JP7303701B2 - Optical film thickness control device, thin film forming device, optical film thickness control method, and thin film forming method - Google Patents

Description

The present invention relates to an optical film thickness control apparatus, a thin film forming apparatus, an optical film thickness control method, and a thin film forming method. In particular, an optical film thickness control device for forming a thin multilayer film by solidifying a film forming material supplied from a film forming material supply unit such as a vapor deposition source disposed in a film forming chamber on the surface of a film forming target substrate, and a thin film forming apparatus. The present invention relates to an apparatus, an optical film thickness control method, and a thin film forming method.

2. Description of the Related Art In recent years, along with the development of optical communication technology due to the introduction of optical amplifiers and wavelength division multiplexing, the importance of optical filters has increased, and optical filters with excellent optical characteristics are in demand.
For example, a narrowband bandpass filter (hereinafter also referred to as an NBP filter) used for optical communication such as DWDM (Dense Wavelength Division Multiplexing) communication system has a structure in which an optical multilayer film is formed on an optical substrate. high wavelength selectivity, high reflectivity of light in non-selected wavelength regions, and high transmittance of light in selected wavelength regions.

The optical multilayer film that constitutes the NBP filter has a structure in which dielectric thin films having different refractive indices are laminated in multiple layers.
For example, an NBP filter is an optical multilayer in which 80 to 260 layers of Ta ₂ O ₅ thin films with a thickness of 220 to 235 nm and SiO ₂ thin films with a thickness of 250 to 260 nm are alternately laminated on an optical substrate such as quartz glass. A film is formed.
Each thin film forming the optical multilayer film is formed to have a predetermined optical film thickness. The optical thickness is defined as the product of the physical thickness of the thin film and the refractive index of the thin film, and is an important factor for satisfying the optical properties desired for the optical multilayer film.

Examples of methods for forming an optical multilayer film include vacuum deposition such as ion beam assisted vacuum deposition, molecular beam deposition, and ion plating.
Since the refractive index of a thin film depends on the type and composition of the elements that make up the thin film, for example, when forming a thin film by vacuum deposition, a thin film with a desired refractive index can be formed by appropriately selecting the composition of the vacuum deposition source. can do.
In addition, in order to obtain the desired optical film thickness in the optical multilayer film having the above configuration, it is required that the error from the design value be suppressed to 0.1% or less as the accuracy of the physical film thickness of each thin film. . For example, Patent Literatures 1 to 4 disclose a method of forming a thin film while monitoring the physical film thickness by a direct or indirect optical film thickness monitoring method.

For example, in a vacuum vapor deposition apparatus using a direct film thickness monitoring method, monitor light is projected from a light projecting unit onto a film formation target substrate during film formation of each thin film, and passes through the film formation target substrate. The monitor light is received by the light-receiving part, and the change in light transmittance due to interference is captured to monitor the film thickness of the thin film being formed.
Since the film thickness is monitored by receiving the monitor light that has passed through the film formation target substrate, this method is called a direct film thickness monitoring method.

In the indirect type optical film thickness monitoring method, during the deposition of each thin film, monitor light is projected from the light emitting and receiving unit onto the monitor substrate, reflected light from the monitor substrate is received by the light emitting and receiving unit, and light Monitor changes in reflectance.
Since the film thickness of the thin film on the substrate to be formed is estimated and monitored from changes in reflected light from the monitor substrate, this method is called an indirect film thickness monitoring method.

JP-A-2003-82462 JP-A-2002-340527 Japanese Patent Application Laid-Open No. 2002-303510 JP 2014-133926 A

Optical film thickness control is applied to film thickness control when forming an optical multilayer film, but in general, the following error factors exist in optical film thickness control.

i.e.
・Mismatch between the designed refractive index and the actual refractive index,
・Variation of deposition rate,
・Transmittance measurement error,
・random error due to noise,
・Systematic error in the measured transmittance due to vibrations, bending of the substrate due to heat during film formation, etc.
・Decrease in transmittance due to membrane absorption,
There are error factors such as

In addition, there are other control problems as follows.
Conventionally, proportional control, which is commonly used, uses the ratio of peak transmittance and stop transmittance (Final Swing) to determine whether film formation is stopped. However, there is a problem that the film thickness error becomes large. Therefore, there are restrictions on film design, selection of control wavelength, and the like.
When a film thickness error occurs in a layer in the middle of film formation, conventionally, there is no means for applying feedback to the film thickness of subsequent layers so as to correct this error.

In addition, the physical properties (for example, the refractive ^index ) of the film-forming substance change with temperature during film formation, which cannot be ignored in terms of optical control and product reproducibility. Otherwise it is difficult to ascertain good reproducibility.

INDUSTRIAL APPLICABILITY According to the present invention, error factors in film thickness control can be removed, film thickness errors can be suppressed, and film thickness errors occurring in layers during film formation can be corrected. It is possible to achieve highly accurate optical film thickness control even when the physical properties of film-forming materials change with temperature. An object of the present invention is to provide an apparatus, a thin film forming apparatus, an optical film thickness control method, and a thin film forming method.

The optical film thickness control device according to the first aspect of the present invention is a film forming device in which a film forming material supplied from a film forming material supply unit arranged in a film forming chamber is deposited to form a thin multilayer film. A light projecting unit for projecting monitor light onto a target substrate, a light receiving unit for receiving the monitor light transmitted through the film formation target substrate and outputting a received light signal, and a temperature measurement unit for measuring the temperature of the substrate during film formation. and a control unit that acquires the light transmittance of the film formation target substrate according to the light reception signal, and controls thin film deposition in association with the acquired light transmittance information, the control unit comprising: With respect to the multilayer film to be formed, the multilayer film and the substrate that have already been formed are defined as one film as an equivalent film, and the square root of the reflectance between the two substances is defined as the reflection amplitude. Employing a fitting function T related to the equivalent reflection amplitude r between the current layer, the current reflection amplitude r between the current layer and air, and the phase δ, the measured transmittance time variation during deposition is fitted to the At least one of the phase δ and the equivalent reflection amplitude r during film formation is determined by fitting in relation to the function, and the current layer is stopped so that it matches the determined physical parameter and the preset theoretical value. It is possible to determine a time and perform film formation control to stop film formation at the stop time, and to correct the film formation control based on the substrate temperature measured by the temperature measurement unit.

A thin film forming apparatus according to a second aspect of the present invention comprises a film forming chamber, a film forming material supply unit disposed in the film forming chamber, and a film forming material supplied from the film forming material supplying unit. a film formation target substrate on which a multi-layered thin film is formed; a light projecting unit for projecting monitor light onto the film formation target substrate; a temperature measuring unit that measures the temperature of the substrate during film formation; and acquires the light transmittance of the film formation target substrate according to the light reception signal, and associates the acquired light transmittance information with the thin film with respect to the multilayer film to be formed, the controller equates an already-formed multilayer film and a substrate with a certain film as an equivalent film, A fitting function that defines the square root of the reflectance between two materials as the reflection amplitude and relates it to the equivalent reflection amplitude r between the equivalent film and the current layer, the current reflection amplitude r between the current layer and air, and the phase δ. T is employed, the measured value of transmittance time change during film formation is correlated with the fitting function, and the physical parameter of at least one of phase δ and equivalent reflection amplitude r during film formation is determined, and determined The substrate temperature measured by the temperature measurement unit is capable of determining the stop time of the current layer so as to match the physical parameter obtained and the theoretical value set in advance, and stopping the film formation at the stop time. Based on this, it is possible to correct the film formation control.

Preferably, in the optical film thickness control apparatus or the thin film forming apparatus of the present invention, the control section measures the temperature change of the physical properties of the film forming material during the film formation based on the substrate temperature measured by the temperature measuring section. is corrected, and the physical parameters are recalculated in association with the corrected physical properties of the film-forming material to correct the film-forming stop time.

Preferably, the physical properties of the deposition material include refractive index.

Preferably, the control unit obtains the refractive index during film formation based on the temperature coefficient set for each film forming material, and calculates the value of the physical film thickness in film design and the obtained refractive index value during film formation. is used to recalculate the optical characteristics of the multilayer film, and recalculate at least one of at least the reflection amplitude, phase, and optical film thickness used for control, and correct the deposition stop time.

Preferably, in the optical film thickness control apparatus or thin film forming apparatus of the present invention, the control unit is given in advance a theoretical phase δ_design at the time of stopping each layer based on the film design of the multilayer film. to determine the angular velocity ω of the phase δ and the initial phase φ0. Film formation is stopped at a time that matches the given theoretical phase δ_design.

Preferably, the control unit is given a theoretical equivalent reflection amplitude at the time point when each layer is stopped based on the film design of the multilayer film, and changes the transmittance with time according to the light receiving signal during film formation. Fitting is performed in association with the fitting function to determine the equivalent reflection amplitude of the current layer during deposition of the next layer, and the absolute value of the determined equivalent reflection amplitude of the current layer during deposition of the next layer is the theoretical equivalent reflection amplitude. The stop time of the current layer is determined so as to match with , and film formation is stopped at this stop time.

