Plasma processing apparatus, plasma processing method, and etching system

Abstract

The invention provides a plasma processing apparatus, a plasma processing method, and an etching processing system which can realize high-precision film thickness monitoring and end point determination without relying on a database acquisition method and executed signal processing. A plasma processing apparatus (70) that measures wafer reflected light from a wafer to be processed during etching processing and estimates the film thickness and depth of the wafer from the wafer reflected light using a waveform pattern database (122) includes a film thickness / depth amount determination unit (102) that determines the film thickness and depth of the wafer from the wafer reflected light; data processing is performed in which the correspondence between the film thickness and depth used in the waveform pattern database (122) and the light intensity matches before and after the second signal processing for the light intensity is performed.

Description

Technical Field

[0001] This invention relates to plasma processing apparatus, plasma processing method, and etching system. Background Technology

[0002] In the manufacture of semiconductor devices, various components are formed on the surface of a wafer, along with interconnecting wiring. These devices are formed by repeatedly depositing films of various materials such as conductors, semiconductors, and insulators, and removing unwanted parts. As a process for removing unwanted parts, dry etching using plasma (also known as plasma etching) is widely used. In plasma etching, a gas introduced into the processing chamber of the etching apparatus is ionized using a high-frequency power supply, exposing the wafer to the ionized gas for processing. At this time, anisotropic and isotropic etching is performed through ion sputtering based on plasma, free radical-based chemical reactions, etc., and by using these methods separately, various structural components and wiring are formed on the wafer surface.

[0003] When the processing shape and design differ from those achieved through plasma etching, various components formed may fail to perform their intended functions. Therefore, several process monitoring techniques have been proposed to monitor and stabilize the etching process. One such technique, known as film thickness / depth monitoring, measures the thickness of films deposited on a wafer, the depth of trenches and holes formed on the wafer, by measuring reflected light from the wafer during processing. This monitoring is used for endpoint determination of the etching process.

[0004] Patent Document 1 describes a method for improving processing accuracy using film thickness / depth monitoring. In this document, film thickness / depth monitoring using plasma light as a light source is used to detect when the film of the object being processed is about to be completely removed, at which point the etching process ends. Subsequently, the etching process is performed under conditions that allow for highly selective etching of the processed portion and the non-processed portion.

[0005] Patent Document 2 describes a high-precision technique for measuring film thickness / depth in film thickness / depth monitoring. In this document, an external light source is used instead of plasma light as the light source for illuminating the wafer.

[0006] Patent document 3 describes a high-precision method for estimating film thickness / depth using multiple waveform pattern databases, which represent the correspondence between reflected light from a wafer (wafer reflected light) and film thickness / depth. In this document, multiple waveform pattern databases are used, and the estimated film thickness / depth is calculated by using a weighted calculation based on the difference between the measured wafer reflected light and the multiple waveform pattern databases.

[0007] Prior art literature

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2006-119145

[0010] Patent Document 2: Japanese Patent Publication No. 2004-507070

[0011] Patent Document 3: Japanese Patent Application Publication No. 2022-058184 Summary of the Invention

[0012] -The problem the invention aims to solve-

[0013] In methods that use multiple waveform pattern databases (hereinafter referred to as databases) to calculate film thickness and depth, multiple databases need to be prepared in advance. These databases are data that establishes a correspondence between the wafer reflected light (light intensity) acquired at various moments during wafer processing and the film thickness and depth during processing. For example, in this processing step, wafer reflected light is acquired by etching the wafer, the film thickness and depth before and after etching are measured, the film thickness and depth before and after etching are linearly interpolated and assigned to the film thickness and depth at each moment during etching, thereby obtaining the database. Alternatively, if the relationship between the wafer film thickness and depth and the wafer reflected light in this processing step can be calculated, the database can be obtained through calculation.

[0014] The estimation of film thickness and depth using these databases is performed based on wafer-reflected light obtained from measuring the wafer of the target object during processing. At this time, various signal processing steps are performed on the wafer-reflected light to remove various light quantity variations, i.e., noise components, that occur during measurement. For example, to remove random variations in light quantity at each time point, the LPF (Low Pass Filter) performs differential and difference calculations between measurement times to remove light quantity and offset components. Since the film thickness and depth are calculated based on the wafer-reflected light that has undergone these signal processing steps, the same signal processing is typically performed on the database as well.

[0015] Here, in determining the endpoint of etching, the film thickness / depth needs to be estimated in real time based on the wafer's reflected light during etching. The etching endpoint is then determined based on the estimated value, thus ending the etching process. Therefore, the signal processing performed on the wafer's reflected light and the database is limited to signal processing that can be executed in real time. In the calculation of the time direction of LPF and differential values ​​in these signal processing steps, the correspondence between the time and the measured wafer reflected light sometimes changes before and after signal processing. Due to this change in correspondence, for example, in estimating film thickness and depth using multiple databases, contradictions arise between the multiple databases regarding the correspondence between film thickness / depth and wafer reflected light, reducing the accuracy of the film thickness / depth estimation.

[0016] Furthermore, changes in the correspondence between the time before and after signal processing and the measured reflected light from the wafer can sometimes reduce the accuracy of etching endpoint determination. For example, in cases where the etching speed of the wafer used to estimate film thickness and depth is fast or slow, even if the correspondence between film thickness and depth and reflected light is the same before signal processing, the correspondence will differ after signal processing. In such cases, when using the same database or multiple databases with a fixed (inconsistent) correspondence between film thickness / depth and reflected light to estimate film thickness and depth based on the reflected light after signal processing, even if the estimated film thickness and depth are the same, the actual film thickness and depth will differ. Consequently, deviations in the post-processed film thickness and depth occur in each wafer processed according to endpoint determination.

