A method for measuring the morphology of an optical waveguide based on nanoimprinting technology

Abstract

The application provides a kind of optical waveguide topography measurement method based on nanoimprint technology, comprising the following steps: obtaining a polymer, and placing the polymer on a to-be-characterized optical waveguide, heating and pressurizing the polymer and the to-be-characterized optical waveguide, so that the to-be-characterized topography pattern of the to-be-characterized optical waveguide is imprinted on the polymer characterization surface of the polymer;Based on scanning electron microscope, the first topography of the polymer characterization surface is identified, and the spatial frequency intensity of the first topography is calculated;Photonic device pattern on the polymer characterization surface is photographed and stored, and the second topography of the optical device integrated on the to-be-characterized optical waveguide formed by analyzing the photonic device pattern. After the above scheme, gold spraying and etching steps will not be introduced on the optical waveguide and other devices, and the overall structure of the wafer will not be damaged.

Description

Technical Field

[0001] This invention relates to the field of micro-nano device manufacturing, and more particularly to a method for measuring the morphology of optical waveguides based on nanoimprint technology. Background Technology

[0002] Photonic integrated circuits (PICs) are a technology that integrates multiple optical components (such as lasers, modulators, waveguides, and detectors) onto a single chip. In recent years, photonic integrated circuits have been widely used in optical communication, sensing, optical computing, and quantum computing due to their superior characteristics such as high speed, low loss, integration, and miniaturization. Optical waveguides are the fundamental devices in photonic integrated circuits, and lower loss is required to achieve better performance. Scattering loss introduced by the roughness of the waveguide sidewalls is the most significant source of loss in optical waveguides. However, due to unavoidable effects in manufacturing processes such as photolithography and etching, sidewall roughness is introduced during manufacturing. Therefore, characterizing and measuring the sidewall roughness is crucial for estimating waveguide loss. Simultaneously, photolithography and etching steps inevitably introduce nanometer-scale effects on the waveguide width, thus impacting device performance. Therefore, characterizing the waveguide width is also very important.

[0003] In existing technologies, the characterization methods for optical waveguides and their sidewall roughness generally utilize atomic force microscopy (AFM) and scanning electron microscopy (SEM) to measure the waveguide sidewall roughness. SEM is a high-resolution morphology analysis instrument, with a resolution of up to 1 nm. However, SEM requires the sample to be conductive, and most optical waveguide materials are non-conductive. Therefore, additional processes such as gold sputtering are needed to make the surface conductive before imaging. Thus, the SEM characterization method requires additional gold sputtering and subsequent etching of a conductive gold layer onto the waveguide after etching. This process may introduce impurities, affecting subsequent cladding growth and ultimately impacting device performance. AFM is an instrument for measuring surface roughness, and it is commonly used for this purpose. For waveguide sidewall roughness, the wafer is typically cleaved into small pieces and placed on an inclined stage for characterization. This damages the entire wafer, making subsequent cladding growth and other processes difficult and hindering large-area manufacturing. Furthermore, since AFM uses probes to scan structures, the characterization range is typically on the micrometer scale, and characterization of large areas would be very slow.

[0004] Therefore, a novel optical waveguide topography measurement method is needed to achieve rapid large-area characterization, as well as accurate characterization results for small regions. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a method for measuring the morphology of optical waveguides based on nanoimprint technology, which does not introduce gold sputtering and etching steps on optical waveguides and other devices, and thus does not damage the overall structure of the wafer.

[0006] This invention discloses a method for measuring the morphology of optical waveguides based on nanoimprint technology, comprising the following steps:

[0007] A polymer is obtained and placed on an optical waveguide to be characterized. The polymer and the optical waveguide to be characterized are heated and pressurized so that the morphology pattern of the optical waveguide to be characterized is imprinted onto the polymer characterization surface of the polymer.

[0008] The first morphology of the polymer characterization surface was identified based on scanning electron microscopy, and the spatial frequency intensity of the first morphology was calculated.

[0009] The photonic device pattern on the polymer characterization surface is captured and stored, and the second morphology of the optical device integrated on the optical waveguide to be characterized is analyzed by the photonic device pattern.

[0010] The steps of identifying the first morphology of the polymer characterization surface based on scanning electron microscopy and calculating the spatial frequency intensity of the first morphology include:

[0011] Sputtering gold onto the polymer characterization surface makes the polymer characterization surface conductive;

[0012] The top-down image of the morphology pattern to be characterized on the polymer characterization surface is captured and stored to form a morphology photograph, and the morphology photograph is converted into a grayscale image.