Preferably, a temperature measurement unit is provided for measuring the temperature of the film formation target substrate during film formation, and the control unit measures the refractive index during film formation based on a temperature coefficient set for each film formation substance. The optical properties of the multilayer film are recalculated using the physical thickness of the film design and the value of the refractive index during film formation, and at least the design reflection amplitude, phase, and optical film used for control are calculated. At least one of the thicknesses is recalculated to correct the deposition stop time.

Preferably, the substrate is provided in the film formation chamber, holds a plurality of film formation target substrates so that the film formation surfaces thereof face the film formation material supply unit, and rotates around the center of the holder as the center of rotation. a substrate holder; the light projecting unit that projects monitor light so as to trace a plurality of film formation target substrates circularly held on the outer periphery of the rotated substrate holder; and the film formation target substrates. the light-receiving unit for receiving the monitor light transmitted through the substrate, detecting the monitor light at multiple wavelengths, and outputting a light-receiving signal reflecting the light transmittance at the multiple wavelengths of each film-forming target substrate; a trigger signal output unit that outputs a trigger signal for identifying the position of the substrate holder that rotates in synchronization with the rotation of the holder; and the control unit that acquires the light transmittance of each film formation target substrate by using the above method, and controls the thin film formation of each film formation target substrate in association with the acquired light transmittance information, wherein the control unit By specifying the position of the rotating substrate holder from the trigger signal synchronized with the rotation of the substrate holder, it is possible to determine which portion of the received light signal intermittently reflects the light transmittance of each film formation target substrate. is the light transmittance for each film formation target substrate, and which part of the received light signal is the light transmittance for which film formation target substrate is specified.

In the optical film thickness control method according to the third aspect of the present invention, a film forming material supplied from a film forming material supply unit arranged in a film forming chamber is deposited to form a thin multi-layer film. A light projecting step of projecting monitor light onto a target substrate, a light receiving step of receiving the monitor light transmitted through the film formation target substrate to acquire a light reception signal, and a temperature measurement step of measuring a substrate temperature during film formation. and a control step of acquiring the light transmittance of the film formation target substrate according to the light reception signal, and controlling the film formation of the thin film in association with the acquired light transmittance information, wherein the control step comprises , with respect to the multilayer film to be formed, the equivalent film is defined by equating the already formed multilayer film and the substrate with one film, and the square root of the reflectance between the two substances is defined as the reflection amplitude. and the current layer, the current reflection amplitude r between the current layer and air, and the fitting function T associated with the phase δ, and the measured transmittance time variation during deposition is Fitting is performed in association with the fitting function to determine at least one physical parameter of the phase δ and the equivalent reflection amplitude r during film formation, and the current layer is adjusted so as to match the determined physical parameter with a preset theoretical value. A stop time is determined, film formation control is performed to stop film formation at the stop time, and the film formation control is corrected based on the substrate temperature measured in the temperature measurement step.

A thin film forming method according to a fourth aspect of the present invention is a method for forming a multi-layered thin film on a substrate to be film-formed by supplying a film-forming material from a film-forming material supply section arranged in a film-forming chamber. a light projecting step of projecting monitor light onto the film formation target substrate; a light receiving step of receiving the monitor light transmitted through the film formation target substrate and obtaining a received light signal; and a substrate temperature during film formation. and a control step of acquiring the light transmittance of the film formation target substrate according to the light reception signal and controlling the film formation of the thin film in association with the acquired light transmittance information. , In the control step, regarding the multilayer film to be formed, the multilayer film and the substrate that have already been formed are regarded as a single film, which is the equivalent film, and the square root of the reflectance between the two substances is the reflection amplitude. , and adopting the equivalent reflection amplitude r between the equivalent film and the current layer, the current reflection amplitude r between the current layer and air, and the fitting function T related to the phase δ, the transmittance time during deposition Fitting the measured value of the change in association with the fitting function, determining at least one physical parameter of the phase δ and the equivalent reflection amplitude r during film formation, and matching the determined physical parameter with a preset theoretical value The stop time of the current layer is determined so that the current layer is stopped, film formation is controlled to stop film formation at the stop time, and the film formation control is corrected based on the substrate temperature measured in the temperature measurement step.

According to the present invention, error factors in film thickness control can be removed, film thickness errors can be suppressed, film thickness errors occurring in layers during film formation can be corrected, and moreover, film thickness errors can be corrected during film formation. It is possible to achieve highly accurate optical film thickness control even with respect to temperature changes in the physical properties of the film-forming material, and furthermore, it is possible to improve the accuracy of optical control for arbitrary multilayer film formation.

FIG. 1 is a configuration diagram schematically showing an ion beam assisted vacuum deposition apparatus, which is a vacuum film forming apparatus employing an optical film thickness control apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram schematically showing a film formation target substrate and a multilayer film of thin films formed on the film formation target substrate according to the first embodiment. FIG. 3 is a diagram for explaining terms such as an equivalent film and reflection amplitude related to optical film thickness control according to the present embodiment, and parameters of a fitting function. FIG. 4 is a diagram showing an example of the relationship between the fitting curve obtained by the fitting function and the measured value data of the transmittance change according to the present embodiment. FIG. 5 is a diagram showing refractive index characteristics as temperature dependence of an a-si sample (specimen). FIG. 6 is a diagram showing absorption (extinction) coefficient characteristics as temperature dependence of an a-si sample (specimen). FIG. 7 is a diagram showing an example of the relationship between the fitting curve obtained by the fitting function according to the first embodiment, the measured value data of the transmittance change, and the predicted curve of the next layer. FIG. 8 is a flow chart for explaining the optical film thickness control operation of the controller in the vacuum deposition apparatus according to the first embodiment. FIG. 9 shows the relationship between the wavelength and the transmittance of a film formation example of a bandpass filter (BPF) having a predetermined center wavelength using three substances in total phase compensation control (TPC) and time control and design as a comparative example. It is a characteristic diagram showing . FIG. 10 is a flow chart for explaining the simulation operation of the correction process for the temperature change of the refractive index of the film forming material for optical film thickness control in the control unit of the vacuum deposition apparatus according to the first embodiment. FIG. 11 is a diagram showing simulation results of a QW design BPF with a center wavelength of 940 nm, depending on the presence or absence of temperature correction processing. FIG. 12 is a diagram showing results of reproducibility confirmation by the temperature correction processing function according to the first embodiment of the present invention. FIG. 13 is a diagram showing film formation results of a design by a non-QW design BPF with a center wavelength of 940 nm, a TPC without temperature correction processing, and a TPC with temperature correction processing. FIG. 14 is a configuration diagram schematically showing an ion beam assisted vacuum vapor deposition apparatus, which is a vacuum film forming apparatus employing the optical film thickness control apparatus according to the second embodiment of the present invention. FIG. 15 shows how monitor light L is projected so as to trace onto a plurality of film-forming target substrates circularly held on the outer periphery of a substrate holder that rotates in the vacuum deposition apparatus of FIG. 14 is a diagram schematically showing an arrangement example of a plurality of film-forming target substrates circularly held on the outer peripheral portion of a rotated substrate holder of the vacuum deposition apparatus No. 14. FIG. FIG. 16 is a diagram for explaining signal processing for specifying the light transmittance for which film formation target substrate in the vacuum vapor deposition apparatus according to the second embodiment. FIG. 17 is a flow chart for explaining the optical film thickness control operation of the controller in the vacuum vapor deposition apparatus according to the second embodiment. FIG. 18 is a flow chart for explaining the simulation operation of the correction process for the temperature change of the refractive index of the film forming material for optical film thickness control in the control unit of the vacuum deposition apparatus according to the second embodiment. FIG. 19 is a diagram showing an example of the relationship between a fitting curve obtained by a fitting function according to the third embodiment, measured value data of transmittance change, and a prediction curve for the next layer. FIG. 20 is a flow chart for explaining the optical film thickness control operation of the controller in the vacuum deposition apparatus according to the third embodiment.

Embodiments of a vacuum film forming apparatus as a thin film forming apparatus employing the optical film thickness control apparatus of the present invention and a vacuum film forming method as a thin film forming method using the vacuum film forming apparatus will be described below with reference to the drawings.

(First embodiment)
[Configuration of Vacuum Film Forming Apparatus]
FIG. 1 is a configuration diagram schematically showing an ion beam assisted vacuum deposition apparatus, which is a vacuum film forming apparatus employing an optical film thickness control apparatus according to a first embodiment of the present invention.

In the vacuum deposition apparatus 1 of the first embodiment, for example, an exhaust pipe and a vacuum pump (not shown) are connected to a vacuum chamber 10, which is a film forming chamber, so that the inside can be reduced to a predetermined pressure. there is The back pressure in the vacuum chamber 10 during film formation by vacuum deposition is, for example, about 10 ^-2 to 10 ^-5 Pa.

A first vacuum evaporation source 21 and a second vacuum evaporation source 22 are arranged as a film-forming material supply unit 20 in the lower part of the vacuum chamber 10 . A first vapor deposition material 211 is accommodated inside the first vacuum evaporation source 21 , and a second vapor deposition material 221 is accommodated inside the second vacuum evaporation source 22 .
The first vapor deposition material 21 is eg SiO ₂ and the second vapor deposition material 23 is eg TiO ₂ or Ta ₂ O ₅ .
Each of the vacuum evaporation sources 21 and 22 is provided with heating means such as resistance heating, electron beam heating, laser beam heating, and electron gun (not shown). Vapor of material shoots out.

