Preparation method of optical waveguide
The groove structure of the optical waveguide is formed through the embossing process, which solves the problems of rough side walls and inaccurate angles caused by the etching process and realizes the preparation of low-loss optical waveguides.
Patent Information
- Application Number
- CN202410295933.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-14
- Publication Date
- 2025-09-16
AI Technical Summary
During the preparation of silicon photonic waveguides, the etching process causes the groove sidewall stripes to be not smooth enough and the sidewall angle cannot reach 90°, which increases the transmission loss of the optical waveguide.
An imprinting process is used to form a structural layer with a groove structure, and an optical waveguide is formed by filling the groove structure, avoiding an etching process and ensuring that the sidewall is smooth and the angle is 90°.
The transmission loss of the optical waveguide is reduced, and the side smoothness and angle accuracy are improved.
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Figure CN120652614A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of semiconductor technology, and in particular to a method for preparing an optical waveguide. Background Art
[0002] Silicon photonics technology is an optical communication technology that uses laser beams instead of electronic semiconductor signals to transmit data. It is a new generation of technology based on silicon and silicon-based substrate materials, using existing complementary metal oxide semiconductor (CMOS) processes for the development and integration of optical devices. It has the advantages of fast transmission speed, large bandwidth and low loss.
[0003] Optical waveguides utilize the phenomenon of total internal reflection, that is, when light enters a medium with a lower refractive index from a medium with a high refractive index, the light will be completely reflected back without passing through the medium boundary, thereby achieving stable and fast signal transmission.
[0004] The current method for preparing silicon photonic waveguides is as follows: first, a transparent low-refractive-index dielectric layer is prepared on the substrate surface, and then photolithography and etching are performed to form grooves in the low-refractive-index dielectric layer; second, the formed grooves are filled with a material with a high refractive index; finally, a layer of material with the same refractive index as the low-refractive-index dielectric layer is prepared to cover the high-refractive-index material to form an optical waveguide.
[0005] It should be noted that the above introduction to the technical background is merely intended to provide a clear and complete description of the technical solutions of this application and facilitate understanding by those skilled in the art. Simply because these solutions are described in the background technology section of this application, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention
[0006] The inventors of this application discovered that when etching processes are used in the preparation of silicon optical waveguides, especially for high-density materials such as silicon oxide, silicon nitride, and lithium niobate, the etching process will form stripes on the sidewalls of the grooves. In addition, the angle of the groove sidewalls may not reach 90°, thereby increasing the transmission loss of the optical waveguide.
[0007] To address the aforementioned problems, or at least similar problems, embodiments of the present application provide a method for fabricating an optical waveguide. In this method, a structural layer having a groove structure is formed by an imprinting process, and an optical waveguide is formed by filling the groove structure. The optical waveguide is fabricated without an etching process during the entire fabrication process. Therefore, problems such as uneven groove sidewall stripes and sidewall angles that cannot reach 90° caused by the etching process are avoided at the source, resulting in the optical waveguide having lower transmission loss.
[0008] According to an embodiment of the present application, a method for preparing an optical waveguide is provided, the method comprising:
[0009] forming a first material layer on a surface of the substrate, wherein the first material layer has a first refractive index;
[0010] forming a structural layer on the surface of the first material layer using an embossing process, wherein a groove structure is formed in the structural layer;
[0011] Filling a second material layer in the groove structure of the structural layer, wherein the second material layer has a second refractive index, and the second refractive index is higher than the first refractive index;
[0012] removing the structural layer; and
[0013] A third material layer is formed to cover the top and sidewalls of the second material layer, wherein the third material layer has a third refractive index lower than the second refractive index.
[0014] In at least some embodiments, the first refractive index is equal to the third refractive index.
[0015] In at least some embodiments, the first material layer is silicon oxide.
[0016] The second material layer is silicon nitride,
[0017] The third material layer is silicon oxide.
[0018] In at least some embodiments, forming a structural layer on the surface of the first material layer using an embossing process includes:
[0019] forming a structural layer material on the surface of the first material layer, wherein the structural layer material contains resin; and
[0020] The pattern of the embossed replica is copied into the structural layer material by using an embossing process to form the groove structure in the structural layer material.
