higher than that in the first nitride, such that the second nitride region has a refractive index different from that of the first nitride layer, and the second nitride is formed by transforming the first nitride at a target position.
2. The optical structure according to claim 1, characterized in that, The second nitride region is exposed on the surface of the first nitride layer, or the second nitride region is completely embedded in the first nitride layer.
3. The optical structure according to claim 1, characterized in that, The second nitride regions are one or more, and the plurality of second nitride regions form a repeating periodic structure.
4. The optical structure according to claim 1, characterized in that, The semiconductor element includes silicon, the first nitride and the second nitride include silicon nitride, and the second nitride is formed by nitrogen addition and transformation of the first nitride at a target position.
5. The optical structure according to claim 1, characterized in that, A dielectric layer is provided on the surface of the substrate, the first nitride layer is provided on the surface of the dielectric layer, the substrate includes a silicon substrate, and the dielectric layer includes a silicon dioxide layer.
6. A method for preparing an optical structure, characterized in that, Comprising: Providing a substrate; Forming a first nitride layer of a semiconductor element on the substrate; Performing a transformation process on the first nitride at a target position in the first nitride layer to form a second nitride region with a nitrogen content higher than that of the first nitride.
7. The method for preparing an optical structure according to claim 6, wherein The forming of the first nitride layer of the semiconductor element on the substrate specifically includes: Forming a dielectric layer on the surface of the substrate; Forming a silicon nitride layer on the surface of the dielectric layer as the first nitride layer; The performing of the transformation process on the first nitride at a target position in the first nitride layer to form a second nitride region with a nitrogen content higher than that of the first nitride specifically includes: Forming a mask pattern for defining the target position on the surface of the first nitride layer; Through the mask pattern, nitrogen doping is performed on the first nitride layer at the target position, so that the first nitride at the target position is transformed into a second nitride with an increased nitrogen content, thereby forming a second nitride region with a nitrogen content higher than that of the first nitride at the target position.
8. The method for preparing an optical structure according to claim 7, wherein, The silicon nitride layer is formed by a plasma enhanced chemical vapor deposition process and by changing the ratio of reactants; and / or, through a patterning process, the mask pattern for defining one or more target positions is formed, and nitrogen doping is performed through a decoupled plasma nitridation process, and one or more surface-exposed second nitride regions with a refractive index different from that of the first nitride layer are correspondingly formed at one or more target positions, and when forming a plurality of second nitride regions, a repeating periodic structure is formed; and / or, further comprising: repeating the formation of another layer of the first nitride layer on the first nitride layer by the same process and covering the second nitride region; and / or, the substrate includes a silicon substrate, and the dielectric layer includes a silicon dioxide layer.
9. Application of an optical structure prepared by the method for preparing an optical structure according to any one of claims 1-5 or an optical structure according to any one of claims 6-8 in the field of photon integration.
10. The application according to claim 9, characterized in that, The application includes forming a photonic integrated device through the optical structure, and the photonic integrated device includes a grating coupler or a photonic crystal.