Optical measurement system, multilayer film manufacturing apparatus, and optical measurement method

Abstract

The present application relates to an optical measurement system, a multilayer film manufacturing apparatus, and an optical measurement method. The optical measurement system includes a light source for generating measurement light, a light receiving section that receives reflected light or transmitted light generated by irradiating measurement light to a sample as observation light, and a generation section that generates a theoretical interference spectrum based on a first matrix representing an optical characteristic of an uppermost layer of the sample and a second matrix representing an optical characteristic of a layer other than the uppermost layer of the sample. The optical measurement system further includes a fitting section that updates a film thickness of the uppermost layer of the sample in such a manner that the theoretical interference spectrum coincides with a spectrum of the observation light, i.e., a measured interference spectrum, thereby determining the film thickness, and an update section that updates the second matrix using the film thickness determined by the fitting section.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical measurement system for optically measuring a sample having a plurality of layers, a multilayer film manufacturing apparatus provided with the optical measurement system, and an optical measurement method. BACKGROUND

[0002] High-function devices and the like in which a plurality of layers are stacked on a substrate are being developed and utilized. In film formation of such high-function devices, there is a demand to measure the film thickness of each layer. In response to such a demand, for example, Japanese Patent Application Publication No. 2019-120607 discloses a film thickness measuring device that measures the film thickness of a first film and the film thickness of a second film with respect to a measurement target in which a plurality of first films and second films are alternately stacked on a substrate.

[0003] In addition, Japanese Patent Application Publication No. H11-160028 discloses a film thickness measuring device that can accurately measure the film thickness even in a case where the film configuration cannot be determined.

[0004] There is a demand to manufacture high-function devices corresponding to various requirements, and in response thereto, various stacked configurations need to be realized.

[0005] The film thickness measuring device disclosed in Japanese Patent Application Publication No. 2019-120607 is premised on a set of films in which a plurality of identical first films and second films are stacked, and uses a comparison result of a measured reflectance and a theoretical reflectance to determine optimization, and thus cannot be applied to high-function devices having a complex stacked configuration.

[0006] In addition, the film thickness measuring device disclosed in Japanese Patent Application Publication No. H11-160028 is premised on a comparatively simple film configuration in which the film configuration cannot be determined, and thus cannot be applied to a film configuration in which a large number of layers are stacked. SUMMARY

[0007] One of the objects of the present application is to provide an optical measurement system and an optical measurement method that can more rapidly measure the film thickness of each layer in a manufacturing process in which a plurality of layers are sequentially stacked.

[0008] According to an aspect of the present application, there is provided an optical measurement system that measures one or more layers successively formed on a substrate by a multilayer film manufacturing apparatus as a sample. The optical measurement system includes a light source for generating measurement light, a light receiving section that receives reflected light or transmitted light generated by irradiating the sample with the measurement light as observation light, and a generation section that generates a theoretical interference spectrum based on a first matrix representing an optical characteristic of an uppermost layer of the sample and a second matrix representing optical characteristics of layers other than the uppermost layer of the sample. The first matrix includes a film thickness of the uppermost layer of the sample as a parameter. The optical measurement system includes a fitting section that updates the film thickness of the uppermost layer of the sample in such a manner that the theoretical interference spectrum coincides with a spectrum of the observation light, i.e., a measured interference spectrum, thereby determining the film thickness, and an update section that updates the second matrix using the film thickness determined by the fitting section.

[0009] It can be configured that the generation section acquires a refractive index of the uppermost layer of the sample and determines the first matrix based on the acquired refractive index.

[0010] It can be that the first matrix includes an interference matrix that defines a phase change due to interference of light propagating within the uppermost layer of the sample and an interface matrix that defines transmission and reflection of light at an interface between the uppermost layer of the sample and a layer adjacent to the uppermost layer.

[0011] It can be that the optical measurement system further includes a storage section for storing the second matrix. It can be configured that the update section updates the second matrix stored in the storage section.

[0012] It can be that the optical measurement system further includes a storage section that stores the first matrix and the second matrix for each layer included in the sample.

[0013] It can be configured that the determination processing of the film thickness by the generation section and the fitting section is started when a predetermined number of layers are formed on the substrate.

[0014] It can be that the generation section further generates the theoretical interference spectrum based on one or more third matrices representing optical characteristics of one or more layers successively adjacent to the uppermost layer of the sample. It can be that the second matrix represents optical characteristics of layers for which the first matrix and the one or more third matrices are not generated. It can be that each of the one or more third matrices includes a film thickness of the corresponding layer as a parameter.

[0015] According to another aspect of the present application, there is provided a multilayer film manufacturing apparatus having the above-described optical measurement system.

[0016] According to another other aspect of the present application, there is provided an optical measurement method of measuring one or more layers successively formed on a substrate by a multilayer film manufacturing apparatus as a sample. The optical measurement method includes the steps of: irradiating measurement light from a light source to the sample, and acquiring reflected light or transmitted light, i.e., observation light, generated from the sample; and generating a theoretical interference spectrum based on a first matrix representing an optical property of an uppermost layer of the sample, and a second matrix representing optical properties of layers other than the uppermost layer of the sample. The first matrix includes a film thickness of the uppermost layer of the sample as a parameter. The optical measurement method includes the steps of: updating the film thickness of the uppermost layer of the sample in such a manner that the theoretical interference spectrum coincides with a spectrum of the observation light, i.e., a measured interference spectrum, thereby determining the film thickness; and updating the second matrix using the determined film thickness.

[0017] The above and other objects, features, aspects and advantages of the present application will become more apparent from the following detailed description of the present application when taken in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic view showing a structure example of an optical measurement system based on the present embodiment.

[0019] Figure 2 is a schematic view showing a schematic structure of a spectrometer detector used in the optical measurement system based on the present embodiment.

