JP6925062B1 - Optical measurement system, multilayer film manufacturing equipment and optical measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical measurement system and an optical measurement method capable of measuring the film thickness of each layer at a higher speed in a manufacturing process in which a plurality of layers are sequentially laminated. An optical measurement system exhibits optical characteristics of a light source that generates measurement light, a light receiving portion that receives reflected light or transmitted light generated by irradiating the sample with measurement light as observation light, and an optical characteristic of the uppermost layer of the sample. It includes a generator that generates a theoretical interference spectrum based on a first matrix and a second matrix that exhibits the optical properties of layers other than the top layer of the sample. The optical measurement system has a fitting unit and a fitting unit that determine the film thickness by updating the film thickness of the uppermost layer of the sample so that the theoretical interference spectrum and the measured interference spectrum, which is the spectrum of the observed light, match. Includes an update section that updates the second matrix with the film thickness determined by. [Selection diagram] FIG. 8

Description

The present invention relates to an optical measurement system for optically measuring a sample having a plurality of layers, a multilayer film manufacturing apparatus including the optical measurement system, and an optical measurement method.

High-performance devices in which a plurality of layers are laminated on a substrate have been developed and used. There is a demand to measure the film thickness of each layer during the film formation of such a high-performance device. In response to such a demand, for example, Japanese Patent Application Laid-Open No. 2019-120607 (Patent Document 1) describes a measurement object in which a plurality of first films and second films are alternately laminated on a substrate. A film thickness measuring device for measuring the film thickness of the first film and the film thickness of the second film is disclosed.

Further, Japanese Patent Application Laid-Open No. 11-160028 (Patent Document 2) discloses a film thickness measuring device capable of accurately measuring a film thickness even when the film structure cannot be specified.

JP-A-2019-120607 Japanese Unexamined Patent Publication No. 11-160028

It is necessary to manufacture high-performance devices that meet various demands, and to realize various laminated structures accordingly.

The film thickness measuring apparatus disclosed in Patent Document 1 described above compares the measured reflectance with the theoretical reflectance on the premise that the same set of the first film and the second film are laminated. It is used to determine optimization and is not applicable to high-performance devices with complex laminated structures.

Further, the film thickness measuring device disclosed in Patent Document 2 is based on the premise that the film structure that cannot be specified is relatively simple, and cannot be applied to a film structure in which a large number of layers are laminated.

One object of the present invention is to provide an optical measurement system and an optical measurement method capable of measuring the film thickness of each layer at a higher speed in a manufacturing process in which a plurality of layers are sequentially laminated.

According to an aspect of the present invention, there is provided an optical measurement system that measures one or more layers sequentially formed on a substrate by a multilayer film manufacturing apparatus as a sample. The optical measurement system includes a light source that generates measurement light, a light receiving unit that receives reflected light or transmitted light generated by irradiating the sample with measurement light as observation light, and a first matrix showing the optical characteristics of the uppermost layer of the sample. And a generator that generates a theoretical interference spectrum based on a second matrix showing the optical properties of layers other than the top layer of the sample. The first matrix includes the film thickness of the top layer of the sample as a parameter. The optical measurement system has a fitting unit and a fitting unit that determine the film thickness by updating the film thickness of the uppermost layer of the sample so that the theoretical interference spectrum and the actually measured interference spectrum, which is the spectrum of the observed light, match. Includes an update section that updates the second matrix with the film thickness determined by.

The generation unit may acquire the refractive index of the uppermost layer of the sample and determine the first matrix based on the acquired refractive index.

The first matrix defines the transmission and reflection of light at the interface between the interference matrix, which defines the phase change caused by the interference of light propagating within the top layer of the sample, and the layer adjacent to the top layer of the sample. It may include an interfacial matrix.

The optical measurement system may further include a storage unit that stores a second matrix. The update unit may update the second matrix stored in the storage unit.

The optical measurement system may further include a storage unit for storing a first matrix and a second matrix for each layer contained in the sample.

When a predetermined number of layers are formed on the substrate, the film thickness determination process by the generation unit and the fitting unit may be started.

The generator may further generate a theoretical interference spectrum based on one or more third matrices that exhibit the respective optical properties of one or more layers sequentially adjacent to each other from the top layer of the sample. The second matrix may exhibit the optical properties of the first matrix and the layer in which one or more third matrices have not been produced. Each of the one or more third matrices may include the film thickness of the corresponding layer as a parameter.

According to another aspect of the present invention, there is provided a multilayer film manufacturing apparatus having the above-mentioned optical measurement system.

According to yet another aspect of the present invention, there is provided an optical measurement method for measuring one or more layers sequentially formed on a substrate by a multilayer film manufacturing apparatus as a sample. The optical measurement method includes a step of irradiating the sample with measurement light from a light source to acquire observation light which is reflected light or transmitted light generated from the sample, a first matrix showing the optical characteristics of the uppermost layer of the sample, and a sample. Includes a step of generating a theoretical interference spectrum based on a second matrix showing the optical properties of layers other than the top layer of. The first matrix includes the film thickness of the top layer of the sample as a parameter. The optical measurement method was determined as a step of determining the film thickness by updating the film thickness of the uppermost layer of the sample so that the theoretical interference spectrum and the measured interference spectrum which is the spectrum of the observed light match. Includes a step of updating the second matrix with film thickness.

According to an embodiment of the present invention, the film thickness of each layer can be measured at a higher speed in a manufacturing process in which a plurality of layers are sequentially laminated.

