WO2022244274A1 - Manufacturing method for optical waveguide element - Google Patents

Manufacturing method for optical waveguide element Download PDF

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Publication number
WO2022244274A1
WO2022244274A1 PCT/JP2021/019476 JP2021019476W WO2022244274A1 WO 2022244274 A1 WO2022244274 A1 WO 2022244274A1 JP 2021019476 W JP2021019476 W JP 2021019476W WO 2022244274 A1 WO2022244274 A1 WO 2022244274A1
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optical waveguide
substrate
optical
core layer
height
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PCT/JP2021/019476
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French (fr)
Japanese (ja)
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飛鳥 井上
啓 渡邉
慶太 山口
雅 太田
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日本電信電話株式会社
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Priority to JP2023522194A priority Critical patent/JPWO2022244274A1/ja
Priority to PCT/JP2021/019476 priority patent/WO2022244274A1/en
Publication of WO2022244274A1 publication Critical patent/WO2022244274A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method

Definitions

  • the present disclosure relates to a method for manufacturing an optical waveguide device.
  • optical devices capable of generating and modulating coherent light in the wavelength bands of ultraviolet, visible, near-infrared, and terahertz have been used for wavelength conversion and modulation of optical signals in optical communication systems, optical measurement, and optical processing. It is applied in a wide variety of representative fields. Among them, optical elements utilizing nonlinear optical effects have excellent characteristics in terms of wavelength conversion and electro-optical effects, and are being researched and developed.
  • Oxide-based compound substrates have high second-order nonlinear optical constants and high electro-optic constants, and are transparent in a wide wavelength band, and thus are being researched and developed as promising materials.
  • LN and LT periodically poled lithium niobate (Periodically Poled LN: PPLN) and periodically poled lithium niobate (PPLN) having a periodically poled structure formed by taking advantage of the property of being spontaneously polarized at room temperature Lithium tantalate (Periodically Poled LN: PPLT) is widely used.
  • the optical materials described above have a periodically poled structure, so that they have a high phase matching property and, as a result, a high second-order nonlinear optical effect and the like, and are therefore widely used.
  • Second harmonic generation (SHG), difference frequency generation (DFG), and sum frequency generation (SFG) are used as optical devices using high nonlinearity of PPLN and PPLT. Utilizing wavelength conversion elements are known.
  • diffused optical waveguides called titanium diffused optical waveguides and proton exchange optical waveguides were the mainstream.
  • LN is a difficult-to-work material, and therefore it has been difficult to fabricate anything other than a diffused optical waveguide.
  • this diffused optical waveguide has problems from the viewpoint of optical damage resistance and long-term reliability because impurities are diffused in order to form the optical waveguide at the time of fabrication, causing a difference in refractive index.
  • the diffusion type optical waveguide structure when high-power light enters the optical waveguide, the crystal structure is damaged due to the photorefractive effect, so there is a limit to the optical power that can be input to the optical waveguide.
  • Non-Patent Document 1 As one of the methods for solving this problem, research and development are being conducted on ridge-type optical waveguides (see Non-Patent Document 1).
  • the use of a ridge-type optical waveguide forming method by direct bonding enables high-power optical input, and is expected to expand the application to the generation of optical modulation signals with high optical intensity and laser processing technology.
  • the present disclosure has been made in view of such problems, and an object thereof is to provide a method for manufacturing an optical waveguide element, which is a structural target aimed at by an optical waveguide structure to be actually manufactured. be.
  • an optical waveguide device manufacturing method comprises measuring at least one of the height and width of a core of an optical waveguide formed on a substrate. Then, on the condition that the optical characteristics of the optical waveguide are predicted based on the measured structural values, and that the predicted optical characteristics do not become the target optical characteristics, the core of the optical waveguide formed on the substrate Determining a correction amount of at least one of height and width, reprocessing at least one of the height and width of the core of the optical waveguide formed on the substrate according to the determined correction amount, and improving the predicted optical characteristics Dividing the substrate on which the optical waveguide is formed into chips on the condition that the target optical characteristics are achieved.
  • FIG. 1 is a diagram showing a cross-sectional structure of a ridge-type optical waveguide.
  • FIG. 2 is a diagram for explaining a conventional method of manufacturing a chip having a ridge type optical waveguide.
  • FIG. 3 is a diagram illustrating a method of manufacturing a chip having a ridge-type optical waveguide according to one embodiment of the present invention.
  • FIG. 4 is a diagram showing a schematic configuration of a computer for carrying out the method of manufacturing a chip having a ridge-type optical waveguide according to one embodiment of the present invention.
  • a method for manufacturing an optical waveguide element according to one embodiment of the present invention will be described below, taking as an example a ridge-type optical waveguide in which a core layer of nonlinear optical material and an undercladding layer are bonded by direct bonding.
  • the ridge-type optical waveguide included in the device can be, for example, a PPLN optical waveguide.
  • the nonlinear optical material used in this embodiment may be any material as long as it is transparent at light wavelengths of 400 nm to 2000 nm.
  • the nonlinear optical material may be any material as long as it has a nonlinear optical effect, and may be a second-order nonlinear optical effect or a third-order or higher nonlinear optical effect. Examples include lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), beta-barium borite ( ⁇ -BaB 2 O 4 :BBO), potassium titanyl phosphate (KTiOPO 4 :KTP), and the like.
  • the nonlinear optical material may have a periodically poled structure to enhance the nonlinear optical effect. When using a nonlinear optical material having a periodically poled structure, an optical waveguide processing condition below the Curie temperature that does not lose the periodically poled structure, and an optical waveguide structure that can achieve phase matching can be appropriately selected.
  • FIG. 1 is a diagram showing a cross-sectional structure of a ridge-type optical waveguide. As shown in FIG. 1, it has a structure composed of an undercladding layer 1, an overcladding layer 3, and a core layer 2, forming an optical waveguide structure in which light propagates through the core layer 2. As shown in FIG. Since the under-cladding layer 1 and the core layer 2 are directly bonded to each other, they have high resistance to optical damage, so that excitation light with a very high power density can be input into the optical waveguide.
  • the over-cladding layer 3 may be air (air clad), chemical vapor deposition (CVD), flame deposition ( Flame Hydrolysis Deposition: FHD), glass deposited by a sputtering method, or the like may be used as long as it has an over-cladding layer according to the optical waveguide structure design.
  • the core size there are no particular restrictions on the core size, and even if the core diameter is relatively large (10 ⁇ m) or larger for multimode light propagation, it may be small core diameter (10 ⁇ m) or smaller for single mode light propagation. There may be.
  • the shape of the core is not particularly limited, and may be square, rectangular, trapezoidal, or any shape that can be processed.
  • optical waveguide forming method Next, a method for forming an optical waveguide will be described. First, as a comparative example, a conventional method for manufacturing an optical waveguide device will be described with reference to FIG. 2, and then a method for manufacturing an optical waveguide device according to an embodiment of the present invention will be described with reference to FIG.
  • the conventional method for manufacturing an optical waveguide element includes direct bonding in step 1, thinning in step 2, optical waveguide formation in step 3, chip formation in step 4, and optical characteristic evaluation in step 5. .
  • step 1 the substrate 10 of the nonlinear optical material that will be the undercladding layer 1 and the substrate 20 of the nonlinear optical material that will be the core layer 2 are directly bonded.
  • the direct bonding in step 1 leads to an improvement in resistance to light loss when high-intensity light is used as input light by using a direct bonding technique that does not use an adhesive.
  • step 1 the substrate 10 of the undercladding layer 1 and the substrate 20 of the core layer 2 are selected so that their coefficients of thermal expansion are as close as possible, so that cracking of the substrate can be suppressed in the subsequent heat treatment process. become.
  • a substrate formed by directly bonding the substrate 10 and the substrate 20 is also referred to as a bonded substrate.
  • step 2 the nonlinear optical material substrate 20, which will be the core layer 2 of the bonded substrate, is thinned.
  • the method of thinning There are no particular restrictions on the method of thinning, and candidates include a grinding polishing process, a smart cut method, and the like.
  • the core layer 2 of the optical waveguide 40 is formed by processing the substrate 20 .
  • candidates include a dry etching process, cutting out the core layer 2 of the optical waveguide 40 using a dicing saw, and the like.
  • the over-cladding layer 3 of the optical waveguide 40 is formed by a known method as required.
  • step 4 the substrate having the manufactured optical waveguide 40 is chipped to produce an optical waveguide element.
  • a chipping method a method using a dicing saw can be mentioned as a candidate, but there is no particular limitation on the processing method.
  • by optically polishing the end face or coating an anti-reflection film after chipping it is possible to reduce light loss when light enters or exits the chip 50 as an optical waveguide element. .
  • step 5 the chip 50 having the manufactured optical waveguide 40 is evaluated for optical characteristics.
  • the method for manufacturing an optical waveguide element of the present embodiment includes direct bonding in step 1, thinning in step 2, optical waveguide formation in step 3, chip formation in step 4, and optical characteristic evaluation in step 5. and further includes structural measurement in step 31, property prediction in step 32, correction amount determination in step 33, and rework in step 343.
  • the manufacturing method of FIG. 3 is a method incorporating a correction process for the optical waveguide structure.
  • Steps 1 and 2 are the same steps as described with reference to FIG.
  • step 3 the core layer 2 of the optical waveguide 40 is formed by processing the substrate 20 .
  • the method of forming the optical waveguide There are no particular restrictions on the method of forming the optical waveguide, and candidates include a dry etching process, cutting out the optical waveguide using a dicing saw, and the like.
  • no overcladding layer 3 is formed. If the overcladding layer 3 of the optical waveguide 40 is required, it is formed after steps 31 and 32 .
  • step 31 the structure of the fabricated optical waveguide 40 is measured.
  • the distribution of the width W and the height H of the core layer 2 of the optical waveguide 40 with respect to the propagation direction of light can be mentioned as a candidate. This is because the effective refractive index of the optical waveguide 40 is determined by the product of these items, and is the item that ultimately affects the effective refractive index distribution of the optical waveguide 40 in the propagation direction.
  • the width W of the core layer 2 of the optical waveguide 40 can be measured using an optical microscope or a scanning electron microscope (SEM).
  • the height H of the core layer 2 of the optical waveguide 40 that is, the film thickness distribution of the core layer 2
  • the measurement of the height H of the core layer 2 of the optical waveguide 40 in step 31 may be performed after step 2 and before step 3 . In this case, the film thickness distribution of the thinned substrate 20 before the optical waveguide is formed may be measured.
  • step 32 based on the measured values of the structure obtained in step 31 (the distribution of the width W and the height H of the core layer 2 of the optical waveguide 40), the same structure (digital twin of the optical waveguide) is generated on the simulator. to simulate optical properties.
  • the method of simulation at this time can be determined according to the target physical quantity (for example, optical loss, nonlinear optical effect).
  • Typical simulation methods include the beam propagation method (BPM) and the finite difference time domain (FDTD).
  • BPM beam propagation method
  • FDTD finite difference time domain
  • step 32 it is determined whether the optical properties predicted by the simulation are the target properties. If the expected optical characteristics are determined to be the target characteristics, the process proceeds to step 4, which is a chip forming step. to the correction process (trimming process).
  • step 33 the extent to which various structural parameters should be changed is calculated and corrected so that the optical characteristics of the structure (digital twin) on the simulator produced in step 32 can reach the target characteristics. Determine the amount (trimming amount).