[0020] Figure 3 is a schematic view showing a structure example of a processing device included in the optical measurement system based on the present embodiment.

[0021] Figure 4 is a schematic view showing an example of a layer stack structure of a sample which is a measurement object of the optical measurement system based on the present embodiment.

[0022] Figure 5 is a graph showing an optical property related to a film thickness measurement of a sample which is a measurement object of the optical measurement system based on the present embodiment.

[0023] Figure 6 is a schematic view showing a state in which a film is successively formed on a sample which is a measurement object of the optical measurement system based on the present embodiment.

[0024] Figure 7 is a graph for explaining a method of measuring a film thickness of a sample shown in Figure 6 .

[0025] Figure 8 is a flowchart showing a processing procedure related to a film thickness measurement of a sample in the optical measurement system based on the present embodiment.

[0026] Figure 9is a schematic diagram showing an example of a functional configuration provided by an optical measurement system based on the present embodiment.

[0027] Figure 10 is a schematic diagram showing an example of a method of updating a synthesis matrix in an optical measurement system based on the present embodiment.

[0028] Figure 11 is a sequence diagram showing an example of an interface between a processing device and a multilayer film manufacturing device in an optical measurement system based on the present embodiment.

[0029] Figure 12 is a diagram for explaining other methods of measuring Figure 6 the film thickness of a sample shown in FIG. 6.

[0030] Explanation of Reference Numerals

[0031] 1: optical measurement system; 3: sample; 4: Y-type optical fiber; 10: light source; 20: spectrometer; 22: diffraction grating; 24: light-receiving element; 26: interface circuit; 30: substrate; 32: layer; 50: multilayer film manufacturing device; 100: processing device; 102: processor; 104: main memory; 106: input section; 108: display section; 110: storage unit; 112: operating system; 114: measurement program; 116: detection result; 118: measurement result; 120: communication interface; 122: network interface; 124: medium drive; 126: recording medium; 150: buffer; 152: theoretical interference spectrum generation module; 154: fitting module; 156: output module; 158: work data saving module; 160: selection module; 162: optical data saving section; 164: synthesis matrix updating module; 170, 170A, 170B: synthesis matrix; 172: interference matrix; 174: interface matrix. DETAILED DESCRIPTION

[0032] Embodiments of the present application are explained in detail with reference to the accompanying drawings. In addition, the same or corresponding portions in the drawings are denoted by the same reference numerals, and are not explained repeatedly.

[0033] <A. Optical Measurement System>

[0034] First, a structure example of an optical measurement system 1 based on the present embodiment is explained. The optical measurement system 1 is a film thickness measurement device of a spectrometer interference type. Hereinafter, an optical system (reflection light observation system) that irradiates light to a sample to observe the reflection light thereof is mainly explained, and of course, can be applied to an optical system (transmission light observation system) that irradiates light to a sample to observe the transmission light thereof.

[0035] In the present specification, "film thickness" means a thickness of a specific layer or a thickness of a specific film included in an arbitrary sample.

[0036] Figure 1 is a schematic view showing a configuration example of an optical measurement system 1 based on the present embodiment. The optical measurement system 1 can be configured integrally with a multilayer film manufacturing apparatus 50, or can be configured in a form to be installed to the multilayer film manufacturing apparatus 50 after the fact. In the case of being configured integrally, the multilayer film manufacturing apparatus 50 including the optical measurement system 1 can be provided.

[0037] Typically, the multilayer film manufacturing apparatus 50 is a film forming apparatus for forming a plurality of layers on a substrate in sequence. As the film to be formed, typically, a dielectric film, an oxide film, a nitride film, and the like are assumed. The configuration of the film forming apparatus is known, and thus detailed description thereof will not be made here. The optical measurement system 1 measures one or more layers formed on a substrate in sequence by the multilayer film manufacturing apparatus 50 as a sample 3. Here, the sample 3 can also include the substrate.

[0038] The optical measurement system 1 includes a light source 10 for generating measurement light for irradiating the sample 3, a spectrometer 20 as a light receiving section that receives observation light (reflected light or transmitted light) generated by the measurement light irradiating the sample 3, and a processing apparatus 100 to which the detection result of the spectrometer 20 is input.

[0039] The processing apparatus 100 calculates a measurement result (typically, a film thickness) of the sample 3 based on the detection result of the spectrometer 20. The processing apparatus 100 also exchanges necessary information with the multilayer film manufacturing apparatus 50.

[0040] The light source 10 and the spectrometer 20 are optically connected via a Y-type optical fiber 4 having an irradiation port toward the sample 3. In the optical measurement system 1, the measurement light from the light source 10 is irradiated to the sample 3, and light occurring due to light interference generated inside the sample 3 is observed, thereby measuring the film thickness or the like of the sample 3.

[0041] The light source 10 is for generating measurement light having a prescribed wavelength range. The wavelength range of the measurement light is decided in accordance with the range of the wavelength information to be measured from the sample 3 or the like. The light source 10 uses, for example, a halogen lamp, a white LED, or the like. It can also be configured that the light source 10 generates measurement light containing a component of a near-infrared region. In this case, an ASE (Amplified Spontaneous Emission) light source can be employed as the light source 10.

[0042] Figure 2 is a schematic view showing a schematic configuration of the spectrometer 20 used in the optical measurement system 1 based on the present embodiment. Referring to Figure 2 , the spectrometer 20 outputs the intensity of each wavelength of the observation light with respect to a prescribed wavelength range.

[0043] More specifically, the spectrometer 20 includes a diffraction grating 22 that diffracts light incident via the Y-type optical fiber 4, a light-receiving element 24 having a plurality of channels configured in correspondence with the diffraction grating 22, and an interface circuit 26 electrically connected to the light-receiving element 24 for outputting a detection result to the processing device 100. The light-receiving element 24 is constituted by a line sensor or a two-dimensional sensor, or the like, and is capable of outputting an intensity of each frequency component as the detection result.