[0013] The edge regions integrating photonic devices are extracted from the topographic image to obtain the first topography;

[0014] After fitting the first morphology, the edge difference is calculated to obtain the spatial domain roughness function of the edge region where the photonic device is integrated. , where z is the spatial coordinate axis of the optical waveguide direction, and the edge difference is the height difference between the fitted straight line and the protruding edge in the first morphology;

[0015] For the spatial domain roughness function After autocorrelation, we obtain an autocorrelation function. And according to the definition of the autocorrelation function, we get: ,in This is the convolution operator;

[0016] For autocorrelation function Fourier transform yields the frequency domain power spectral density function of the spatial roughness of the edge region. The frequency domain power spectral density function The spatial frequency intensity characterizing the first morphology, and the fitting of the first morphology includes:

[0017] For non-edge locations within the edge region, take the first, second, third, and fourth sampling points;

[0018] Draw circles outward from the first sampling point, the second sampling point, the third sampling point, and the fourth sampling point respectively, until they are tangent to the edge for the first time, and record the tangent points as the first tangent point, the second tangent point, the third tangent point, and the fourth tangent point;

[0019] Connect the first tangent point and the first sampling point and extend the line to intersect the other edge at the first intersection point;

[0020] Connect the second tangent point and the second sampling point and extend it to intersect the other edge at the second intersection point;

[0021] Connect the third tangent point and the third sampling point and extend the line to intersect the other edge at the third intersection point;

[0022] Connect the fourth tangent point and the fourth sampling point and extend the line to intersect the other edge at the fourth intersection point;

[0023] Construct a first rectangle with the first intersection point, the second intersection point, the first tangent point, and the second tangent point as vertices, and take the intersection point of the diagonals of the first rectangle as the first fitting point;

[0024] Construct a second rectangle with the third intersection point, the fourth intersection point, the third tangent point, and the fourth tangent point as vertices, and take the intersection point of the diagonals of the second rectangle as the second fitting point;

[0025] Connect the first and second fitting points to form a fitting straight line, and use the fitting straight line as the topographic reference.

[0026] Preferably, the steps of obtaining a polymer, placing the polymer on an optical waveguide to be characterized, and heating and pressurizing the polymer and the optical waveguide to be characterized, so that the morphology pattern to be characterized of the optical waveguide is imprinted onto the polymer characterization surface of the polymer, include:

[0027] A thermoplastic polymer is obtained and placed on an optical waveguide to be characterized;

[0028] The thermoplastic polymer and the optical waveguide to be characterized are heated until the heating temperature is greater than the glass transition temperature of the thermoplastic polymer, so that the polymer contact surface on the thermoplastic polymer that is in contact with the optical waveguide to be characterized softens.

[0029] Pressurizing the thermoplastic polymer causes the polymer contact surface to be deformed by the optical waveguide to be characterized, so as to reverse the characteristic morphology pattern of the optical waveguide to be characterized to the polymer contact surface.

[0030] After the thermoplastic polymer has cured, it is peeled off from the optical waveguide to be characterized.

[0031] Preferably, the heating temperature is 50℃-200℃, and the pressure applied is 0.5-2MPa;

[0032] Furthermore, when applying pressure to thermoplastic polymers, the pressure should be kept constant while the heating temperature is gradually reduced until the thermoplastic polymer cools and solidifies.

[0033] The thermoplastic polymer is any one of cyclic olefin copolymer (COC) film, polymethyl methacrylate, polyethylene terephthalate, or polycarbonate.

[0034] Preferably, the steps of obtaining a polymer, placing the polymer on an optical waveguide to be characterized, and heating and pressurizing the polymer and the optical waveguide to be characterized, so that the morphology pattern to be characterized of the optical waveguide is imprinted onto the polymer characterization surface of the polymer, include:

[0035] A flexible polymer solution is obtained and then drop-coated onto an optical waveguide to be characterized.

[0036] The flexible polymer solution and the optical waveguide to be characterized are heated until the solvent in the flexible polymer solution evaporates, so that the flexible polymer in the flexible polymer solution is solidified on the optical waveguide to be characterized.

[0037] Flexible polymer was peeled off from the optical waveguide to be characterized.

[0038] Preferably, the flexible polymer solution is polydimethylsiloxane (PDMS), and the solvent in the flexible polymer solution is propylene glycol methyl ether acetate.

[0039] Preferably, the steps of obtaining a polymer, placing the polymer on an optical waveguide to be characterized, and heating and pressurizing the polymer and the optical waveguide to be characterized, so that the morphology pattern to be characterized of the optical waveguide is imprinted onto the polymer characterization surface of the polymer, include:

[0040] A UV-curable resin solution containing UV-curable resin is obtained, and the UV-curable resin solution is spin-coated onto an optical waveguide to be characterized.

