Optical circuit manufacturing apparatus and method for manufacturing optical circuit

Abstract

There has been a problem with an optical circuit fabricated on a wafer in that a distribution (bias) is generated with respect to the properties thereof in the wafer surface due to various manufacturing related causes. The present invention is characterized in that the refractive index distribution of an upper clad is adjusted on the basis of the refractive index distributions of a lower clad and a core film, the film thickness of the core film, and, additionally, the intra-surface distribution of the effective refractive index of an optical waveguide (calculated from the core pattern width) or the like.

Description

[Technical field]

[0001] The present invention relates to optical waveguide components and silica-based planar lightwave circuits fabricated by flame deposition. [Background technology]

[0002] Optical devices such as semiconductor lasers, photodiodes, optical wavelength multiplexers / demultiplexers, and optical switches are configured with optical integrated circuits. In optical fiber communications, not only optical fibers as a transmission medium but also optical integrated circuits in these optical devices for processing optical signals play an important role (see, for example, Non-Patent Document 1). Semiconductor lasers generate light waves for superimposing signals as optical oscillators, and photodiodes operate as elements for converting the intensity of optical signals into electrical signals. Optical wavelength multiplexers / demultiplexers, typified by arrayed waveguide gratings, are used in wavelength division multiplexing communications as elements for multiplexing / demultiplexing different wavelengths of light (see, for example, Non-Patent Document 2). Optical switches have an important function in ROADM (Reconfigurable Optical Add / Drop Multiplexing) systems as elements for routing optical paths. These optical integrated circuits are generally configured with optical waveguides formed on a substrate. An optical waveguide consists of a core through which an optical signal propagates and a cladding that surrounds it. Semiconductor lasers and photodiodes are made of semiconductor materials such as InP, while arrayed waveguide gratings and optical switches are made of optical waveguide materials, mainly made of silica glass.

[0003] FIG. 1 is a block diagram showing a method for manufacturing an optical waveguide. A silica-based planar lightwave circuit made of silica-based glass is taken as an example for explanation. First, in a lower clad deposition step 1, a glass film that will become the lower clad 12 is deposited on a silicon substrate (wafer) 11. The lower clad 12 is made of SiO2 doped with P2O5 or B2O3, for example, deposited by flame hydrolysis deposition (FHD). Soot-like glass particles deposited by the FHD method are heated at a high temperature of 1000°C or higher to obtain a transparent lower clad 12. Next, in a core deposition step 2, a thin-film glass that will become the core 13, which has a higher refractive index than the lower clad 12, is deposited by the same FHD (Flame Hydrolysis Deposition) method. When depositing the core 13, a desired refractive index value can be obtained by adding, for example, GeO2 to SiO2. As in the lower clad deposition step 1, the transparent core 13 is formed by heating at a high temperature of 1000°C or higher. It is to be noted that the formation of the lower cladding and the core is not limited to the FHD method, and they may be formed by other well-known methods.

[0004] In a photoresist film formation process 3, a photoresist film 14 is formed on a substrate by spin coating. Next, in a circuit pattern exposure process 4, the photoresist film is irradiated with UV light 16 through a photomask 15 to expose a circuit pattern according to the mask pattern. Then, in a photoresist development process 5, the circuit pattern of the photoresist film is developed to obtain a photoresist pattern 17.

[0005] Next, in an etching step 6, the photoresist pattern 17 is transferred to the core by reactive ion etching (RIE) to obtain a core pattern 18. Then, in a resist removal step 7, the photoresist remaining on the core is removed by ashing. Finally, in an upper clad deposition step 8, an upper clad 19 is deposited by the same method as in the lower clad deposition step 1. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Fundamentals of Optical Waveguides 2nd edition (2010 / 8 / 4), P. 437 [Non-Patent Document 2] A. Himeno, K. Kato and T. Miya, "Silica-based planar lightwave circuits," in IEEE Journal of Selected Topics in Quantum Electronics, vol. 4, no. 6, pp. 913-924, Nov.-Dec. 1998, doi: 10.1109 / 2944.736076. Summary of the Invention

[0007] The optical waveguide obtained through the above manufacturing process is inspected for various characteristics, such as optical characteristics. Conventionally, in order to reflect the inspection results in the manufacturing process, manufacturing conditions that reflect the inspection results are set for each process after the entire series of processes are completed. This method has the problem that manufacturing errors accumulate in each process, so the later the process, the lower the accuracy of the inspection results. On the other hand, by resetting the manufacturing conditions for a process or adjusting the manufacturing conditions for a later process based on the inspection results obtained at the end of a process, it is possible to suppress the accumulation of manufacturing errors.

[0008] Therefore, if information on the processing results obtained in a certain process, for example, information on the resist pattern width obtained in a photolithography process, can be known immediately after the photolithography process, a process that reflects the information on the pattern width can be carried out in the subsequent etching process. Also, if the film thickness and refractive index of the core obtained in the core deposition process can be known immediately after the deposition process, the optical characteristics of the optical waveguide formed in the subsequent photolithography and etching processes can be predicted. In this way, if information on the optical waveguide components obtained in the previous process can be acquired during or immediately after the previous process, it is advantageous in terms of the throughput of the manufacturing process if it can be reflected in the processing conditions of the subsequent process or used to predict the optical characteristics obtained in the subsequent process.

[0009] In particular, in the FHD method that can be used in the lower cladding deposition step 1, the core deposition step 2, and the upper cladding deposition step 8 in the above-mentioned manufacturing process, a hydrolyzed raw material gas is sprayed by a burner onto a wafer placed on a rotating turntable to burn glass soot. At this time, various factors such as fluctuations in the environmental temperature and the rotation speed of the turntable, and discretization and fluctuations of the burner's trajectory cause fluctuations in the film thickness and refractive index within the wafer surface. In addition, manufacturing fluctuations also occur in the photolithography process from the photoresist film formation step 3 to the photoresist development step 5. In the spin coating of photoresist in the photoresist film formation step 3, a thick layer of resist may be formed on the outer periphery of the wafer due to the influence of surface tension at the edge of the wafer. In the exposure step in the circuit pattern exposure step 4, a distribution of the exposure amount occurs within the wafer surface due to uneven illuminance of UV light from the exposure machine, etc. Furthermore, in the development step in the photoresist development step 5, a distribution (bias) of the development amount may occur within the wafer surface due to differences in the timing at which the developer is dropped onto the wafer and spreads. The manufacturing deviations due to these pre-processing steps 3 to 5 may affect the film thickness and refractive index of the upper cladding that is finally formed in the post-processing step 8 of depositing the upper cladding.