  • step 34 correction (trimming) processing is performed on the actual structure based on the correction amount determined in step 33.
  • at least one of the width W and thickness H of the core layer 2 of the optical waveguide 40 can be corrected.
  • a method of correction processing local structural modification using a local etching apparatus is a candidate.
  • step 35 steps 31 to 34 are repeated until the optical waveguide structure exhibits the target characteristics.
  • the structure of the core layer 2 of the optical waveguide 40 finally obtained satisfies the initially set target values.
  • An overcladding layer 3 is deposited as required.
  • the optical waveguide 40 is a ridge-type optical waveguide including an undercladding layer 1 , a core layer 2 and an overcladding layer 3 .
  • Steps 4 and 5 are the same steps as described with reference to FIG.
  • the manufacturing method of the optical waveguide element of the present embodiment (steps 1 to 5 above) is expected to dramatically improve the yield and characteristics compared to the conventional manufacturing method of the optical waveguide element.
  • a direct bonding technique is available as a technique for firmly bonding substrates together without using an adhesive.
  • the direct bonding technique is a method in which the surfaces of the substrates are first treated using a chemical agent, and then the substrates are placed on top of each other to bond the substrates by the attractive force between the surfaces.
  • the surface treatment conditions temperature, type of chemicals, etc.
  • the surface treatment conditions for various substrates can be optimized according to the type and combination of substrates to be actually bonded.
  • the direct bonding process is performed at normal temperature, since the bonding strength at this time is small, heat treatment at a high temperature is performed after that, diffusion bonding can be performed, and the bonding strength can be improved.
  • the bonded substrates are void-free with no inclusion of microparticles or the like on the bonded surfaces, and no cracks or the like occur at room temperature.
  • the technology of direct bonding which can firmly bond substrates without using adhesives, etc., has characteristics such as high optical damage resistance, long-term reliability, and ease of device design.
  • characteristics such as high optical damage resistance, long-term reliability, and ease of device design.
  • difference frequency generation which is a type of nonlinear optical effect, there is also the advantage of avoiding the contamination of impurities and the absorption of adhesives and the like.
  • Method for thinning Techniques for thinning the substrate 20 include a grinding/polishing process, a thinning process using smart cut, and the like.
  • the method of thinning is not particularly limited, and thinning by grinding/polishing or thinning by smart cut may be used.
  • the grinding/polishing process is performed until the optical waveguide exists at an arbitrary depth using a device with a controlled flatness of the surface plate for grinding/polishing.
  • a mirror polished surface optical end face
  • the parallelism of the substrate as a whole can be obtained by measuring the parallelism of the substrate (the difference between the maximum height and the minimum height of the substrate) using an optical parallelism measuring instrument.
  • the thinning process by SmartCut mainly consists of two processes: the ion implantation process and the thin film peeling process.
  • the ion implantation step helium or hydrogen ions are implanted into the substrate 20 which needs to be thinned to have a second-order nonlinear optical effect. Ions are implanted from the substrate surface under a controlled acceleration voltage and a controlled dose, and are trapped at a certain depth from the surface.
  • the ions to be used are desirably smaller than the atoms forming the substrate, such as hydrogen and helium.
  • the substrate peeling process the above-described substrate into which ions are implanted is subjected to heat treatment, thereby peeling the substrate along the damaged layer in the substrate.
  • the heat treatment temperature in the substrate peeling step should be lower than the Curie temperature of the secondary nonlinear optical crystal so as not to disturb the patterned polarization direction.
  • the core layer thinned by the above method has an in-plane film thickness distribution due to its processing accuracy.
  • the thinning process by grinding and polishing which can produce a ridge-type optical waveguide 40 having a relatively large core layer 2 with high optical damage resistance, there is a relatively large processing limit in suppressing the film thickness distribution. It is difficult to fabricate an optical waveguide having a final target structure due to the film thickness distribution that exists due to these processing accuracy limits.
  • Methods for forming the core layer 2 of the ridge-type optical waveguide 40 include a method using a dry etching process and a method using a mechanical process represented by a dicing saw.
  • the method of forming the core layer 2 of the ridge-type optical waveguide 40 is not particularly limited, and may be a method using dry etching, a method using a dicing saw, or any other forming method. good.
  • the core layer 2 of the optical waveguide 40 is formed by etching the surface of the substrate 20 to be the core layer 2 (hereinafter referred to as the core substrate surface) using a dry etching apparatus. At this time, the pattern of the optical waveguide 40 is formed on the surface of the core substrate by a normal photolithography process.
  • the core layer 2 of the optical waveguide 40 is formed by dry etching with a dry etching apparatus using the resist of the optical waveguide pattern as a mask. In this method, the width of the optical waveguide is distributed due to the following two causes.
  • the first cause is the manufacturing error of the optical waveguide pattern created by the photolithography process.
  • This process it is possible to suppress the optical waveguide width distribution by optimizing the photolithography conditions, but it is difficult to produce a resist pattern in which the optical waveguide width distribution does not occur completely.
  • the second cause is the in-plane etching amount distribution during dry etching.
  • the dry etching process it is difficult to completely eliminate the in-plane distribution of the etching amount that affects the width of the optical waveguide 40 that is finally formed.
  • the reasons for this are that, for example, in the case of a nonlinear optical substrate having a periodically poled structure, the etching rate varies slightly depending on the polarization direction, the temperature distribution occurs in the substrate surface during the process, and the etching rate varies depending on the substrate temperature.
  • the density of plasma during etching does not always have a uniform distribution within the plane.
  • a method using machining represented by a dicing saw is a method of forming the core layer 2 of the optical waveguide 40 by using a dicing blade used in a normal dicing process.
  • the accuracy of the structure of the optical waveguide 40 to be fabricated is determined mainly by the accuracy of the machine used for processing, particularly the positional accuracy of the stage and processing section for fixing the sample. For this reason, there is a limit to the accuracy of manufacturing the core layer 2 of the optical waveguide 40, and it is difficult to manufacture an optical waveguide having an optical waveguide width exactly as designed.
  • step 5 optical characteristics are evaluated in step 5 after chipping in step 4.
  • the "characteristic" in step 5 is an index value representing the function and performance of the optical waveguide, such as second-order nonlinear optical constant and light transmittance in the case of a nonlinear optical element.
  • a target optical characteristic value is set, and the structure of the optical waveguide is designed to achieve it. Then, aiming at the target structure, the process moves to the optical waveguide processing step.
  • the structure of the optical waveguide 40 obtained deviates from the target structure. This is due to manufacturing errors in each process.
  • the optical waveguide 40 obtained through steps 1 to 3 is chipped by dicing or the like, optical end faces are formed, and the chip 50 having the optical waveguide 40 is completed.
  • the characteristics of the optical waveguide 40 are known for the first time by inspecting the completed chip 50 .
  • the characteristics of the optical waveguide are not known until it is chipped and inspected. There is the problem of producing chips that do not provide structures with the desired characteristics.
  • target optical characteristic values are set, and the structure of the optical waveguide is designed to achieve them. Then, aiming at the target structure, the process moves to the optical waveguide processing step. In an actual processing step, the structure of the optical waveguide 40 obtained deviates from the target structure. This is due to manufacturing errors in each process, and the process up to this process is the same as the conventional method of manufacturing an optical waveguide element.
  • the same structure is formed on a simulator based on structural information obtained by measuring various structural values represented by the height H and width W of the core layer 2 of the fabricated optical waveguide 40. Then, the optical characteristics are predicted using various simulation techniques.
  • the optical waveguide produced on the simulator at this time is a digital twin of the optical waveguide 40 actually produced, and it is possible to predict characteristic values non-destructively on the simulator. A pass/fail judgment is made as to whether or not the characteristic values obtained on the simulator have reached the initially set target values (judgment as to whether or not the initially set target values are met). If the predicted characteristics are acceptable, the over-cladding layer 3 is formed as necessary, and then the process proceeds to chip formation.
  • the process moves to the correction process (trimming process) for the structure of the core layer 2.
  • the structural correction amount in the correction process is calculated on the simulator, the correction amount is reflected in the structure on the simulator, and the calculation is performed until the obtained optical characteristics exceed the acceptance criteria. Then, based on the obtained correction amount, reprocessing (trimming) of the core layer 2 of the actual optical waveguide 40 is performed.
  • This reprocessing method may be any method as long as it has a processing accuracy that allows reprocessing of the correction amount obtained on the simulator, and in this embodiment, local etching that performs dry etching locally is a candidate. technology.
  • the structural values of the core layer 2 are measured again, the digital twin is reproduced on the simulator, and the optical properties are predicted.
  • the optical characteristics such as the effective refractive index (equivalent refractive index) and propagation characteristics of the optical waveguide 40 are basically determined by the width and height of the core layer and the refractive index of the core. , and the refractive index of the cladding.
  • Correction of the optical characteristics by correcting the width W of the core layer can also be performed by correcting the height of the core layer. Therefore, by correcting one or both of the width and height of the core layer of the optical waveguide, the optical characteristics of the optical waveguide can be corrected. Therefore, the structural correction amount calculated on the simulator can indicate the correction amount for one or both of the width W and height H of the core layer 2 of the optical waveguide 40 formed on the bonded substrate.
  • the distribution (film thickness distribution) of the height H of the core layer 2 of the optical waveguide 40 is measured using optical interference.
  • light is incident on the surface of the substrate 20 serving as the core layer 2, and non-contact evaluation of the film thickness of the multilayer film can be performed by light reflection spectrum analysis.
  • the method of analyzing the film thickness by using interference with reflected light is a widely used method, and the film thickness is measured using the widely used optical interference method also in this embodiment. Even if the film thickness is measured for the entire substrate surface after step 2, which is before the optical waveguide is formed in step 3, the core layer 2 of the optical waveguide 40 is measured in step 4 after the optical waveguide is formed in step 3. Any of the methods of measuring for only may be used.
  • the film thickness measurement method in this embodiment may be a method other than the method using optical interference, and any method may be used as long as it is non-invasive to the optical waveguide structure.
  • the distribution of the width W of the core layer 2 of the optical waveguide 40 is measured by directly observing the core layer 2 of the optical waveguide 40 .
  • Any specific observation method may be used as long as it is non-invasive to the optical waveguide structure, and representative examples include a method using an optical microscope and a method using an electron microscope such as a scanning electron microscope.
  • a method using a step meter or a high-precision measurement method using an atomic force microscope may be used.
  • the interval between measurement points when measuring the distribution of the width W of the core layer 2 of the optical waveguide there is no particular limitation on the interval between measurement points when measuring the distribution of the width W of the core layer 2 of the optical waveguide, and the number of measurement points is such that necessary and sufficient structural information can be obtained in the trimming process of the structure, and Any number of measurement points may be used as long as the throughput of the optical waveguide forming process does not significantly decrease.
  • a simulator In the method for manufacturing an optical waveguide element of the present embodiment, a simulator is used to simulate the same structure as the core layer 2 of the actually manufactured optical waveguide 40, and the optical characteristics of the simulated structure are predicted. A pass/fail decision is made by testing whether the property has the initial target property. If the optical properties of the simulated structure do not meet the target values, in step 33, the degree to which the structure of the core layer 2 should be corrected to obtain the target optical properties is calculated on the simulator. Then, in step 34, the structure of the core layer 2 of the optical waveguide 40 actually manufactured is corrected using the amount of correction obtained in step 33.