For example, in the vacuum chamber 10, a film formation target substrate 30, which is an optical substrate such as quartz glass, is placed in a direction in which the vapor of the vapor deposition materials of the first vacuum evaporation source 21 and the second vacuum evaporation source 22 is ejected. A substrate holder 31 is provided so as to face the film forming material supply unit 20 side.
For example, the substrate holder 31 is supported by a holder support 32 from above the vacuum chamber 10 .

Although FIG. 1 shows an example in which two vacuum deposition sources are provided to form a multilayer film of two types of thin films, a multilayer film of three types of thin films may be formed by providing three vacuum deposition sources. , various embodiments are possible.
When using three vacuum deposition sources, for example, the first deposition material is SiO ₂ , the second deposition material is Si ₃ N ₄ and the third deposition material is a-SiN:H.

FIGS. 2A and 2B are diagrams schematically showing a film formation target substrate 30 according to the first embodiment and a multi-layer film of thin films formed on the film formation target substrate.
FIG. 2A shows an example of using two vapor deposition materials, and FIG. 2B shows an example of using three vapor deposition materials.

When two substances are used as vapor deposition materials, as shown in FIG. 2A, when the vapor of the vapor deposition materials ejected from the two vacuum vapor deposition sources 21 and 22 reaches the surface of the film formation target substrate 30 and solidifies. , a multilayer film 310 of thin films 311 and 312 of vapor deposition materials is formed on the surface of the substrate 30 to be film-formed.
For example, the NBP filter is produced by alternately laminating 66 layers of SiO ₂ /TiO ₂ on the film formation target substrate 30 formed of an optical glass substrate. For example, the transmission band has a center wavelength of 827 nm and a bandwidth of 12 nm or less.

When three substances are used as vapor deposition materials, as shown in FIG. 2B, when the vapor of the vapor deposition materials jetted from each of the three vacuum vapor deposition sources reaches the surface of the film formation target substrate 30 and solidifies, the film is formed. A multilayer film 320 of thin films 321 , 322 , 323 of vapor deposition materials is formed on the surface of the target substrate 30 .
For example, a BP filter is produced by alternately laminating 66 layers of SiO ₂ /Si ₃ N ₄ /a-SiN:H on a film-forming target substrate 30 formed of an optical glass substrate. For example, the center wavelength of the transmission band is 940 nm.

Further, for example, an ion source 23 for irradiating a film-forming target substrate with ions such as oxygen ions is provided in the vacuum chamber 10, and ion beam assisted vacuum deposition can be performed.
By irradiating the film formation surface of the film formation target substrate 30 with ions from the ion source 23, a film is formed by the vapor deposition material supplied from the film formation material supply unit 20 and the film thickness is increased. A part of the film near the surface is sputtered by ions irradiated from the ion source 23 to thin the film, and the film can be formed while proceeding simultaneously.
At this time, if a film thickness difference occurs depending on the density distribution of the film-forming material supplied from the film-forming material supply unit 20 in the film-forming target substrate 30, conditions are set to cancel the film thickness difference. By performing sputtering with ions irradiated from the ion source 23, a multilayer film having a uniform in-plane film thickness distribution can be obtained.

In the first embodiment, a light projecting unit 40 for projecting monitor light L onto the film formation target substrate 30 held by the substrate holder 31 is provided.
The light projecting unit 40 is installed outside the vacuum chamber 10 and includes a light source 41 as a light projecting head that projects the monitor light L onto the film formation target substrate 30 . A halogen lamp, for example, can be used as the light source 40 .

A light-receiving unit 50 is provided for receiving the monitor light L transmitted through the film-forming target substrate 30 and the thin film and multilayer film being formed and outputting a light-receiving signal _SR .
The light-receiving unit 50 is provided, for example, in the vacuum chamber 10, and includes a light-receiving lens 51 as a light-receiving head of the light-receiving unit that receives the monitor light L transmitted through the film-forming target substrate, the thin film being formed, and the multilayer film, and a light-receiving lens. A spectrophotometer 52 configured to disperse the monitor light received by 51 , a photodetector 53 detecting the light split by the spectrophotometer 52 , and a monitor light L received by the light receiving lens 51 to the spectrophotometer 52 . It is composed of a light receiving optical system 54 such as an optical fiber that transmits the light to the light source.

For example, the photodetector 53 has a configuration in which light-receiving pixels that convert received light into optical signals are arranged in a matrix, and a CCD sensor or the like can be used as the photodetector 53 .
The monitor light L transmitted through the film formation target substrate 30 is received by the light receiving lens 51 , transmitted to the spectroscopic unit 52 by the light receiving optical system 54 , and spectroscopically separated.
The monitor light L transmitted through the film formation target substrate 30 is separated by the spectroscopic section 52, the separated light is detected by the photodetector section 53 in which light receiving pixels are arranged in a matrix, and the received light signal _SR is output. The photodetector 53 can acquire a continuous spectrum of the monitor light, that is, detect the monitor light at multiple wavelengths.

A light reception signal _SR detected by the light detection section 53 is supplied to a control section 60 constituted by a personal computer (PC) or the like.
The control unit 60 processes the received light signal _SR to obtain the light transmittance of the film formation target substrate 30 . Further, by obtaining the continuous spectrum of the monitor light as described above, the light transmission spectrum of the film-forming target substrate 30 is obtained.
The control unit 60 can feed back during film formation so as to change the film formation conditions so as to obtain desired optical characteristics from the obtained light transmittance or light transmission spectrum.

As described above, the control unit 60 according to the first embodiment acquires the light transmittance of the film-forming target substrate 30 according to the received light signal _SR , and performs thin film deposition in association with the acquired light transmittance information. More specifically, film formation control is performed to control the film thickness of the currently formed thin film (current layer).

In the vacuum deposition apparatus 1 of the first embodiment, in addition to the above configuration, a radiation thermometer 70 as a temperature measurement unit for measuring the substrate temperature during film formation is provided, for example, in the holder support portion 32 of the substrate holder 31. provided inside (on the upper side of the substrate holder 31).

In this embodiment, the substrate temperature includes not only the temperature of the substrate itself but also the temperature around the substrate which is expected to be kept at the same temperature as the substrate.

In the first embodiment, the control unit 60 is configured to be able to correct the film formation control based on the substrate temperature measured by the radiation thermometer 70 as the temperature measurement unit.

The optical film thickness control in the controller 60 according to the first embodiment will be described in detail below.
FIG. 3 is a diagram for explaining terms such as an equivalent film and reflection amplitude related to optical film thickness control according to the present embodiment, and parameters of a fitting function.

With respect to the multilayer film to be formed, the control unit 60 uses the equivalent film 330, which equates the already formed multilayer film and the substrate with one film, and the reflectance between the two substances, as shown in the following equation. Define the square root (r=√R) as the reflection amplitude, the (equivalent) reflection amplitude r between the equivalent film 330 and the current layer 340, the (current) reflection amplitude r between the current layer and air (vacuum), and A fitting function T(t) associated with the phase δ is employed.

The physical parameters of this fitting function T(t) are as follows.
The parameter r indicates the (equivalent) reflection amplitude between equivalent film 330 and current layer 340 .
The parameter r0 indicates the (current) reflection amplitude between the current layer 340 and air (vacuum).

The parameter ω indicates the angular velocity forming the phase information.
Here, there is a relationship of ωt=4πnd/λ. n represents the refractive index, d the physical thickness, and λ the monitoring wavelength.

The parameter φ0 indicates the initial phase, that is, the phase of a certain layer at the start of film formation.
The parameter Ψ indicates the constant of proportionality and expresses the systematic error of membrane absorption and transmittance measurements (the value would be 1 without them).

Among the above physical parameters r, r0, ω, ψ, φ0, the current reflection amplitude r0 is a fixed value, and the remaining physical parameters r, ω, ψ, φ0 are determined by fitting using fitting functions.

FIG. 4 is a diagram showing an example of the relationship between the fitting curve obtained by the fitting function and the measured value data of the transmittance change according to the present embodiment.
In FIG. 4, the vertical axis represents transmittance and the horizontal axis represents time.
In FIG. 4, FC indicates a fitting curve by the fitting function of the current layer, and MF indicates measured value data of transmittance change.

In the first embodiment, the control unit 60 performs fitting by associating the measured value (data) of the change in transmittance with time during film formation with the fitting function T(t), and the thickness of the layer in the middle of the film formation. When an error occurs, it is controlled so as to apply feedback to the film thicknesses of the next and higher layers so as to correct the error.

In the first embodiment, the control unit 60 performs fitting by associating the measured value (data) of the transmittance time change during film formation with the fitting function T(t), and determines the phase and equivalent reflection amplitude during film formation. The physical parameters r, ω, Ψ, and φ0 are determined, and the determined physical parameters r, ω, Ψ, and φ0 are used for the next control.
That is, the control unit 60 determines the stop time of the current layer so that the determined physical parameters r, ω, Ψ, φ0 match the preset theoretical values (target values, design values), and reaches the stop time. Stop the membrane.

Based on the film design of the multilayer film, the control unit 60 is given in advance the theoretical phase δ_design at the time point when each layer stops, and performs fitting in association with the time change of the transmittance according to the light receiving signal _SR during film formation with a fitting function. Then, the angular velocity ω of the phase δ and the initial phase φ0 are determined, and the film formation is stopped at the time t_stop at which the determined phase δ=ωt+φ0 during film formation coincides with the theoretical phase δ_design given in advance.