[0044] Figure 3 is a schematic view showing a configuration example of the processing device 100 included in the optical measurement system 1 according to the present embodiment. Referring to Figure 3 , the processing device 100 includes a processor 102, a main memory 104, an input section 106, a display section 108, a storage unit 110, a communication interface 120, a network interface 122, and a medium drive 124.

[0045] Typically, the processor 102 is an arithmetic processing section such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or the like, and reads out one or more programs saved in the storage unit 110 to the main memory 104 to execute the program. The main memory 104 is a volatile memory such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory), and functions as a work memory for the processor 102 to execute the program.

[0046] The input section 106 includes a keyboard, a mouse, or the like, and is used to accept an operation from a user. The display section 108 is used to output an execution result of the processor 102 executing the program, or the like, to the user.

[0047] The storage unit 110 is constituted by a hard disk, a flash memory, or the like, and is used to save various programs and data. More specifically, the storage unit 110 saves an operating system 112 (OS: Operating System), a measurement program 114, a detection result 116, and a measurement result 118.

[0048] The operating system 112 provides an environment for the processor 102 to execute the program. The measurement program 114 realizes an optical measurement method according to the present embodiment, or the like, by being executed by the processor 102. The detection result 116 includes data output from the spectrometer 20. The measurement result 118 includes measurement data obtained by execution of the measurement program 114.

[0049] The communication interface 120 is used to handle data relay transmission between the apparatus 100 and the spectrometer 20. The network interface 122 is used to handle data relay transmission between the apparatus 100 and the multilayer film manufacturing apparatus 50.

[0050] The media drive 124 reads out required data from a recording medium 126 (e.g., an optical disc, etc.) that stores programs and the like executed by the processor 102, and stores the data in the storage unit 110. Further, the measurement program 114 and the like executed in the apparatus 100 can be installed via the recording medium 126 and the like, or downloaded from a server apparatus via the network interface 122 and the like.

[0051] The measurement program 114 can also be a program that executes processing by calling required modules in a prescribed arrangement in a prescribed timing from among program modules provided as part of the operating system 112. In such a case, the measurement program 114 that does not include the modules is also included in the scope of protection of the present application. The measurement program 114 can also be provided as part of other programs.

[0052] Further, all or part of the functions provided by execution of the program by the processor 102 of the apparatus 100 can also be implemented using a hardwired logic circuit (e.g., an FPGA (field-programmable gate array), an ASIC (application specific integrated circuit), etc.). In addition, an SoC (System on Chip) that integrates a DSP (Digital Signal Processor) and an ISP (Image Signal Processor) and the like in addition to a processor such as a CPU and a GPU can also be used.

[0053] <B. Film thickness measurement>

[0054] Next, film thickness measurement of the sample 3 that is a measurement target of the optical measurement system 1 and each layer included in the sample 3 will be described theoretically.

[0055] Figure 4 is a schematic view that shows an example of a layered structure of the sample 3 that is a measurement target of the optical measurement system 1 based on the present embodiment. Referring to Figure 4 , the sample 3 is obtained by sequentially forming a plurality of layers 32 on a substrate 30 such as glass. The optical measurement system 1 sequentially measures the film thickness of the layers 32 formed during the process of sequentially forming the layers 32.

[0056] Figure 5This is a graph showing the optical characteristics related to the film thickness measurement of the sample 3, which is the object of measurement in the optical measurement system 1 based on this embodiment.

[0057] Reference Figure 5 (A) defines the complex refractive index of the j-th (1≤j≤L) layer as N. j (=n j -ik j Additionally, the incident angle of the j-th layer is set to θ. j Let the thickness of the j-th layer be d. j Let the wavelength be λ. Furthermore, i is the imaginary unit.

[0058] and Figure 5 The complex refractive index N shown in (A) j Correspondingly defined Figure 5 The interference matrix M of the j-th layer, as shown in (B), j and the interface matrix I between layer j and layer j-1. j，j-1 .

[0059] Interference matrix M j It is a matrix that defines the phase change caused by the interference of light propagating within the layer of interest (layer j). It is a 2×2 matrix to define the behavior of the incident and reflected light, respectively.

[0060] Interface Matrix I j，j1 It is a matrix that defines the transmission and reflection of light at the interface between the layer of interest (layer j) and the adjacent layer (layer j-1). It is a 2×2 matrix to define the behavior of the incident and reflected light.

[0061] Here, substrate 30 is considered as layer 0. Therefore, I 1，0 This represents the interface matrix between layer 1 and substrate 30 (layer 0). Additionally, atmosphere layer A... m The interface matrix of the Lth layer, which is the topmost layer, is defined separately as I. Am，L .

[0062] For a sample 3 with a multi-layered stacked structure, a scattering matrix S can be defined as shown in equation (1) below. That is, the scattering matrix S is calculated as the interference matrix M of all layers included in the sample 3 and the interface matrix I (including the interface matrix I). Am，L The inner product of ).

[0063] S = I Am，L ·(M L ·I L，L-1 )·(M L-1 ·I L-1，L-2 ...(M1·I 1，0 (1)

[0064]

[0065]

[0066] When the elements of the scattering matrix S (2×2 matrix) are defined as shown in Equation (2), the intensity reflectivity R of the sample 3, which has a multi-layered stacked structure, can be calculated as shown in Equation (3). The parameters (mainly the film thickness of each layer) of Equation (3) are optimized in a way that makes the spectrum of the observed light (reflected light) generated by irradiating the sample 3 with the measured light (hereinafter also referred to as the "measured interference spectrum") consistent with the theoretical interference spectrum (hereinafter also referred to as the "theoretical interference spectrum") calculated using the theoretical intensity reflectivity calculated according to Equation (3). Thus, the film thickness of the multiple layers 32 included in the sample 3 can be determined.