[0010] Although the above has been explained using a silica-based planar lightwave circuit as an example, similar issues exist in optical semiconductor waveguides such as lasers and photodetectors, ferroelectric waveguides such as LiNbO3, and silicon waveguides using silicon as a waveguide material.

[0011] The present invention provides an optical circuit in which the refractive index profile of the upper clad finally formed in the upper clad deposition step is adjusted based on measurement data measured in a step prior to the upper clad deposition step.

[0012] One aspect of the present invention is a method for manufacturing an optical circuit having a glass film produced by a glass film formation method using a flame deposition method, the method comprising: forming a lower clad First Process and 、 Depositing the core film Second and forming a core pattern by photolithography. Third The process and In the steps subsequent to the first step, the second step, and the third step, An upper clad is formed on the core pattern. Fourth In the method for manufacturing the optical circuit, Fourth In the process, a) The above First Process in of a) a refractive index distribution of the lower cladding in the wafer plane, b) a refractive index distribution and a film thickness of the core film in the second step, and c) an in-plane distribution of a width dimension of the core pattern in the third step. The method for manufacturing an optical circuit is characterized in that the refractive index profile of the upper cladding is adjusted based on measurement data about the upper cladding or data calculated from the measurement data.

[0014] The upper cladding may have a refractive index profile adjusted to meet desired circuit characteristics in a silica-based planar lightwave circuit (an optical circuit formed by a silica-based planar lightwave).

[0015] The upper cladding may have a refractive index profile adjusted so that the effective refractive index of the optical waveguide is constant within a plane.

[0016] The upper cladding may be index-tuned with P2O5 and / or B2O3.

[0017] The refractive index adjustment of the upper cladding may be done by doping with GeO2, TiO2, Ta2O5, HfO2, ZrO2, or the like.

[0018] The present invention also provides an apparatus for manufacturing an optical circuit having a glass film produced by a glass film formation method using a flame deposition method, the apparatus comprising a first apparatus for forming a lower clad film, a second apparatus for forming a core film, a third apparatus for forming a core pattern by photolithography, and a fourth apparatus for forming an upper clad film on the core pattern in a step subsequent to steps performed by the first apparatus, the second apparatus, and the third apparatus, the apparatus measuring manufacturing condition parameters that affect the refractive index distribution in the core pattern of the optical circuit in a step performed by the third apparatus, Based on the measured data, The process by the fourth device Before The refractive index distribution of the upper cladding is adjusted, and the manufacturing condition parameters are RF power reading, mass flow meter reading, optical emission detector reading (wavelength), optical emission detector reading (intensity), and Vacuum Gauge Reading By The optical circuit may be manufactured by an optical circuit manufacturing apparatus having the above-mentioned features. [Brief description of the drawings]

[0019] [Figure 1] 1A to 1C are diagrams illustrating a manufacturing process of an optical waveguide. [Diagram 2] 1A to 1C are diagrams illustrating a method for manufacturing an optical device according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a generalized block diagram of a feedforward system according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram of data processing according to an embodiment of the present invention. [Diagram 5] FIG. 1 is a diagram showing a dry etching apparatus according to an embodiment of the present invention. [Figure 6] FIG. 1 is a schematic diagram of a Flame Hydrolisys Deposition (FHD) apparatus for depositing glass. [Figure 7]FIG. 1 illustrates the deposition of glass particles on a wafer. [Figure 8] FIG. 1A is a diagram showing the dependency of the effective refractive index on the change in the waveguide core width, and FIG. 1B is a diagram showing the dependency of the effective refractive index on the absolute value of the refractive index of the cladding layer and the cladding refractive index. [Figure 9] 1A is a diagram showing lattice-like points selected as representative points within a wafer, and FIG. 1B is a diagram showing points on polar coordinates (r, θ) selected as representative points within a wafer. [Figure 10] 1A is a diagram showing an optical circuit pattern for compensating for the distribution of refractive index and film thickness, and FIG. 1B is a diagram showing circuit patterns of arrayed waveguide gratings with different optical path differences dL. [Figure 11] 1A is a diagram showing an example of depositing glass particles on a wafer, and FIG. 1B is a diagram showing an example of adjusting the gas flow rate of a burner. [Figure 12] FIG. 11 is a diagram showing an arrayed waveguide grating according to a third embodiment of the present invention. [Figure 13] 1A is a diagram showing the arrangement of reticles, and FIG. 1B is a diagram showing the thickness of the arrayed waveguide of each reticle pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0021] (Basic configuration) A manufacturing method according to an embodiment of the present invention measures the components or characteristics of an optical device formed in one step of the manufacturing process at that point in time, and adjusts or corrects the manufacturing conditions for subsequent steps based on the measured data (hereinafter, this method is referred to as a "feedforward system"). The feedforward system makes it possible to obtain desired optical characteristics for the final optical device, such as by suppressing variations in the optical characteristics of the optical device.

[0022] 2 is a diagram for explaining an example of a method for manufacturing an optical waveguide according to an embodiment of the present invention. The feedforward system performs "measurement" of components of an optical device formed in one process, and performs "optical property estimation" based on the measurement results by optical property estimation process 21. Then, based on the estimation results, "control" of the post-process is performed by process control process 22.