[0041] Pressurizing the UV-curable resin solution causes the polymer contact surface between the UV-curable resin solution and the optical waveguide to be characterized to be squeezed and filled by the optical waveguide to be characterized, so as to reverse the characteristic morphology pattern of the optical waveguide to be characterized to the polymer contact surface.

[0042] Irradiate the UV-curable resin solution with UV light until the UV curing agent in the UV-curable resin solution is cured;

[0043] UV-curable resin was peeled off from the optical waveguide to be characterized.

[0044] Preferably, the polymer is placed on a sample stage tilted at 45 degrees, and the needle is dropped onto the polymer characterization surface;

[0045] The spatial domain roughness function of the polymer characterization surface was measured using a tapping mode.

[0046] The frequency domain power spectral density function of the spatial domain roughness is obtained by performing a Fourier transform on the spatial domain roughness function.

[0047] Preferably, the steps of photographing and storing the photonic device pattern on the polymer characterization surface, and analyzing the photonic device pattern to form the second morphology of the optical device integrated on the optical waveguide to be characterized include:

[0048] Gold is sputtered onto the polymer characterization surface to make the polymer characterization surface conductive, so as to observe the morphology of the integrated photonic device pattern formed on the optical waveguide to be characterized.

[0049] The integrated photonic device pattern on the polymer characterization surface is photographed from top to bottom and the photos are stored. The resulting images of the integrated photonic device morphology are then input into an analysis module.

[0050] The second morphology of the integrated photonic device pattern is analyzed in the analysis module.

[0051] Compared with existing technologies, the above technical solution has the following advantages:

[0052] By transferring the micro-nano structure on the optical waveguide onto the polymer, and then using the patterned polymer to characterize the optical waveguide and other devices, this process does not introduce operations such as gold sputtering and etching on the optical waveguide and other devices, nor does it damage the overall structure of the wafer. It can not only achieve rapid large-area characterization, but also perform precise characterization on small parts.

[0053] Since the polymers used in imprinting materials can undergo dry reactive ion etching with the aid of oxygen gas, while materials such as silicon, silicon nitride, and lithium niobate in photonic devices cannot be etched by this method, even if residual polymer remains on the wafer after imprinting, it can be removed using cleaning methods such as dry etching or ultrasonic cleaning with acetone, without affecting subsequent process flows of the waveguide and devices. Attached Figure Description

[0054] Figure 1aThis is a schematic diagram of the spin-coating photoresist process for transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the first embodiment of the present invention.

[0055] Figure 1b This is a schematic diagram of the exposure and development process for transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer, as shown in the first embodiment of the present invention.

[0056] Figure 1c This is a schematic diagram of the etching process for transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the first embodiment of the present invention.

[0057] Figure 1d This is a schematic diagram of the process of transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the first embodiment of the present invention.

[0058] Figure 1e This is a schematic diagram of the hot-pressing polymer process for transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer, as shown in the first embodiment of the present invention.

[0059] Figure 1f This is a schematic diagram of the cooling and curing process for transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer, as shown in the first embodiment of the present invention.

[0060] Figure 1g This is a schematic diagram of the process of transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the first embodiment of the present invention.

[0061] Figure 1h This is a schematic diagram of the polymer acquisition process in the first embodiment of the present invention, which shows the transfer of the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer.

[0062] Figure 2a This is a schematic diagram of the process for obtaining an optical waveguide by transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer, as shown in the second embodiment of the present invention.

[0063] Figure 2b This is a schematic diagram of the drop-coating polymer process for transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the second embodiment of the present invention.

[0064] Figure 2c This is a schematic diagram of the heating and evaporation solvent process for transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer, as shown in the second embodiment of the present invention.

[0065] Figure 2dThis is a schematic diagram of the process of transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the second embodiment of the present invention.

[0066] Figure 2e This is a schematic diagram of the polymer acquisition process in the second embodiment of the present invention, which shows the transfer of the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer.

[0067] Figure 3a This is a schematic diagram of the process for obtaining an optical waveguide by transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer, as shown in the third embodiment of the present invention.

[0068] Figure 3b This is a schematic diagram of the process of transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer in accordance with the third embodiment of the present invention.

[0069] Figure 3c This is a schematic diagram of the imprinting process for transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the third embodiment of the present invention.

[0070] Figure 3d This is a schematic diagram of the ultraviolet light irradiation process for transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer, as shown in the third embodiment of the present invention.

[0071] Figure 3e This is a schematic diagram of the process of transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the third embodiment of the present invention.

[0072] Figure 3f This is a schematic diagram of the thin film acquisition process for transferring the optical waveguide morphology pattern to be characterized onto the polymer characterization surface of the polymer, as shown in the third embodiment of the present invention.