[0021] In at least some embodiments, forming a structural layer on the surface of the first material layer using an embossing process further includes:
[0022] The structural layer material is thinned by a dry stripping process to remove the structural layer material at the bottom of the groove structure, so that the surface of the first material layer is exposed from the bottom of the groove structure.
[0023] In at least some embodiments, forming a structural layer on the surface of the first material layer using an embossing process further includes:
[0024] Before forming the structural layer material, the surface of the first material layer is treated with oxygen plasma.
[0025] In at least some embodiments, filling the groove structure of the structural layer with a second material layer includes:
[0026] depositing the second material layer, where the second material layer covers the surface of the structural layer and fills the groove structure, and the second material layer in the groove structure contacts the surface of the first material layer; and
[0027] The second material layer is thinned to remove the second material layer on the surface of the structure layer and expose the surface of the structure layer around the groove structure.
[0028] In at least some embodiments, removing the structural layer includes:
[0029] The structural layer is completely removed through a physical dry debonding process.
[0030] In at least some embodiments, forming a third material layer covering a top portion and sidewalls of the second material layer includes:
[0031] Depositing the third material layer on the top and sidewalls of the second material layer; and
[0032] The third material layer is thinned so that the surfaces of the third material layer are in the same plane and the top of the second material layer is not exposed.
[0033] The beneficial effect of the present application is that in the optical waveguide preparation method of the present application, a structural layer having a groove structure is formed by an imprinting process, and an optical waveguide is formed by filling the groove structure. The etching process is avoided in the entire preparation process. Therefore, problems such as the groove sidewall stripes being not smooth enough and the sidewall angle not being able to reach 90 degrees caused by the etching process are avoided from the source, resulting in the optical waveguide having lower transmission loss.
[0034] With reference to the following description and accompanying drawings, specific embodiments of the present application are disclosed in detail, indicating the manner in which the principles of the present application can be employed. It should be understood that the embodiments of the present application are not limited in scope. Within the spirit and scope of the appended claims, the embodiments of the present application include many variations, modifications and equivalents.
[0035] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.
[0036] It should be emphasized that the term "include / comprising" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The included drawings are used to provide a further understanding of the embodiments of the present application, which constitute a part of the specification, are used to illustrate the implementation methods of the present application, and together with the text description, explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive work. In the drawings:
[0038] Figure 1 This is a schematic diagram of the process structure formed after the first buried oxide layer is combined with the substrate in this application;
[0039] Figure 2a This is a schematic diagram of the process structure formed after the structural layer of the present application is combined with the first buried oxide layer;
[0040] Figure 2b This is a schematic diagram of the imprinting process structure in which the nanoimprint replica plate is covered on the surface of the structural layer;
[0041] Figure 2c This is a schematic diagram of forming a nano-groove structure in a structural layer according to the present application;
[0042] Figure 2d This is a schematic diagram of the process structure after the structural layer of this application is modified and the groove structure primer is removed;
[0043] Figure 3a This is a schematic diagram of the process structure for forming a waveguide layer within a groove of a structural layer in this application;
[0044] Figure 3b This is a schematic diagram of the process structure after the entire waveguide layer is thinned until the structural layer is exposed;
[0045] Figure 4 This is a schematic diagram of the process structure of forming a ridge waveguide structure after removing the structural layer of this application;
[0046] Figure 5a This is a schematic diagram of the process structure of forming an optical waveguide by covering the first buried oxide layer with the second buried oxide layer and the ridge waveguide structure of the present application;
[0047] Figure 5b This is a schematic diagram of the silicon optical waveguide formed after the second buried oxide layer is thinned in this application;
[0048] Figure 6 It is a schematic diagram of the method for preparing the optical waveguide of the present application.