  • a local etching method capable of locally processing only a target range with high accuracy is used. It can be either. Then, structural values such as the height H and the width W of the core layer 2 of the optical waveguide 40 are similarly measured for the structure after processing. Using the obtained post-processing structural values, the structure of the core of the optical waveguide is recreated on the simulator so as to be a digital twin of the structure of the core layer 2 of the actual optical waveguide 40, and the optical characteristics are predicted. A pass/fail judgment is made by performing an inspection on a simulator to see if the optical properties obtained initially have the target properties.
  • a series of steps of structural measurement in step 31, property prediction in step 32, correction amount determination in step 33, reprocessing in step 34, structural measurement in step 31, and property prediction in step 32 are initially set with the expected optical properties. It is possible to form an optical waveguide having the target characteristics by repeating the process until the desired characteristics are obtained.
  • FIG. 4 is a diagram showing a schematic configuration of a computer 100 that constitutes a simulator that can be used in the method for manufacturing an optical waveguide device according to this embodiment.
  • Computer 100 has processor 101 , memory 102 , input device 103 , output device 104 , communication device 105 and storage 106 .
  • the processor 101 can be, for example, a CPU (Central Processing Unit), a microprocessor implemented in an integrated circuit (IC), or an MPU (Micro-Processing Unit), or other processor.
  • the processor 101 can function as a measurement data processing unit 132 and a control data processing unit 133 by loading a program stored in the storage 106 into the memory 102 and executing the program.
  • Memory 102 may be, for example, RAM (Random Access Memory) or ROM (Read Only Memory).
  • Input device 103 may be, for example, a keyboard, mouse, camera, or sensor.
  • Output device 104 may be, for example, a display device or a printer.
  • Communication device 105 may be, for example, a wireless communication device or a wired communication device.
  • Storage 106 may be, for example, a hard disk drive (HDD) or solid state drive (SSD).
  • HDD hard disk drive
  • SSD solid state drive
  • the computer 100 includes a measurement data processing unit 132 and a control data processing unit 133 that execute the functions of the simulator described above.
  • the measurement data processing unit 132 executes characteristic prediction in step 32 described with reference to FIG. 3, and the control data processing unit 133 executes correction amount determination (trimming amount determination) in step 33 described with reference to FIG. .
  • the solid line indicates the flow of the product according to the process.
  • the dashed line indicates measurement data obtained by structural measurement in step 31, and the one-dot chain line indicates correction amount (trimming amount) data for "control" in step 34, respectively.
  • the predicted value derived by the measurement data processing unit 132 is passed to the control data processing unit 133.
  • the control data processing unit 133 determines the correction amount (trimming amount) in step 34, which is the post-process, based on the predicted value.
  • the control data processing unit 133 supplies the correction amount data of the process 34 to be set in the manufacturing apparatus according to the obtained correction amount when the process 34 is performed.
  • the optical waveguide structure actually manufactured due to the processing accuracy limits of various processes in the conventional method for manufacturing an optical waveguide element is the target structure. It is possible to solve the problem that the target characteristics cannot be obtained due to deviation from the
  • the step of predicting the optical characteristics of the optical waveguide based on the measured structural values of the structure of the optical waveguide formed on the substrate and correcting the structure of the optical waveguide is performed.

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Abstract

The present disclosure provides a manufacturing method for an optical waveguide element. The manufacturing method according to the present disclosure comprises: measuring a structure value of the height and/or width of a core layer of an optical waveguide formed on a substrate (step 31); and predicting optical characteristics of the optical waveguide on the basis of the measured structure value (step 32). This manufacturing method comprises: determining a correction amount of the height and/or width of the core layer of the optical waveguide formed on the substrate, on a condition that the predicted optical characteristics do not meet target optical characteristics (step 33); reprocessing the height and/or width of the core layer in accordance with the determined correction amount (step 34); and forming, into a chip, the substrate on which the optical waveguide is formed, on a condition that the predicted optical characteristics meet the target optical characteristics (step 4).

Description

光導波路素子の製造方法Method for manufacturing optical waveguide device
　本開示は、光導波路素子の製造方法に関する。 The present disclosure relates to a method for manufacturing an optical waveguide device.
　従来、紫外～可視～近赤外～テラヘルツの波長帯域においてコヒーレント光の発生や変調をすることが可能な光学素子は、光通信システムにおける光信号の波長変換や光変調、光計測、光加工に代表される多岐にわたる分野において応用されている。なかでも非線形光学効果を利用する光学素子は、波長変換や電気光学効果において優れた特性を有することから、研究開発が進められている。 Conventionally, optical devices capable of generating and modulating coherent light in the wavelength bands of ultraviolet, visible, near-infrared, and terahertz have been used for wavelength conversion and modulation of optical signals in optical communication systems, optical measurement, and optical processing. It is applied in a wide variety of representative fields. Among them, optical elements utilizing nonlinear optical effects have excellent characteristics in terms of wavelength conversion and electro-optical effects, and are being researched and developed.
　非線形光学効果および電気光学効果を有する光学材料として、様々な種類の材料が開発されているが、なかでもニオブ酸リチウム（ＬｉＮｂＯ３：ＬＮ）やタンタル酸リチウム（ＬｉＴａＯ３：ＬＴ）等に代表される酸化物系化合物基板は、高い二次非線形光学定数、高い電気光学定数を有し、広い波長帯域において透明であることから有望な材料として研究開発されている。ＬＮやＬＴの中でも、室温で自発分極することが可能な特性を生かして形成される、周期的に分極反転された構造を有する周期分極反転ニオブ酸リチウム（Ｐｅｒｉｏｄｉｃａｌｌｙ　Ｐｏｌｅｄ　ＬＮ：ＰＰＬＮ）や周期分極反転タンタル酸リチウム（Ｐｅｒｉｏｄｉｃａｌｌｙ　Ｐｏｌｅｄ　ＬＮ：ＰＰＬＴ）が広く用いられている。上記の光学材料は周期分極反転構造を有することにより、高い位相整合性を有し結果として高い二次非線形光学効果等を有することから、広く用いられている。ＰＰＬＮ、ＰＰＬＴの高い非線形性を用いた光デバイスとして、第二次高調波発生（Ｓｅｃｏｎｄ　ｈａｒｍｏｎｉｃ　ｇｅｎｅｒａｔｉｏｎ：ＳＨＧ）、差周波発生（Ｄｉｆｆｅｒｅｎｃｅ　Ｆｒｅｑｕｅｎｃｙ　Ｇｅｎｅｒａｔｉｏｎ：ＤＦＧ）、和周波発生（Ｓｕｍ　Ｆｒｅｑｕｅｎｃｙ　Ｇｅｎｅｒａｔｉｏｎ：ＳＦＧ）を利用した波長変換素子が知られている。 Various kinds of materials have been developed as optical materials having a nonlinear optical effect and an electrooptic effect. Oxide-based compound substrates have high second-order nonlinear optical constants and high electro-optic constants, and are transparent in a wide wavelength band, and thus are being researched and developed as promising materials. Among LN and LT, periodically poled lithium niobate (Periodically Poled LN: PPLN) and periodically poled lithium niobate (PPLN) having a periodically poled structure formed by taking advantage of the property of being spontaneously polarized at room temperature Lithium tantalate (Periodically Poled LN: PPLT) is widely used. The optical materials described above have a periodically poled structure, so that they have a high phase matching property and, as a result, a high second-order nonlinear optical effect and the like, and are therefore widely used. Second harmonic generation (SHG), difference frequency generation (DFG), and sum frequency generation (SFG) are used as optical devices using high nonlinearity of PPLN and PPLT. Utilizing wavelength conversion elements are known.
　ＰＰＬＮを用いた光導波路構造として、チタン拡散光導波路、プロトン交換光導波路と呼ばれる拡散型の光導波路が主流であった。これは、ＬＮは難加工性材料であるがゆえ拡散型光導波路以外の作製が困難であったことに因る。しかしながらこの拡散型光導波路は、作製時に光導波路を形成するため不純物を拡散させ、屈折率差を生じさせることから、光損傷耐性や長期信頼性の観点から課題があった。拡散型の光導波路構造では、高いパワーの光を光導波路に入射すると、フォトリフラクティブ効果により結晶構造が損傷してしまうため、光導波路に入力できる光パワーに制限があった。 As optical waveguide structures using PPLN, diffused optical waveguides called titanium diffused optical waveguides and proton exchange optical waveguides were the mainstream. This is because LN is a difficult-to-work material, and therefore it has been difficult to fabricate anything other than a diffused optical waveguide. However, this diffused optical waveguide has problems from the viewpoint of optical damage resistance and long-term reliability because impurities are diffused in order to form the optical waveguide at the time of fabrication, causing a difference in refractive index. In the diffusion type optical waveguide structure, when high-power light enters the optical waveguide, the crystal structure is damaged due to the photorefractive effect, so there is a limit to the optical power that can be input to the optical waveguide.
　この課題の解決手法の一つとして、リッジ型の光導波路についての研究開発がなされている（非特許文献１参照）。特に直接接合法によるリッジ型光導波路形成手法を用いると、高パワーの光入力が可能になり、高光強度の光変調信号の生成やレーザー加工技術等への応用が広がると予想されている。 As one of the methods for solving this problem, research and development are being conducted on ridge-type optical waveguides (see Non-Patent Document 1). In particular, the use of a ridge-type optical waveguide forming method by direct bonding enables high-power optical input, and is expected to expand the application to the generation of optical modulation signals with high optical intensity and laser processing technology.
　しかしながら、直接接合法によるリッジ型光導波路形成手法における各種プロセスの加工精度限界により実際に作製される光導波路構造は目標とする構造から逸脱してしまい、目標とする特性が得られないという課題があった。 However, there is a problem that the optical waveguide structure actually manufactured deviates from the target structure due to the processing accuracy limit of various processes in the ridge type optical waveguide formation method by the direct bonding method, and the target characteristics cannot be obtained. there were.
　本開示は、このような問題に鑑みてなされたもので、その目的とするところは、実際に作製される光導波路構造が目標とする構造目標である光導波路素子の製造方法を提供することにある。 The present disclosure has been made in view of such problems, and an object thereof is to provide a method for manufacturing an optical waveguide element, which is a structural target aimed at by an optical waveguide structure to be actually manufactured. be.
　このような目的を達成するために、本発明の一実施形態にかかる光導波路素子の製造方法は、基板に形成された光導波路のコアの高さ及び幅の少なくとも一方の構造値を計測することと、計測された構造値に基づいて、光導波路の光学特性の予測することと、予測された光学特性が目標とする光学特性とならないことを条件に、基板に形成された光導波路のコアの高さ及び幅の少なくとも一方の補正量を決定し、決定した補正量に従って、基板に形成された光導波路のコアの高さ及び幅の少なくとも一方を再加工することと、予測された光学特性が目標とする光学特性となることを条件に、光導波路が形成された基板をチップ化することとを備える。 In order to achieve these objects, an optical waveguide device manufacturing method according to an embodiment of the present invention comprises measuring at least one of the height and width of a core of an optical waveguide formed on a substrate. Then, on the condition that the optical characteristics of the optical waveguide are predicted based on the measured structural values, and that the predicted optical characteristics do not become the target optical characteristics, the core of the optical waveguide formed on the substrate Determining a correction amount of at least one of height and width, reprocessing at least one of the height and width of the core of the optical waveguide formed on the substrate according to the determined correction amount, and improving the predicted optical characteristics Dividing the substrate on which the optical waveguide is formed into chips on the condition that the target optical characteristics are achieved.