[0023] For example, the refractive index and thickness of the lower cladding film formed in the lower cladding deposition process 1, and the refractive index and thickness of the core layer deposited in the core deposition process 2 are "measured." Based on the measurement results, the final optical characteristics of the device fabricated with standard (nominal) design values ​​are estimated. Then, based on this estimation, the etching strength or time is "controlled" in the subsequent etching process 6.

[0024] Specifically, based on the "measured" film thickness and refractive index of the core layer and the refractive index of the cladding film, the ideal core width of the pattern to satisfy the performance required for the optical device is estimated (predicted). Then, in the etching process 6, etching is performed based on this predicted value. For example, if the predicted information indicates that the standard (nominal) design value will result in a "wide waveguide width after core processing, and the desired performance cannot be satisfied," a correction is made in the etching process to narrow the core width. Possible adjustment methods at this time include lengthening the etching time or increasing the etching strength to make the core width narrower than the standard (nominal) value. Furthermore, the core width and step in the waveguide pattern formed in the etching process 6 are "measured," and based on the measurement results, the refractive index of the upper cladding film formed in the upper cladding deposition process 8 is "controlled," and the optical properties of the optical waveguide finally obtained can be adjusted.

[0025] As described above, in the feedforward system of the present embodiment, among a plurality of processes for manufacturing an optical device, during or after a process in a previous process, the shape, characteristics, etc. of components of the formed optical device are measured, and based on the measurement results, the manufacturing conditions in subsequent processes are adjusted or corrected so that the performance of the finally completed device satisfies the desired conditions.

[0026] FIG. 3 is a diagram generally showing a feedforward system according to an embodiment of the present invention. The feedforward system includes a manufacturing procedure of an optical device consisting of M processes, and the optical device to be manufactured is carried out in the order of process 1, process 2 ···, process i, ··· process j, ··· process M. Here, when i < j, process j is a process that is temporally later than process i. The feedforward system includes a measurement data processing unit 31 and a control data processing unit 32. The measurement data processing unit 31 executes the optical characteristic estimation process 21 described above with reference to FIG. 2, and the control data processing unit 32 executes the process control process 22. The measurement data processing unit 31 and the control data processing unit 32 can be in the form of a computer configured to have a CPU, a RAM, a ROM, and the like.

[0027] In FIG. 3, the solid line indicates the flow according to the process of the object to be manufactured. Also, the broken line indicates the measurement data obtained by "measurement" in each process, and the alternate long and short dash line indicates the control data for "control" for each process, respectively. Thus, in the feedforward system of the present embodiment, in process i, measurement data is acquired from the manufacturing apparatus or its measurement apparatus related to the manufacturing, and transferred to the measurement data processing unit 31. The measurement data processing unit 31 predicts the shape or characteristics of the components of the optical device formed in process i based on the measurement data. Alternatively, based on the measurement data, the optical characteristics of the optical device finally obtained in process i may be predicted.

[0028] The predicted value derived by the measurement data processing unit 31 is passed to the control data processing unit 32. The control data processing unit 32 determines the manufacturing conditions for process j, which is a subsequent process, based on the predicted value. When process j is executed, the control data processing unit 32 supplies control data for process j to be set in the manufacturing equipment according to the determined manufacturing conditions. The control data based on the previous process supplied when executing the subsequent process j may be only control data based on the previous process i, or may be multiple types of control data based on several of the previous processes. The form of the control data is naturally determined according to conditions such as the actually configured manufacturing equipment and the object to be manufactured.

[0029] Example 1 A specific example of the waveguide manufacturing using the above-mentioned feedforward system will be described below. The following example relates to a configuration for determining control data for the upper cladding deposition step 8 (step k) based on measurement data obtained in the etching step 6 (step i).

[0030] Fig. 4 is a diagram showing a manufacturing system according to this embodiment, which shows only the etching process 6 as process i and the upper cladding deposition process 8 as process k in the basic configuration system shown in Fig. 3, as well as the measurement data processing unit and the control data processing unit. The etching process 6 is performed by a dry etcher 1013, and the time series values ​​W(t), F1(t), F2(t), L(t), P(t), and V(t) of the readings of each measuring device measured during this etching process are transmitted to a measurement data processing unit 31. The measurement data processing unit 31 calculates the optical characteristic λ of the optical device based on each time series value. nom The prediction is made by calculating a nominal model of (x, y) according to Equation 1. Furthermore, the control data processor 32 generates control values ​​for the FHD method in the upper cladding deposition process 8 based on the predicted values ​​of the optical characteristics by the measurement data processor 31. Then, the FHD device 2001 performs the FHD method based on the generated control values ​​to deposit the upper cladding.

[0031] FIG. 5 is a schematic diagram showing the dry etching apparatus 1013 shown in FIG. 4. The dry etching apparatus 1013 performs patterning of the core of the optical waveguide. In FIG. 5, a wafer 1000 to be processed is placed on an RF electrode 1002 placed inside a vacuum chamber 1001 of the dry etching apparatus 1013. On the top of the RF electrode 1002, another RF electrode 1003 facing the RF electrode 1002 is placed, and an RF signal is supplied from an RF power source 1004. An RF power meter 1005 is placed on the RF electrode 1002, and the RF power is observed. In addition, connection pipes 1006 and 1007 are connected to the vacuum chamber 1001, and are connected to cylinders C1 and C2 via valves 1008 and 1009, mass flow meters MFM1 and MFM2, and mass flow controllers MFC1 and MFC2, respectively. An etching gas is supplied to the vacuum chamber 1001 from the cylinders C1 and C2. As etching gas, active gas such as CF or SF, or inert gas such as Ar may be used, and the two may be mixed. Here, an example of two cylinders, C1 and C2, is shown, but the number of cylinders is optional. Furthermore, an observation window 1010 is provided in the vacuum chamber 1001, and the internal plasma state is observed through the observation window 1010 by an optical emission detector 1011. In addition, a vacuum gauge 1012 is provided in the vacuum chamber 1001 to measure the degree of vacuum inside the vacuum chamber 1001. The readings of each measuring device are defined as follows: RF power reading: W Mass flow meter readings: F1 and F2 Emission detector reading: (wavelength) L, (intensity) P Vacuum gauge reading: V

[0032] The core of the optical waveguide is processed by the dry etching device 1013 shown in Fig. 5, but the amount of processing and the distribution within the wafer surface depend on the RF power, the flow rate of the supply gas, the state of the plasma, and the degree of vacuum. Factors that cause the uneven distribution within the wafer surface include, for example, that fresh gas is supplied to the area close to the supply gas connection pipes 1006 and 1007, whereas degraded gas contributes to the etching near the vent port not shown in Fig. 5. Another factor is that the edge effect of the electric field becomes prominent at the ends of the RF electrodes 1002 and 1003, causing the plasma generation to differ.