[0067] Use the phase factor β of the corresponding j-th layer j The amplitude reflectivity r between the j-th layer and the (j-1)-th layer j，j-1 and the amplitude transmittance t between the j-th layer and the (j-1)-th layer j，i-1 To define the interference matrix M included in equation (1) j and Interface Matrix I j，j-1 .

[0068] More specifically, as shown in equation (4-1), the phase factor β can be used. j To define the interference matrix M j Furthermore, as shown in equation (4-2), the amplitude reflectivity r can be used. i，i-1 and amplitude transmittance t i，i-1 To define the interface matrix I j，j-1 .

[0069]

[0070]

[0071] Here, as shown in equation (5-1), the film thickness d of the j-th layer can be used. j To define the phase factor β j As shown in equation (5-2), the incident angle θ is used. Am To define the phase factor β j The incident angle θ of the j-th layer included j .

[0072]

[0073]

[0074] Furthermore, the amplitude reflectivity rj，j-1 and amplitude transmittance t j，j-1 Equivalent to Fresnel coefficients, the amplitude reflectivity r of p-polarized light and s-polarized light are defined as follows (6-1) to (6-4). j，j-1 and amplitude transmittance t j，j-1 .

[0075]

[0076]

[0077]

[0078]

[0079] At the incident angle θ Am nonzero (θ) Am In the case of ≠0), the intensity reflectance for s-polarized light and p-polarized light is calculated separately (intensity reflectance Rs for s-polarized light and intensity reflectance Rp for p-polarized light). Finally, as shown in Equation (7), the average intensity reflectance for each polarized light is determined as the theoretical intensity reflectance R of sample 3.

[0080]

[0081] By fitting the theoretical interference spectrum calculated using the finally determined theoretical intensity reflectivity R with the actual measured interference spectrum obtained from sample 3, the film thickness of each layer included in sample 3 can be determined.

[0082] The optical measurement system 1 based on this embodiment measures film thickness during a manufacturing process in which new layers are sequentially formed on a substrate. Therefore, essentially only the thickness of the uppermost layer is the object of measurement. In this specification, "uppermost layer" refers to the layer in the sample that is first incident with the measurement light.

[0083] Figure 6 This is a schematic diagram showing the state in which films are sequentially formed on the sample 3, which is the object of measurement in the optical measurement system 1 based on this embodiment. Assuming that for... Figure 6 As shown in (A), the sample 3 has L layers stacked together. Figure 6 The state of the newly formed L+1 layer is shown in (B).

[0084] In this case, a new atmosphere layer A is added. m With the interface matrix I of the L+1th layer as the top layer Am，L+1 Interference matrix M L+1 and interface matrix I L+1，LThese three matrices serve as components of the scattering matrix S of sample 3. The interference matrix M and interface matrix I of the other layers remain unchanged.

[0085] Therefore, in the fitting process, 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 of layers 1 to L is set as matrix P as shown in equation (8-1) below. L Furthermore, the composition matrix P can be defined as shown in equation (8-2) below. L The various elements.

[0086] Moreover, when using the composite matrix P L Then, the scattering matrix S can be defined as shown in equation (8-3) below. L+1 When the scattering matrix S is defined as shown in equation (8-4) L+1 When considering the components, the intensity reflectivity R of the sample 3 with an L+1-layer stacked structure can be calculated as shown in Equation (8-5). L+1 .

[0087] P L =(M L ·I L，L-1 )·(M L-1 ·I L-1，L-2 ...(M1·I 1，0 (8-1)

[0088]

[0089] S L+1 =I Am，L+1 ·(M L+1 ·I L+1，L )·P L …(8-3)

[0090]

[0091]

[0092] In this case, when multiple layers are formed sequentially on a substrate, the interference matrix M and interface matrix I of the already formed layers can be used directly, and only the parameters related to the newly formed layers need to be optimized.

[0093] When the above equation (8-3) is expanded using phase factor, amplitude reflectivity, and amplitude transmittance, it becomes the following equation (9).

[0094]

[0095] The optical measurement system 1 uses the recursive formula shown in Equation (9) to optimize the parameters related to the layers formed sequentially on the substrate, thereby determining the film thickness and stacking structure of the sample 3 with multiple layers.

[0096] Figure 7 It is used for determination Figure 6 The figure shown illustrates the method for determining the film thickness of sample 3. Figure 7 (A) and Figure 6 Similarly, (B) shows the state of the formation of the (L+1)th layer for sample 3, which has L layers stacked together. At this time, as... Figure 7 As shown in (B), layers 1 through L can theoretically be considered as a single layer (the synthesized single layer). The optical properties of this single layer have a synthesis matrix P. L Using the composite matrix P L To determine the thickness of the newly formed layer (L+1 layer).

[0097] In the following description, the matrix obtained by combining the interference matrix M and the interface matrix I of layer 32 from layer 1 to layer s (s≥1) will be referred to as "composite matrix P". s ". Composite matrix P s It is a 2×2 matrix, including P s_11 P s_12 P s_21 P s_22 These four elements.

[0098] As shown in equation (8-3) above, based on the matrix (I) representing the optical properties of the uppermost layer of sample 3 Am，L+1 M L+1 I L+1，L ) and a matrix (P) representing the optical properties of the layers of sample 3 excluding the topmost layer. L The scattering matrix S is determined by this. L+1 Here, the matrix representing the optical properties of the uppermost layer of sample 3 includes the interference matrix M, which defines the phase change caused by the interference of light propagating within the uppermost layer of sample 3. L+1 And the interface matrix I, which defines the transmission and reflection of light at the interface between the uppermost layer of sample 3 and the layer adjacent to it. Am，L+1 I L+1，L .