It is a schematic diagram which shows the structural example of the optical measurement system according to this embodiment. It is a schematic diagram which shows the schematic structure of the spectroscopic detector used in the optical measurement system according to this embodiment. It is a schematic diagram which shows the structural example of the processing apparatus included in the optical measurement system according to this embodiment. It is a schematic diagram which shows an example of the laminated structure of the sample to be the measurement target of the optical measurement system according to this embodiment. It is a figure which shows the optical characteristic which concerns on the measurement of the film thickness of the sample which is the object of measurement of the optical measurement system according to this Embodiment. It is a schematic diagram which shows the state which the film is sequentially formed on the sample which is the measurement target of the optical measurement system according to this embodiment. It is a figure for demonstrating the method of measuring the film thickness of the sample shown in FIG. It is a flowchart which shows the processing procedure which concerns on the film thickness measurement of the sample in the optical measurement system according to embodiment of this invention. It is a schematic diagram which shows an example of the functional structure provided by the optical measurement system according to this embodiment. It is a schematic diagram which shows an example of the method of updating the synthetic matrix in the optical measurement system according to the Embodiment of this invention. It is a sequence diagram which shows an example of the interface between the processing apparatus and the multilayer film manufacturing apparatus in the optical measurement system according to embodiment of this invention. It is a figure for demonstrating another method for measuring the film thickness of the sample shown in FIG.

Embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

<A. Optical measurement system>
First, a configuration example of the optical measurement system 1 according to the present embodiment will be described. The optical measurement system 1 is a spectroscopic interference type film thickness measuring device. In the following, the optical system that irradiates the sample with light and observes the reflected light (reflected light observation system) will be mainly described, but the optical system that irradiates the sample with light and observes the transmitted light (transmitted light observation system). ) Is also applicable as a matter of course.

As used herein, "film thickness" means the thickness of a particular layer or film contained in any sample.

FIG. 1 is a schematic view showing a configuration example of an optical measurement system 1 according to the present embodiment. The optical measurement system 1 may be configured integrally with the multilayer film manufacturing apparatus 50, or may be configured to be mounted on the multilayer film manufacturing apparatus 50 after the fact. When integrally configured, a multilayer film manufacturing apparatus 50 including an optical measurement system 1 may be provided.

The multilayer film manufacturing apparatus 50 is typically a film forming apparatus that sequentially forms a plurality of layers on a substrate. As the film to be formed, a dielectric film, an oxide film, a nitride film, or the like is typically assumed. Since the configuration of the film forming apparatus is known, detailed description thereof will not be given here. The optical measurement system 1 measures one or a plurality of layers sequentially formed on the substrate by the multilayer film manufacturing apparatus 50 as a sample 3. Here, the sample 3 may include a substrate.

The optical measurement system 1 is a spectroscopic detection unit that receives a light source 10 that generates measurement light for irradiating the sample 3 and an observation light (reflected light or transmitted light) generated by irradiating the sample 3 with the measurement light. A device 20 and a processing device 100 into which the detection result of the spectroscopic detector 20 is input are included.

The processing apparatus 100 calculates the measurement result (typically, the film thickness) of the sample 3 based on the detection result of the spectroscopic detector 20. The processing device 100 also exchanges necessary information with the multilayer film manufacturing device 50.

The light source 10 and the spectroscopic detector 20 are optically connected via a Y-shaped fiber 4 having an irradiation port toward the sample 3. In the optical measurement system 1, the sample 3 is irradiated with the measurement light from the light source 10, and the film thickness of the sample 3 is measured by observing the light appearing due to the optical interference generated inside the sample 3.

The light source 10 generates measurement light having a predetermined wavelength range. The wavelength range of the measurement light is determined according to the range of wavelength information to be measured from the sample 3. As the light source 10, for example, a halogen lamp, a white LED, or the like is used. The light source 10 may generate measurement light including a component in the near infrared region. In this case, an ASE (Amplified Spontaneous Emission) light source may be adopted as the light source 10.

FIG. 2 is a schematic diagram showing a schematic configuration of a spectroscopic detector 20 used in the optical measurement system 1 according to the present embodiment. With reference to FIG. 2, the spectroscopic detector 20 outputs the intensity of the observed light for each wavelength in a predetermined wavelength range.

More specifically, the spectroscopic detector 20 includes a diffraction grating 22 that diffracts light incident on the Y-shaped fiber 4, a light receiving element 24 having a plurality of channels arranged in association with the diffraction grating 22, and light receiving. It is electrically connected to the element 24 and includes an interface circuit 26 for outputting a detection result to the processing device 100. The light receiving element 24 is composed of a line sensor, a two-dimensional sensor, or the like, and can output the intensity of each frequency component as a detection result.

FIG. 3 is a schematic view showing a configuration example of a processing device 100 included in the optical measurement system 1 according to the present embodiment. With reference to FIG. 3, the processing unit 100 includes a processor 102, a main memory 104, an input unit 106, a display unit 108, a storage 110, a communication interface 120, a network interface 122, and a media drive 124. include.

The processor 102 is typically an arithmetic processing unit such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), and reads one or a plurality of programs stored in the storage 110 into the main memory 104 and executes them. do. The main memory 104 is a volatile memory such as a DRAM (Dynamic Random Access Memory) or a SRAM (Static Random Access Memory), and functions as a working memory for the processor 102 to execute a program.

The input unit 106 includes a keyboard, a mouse, and the like, and accepts operations from the user. The display unit 108 outputs the execution result of the program by the processor 102 to the user.

The storage 110 is composed of a non-volatile memory such as a hard disk or a flash memory, and stores various programs and data. More specifically, the storage 110 stores an operating system 112 (OS: Operating System), a measurement program 114, a detection result 116, and a measurement result 118.