The control unit 60 directly uses the phase δ=ωt+φ0 of the phase information term of the fitting function T(t) to determine the deposition stop time t_stop of the layer being deposited.

The film formation stop time t_stop is given by the following equation.

Here, φ ₀ ^fit indicates the initial phase determined by fitting using the fitting function, and ω ^fit indicates the angular velocity determined by fitting using the fitting function.

Furthermore, in the first embodiment, the control unit 60 corrects temperature changes in the physical properties of the film formation material during film formation based on the substrate temperature measured by the radiation thermometer 70 as the temperature measurement unit. Then, the physical parameters are recalculated in association with the corrected physical properties of the film-forming substance, and the film-forming stop time t_stop is corrected.
In addition, in this embodiment, the physical properties of the film-forming substance include the refractive index n (or N).

Based on the temperature coefficient set for each film forming substance, the control unit 60 obtains the refractive index during film formation, and uses the physical film thickness in film design and the calculated refractive index value during film formation to form a multi-layer film. Recalculate the optical properties of the film.
Specifically, the characteristic matrix is recalculated up to the layers that have already been deposited.
Then, the control unit 60 recalculates at least one of the design reflection amplitudes r and r0, the phase δ, and the optical film thickness nd used for control from the above, and corrects the film formation stop time t_stop.

Here, in the optical film thickness control of the first embodiment, TPC described in the first embodiment or CRO described in the third embodiment described later is used to perform optical control for an arbitrary multilayer film design. The reason for not only improving the accuracy but also measuring the substrate temperature during film formation and using the result to correct the optical control will be explained.

FIG. 5 is a diagram showing refractive index characteristics as temperature dependence of an a-si sample (specimen).
In FIG. 5, the vertical axis represents refractive index, and the horizontal axis represents temperature. In FIG. 5, the curve A indicates the refractive index characteristics when the wavelength λ is 632.8 nm, and the curve B indicates the refractive index characteristics when the wavelength λ is 752.0 nm.
FIG. 6 is a diagram showing absorption (extinction) coefficient characteristics as temperature dependence of an a-si sample. In FIG. 6, the vertical axis represents the absorption (extinction) coefficient, and the horizontal axis represents the temperature. In FIG. 6, the curve C indicates the absorption (extinction) characteristics when the wavelength λ is 632.8 nm, and the curve D indicates the absorption (extinction) characteristics when the wavelength λ is 752.0 nm.

References: Oguz Yavas, Nhan Do, Andrew C. Tam, PT Leung, Wing P. Leung, Hee K. Park, Costas P. Grigoropoulos, Johannes Boneberg, and Paul Leiderer,
"Temperature dependence of optical properties for amorphous silicon at wavelengths of 632.8 and 752 nm," Opt. Lett. 18, 540-542 (1993)

Using the temperature coefficient T, the refractive index coefficient n(T) at a wavelength λ of 632.8 nm is
n(T)=4.19−1.43×10 ⁻⁴ T
can be expressed as
The absorption coefficient k(T) when the wavelength λ is 632.8 nm, using the temperature coefficient T, is
k(T)=0.24+4.85×10 ⁻⁴ T
can be expressed as

Using the temperature coefficient T, the refractive index coefficient n(T) at a wavelength λ of 752.0 nm is
n(T)=3.92+2.71×10 ⁻⁴ T
can be expressed as
The absorption coefficient k(T) when the wavelength λ is 632.8 nm, using the temperature coefficient T, is
k(T)=2.59×10 ⁻² +2.25×10 ⁻⁴ T
can be expressed as

The temperature change of the refractive index of semiconductor materials such as a-Si and a-Si:H is typically about 10 ⁻⁴ [1/K].
On the other hand, the temperature during film formation in the vacuum deposition apparatus 1 of the present embodiment and its variation are typically several tens of degrees Celsius to several hundreds of degrees Celsius.
In other words, the temperature change of the refractive index during film formation is about 10 ⁻² , which cannot be ignored in terms of optical control and product reproducibility.
Therefore, in the first embodiment, the substrate temperature during film formation is measured by the radiation thermometer 70, and the controller 60 uses the result to correct the optical control of the film formation control.

Next, the optical film thickness control operation of the controller 60 in the vacuum deposition apparatus 1 according to the first embodiment will be described with reference to FIGS. 7 and 8. FIG.
FIG. 7 is a diagram showing an example of the relationship between the fitting curve obtained by the fitting function according to the first embodiment, the measured value data of the transmittance change, and the predicted curve of the next layer.
In FIG. 7, the vertical axis represents transmittance and the horizontal axis represents time.
In FIG. 7, FC indicates a fitting curve by the fitting function of the current layer, MF indicates measured value data of transmittance change, and NP indicates a prediction curve of the next layer.
FIG. 8 is a flow chart for explaining the optical film thickness control operation of the controller 60 in the vacuum deposition apparatus 1 according to the first embodiment.

To explain the parameters employed in FIG. 8, i indicates the number of the currently applied (coated) layer, t_current indicates the time from the start of the i-th coating (coating) to the present, and t_stop indicates the i layer. Calculations of the optimal stop time for eye coating are shown.
ut indicates a unit time for giving a certain amount of allowable time to the time t_current from the start of coating of the i-th layer to the present. For example, one light projection time (or measurement time) is adopted as the unit time ut.
δ_design indicates the optimum stopping phase, which is calculated from the film design by optical theory.

First, in forming a multilayer film of a thin film of a desired film-forming material on a predetermined film-forming target substrate 30 using the vacuum film-forming apparatus 1 according to the first embodiment, each layer is first based on the film design of the multilayer film. is theoretically calculated in advance for the phase δ_design at the time of stopping (step ST1).

Then, for example, the film-forming target substrate 30 is held by the film-forming material supply unit 20 inside and the substrate holder 31 of the vacuum chamber 10 . Here, the film formation surface of the film formation target substrate 30 is held so as to face the film formation material supply unit 20 side.

Next, for example, a film-forming material is supplied from the film-forming material supply unit 20 to form a thin film of the film-forming material on the film-forming target substrate 30 . That is, the thin film formation of the i-layer (layer coating) is started (step ST2).

Next, monitor light L is projected onto the film formation target substrate 30 held by the substrate holder 31 .
Next, for example, the monitor light L transmitted through the film-forming target substrate 30 is received, and the received light signal S_R.to get
The control unit 60 controls the received light signal S_R.is signal-processed to acquire the light transmittance of the film-forming target substrate 30 during film-forming.
The control unit 60 controls the time t from the start of film formation of the i-layer. When current passes (step ST3), a new data point of the transmittance measured by the spectroscope 52 is added (step ST4).

In the optical film thickness control according to the first embodiment, in step ST3, the time obtained by adding the unit time ut of the allowable time to the time t_current from the start of coating of the i-th layer to the present is After the elapse of this time, the process of adding a new data point of the transmittance measured by the spectroscope 52 in step ST4 is performed.

Then, the control unit 60 performs fitting to apply all transmittance data (step ST5).
Specifically, as shown in FIG. 7, the control unit 60 successively fits the change in transmittance with time during actual film formation to determine the angular velocity ω and the initial phase φ0. Actually, the physical parameters r, ω, ψ, φ0 are determined and updated (step ST5).

The control unit 60 adjusts the stop time t of the current layer so that the determined physical parameters r, ω, ψ, φ0 and the preset theoretical values (target values, design values) match. Calculate (determine) stop and stop time t Film formation is stopped at stop (steps ST6 and ST7).
Specifically, based on the film design of the multilayer film, the control unit 60 is given in advance the theoretical phase δ_design at the time point when each layer is stopped, and the received light signal S_R.The change in transmittance over time is fitted in association with the fitting function, the angular velocity ω of the phase δ and the initial phase φ0 are determined, and the determined phase δ=ωt+φ0 during film formation is the theoretical phase δ_design given in advance. matching time t The film formation is stopped with stop.

In the optical film thickness control according to the first embodiment, the time obtained by subtracting the time t_current from the optimum stop time t_stop for the i-th layer coating in step ST7 is half the unit time ut of the allowable time (0.5). If it becomes shorter, the film formation of the i-layer is completed (step ST8).

When the film formation of the i layers is completed in this manner (step ST8), the controller 60 determines whether or not i is the total number of layers to be formed (step ST9).
If it is determined in step ST9 that i is the total number of layers to be deposited, the deposition process is terminated.
If it is determined in step ST9 that i is not the total number of layers to be formed, i is incremented by 1 and the processing is repeated from step ST1.

The above optical film thickness control method can also be called total phase compensation control (Total Phase Compensation: TPC).

Here, the effect of the actual measurement comparing the TPC control and the conventional time control will be described.
FIG. 9 shows the relationship between the wavelength and the transmittance of a film formation example of a bandpass filter (BPF) having a predetermined center wavelength using three substances in total phase compensation control (TPC) and time control and design as a comparative example. It is a characteristic diagram showing .
FIG. 9 shows a characteristic diagram of an example of deposition _of a 940 nm non-QW design band pass filter using three substances of a-Si:H/ _Si3N4 / _SiO2 .
In FIG. 9, the vertical axis represents transmittance and the horizontal axis represents wavelength.
In FIG. 9, A indicates a characteristic curve by TPC control, B indicates a characteristic curve by time control, and C indicates a characteristic curve by design.