図１は、リッジ型の光導波路の断面構造を示す図である。FIG. 1 is a diagram showing a cross-sectional structure of a ridge-type optical waveguide. 図２は、従来のリッジ型の光導波路を有するチップの製造方法を説明する図である。FIG. 2 is a diagram for explaining a conventional method of manufacturing a chip having a ridge type optical waveguide. 図３は、本発明の一実施形態のリッジ型の光導波路を有するチップの製造方法を説明する図である。FIG. 3 is a diagram illustrating a method of manufacturing a chip having a ridge-type optical waveguide according to one embodiment of the present invention. 図４は、本実施形態の一実施形態のリッジ型の光導波路を有するチップの製造方法を実施するための計算機の概略構成を示す図である。FIG. 4 is a diagram showing a schematic configuration of a computer for carrying out the method of manufacturing a chip having a ridge-type optical waveguide according to one embodiment of the present invention.
　以下、図面を参照しながら本発明の実施形態について詳細に説明する。同一または類似の参照符号は、同一または類似の要素を示し、繰り返しの説明を書略する場合がある。以下の説明中の材料および数値は、例示であり、本館発明の技術的範囲を限定することを意図しない。以下に説明する実施形態は、本願発明の要旨を逸脱しない範囲において、他の材料および数値を用いて実施してもよい。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Identical or similar reference numerals indicate identical or similar elements and may abbreviate repeated descriptions. Materials and numerical values in the following description are examples and are not intended to limit the technical scope of the present invention. The embodiments described below may be implemented using other materials and numerical values without departing from the gist of the present invention.
　以下、直接接合により非線形光学材料のコア層とアンダークラッド層とが接合されたリッジ型の光導波路を例として、本発明の一実施形態の光導波路素子の製造方法を説明する。素子に含まれるリッジ型の光導波路は、例えば、ＰＰＬＮ光導波路とし得る。 A method for manufacturing an optical waveguide element according to one embodiment of the present invention will be described below, taking as an example a ridge-type optical waveguide in which a core layer of nonlinear optical material and an undercladding layer are bonded by direct bonding. The ridge-type optical waveguide included in the device can be, for example, a PPLN optical waveguide.
（非線形光学材料の選定）
　本実施形態で用いる非線形光学材料は、光波長４００ｎｍ～２０００ｎｍにおいて透明である材料であればいずれの材料でもよい。非線形光学材料は、非線形光学効果を有する材料であればいずれの材料でもよく、二次非線形光学効果であっても三次以上の非線形光学効果であってもよい。例として、ニオブ酸リチウム（ＬｉＮｂＯ３）、タンタル酸リチウム（ＬｉＴａＯ３）、ベータバリウムボライト（β－ＢａＢ２Ｏ４：ＢＢＯ）、リン酸チタニルカリウム（ＫＴｉＯＰＯ4：ＫＴＰ）等があげられる。非線形光学材料は、非線形光学効果増大のために周期分極反転構造を有するものであってもよい。周期分極反転構造を有する非線形光学材料を用いる際は、周期分極反転が失われないキュリー温度以下の光導波路加工条件や、位相整合をとることができる光導波路構造を適宜選択し得る。 (Selection of nonlinear optical material)
The nonlinear optical material used in this embodiment may be any material as long as it is transparent at light wavelengths of 400 nm to 2000 nm. The nonlinear optical material may be any material as long as it has a nonlinear optical effect, and may be a second-order nonlinear optical effect or a third-order or higher nonlinear optical effect. Examples include lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), beta-barium borite (β-BaB 2 O 4 :BBO), potassium titanyl phosphate (KTiOPO 4 :KTP), and the like. The nonlinear optical material may have a periodically poled structure to enhance the nonlinear optical effect. When using a nonlinear optical material having a periodically poled structure, an optical waveguide processing condition below the Curie temperature that does not lose the periodically poled structure, and an optical waveguide structure that can achieve phase matching can be appropriately selected.
（光導波路の構造）
　図１は、リッジ型の光導波路の断面構造を示す図である。図１に示すように、アンダークラッド層１、オーバークラッド層３、コア層２から構成される構造をとり、コア層２内部を光が伝搬する光導波路構造となっている。アンダークラッド層１とコア層２は直接接合により接合されることにより、高い光損傷耐性を有するため、光導波路内部にパワー密度の非常に高い励起光を入力することが可能となる。また、オーバークラッド層３の屈折率に関しては特に制限はなく、オーバークラッド層３は、空気(エアークラッド)であってもよく、化学気相成長法(Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒ　Ｄｅｐｏｓｉｔｉｏｎ：ＣＶＤ)や火炎堆積法（Ｆｌａｍｅ Ｈｙｄｒｏｌｙｓｉｓ Ｄｅｐｏｓｉｔｉｏｎ：ＦＨＤ）、スパッタリング法により堆積されたガラス等であってもよく、光導波路構造設計に応じたオーバークラッド層を有していればいずれでもよい。 (Structure of optical waveguide)
FIG. 1 is a diagram showing a cross-sectional structure of a ridge-type optical waveguide. As shown in FIG. 1, it has a structure composed of an undercladding layer 1, an overcladding layer 3, and a core layer 2, forming an optical waveguide structure in which light propagates through the core layer 2. As shown in FIG. Since the under-cladding layer 1 and the core layer 2 are directly bonded to each other, they have high resistance to optical damage, so that excitation light with a very high power density can be input into the optical waveguide. Moreover, there is no particular limitation on the refractive index of the over-cladding layer 3, and the over-cladding layer 3 may be air (air clad), chemical vapor deposition (CVD), flame deposition ( Flame Hydrolysis Deposition: FHD), glass deposited by a sputtering method, or the like may be used as long as it has an over-cladding layer according to the optical waveguide structure design.
　またコアサイズに関しても特に制限はなく、マルチモードで光が伝搬する比較的大きなコア径（１０μｍ）以上のものであっても、シングルモードで光が伝搬する小コア径（１０μｍ）以下のものであってもよい。コア層２の薄膜化をスマートカット法等にて行い小コア化を試みた光導波路であって、そのコア径が非常に小さなコア径（ｎｍ単位）でもよい。また、コア形状に関しても特に制限はなく、正方形、長方形、台形、その他加工可能な形状であればいずれでもよい。 There are no particular restrictions on the core size, and even if the core diameter is relatively large (10 μm) or larger for multimode light propagation, it may be small core diameter (10 μm) or smaller for single mode light propagation. There may be. An optical waveguide in which a small core is attempted by thinning the core layer 2 by a smart cut method or the like, and the core diameter may be very small (in units of nm). Also, the shape of the core is not particularly limited, and may be square, rectangular, trapezoidal, or any shape that can be processed.
（光導波路形成手法）
　次に光導波路形成手法を説明する。初めに比較例として図２を参照して従来の光導波路素子の製造方法を説明し、次いで図３を参照して本発明の一実施形態の光導波路素子の製造方法を説明する。 (Optical waveguide forming method)
Next, a method for forming an optical waveguide will be described. First, as a comparative example, a conventional method for manufacturing an optical waveguide device will be described with reference to FIG. 2, and then a method for manufacturing an optical waveguide device according to an embodiment of the present invention will be described with reference to FIG.
　図２に示すように従来の光導波路素子の製造方法は、工程１の直接接合、工程２の薄膜化、工程３の光導波路形成、工程４のチップ化、および工程５の光学特性評価を含む。 As shown in FIG. 2, the conventional method for manufacturing an optical waveguide element includes direct bonding in step 1, thinning in step 2, optical waveguide formation in step 3, chip formation in step 4, and optical characteristic evaluation in step 5. .
　工程１において、アンダークラッド層１となる非線形光学材料の基板１０とコア層２となる非線形光学材料の基板２０を直接接合する。工程１における直接接合は、接着剤を用いない直接接合技術を用いることにより、高強度の光を入力光とした場合の光損失耐性の向上につながる。工程１において、アンダークラッド層１の基板１０とコア層２の基板２０の熱膨張係数は可能な限り近いものを選定することにより、後のプロセスでの熱処理プロセスにおいて基板割れを抑制することが可能になる。本開示において、基板１０と基板２０とを直接接合することにより形成された基板を接合基板ともいう。 In step 1, the substrate 10 of the nonlinear optical material that will be the undercladding layer 1 and the substrate 20 of the nonlinear optical material that will be the core layer 2 are directly bonded. The direct bonding in step 1 leads to an improvement in resistance to light loss when high-intensity light is used as input light by using a direct bonding technique that does not use an adhesive. In step 1, the substrate 10 of the undercladding layer 1 and the substrate 20 of the core layer 2 are selected so that their coefficients of thermal expansion are as close as possible, so that cracking of the substrate can be suppressed in the subsequent heat treatment process. become. In the present disclosure, a substrate formed by directly bonding the substrate 10 and the substrate 20 is also referred to as a bonded substrate.
　工程２において、接合基板のうちのコア層２となる非線形光学材料の基板２０を薄膜化する。薄膜化の手法に関しては特に制限はなく、研削研磨工程やスマートカット法等が候補として挙げられる。 In step 2, the nonlinear optical material substrate 20, which will be the core layer 2 of the bonded substrate, is thinned. There are no particular restrictions on the method of thinning, and candidates include a grinding polishing process, a smart cut method, and the like.
　工程３において、基板２０を加工することにより光導波路４０のコア層２を形成する。光導波路形成手法に関しては特に制限はなく、ドライエッチングプロセスやダイシングソーによる光導波路４０のコア層２の切り出し等が候補として挙げられる。工程３において、必要に応じて既知の方法により光導波路４０のオーバークラッド層３を形成する。 In step 3, the core layer 2 of the optical waveguide 40 is formed by processing the substrate 20 . There are no particular restrictions on the method of forming the optical waveguide, and candidates include a dry etching process, cutting out the core layer 2 of the optical waveguide 40 using a dicing saw, and the like. In step 3, the over-cladding layer 3 of the optical waveguide 40 is formed by a known method as required.
　工程４において、作製した光導波路４０を有する基板をチップ化して光導波路素子を生成する。チップ化の手法として、ダイシングソーを用いた手法が候補として挙げられるが、加工手法に特に制限はない。また、チップ化の後に端面を光学研磨したり、反射防止膜をコートしたりすることで、光導波路素子としてのチップ５０に光が入射もしくは出射する際の光損失を低減することが可能になる。 In step 4, the substrate having the manufactured optical waveguide 40 is chipped to produce an optical waveguide element. As a chipping method, a method using a dicing saw can be mentioned as a candidate, but there is no particular limitation on the processing method. In addition, by optically polishing the end face or coating an anti-reflection film after chipping, it is possible to reduce light loss when light enters or exits the chip 50 as an optical waveguide element. .
　工程5において、作製した光導波路４０を有するチップ５０に対して光学特性評価を行う。 In step 5, the chip 50 having the manufactured optical waveguide 40 is evaluated for optical characteristics.
　図２の従来の光導波路素子の製造方法では、工程５において光導波路素子であるチップ５０の光導波路４０の光学特性を評価した際に、作製誤差等が原因となり目標とする光学特性を満たさない光導波路を多数製造してしまい、一度チップ化すると再度加工することは困難であるために歩留まりの向上に限界があった。 In the conventional method for manufacturing an optical waveguide element shown in FIG. 2, when the optical characteristics of the optical waveguide 40 of the chip 50, which is an optical waveguide element, are evaluated in step 5, the target optical characteristics are not satisfied due to manufacturing errors and the like. A large number of optical waveguides are manufactured, and once they are made into chips, it is difficult to process them again, which limits the improvement in yield.