[0073] Figure 4 This is a schematic diagram of the first morphology of the sidewall of the polymer characterization surface in a preferred embodiment of the present invention;

[0074] Figure 5a This is a schematic diagram of the fitting line flow in the first morphology spatial frequency intensity analysis of the sidewall of the polymer characterization surface in a preferred embodiment of the present invention.

[0075] Figure 5b To obtain a roughness function schematic diagram from the first morphology spatial frequency intensity analysis of the sidewall of the polymer characterization surface in a preferred embodiment of the present invention;

[0076] Figure 5c To conform to the schematic diagram of the autocorrelation function obtained by the autocorrelation algorithm in the first morphology spatial frequency intensity analysis of the sidewall of the polymer characterization surface in a preferred embodiment of the present invention;

[0077] Figure 5d To illustrate the power spectral density obtained by Fourier transform in the first morphology spatial frequency intensity analysis of the sidewall of the polymer characterization surface in a preferred embodiment of the present invention;

[0078] Figure 6 This is a schematic flowchart of the optical waveguide topography measurement method of the present invention. Detailed Implementation

[0079] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0080] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0081] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0082] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if," as used herein, can be interpreted as "when," "in response to determination," or "when," or "in the event of a determination."

[0083] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0084] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0085] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0086] See Figure 6 In this invention, the surface of an optical waveguide, especially the shape of its sidewalls, is characterized in an indirect manner, specifically including the following steps:

[0087] S100: Obtain a polymer and place the polymer on an optical waveguide to be characterized. Heat and pressurize the polymer and the optical waveguide to be characterized so that the morphology pattern of the optical waveguide to be characterized is imprinted onto the polymer characterization surface of the polymer.

[0088] A polymer is a long-chain molecule or macromolecule constructed by linking together repeating chemical units. Each molecule of a polymer can consist of hundreds, thousands, or even millions of repeating units, typically including monomers and oligomers. The number of monomers in a polymer chain plays a crucial role in determining its properties. Polyethylene, for example, is derived from ethylene as its basic unit. As the number of monomers in the chain increases, the product changes from a gas to a liquid, and then to a brittle or waxy solid. Monomers are typically held together by covalent bonds, which are characterized by relatively high energy and short distances (0.11–0.16 nm), determining the polymer's mechanical, thermal, chemical, and photochemical properties. In some cases, ionic bonds may also exist in polymers. Polymers can be classified according to their monomers as follows: homopolymers, which are formed using only one monomer (A); copolymers, which use two monomers (A and B) in the polymerization reaction; alternating copolymers, which are copolymers with alternating monomers; random copolymers, which are copolymers with randomly combined monomers; and block copolymers, where monomers are attached in blocks. Polymers can also be classified according to the shape of their chains as follows: linear polymers, which have a main chain resembling a single string—it has no branches but may have some dangling groups, such as polystyrene; branched polymers, which are produced by side reactions during polymerization and consist of branches connected to the main molecular backbone; and network polymers, which, during or after polymerization, produce a network polymer when branches connect with adjacent molecules. Network polymers are also called cross-linked polymers. When exposed to high energy, such as electron beam radiation or gamma rays, sufficient energy can be provided to break some bonds within the polymer. These broken bonds may react with adjacent chains to form a network. As the degree of cross-linking increases, the polymer chains lose their ability to slide against each other, and these cross-linked polymers become more rigid and dimensionally stable. These cross-linked polymers, known as thermosets, are difficult to melt or dissolve, making them challenging to manufacture into products. Thermoset polymers do not flow upon reheating and cannot be reshaped.

[0089] By placing a polymer on an optical waveguide to be characterized, heating and pressurizing both the polymer and the waveguide, the morphological pattern to be characterized in the waveguide is embedded in the polymer's characterization surface. For example, a protrusion in the morphological pattern will appear as a depression on the polymer characterization surface, and vice versa. This achieves the imprinting of the morphological pattern onto the polymer's characterization surface. By then analyzing the roughness of the polymer characterization surface and performing reverse reconstruction, the characterization analysis of the morphological pattern of the optical waveguide to be characterized can be achieved.

[0090] S200: The first morphology of the polymer characterization surface is identified based on scanning electron microscopy, and the spatial frequency intensity of the first morphology is calculated.

[0091] After obtaining the polymer characterization surface, its morphology can be characterized using different types of microscopes (preferably scanning electron microscopes) to obtain a first morphology. By identifying and calculating the first morphology, its spatial frequency intensity, such as flatness, roughness, and height difference, can be obtained. It is understood that although the protrusions in the characterization pattern of the optical waveguide will appear as depressions on the polymer characterization surface, the corresponding results are the same when analyzing the relative relationships of flatness, roughness, or height difference. Therefore, the spatial frequency intensity of the polymer characterization surface represents the spatial frequency intensity of the characterization pattern of the optical waveguide.