As a result of comparing TPC and time control with reference to FIG. 9, it was found that TPC has the following advantages.
As a result of TPC control without adjusting the refractive index or the like, the ^1st batch already has a distribution and center wavelength close to the design.
The remaining central wavelength shift is due to the refractive index temperature change of a-Si:H, which is one of the vapor deposition materials, and the shift width of the central wavelength substantially agrees with the theoretical prediction.
Using a temperature correction function, which will be described later, further improves the agreement of the center wavelength with the design value.
As described above, it was verified that the application of TPC can obtain film deposition results with a spectrum close to the design without the need for fine adjustment.

Here, the physical properties of the film forming material for controlling the optical film thickness according to the first embodiment, and in the present embodiment, correction processing for the temperature change of the refractive index will be described with reference to FIG. 10 .
FIG. 10 is a flow chart for explaining the simulation operation of the correction process for the temperature change of the refractive index of the film forming material for optical film thickness control in the control unit of the vacuum deposition apparatus according to the first embodiment.

First, the monitor light L is not projected onto the film formation target substrate 30 of the substrate holder 31 (ut→0), and the layer number is set to 1 (step ST21).
If the layer number is not that of the last layer (step ST22), the projection time of the monitor light is lengthened (step ST23), and the substrate temperature is obtained (step ST24). In step ST24, a dummy current temperature is calculated for each film formation.
Next, the refractive index N is set according to the temperature (step ST25).
Next, the final thickness is added by deposition (step ST26).
Then, the transmittance is calculated by recalculating the characteristic matrix (step ST27).
Next, an SWM control process for input transmittance is performed (step ST28).
In steps ST27 and ST28, the control unit 60 obtains the refractive index during film formation based on the temperature coefficient set for each film forming material, and determines the physical film thickness in film design and the obtained refractive index during film formation. is used to recalculate the optical properties of the multilayer film.
Then, the control unit 60 recalculates at least one of the design reflection amplitudes r and r0, the phase δ, and the optical film thickness nd used for control from the above, and corrects the film formation stop time t_stop.

Next, the SWM changes the layer flag (step ST29).
The layer number is increased (step ST30), and Temp (temperature) is set to Temp_in_SWM (step ST31). For actual coatings, "Temp_in_SWM" is replaced with the value from the radiation thermometer.
Then, using Temp_in_SWM, the design is changed by SWM (step ST32), and the process proceeds to step ST22.

Even if the flag is not changed in step ST29, the process proceeds to step ST22 without proceeding to the process of step ST30.
Then, in step ST22, when it is determined that the layer is the last layer, the simulation ends.

FIGS. 11A and 11B show QW design with a center wavelength of 940 nm depending on the presence or absence of temperature correction processing ("TC", which is an abbreviation for Temperature Correction, is used in FIGS. 12 and 13 described later). It is a figure which shows the simulation result of BPF.
In FIG. 11, the vertical axis represents transmittance and the horizontal axis represents wavelength.
FIG. 11A shows the simulation results without the temperature correction process, and FIG. 11B shows the simulation results with the temperature correction process.
In the figure, the curve indicated by A is the characteristic curve by design, and the curve indicated by B is the characteristic curve of the simulation results.

In this way, according to the deposition control simulation, if the control is performed without considering the refractive index temperature change, the spectrum of the deposition results shifts to the shorter wavelength side than the target spectrum, and the design characteristic curve deviate from A.
On the other hand, when controlled in consideration of the refractive index temperature change, the spectrum of the film formation result matches the design characteristic curve A without shifting to the shorter wavelength side than the target spectrum. It can be seen that the correction is correct.

FIG. 12 is a diagram showing results of reproducibility confirmation by the temperature correction processing function according to the first embodiment of the present invention.
FIG. 12 shows simulation results of TPC reproducibility with non-QW designed BPFs with a central wavelength of 940 nm for three samples.
In FIG. 12, the vertical axis represents transmittance and the horizontal axis represents wavelength.
The first sample has a central wavelength of 940.11 nm and a film forming temperature of 55 to 65° C. The second sample has a central wavelength of 940.64 nm and a film forming temperature of about 80° C. The third sample has a central wavelength of 940.0° C. At 67 nm, the film formation temperature is 55 to 65°C.
In FIG. 12, the curve indicated by A is the characteristic curve of the first sample, the curve indicated by B is the characteristic curve of the second sample, and the curve indicated by C is the characteristic curve of the third sample.

As shown in FIG. 12, as a result of confirming the reproducibility by the temperature correction processing function, good reproducibility can be confirmed even if the film formation temperature is different.

FIG. 13 is a diagram showing film formation results of a design by a non-QW design BPF with a center wavelength of 940 nm, a TPC without temperature correction processing, and a TPC with temperature correction processing.
In FIG. 13, the vertical axis represents transmittance and the horizontal axis represents wavelength.
In FIG. 13, the curve indicated by A is the characteristic curve by design, the curve indicated by B is the characteristic curve by TPC without temperature correction processing, and the curve indicated by C is the characteristic curve by TPC with temperature correction processing. .

As can be seen from FIG. 13, due to the effect of temperature correction, the center wavelength approaches the design.
Further, by performing optical film thickness control by TPC accompanied by temperature correction processing, it is possible to perform self-correction for thickness errors without the need to finely adjust the input refractive index value.
Robust against systematic errors in measured transmittance.
Further, the thermo-optical dependence of the refractive index of SiH(TC) is corrected as follows.
SiH: dn/dT = ~3 x ^10-4 [1/K]

As described above, according to the first embodiment, the controller 60 combines the multilayer film and the substrate that have already been formed into a certain film and The equated object is defined as the equivalent film 330, the square root of the reflectance between the two substances (r=√R) is defined as the reflection amplitude, and the (equivalent) reflection amplitude r between the equivalent film 330 and the current layer 340 is defined as the current layer and air (vacuum), and a fitting function T(t) that relates the amplitude r0 and the phase δ.
In the first embodiment, the control unit 60 performs fitting by associating the measured value (data) of the transmittance time change during film formation with the fitting function T, and a film thickness error occurs in the layer during film formation. When the error is corrected, control is performed so as to apply feedback to the film thicknesses of the next and higher layers.
In the first embodiment, the control unit 60 performs fitting by associating the measured value (data) of the transmittance time change during film formation with the fitting function T(t), and determines the phase and equivalent reflection amplitude during film formation. The physical parameters r, ω, Ψ, and φ0 are determined, and the determined physical parameters r, ω, Ψ, and φ0 are used for the next control.
That is, the control unit 60 determines the stopping time of the current layer so that the determined physical parameters r, ω, Ψ, φ0 match the preset target values (design values), and stops the film formation at the stopping time. do.
That is, based on the film design of the multilayer film, the control unit 60 is given in advance the theoretical phase δ_design at the time point when each layer is stopped, and the received light signal S_R.The change in transmittance over time is associated with the fitting function T(t) according to the , and the angular velocity ω of the phase δ and the initial phase φ0 are determined. Time t matching the theoretical phase δ_design The film formation is stopped with stop.

Therefore, according to the first embodiment, the following effects can be obtained.
Since only phase information is used and amplitude information is not used, adverse effects such as systematic errors in transmittance measurement, film absorption, and substrate warping can be suppressed.
Even if there is a film thickness error in the previous layer, the current film thickness is automatically corrected in the direction of canceling out the adverse effect.
Even if there is an error in the design refractive index, the optical film thickness nd is automatically corrected in the direction matching the design (from the relationship ωt=4πnd/λ).
Unlike conventional proportional control, control is possible at any stop position and monitoring wavelength. In other words, it is not subject to restrictions such as Final Swing.
Even if there is rate fluctuation, it is possible to maintain the determination accuracy of the current phase by automatically correcting the fitting range, and it is possible to maintain high resistance to rate fluctuation.

In other words, according to the first embodiment, error factors in film thickness control can be removed, film thickness errors can be suppressed, and film thickness errors occurring in layers during film formation can be corrected. In addition, it is possible to realize highly accurate optical film thickness control against temperature changes in the physical properties of the film deposition material during film formation, and by extension, improve the accuracy of optical control for arbitrary multilayer film formation. becomes possible.

According to the first embodiment, the substrate temperature during film formation is measured by the radiation thermometer 70, and the control unit 60 uses the result to correct the optical control. However, good reproducibility can be confirmed.
More specifically, it is possible to achieve highly accurate optical film thickness control even with respect to temperature changes in the physical properties (for example, refractive index) of the film-forming material during film formation.

(Second embodiment)
FIG. 14 is a configuration diagram schematically showing an ion beam assisted vacuum vapor deposition apparatus, which is a vacuum film forming apparatus employing the optical film thickness control apparatus according to the second embodiment of the present invention.