[0033] The measurement results from the dry etching process can be fed forward to the FHD process, for example.

[0034] The measurement data obtained as described above is subjected to the following processing by the measurement data processing unit 31. Specifically, the measurement data processing unit 31 calculates the optical characteristic λ of the optical device based on the time series value of each measurement data. nom The nominal model of (x, y) is calculated according to the following equation 1 to make a prediction.

number

[0035] In Equation 1, x and y are coordinates within the wafer surface. nom are optical characteristics, such as the transmission center wavelength, crosstalk, polarization dependent loss, wavelength dependent loss, polarization dependent transmission wavelength, chromatic dispersion, and polarization mode dispersion in the case of an arrayed waveguide grating.

[0036] Nominal model f xy (W, F1, F2, L, P, V) can be expressed as the sum of powers of each parameter. In other words, the average value of the optical characteristics over multiple K-1 manufacturing cycles prior to the Kth manufacturing cycle is expressed as λ Avg (x, y), the average of the measured values ​​is W avg , F 1avg , F 2avg , L avg , Pavg ,V avg When

number

[0037] Here, each coefficient C w , C F1 , C F2 ,C L , C P , C V is determined for each coordinate (x, y) within the wafer. In addition, since it can be assumed that the deviation of each measurement value in the Kth manufacturing process from the average of the previous measurements is small, each sum can be calculated by taking the first-order terms. In addition, it is assumed here that the change from the average value of each measurement value is small and that they are independent of each other, but the formula f of the nominal model assuming that each is dependent on each other can be used. xy (W, F1, F2, L, P, V) may be defined. For example, if the gas flow rates F1 and F2 change, the vacuum level V also changes, so the product of the two or light related to V(F1, F2) may be included. In addition to the power sum, coefficients may be calculated using machine learning, etc.

[0038] The above coefficients may be calculated using AI / machine learning based on the results of inspections performed during the optical waveguide manufacturing process, and the final device characteristics may be predicted. Data consisting of a set of process inspection results and device characteristics of optical waveguides manufactured up to that point can be used as training data for the AI.

[0039] In addition, in the embodiment described above, the RF power reading W, the mass flow meter readings F1 and F2, the optical emission detector reading (wavelength) L, (intensity) P, and the vacuum gauge reading V are the measurement items, but other items, such as the optical emission spectrum obtained from the optical emission detector, temperature, humidity, air pressure, weather, the timing of equipment overhauls, and the number of processing operations since overhaul, and other measurement values ​​may be added.

[0040] An example using FHD is shown below.

[0041] FIG. 6 is a schematic diagram showing the FHD (Flame Hydrolisys Deposition) apparatus 2001 shown in FIG. 4. In FIG. 6, a wafer 2008 is placed on a turntable 2002 that rotates at an angular velocity Ω. A burner 2003 is placed above the turntable 2002 and is connected to valves 2005, 2006, and 2007 via a pipe 2004. The valves 2005, 2006, and 2007 are connected to cylinders C21, C22, and C23 via mass flow meters MFM21, MFM22, and MFM23, and mass flow controllers MCF21, MCF22, and MCF23, respectively. The cylinders C21, C22, and C23 are filled with raw material gases such as SiCl4, BCl3, and POCl3, and the flow rates of the raw material gases are adjusted and mixed by the mass flow controllers MCF21, MCF22, and MCF23, and the raw material gases are supplied to the burner 2003. BCl3 has the effect of lowering the refractive index of glass, while POCl3 has the effect of raising the refractive index of glass.

[0042] Oxygen and hydrogen (not shown) are simultaneously supplied to the burner. The raw gas is hydrolyzed in the oxyhydrogen flame to generate glass particles, which are deposited on the wafer. The burner 2003 moves in the radial direction above the turntable 2002 rotating at an angular velocity Ω. Thus, as shown in FIG. 7, the glass particles are deposited on the wafer 2008 over an area φ of about the inner diameter of the tube of the burner 2003 per rotation of the turntable 2002.

[0043] Here, the control value is Turntable rotational angular velocity: Ω Mass flow meter readings: F21, F22, F23 Burner radial movement speed: v These control values ​​are observable. The following description assumes that the upper cladding layer is formed by the FHD method after the core processing.

[0044] Optical properties λ' of the optical device in the upper cladding deposition step 8 nomThe nominal model for (x, y) is

number

[0045] Here, x and y in equation (3) are coordinates within the wafer surface. nom are optical characteristics, such as the transmission center wavelength, crosstalk, polarization dependent loss, wavelength dependent loss, polarization dependent transmission wavelength, chromatic dispersion, and polarization mode dispersion for an arrayed waveguide grating. For an optical switch, the optical characteristics include loss, extinction wavelength, crosstalk, and polarization dependent loss.

[0046] Nominal model f' xy (Ω, F 21 , F 22 , F 23 , v) can be expressed as the sum of powers of each parameter. That is, the average value of the optical characteristics over multiple K-1 manufacturing cycles prior to the Kth manufacturing cycle is expressed as λ Avg (x, y), the average of the measured control values ​​is Ω avg , F 21avg , F 22avg , F 23avg , v avg When

number

[0047] As mentioned above, the nominal model equation can be in a form other than the sum of powers. In the nominal model equation, Ω, F 21 , F 22 , F 23 , v is both a measured value and a controlled value.