The operating system 112 provides an environment in which the processor 102 executes a program. The measurement program 114 is executed by the processor 102 to realize an optical measurement method or the like according to the present embodiment. The detection result 116 includes data output from the spectroscopic detector 20. The measurement result 118 includes the measurement result obtained by executing the measurement program 114.

The communication interface 120 mediates data transmission between the processing device 100 and the spectroscopic detector 20. The network interface 122 mediates data transmission between the processing apparatus 100 and the multilayer film manufacturing apparatus 50.

The media drive 124 reads necessary data from a recording medium 126 (for example, an optical disk) storing a program or the like executed by the processor 102 and stores it in the storage 110. The measurement program 114 or the like executed by the processing device 100 may be installed via the recording medium 126 or the like, or may be downloaded from the server device via the network interface 122 or the like.

The measurement program 114 may call the necessary modules in a predetermined array at a predetermined timing among the program modules provided as a part of the operating system 112 to execute the process. In such a case, the measurement program 114 that does not include the module is also included in the technical scope of the present invention. The measurement program 114 may be provided by being incorporated into a part of another program.

A hard-wired logic circuit (for example, FPGA (field-programmable gate array), ASIC (application specific integrated circuit), etc.) provides all or part of the functions provided by the processor 102 of the processing device 100 executing the program. It may be realized by. Further, in addition to a processor such as a CPU or GPU, a SoC (System on Chip) in which a DSP (Digital Signal Processor) and an ISP (Image Signal Processor) are integrated may be used.

<B. Film thickness measurement>
Next, a theoretical explanation will be given regarding the measurement of the film thickness of each layer contained in the sample 3 and the sample 3 which are the measurement targets of the optical measurement system 1.

FIG. 4 is a schematic view showing an example of the laminated structure of the sample 3 to be measured by the optical measurement system 1 according to the present embodiment. With reference to FIG. 4, in the sample 3, a plurality of layers 32 are sequentially formed on a substrate 30 such as glass. The optical measurement system 1 sequentially measures the film thickness of the layer 32 formed in the process of sequentially forming the layer 32.

FIG. 5 is a diagram showing optical characteristics related to the measurement of the film thickness of the sample 3 to be measured by the optical measurement system 1 according to the present embodiment.

With reference to FIG. 5 (A), the complex refractive index of the jth (1 ≦ j ≦ L) layer is defined _{as N j} (= n _j −ik _j). Further, the incident angle theta _j of the j-th _layer, the j-th layer of thickness d _j, and the wavelength lambda. Note that i is an imaginary unit.

Figure 5 in correspondence with the complex refractive index N _j of (A), a shown in FIG. 5 (B), the interference matrix M _j of the j-th _layer, and, j-th layer and the j-1 th layer The interface matrix I _{j, j-1} between and is defined.

The interference matrix _Mj is a matrix that defines the phase change caused by the interference of light propagating in the layer of interest (the jth layer). It is a 2x2 matrix to define the behavior of the incident light and the reflected light.

The interface matrix I _{j, j-1} is a matrix that defines the transmission and reflection of light at the interface with the layer (j-1st layer) adjacent to the layer of interest (jth layer). It is a 2x2 matrix to define the behavior of the incident light and the reflected light.

Here, the substrate 30 is regarded as the 0th layer. Therefore, I _1,0 indicates an interface matrix between the first layer and the substrate 30 (0th layer). Further, the interface matrix of L-th layer is atmosphere layer A _m and the top layer I _Am, as _L, is defined separately.

A scattering matrix S as shown in the following equation (1) can be defined for the sample 3 having a laminated structure in which a plurality of layers are formed. That is, the scattering matrix S is calculated as the inner product of the interference matrix M and the interface matrix I (the interface matrix _{includes I Am and L) for all the layers contained in the sample 3.}

As shown in the equation (2), when each element of the scattering matrix S (2 × 2 matrix) is defined, the intensity reflectance R of the sample 3 having a laminated structure in which a plurality of layers are formed is as shown in the equation (3). Can be calculated. The film thicknesses of the plurality of layers 32 included in the sample 3 are the spectrum of the observed light (reflected light) generated by irradiating the sample 3 with the measurement light (hereinafter, also referred to as “measured interference spectrum”) and the equation (3). A parameter (mainly) for determining Eq. (3) so as to match the theoretical interference spectrum (hereinafter, also referred to as “theoretical interference spectrum”) calculated using the theoretical intensity reflectance calculated according to. , The film thickness of each layer) can be optimized.

_{The interference matrix M j} and the interface matrix I _{j, j-1} included in the equation (1) are the phase factor β _j of the corresponding jth layer, and the amplitude between the jth layer and the j-1st layer. It is defined using the reflectances r _{j, j-1 , and the amplitude transmittance s j, j-1} between the jth layer and the j-1st layer.

More specifically, as shown in Eq. (4-1), the interference matrix M _j can be defined _{using the phase factor β j.} Further, as shown in Eq. (4-2), the interface matrix I _{j, j-1} can be defined _{by using the amplitude reflectance r j, j-1} and the amplitude transmittance s _{j, j-1.}

Here, the phase factor beta _j, (5-1) as shown in the expression can be defined using the thickness d _j of the j-th layer. _{The incident angle θ j} of the j-th layer included in the phase factor β _j is defined as shown in Eq. (5-2) using the incident angle θ _Am.

Further, the amplitude reflectance r _{j, j-1} and the amplitude transmittance s _{j, j-1} correspond to the Fresnel coefficient, and (6-1) to (6-4) for each case of p-polarized light and s-polarized light. ) Is defined as an expression.

When the incident angle θ _Am is non-zero (θ _Am ≠ 0), the intensity reflectance for each of s-polarized light and p-polarized light (intensity reflectance Rs for s-polarized light and intensity reflectance Rp for p-polarized light) is calculated. do. Finally, as shown in Eq. (7), the average intensity reflectance for each polarized light is determined as the theoretical intensity reflectance R of sample 3.