　図３に示すように本実施形態の光導波路素子の製造方法は、工程１の直接接合、工程２の薄膜化、工程３の光導波路形成、工程４のチップ化、および工程５の光学特性評価を含み、工程３１の構造計測、工程３２の特性予測、工程３３の補正量決定、および工程３４３の再加工をさらに含む。図３の製造方法は、光導波路構造の補正プロセスを組み入れた方法である。 As shown in FIG. 3, the method for manufacturing an optical waveguide element of the present embodiment includes direct bonding in step 1, thinning in step 2, optical waveguide formation in step 3, chip formation in step 4, and optical characteristic evaluation in step 5. and further includes structural measurement in step 31, property prediction in step 32, correction amount determination in step 33, and rework in step 343. The manufacturing method of FIG. 3 is a method incorporating a correction process for the optical waveguide structure.
　工程１および工程２はそれぞれ、図２を参照して説明したのと同様の工程である。 Steps 1 and 2 are the same steps as described with reference to FIG.
　工程３において、基板２０を加工することにより光導波路４０のコア層２を形成する。光導波路形成手法に関しては特に制限はなく、ドライエッチングプロセスやダイシングソーによる光導波路の切り出し等が候補として挙げられる。工程３において、オーバークラッド層３は形成しない。光導波路４０のオーバークラッド層３が必要な場合には、工程３１および工程３２よりも後に形成する。 In step 3, the core layer 2 of the optical waveguide 40 is formed by processing the substrate 20 . There are no particular restrictions on the method of forming the optical waveguide, and candidates include a dry etching process, cutting out the optical waveguide using a dicing saw, and the like. In step 3, no overcladding layer 3 is formed. If the overcladding layer 3 of the optical waveguide 40 is required, it is formed after steps 31 and 32 .
　工程３１において、作製した光導波路４０の構造を計測する。主な計測項目としては、光の伝搬方向に対する光導波路４０のコア層２の幅Ｗと高さＨの分布が候補として挙げられる。これは、これらの項目の積により光導波路４０の実効屈折率が決定し、最終的に光導波路４０の伝搬方向に対する光導波路の実効屈折率分布に最も影響のある項目であるためである。構造の計測方法としては、光導波路４０のコア層２の幅Ｗの計測としては光学顕微鏡、もしくは測長走査型電子顕微鏡（Ｓｃａｎｎｉｎｇ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｅ：ＳＥＭ）による実測が候補として挙げられる。また光導波路４０のコア層２の高さＨ、つまりコア層２の膜厚分布は光干渉を利用した手法が候補として挙げられる。工程３１における光導波路４０のコア層２の高さＨの計測は、工程２の後および工程３の前に実施してもよい。この場合、光導波路が形成される前の薄膜化された基板２０の膜厚の分布を計測してもよい。 In step 31, the structure of the fabricated optical waveguide 40 is measured. As a main measurement item, the distribution of the width W and the height H of the core layer 2 of the optical waveguide 40 with respect to the propagation direction of light can be mentioned as a candidate. This is because the effective refractive index of the optical waveguide 40 is determined by the product of these items, and is the item that ultimately affects the effective refractive index distribution of the optical waveguide 40 in the propagation direction. As a method for measuring the structure, the width W of the core layer 2 of the optical waveguide 40 can be measured using an optical microscope or a scanning electron microscope (SEM). Further, the height H of the core layer 2 of the optical waveguide 40, that is, the film thickness distribution of the core layer 2, can be determined by a method using optical interference. The measurement of the height H of the core layer 2 of the optical waveguide 40 in step 31 may be performed after step 2 and before step 3 . In this case, the film thickness distribution of the thinned substrate 20 before the optical waveguide is formed may be measured.
　工程３２において、工程３１で得られた構造の実測値（光導波路４０のコア層２の幅Ｗの分布と高さＨの分布）をもとにシミュレーター上に同一構造（光導波路のデジタルツイン）を作成し、光学特性をシミュレートする。この際のシミュレーションの方法は、目的とする物理量（例えば光損失、非線形光学効果）に応じて決定し得る。シミュレーションの代表的な手法としてビーム伝搬法（Ｂｅａｍ　Ｐｒｏｐａｇａｔｉｏｎ　Ｍｅｔｈｏｄ：　ＢＰＭ）や時間領域差分法（Ｆｉｎｉｔｅ　Ｄｉｆｆｅｒｅｎｃｅ　Ｔｉｍｅ　Ｄｏｍａｉｎ：　ＦＤＴＤ）を例示し得る。工程３２においてシミュレーションにより予想した光学特性が目標特性であるかどうかを決定する。予想した光学特性が目標特性であると決定される場合は工程４のチップ化工程へと進み、作製誤差等により予想した光学特性が目標特性とならないと決定される場合は、工程３３から工程３４の補正工程（トリミングプロセス）へと進む。 In step 32, based on the measured values of the structure obtained in step 31 (the distribution of the width W and the height H of the core layer 2 of the optical waveguide 40), the same structure (digital twin of the optical waveguide) is generated on the simulator. to simulate optical properties. The method of simulation at this time can be determined according to the target physical quantity (for example, optical loss, nonlinear optical effect). Typical simulation methods include the beam propagation method (BPM) and the finite difference time domain (FDTD). In step 32, it is determined whether the optical properties predicted by the simulation are the target properties. If the expected optical characteristics are determined to be the target characteristics, the process proceeds to step 4, which is a chip forming step. to the correction process (trimming process).
　工程３３において、工程３２で作製したシミュレーター上の構造（デジタルツイン）の光学特性が目標特性に到達できるような構造となるよう、各種構造パラメーターをどの程度変化させればよいかを計算し、補正量（トリミング量）を決定する。 In step 33, the extent to which various structural parameters should be changed is calculated and corrected so that the optical characteristics of the structure (digital twin) on the simulator produced in step 32 can reach the target characteristics. Determine the amount (trimming amount).
　工程３４において、工程３３で決定した補正量を基に実際の構造に対して補正（トリミング）加工を行う。この工程では、光導波路４０のコア層２の幅Ｗおよび厚さＨの少なくとも一方を補正し得る。補正加工の手法として局所エッチング装置を用いた局所的な構造改変が候補として挙げられる。 In step 34, correction (trimming) processing is performed on the actual structure based on the correction amount determined in step 33. In this step, at least one of the width W and thickness H of the core layer 2 of the optical waveguide 40 can be corrected. As a method of correction processing, local structural modification using a local etching apparatus is a candidate.
　工程３５において、光導波路構造が目標特性を発揮する構造となるまで工程３１から工程３４までを繰り返す。この工程により、最終的に得られる光導波路４０のコア層２の構造は当初目標設定値を満たす構造となる。必要に応じて、オーバークラッド層３を堆積する。本実施形態では、光導波路４０は、アンダークラッド層１と、コア層２と、オーバークラッド層３を含むリッジ型の光導波路としている。 In step 35, steps 31 to 34 are repeated until the optical waveguide structure exhibits the target characteristics. By this process, the structure of the core layer 2 of the optical waveguide 40 finally obtained satisfies the initially set target values. An overcladding layer 3 is deposited as required. In this embodiment, the optical waveguide 40 is a ridge-type optical waveguide including an undercladding layer 1 , a core layer 2 and an overcladding layer 3 .
　工程４および工程５はそれぞれ、図２を参照して説明したのと同様の工程である。 Steps 4 and 5 are the same steps as described with reference to FIG.
　本実施形態の光導波路素子の製造方法（上記工程１から工程５）により、従来の光導波路素子の製造方法に比べた歩留まりおよび特性の飛躍的な向上が期待される。 The manufacturing method of the optical waveguide element of the present embodiment (steps 1 to 5 above) is expected to dramatically improve the yield and characteristics compared to the conventional manufacturing method of the optical waveguide element.
（直接接合方法（工程１））
　接着剤を用いずに基板同士を強固に接合する技術として、直接接合技術がある。直接接合技術は、初めに化学薬品を用いて基板の表面処理を行った後、基板同士を重ね合わせることにより、表面間引力により接合する方法である。各種基板の表面処理条件（温度や薬品の種類等）は実際に接合する基板の種類および組み合わせによって最適化し得る。また、基板を貼り合わせる際はマイクロパーティクルが極力存在しない清浄雰囲気化にて、作業を行うことが望ましい。また、直接接合プロセスは常温で行われるが、このときの接合強度は小さいため、その後に高温での熱処理を行って、拡散接合を行い、接合強度を向上し得る。接合された基板は、接合面にマイクロパーティクル等の挟み込みがなく、ボイドフリーであり、室温状態においてクラックなどは発生しない。 (Direct bonding method (step 1))
A direct bonding technique is available as a technique for firmly bonding substrates together without using an adhesive. The direct bonding technique is a method in which the surfaces of the substrates are first treated using a chemical agent, and then the substrates are placed on top of each other to bond the substrates by the attractive force between the surfaces. The surface treatment conditions (temperature, type of chemicals, etc.) for various substrates can be optimized according to the type and combination of substrates to be actually bonded. Moreover, when bonding the substrates together, it is desirable to perform the work in a clean atmosphere in which microparticles are not present as much as possible. In addition, although the direct bonding process is performed at normal temperature, since the bonding strength at this time is small, heat treatment at a high temperature is performed after that, diffusion bonding can be performed, and the bonding strength can be improved. The bonded substrates are void-free with no inclusion of microparticles or the like on the bonded surfaces, and no cracks or the like occur at room temperature.
　接着剤等を用いずに基板同士を強固に接合することのできる直接接合の技術は、高光損傷耐性、長期信頼性、デバイス設計の容易性などの特徴を有する。他にも、非線形光学効果の一種である差周波発生を用いた中赤外域の光発生において、不純物の混入や接着剤等の吸収を回避できるといったメリットも存在する。 The technology of direct bonding, which can firmly bond substrates without using adhesives, etc., has characteristics such as high optical damage resistance, long-term reliability, and ease of device design. In addition, in light generation in the mid-infrared region using difference frequency generation, which is a type of nonlinear optical effect, there is also the advantage of avoiding the contamination of impurities and the absorption of adhesives and the like.
（薄膜化方法（工程２））
　基板２０を薄膜化する技術として、研削・研磨工程やスマートカットによる薄膜化工程等がある。本実施形態においては薄膜化の手法に特に制限はなく、研削・研磨による薄膜化でもスマートカットによる薄膜化のいずれであってもよい。 (Method for thinning (step 2))
Techniques for thinning the substrate 20 include a grinding/polishing process, a thinning process using smart cut, and the like. In this embodiment, the method of thinning is not particularly limited, and thinning by grinding/polishing or thinning by smart cut may be used.
　研削・研磨工程による薄膜化では、研削研磨用の定盤の平坦度が管理された装置を用いて、任意の深さに光導波路が存在するようになるまで研削研磨加工を施す。研削研磨工程終了後にポリッシング加工を行うことで、鏡面の研磨表面(光学端面)を得ることができる。最終的に基板の平行度(基板の最大高さと最小高さの差)を光学的な平行度測定器を用いて測定することで、基板全体としての平行度を得ることができる。 　In the thinning by the grinding/polishing process, the grinding/polishing process is performed until the optical waveguide exists at an arbitrary depth using a device with a controlled flatness of the surface plate for grinding/polishing. A mirror polished surface (optical end face) can be obtained by performing a polishing process after the grinding and polishing step. Finally, the parallelism of the substrate as a whole can be obtained by measuring the parallelism of the substrate (the difference between the maximum height and the minimum height of the substrate) using an optical parallelism measuring instrument.