[0099] According to the scattering matrix S L+1 Generate a theoretical interference spectrum. Here, as shown in equation (9), the matrix (I) represents the optical properties of the uppermost layer of sample 3. Am，L+1 M L+1 I L+1，L (Including the film thickness d of the uppermost layer of sample 3) Las parameters (refer to the above-described formula (4-1) and formula (5-1), etc.).

[0100] <C. Measurement Process>

[0101] Next, a measurement process related to the film thickness measurement of the sample 3 by the optical measurement system 1 based on the present embodiment will be described.

[0102] Figure 8 is a flowchart showing a measurement process related to the film thickness measurement of the sample 3 in the optical measurement system 1 based on the present embodiment. Typically, the measurement process shown in Figure 8 is realized by executing the measurement program 114 by the processor 102 of the processing device 100.

[0103] Referring to Figure 8 , the processing device 100 acquires initial settings (step S2). The initial settings include the incident angle θ Am of the measurement light, the complex refractive index N0(= n0- ik0) of the substrate 30, and the complex refractive index N m (= n Am - ik Am ) of the atmosphere layer A Am . The processing device 100 initializes the synthesis matrix P s (s = 1) to the identity matrix (step S4).

[0104] The processing device 100 determines whether a measurement start instruction is received from the multilayer film manufacturing device 50 (step S6). If the measurement start instruction is not received from the multilayer film manufacturing device 50 (NO in step S6), the process of step S6 is repeated.

[0105] If the measurement start instruction is received from the multilayer film manufacturing device 50 (YES in step S6), the processing device 100 acquires the complex refractive index N s (= n s - ik s ) of the uppermost layer of the sample 3 (step S8). For example, the measurement start instruction can also include information for specifying the kind (material, etc.) of the film (the uppermost layer) that is the measurement target. In addition, the subscript s refers to the serial number of the uppermost layer of the current sample 3. The initial value of s is “1”.

[0106] The processing device 100 calculates the amplitude reflectance r Am,s and the amplitude transmittance t Am，s between the atmosphere layer and the uppermost layer, and the amplitude reflectance r s，s-1 and the amplitude transmittance t s，s-1(Step S10). Furthermore, for the layer initially formed on the substrate (i.e., s=1), the layer adjacent to the uppermost layer on the substrate side is the substrate itself.

[0107] The processing apparatus 100 acquires the spectrum generated by irradiating the sample 3, which is positioned at the measurement location, with measurement light, i.e., the measured interference spectrum (step S12). In this way, the processing is performed to irradiate the sample 3 with measurement light from the light source 10 and acquire the reflected light or transmitted light generated from the sample 3, i.e., the observation light.

[0108] Processing device 100 for the outermost film thickness d s Set initial values ​​(step S14) and calculate the corresponding phase factor β. s (Step S16). The processing device 100 uses the current synthesis matrix P s The amplitude reflectivity r calculated in step S10 Am，s r s，s-1 and amplitude transmittance t Am，s t s，s-1 and the phase factor β calculated in step S16 s To calculate the scattering matrix S s (Step S18). Furthermore, in step S18, amplitude reflectivity and amplitude transmittance are calculated for each case of p-polarized light and s-polarized light.

[0109] The processing device 100 is based on the scattering matrix S calculated in step S18 s The elements are used to calculate the intensity reflectivity R of sample 3. s (Step S20). Calculate the intensity reflectivity R. s This represents the theoretical interference spectrum of sample 3. In this way, the processing device 100 is based on a matrix (I) representing the optical properties of the uppermost layer of sample 3. Am，s M s I s，s-1 ) and a matrix (P) representing the optical properties of the layers of sample 3 excluding the topmost layer. s To generate theoretical interference spectra.

[0110] The processing device 100 calculates the error (e.g., sum of squares) between the theoretical interference spectrum of sample 3 calculated in step S20 and the measured interference spectrum of sample 3 obtained in step S12 (step S22), and determines whether the convergence condition is met based on the magnitude of the calculated error (step S24).

[0111] If the convergence condition is not met ("No" in step S24), the processing device 100 updates the thickness d of the uppermost film based on the error. sthe current value of the uppermost layer film thickness d s is determined. s

[0112] If the convergence condition is satisfied (YES in step S24), the processing device 100 outputs the current value of the uppermost layer film thickness d s as a measurement result (step S28). Then, the processing device 100 updates the value of the synthesis matrix P s based on the determined film thickness d s (step S30). In this way, the processing device 100 updates the synthesis matrix P s using the determined film thickness d Am，s to represent the optical properties of the entire layers included in the sample 3.

[0113] The processing device 100 determines whether a measurement end notification is received from the multilayer film manufacturing device 50 (step S32). If the measurement end notification is not received from the multilayer film manufacturing device 50 (NO in step S32), the processing of step S6 is repeated.

[0114] If the measurement end notification is received from the multilayer film manufacturing device 50 (YES in step S32), the processing device 100 ends the processing.

[0115] The film thickness of the layers formed sequentially on the substrate is measured by the above-described processing procedure.

[0116] <D. Functional Block Diagram>

[0117] Figure 9 is a schematic diagram that represents an example of a functional structure provided by the optical measurement system 1 according to the present embodiment. Typically, Figure 9 each function illustrated in the drawing is implemented by executing the measurement program 114 by the processor 102 of the processing device 100.

[0118] Referring to Figure 9 , the processing device 100 includes, as a functional structure, a buffer 150, a theoretical interference spectrum generation module 152, a fitting module 154, an output module 156, a working data saving module 158, a selection module 160, an optical data saving section 162, and a synthesis matrix update module 164.