The difference of the vacuum deposition apparatus 1A according to the second embodiment from the vacuum deposition apparatus 1 according to the first embodiment is as follows.
In the vacuum deposition apparatus 1A according to the second embodiment, in the vacuum chamber 10A, a plurality of vapor deposition materials of the vacuum evaporation sources 21A including the plurality of deposition sources of the film-forming material supply section 20A are ejected in a direction in which the vapor of the deposition material is ejected. A sheet of film-forming target substrate 30 is held so that the film-forming surface faces the film-forming material supply unit side, and has a flat disk shape or a dome shape, and the center of the flat disk or the top of the dome is the center of rotation. A substrate holder 31A that rotates as a
For example, the substrate holder 31A is rotatably supported by the holder supporting portion 32A, and is rotationally driven by driving a motor 33 having an encoder 331 that constitutes a rotating mechanism.

In the vacuum vapor deposition apparatus 1A according to the second embodiment, the light projecting part 40A traces the monitor light L to the plurality of film formation target substrates 30 circularly held on the outer periphery of the rotated substrate holder 31A. illuminate as if
The light-receiving lens 51 of the light-receiving unit 50 receives the monitor light L transmitted through the film-forming target substrate 30 , the monitor light L is detected at multiple wavelengths by the spectroscope 52 , and the light-detecting unit 44 detects multiple wavelengths of each film-forming target substrate. A received light signal _SR reflecting the light transmittance at the wavelength is output to the data processor 61 .

Note that the light receiving lens 51 is supported by a light receiving lens supporting portion 55 .
For example, the light-receiving lens supporting portion 55 that supports the light-receiving lens 51 is provided so as not to hinder the rotational driving of the substrate holder 31A and the holder supporting portion 32A.

Further, the encoder 331 as a trigger signal output unit outputs to the data processor 61 a trigger signal _ST as a synchronizing signal for specifying the position of the rotating substrate holder synchronized with the rotation of the substrate holder 31A.

The data processor 61 supplies the received light signal _SR and the trigger signal _ST to the controller 60A, and the controller 60A performs signal processing on the received light signal _SR and the trigger signal _ST to determine the light transmittance of each film-forming target substrate. to get Further, by obtaining the continuous spectrum of the monitor light, the light transmission spectrum for each film formation target substrate is obtained.
From the obtained light transmittance or light transmission spectrum, it is possible to feed back during the film formation so as to change the film formation conditions so as to obtain the desired optical characteristics.

That is, the control unit 60A receives the received light signal _SR and the trigger signal _ST , processes the received light signal _SR and the trigger signal _ST , obtains the light transmittance of each film formation target substrate, and obtains the obtained light transmittance. The thin film formation is controlled for each film formation target substrate in association with the rate information.
More specifically, the control unit 60A specifies the position of the rotating substrate holder 31A from the trigger signal _ST synchronized with the rotation of the substrate holder 31A, thereby intermittently changing the light transmittance of each film-forming target substrate. It is specified which part of the light reception signal _SR reflected in SR is the light transmittance for which film formation target substrate, and which part of the light reception signal _SR is the light transmittance for which film formation target substrate. do.

Here, by specifying the position of the rotating substrate holder 31A, which part of the received light signal _SR intermittently reflecting the light transmittance of each film formation target substrate corresponds to the light transmittance of which film formation target substrate. An example of processing for identifying which part of the received light signal _SR is the light transmittance for which film formation target substrate will be described.

In FIG. 15A, monitor light L is projected so as to trace a plurality of film formation target substrates 30 circularly held on the outer periphery of a rotated substrate holder 31A of the vacuum deposition apparatus of FIG. It is a figure which shows a state typically.
FIG. 15B is a diagram schematically showing an arrangement example of a plurality of film formation target substrates 30 circularly held on the outer periphery of a rotated substrate holder 31A of the vacuum deposition apparatus of FIG. be.

In the example of FIG. 15, a substrate holder 31A having a dome shape and rotated around the top of the dome is provided with a plurality of film-forming target substrates so that the film-forming surface faces the film-forming material supply unit side. 30 is held,
Monitor light L is projected onto the film formation target substrate 30 from a light projection unit (not shown), and the monitor light L that has passed through the film formation target substrate 30 is received by the light receiving lens 51 .

In FIG. 15B, the projection spot _SPL of the monitor light L is arranged so as to pass over the film-forming target substrate 30 arranged in the outer peripheral portion of the substrate holder 31A. The vicinity of the area R traced by the projected light spot _SPL becomes the non-defective product distribution area.

FIG. 16 is a diagram for explaining signal processing for specifying the light transmittance for which film formation target substrate in the vacuum vapor deposition apparatus according to the second embodiment.

A plurality of _film -forming target substrates (30 ₁ , 30 ₂ , 30 ₃ . . . _n ) pass over.
By receiving the monitor light L transmitted through the moving film formation target substrates (30 ₁ , 30 ₂ , 30 ₃ . . . 30 _n ), each film formation target substrate (30 ₁ , 30 ₂ , 30 ₃ . 30 _n ) intermittently reflecting the light transmittance of the received light signal _SR .
Here, by specifying the position of the rotating substrate holder 31 from the trigger signal _ST synchronized with the rotation of the substrate holder 31A, the light-receiving signal _SR intermittently reflecting the light transmittance of each film-forming target substrate is obtained. It is possible to specify which part of the light transmittance is for which film formation target substrate. The trigger signal _ST is output once or many times in one rotation period of the substrate holder 31A.
By specifying which part of the light reception signal _SR is the light transmittance for which film formation target substrate, the light reception signal S ₁ for the film formation target substrate ₃₀₁ and the film formation target substrate are obtained from the light _reception signal SR. It is possible to obtain a light reception _{signal S2} for the film formation target _{substrate 302} , a light reception signal _S3 for the film formation target substrate ₃₀₃ , .

For example, when the starting radius of the center of the substrate to be film-formed located at the outer periphery of the substrate holder is 450 mm, the diameter of the substrate to be film-formed is 30 mm, and the rotation speed of the substrate holder is 30 rpm, the monitor light is treated as a point light source. , the monitor time per rotation of the substrate holder per film formation target substrate is 21 ms. Since the spot diameter of the monitor light has a certain size, the monitor time is further shortened. In order to ensure high film thickness controllability within this limited time, high photodetection sensitivity is required.

For example, by using a CCD sensor or the like as the light detection unit 53, it is possible to increase the amount of information obtained by obtaining information on the light transmittance at multiple wavelengths, improve the accuracy of the light transmittance, and improve the S/N ratio. ratio can be improved.

[Optical film thickness control of the second embodiment]
Here, the optical film thickness control operation of the controller 60A in the vacuum vapor deposition apparatus 1A according to the second embodiment will be described.

FIG. 17 is a flow chart for explaining the optical film thickness control operation of the controller 60A in the vacuum vapor deposition apparatus 1A according to the second embodiment.
The optical film thickness control according to the second embodiment is basically the same as the optical film thickness control according to the first embodiment shown in FIG. .

In FIG. 17, when explaining including the parameters common to FIG. 8, i indicates the layer number currently being applied (coated), t_current indicates the time from the start of the i-th coating (coating) to the present, t_stop indicates the calculated optimum stop time for the i-th coating.
dt indicates the unit time of dome rotation of the substrate holder 31A.
δ_design indicates the optimum stopping phase, which is calculated from the film design by optical theory.

In the optical film thickness control according to the second embodiment, in step ST3A in FIG. Assuming that the time from the start to the present is t_current, after this time elapses, a process of adding a new data point of the transmittance measured by the spectroscope 52 in step ST4 is performed.

Further, in the optical film thickness control according to the second embodiment, the time obtained by subtracting the time t_current from the optimum stop time t_stop of the i-th coating in step ST7A of FIG. 17 is half the unit time dt of the dome rotation. When it becomes shorter than (0.5), the film formation of the i-layer is finished (step ST8).

Next, the physical properties of the film forming material for controlling the optical film thickness according to the second embodiment, in this embodiment, correction processing for the temperature change of the refractive index will be described with reference to FIG. 18 .
FIG. 18 is a flow chart for explaining the simulation operation of the correction process for the temperature change of the refractive index of the film forming material for optical film thickness control in the control unit of the vacuum deposition apparatus according to the second embodiment.

The correction processing of the optical film thickness control according to the second embodiment is basically the same as the optical film thickness control according to the first embodiment shown in FIG. , the processing of step ST24A is slightly different.

In FIG. 18, dt indicates the unit time of dome rotation of the substrate holder 31A.

In the optical film thickness control according to the second embodiment, first, the dome of the substrate holder 31A is not rotated (rotation→0), and the layer number is set to 1 (step ST21A).
If the layer number is not the final layer (step ST22), the rotation speed of the dome is increased (step ST23A), and the substrate temperature is obtained (step ST24A). At step ST24, a dummy current temperature is calculated for each rotation.
Next, the refractive index N is set according to the temperature (step ST25).
Next, the final thickness is added by deposition (step ST26).
Then, the transmittance is calculated by recalculating the characteristic matrix (step ST27).
Next, an SWM control process for input transmittance is performed (step ST28).
In steps ST27 and ST28, the control unit 60C obtains the refractive index during film formation based on the temperature coefficient set for each film forming substance, and determines the physical film thickness in film design and the obtained refractive index during film formation. is used to recalculate the optical properties of the multilayer film.
Then, the control unit 60C recalculates at least one of the design reflection amplitudes r and r0, the phase δ, and the optical film thickness nd used for control from the above, and corrects the film formation stop time t_stop.