By fitting the theoretical interference spectrum calculated using the finally determined theoretical intensity reflectance R and the actually measured interference spectrum actually obtained from the sample 3, the film thickness of each layer included in the sample 3 is formed. The thickness can be determined.

The optical measurement system 1 according to the present embodiment measures the film thickness in the manufacturing process in which new layers are sequentially formed on the substrate. Therefore, basically, only the uppermost layer is the film thickness to be measured. In the present specification, the "top layer" means the layer in which the measurement light is first incident among the layers included in the sample.

FIG. 6 is a schematic view showing a state in which a film is sequentially formed on a sample 3 which is a measurement target of the optical measurement system 1 according to the present embodiment. As shown in FIG. 6 (A), it is assumed that the L + 1th layer is newly formed with respect to the sample 3 in which L layers are laminated, as shown in FIG. 6 (B).

In this case, as a component of the scattering matrix S of the sample 3, the interface matrix _{I Am} the L + 1 th layer is atmosphere layer _{A m} and the top _{layer, L + 1,} the interference matrix _{M L + 1,} and, the interface matrix _{I L + 1, L} Three are newly added. The interference matrix M and the interface matrix I for the other layers remain unchanged.

Therefore, in fitting, only the parameters included in these three matrices need to be optimized. Here, the inner product of the interference matrix M and the interface matrix I from the first layer to the L-th layer, as shown in the following (8-1) equation, the matrix P _L. Further, each element of the synthetic matrix _{P L} can be defined as the following (8-2) equation.

When using a synthetic matrix _{P L,} scattering matrix _{S L + 1} can be defined as the following (8-3) equation. As shown in Eq. (8-4) _{, when each component of the scattering matrix SL + 1 is defined, the intensity reflectance RL + 1} of the laminated structure sample 3 in which L + 1 layers are formed is obtained by Eq. (8-5). Can be calculated as follows.

In this way, when a plurality of layers are sequentially formed on the substrate, the interference matrix M and the interface matrix I of the already formed layers are used as they are, and only the parameters related to the newly formed layer are optimized. do it.

When the above equation (8-3) is expanded using the phase factor, the amplitude reflectance, and the amplitude transmittance, the following equation (9) is obtained.

The optical measurement system 1 uses the recurrence formula shown in Eq. (9) to sequentially optimize the parameters related to the layers sequentially formed on the substrate, thereby forming the film thickness and the laminated structure of the sample 3 having a plurality of layers. Can be identified.

FIG. 7 is a diagram for explaining a method of measuring the film thickness of the sample 3 shown in FIG. FIG. 7A shows a state in which the L + 1th layer is newly formed with respect to the sample 3 in which L layers are laminated, as in FIG. 6B. At this time, as shown in FIG. 7B, the first to Lth layers can theoretically be regarded as a single layer (synthesized single layer). The single layer will have a synthetic matrix P _L as the optical properties. Using synthetic matrix P _L, measures the thickness of the layer (L + 1 layer) to be newly formed.

In the following description, referred to the layer 32 of the s-th from the first (s ≧ 1), the matrix obtained by combining the interference matrix M and the interface matrix I "synthetic matrix P _s". The synthetic matrix P _s is a 2 × 2 matrix and includes four elements _{, P s_11} , P _{s_12} , P _{s_21} , and P _{s_22.}

_{As shown in the above equation (8-3), the matrix (IAm, L + 1} , ML _{+ 1} , _{IL + 1, L} ) showing the optical characteristics of the uppermost layer of the sample 3 and the optics of the layers other than the uppermost layer of the sample 3 scattering matrix _{S L + 1} is determined based on the matrix _{(P L)} indicating the characteristics. Here, the matrix showing the optical characteristics of the uppermost layer of _{the sample 3 is adjacent to the interference matrix ML + 1} , which defines the phase change caused by the interference of light propagating in the uppermost layer of the sample 3, and the uppermost layer of the sample 3. _{Includes interface matrices I Am, L + 1} , _{IL + 1, L} , which define the transmission and reflection of light at the interface with the layer.

A theoretical interference spectrum will be generated from the scattering matrix _{SL + 1.} Here, as shown in Eq. (9), the matrix ( _{IAm, L + 1} , ML _{+ 1} , _{IL + 1, L} ) showing the optical characteristics of the uppermost layer of the sample 3 has a film thickness d _L of the uppermost layer of the sample 3. It will be included as a parameter (see the above equations (4-1) and (5-1), etc.).

<C. Measurement processing procedure>
Next, the processing procedure related to the film thickness measurement of the sample 3 by the optical measurement system 1 according to the present embodiment will be described.

FIG. 8 is a flowchart showing a processing procedure related to film thickness measurement of sample 3 in the optical measurement system 1 according to the embodiment of the present invention. The processing procedure shown in FIG. 8 is typically realized by the processor 102 of the processing apparatus 100 executing the measurement program 114.

With reference to FIG. 8, the processing apparatus 100 acquires the initial settings (step S2). The default setting is the incident angle theta _Am of the measuring light, the complex refractive index _N 0 of the substrate 30 and the ₍₌ n ₀ -ik 0), and an atmosphere layer _{A m} of the complex refractive index _{N Am (= n Am -ik Am} ) including. Processor 100 initializes the identity matrix composite matrix _P s (s = 1) (step S4).

The processing device 100 determines whether or not a measurement start instruction has been received from the multilayer film manufacturing device 50 (step S6). If the measurement start instruction is not received from the multilayer film manufacturing apparatus 50 (NO in step S6), the process of step S6 is repeated.