[0119] The buffer 150 saves the detection result (measured interference spectrum) output from the spectrometer detector 20.

[0120] ​The theoretical interference spectrum generation module 152 calculates the scattering matrix S corresponding to the sample 3 as the measurement target and the corresponding theoretical interference spectrum based on the information held in the working data holding module 158. At this time, the theoretical interference spectrum generation module 152 acquires the complex refractive index of the uppermost layer of the sample 3, and determines the matrix representing the optical characteristics of the uppermost layer of the sample 3 based on the acquired complex refractive index (I Am，s s s，s-1 ).

[0121] The fitting module 154 calculates the error between the measured interference spectrum held in the buffer 150 and the theoretical interference spectrum calculated by the theoretical interference spectrum generation module 152, and updates the film thickness as the fitting target based on the error. 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 this time as the measurement result. Furthermore, as a method of evaluating the agreement between the measured interference spectrum and the theoretical interference spectrum, the least squares method, the optimization method, or the like can be employed.

[0122] In this way, the fitting module 154 updates the film thickness of the uppermost layer of the sample 3 in such a manner that the theoretical interference spectrum agrees with the spectrum of the observation light, that is, the measured interference spectrum, thereby determining the film thickness.

[0123] In the working data holding module 158, the initial settings (the incident angle θ Am of the measurement light, the complex refractive index N0of the substrate, the complex refractive index N m of the atmosphere layer A Am , and the like), the synthesis matrix P, the complex refractive index of the layer (the uppermost layer) as the measurement target, and the like are held.

[0124] The selection module 160 selects the corresponding optical data from among the optical data sets held in the optical data holding section 162 in response to the information from the multilayer film manufacturing apparatus 50 for determining the kind (material, etc.) of the layer (the uppermost layer) as the measurement target.

[0125] The optical data holding section 162 holds the optical data (complex refractive index, etc.) corresponding to each layer that can be formed in the multilayer film manufacturing apparatus 50.

[0126] When the film thickness as the measurement target is determined by the fitting module 154, the synthesis matrix updating module 164 updates the value of the synthesis matrix P held in the working data holding module 158 based on the determined film thickness. In this way, the synthesis matrix updating module 164 updates the synthesis matrix P (the second matrix) using the film thickness determined by the fitting module 154 to represent the optical characteristics of the entire layers included in the sample 3.

[0127] <E. Update of Synthesis Matrix>

[0128] ​​In the optical measurement system 1 according to this embodiment, when the film thickness measurement of the outermost layer is completed, the value of the synthesis matrix P is updated (or calculated in sequence). An embodiment of updating such a synthesis matrix P will be described.

[0129] Figure 10 It is a schematic diagram showing an example of a method for updating the synthesis matrix in the optical measurement system 1 according to an embodiment of the present invention.

[0130] Figure 10 (A) of shows a method of substantially only saving the latest synthesis matrix. When measuring the film thickness of any outermost layer (the (L + 1)-th layer), using the interference matrix 172 (for the (L + 1)-th layer) and the interface matrix 174 (for the interface between the (L + 1)-th layer and the L-th layer) calculated in this measurement, the synthesis matrix 170A (the inner product of the interference matrix and the interface matrix up to the L-th layer) is updated to the synthesis matrix 170B (the inner product of the interference matrix and the interface matrix up to the (L + 1)-th layer) for measuring the next new film thickness.

[0131] As Figure 10 shown in (A) of, the processing device 100 has a storage unit for saving the synthesis matrix 170. The synthesis matrix update module 164 ( Figure 9 ) is used to update the synthesis matrix 170 saved in the storage unit. By adopting the method of only saving the latest synthesis matrix 170 that is sequentially updated like this, it is possible to continuously perform film thickness measurement with a small data capacity.

[0132] Figure 10 (B) of shows an example of saving a group of the synthesis matrix 170, the interference matrix 172, and the interface matrix 174 for each measured layer. Also in this example, for the synthesis matrix 170 of a certain layer, it is calculated by multiplying the synthesis matrix 170 of the previously measured layer by the inner product of the interference matrix 172 and the interface matrix 174.

[0133] As Figure 10 shown in (B) of, the processing device 100 has a storage unit for saving the interference matrix 172, the interface matrix 174, and the synthesis matrix 170 for each layer included in the specimen 3. By adopting such a data structure, it is also possible to easily perform post-verification and the like.

[0134] <F. Interface between the processing device 100 and the multilayer film manufacturing device 50>

[0135] Next, an example of the interface between the processing device 100 and the multilayer film manufacturing device 50 will be described.

[0136] Figure 11is a sequence chart 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 application.

[0137] Referring to Figure 11 First, in the multilayer film manufacturing device 50, a substrate as an object of film formation is set (sequence SQ2). Then, the multilayer film manufacturing device 50 transmits initial settings including information on the substrate to the processing device 100 (sequence SQ4). The processing device 100 saves the initial settings from the multilayer film manufacturing device 50 and calculates parameters required for measurement.

[0138] In the multilayer film manufacturing device 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 device 50 transmits a measurement start instruction to the processing device 100 (sequence SQ8).

[0139] The processing device 100 measures the film thickness of the film as an object (the uppermost film) (sequence SQ10). The processing device 100 transmits a measurement result (film thickness) obtained by the film thickness measurement to the multilayer film manufacturing device 50 (sequence SQ12).

[0140] The multilayer film manufacturing device 50 determines whether the formed film is appropriate based on the measurement result (film thickness) from the processing device 100 (sequence SQ14). For example, it is determined whether the film thickness of the formed film is within a range decided in advance. It can be configured that, in a case where the film thickness of the formed film exceeds the range decided in advance, the workpiece as an object is discarded. Conversely, in a case where the film thickness of the formed film is smaller than the range decided in advance, the formation of the film can be started again. In this case, the multilayer film manufacturing device 50 can transmit a measurement start instruction to the processing device 100 again.