　スマートカットによる薄膜化工程は、主にイオンの打ち込み工程と薄膜の剥離工程の２つの工程からなる。イオン打ち込み工程では二次非線形光学効果を有する薄膜化をする必要がある基板２０に対しヘリウムもしくは水素イオンを打ち込む。イオンは制御された加速電圧と制御されたドーズ量のもと基板表面から打ち込まれ、表面からある一定の深さにトラップされる。使用するイオンは水素やヘリウムといった基板を構成する原子よりも小さいものが望ましい。基板剥離工程ではイオンを打ち込んだ上述の基板に対して熱処理を施すことで、基板内のダメージ層を境に基板を剥離する工程である。非線形光学材料が周期分極反転構造を有する場合には、パターニングされた分極方向を崩さないために、基板剥離工程における熱処理温度は二次非線形光学結晶のキュリー温度以下で行うことになる。 The thinning process by SmartCut mainly consists of two processes: the ion implantation process and the thin film peeling process. In the ion implantation step, helium or hydrogen ions are implanted into the substrate 20 which needs to be thinned to have a second-order nonlinear optical effect. Ions are implanted from the substrate surface under a controlled acceleration voltage and a controlled dose, and are trapped at a certain depth from the surface. The ions to be used are desirably smaller than the atoms forming the substrate, such as hydrogen and helium. In the substrate peeling process, the above-described substrate into which ions are implanted is subjected to heat treatment, thereby peeling the substrate along the damaged layer in the substrate. In the case where the nonlinear optical material has a periodically poled structure, the heat treatment temperature in the substrate peeling step should be lower than the Curie temperature of the secondary nonlinear optical crystal so as not to disturb the patterned polarization direction.
　上記手法により薄膜化したコア層は、その加工精度により面内膜厚分布を有する。特に高光損傷耐性が存在する比較的大きいコア層２を有するリッジ型の光導波路４０が作製可能な、研削研磨による薄膜化プロセスでは膜厚分布抑制において比較的大きな加工限界が存在する。これら加工精度限界により存在する膜厚分布によって、最終的に目標とする構造を有する光導波路の作製が困難である。 The core layer thinned by the above method has an in-plane film thickness distribution due to its processing accuracy. In particular, in the thinning process by grinding and polishing, which can produce a ridge-type optical waveguide 40 having a relatively large core layer 2 with high optical damage resistance, there is a relatively large processing limit in suppressing the film thickness distribution. It is difficult to fabricate an optical waveguide having a final target structure due to the film thickness distribution that exists due to these processing accuracy limits.
（光導波路のコア層の形成方法（工程３））
　リッジ型の光導波路４０のコア層２の形成手法として、ドライエッチングプロセスを用いる方法やダイシングソーに代表される機械加工を用いる方法等がある。本実施形態においてはリッジ型の光導波路４０のコア層2の形成手法に特に制限はなく、ドライエッチングを用いる方法であっても、ダイシングソーを用いる方法、その他の形成手法のいずれであってもよい。 (Method for Forming Core Layer of Optical Waveguide (Step 3))
Methods for forming the core layer 2 of the ridge-type optical waveguide 40 include a method using a dry etching process and a method using a mechanical process represented by a dicing saw. In this embodiment, the method of forming the core layer 2 of the ridge-type optical waveguide 40 is not particularly limited, and may be a method using dry etching, a method using a dicing saw, or any other forming method. good.
　ドライエッチングを用いる手法では、ドライエッチング装置を用いてコア層２となる基板２０の表面（以下、コア基板表面という）をエッチングすることにより、光導波路４０のコア層２を形成する。この際、コア基板表面には通常のフォトリソグラフィのプロセスによって光導波路４０のパターンを作製する。光導波路パターンのレジストをマスクとし、ドライエッチング装置によりドライエッチングすることにより、光導波路４０のコア層２を形成する。この手法では、以下の二つが原因となり、光導波路幅に分布が生じる。 In the method using dry etching, the core layer 2 of the optical waveguide 40 is formed by etching the surface of the substrate 20 to be the core layer 2 (hereinafter referred to as the core substrate surface) using a dry etching apparatus. At this time, the pattern of the optical waveguide 40 is formed on the surface of the core substrate by a normal photolithography process. The core layer 2 of the optical waveguide 40 is formed by dry etching with a dry etching apparatus using the resist of the optical waveguide pattern as a mask. In this method, the width of the optical waveguide is distributed due to the following two causes.
　一つ目の原因は、フォトリソグラフィのプロセスにより作成された光導波路パターンの作製誤差である。このプロセスでは、フォトリソグラフィの条件を最適化することにより光導波路幅分布を抑制することは可能であるが、完全に光導波路幅分布が生じないレジストパターンを作製することは困難である。 The first cause is the manufacturing error of the optical waveguide pattern created by the photolithography process. In this process, it is possible to suppress the optical waveguide width distribution by optimizing the photolithography conditions, but it is difficult to produce a resist pattern in which the optical waveguide width distribution does not occur completely.
　二つ目の原因は、ドライエッチング時における面内エッチング量分布である。ドライエッチング工程において、最終的に形成される光導波路４０の幅に影響するエッチング量の面内分布を完全になくすことは困難である。その理由として、例えば周期分極反転構造を有する非線形光学基板であった場合、分極方向によってエッチングレートが若干異なること、プロセス中に基板面内に温度分布が生じエッチングレートが基板温度によって異なること、ドライエッチング時のプラズマの密度が必ず面内一様分布とならないことが挙げられる。 The second cause is the in-plane etching amount distribution during dry etching. In the dry etching process, it is difficult to completely eliminate the in-plane distribution of the etching amount that affects the width of the optical waveguide 40 that is finally formed. The reasons for this are that, for example, in the case of a nonlinear optical substrate having a periodically poled structure, the etching rate varies slightly depending on the polarization direction, the temperature distribution occurs in the substrate surface during the process, and the etching rate varies depending on the substrate temperature. One reason for this is that the density of plasma during etching does not always have a uniform distribution within the plane.
　ダイシングソーに代表される機械加工を用いる手法では、通常のダイシングプロセスに用いられるダイシングブレードを用いることで光導波路４０のコア層２を形成する手法である。この手法では、主に加工する機械の精度、特にサンプルを固定するステージや加工部の位置精度により、作製される光導波路４０の構造の精度が決定する。そのため、光導波路４０のコア層2の作製精度には限界があり、完全に設計通りの光導波路幅を有する光導波路の作製は困難である。 A method using machining represented by a dicing saw is a method of forming the core layer 2 of the optical waveguide 40 by using a dicing blade used in a normal dicing process. In this method, the accuracy of the structure of the optical waveguide 40 to be fabricated is determined mainly by the accuracy of the machine used for processing, particularly the positional accuracy of the stage and processing section for fixing the sample. For this reason, there is a limit to the accuracy of manufacturing the core layer 2 of the optical waveguide 40, and it is difficult to manufacture an optical waveguide having an optical waveguide width exactly as designed.
　以上の理由により、現在広く用いられているリッジ型光導波路の作製プロセスにおいては、当初設定した目標構造、特に光導波路幅を有する光導波路と完全に一致する光導波路を作製することは困難である。 For the above reasons, in the fabrication process of ridge-type optical waveguides that are widely used today, it is difficult to fabricate an optical waveguide that perfectly matches the initially set target structure, especially an optical waveguide having an optical waveguide width. .
（再加工（トリミング加工））
　図２を参照して説明したように従来の光導波路素子の製造方法では、工程４においてチップ化した後に、工程５において光学特性評価を行っていた。工程５における「特性」とは、光導波路の機能や性能を表す指標値であり、例えば非線形光学素子の場合は二次非線形光学定数や光の透過率等である。 (Reprocessing (trimming))
As described with reference to FIG. 2, in the conventional method of manufacturing an optical waveguide element, optical characteristics are evaluated in step 5 after chipping in step 4. FIG. The "characteristic" in step 5 is an index value representing the function and performance of the optical waveguide, such as second-order nonlinear optical constant and light transmittance in the case of a nonlinear optical element.
　従来の光導波路素子の製造方法においては、目標とする光学特性値を設定し、その実現に向けて光導波路の構造を設計する。そして目標とする構造をめざして、光導波路の加工工程に移る。実際の加工工程では、得られる光導波路４０の構造は目標とする構造から逸脱してしまう。これは各工程における製造誤差のためである。工程４において、工程１から工程３を経て得た光導波路４０をダイシング等によりチップ化し、光学端面を形成し、光導波路４０を有するチップ５０が完成する。工程５において、完成したチップ５０に関して検査することで初めて光導波路４０の特性がわかる。従来の光導波路形成工程では、チップ化し検査するまで光導波路の特性が分からず、検査により目標特性を満たさないチップが製造されたことがわかっても構造補正はチップ化した後では困難であり、目標とする特性を有する構造が得られないチップを製造してしまうという課題があった。 In the conventional method of manufacturing an optical waveguide element, a target optical characteristic value is set, and the structure of the optical waveguide is designed to achieve it. Then, aiming at the target structure, the process moves to the optical waveguide processing step. In an actual processing step, the structure of the optical waveguide 40 obtained deviates from the target structure. This is due to manufacturing errors in each process. In step 4, the optical waveguide 40 obtained through steps 1 to 3 is chipped by dicing or the like, optical end faces are formed, and the chip 50 having the optical waveguide 40 is completed. In step 5, the characteristics of the optical waveguide 40 are known for the first time by inspecting the completed chip 50 . In the conventional optical waveguide forming process, the characteristics of the optical waveguide are not known until it is chipped and inspected. There is the problem of producing chips that do not provide structures with the desired characteristics.
　図３を参照して説明した本実施形態の光導波路素子の製造方法においても目標とする光学特性値を設定し、その実現に向けて光導波路の構造を設計する。そして目標とする構造をめざして、光導波路の加工工程に移る。実際の加工工程では、得られる光導波路４０の構造は目標とする構造から逸脱してしまう。これは各工程における製造誤差のためであり、この工程までは従来の光導波路素子の製造方法と同等である。 Also in the method of manufacturing the optical waveguide element of the present embodiment described with reference to FIG. 3, target optical characteristic values are set, and the structure of the optical waveguide is designed to achieve them. Then, aiming at the target structure, the process moves to the optical waveguide processing step. In an actual processing step, the structure of the optical waveguide 40 obtained deviates from the target structure. This is due to manufacturing errors in each process, and the process up to this process is the same as the conventional method of manufacturing an optical waveguide element.
　本実施形態においては、作製した光導波路４０のコア層２の高さＨや幅Ｗに代表される各種構造値を計測することで得られた構造情報を基に、シミュレーター上に同一構造を形成し、各種シミュレーションの手法を用いて光学特性を予想する。この際にシミュレーター上に作製される光導波路は、実際に作製した光導波路４０のデジタルツインとなるものであり、シミュレーター上で非破壊的に特性値を予想することが可能である。シミュレーター上で得られた特性値が当初設定した目標値に達しているか否かの合否判定（当初設定した目標値となっているかどうかの判定）を行う。予測された特性が合格である場合は、必要に応じてオーバークラッド層３を形成した後に、チップ化の工程に進む。 In this embodiment, the same structure is formed on a simulator based on structural information obtained by measuring various structural values represented by the height H and width W of the core layer 2 of the fabricated optical waveguide 40. Then, the optical characteristics are predicted using various simulation techniques. The optical waveguide produced on the simulator at this time is a digital twin of the optical waveguide 40 actually produced, and it is possible to predict characteristic values non-destructively on the simulator. A pass/fail judgment is made as to whether or not the characteristic values obtained on the simulator have reached the initially set target values (judgment as to whether or not the initially set target values are met). If the predicted characteristics are acceptable, the over-cladding layer 3 is formed as necessary, and then the process proceeds to chip formation.