[0049] In the figure: 10 substrate, 20 first buried oxide layer, 30 structural layer, 40 waveguide layer, 50 nano-imprint replica plate, 60 second buried oxide layer. DETAILED DESCRIPTION
[0050] The above and other features of the present application will become apparent through the following description with reference to the accompanying drawings. In the description and the accompanying drawings, specific embodiments of the present application are disclosed in detail, which illustrate some embodiments in which the principles of the present application can be adopted. It should be understood that the present application is not limited to the described embodiments. On the contrary, the present application includes all modifications, variations and equivalents that fall within the scope of the appended claims.
[0051] In the description of the various embodiments of the present application, for the convenience of description, the direction parallel to the surface of the substrate is called "lateral", the direction perpendicular to the surface of the substrate is called "longitudinal", and the dimension in the "longitudinal" direction can be called "height" or "thickness"; in the "longitudinal", the direction from the back of the substrate to the surface is called the "upper" direction, and the direction opposite to the "upper" direction is the "lower" direction; the surface of the substrate can have a central axis parallel to the "longitudinal", the direction around the central axis is called "circumferential", and the radial direction along the central axis is called "radial".
[0052] It should be noted that the above-mentioned “up” direction and “down” direction are only for the convenience of description and do not limit the orientation or posture of the optical waveguide of the present application during preparation or use.
[0053] Example
[0054] Figure 6 FIG. 1 is a schematic diagram of the method for preparing the optical waveguide of the present application. Figure 6 As shown, the method for preparing the optical waveguide includes:
[0055] 601. Form a first material layer on a surface of a substrate, wherein the first material layer has a first refractive index;
[0056] 602. Form a structural layer on the surface of the first material layer using an embossing process, wherein a groove structure is formed in the structural layer;
[0057] 603. Fill the groove structure of the structural layer with a second material layer, where the second material layer has a second refractive index higher than the first refractive index;
[0058] 604. Remove the structural layer; and
[0059] 605. Form a third material layer covering the top and sidewalls of the second material layer, wherein the third material layer has a third refractive index lower than the second refractive index.
[0060] In the optical waveguide preparation method of the present application, a structural layer having a groove structure is formed by an imprinting process, and an optical waveguide is formed by filling the groove structure, and then the structural layer is removed. The entire preparation process avoids the etching process of the low-refractive-index medium in the prior art. Therefore, problems such as the groove sidewall stripes not being smooth enough and the sidewall angle not being able to reach 90° caused by the etching process are avoided from the source. An optical waveguide with improved side surface smoothness and a side surface angle of 90° can be formed, so that the optical waveguide has lower transmission loss.
[0061] In at least one example, the first refractive index is equal to the third refractive index.
[0062] For example, the first material layer is silicon oxide with a first refractive index of n=1.45; the second material layer is silicon nitride with a second refractive index of n=4; and the third material layer is silicon oxide with a third refractive index of n=1.45. Furthermore, the present application is not limited thereto, and the first, second, and third material layers may also be other materials.
[0063] In at least one example, the substrate in operation 601 is, for example, silicon (e.g., N-type silicon or P-type silicon), silicon on insulator (SOI), silicon germanium, or other semiconductor substrates or insulating substrates commonly used in semiconductor manufacturing processes.
[0064] In at least one example, in operation 602, forming a structure layer on the surface of the first material layer using an embossing process includes:
[0065] 6021. Forming a structural layer material on the surface of the first material layer, wherein the structural layer material contains resin; and
[0066] 6022. Using an embossing process, copy the pattern of the embossed replica into the structural layer material to form the groove structure in the structural layer material.
[0067] The groove structure may, for example, extend along a first direction on the surface of the first material layer.
[0068] In at least one example, in operation 602, forming a structural layer on the surface of the first material layer using an embossing process, in addition to operations 6021 and 6022, further includes the following operation 6023:
[0069] 6023. Thin the structural layer material through a dry degumming process to remove the structural layer material at the bottom of the groove structure, so that the surface of the first material layer is exposed from the bottom of the groove structure.
[0070] Through operation 6023 , the surface of the first material layer can be exposed from the bottom of the groove structure.
[0071] In at least one example, in operation 602, forming a structural layer on the surface of the first material layer using an embossing process, in addition to operations 6021 and 6022, further includes the following operation 6020:
[0072] 6020. Before forming the structural layer material (ie, before operation 6021), the surface of the first material layer is treated with oxygen plasma.