[0092] S300: Capture and store the photonic device pattern on the polymer characterization surface, and analyze the photonic device pattern to form the second morphology of the optical device integrated on the optical waveguide to be characterized.

[0093] After obtaining the surface features of the sidewall of the optical waveguide as the first morphology, the photonic device pattern integrated on it can be analyzed. That is, the photonic device pattern on the polymer characterization surface is photographed and stored, and the photonic device pattern is analyzed to form the second morphology of the optical device integrated on the optical waveguide to be characterized. Thus, the surface features of the entire optical waveguide can be obtained, including the surface roughness at non-planar locations and the photonic device features integrated at planar locations.

[0094] See Figures 1a-1h To conform to the flowchart of the transfer of the optical waveguide morphology pattern to the polymer characterization surface in the first embodiment of the present invention, based on the thermoforming technique, the optical waveguide pattern is transferred onto a thermoplastic polymer (such as a cyclic olefin copolymer COC film) under the characteristic of deformation caused by applying pressure at high temperature, thereby patterning the polymer. That is, the thermoplastic polymer is pressed at high temperature (above the glass transition temperature of the polymer), causing the polymer to soften and deform, and then demolded after cooling. In this embodiment, step S100 includes:

[0095] S110: The integrated optical device to be characterized, such as an optical waveguide, is obtained by photolithography and etching. The integrated optical device is used as a template, and a thermoplastic polymer is then obtained and placed on the optical waveguide to be characterized.

[0096] Specifically, see Figure 1a Spin-coating photoresist onto the integrated optical device to be characterized, see [reference]. Figure 1b For the exposure and development of the integrated optical devices to be characterized, refer to [reference needed]. Figure 1c Subsequently, etching is performed to obtain the optical waveguide to be characterized. (See reference...) Figure 1d A thermoplastic polymer is placed on the optical waveguide to be characterized.

[0097] S120: Heating the thermoplastic polymer and the optical waveguide to be characterized until the heating temperature is greater than the glass transition temperature of the thermoplastic polymer, so that the polymer contact surface on the thermoplastic polymer that is in contact with the optical waveguide to be characterized softens.

[0098] Specifically, see Figure 1e Heating of thermoplastic polymer and optical waveguide to be characterized.

[0099] S130: Pressurize the softened thermoplastic polymer to deform the polymer contact surface under the pressure of the optical waveguide to be characterized, so as to reverse the morphological pattern of the optical waveguide to be characterized to the polymer contact surface.

[0100] S140: After the thermoplastic polymer has cured, the thermoplastic polymer is peeled off from the optical waveguide to be characterized.

[0101] See Figure 1f After the thermoplastic polymer cools, allow it to solidify. See [reference needed]. Figure 1g If the thermoplastic polymer is peeled off from the optical waveguide to be characterized, then as follows: Figure 1h As shown, a thermoplastic polymer with an optical waveguide-like morphological pattern to be characterized was obtained.

[0102] Preferably, in the above embodiments, the heating temperature is 50℃-200℃, which softens the thermoplastic polymer, and the pressure applied is 0.5-2MPa; and when the thermoplastic polymer is pressurized, the pressure is kept constant, and the heating temperature is gradually reduced until the thermoplastic polymer cools and solidifies; wherein, the thermoplastic polymer is any one of cyclic olefin copolymer COC film, polymethyl methacrylate, polyethylene terephthalate, or polycarbonate.

[0103] See Figures 2a-2e To conform to the schematic diagram of the process of transferring the optical waveguide morphology pattern to the polymer characterization surface of the polymer in the second embodiment of the present invention, based on soft imprinting technology, the pattern transfer can be achieved by contacting the template under lower pressure by utilizing the solvent evaporation property of flexible polymers (such as polydimethylsiloxane PDMS) at higher temperatures. In this embodiment, step S100 includes:

[0104] S110': See also Figure 2a Photolithography and etching yield the integrated optical device to be characterized, such as an optical waveguide. This integrated optical device is then used as a template, as detailed later. Figure 2b A flexible polymer solution was obtained and then drop-coated onto an optical waveguide to be characterized.

[0105] S120': See Figure 2cThe flexible polymer solution and the optical waveguide to be characterized are heated (for example, the curing temperature is 40℃-90℃, preferably 60℃) until the solvent in the flexible polymer solution evaporates, so that the flexible polymer in the flexible polymer solution is cured on the optical waveguide to be characterized.

[0106] S130': See also Figure 2d and Figure 2e Flexible polymer was peeled off from the optical waveguide to be characterized.