[0141] Basically, the processes of sequences SQ6 to SQ14 are repeated in accordance with the number of films formed on the substrate (1).

[0142] When the formation of a prescribed number of films on the substrate is completed (sequence SQ16), the multilayer film manufacturing device 50 transmits a measurement end notification to the processing device 100 (sequence SQ18).

[0143] Through the above processes, a series of film thickness measurement processes is completed.

[0144] Further, the measurement start instruction can include information for determining the kind (material, etc.) of the film as a measurement object (the uppermost layer). Alternatively, it can be configured that the order of films to be formed on the substrate (description file) is saved in advance and the kind of the film as a measurement object is determined in accordance with the description file.

[0145] In addition, inFigure 11 In the interface shown, the film thickness measurement is assumed to be performed after the formation of any of the films is completed, but the film thickness can also be measured in real time during the formation of the films. In this case, the synthesis matrix can be updated at the timing when the formation of the uppermost film is completed and the formation of another type of film is started.

[0146] (G. Modification)

[0147] (g1: Application from a predetermined number of layers)

[0148] In the film thickness measurement processing described above, an example is shown in which the uppermost film is taken as the measurement target, and in the fitting of the theoretical interference spectrum to the actually measured interference spectrum, only the film thickness of the uppermost film is made variable, while the film thicknesses of the other layers are fixed (reflected as fixed values in the synthesis matrix), but in the case where the number of layers formed is small, the film thicknesses of the respective layers can also be taken as the fitting targets. Further, as the fitting method, a method such as that disclosed in Japanese Patent No. 5721586 can be employed.

[0149] Although it also depends on the processing capacity of the processing device 100, for example, the film thicknesses of a plurality of layers up to about 5 to 6 layers can also be taken as the optimization targets. Also, when more layers are formed, the processing can be switched to the processing described above in which the synthesis matrix is used, and the entire layers other than the uppermost layer are treated as a single layer to measure the film thickness of the uppermost layer.

[0150] As such, it can also be configured that after a predetermined number of layers are formed on the substrate, the film thickness determination processing of the sample 3 is started using the method described above.

[0151] (g2: Taking a plurality of layers including the uppermost layer as the fitting targets)

[0152] In the film thickness measurement processing described above, the method of calculating the theoretical interference spectrum with focus on the film of the uppermost layer is explained, but a plurality of layers including the uppermost layer can also be taken as the fitting targets.

[0153] Figure 12 is a diagram for explaining the measurement Figure 6 of the film thickness of the sample shown. Figure 12 (A) of shows a state in which the L+lth layer is newly formed on the sample 3 in which L layers are laminated. For example, as shown in Figure 12 (B), the two layers (Lth layer and L-lth layer) adjacent to the L+lth layer which is the uppermost layer are each treated as an independent layer, and the layers other than them are treated as a single layer in theory (single layer after synthesis).

[0154] As a result, sample 3 can be considered as a stacked structure consisting of four layers formed on a substrate. Furthermore, by using the film thicknesses of these four layers as parameters, the theoretical interference spectrum is calculated, and the film thicknesses of each layer of sample 3 are updated in a manner that ensures consistency between the theoretical and measured interference spectra. This allows the determination of the film thickness d, including the uppermost layer. L+1 The layered structure of sample 3.

[0155] In this case, besides using the matrix (interference matrix M) representing the optical properties of the uppermost layer (the (L+1)th layer) L+1 and Interface Matrix I L+1，L ), and a matrix representing the optical properties of a single layer (composite matrix P) L-2 In addition to the above, a matrix (interference matrix M) representing the optical properties of the layer adjacent to the topmost layer (the Lth layer) is also used. L and Interface Matrix I L，L-1 ), and the matrix (interference matrix M) representing the optical properties of the further adjacent layers (the (L-1)th layer). L-1 and Interface Matrix I L-1，L-2 ).

[0156] In this way, a theoretical interference spectrum is generated based on one or more matrices (interference matrix M and interface matrix I) representing the optical properties of one or more layers sequentially adjacent to the top layer of sample 3. In this case, the synthesized matrix P represents the optical properties of layers other than those for which interference matrix M and interface matrix I were not generated (i.e., the top layer of sample 3 and one or more layers sequentially adjacent to the top layer). Moreover, the film thickness of the top layer and each of the one or more layers sequentially adjacent to the top layer becomes the fitting object.

[0157] Furthermore, as a fitting method, the method disclosed in Japanese Patent No. 5721586 can be adopted.

[0158] When determining the film thickness of each layer through fitting, the layer closest to the substrate in sample 3 is used as the fitting object. Figure 12 In the example shown, the synthesis matrix P is updated using the film thickness of the (L-1)th layer. L The value of . The updated composite matrix P L This represents the optical properties of the layers from layer 1 to layer L-1.

[0159] By adopting this method, the accuracy of film thickness measurement can be improved by fitting a specified number of layers starting from the top layer. Furthermore, for other layers, although there are many layers, they can be regarded as a single layer. Therefore, even when the number of layers increases, higher measurement accuracy can be maintained without increasing the computational load.

[0160] (g3: Update of the composition matrix)

[0161] In the above description, the processing in which the synthesis matrix is updated each time the film thickness of the uppermost layer formed is measured when the uppermost layer is formed is exemplified, but the timing and conditions for updating the synthesis matrix can be arbitrarily set. For example, the synthesis matrix can be set to be updated every other layer or every several layers.

[0162] As a specific example, it can be set that, in a case where layers composed of two different materials are alternately formed on a substrate, the synthesis matrix is updated at the timing when a set of a first layer composed of a first material and a second layer composed of a second material is formed. That is, it can be set that, at the timing when a first layer composed of a first material is formed as an uppermost layer, the synthesis matrix is not updated, and at the timing when a set of a first layer and a second layer is formed as an uppermost layer, the synthesis matrix is updated based on the film thickness of each of the first layer and the second layer.