[0073] Through operation 6020, the structural layer is bonded to the surface of the first material layer.
[0074] In at least one example, in operation 603, filling the groove structure of the structural layer with a second material layer includes:
[0075] 6031. Deposit the second material layer, where the second material layer covers the surface of the structural layer and fills the groove structure, and the second material layer in the groove structure contacts the surface of the first material layer; and
[0076] 6032. Thin the second material layer to remove the second material layer on the surface of the structural layer and expose the surface of the structural layer around the groove structure.
[0077] In at least one example, in operation 604, removing the structural layer includes:
[0078] The structural layer is completely removed through a physical dry debonding process.
[0079] In at least one example, in operation 605, forming a third material layer covering a top portion and sidewalls of the second material layer includes:
[0080] 6051. Depositing the third material layer on the top and sidewalls of the second material layer; and
[0081] 6052. Thin the third material layer so that the surfaces of the third material layer are in the same plane and the top of the second material layer is not exposed.
[0082] Through the above steps, the second material layer with a higher refractive index extends in the first direction, and the four sides of the second material layer (i.e., the surfaces parallel to the first direction) are covered by the first material layer and the third material layer with a lower refractive index, thereby forming an optical waveguide structure.
[0083] Next, combine Figure 1 - The specific example of FIG5 further illustrates the method for preparing the optical waveguide of the present application.
[0084] Step 1, preparation of the first buried oxide layer, corresponding to the above-mentioned operation 601:
[0085] like Figure 1 As shown, a layer of low refractive index material is prepared on the surface of the N-type silicon substrate 10 by a PECVD process or other methods to form a first buried oxide layer 20, which corresponds to the aforementioned first material layer.
[0086] For example, the material of the first buried oxide layer 20 is silicon oxide with a refractive index n=1.45, and the thickness of the first buried oxide layer 20 is 15000 nanometers.
[0087] In addition, the first buried oxide layer 20 may also have other thicknesses, and the first material layer may also be made of other materials.
[0088] Step 2, structural layer preparation, corresponds to the above-mentioned operation 602:
[0089] In some examples, such as Figure 2a to Figure 2d As shown, the groove structure is obtained by directly forming the groove structure in the structure layer 30 on the surface of the first buried oxide layer 20 through an imprint process (for example, an ultraviolet nanoimprint lithography process), thereby achieving step 2.
[0090] For example, step 2 may include the following steps ①, ②, and ③.
[0091] ① Structural layer preparation, corresponding to the above operation 6021: Figure 2a As shown, a structure layer 30 with a thickness of 800 nanometers is formed on the surface of the first buried oxide layer 20 by a spin coating process.
[0092] For example, the structure layer 30 is heated at 100° C. for 90 seconds.
[0093] For example, the material of the structural layer 30 may include resin. For example, the material of the structural layer 30 is nanoimprint photoresist, and the nanoimprint photoresist may be composed of materials such as resin, photosensitizer, organic solvent, inorganic silicon oxide particles, and additives.
[0094] In some examples, before spin coating the structural layer 30 , the surface of the first buried oxide layer 20 is treated with O 2 plasma to remove organic matter on the surface and attach oxygen-containing (polar) molecules to increase the surface energy and achieve high hydrophilicity.
[0095] The specific process of O2 Plasma (oxygen plasma) treatment is shown in Table 1:
[0096] Table 1
[0097] gas ICP Power RF Power Preassure Temperature time O2=3000sccm 1000W 0 10Torr 107℃ 300s
[0098] ②Nanoimprint lithography process, corresponding to the above operation 6022: Figure 2bAs shown, a nanoimprint replica plate 50 with nanostructures is placed on the surface of the structural layer 30, and then mechanical force is applied to the surface of the nanoimprint replica plate 50. Then, ultraviolet light is used to cure the structural layer 30. Finally, the nanoimprint replica plate 50 is separated from the structural layer 30 and demoulded. The structural layer 30 with nanostructures is replicated on the surface of the first buried oxide layer 20. The result is shown in FIG. Figure 2c shown.