[0048] The measurement data including the measurement values ​​and the control data including the control values ​​may be configured to be stored in a database.

[0049] The control data processing unit 32 generates the control data as follows. For example, in the case of a quartz-based planar lightwave circuit, as shown in FIG. 1, the upper cladding 19 is deposited and embedded after the core processing. Therefore, the optical characteristic λ of the optical device obtained from the nominal model at the time of the core processing by the above-mentioned etching process 6 is nom Nominal model λ′ of optical properties in (x, y) and upper cladding deposition nom (x, y) at each position (x, y) on the wafer surface

number

[0050] The control values ​​Ω and F of the FHD method during deposition of the upper cladding 19 are 21 , F 22 , F 23 , v. This generates the desired optical characteristic λ of the optical device that has no distribution in the optical characteristic. target You can get (x, y).

[0051] In feedforward correction, it is sufficient to control the controllable parameters (Ω, F21, 22, ..., etc. above) so as to satisfy equation (5). The above nominal model equation is expressed to express controllability. In other words, the left side of equation (5) is the evaluation function, and by substituting equations (1) and (3) into equation (5), the evaluation function is expressed as the sum of the powers of the controllable parameters for each process. Each control parameter can be adjusted so that this evaluation function becomes zero during manufacturing. When controlling, it is acceptable to select the control parameters that most efficiently satisfy the evaluation function. The method described below is used to obtain the data to be output. In deriving the control parameters to be output, first, the measured values ​​of the known control parameters obtained in the etching process 6 are substituted into the formula (5) obtained by substituting the formulas (1) and (3). The control parameter Ω in the upper cladding deposition process 8 is avg , F 21avg , F 22avg , F 23avg , v avgare the variables in the equation, and each parameter can be determined using methods such as hill climbing, genetic algorithms, particle swarm optimization, etc. If equation (3) is linear, it can also be determined using simple methods such as linear programming.

[0052] A specific description will be given below. For example, the central wavelength of the arrayed waveguide grating is

number

[0053] where n eff is the effective refractive index of the arrayed waveguide, dL is the optical path length difference between the waveguides of the arrayed waveguide, and m is the diffraction order. In other words, the central wavelength of the arrayed waveguide grating is the effective refractive index n eff It depends on the effective refractive index n eff becomes larger as the width and height of the waveguide core increase, and becomes larger as the refractive index of the cladding increases. Figure 8(a) is a diagram showing the dependency of the effective refractive index on the waveguide core width. Figure 8(b) is a diagram showing the change in the absolute value of the refractive index of the cladding layer and the dependency of the effective refractive index on the cladding refractive index. For example, if it is predicted by calculation from the nominal model during reactive ion etching that the desired effective refractive index has increased as the core width increases in the core processing process, then the refractive index of the upper cladding can be reduced by, for example, adjusting the source gas during deposition of the upper cladding by the FHD method. The right-hand side of equation (3) of the nominal model for the FHD method,

number

[0054] This is accomplished by increasing the flow rate of BCl3, which lowers the refractive index of the glass.

[0055] Although the method of compensating for the deviation of the wafer in-plane distribution from the target value in core processing during upper cladding deposition has been described as an example, it is clear that this is also possible between other processes. For example, the distribution during core film deposition can be corrected in the subsequent processes, such as the photolithography process, the core processing process, and the upper cladding film formation process (upper cladding film formation process 8), and the distribution in photolithography can be corrected in the core processing process or the upper cladding film formation process. Furthermore, it is clear that the distribution during core deposition can be corrected by combining the photolithography process and core processing.

[0056] Here, the central wavelength of the arrayed waveguide grating has been taken as an example for explanation, but crosstalk and polarization dependency may be similarly corrected as optical characteristics, or the extinction wavelength and loss of an optical switch using a Mach-Zehnder interferometer may be corrected. Furthermore, multiple indicators among these may be corrected.

[0057] In addition, in correcting the oscillation wavelength of a DBR (Distributed Bragg Reflector) type semiconductor laser, the oscillation wavelength is the Gragg grating wavelength λ0.

number

[0058] Similarly, n eff It is also possible to correct between processes. In the manufacturing process of a semiconductor laser, the refractive index of the epitaxially grown InP waveguide varies depending on its composition. The deviation from the absolute value of the refractive index that occurs in the growth process and the distribution within the wafer surface can be corrected by using the etching parameters W, F1, F2, L, P, and V as control values.

[0059] In the above description, FHD was used as an example, but other methods such as CVD (Chemical Phase Vapor Deposition) and PVD (Physical phase vaper deposition) may also be used. In methods such as CVD and PVD, a glass film is formed all at once on the entire wafer without scanning the wafer position with a burner. In this case, as described above, the optical characteristics may be corrected based on Equation (1) for each device calculated from the time-series values W(t), F1(t), F2(t), L(t), P(t), and V(t) of the readings of each measuring device of the manufacturing apparatus.

[0060] In this embodiment, in a manufacturing system for an optical device including M (M is an integer of 2 or more) processes, where M is an integer of 2 or more, when i is a natural number, j is an integer of 2 or more, and i < j, there is at least one measurement data processing means for inputting and processing measurement data from a manufacturing apparatus or a measuring device in the i-th process, and control data processing means for processing the measurement data and outputting it to the manufacturing apparatus in the j-th process. An optical device manufacturing system is disclosed. By this optical device manufacturing system, in the manufacture of an optical waveguide component including a plurality of processes, in a certain process (the j-th process), the conditions of the process (the j-th process) can be adjusted using measurement data from a manufacturing apparatus or a measuring device in a process (the i-th process) before the process.

[0061] (Embodiment 2) In this embodiment, the correction of the upper cladding (overclad) will be described.