If the measurement start instruction is received from the multilayer film manufacturing apparatus 50 (YES in step S6), the processing apparatus 100 _{acquires the complex refractive index N s} (= n _s −ik _s ) of the uppermost layer of the sample 3 (YES in step S6). Step S8). For example, the measurement start instruction may include information that identifies the type (material, etc.) of the film (top layer) to be measured. The subscript s means the number of the uppermost layer of the current sample 3. The initial value of s is "1".

_{The processing apparatus 100 has an amplitude reflectance r Am, s} and an amplitude transmittance s _{Am, s} between the atmosphere layer and the uppermost layer, and an amplitude reflection between the uppermost layer and the layer on the substrate side adjacent to the uppermost layer. The rates r _{s, s-1} and the amplitude transmittances s _{s, s-1} are calculated (step S10). Regarding the layer first formed on the substrate (that is, s = 1), the layer on the substrate side adjacent to the uppermost layer is the substrate itself.

The processing device 100 acquires an actually measured interference spectrum, which is a spectrum generated by irradiating the sample 3 arranged at the measurement position with the measurement light (step S12). In this way, the process of irradiating the sample 3 with the measurement light from the light source 10 and acquiring the observed light which is the reflected light or the transmitted light generated from the sample 3 is executed.

Processor 100 sets an initial value to the top layer of thickness _{d s} (step S14), and calculates the corresponding phase factor beta _s (step S16). The processing apparatus 100 includes the current synthetic matrix P _s , the amplitude reflectance r _{Am, s} , rs _{, s-1} calculated in step S10, and the amplitude transmittance s _{Am, s} , s _{s, s-1,} and the step. The scattering matrix S _s is calculated using the phase factor β _s calculated in S16 (step S18). In step S18, the amplitude reflectance and the amplitude transmittance are calculated for each of the cases of p-polarized light and s-polarized light.

The processing apparatus 100 calculates _{the intensity reflectance R s} of the sample 3 based on the elements of _{the scattering matrix S s} calculated in step S18 (step S20). The calculated intensity reflectance R _s shows the theoretical interference spectrum of sample 3. Thus, processing device 100, the matrix indicating the uppermost layer of the optical characteristics of the sample _{3 (I Am, s, M} s, I s, s-1) and the optical properties of the top layer other than the layer of the sample 3 generating a theoretical interference spectrum based on the matrix (P _s) shown.

The processing apparatus 100 calculates an error (for example, sum of squares) between the theoretical interference spectrum of the sample 3 calculated in step S20 and the actually measured interference spectrum of the sample 3 acquired in step S12 (step S22), and calculates the error. It is determined whether or not the convergence condition is satisfied based on the size (step S24).

Does not satisfy the convergence condition (NO in step S24), and the processing device 100, the current value of the top layer having a thickness _{d s} and updated in accordance with the error (step S26), step S16 and repeats the process. Thus, processing device 100, such that the measured interference spectrum is a spectrum of theoretical interference spectrum and the observed light matches, by updating the uppermost layer having a thickness d _s of the sample 3, the thickness d _s Determine the value.

If it meets the convergence condition (YES at step S24), and the processing unit 100 outputs the measurement result of the current value of the top layer having a thickness _{d s} (step S28). Then, the processing unit 100 based on the determined thickness _{d s,} and updates the value of the composite matrix _{P s} (step S30). Thus, processor 100 uses the determined thickness d _s, as showing optical characteristics of the entire layer in the sample 3, and it updates the synthetic matrix P _s.

The processing device 100 determines whether or not the measurement completion notification has been received from the multilayer film manufacturing device 50 (step S32). If the measurement completion notification is not received from the multilayer film manufacturing apparatus 50 (NO in step S32), the process of step S6 is repeated.

If the measurement completion notification is received from the multilayer film manufacturing apparatus 50 (YES in step S32), the processing apparatus 100 ends the processing.

The film thickness of the layers sequentially formed on the substrate is measured by the processing procedure as described above.
<D. Functional block diagram>
FIG. 9 is a schematic diagram showing an example of the functional configuration provided by the optical measurement system 1 according to the present embodiment. Each function shown in FIG. 9 is typically realized by the processor 102 of the processing device 100 executing the measurement program 114.

With reference to FIG. 9, the processing apparatus 100 has, as a functional configuration, a buffer 150, a theoretical interference spectrum generation module 152, a fitting module 154, an output module 156, a working data storage module 158, a selection module 160, and the like. It includes an optical data storage unit 162 and a synthesis matrix update module 164.

The buffer 150 stores the detection result (measured interference spectrum) output from the spectroscopic detector 20.

The theoretical interference spectrum generation module 152 calculates the scattering matrix S corresponding to the sample 3 to be measured and the corresponding theoretical interference spectrum based on the information stored in the working data storage module 158. At this time, the theoretical interference spectrum generation module 152 acquires the complex refractive index of the uppermost layer of sample 3, and based on the acquired complex refractive index, a matrix ( _{IAm, s) showing the optical characteristics of the uppermost layer of sample 3.} , _Ms , _{Is, s-1} ).

The fitting module 154 calculates an error between the actually measured interference spectrum stored in the buffer 150 and the theoretical interference spectrum calculated by the theoretical interference spectrum generation module 152, and updates the film thickness of the fitting target based on the error. do. If the error between the measured interference spectrum and the theoretical interference spectrum satisfies the convergence condition, the fitting module 154 determines the film thickness at that time as the measurement result. As a method for evaluating the match between the actually measured interference spectrum and the theoretical interference spectrum, the least squares method or the optimization method can be adopted.