[0099] The specific process of nanoimprint lithography is shown in Table 2:
[0100] Table 2
[0101] Contact Speed UV Separate Speed Preassure Temperature Stamp 2mm / s 300s 1mm / s 50000Pa 40 PS
[0102] Among them, the nanoimprint replica plate 50 used in the nanoimprint lithography process can be prepared by the following method: polydimethylsiloxane (PDMS) is molded on the surface of a hard matrix nanoimprint mold, mechanical force is applied and heated at 60° for 12 hours to solidify and demold to obtain the nanoimprint replica plate 50.
[0103] ③ Structural layer modification, corresponding to the above-mentioned operation 6023: the structural layer 30 is thinned as a whole by a dry degumming process, and the nanoimprint glue in the concave part of the groove structure of the structural layer 30 is the base glue of the structural layer 30. The base glue in the concave part of the groove structure of the structural layer 30 is completely removed, and the smoothness and inclination of the side wall of the groove structure are further improved, so that the first buried oxide layer 20 in the concave part of the groove structure of the structural layer 30 is exposed to the surface, as shown in FIG. Figure 2d shown.
[0104] The specific process of the structural layer modification process is shown in Table 3:
[0105] Table 3
[0106] gas ICP Power RF Power Preassure Temperature time 02=3000sccm 1000W 0 10Torr 107℃ 60s
[0107] Step 3, waveguide layer preparation, corresponds to the above operation 603:
[0108] like Figure 3a-3b As shown, a layer of high refractive index material (ie, the second material layer mentioned above) is first prepared in the groove structure of the structural layer 30 to form a waveguide layer, and finally a ridge waveguide structure capable of transmission is obtained on the surface of the first buried oxide layer 20 .
[0109] Step 3 includes the following steps ① and ②.
[0110] ① Waveguide layer deposition: such as Figure 3a As shown, the groove pattern of the structural layer 30 is filled with a layer of high refractive index material by physical vapor deposition (PVD);
[0111] Specifically, the material of the waveguide layer 40 is silicon nitride with a high refractive index n=4.
[0112] Specifically, the waveguide layer 40 is formed by combining the first buried oxide layer 20 exposed on the surface at the recessed portion of the groove structure of the structural layer 30, filling the entire groove structure of the structural layer 30, and also forming a waveguide layer 40 on the entire surface of the structural layer 30 on both sides of the groove structure.
[0113] ②Thinning of waveguide layer: Figure 3b As shown, the entire waveguide layer 40 is ground and thinned by a chemical mechanical polishing process until the waveguide layer 40 on the raised portion of the surface of the structural layer 30 is completely removed, so that the entire surface of the structural layer 30 on both sides of the groove structure in the structural layer 30 is completely exposed. At this time, the waveguide layer filling the entire groove structure of the structural layer 30 is on the same horizontal plane as the entire structural layer 30 on both sides of the groove structure in the structural layer 30.
[0114] Step 4, structural layer removal, corresponds to the above operation 604:
[0115] The structural layer 30 is completely removed by a dry stripping process, and only a ridge waveguide structure remains on the surface of the first buried oxide layer 20 to form a ridge waveguide structure.
[0116] The specific process of removing the structural layer is shown in Table 4:
[0117] Table 4
[0118] gas ICP Power RF Power Preassure Temperature time O2=5000sccm 1000W 0 10Torr 250℃ 600s
[0119] For example, after the structural layer 30 is completely removed, the device after step 4 is cleaned using an organic cleaning solution (e.g., EKC solution) to remove the polymer on the surface of the first buried oxide layer 20 and the ridge waveguide structure, thereby improving the bonding quality of the second buried oxide layer 60 with the surface.
[0120] Step 5, preparing the second buried oxide layer, corresponds to the above operation 605:
[0121] like Figure 5a-5b As shown, a layer of material with the same refractive index as the first buried oxide layer 20 (i.e., the third material layer mentioned above) is deposited on the entire surface of the first buried oxide layer 20 to completely cover and wrap the ridge waveguide structure on the surface of the first buried oxide layer 20 and finally form a silicon optical waveguide.