[0062] In photolithography, the target pattern width may not be the desired width due to factors such as the in-plane distribution of resist film thickness, the distribution of development caused by deterioration of the developer due to pattern density, and the distribution of illuminance within the surface of the exposure device. Deviations from the target value of the circuit pattern width due to these factors can be corrected in subsequent processes. That is, in the manufacturing process of the standard quartz-based planar lightwave circuit in Figure 1, the distribution of effective refractive index can also be corrected by correcting the distribution of effective refractive index in the film formation process (upper cladding deposition process) 8 of the upper cladding 19.

[0063] In this embodiment, the in-plane distribution of the width dimension of the core pattern 18 is measured after removing the photoresist pattern 17 in step 7 in Fig. 1. After measuring the width distribution, the distribution of the effective refractive index explained in Example 1 is obtained, and the upper cladding 19 formed in step 8 is made to have a refractive index distribution so as to correct the distribution.

[0064] Figure 6 is a diagram showing the deposition of glass particles on a wafer. In the FHD method shown in Figure 6, the wafer is placed on a turntable that rotates in the Ω direction, and a burner that emits glass particles moves in the v direction. That is, in one revolution of the turntable, the glass particles are deposited along the trajectory shown in Figure 6. Glass is deposited by adjusting the flow rate of the source gas over time so as to compensate for the distribution of the effective refractive index calculated earlier with respect to this trajectory.

[0065] As shown in Fig. 11(a), the burner deposits glass particles in the area of ​​spot 60001 at a certain moment according to its diameter, and if the position of the burner spot in the radial direction is r, the spot 60001 moves as shown in the figure at a moving speed of rΩ according to the rotation of the turntable. Here, referring to Fig. 8, the gas flow rates MFM21 to MFM23 are adjusted.

[0066] FIG. 11(b) is an example showing the adjustment of the gas flow rate. The horizontal axis indicates the position of the burner spot, which is set according to time. The vertical axis indicates the gas flow rate (sccm). The dotted line in FIG. 11(b) is the effective refractive index of the waveguide predicted from FIG. 8 in the process before the deposition of the upper cladding. As shown by the dotted line in FIG. 11(b), the effective refractive index is minimized at the position P of the burner. The gas flow rate during the deposition of the upper cladding is adjusted, and the effective refractive index is increased at the position P by, for example, adjusting the flow rate of the raw material gas to increase the concentration of P2O5 or decrease the concentration of B2O3. At the position where the effective refractive index becomes high, the concentration of P2O5 may be decreased or the concentration of B2O3 may be increased. The distribution of the effective refractive index may be corrected by adding GeO2, TiO2, Ta2O5, HfO2, or ZrO2 and adjusting the concentration. The refractive index of the upper cladding may be decreased by adding fluorine.

[0067] In this embodiment, the refractive index distribution of the upper cladding is adjusted based on the in-plane distribution of the refractive index distribution of the lower cladding and the core film, the film thickness of the core film, and the effective refractive index of the optical waveguide (calculated from the width of the core pattern). This optical circuit is manufactured by a glass film formation method using a flame deposition method, and is manufactured by a process of forming a lower cladding, a process of forming a core film, and a process of forming a core pattern by photolithography. The in-plane distribution of the effective refractive index of the optical waveguide calculated from the refractive index distribution of the lower cladding in the wafer plane, the refractive index distribution and film thickness of the core film, and the width of the core pattern is fed forward to the manufacture of the upper cladding, thereby reducing the distribution (bias) of characteristics in the wafer plane of a quartz-based planar lightwave circuit. Example 3

[0068] The effective refractive index may be adjusted by providing an in-plane distribution to the refractive index of the upper cladding so that the circuit characteristics within the wafer plane are maintained at the desired values. As described above, it is possible to control the in-plane distribution of the upper cladding during deposition of the upper cladding 8. Therefore, the refractive index of the upper cladding may be controlled to obtain desired optical circuit characteristics.

[0069] FIG. 12 is a diagram according to this embodiment. FIG. 12 shows an arrayed waveguide grating, which is composed of an input waveguide 11001, an input slab waveguide 11002, arrayed waveguides 11003-11007, an output slab waveguide 11008, and an output waveguide 11009. Although FIG. 12 shows an example in which there are five arrayed waveguides 11003-11007, the number is not limited to this number. In the arrayed waveguide grating of FIG. 12, the arrayed waveguides 11003-11007 are all formed to have the same length. That is, the path length difference is zero (path length difference is defined as the length in the layout, and optical path length difference is defined as the optical length). With reference to the graph of FIG. 8(b), deposition is performed while adjusting the refractive index of the upper cladding so that the effective refractive index of the arrayed waveguide 11003 is low and the effective refractive index of the arrayed waveguide 11007 is high. As a result, the optical path length difference between the arrayed waveguides becomes longer as the array number increases, making it possible to realize the wavelength demultiplexing function that is the desired function of the arrayed waveguide grating.

[0070] (Another example 1) As a method using the secondary measurement value, the following detailed method (called selective exposure) will be explained. Here, an example of a quartz-based planar lightwave circuit will be explained.

[0071] In the above embodiment 1, an example has been shown in which the measurement data processing unit predicts optical characteristics from measurement data of the control value of the manufacturing equipment, and the control data processing unit generates measurement values ​​of control data for controlling the manufacturing equipment for the next process and thereafter. However, as will be described below, for wafers in process between each manufacturing process, it is also possible to obtain wafer characteristic data separately using a measurement device, and perform correction using a manufacturing device or method that performs correction.

[0072] Here, we will explain the manufacturing method of a silica-based planar lightwave circuit by referring to the manufacturing process of the optical waveguide device shown in Figure 1. However, as will be described later, it is clear that the method can be applied to other materials, such as semiconductors such as InP and ferroelectric waveguides such as LiNbO3, as long as the optical waveguide is made of a cladding and a core.