In this way, the fitting module 154 determines the film thickness by updating the film thickness of the uppermost layer of the sample 3 so that the theoretical interference spectrum and the actually measured interference spectrum which is the spectrum of the observed light match.

The working data storage module 158, the initial setting (the measurement light incident angle theta _Am, complex refractive index _{N 0} of the substrate, such as the complex refractive index _{N Am} atmosphere layer _{A m),} synthetic matrix P, the layer to be measured (highest The complex refractive index of the upper layer) is stored.

The selection module 160 responds to information specifying the type (material, etc.) of the layer (top layer) to be measured from the multilayer film manufacturing apparatus 50 from the set of optical data stored in the optical data storage unit 162. Select the corresponding optical data.

The optical data storage unit 162 stores optical data (complex refractive index, etc.) corresponding to each layer that can be formed in the multilayer film manufacturing apparatus 50.

When the film thickness of the measurement target is determined by the fitting module 154, the synthetic matrix update module 164 updates the value of the synthetic matrix P stored in the working data storage module 158 based on the determined film thickness. .. As described above, the synthetic matrix update module 164 updates the synthetic matrix P (second matrix) so as to show the optical characteristics of the entire layer contained in the sample 3 by using the film thickness determined by the fitting module 154. do.

<E. Update Synthetic Matrix>
In the optical measurement system 1 according to the present embodiment, when the film thickness measurement of the uppermost layer is completed, the value of the synthetic matrix P is sequentially updated (or sequentially calculated). An implementation form of such an update of the synthetic matrix P will be described.

FIG. 10 is a schematic diagram showing an example of a method for updating the synthetic matrix in the optical measurement system 1 according to the embodiment of the present invention.

FIG. 10 (A) shows a method of storing substantially only the latest synthetic matrix. When the film thickness of an arbitrary top layer (L + 1st layer) is measured, the interference matrix 172 (for the L + 1st layer) and the interface matrix 174 (the interface between the L + 1st layer and the Lth layer) calculated in the measurement are measured. Synthetic matrix 170A (inner product of interference matrix up to Lth and interface matrix) to measure the next new film thickness using synthetic matrix 170B (inner product of interference matrix and interface matrix up to L + 1). Update to.

As shown in FIG. 10A, the processing apparatus 100 has a storage unit for storing the synthetic matrix 170. The synthetic matrix update module 164 (FIG. 9) updates the synthetic matrix 170 stored in the storage unit. By adopting the method of storing only the latest synthetic matrix 170 that is sequentially updated in this way, the film thickness measurement can be continued with a small amount of data.

FIG. 10B shows an example in which a pair of the synthetic matrix 170, the interference matrix 172, and the interface matrix 174 is stored for each measured layer. Also in this example, the synthetic matrix 170 for a layer is calculated by multiplying the synthetic matrix 170 for the previously measured layer by the inner product of the interference matrix 172 and the interface matrix 174.

As shown in FIG. 10B, the processing apparatus 100 has a storage unit for storing the interference matrix 172, the interface matrix 174, and the synthetic matrix 170 for each layer included in the sample 3. By adopting such a data structure, ex-post verification can be easily performed.

<F. Interface between processing device 100 and multilayer film manufacturing device 50>
Next, an example of the interface between the processing apparatus 100 and the multilayer film manufacturing apparatus 50 will be described.

FIG. 11 is a sequence diagram showing an example of an interface between the processing device 100 and the multilayer film manufacturing device 50 in the optical measurement system 1 according to the embodiment of the present invention.

With reference to FIG. 11, first, in the multilayer film manufacturing apparatus 50, a substrate to be formed of a film is set (sequence SQ2). Then, the multilayer film manufacturing apparatus 50 transmits the initial setting including the information about the substrate to the processing apparatus 100 (sequence SQ4). The processing apparatus 100 stores the initial settings from the multilayer film manufacturing apparatus 50 and calculates the parameters required for the measurement.

In the multilayer film manufacturing apparatus 50, a process of forming a film on the set substrate is executed (sequence SQ6). When the formation of an arbitrary film is completed, the multilayer film manufacturing apparatus 50 transmits a measurement start instruction to the processing apparatus 100 (sequence SQ8).

The processing apparatus 100 measures the film thickness of the target film (the uppermost film) (sequence SQ10). The processing device 100 transmits the measurement result (film thickness) obtained by the film thickness measurement to the multilayer film manufacturing device 50 (sequence SQ12).

The multilayer film manufacturing apparatus 50 determines the suitability of the formed film based on the measurement result (film thickness) from the processing apparatus 100 (sequence SQ14). For example, it is determined whether or not the film thickness of the formed film is within a predetermined range. If the film thickness of the formed film exceeds a predetermined range, the target work may be discarded. On the contrary, when the film thickness of the formed film is less than a predetermined range, the film formation may be restarted. In this case, the multilayer film manufacturing apparatus 50 may transmit the measurement start instruction to the processing apparatus 100 again.

Basically, the processing (* 1) of the sequences SQ6 to SQ14 is repeated as many times as the number of films formed on the substrate.

When the formation of a predetermined number of films on the substrate is completed (sequence SQ16), the multilayer film manufacturing apparatus 50 transmits a measurement completion notification to the processing apparatus 100 (sequence SQ18).

By the above processing procedure, a series of film thickness measurement processing is completed.
The measurement start instruction may include information for specifying the type (material, etc.) of the film (top layer) to be measured. Alternatively, the order (profile) of the film formed on the substrate may be stored in advance, and the type of film to be measured may be specified according to the profile.

Further, in the interface shown in FIG. 11, it is assumed that the film thickness is measured after the formation of an arbitrary film is completed, but the film thickness can be measured in real time during the formation of the film. In this case, the synthetic matrix may be updated at the timing when the formation of the uppermost film is completed and the formation of another type of film is started.