[0163] Similarly, it can also be set that, in a case where three or more layers composed of three or more different materials are sequentially formed on a substrate as a set of layers, the synthesis matrix is updated at the timing when the formation of the set of layers is completed.

[0164] As such, the timing and conditions for updating the synthesis matrix can be set depending on the stacked structure of the sample.

[0165] Alternatively, it can also be set that the synthesis matrix is updated according to a description file arbitrarily set in advance. Such a description file, for example, includes, as fitting targets, as many layers as possible that have a large influence on the quality of the sample, and on the other hand, actively includes the optical characteristics of layers that have a relatively small influence on the quality of the sample in the synthesis matrix, whereby it is possible to reduce the amount of calculation while maintaining the measurement accuracy of the film thickness.

[0166] (g4: computing resources)

[0167] In the above description, a configuration example in which the processing device 100 of the optical measurement system 1 performs necessary processing is described, but it is not limited thereto, and for example, the processing can be shared by a plurality of processing devices, and it can also be set that the spectrometer detector 20 performs a part of the processing. Furthermore, it can also be set that all or a part of the necessary processing is performed by a computing resource (so-called cloud) on a network that is not illustrated.

[0168] [H. SUMMARY]

[0169] In the optical measurement apparatus based on the present embodiment, for a sample in which one or more layers are formed on a substrate in order, a theoretical interference spectrum is generated based on an interference matrix and an interface matrix that represent optical characteristics of the uppermost layer of the sample, and a synthesis matrix that represents optical characteristics of layers other than the uppermost layer of the sample, and the film thickness of the uppermost layer of the sample is updated in a manner that the theoretical interference spectrum coincides with a measured interference spectrum, thereby determining the film thickness. The film that is formed first is regarded as a single layer having the synthesis matrix as the optical characteristics, thereby enabling reduction of the amount of calculation of the process of determining the film thickness, and speeding up of the process.

[0170] Embodiments of the present application have been described, but it should be considered that the embodiments disclosed this time are illustrative in all respects, but not limitative. The scope of the present application is shown by the claims, and intended to include all modifications within the meaning and range of equivalents of the claims.

Claims

1. An optical measurement system that measures one or more layers successively formed on a substrate by a multilayer film manufacturing apparatus as a sample, the optical measurement system comprising: a light source for generating measurement light; a light receiving section that receives reflected light or transmitted light generated by irradiating the sample with the measurement light as observation light; and a generation section that generates a theoretical interference spectrum based on a first matrix representing optical characteristics of an uppermost layer of the sample, the first matrix including a film thickness of the uppermost layer of the sample as a parameter, and a second matrix representing optical characteristics of layers other than the uppermost layer of the sample, the optical measurement system further comprising: a fitting section that updates the film thickness of the uppermost layer of the sample in a manner that makes the theoretical interference spectrum coincide with a spectrum of the observation light, i.e., a measured interference spectrum, thereby determining the film thickness; and an update section that updates the second matrix so as to represent optical characteristics of a single layer after synthesis of a layer represented by the second matrix and the layer whose film thickness is determined, using the film thickness determined by the fitting section.

2. The optical measurement system according to claim 1, wherein the number of elements of the second matrix is maintained before and after the update.

3. The optical measurement system according to claim 1, wherein the generation section acquires a refractive index of the uppermost layer of the sample, and determines the first matrix based on the acquired refractive index.

4. The optical measurement system according to claim 1, wherein the first matrix includes an interference matrix that defines a phase change due to interference of light propagating within the uppermost layer of the sample, and an interface matrix that defines transmission and reflection of light at an interface between the uppermost layer of the sample and a layer adjacent to the uppermost layer.

5. The optical measurement system according to any one of claims 1 to 4, further comprising a storage section for storing the second matrix, wherein the update section updates the second matrix stored in the storage section.

6. The optical measurement system according to any one of claims 1 to 4, further comprising a storage section that stores the first matrix and the second matrix for each layer included in the sample.

7. The optical measurement system according to any one of claims 1 to 4, wherein the determination process of the film thickness by the generation section and the fitting section is started when a predetermined number of layers are formed on the substrate.

8. The optical measurement system according to any one of claims 1 to 4, wherein the generation section generates the theoretical interference spectrum further based on one or more third matrices representing optical characteristics of each of one or more layers adjacent to the uppermost layer of the sample in order, wherein the second matrix represents optical characteristics of a layer for which the first matrix and the one or more third matrices are not generated, and wherein each of the one or more third matrices includes a film thickness of the corresponding layer as a parameter.

9. A multilayer film manufacturing apparatus comprising the optical measurement system according to any one of claims 1 to 4. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 10. An optical measurement method of measuring one or more layers successively formed on a substrate by a multilayer film manufacturing apparatus as a sample, the optical measurement method comprising the steps of: irradiating measurement light from a light source to the sample, and acquiring reflected light or transmitted light, i.e., observation light, generated from the sample; and generating a theoretical interference spectrum based on a first matrix representing optical characteristics of the uppermost layer of the sample, the first matrix including a film thickness of the uppermost layer of the sample as a parameter, and a second matrix representing optical characteristics of layers other than the uppermost layer of the sample, the optical measurement method further comprising the steps of: updating the film thickness of the uppermost layer of the sample in such a manner that the theoretical interference spectrum coincides with a spectrum of the observation light, i.e., a measured interference spectrum, thereby determining the film thickness; and updating the second matrix so as to represent optical characteristics of a single layer after the layers represented by the second matrix and the layer whose film thickness is determined are combined, using the determined film thickness.

Images