[0107] Preferably, in the above embodiments, the flexible polymer solution is polydimethylsiloxane (PDMS), and the solvent in the solution is propylene glycol methyl ether acetate.

[0108] See Figures 3a-3f To conform to the flowchart of the transfer of the optical waveguide morphology pattern to be characterized onto the polymer characterization surface in the third embodiment of the present invention, based on ultraviolet imprinting technology, the characteristic of cross-linking and curing of liquid photocurable resist under ultraviolet light irradiation is utilized to pattern the polymer, and finally demolding is performed. In this embodiment, step S100 includes:

[0109] S110'': See also Figure 3a Photolithography and etching yield the integrated optical device to be characterized, such as an optical waveguide. This integrated optical device is then used as a template, as detailed later. Figure 3d A UV-curable resin solution containing UV-curable resin was obtained, and the UV-curable resin solution was spin-coated onto an optical waveguide to be characterized.

[0110] S120'': See also Figure 3c Pressurize the UV-curable resin solution so that the polymer contact surface between the UV-curable resin solution and the optical waveguide to be characterized is squeezed and filled by the optical waveguide to be characterized, so as to reverse the morphological pattern of the optical waveguide to be characterized to the polymer contact surface.

[0111] S130'': See also Figure 3d The UV-curable resin solution is irradiated with UV light until the UV curing agent in the UV-curable resin solution is cured.

[0112] S140'': See also Figure 3e and Figure 3f UV-cured resin was peeled off from the optical waveguide to be characterized.

[0113] After obtaining the polymer from any of the above embodiments, the analysis of the polymer can also be carried out in various ways. Preferably, in method one, please refer to... Figure 4 This is achieved using a scanning electron microscope; for details, please refer to [link / reference]. Figures 5a-5d Then step S200 includes:

[0114] S210: Gold is sprayed onto the polymer characterization surface to make the polymer characterization surface conductive;

[0115] S220: Take a top-down photograph of the morphology pattern to be characterized on the polymer characterization surface and store it to form a morphology photograph, and convert the morphology photograph into a grayscale image;

[0116] S230: See also Figure 5a To obtain the first morphology, the edge region integrating photonic devices is extracted from the morphological image. For example, based on the original SEM image, the sidewalls are identified using grayscale images, and the difference is calculated based on the fitted straight line.

[0117] S240: See also Figure 5b After fitting the first morphology, the edge difference is calculated to obtain the spatial domain roughness function of the edge region where the photonic device is integrated. , where z is the spatial coordinate axis of the optical waveguide direction, and the edge difference is the height difference between the fitted straight line and the protruding edge in the first morphology;

[0118] S250: See also Figure 5c For the spatial domain roughness function After autocorrelation, we obtain an autocorrelation function. And according to the definition of the autocorrelation function, we get: ,in This is the convolution operator;

[0119] S260: See also Figure 5d For autocorrelation function Fourier transform yields the frequency domain power spectral density function of the spatial roughness of the edge region. ,Right now , For Fourier transform operators, the frequency domain power spectral density function Spatial frequency intensity characterizing the first morphology.

[0120] In the above embodiments, the fitting of the first morphology in step 240 is particularly important. Since the reference plane or reference line cannot be directly determined from the photograph, it is necessary to calculate the fitting line as the reference line from the photograph. Therefore, step S240 includes:

[0121] S241: Take the first, second, third, and fourth sampling points at the non-edge locations within the edge region. These four sampling points can be arbitrarily selected, as long as they do not completely overlap.

[0122] S242: Draw circles outward from the first sampling point, the second sampling point, the third sampling point, and the fourth sampling point respectively, until they are tangent to the edge for the first time. It can be understood that four circles tangent to the edge can be drawn, and the tangent points are recorded as the first tangent point, the second tangent point, the third tangent point, and the fourth tangent point.

[0123] S243: Connect the first tangent point and the first sampling point and extend it to intersect with the other edge at the first intersection point;

[0124] S244: Connect the second tangent point and the second sampling point and extend it to intersect with the other edge at the second intersection point;

[0125] S245: Connect the third tangent point and the third sampling point and extend it to intersect with another edge at the third intersection point;

[0126] S246: Connect the fourth tangent point and the fourth sampling point and extend it to intersect with the other edge at the fourth intersection point;

[0127] It is understandable that, since the edge is tangent to the circle at each tangent point, the line connecting each tangent point and the sampling point should be orthogonal to the edge at the point of tangency. Considering that the roughness is at the nanometer level and the edge tooth shape is relatively limited, the line connecting each intersection point and the sampling point should be basically orthogonal to the edge.