<G. Modification example>
(G1: Applicable from a predetermined number of layers)
In the above-mentioned film thickness measurement process, the uppermost film is the measurement target, and in the fitting between the theoretical interference spectrum and the actually measured interference spectrum, only the film thickness of the uppermost film is made variable, and the films of the other layers are made variable. An example in which the thickness is fixed (reflected as a composite matrix of fixed values) is shown, but when the number of formed layers is small, the film thickness of each layer may be used as a fitting target. As the fitting method, a method as disclosed in Japanese Patent No. 5721586 may be adopted.

Although it depends on the processing capacity of the processing apparatus 100, for example, the film thicknesses of a plurality of layers may be optimized for up to about 5 to 6 layers. Then, when more layers are formed, using the synthetic matrix as described above, the entire layer except the uppermost layer is regarded as a single layer, and the process is switched to the process of measuring the film thickness of the uppermost layer. May be good.

In this way, after a predetermined number of layers are formed on the substrate, the process of determining the film thickness of the sample 3 may be started by the method as described above.

(G2: Fitting target for multiple layers including the top layer)
In the above-mentioned film thickness measurement process, the method of calculating the theoretical interference spectrum by focusing on the uppermost film has been described, but a plurality of layers including the uppermost layer may be the fitting target.

FIG. 12 is a diagram for explaining another method for measuring the film thickness of the sample shown in FIG. FIG. 12A shows a state in which the L + 1th layer is newly formed with respect to the sample 3 in which L layers are laminated. For example, as shown in FIG. 12B, two layers (L layer and L-1 layer) adjacent to the L + 1th layer of the uppermost layer are treated as independent layers, and the other layers are treated as independent layers. Theoretically, it is regarded as a single layer (synthesized single layer).

As a result, the sample 3 can be regarded as a laminated structure composed of four layers formed on the substrate. Then, the theoretical interference spectrum is calculated using the film thicknesses of these four layers as parameters, and the film thickness of each layer of the sample 3 is updated so as to match the measured interference spectrum. The laminated structure of the sample 3 including the thickness d _{L + 1 can be determined.}

In this case, a matrix showing the optical characteristics of the uppermost layer (L + 1st layer) (interference matrix ML _{+ 1} and an interface matrix _{IL + 1, L} ) and a matrix showing the optical characteristics of a single layer (synthetic matrix PL _-2). in addition to) a matrix showing the optical properties of the layer adjacent to the top layer (L th layer) (interference matrix M _L and surfactant matrix I _{L, L-1),} and, further adjacent layer (L-1 th _{A matrix (interference matrix ML-1} and interface matrix _{IL-1, L-2} ) showing the optical characteristics of the layer) is used.

As described above, the theoretical interference spectrum is generated based on one or a plurality of matrices (interference matrix M and interface matrix I) showing the optical characteristics of one or a plurality of adjacent layers sequentially from the top layer of the sample 3. .. In this case, the synthetic matrix P exhibits optical properties other than the layers in which the interference matrix M and the interface matrix I are not generated (that is, the top layer of sample 3 and one or more layers sequentially adjacent to the top layer). Become. Then, the film thickness of each of the uppermost layer and one or a plurality of layers sequentially adjacent to the uppermost layer is the fitting target.

As the fitting method, a method as disclosed in Japanese Patent No. 5721586 may be adopted.

When the film thickness of each layer is determined by the fitting, the film thickness of the layer closest to the substrate (L-1st layer in the example shown in FIG. 12) among the layers to be fitted in the sample 3 is used. the value of the composite matrix P _L is updated. Synthetic matrix P _L after updating will exhibit the optical characteristics of the first layer to the L-1 th layer.

By adopting such a method, it is possible to improve the measurement accuracy of the film thickness by fitting for a predetermined number of layers from the top layer, and for the other layers, even if the number of layers is large, it is single. Since it can be regarded as a layer, even when the number of layers increases, higher measurement accuracy can be maintained without increasing the amount of calculation.

(G3: Update of synthetic matrix)
In the above description, when the uppermost layer is formed, the process of updating the synthetic matrix each time based on the film thickness obtained by measuring the formed uppermost layer has been illustrated, but the synthetic matrix is updated. The timing and conditions can be set arbitrarily. For example, the synthetic matrix may be updated every other layer or every plurality of layers.

As a specific example, when layers made of two different materials are alternately formed on the substrate, a first layer made of the first material and a second layer made of the second material are formed. The synthetic matrix may be updated at the timing when the pair with is formed. That is, at the timing when the first layer made of the first material is formed as the uppermost layer, the synthetic matrix is not updated, and at the timing when the pair of the first layer and the second layer is formed, the first layer is formed. The synthetic matrix may be updated based on the film thickness of each of the first layer and the second layer.

Similarly, when three or more layers made of three or more different materials are sequentially formed on the substrate as one set, the synthetic matrix is formed at the timing when the formation of the one set is completed. You may try to update.

In this way, the timing and conditions for updating the synthetic matrix may be set depending on the laminated structure of the sample.

Alternatively, the synthetic matrix may be updated according to a profile arbitrarily set in advance. Such a profile, for example, should be fitted as closely as possible to a particular layer or layers that have a significant impact on sample quality, while the optics of the layers that have a relatively small impact on sample quality. By positively including the characteristics in the synthetic matrix, the amount of calculation can be reduced while maintaining the measurement accuracy of the film thickness.

(G4: Computing resource)
In the above description, a configuration example in which the processing device 100 of the optical measurement system 1 executes necessary processing has been described, but the present invention is not limited to this, and for example, the processing may be shared by a plurality of processing devices. The spectroscopic detector 20 may be in charge of the processing of the unit. Further, a computing resource (so-called cloud) on a network (not shown) may be responsible for all or part of the required processing.