[0073] Silica-based planar lightwave circuits are mechanically and chemically stable and are used in functional devices such as wavelength filters and optical switches using interferometers. A representative interference device is the arrayed waveguide grating. The central wavelength of the arrayed waveguide grating is:

number

[0074] The manufacturing stability is expressed as the effective refractive index n eff In the FHD method used in the deposition of the core 13 in step 2 of FIG. 1, a hydrolyzed raw material gas is blown by a burner onto a wafer placed on a rotating turntable to bake glass soot. During this process, fluctuations in the film thickness and refractive index occur within the wafer surface due to various factors such as fluctuations in the environmental temperature and the rotation speed of the turntable, and discretization and fluctuations in the burner trajectory. Therefore, the effective refractive index n eff The effective refractive index n eff depends on the bulk refractive index of the core 13, lower cladding 12, and upper cladding 19, and the dimensions and shape of the processed core pattern 18, but since most of the optical energy is confined inside the core pattern 18, it is greatly affected by the refractive index and size of the processed core pattern 18.

[0075] In this embodiment, a method is described in which the distribution of the film thickness and the refractive index of the wafer is measured in the plane after the core 13 is formed using a measuring device, the measurement data is acquired, and the distribution is corrected in the photolithography process in step 4. In general, an optical waveguide device is manufactured on a wafer by arranging a plurality of chips Shot 1 to 16 on the wafer. Since the core 13 has a distribution of the refractive index and the film thickness over the wafer plane, each chip has optical characteristics that reflect the distribution. Therefore, in this embodiment, as shown in FIG. 10(a), the distribution of the optical characteristics is corrected by exposing the patterns A to I of the optical circuit that compensates for the distribution of the refractive index and the film thickness at each position. It is also possible to perform the correction using a separate manufacturing device that performs the correction.

[0076] First, after the narrow core film in step 2, the thickness and refractive index distribution of the core film are measured by a method such as ellipsometry. For the measurement, as shown in Figures 9(a) and (b), points on a lattice pattern in the wafer or points on the polar coordinates (r, θ) are selected as representative points. Next, referring to the representative points where the refractive index and thickness of the core 13 were measured, the approximate equations n(x, y) and t(x, y) for the thickness and refractive index are generated using the following equations.

number

[0077] Here, a k ,b k ,c k ,d k is a coefficient, which is found using the least squares method, etc. When correcting the optical characteristics for each chip, n(x, y) and t(x, y) at each placement location are calculated using the above approximation formula. For example, if an arrayed waveguide grating is assumed to be the type of optical circuit to be fabricated, the arrayed waveguide portion (x p ,y p ) in n(x p ,y p ),t(x p ,y p ) is required.

[0078] Below are three methods for correcting the effective refractive index.

[0079] In the first distribution correction method, a pattern with different optical path length differences of the arrayed waveguide is arranged. Since the effective refractive index of the optical waveguide is largely dependent on the refractive index of the core pattern 18 as described above, in the first approximation, the refractive index of the bulk of the core should be mainly considered. Therefore, the effective refractive index is determined by the arrayed waveguide position (x p ,y p ) effective refractive index n eff (x p ,y p ) is the nominal value of the finished width of the core pattern 18. norm As

number

[0080] and n(x, y), t(x, y), w norm It is expressed as a function of the function

number

[0081] is a function expressed by the Marcatelli method, the imaginary axis propagation method, the equivalent refractive index method, etc. eff (x p , y p ) for the target range of the central wavelength of the arrayed waveguide grating, λ norm When ±δλ,

number

[0082] If the arrayed waveguide pattern has an optical path length difference dL between the arrays, an arrayed waveguide grating with a desired center wavelength can be obtained. Therefore, as shown in FIG. 10(b), a number of reticles having circuit patterns of arrayed waveguide gratings with different optical path length differences dL (for example, dL1, dL2, dL3, dL4, etc.) of the arrayed waveguides are prepared, and in step 4, the (x p , y p ) can be selected and exposed to obtain the target characteristics of the central wavelength of the desired arrayed waveguide grating.

number

[0083] It is sufficient to select and expose an arrayed waveguide grating pattern having an optical path length difference dL of the arrayed waveguides that satisfies the following equation: In this embodiment, the arrayed waveguide grating pattern is selected and exposed.

[0084] Incidentally, it is preferable to prepare a plurality of circuit patterns such that the ranges of the optical path length difference dL of the arrayed waveguides overlap to some extent, taking into consideration the influence of manufacturing fluctuations in the subsequent processes. For example, when dλ is a positive value and the target central wavelength range is

number

[0085] In this case, the ideal (nominal) effective refractive index is

number

[0086] The optical path length difference dL0 of the arrayed waveguide when the core film is obtained is

number

[0087] Then, σ>0.

number

number

number

number

[0088] It is preferable to arrange, on a reticle, a pattern of an arrayed waveguide grating having an optical path length difference such that:

[0089] In the second correction method, a circuit pattern with different waveguide widths is arranged. As described above, the effective refractive index n eff (x p ,y p ) is (x p ,y p ) in n(x p ,y p ),t(xp ,y p ) and the width W. Therefore, as shown in Fig. 13, a circuit pattern having an arrayed waveguide width of width W such that the effective refractive index becomes a desired value (constant value) may be exposed. In this case as well, multiple circuit patterns having multiple arrayed waveguide widths may be prepared and selected.

[0090] The second correction method also makes it possible to correct optical characteristics other than the central wavelength mentioned above. In general, the clarity of a multi-beam interferometer such as an arrayed waveguide grating is limited by the phase error between each beam. In other words, the phase error determines the crosstalk performance of different wavelengths in optical communications. Therefore, if there is a distribution of the effective refractive index within the region where the arrayed waveguide exists, the internal point (x pi ,y pi ) may be provided with an arrayed waveguide grating having a width that corrects the deviation of the effective refractive index from a desired value.

[0091] Fig. 13 shows a photomask pattern in which an arrayed waveguide grating for compensating for crosstalk performance is arranged. Fig. 13(a) shows the arrangement of the reticle. Fig. 13(b) shows the thickness of the arrayed waveguide of each reticle pattern.