[0128] S247: Construct a first rectangle with the first intersection point, the second intersection point, the first tangent point, and the second tangent point as vertices, and take the intersection point of the diagonals of the first rectangle as the first fitting point;

[0129] S248: Construct a second rectangle with the third intersection point, the fourth intersection point, the third tangent point, and the fourth tangent point as vertices, and take the intersection point of the diagonals of the second rectangle as the second fitting point;

[0130] It is understandable that the first and second fitting points mentioned above are basically the "midpoints of the width" at the edges of the photographs.

[0131] S249: Connect the first fitting point and the second fitting point to form a fitting straight line. Since the first and second fitting points are essentially the "midpoints of the width" at the edges of the captured image, the fitting straight line basically satisfies:

[0132] Basically parallel to the edge;

[0133] The distance between the two sides is almost equal. If the edges are basically smooth, the fitted line is the midline at the two sides.

[0134] Therefore, the fitted straight line is used as the topographic reference. Subsequently, when calculating the specific location of each position and the height difference between adjacent positions, this fitted straight line is used as a reference line or baseline.

[0135] In the preferred method two, which is based on atomic force microscopy, step S200 includes:

[0136] S210': Place the polymer on a sample stage tilted at 45 degrees and drop the needle onto the polymer characterization surface;

[0137] S220': Measure the spatial domain roughness function of the polymer characterization surface using a tapping mode;

[0138] S230': Perform a Fourier transform on the spatial domain roughness function to obtain the frequency domain power spectral density function of the spatial domain roughness.

[0139] Preferably or optionally, step S300, which involves photographing and storing the photonic device pattern on the polymer characterization surface and analyzing the photonic device pattern to form the second morphology of the optical device integrated on the waveguide to be characterized, includes:

[0140] S310: Gold is sputtered onto the polymer characterization surface to make the polymer characterization surface conductive, so as to observe the morphology of the integrated photonic device pattern formed on the optical waveguide to be characterized, i.e., to further analyze the pattern morphology of the photonic device.

[0141] S320: Take a top-down photograph of the integrated photonic device pattern on the polymer characterization surface and store the photograph. Input the resulting integrated photonic device morphology image into an analysis module.

[0142] S330: Analyze the second morphology of the integrated photonic device pattern in the analysis module.

[0143] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for measuring the morphology of optical waveguides based on nanoimprint technology, characterized in that, Includes the following steps: A polymer is obtained and placed on an optical waveguide to be characterized. The polymer and the optical waveguide to be characterized are heated and pressurized so that the topographic pattern of the optical waveguide to be characterized is imprinted onto the polymer characterization surface of the polymer. The first morphology of the polymer characterization surface was identified using scanning electron microscopy, and the spatial frequency intensity of the first morphology was calculated. The photonic device pattern on the polymer characterization surface is photographed and stored, and the photonic device pattern is analyzed to form the second morphology of the optical device integrated on the optical waveguide to be characterized; The step of identifying the first morphology of the polymer characterization surface based on scanning electron microscopy and calculating the spatial frequency intensity of the first morphology includes: The polymer characterization surface is sputter-coated with gold to make the polymer characterization surface conductive; The top-down image of the morphology pattern to be characterized on the polymer characterization surface is captured and stored to form a morphology photograph, and the morphology photograph is converted into a grayscale image. The edge region integrating the photonic device is extracted from the morphology photograph to obtain the first morphology; After fitting the first morphology, the edge difference is calculated to obtain the spatial domain roughness function of the edge region where the photonic device is integrated. , where z is the spatial coordinate axis of the optical waveguide direction, and the edge difference is the height difference between the fitted straight line and the protruding edge in the first morphology; For the spatial domain roughness function After autocorrelation, we obtain an autocorrelation function. And according to the definition of the autocorrelation function, we get: ,in This is the convolution operator; For autocorrelation function Fourier transform yields the frequency domain power spectral density function of the spatial roughness of the edge region. The frequency domain power spectral density function Characterizing the spatial frequency intensity of the first morphology, and fitting the first morphology includes: For the non-edge locations within the edge region, take the first sampling point, the second sampling point, the third sampling point, and the fourth sampling point; Draw circles outward from the first sampling point, the second sampling point, the third sampling point, and the fourth sampling point respectively, until they are tangent to the edge for the first time, and record the tangent points as the first tangent point, the second tangent point, the third tangent point, and the fourth tangent point; Connect the first tangent point and the first sampling point and extend the line to intersect the other edge at the first intersection point; Connect the second tangent point and the second sampling point and extend it to intersect the other edge at the second intersection point; Connect the third tangent point and the third sampling point and extend the line to intersect the other edge at the third intersection point; Connect the fourth tangent point and the fourth sampling point and extend the line to intersect the other edge at the fourth intersection point; A first rectangle is constructed with the first intersection point, the second intersection point, the first tangent point, and the second tangent point as vertices, and the intersection point of the diagonals of the first rectangle is taken as the first fitting point; Construct a second rectangle with the third intersection point, the fourth intersection point, the third tangent point, and the fourth tangent point as vertices, and take the intersection point of the diagonals of the second rectangle as the second fitting point; Connect the first fitting point and the second fitting point to form a fitting straight line, and use the fitting straight line as the topographic reference. The steps of photographing and storing the photonic device pattern on the polymer characterization surface, and analyzing the photonic device pattern to form the second morphology of the optical device integrated on the optical waveguide to be characterized, include: Gold is sputtered onto the polymer characterization surface to make it conductive, so as to observe the morphology of the integrated photonic device pattern formed by the photonic device pattern on the optical waveguide to be characterized. The integrated photonic device pattern on the polymer characterization surface is photographed from top to bottom and the photograph is stored. The resulting integrated photonic device morphology image is then input into an analysis module. The second morphology of the integrated photonic device pattern is analyzed in the analysis module.