<H. Summary>
In the optical measuring apparatus according to the present embodiment, for a sample in which one or a plurality of layers are sequentially formed on a substrate, an interference matrix and an interface matrix showing the optical characteristics of the top layer of the sample, and other than the top layer of the sample. A theoretical interference spectrum is generated based on a synthetic matrix showing the optical characteristics of the layers of the above layer, and the film thickness of the uppermost layer of the sample is updated so that the theoretical interference spectrum and the measured interference spectrum match. To determine. By regarding the film that has been formed first as a single layer having a synthetic matrix as an optical characteristic, it is possible to reduce the amount of calculation for the process of determining the film thickness and speed up the process.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Optical measurement system, 3 samples, 4 Y-type fiber, 10 light sources, 20 spectroscopic detectors, 22 diffraction grids, 24 light receiving elements, 26 interface circuits, 30 substrates, 32 layers, 50 multilayer film manufacturing equipment, 100 processing equipment, 102 Processor, 104 main memory, 106 input, 108 display, 110 storage, 112 operating system, 114 measurement program, 116 detection result, 118 measurement result, 120 communication interface, 122 network interface, 124 media drive, 126 recording medium, 150 Buffer, 152 Theoretical Interference Spectrum Generation Module, 154 Fitting Module, 156 Output Module, 158 Working Data Storage Module, 160 Selection Module, 162 Optical Data Storage Module, 164 Synthetic Matrix Update Module, 170, 170A, 170B Synthetic Matrix, 172 Interference Matrix 174 interface matrix.

Claims (8)

An optical measurement system that measures one or more layers sequentially formed on a substrate by a multilayer film manufacturing apparatus as a sample.
A light source that generates measurement light and
A light receiving unit that receives reflected light or transmitted light generated by irradiating the sample with the measurement light as observation light.
A first matrix newly formed in the sample showing the optical characteristics of the uppermost layer and one or more second matrices showing the optical characteristics of one or more adjacent layers sequentially from the uppermost layer of the sample. And a generation unit that generates a theoretical interference spectrum based on the first matrix and a third matrix in which the one or more second matrices show the optical characteristics of layers other than the corresponding layers. The first matrix contains the thickness of the top layer of the sample as a parameter, and each of the one or more second matrices contains the thickness of the corresponding layer as a parameter.
By updating the film thickness of each of the first matrix and the one or more second matrices so that the theoretical interference spectrum and the actually measured interference spectrum which is the spectrum of the observed light match. The fitting part that determines the respective film thickness and
A single layer obtained by synthesizing at least the lowest layer of the layer corresponding to the third matrix and the layer corresponding to the one or a plurality of second matrices using the film thickness determined by the fitting portion. With an update section that updates the third matrix to show the optical properties of the single layer .
When a predetermined number of layers are formed on the substrate, the film thickness determination process by the generation unit and the fitting unit is started.
When a predetermined number of layers from the bottom layer are included as layers corresponding to the second matrix due to the formation of the sample, the renewal unit collects a predetermined number of layers from the bottom layer and collects the third matrix. to update as, optical measurement system. The optical measurement system according to claim 1 , wherein the number of elements of the third matrix is maintained before and after the update. The optical measurement system according to claim 1 or 2 , wherein the generation unit acquires the refractive index of the uppermost layer of the sample and determines the first matrix based on the acquired refractive index. The first matrix transmits and reflects light at the interface between an interference matrix that defines the phase change caused by the interference of light propagating within the top layer of the sample and a layer adjacent to the top layer of the sample. The optical measurement system according to any one of claims 1 to 3 , which includes an interfacial matrix that defines. A storage unit for storing the third matrix is further provided.
The optical measurement system according to any one of claims 1 to 4 , wherein the updating unit updates the third matrix stored in the storage unit. Each layer included in the sample, said first matrix further comprises a storage unit for storing said one or more second matrix and the third matrix, according to any one of claims 1-4 Optical measurement system. A multilayer film manufacturing apparatus comprising the optical measurement system according to any one of claims 1 to 6. An optical measurement method for measuring one or more layers sequentially formed on a substrate by a multilayer film manufacturing apparatus as a sample.
A step of irradiating the sample with measurement light from a light source and acquiring observation light which is reflected light or transmitted light generated from the sample.
A first matrix newly formed in the sample showing the optical characteristics of the uppermost layer and one or more second matrices showing the optical characteristics of one or more adjacent layers sequentially from the uppermost layer of the sample. A step of generating a theoretical interference spectrum based on the first matrix and a third matrix in which the one or more second matrices show the optical properties of layers other than the corresponding layers. The matrix of 1 includes the film thickness of the uppermost layer of the sample as a parameter, and each of the one or a plurality of second matrices includes the film thickness of the corresponding layer as a parameter.
By updating the film thickness of each of the first matrix and the one or more second matrices so that the theoretical interference spectrum and the actually measured interference spectrum which is the spectrum of the observed light match. Steps to determine the respective film thickness and
Using the determined film thickness, the layer corresponding to the third matrix and at least the lowest layer of the layers corresponding to the one or more second matrices are regarded as a single layer synthesized. , With the step of updating the third matrix to show the optical properties of the single layer .
The generating step, the determining step, and the updating step are started when a predetermined number of layers are formed on the substrate.
In the updating step, when a predetermined number of layers from the bottom layer are included as the layers corresponding to the second matrix due to the formation of the sample, the predetermined number of layers from the bottom layer are put together and the third layer is combined. An optical measurement method that includes steps to update as a matrix.

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