Next, the SWM changes the layer flag (step ST29).
The layer number is increased (step ST30), and Temp (temperature) is set to Temp_in_SWM (step ST31). For actual coatings, "Temp_in_SWM" is replaced with the value from the radiation thermometer.
Then, using Temp_in_SWM, the design is changed by SWM (step ST32), and the process proceeds to step ST22.

Even if the flag is not changed in step ST29, the process proceeds to step ST22 without proceeding to the process of step ST30.
Then, in step ST22, when it is determined that the layer is the last layer, the simulation ends.

According to the second embodiment, it is possible to obtain the same effects as those of the first embodiment described above.
According to the second embodiment, since only phase information is used and amplitude information is not used, adverse effects such as systematic errors in transmittance measurement, film absorption, and substrate warping can be suppressed.
Even if there is a film thickness error in the previous layer, the current film thickness is automatically corrected in the direction of canceling out the adverse effect.
Even if there is an error in the design refractive index, the optical film thickness nd is automatically corrected in the direction matching the design (from the relationship ωt=4πnd/λ).
Unlike conventional proportional control, control is possible at any stop position and monitoring wavelength. In other words, it is not subject to restrictions such as Final Swing.
Even if there is rate fluctuation, it is possible to maintain the determination accuracy of the current phase by automatically correcting the fitting range, and it is possible to maintain high resistance to rate fluctuation.

According to the second embodiment, the substrate temperature during film formation is measured by the radiation thermometer 70, and the control unit 60 uses the result to correct the optical control. However, good reproducibility can be confirmed.
More specifically, it is possible to achieve highly accurate optical film thickness control even with respect to temperature changes in the physical properties (for example, refractive index) of the film-forming material during film formation.

Furthermore, according to the second embodiment, the following effects can be obtained.
That is, according to the second embodiment, a plurality of film formation target substrates are held by the substrate holder, and the monitor light is projected onto the film formation target substrates held in the outer periphery of the substrate holder, and transmitted through the monitor light. The monitor light is received to obtain the light transmittance of each film-forming target substrate, and in the vacuum film-forming process for manufacturing the optical filter, the yield can be improved while coping with mass production.

(Third embodiment)
FIG. 19 is a diagram showing an example of the relationship between a fitting curve obtained by a fitting function according to the third embodiment, measured value data of transmittance change, and a prediction curve for the next layer.
In FIG. 19, the vertical axis represents transmittance and the horizontal axis represents time.
In FIG. 19, FC2 indicates a fitting curve by the fitting function of the current layer, MF2 indicates measured value data of transmittance change, and NP2 indicates a prediction curve of the next layer.
FIG. 20 is a flow chart for explaining the optical film thickness control operation of the controller in the vacuum deposition apparatus according to the third embodiment.

The optical film thickness control according to the third embodiment is basically the same as the optical film thickness control according to the first embodiment shown in FIG. 8 and the optical film thickness control according to the second embodiment shown in FIG. , the processing of step ST6B is different.

In the optical film thickness control of the first and second embodiments, the controller 60 controls the current layer so that the determined physical parameters r, ω, ψ, and φ0 match preset target values (design values). stop time t Calculate (determine) stop and stop time t Film formation is stopped at stop (steps ST6 and ST7).
Specifically, based on the film design of the multilayer film, the control unit 60 is given in advance the theoretical phase δ_design at the time point when each layer is stopped, and the received light signal S_R.The time change of the transmittance T is fitted in association with the fitting function, the angular velocity ω of the phase δ and the initial phase φ0 are determined, and the determined phase δ = ωt + φ0 during film formation is the theoretical phase δ_design given in advance time t coincides with The film formation is stopped with stop.

In contrast, in the optical film thickness control of the third embodiment, calculating t_stop as the expected reflection amplitude of the equivalent layer in the coating of the (i + 1)th layer is r_design(i + 1) is equal to (step ST6B).
In other words, the deposition stop time of the current layer is determined so that the peak expected value of the next layer matches the design.
Physically, this is equivalent to determining the stop time of the current layer so that the absolute value of the equivalent reflection amplitude of the current layer when forming the next layer matches the design value.

That is, in the optical film thickness control of the third embodiment, as shown in FIG. 19, the controller 60B is given in advance the theoretical equivalent reflection amplitude lr at the stop point of each layer based on the film design of the multilayer film. During film formation, the change in transmittance T with respect to time according to the light reception signal _SR is fitted to the fitting function to determine the equivalent reflection amplitude r of the current layer 340 during the film formation of the next layer.
Then, the control unit 60B determines the stop time of the current layer 340 so that the absolute value of the equivalent reflection amplitude r width of the current layer 340 at the time of film formation of the determined next layer coincides with the theoretical equivalent reflection amplitude lr. Film formation is stopped at the stop time.

According to the third embodiment, even if there is a film thickness error in the previous layer, the current film thickness is automatically corrected in such a way as to cancel out the adverse effect.
Even if there is an error in the design refractive index, the optical film thickness nd is automatically corrected in the direction matching the design (from the relationship ωt=4πnd/λ).
Unlike conventional proportional control, control is possible at any stop position and monitoring wavelength. In other words, it is not subject to restrictions such as Final Swing.
Even if there is rate fluctuation, it is possible to maintain the determination accuracy of the current phase by automatically correcting the fitting range, and it is possible to maintain high resistance to rate fluctuation.
Further, according to the second embodiment, in the vacuum film forming process for manufacturing the optical filter, it is possible to improve the yield while coping with mass production.

The invention is not limited to the above description.
For example, it is applicable not only to the ion beam assisted vacuum deposition apparatus and method, but also to other vacuum deposition apparatuses and methods. In addition to vacuum film formation, the present invention can also be applied to other thin film formation apparatuses and methods such as film formation by sputtering or film formation by CVD (chemical vapor deposition).
The trigger signal may be output once or many times in one cycle of rotation of the substrate holder.
Further, the control units such as the light emitting unit, the light receiving unit, the trigger signal output unit, and the signal processing unit in the above embodiments acquire the light transmittance of each film formation target substrate and are formed on the film formation target substrate. A device for monitoring the optical film thickness of the thin film is constructed. As an optical film thickness monitor device, the optical film thickness of a thin film formed on a substrate to be film-formed can be monitored by removing it from the vacuum film-forming device and attaching it to another thin film-forming device.
In addition, various modifications are possible without departing from the gist of the present invention.

10, 10A, 10B... vacuum chamber, 20, 20A... film forming material supply unit, 21, 21A... first vacuum deposition source, 211... first deposition material, 22... second Vacuum deposition source 221 Second deposition material 23 Ion source 30, 30 ₁ to 30 Film formation target substrate 31, 31A Substrate holder 32, 32A Holder support portion 33... Motor, 331... Encoder, 40... Light projecting unit, 41... Light source, 50... Light receiving unit, 51... Light receiving lens, 52... Spectroscopic unit, 53... Photodetector 54 Light-receiving optical system 55 Light-receiving head support 60, 60A, 60B Control unit 70 Radiation thermometer L Monitor light _S1 ˜S _{n .} . _. light receiving signal, _SR .

Claims (16)