[0092] A number of circuits with different arrayed waveguide distributions are arranged on the photomask. As shown on the right side of the figure, arrayed waveguide gratings with different waveguide width distributions are arranged in a 3×3 matrix with respect to the arrayed waveguide numbers. In the matrix, the arrayed waveguide gratings on the left column have the arrayed waveguides with the lower numbers wider, the arrayed waveguide gratings on the right column have the arrayed waveguides with the higher numbers wider, and the arrayed waveguide gratings on the middle column are laid out so that the waveguide at the center of the arrayed waveguide is wider and has a quadratic distribution. Furthermore, the upper row has a large absolute value of the distribution slope, the middle row has a medium slope, and the lower row has a small slope. Here, a 3×3 combination has been described, and the arrayed waveguides with linear and quadratic slopes in the width are described, but they may be arranged on the photomask as a combination with a width distribution expressed by a general polynomial.

[0093] The third method of correcting the distribution is to adjust the exposure time to correct the distribution. In general, the width of the waveguide can be changed by changing the exposure time, development time, and the concentration of the developer. Therefore, for each point (x p , y p The exposure time may be changed for each arrayed waveguide grating circuit present in the wafer. In addition, when it is desired to change the width of the waveguide over the entire wafer, for example when the refractive index of the core film is formed to be large or small over the entire wafer, it is also possible to adjust the width of the waveguide over the entire wafer by changing the concentration of the developer or the development time.

[0094] The above explanation was given using an arrayed waveguide grating as an example, but it can also be applied to matrix switches that use two-beam interference, such as Mach-Zehnder interferometers, and interferometers such as filters, such as Bragg gratings. In addition, in spot size converters, which are used to reduce the connection loss between optical waveguides and optical fibers, the field system of the lightwave affects its characteristics. Since the effective refractive index is one of the parameters of the field system, it is clear that the above method is applicable.

[0095] The refractive index distribution of the lower cladding 11 in the wafer plane, the refractive index distribution of the core film, and / or the film thickness, and the measured data of the in-plane distribution of the effective refractive index of the optical waveguide calculated from the width of the core pattern 18, can be used to adjust the refractive index distribution of the upper cladding 19 in the subsequent deposition process 8 of the upper cladding 19.

Claims

1. An apparatus for manufacturing an optical circuit having a glass film, comprising: a first device for depositing a lower cladding; a second device for depositing a core film; a third device for forming a core pattern by photolithography; a fourth device for depositing an upper clad on the core pattern in a process subsequent to the processes performed by the first device, the second device, and the third device; In the optical circuit device having the above structure, In the fourth apparatus, a) a refractive index distribution in the wafer surface of the lower cladding in the process using the first device; b) the refractive index profile and film thickness of the core film in the process using the second device, and c) the refractive index distribution of the upper cladding is adjusted based on measurement data on an in-plane distribution of a width dimension of the core pattern in the process by the third device or data calculated from the measurement data. Optical circuit manufacturing equipment.

2. 2. The apparatus for manufacturing an optical circuit according to claim 1, wherein the refractive index profile of said upper cladding is adjusted so as to satisfy desired circuit characteristics in said optical circuit formed by a silica-based plane lightwave.

3. 2. The optical circuit manufacturing apparatus according to claim 1, wherein the refractive index profile of the upper cladding is adjusted so that the effective refractive index of the optical waveguide is constant within a plane.

4. The refractive index of the upper cladding is P 2 O 5 and B 2 O 3 4. The optical circuit manufacturing apparatus according to claim 1, wherein either one or both of the above is adjusted.

5. The refractive index of the upper cladding is GeO 2 , TiO 2 , Ta 2 O 5 , HfO 2 , or ZrO 2 5. The optical circuit manufacturing apparatus according to claim 1, wherein the optical fiber is adjusted by adding

6. A method for manufacturing an optical circuit having a glass film, comprising the steps of: A first step of depositing a lower cladding; a second step of depositing a core film; a third step of forming a core pattern by photolithography; a fourth step of depositing an upper clad on the core pattern in a step subsequent to the first step, the second step, and the third step; In the method for manufacturing an optical circuit, In the fourth step, a) the refractive index distribution of the lower cladding in the wafer plane in the first step; b) the refractive index profile and film thickness of the core film in the second step, and c) the refractive index distribution of the upper cladding is adjusted based on measurement data on an in-plane distribution of a width dimension of the core pattern in the third step or data calculated from the measurement data. A method for manufacturing optical circuits.

7. 7. The method for manufacturing an optical circuit according to claim 6, wherein the refractive index profile of the upper cladding is adjusted so as to satisfy desired circuit characteristics in the optical circuit formed by a silica-based plane lightwave.

8. 7. The method for manufacturing an optical circuit according to claim 6, wherein the refractive index profile of the upper cladding is adjusted so that the effective refractive index of the optical waveguide is constant within a plane.

9. The refractive index of the upper cladding is P 2 O 5 and B 2 O 3 9. The method for manufacturing the optical circuit according to claim 6, wherein both or either one of the above is adjusted.

10. The refractive index of the upper cladding is GeO 2 , TiO 2 , Ta 2 O 5 , HfO 2 , or ZrO 2 10. The method for manufacturing an optical circuit according to claim 6, wherein the optical fiber is adjusted by adding

11. An apparatus for manufacturing an optical circuit having a glass film, comprising: a first device for depositing a lower cladding; a second device for depositing a core film; a third device for forming a core pattern by photolithography; a fourth device for depositing an upper clad on the core pattern in a process subsequent to the processes performed by the first device, the second device, and the third device; In the optical circuit manufacturing apparatus, measuring manufacturing condition parameters that affect the refractive index distribution in the core pattern of the optical circuit in a process using the third device, and adjusting the refractive index distribution of the upper cladding in a process using the fourth device based on the measured data; The manufacturing condition parameters are an RF power reading, a mass flow meter reading, an emission detector reading (wavelength), an emission detector reading (intensity), and a vacuum gauge reading. Optical circuit manufacturing equipment.

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