[0122] Step 5 includes the following steps ① and ②:
[0123] ① Preparation of the second buried oxide layer: Figure 5aAs shown, a second buried oxide layer 60 is deposited on the entire surface of the first buried oxide layer 20 by a PECVD process or other deposition process. The second buried oxide layer 60 completely covers and wraps the ridge waveguide structure on the surface of the first buried oxide layer 2.
[0124] ②Thinning of the second buried oxide layer: Figure 5b As shown, chemical mechanical polishing is used to thin the second buried oxide layer 60 as a whole until the protruding portion of the second buried oxide layer 60 is completely removed, and the entire surface of the second buried oxide layer 60 is in the same plane, and the ridge waveguide structure is not exposed, thereby finally forming a silicon photonic passive optical waveguide.
[0125] The present application uses nanoimprinting to directly form a groove structure on the surface of the first buried oxide layer in one go, and forms an optical waveguide by filling the groove structure. No etching process is involved in the entire preparation process, which avoids problems such as the side wall stripes not being smooth enough and the side wall angle not being able to reach 90° caused by etching, and has extremely low transmission loss.
[0126] The present application has been described above in conjunction with specific embodiments. However, those skilled in the art should understand that these descriptions are merely illustrative and are not intended to limit the scope of protection of the present application. Those skilled in the art may make various modifications and variations to the present application based on the spirit and principles of the present application, and such modifications and variations are also within the scope of the present application.
Claims
1. A method for preparing an optical waveguide, characterized in that: The method comprises: forming a first material layer on a surface of the substrate, wherein the first material layer has a first refractive index; forming a structural layer on the surface of the first material layer using an embossing process, wherein a groove structure is formed in the structural layer; Filling the groove structure of the structural layer with a second material layer, wherein the second material layer has a second refractive index, and the second refractive index is higher than the first refractive index; removing the structural layer; and A third material layer is formed to cover the top and sidewalls of the second material layer, wherein the third material layer has a third refractive index lower than the second refractive index.
2. The method for preparing an optical waveguide according to claim 1, wherein: The first refractive index is equal to the third refractive index.
3. The method for preparing an optical waveguide according to claim 1, wherein: The first material layer is silicon oxide, The second material layer is silicon nitride, The third material layer is silicon oxide.
4. The method for preparing an optical waveguide according to claim 1, wherein: Forming a structural layer on the surface of the first material layer using an embossing process, comprising: forming a structural layer material on the surface of the first material layer, wherein the structural layer material contains resin; and The pattern of the embossed replica is copied into the structural layer material by using an embossing process to form the groove structure in the structural layer material.
5. The method for preparing an optical waveguide according to claim 4, wherein: The method further comprises: forming a structural layer on the surface of the first material layer by using an embossing process; The structural layer material is thinned by a dry stripping process to remove the structural layer material at the bottom of the groove structure, so that the surface of the first material layer is exposed from the bottom of the groove structure.
6. The method for preparing an optical waveguide according to claim 4, wherein: The method further comprises: forming a structural layer on the surface of the first material layer by using an embossing process; Before forming the structural layer material, the surface of the first material layer is treated with oxygen plasma.
7. The method for preparing an optical waveguide according to claim 1, wherein: Filling the groove structure of the structural layer with a second material layer comprises: depositing the second material layer, where the second material layer covers the surface of the structural layer and fills the groove structure, and the second material layer in the groove structure contacts the surface of the first material layer; and The second material layer is thinned to remove the second material layer on the surface of the structure layer and expose the surface of the structure layer around the groove structure.
8. The method for preparing an optical waveguide according to claim 1, wherein: Removing the structural layer, comprising: The structural layer is completely removed through a physical dry debonding process.
9. The method for preparing an optical waveguide according to claim 1, wherein: forming a third material layer covering the top and sidewalls of the second material layer, comprising: Depositing the third material layer on the top and sidewalls of the second material layer; and The third material layer is thinned so that the surfaces of the third material layer are in the same plane and the top of the second material layer is not exposed.