a light projecting unit for projecting monitor light onto a film-forming target substrate on which a film-forming material supplied from a film-forming material supply unit arranged in the film-forming chamber is formed to form a thin multi-layer film;
a light receiving unit that receives the monitor light transmitted through the film formation target substrate and outputs a light reception signal;
a temperature measuring unit that measures the substrate temperature during film formation;
a control unit that acquires the light transmittance of the film formation target substrate according to the light reception signal, and controls thin film formation in association with the acquired light transmittance information;
The control unit
With respect to the multilayer film to be formed, the multilayer film and the substrate that have already been formed are defined as one film as an equivalent film, and the square root of the reflectance between the two substances is defined as the reflection amplitude. Employing a fitting function T related to the equivalent reflected amplitude r between the current layer, the current reflected amplitude r between the current layer and air, and the phase δ,
During film formation, the measured value of the transmittance time change is associated with the fitting function and fitted to determine a physical parameter of at least one of the phase δ and the equivalent reflection amplitude r during film formation, and the determined physical parameter and the preliminarily It is possible to determine the stop time of the current layer so that it matches the set theoretical value, and to perform film formation control to stop film formation at that stop time.
An optical film thickness control apparatus capable of correcting the film formation control based on the substrate temperature measured by the temperature measurement unit. The control unit
Based on the substrate temperature measured by the temperature measuring unit, the temperature change in the physical properties of the film forming material during film formation is corrected, and the physical parameters are recalculated in association with the corrected physical properties of the film forming material. 2. The optical film thickness control device according to claim 1, wherein the film formation stop time is corrected by 3. The optical film thickness control device according to claim 2, wherein the physical properties of the film-forming substance include a refractive index. The control unit
Based on the temperature coefficient set for each film-forming substance, the refractive index during film-forming is obtained,
Recalculate the optical properties of the multilayer film using the physical film thickness in the film design and the value of the refractive index obtained during film formation,
4. The optical film thickness control device according to claim 3, wherein at least one of the reflection amplitude, phase, and optical film thickness in design used for control is recalculated to correct the film formation stop time. The control unit
Based on the film design of the multilayer film, the theoretical phase δ_design at the stop point of each layer is given in advance,
Fitting the change in transmittance over time according to the light reception signal during film formation in association with the fitting function to determine the angular velocity ω of the phase δ and the initial phase φ0,
5. The optical film thickness control apparatus according to any one of claims 1 to 4, wherein the film formation is stopped at a time when the determined phase δ=ωt+φ0 during film formation coincides with the theoretical phase δ_design given in advance. The control unit
Based on the film design of the multilayer film, the theoretical equivalent reflection amplitude at the stop point of each layer is given in advance,
Fitting the change in transmittance over time according to the light reception signal during film formation in association with the fitting function to determine the equivalent reflection amplitude of the current layer during film formation of the next layer,
1. A stop time for the current layer is determined so that the absolute value of the equivalent reflection amplitude of the current layer at the time of film formation of the determined next layer coincides with the theoretical equivalent reflection amplitude, and the film formation is stopped at the stop time. 5. The optical film thickness control device according to any one of 4 to 4. a substrate holder that is provided in the film formation chamber, holds a plurality of film formation target substrates so that the film formation surfaces face the film formation material supply unit, and rotates around the center of the holder;
the light projecting unit that projects monitor light so as to trace the plurality of film formation target substrates circularly held on the outer periphery of the rotated substrate holder;
The light receiving for receiving the monitor light transmitted through the film formation target substrate, detecting the monitor light at multiple wavelengths, and outputting a light reception signal reflecting the light transmittance of each film formation target substrate at multiple wavelengths. Department and
a trigger signal output unit that outputs a trigger signal for identifying the position of the rotating substrate holder synchronized with the rotation of the substrate holder;
The light-receiving signal and the trigger signal are input, the light-receiving signal and the trigger signal are processed, the light transmittance of each film formation target substrate is obtained, and the obtained light transmittance information is associated with each film formation target substrate. and the control unit that controls the film formation of the thin film of
The control unit
By specifying the position of the rotating substrate holder from the trigger signal synchronized with the rotation of the substrate holder, which part of the light receiving signal intermittently reflecting the light transmittance of each film formation target substrate corresponds to which part. 7. The optical film according to any one of claims 1 to 6, wherein the light transmittance for each film formation target substrate is specified, and which part of the received light signal is the light transmittance for which film formation target substrate is specified. Thickness controller. a deposition chamber;
a film forming material supply unit arranged in the film forming chamber;
a film-forming target substrate on which a film-forming material supplied from the film-forming material supply unit is formed to form a thin multi-layer film;
a light projecting unit that projects monitor light onto the film formation target substrate;
a light receiving unit that receives the monitor light transmitted through the film formation target substrate and outputs a light reception signal;
a temperature measuring unit that measures the substrate temperature during film formation;
a control unit that acquires the light transmittance of the film formation target substrate according to the light reception signal, and controls thin film formation in association with the acquired light transmittance information;
The control unit
With respect to the multilayer film to be formed, the multilayer film and the substrate that have already been formed are defined as one film as an equivalent film, and the square root of the reflectance between the two substances is defined as the reflection amplitude. Employing a fitting function T related to the equivalent reflected amplitude r between the current layer, the current reflected amplitude r between the current layer and air, and the phase δ,
During film formation, the measured value of the transmittance time change is associated with the fitting function and fitted to determine a physical parameter of at least one of the phase δ and the equivalent reflection amplitude r during film formation, and the determined physical parameter and the preliminarily It is possible to determine the stop time of the current layer so that it matches the set theoretical value, and to perform film formation control to stop film formation at that stop time.
A thin film forming apparatus capable of correcting the film forming control based on the substrate temperature measured by the temperature measuring unit. The control unit
Based on the substrate temperature measured by the temperature measuring unit, the temperature change in the physical properties of the film forming material during film formation is corrected, and the physical parameters are recalculated in association with the corrected physical properties of the film forming material. 9. The thin film forming apparatus according to claim 8, wherein the film forming stop time is corrected by 10. The thin film forming apparatus according to claim 9, wherein the physical properties of said film forming substance include a refractive index. The control unit
Based on the temperature coefficient set for each film-forming substance, the refractive index during film-forming is obtained,
Recalculate the optical properties of the multilayer film using the physical film thickness in the film design and the value of the refractive index obtained during film formation,
11. The thin film forming apparatus according to claim 10, wherein at least one of the designed reflection amplitude, phase, and optical film thickness used for control is recalculated to correct the film formation stop time. The control unit
Based on the film design of the multilayer film, the theoretical phase δ_design at the stop point of each layer is given in advance,
Fitting the change in transmittance over time according to the light reception signal during film formation in association with the fitting function to determine the angular velocity ω of the phase δ and the initial phase φ0,
12. The thin film forming apparatus according to any one of claims 8 to 11, wherein the film formation is stopped at a time at which the determined phase δ=ωt+φ0 during film formation coincides with the theoretical phase δ_design given in advance. The control unit
Based on the film design of the multilayer film, the theoretical equivalent reflection amplitude at the stop point of each layer is given in advance,
Fitting the change in transmittance over time according to the light reception signal during film formation in association with the fitting function to determine the equivalent reflection amplitude of the current layer during film formation of the next layer,
8. A stop time for the current layer is determined so that the absolute value of the equivalent reflection amplitude of the current layer at the time of film formation of the determined next layer coincides with the theoretical equivalent reflection amplitude, and the film formation is stopped at the stop time. 12. The thin film forming apparatus according to any one of 11 to 11. a substrate holder that is provided in the film formation chamber, holds a plurality of film formation target substrates so that the film formation surfaces face the film formation material supply unit, and rotates around the center of the holder;
the light projecting unit that projects monitor light so as to trace the plurality of film formation target substrates circularly held on the outer periphery of the rotated substrate holder;
The light receiving for receiving the monitor light transmitted through the film formation target substrate, detecting the monitor light at multiple wavelengths, and outputting a light reception signal reflecting the light transmittance of each film formation target substrate at multiple wavelengths. Department and
a trigger signal output unit that outputs a trigger signal for identifying the position of the rotating substrate holder synchronized with the rotation of the substrate holder;
The light-receiving signal and the trigger signal are input, the light-receiving signal and the trigger signal are processed, the light transmittance of each film formation target substrate is obtained, and the obtained light transmittance information is associated with each film formation target substrate. and the control unit that controls the film formation of the thin film of
The control unit
By specifying the position of the rotating substrate holder from the trigger signal synchronized with the rotation of the substrate holder, which part of the light receiving signal intermittently reflecting the light transmittance of each film formation target substrate corresponds to which part. 14. The thin film formation method according to any one of claims 8 to 13, wherein the light transmittance for each film formation target substrate is specified, and which part of the received light signal is the light transmittance for which film formation target substrate is specified. Device. a light projecting step of projecting monitor light onto a film-forming target substrate on which a film-forming material supplied from a film-forming material supply unit arranged in the film-forming chamber is formed to form a thin multi-layer film;
a light receiving step of receiving the monitor light transmitted through the film formation target substrate and acquiring a light receiving signal;
a temperature measurement step of measuring the substrate temperature during film formation;
a control step of acquiring the light transmittance of the film formation target substrate according to the light reception signal, and controlling the film formation of the thin film in association with the acquired light transmittance information;
In the control step,
With respect to the multilayer film to be formed, the multilayer film and the substrate that have already been formed are defined as one film as an equivalent film, and the square root of the reflectance between the two substances is defined as the reflection amplitude. Employing a fitting function T related to the equivalent reflected amplitude r between the current layer, the current reflected amplitude r between the current layer and air, and the phase δ,
During film formation, the measured value of the transmittance time change is associated with the fitting function and fitted to determine a physical parameter of at least one of the phase δ and the equivalent reflection amplitude r during film formation, and the determined physical parameter and the preliminarily Determine the stop time of the current layer so that it matches the set theoretical value, and perform film formation control to stop film formation at the stop time,
The optical film thickness control method, wherein the film formation control is corrected based on the substrate temperature measured in the temperature measurement step. a deposition step of supplying a deposition material from a deposition material supply unit arranged in a deposition chamber to form a thin multilayer film on a substrate to be deposited;
a projecting step of projecting monitor light onto the film formation target substrate;
a light receiving step of receiving the monitor light transmitted through the film formation target substrate and acquiring a light receiving signal;
a temperature measurement step of measuring the substrate temperature during film formation;
a control step of acquiring the light transmittance of the film formation target substrate according to the light reception signal, and controlling the film formation of the thin film in association with the acquired light transmittance information;
In the control step,
With respect to the multilayer film to be formed, the multilayer film and the substrate that have already been formed are defined as one film as an equivalent film, and the square root of the reflectance between the two substances is defined as the reflection amplitude. Employing a fitting function T related to the equivalent reflected amplitude r between the current layer, the current reflected amplitude r between the current layer and air, and the phase δ,
During film formation, the measured value of the transmittance time change is associated with the fitting function and fitted to determine a physical parameter of at least one of the phase δ and the equivalent reflection amplitude r during film formation, and the determined physical parameter and the preliminarily Determine the stop time of the current layer so that it matches the set theoretical value, and perform film formation control to stop film formation at the stop time,
A method of forming a thin film, wherein the film forming control is corrected based on the substrate temperature measured in the temperature measuring step.

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