　予測された特性が不合格である場合はコア層２の構造についての補正工程(トリミング工程)に移る。補正工程における構造補正量はシミュレーター上で計算し、シミュレーター上の構造に補正量を反映させ、得られる光学特性が合格基準を上回るまで計算を行う。そして得られた補正量を基に、実際の光導波路４０のコア層２の再加工（トリミング加工）を行う。この再加工の手法は、シミュレーター上で得られた補正量の再加工を実現可能な加工精度を有していればいずれでもよく、本実施形態においては局所的にドライエッチングを行う局所エッチングが候補技術として挙げられる。再加工が終了した後、再びコア層２の構造値を測定し、シミュレーター上にデジタルツインを再現し、光学特性予測を行う。この光学特性予測値が設定した目標値を満たすまで、上記補正工程（工程３１から工程３４）を繰り返すことで、目標とする特性を有する光導波路４０を作製することが可能になる。なお、光導波路４０の形状が矩形の断面の場合、当該光導波路４０の実効屈折率（等価屈折率）および伝搬特性等の光学特性は基本的にコア層の幅と高さ、コアの屈折率、及びクラッドの屈折率で決定される。また、コア層の幅Ｗの補正による光学特性の補正は、当該コア層の高さを補正することによっても行うことができる。したがって、光導波路のコア層の幅または高さの一方または双方を補正することにより、光導波路の光学特性を補正することができる。したがって、シミュレーター上で計算される構造補正量は、接合基板に形成された光導波路４０のコア層２の幅Ｗまたは高さＨの一方または双方についての補正量を示し得る。 If the predicted characteristics are unsatisfactory, the process moves to the correction process (trimming process) for the structure of the core layer 2. The structural correction amount in the correction process is calculated on the simulator, the correction amount is reflected in the structure on the simulator, and the calculation is performed until the obtained optical characteristics exceed the acceptance criteria. Then, based on the obtained correction amount, reprocessing (trimming) of the core layer 2 of the actual optical waveguide 40 is performed. This reprocessing method may be any method as long as it has a processing accuracy that allows reprocessing of the correction amount obtained on the simulator, and in this embodiment, local etching that performs dry etching locally is a candidate. technology. After the reprocessing is finished, the structural values of the core layer 2 are measured again, the digital twin is reproduced on the simulator, and the optical properties are predicted. By repeating the correction steps (steps 31 to 34) until the predicted optical property value satisfies the set target value, it is possible to fabricate the optical waveguide 40 having the target property. When the shape of the optical waveguide 40 has a rectangular cross section, the optical characteristics such as the effective refractive index (equivalent refractive index) and propagation characteristics of the optical waveguide 40 are basically determined by the width and height of the core layer and the refractive index of the core. , and the refractive index of the cladding. Correction of the optical characteristics by correcting the width W of the core layer can also be performed by correcting the height of the core layer. Therefore, by correcting one or both of the width and height of the core layer of the optical waveguide, the optical characteristics of the optical waveguide can be corrected. Therefore, the structural correction amount calculated on the simulator can indicate the correction amount for one or both of the width W and height H of the core layer 2 of the optical waveguide 40 formed on the bonded substrate.
（光導波路の高さの計測）
　本実施形態において、光導波路４０のコア層２の高さＨの分布（膜厚分布）は光干渉を用いて計測される。具体的には、コア層２となる基板２０の表面に光を入射し、光の反射スペクトル解析による多層膜の膜厚の非接触評価によって実施できる。反射光との干渉を用いて膜厚を解析する手法は広く普及している手法であり、本実施例でも汎用的に用いられている光干渉の手法を用いて膜厚を計測する。膜厚の計測は工程３の光導波路形成よりも前の工程２の後に基板表面全体に対して計測をする手法でも、工程３の光導波路形成の後の工程４において光導波路４０のコア層２のみに対して計測する手法のいずれであってもよい。 (Measurement of height of optical waveguide)
In this embodiment, the distribution (film thickness distribution) of the height H of the core layer 2 of the optical waveguide 40 is measured using optical interference. Specifically, light is incident on the surface of the substrate 20 serving as the core layer 2, and non-contact evaluation of the film thickness of the multilayer film can be performed by light reflection spectrum analysis. The method of analyzing the film thickness by using interference with reflected light is a widely used method, and the film thickness is measured using the widely used optical interference method also in this embodiment. Even if the film thickness is measured for the entire substrate surface after step 2, which is before the optical waveguide is formed in step 3, the core layer 2 of the optical waveguide 40 is measured in step 4 after the optical waveguide is formed in step 3. Any of the methods of measuring for only may be used.
　また、本実施形態における膜厚計測手法は光干渉を用いるもの以外の手法でもよく、光導波路構造に対して非侵襲であればいずれの手法でもよい。 In addition, the film thickness measurement method in this embodiment may be a method other than the method using optical interference, and any method may be used as long as it is non-invasive to the optical waveguide structure.
（光導波路の幅の計測）
　本実施形態において、光導波路４０のコア層２の幅Ｗの分布は直接的に光導波路４０のコア層２を観察することで計測される。具体的な観察手法としては、光導波路構造に対して非侵襲であればいずれでもよく、光学顕微鏡を用いる方法や、走査型電子顕微鏡といった電子顕微鏡を用いる方法が代表例として挙げられる。上記手法のほかにも、段差計を用いた手法や原子間力顕微鏡を用いた高精度な測定手法であってもよい。この際、光導波路のコア層２の幅Ｗの分布を測定する際の測定点の間隔に特に制限はなく、構造のトリミング工程において必要十分である構造情報が得られる測定点数であり、尚且つ光導波路形成プロセスのスループットが著しく低下しない測定点数であればよい。 (Measurement of Width of Optical Waveguide)
In this embodiment, the distribution of the width W of the core layer 2 of the optical waveguide 40 is measured by directly observing the core layer 2 of the optical waveguide 40 . Any specific observation method may be used as long as it is non-invasive to the optical waveguide structure, and representative examples include a method using an optical microscope and a method using an electron microscope such as a scanning electron microscope. In addition to the above method, a method using a step meter or a high-precision measurement method using an atomic force microscope may be used. At this time, there is no particular limitation on the interval between measurement points when measuring the distribution of the width W of the core layer 2 of the optical waveguide, and the number of measurement points is such that necessary and sufficient structural information can be obtained in the trimming process of the structure, and Any number of measurement points may be used as long as the throughput of the optical waveguide forming process does not significantly decrease.
（シミュレーター）
　本実施形態の光導波路素子の製造方法では、シミュレーターを用いて、実際に作製した光導波路４０のコア層２と同一構造をシミュレートし、シミュレートした構造の光学特性を予想し、予想した光学特性が当初の目標特性を有するか否かの検査を行うことで合否判定をする。シミュレートした構造の光学特性が目標値に満たない場合は、工程３３において、コア層２の構造をどの程度補正することで目標とする光学特性を有することになるかをシミュレーター上で計算する。そして、工程３４において、工程３３で得られた補正量を用いて実際に作製した光導波路４０のコア層２に対して、構造の補正をする。 (simulator)
In the method for manufacturing an optical waveguide element of the present embodiment, a simulator is used to simulate the same structure as the core layer 2 of the actually manufactured optical waveguide 40, and the optical characteristics of the simulated structure are predicted. A pass/fail decision is made by testing whether the property has the initial target property. If the optical properties of the simulated structure do not meet the target values, in step 33, the degree to which the structure of the core layer 2 should be corrected to obtain the target optical properties is calculated on the simulator. Then, in step 34, the structure of the core layer 2 of the optical waveguide 40 actually manufactured is corrected using the amount of correction obtained in step 33. FIG.
　本実施形態では、構造補正手法として、高精度に狙った範囲だけを局所的に加工することが可能な局所エッチング手法を用いるが、光導波路４０のコア層２の構造を高精度に加工できる手法であればいずれであってもよい。そして加工後の構造に対して、同様に光導波路４０のコア層２の高さＨや幅Ｗといった構造値の測定を行う。得られた加工後の構造値を用いてシミュレーター上に実際の光導波路４０のコア層２の構造のデジタルツインとなる様な光導波路のコアの構造を再度作成し、光学特性を予想し、予想した光学特性が当初目標特性を有するか否かの検査をシミュレーター上で行うことで合否判定をする。工程３１の構造計測、工程３２の特性予測、工程３３の補正量決定、工程３４の再加工、工程３１の構造計測、および工程３２の特性予測という一連の工程を、予想した光学特性が当初設定した目標特性となるまで繰り返すことで、目標特性を有する光導波路の形成が可能になる。 In this embodiment, as a structural correction method, a local etching method capable of locally processing only a target range with high accuracy is used. It can be either. Then, structural values such as the height H and the width W of the core layer 2 of the optical waveguide 40 are similarly measured for the structure after processing. Using the obtained post-processing structural values, the structure of the core of the optical waveguide is recreated on the simulator so as to be a digital twin of the structure of the core layer 2 of the actual optical waveguide 40, and the optical characteristics are predicted. A pass/fail judgment is made by performing an inspection on a simulator to see if the optical properties obtained initially have the target properties. A series of steps of structural measurement in step 31, property prediction in step 32, correction amount determination in step 33, reprocessing in step 34, structural measurement in step 31, and property prediction in step 32 are initially set with the expected optical properties. It is possible to form an optical waveguide having the target characteristics by repeating the process until the desired characteristics are obtained.
　図４は、本実施形態の光導波路素子の製造方法において使用し得るシミュレーターを構成する計算機１００の概略構成を示す図である。計算機１００は、プロセッサ１０１と、メモリ１０２と、入力装置１０３と、出力装置１０４と、通信装置１０５と、ストレージ１０６とを有する。プロセッサ１０１は、例えば、ＣＰＵ（Ｃｅｎｔｒａｌ　Ｐｒｏｃｅｓｓｉｎｇ　Ｕｎｉｔ）、集積回路（ＩＣ）に実装したマイクロプロセッサ、またはＭＰＵ（Ｍｉｃｒｏ－Ｐｒｏｃｅｓｓｉｎｇ　Ｕｎｉｔ）、若しくはその他のプロセッサとし得る。プロセッサ１０１は、ストレージ１０６に格納されたプログラムをメモリ１０２にロードして実行することで、計測データ処理部１３２および制御データ処理部１３３として機能することができる。メモリ１０２は、例えば、ＲＡＭ（Ｒａｎｄｏｍ　ａｃｃｅｓｓ　ｍｅｍｏｒｙ）またはＲＯＭ（Ｒｅａｄ　ｏｎｌｙ　ｍｅｍｏｒｙ）とし得る。入力装置１０３は、例えば、キーボード、マウス、カメラ、またはセンサーとし得る。出力装置１０４は、例えば、ディスプレイ装置、またはプリンタとし得る。通信装置１０５とは、例えば、無線通信装置または有線通信装置とし得る。ストレージ１０６は、例えば、ハードディスクドライブ（ＨＤＤ）またはソリッドステートドライブ（ＳＳＤ）とし得る。 FIG. 4 is a diagram showing a schematic configuration of a computer 100 that constitutes a simulator that can be used in the method for manufacturing an optical waveguide device according to this embodiment. Computer 100 has processor 101 , memory 102 , input device 103 , output device 104 , communication device 105 and storage 106 . The processor 101 can be, for example, a CPU (Central Processing Unit), a microprocessor implemented in an integrated circuit (IC), or an MPU (Micro-Processing Unit), or other processor. The processor 101 can function as a measurement data processing unit 132 and a control data processing unit 133 by loading a program stored in the storage 106 into the memory 102 and executing the program. Memory 102 may be, for example, RAM (Random Access Memory) or ROM (Read Only Memory). Input device 103 may be, for example, a keyboard, mouse, camera, or sensor. Output device 104 may be, for example, a display device or a printer. Communication device 105 may be, for example, a wireless communication device or a wired communication device. Storage 106 may be, for example, a hard disk drive (HDD) or solid state drive (SSD).