2. The method for measuring the morphology of an optical waveguide as described in claim 1, characterized in that, The steps of obtaining a polymer, placing the polymer on an optical waveguide to be characterized, heating and pressurizing the polymer and the optical waveguide to be characterized, so that the topographic pattern of the optical waveguide to be characterized is imprinted onto the polymer characterization surface of the polymer include: A thermoplastic polymer is obtained and placed on an optical waveguide to be characterized; The thermoplastic polymer and the optical waveguide to be characterized are heated until the heating temperature is greater than the glass transition temperature of the thermoplastic polymer, so that the polymer contact surface on the thermoplastic polymer that is in contact with the optical waveguide to be characterized softens. The thermoplastic polymer is pressurized, causing the polymer contact surface to be deformed by the optical waveguide to be characterized, so as to reverse the characteristic morphology pattern of the optical waveguide to be characterized to the polymer contact surface. After the thermoplastic polymer has cured, it is peeled off from the optical waveguide to be characterized.

3. The optical waveguide morphology measurement method as described in claim 2, characterized in that, The heating temperature is 50℃-200℃, and the pressure applied is 0.5-2MPa; Furthermore, when pressurizing the thermoplastic polymer, the pressurization pressure is kept constant, and the heating temperature is gradually reduced until the thermoplastic polymer cools and solidifies. The thermoplastic polymer is any one of cyclic olefin copolymer (COC) film, polymethyl methacrylate, polyethylene terephthalate, or polycarbonate.

4. The optical waveguide topography measurement method as described in claim 1, characterized in that, The steps of obtaining a polymer, placing the polymer on an optical waveguide to be characterized, heating and pressurizing the polymer and the optical waveguide to be characterized, so that the topographic pattern of the optical waveguide to be characterized is imprinted onto the polymer characterization surface of the polymer include: A flexible polymer solution is obtained and drop-coated onto an optical waveguide to be characterized. The flexible polymer solution and the optical waveguide to be characterized are heated until the solvent in the flexible polymer solution evaporates, thereby solidifying the flexible polymer in the flexible polymer solution onto the optical waveguide to be characterized. The flexible polymer is peeled off from the optical waveguide to be characterized.

5. The optical waveguide morphology measurement method as described in claim 4, characterized in that, The flexible polymer solution is polydimethylsiloxane (PDMS), and the solvent in the flexible polymer solution is propylene glycol methyl ether acetate.

6. The method for measuring the morphology of an optical waveguide as described in claim 1, characterized in that, The steps of obtaining a polymer, placing the polymer on an optical waveguide to be characterized, heating and pressurizing the polymer and the optical waveguide to be characterized, so that the topographic pattern of the optical waveguide to be characterized is imprinted onto the polymer characterization surface of the polymer include: A UV-curable resin solution containing a UV-curable resin is obtained, and the UV-curable resin solution is spin-coated onto an optical waveguide to be characterized. Pressurizing the UV-curable resin solution causes the polymer contact surface between the UV-curable resin solution and the optical waveguide to be characterized to be squeezed and filled by the optical waveguide to be characterized, so as to reverse the characteristic morphology pattern of the optical waveguide to be characterized to the polymer contact surface. The UV-curable resin solution is irradiated with UV light until the UV curing agent in the UV-curable resin solution is cured; The UV-curable resin is peeled off from the optical waveguide to be characterized.

7. The method for measuring the morphology of an optical waveguide as described in any one of claims 1-6, characterized in that, The polymer is placed on a sample stage tilted at 45 degrees, and a needle is dropped onto the polymer characterization surface; The spatial domain roughness function of the polymer characterization surface was measured using a tapping mode. The frequency domain power spectral density function of the spatial domain roughness is obtained by performing a Fourier transform on the spatial domain roughness function.

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