　計算機１００は、上述したシミュレーターの機能を実行する計測データ処理部１３２および制御データ処理部１３３を含む。計測データ処理部１３２は、図３を参照して説明した工程３２の特性予想を実行し、制御データ処理部１３３は、図３で説明した工程３３の補正量決定（トリミング量決定）を実行する。 The computer 100 includes a measurement data processing unit 132 and a control data processing unit 133 that execute the functions of the simulator described above. The measurement data processing unit 132 executes characteristic prediction in step 32 described with reference to FIG. 3, and the control data processing unit 133 executes correction amount determination (trimming amount determination) in step 33 described with reference to FIG. .
　図４のフィードフォワードシステムにおいて、実線は製造対象物の工程に従った流れを示している。また、破線は工程３１の構造計測によって得られる計測データを、また、一点鎖線は工程３４に対する「制御」のための補正量（トリミング量）データを、それぞれ示している。 In the feedforward system of Figure 4, the solid line indicates the flow of the product according to the process. The dashed line indicates measurement data obtained by structural measurement in step 31, and the one-dot chain line indicates correction amount (trimming amount) data for "control" in step 34, respectively.
　計測データ処理部１３２で導出された予測値は、制御データ処理部１３３に渡される。制御データ処理部１３３は、予測値に基づいて、後工程である工程３４における補正量（トリミング量）を決定する。制御データ処理部１３３は、工程３４が実施される際に、求めた補正量に応じて、製造装置に設定する工程３４の補正量データを供給する。 The predicted value derived by the measurement data processing unit 132 is passed to the control data processing unit 133. The control data processing unit 133 determines the correction amount (trimming amount) in step 34, which is the post-process, based on the predicted value. The control data processing unit 133 supplies the correction amount data of the process 34 to be set in the manufacturing apparatus according to the obtained correction amount when the process 34 is performed.
　以上説明したように、本実施形態の光導波路素子の製造方法によれば、従来の光導波路素子の製造方法における、各種プロセスの加工精度限界により実際に作製される光導波路構造は目標とする構造から逸脱してしまい、目標とする特性が得られないという課題を解決することが可能となる。 As described above, according to the method for manufacturing an optical waveguide element of the present embodiment, the optical waveguide structure actually manufactured due to the processing accuracy limits of various processes in the conventional method for manufacturing an optical waveguide element is the target structure. It is possible to solve the problem that the target characteristics cannot be obtained due to deviation from the
　本実施形態の光導波路素子の製造方法によれば、基板に形成された光導波路の構造の計測された構造値に基づいて光導波路の光学特性を予想し、光導波路の構造を補正する工程を経ることにより、従来手法に比べて光導波路製造工程における歩留まりおよび光導波路の性能の飛躍的向上が期待される。 According to the method for manufacturing an optical waveguide element of the present embodiment, the step of predicting the optical characteristics of the optical waveguide based on the measured structural values of the structure of the optical waveguide formed on the substrate and correcting the structure of the optical waveguide is performed. As a result, it is expected that the yield in the optical waveguide manufacturing process and the performance of the optical waveguide will be dramatically improved as compared with the conventional method.
　１　アンダークラッド層
　２　コア層
　３　オーバークラッド層
　１０、２０　基板
　４０　光導波路
　５０　チップ
　１００　計算機
　１０１　プロセッサ
　１０２　メモリ
　１０３　入力装置
　１０４　出力装置
　１０５　通信装置
　１０６　ストレージ
　１３２　計測データ処理部
　１３３　制御データ処理部 Reference Signs List 1 undercladding layer 2 core layer 3 overcladding layer 10, 20 substrate 40 optical waveguide 50 chip 100 computer 101 processor 102 memory 103 input device 104 output device 105 communication device 106 storage 132 measurement data processing section 133 control data processing section

Claims (6)

  1. 　光導波路素子の製造方法であって、
    　基板に形成された光導波路のコア層の高さ及び幅の少なくとも一方の構造値を計測することと、
    　前記計測された構造値に基づいて、前記光導波路の光学特性の予測することと、
    　前記予測された光学特性が目標とする光学特性とならないことを条件に、前記基板に形成された前記光導波路の前記コア層の高さ及び幅の少なくとも一方の補正量を決定し、前記決定した補正量に従って、前記基板に形成された前記光導波路の前記コア層の高さ及び幅の少なくとも一方を再加工することと、
    　前記予測された光学特性が前記目標とする光学特性となることを条件に、前記光導波路が形成された前記基板をチップ化することと
    を備える、製造方法。     A method for manufacturing an optical waveguide device,
    measuring a structural value of at least one of height and width of a core layer of an optical waveguide formed on a substrate;
    predicting optical properties of the optical waveguide based on the measured structural values;
    Determining a correction amount for at least one of the height and width of the core layer of the optical waveguide formed on the substrate on the condition that the predicted optical characteristics do not become the target optical characteristics, and reprocessing at least one of the height and width of the core layer of the optical waveguide formed on the substrate according to the correction amount;
    A manufacturing method comprising chipping the substrate on which the optical waveguide is formed on condition that the predicted optical characteristics become the target optical characteristics.
  2. 　前記光導波路の前記高さ及び幅の少なくとも一方の前記構造値は、前記高さ及び幅の少なくとも一方に対して非侵襲に計測される、請求項１に記載の製造方法。 The manufacturing method according to claim 1, wherein the structural value of at least one of the height and width of the optical waveguide is non-invasively measured with respect to at least one of the height and width.
  3. 　前記光導波路の前記光学特性を予測することは、前記光導波路の前記計測された構造値を用いてシミュレートされた光導波路の光学特性を計算することを含む、請求項１または２に記載の製造方法。 3. The method of claim 1 or 2, wherein predicting the optical properties of the optical waveguide comprises calculating optical properties of a simulated optical waveguide using the measured structural values of the optical waveguide. Production method.
  4. 　前記基板に形成された前記光導波路の前記コア層の高さ及び幅の少なくとも一方の補正量を決定することは、
    　　前記光導波路の前記計測された構造値を用いてシミュレートされた光導波路の光学特性が前記目標とする光学特性となる、前記シミュレートされた光導波路のコア層の高さ及び幅の少なくとも一方の構造値を計算することと、
    　　前記計算された構造値と前記計測された構造値に基づいて、前記基板に形成された前記光導波路の前記コア層の高さ及び幅の少なくとも一方の補正量を決定することと
    を備える、請求項１から３のいずれか一項に記載の製造方法。     Determining a correction amount for at least one of the height and width of the core layer of the optical waveguide formed on the substrate includes:
    At least one of a height and a width of a core layer of the simulated optical waveguide such that optical properties of the optical waveguide simulated using the measured structural values of the optical waveguide are the target optical properties. calculating the structure value of
    determining a correction amount for at least one of the height and width of the core layer of the optical waveguide formed on the substrate based on the calculated structural value and the measured structural value. Item 4. The manufacturing method according to any one of Items 1 to 3.
  5. 　前記決定した補正量に従って、前記基板に形成された前記光導波路の前記コア層の高さ及び幅の少なくとも一方を再加工することは、
    　　前記計算された構造値と前記計測された構造値に基づいて決定された前記補正量に基づいて、前記基板に形成された前記光導波路の前記コア層の高さ及び幅の少なくとも一方を局所的に再加工することを含む、請求項４に記載の製造方法。     reworking at least one of the height and width of the core layer of the optical waveguide formed on the substrate according to the determined correction amount;
    locally adjusting at least one of the height and width of the core layer of the optical waveguide formed on the substrate based on the correction amount determined based on the calculated structural value and the measured structural value; 5. The manufacturing method of claim 4, comprising reworking to
  6. 　アンダークラッド層となる基板と前記コア層となる基板とを直接接合することにより接合基板を形成することと、
    　前記接合基板の前記コア層となる基板を薄膜化することと、
    　前記コア層となる基板が薄膜化された前記接合基板に前記光導波路を形成することと
    をさらに備え
    　前記基板に形成された前記光導波路の前記コア層の高さの構造値を計測することは、前記接合基板に前記光導波路を形成する前の前記接合基板の薄膜化された前記コア層となる基板の膜厚を計測することを含む、請求項１から４のいずれか一項に記載の製造方法。     Forming a bonded substrate by directly bonding a substrate serving as an undercladding layer and a substrate serving as the core layer;
    thinning the substrate that will be the core layer of the bonding substrate;
    forming the optical waveguide on the bonding substrate in which the substrate serving as the core layer is thinned; measuring the structural value of the height of the core layer of the optical waveguide formed on the substrate 5. The method according to any one of claims 1 to 4, comprising measuring a film thickness of a thinned core layer substrate of the bonded substrate before forming the optical waveguide on the bonded substrate. Production method.
PCT/JP2021/019476 2021-05-21 2021-05-21 Manufacturing method for optical waveguide element WO2022244274A1 (en)

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WO2003027736A1 (en) * 2001-09-19 2003-04-03 Matsushita Electric Industrial Co., Ltd. Optical waveguide and method for fabricating the same
JP2003232948A (en) * 2001-12-03 2003-08-22 Furukawa Electric Co Ltd:The Method of manufacturing optical waveguide, optical waveguide device using the method, and waveguide type optical multiplexer/demultiplexer
JP2006243484A (en) * 2005-03-04 2006-09-14 Sumitomo Osaka Cement Co Ltd Optical waveguide element and manufacturing method therefor
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US20170023737A1 (en) * 2015-07-23 2017-01-26 Indian Institute Of Technology Madras Method and apparatus for modifying dimensions of a waveguide

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5627105A (en) * 1979-08-14 1981-03-16 Nippon Telegr & Teleph Corp <Ntt> Phase matching and coupling length adjusting hethod
JPS63249328A (en) * 1987-04-03 1988-10-17 Mitsubishi Electric Corp Manufacturing system
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JPH10307220A (en) * 1997-05-06 1998-11-17 Nippon Telegr & Teleph Corp <Ntt> Manufacture of optical waveguide type filter, and optical waveguide filter
WO2003027736A1 (en) * 2001-09-19 2003-04-03 Matsushita Electric Industrial Co., Ltd. Optical waveguide and method for fabricating the same
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JP2006243484A (en) * 2005-03-04 2006-09-14 Sumitomo Osaka Cement Co Ltd Optical waveguide element and manufacturing method therefor
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