[0017] The present invention addresses the aforementioned problems by providing, for example, a plasma processing apparatus, a plasma processing method, and an etching processing system that achieve high-precision film thickness monitoring and endpoint determination without relying on a database acquisition method and signal processing.

[0018] -Methods for solving problems-

[0019] One embodiment of this disclosure includes a plasma processing apparatus comprising a data processor that performs data processing to ensure that the correspondence between film thickness, depth and light intensity used in a database is consistent before and after a second signal processing for light intensity. The plasma processing apparatus measures wafer-reflected light from a wafer to be processed during an etching process and uses a database to estimate the film thickness and depth of the wafer to be processed based on the wafer-reflected light.

[0020] In addition, a film thickness / depth correction device is provided, which uses the deviation of the correspondence between film thickness, depth and light intensity obtained in consistent data processing before and after the implementation of the second signal processing to correct the film thickness / depth estimated in real time based on the wafer reflected light during etching.

[0021] -Invention Effects-

[0022] According to a representative embodiment of this disclosure, the correspondence between film thickness, depth and light intensity in the database is fixed (unchanging) regardless of the measurement conditions of the database or the conditions of the second signal processing performed on the database, and no contradiction in the correspondence between film thickness, depth and light intensity will occur between multiple databases.

[0023] Furthermore, regardless of the difference between wafers undergoing etching processes, which does not depend on the deviation of the correspondence between film thickness / depth and light intensity caused by the first signal processing, the estimated correspondence between film thickness / depth and actual processed film thickness / depth remains constant.

[0024] Therefore, it is possible to achieve highly accurate estimation of film thickness and depth, and to determine the endpoint using the estimated film thickness and depth. Other issues, structures, and effects beyond those described above will be clarified in the following description of the embodiments. Attached Figure Description

[0025] Figure 1 This is a diagram showing an example of a plasma processing apparatus.

[0026] Figure 2 This is a block diagram of an example of a film thickness / depth measurement calculation unit.

[0027] Figure 3 This is a block diagram of an example of a film thickness / depth determination unit.

[0028] Figure 4 (a) is a table of data showing an example of the contents of a spectrum measured at one time point. Figure 4 (b) is a table data example showing the contents of the database.

[0029] Figure 5 (a) is a flowchart illustrating an example of the steps involved in creating a database. Figure 5 (b) is a sample of table data obtained during the creation of the database.

[0030] Figure 6 (a) is a flowchart illustrating an example of the correction steps for the correspondence between film thickness / depth and spectrum in the database. Figure 6 (b) is a table data example obtained during database modification.

[0031] Figure 7 This is a flowchart illustrating an example of the steps for calculating the time delay Δt used in the correction of the database using a test signal.

[0032] Figure 8 This is a flowchart illustrating an example of the steps for calculating the time delay Δt used in the correction of the database using measured signals.

[0033] Figure 9 This is a diagram illustrating the contents of multiple databases.

[0034] Figure 10 This is a diagram illustrating an example of the results of using a test signal to measure the time delay Δt.

[0035] Figure 11Figure (a) is an example of the results of film thickness estimation using the corrected databases. Figure 11 (b) is a figure showing an example of the results of film thickness estimation using the databases before the correction.

[0036] Figure 12 Figure (a) is an example of the results of film thickness estimation for multiple wafers using a modified database. Figure 12 (b) is a figure showing an example of the results of film thickness estimation for multiple wafers using the database before correction.

[0037] Figure 13 This is a diagram illustrating an example of the results of measuring the time delay Δt using a measured signal.

[0038] Figure 14 This is a diagram illustrating an example of the result of applying signal processing to a database using signal processing without time delay.

[0039] Figure 15 This is a figure illustrating an example of the results of film thickness estimation implemented using databases created through signal processing without time delay.

[0040] Figure 16 This is a block diagram of an example of a film thickness / depth correction unit.

[0041] Figure 17 This is a diagram illustrating an example of comparing the estimated film thickness error of an evaluation wafer based on whether or not the determined value of film thickness / depth is corrected.

[0042] Figure 18 This is a diagram illustrating an example of a similar time path calculated based on the similarity of the spectra of the database and the wafer being evaluated.

[0043] Figure 19 This is a diagram illustrating an example of comparing the estimated film thickness error of an evaluation wafer with and without correction of the determination value based on the film thickness / depth quantity, without implementing corrections to the correspondence between film thickness and spectrum in the database. Detailed Implementation

[0044] In the following embodiments, for convenience, they are described in multiple parts or embodiments as needed. However, unless otherwise explicitly stated, they are not unrelated to each other, and each is a variation, detail, or supplementary description of another. Furthermore, in the following embodiments, when referring to the quantity of elements (including number, value, quantity, range, etc.), the quantity is not limited to that specific number, except where it is explicitly stated or clearly limited to a specific number in principle. The quantity can be more than or less than that specific number.

[0045] Furthermore, in the following embodiments, it is self-evident that the constituent elements (including element steps, etc.) are not necessarily essential, except where specifically stated or obviously considered necessary in principle. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc., of constituent elements, etc., it is assumed that shapes substantially similar to or approximate the given shape, except where specifically stated or obviously not considered necessary in principle. The same applies to the aforementioned values ​​and ranges.

[0046] Hereinafter, a plasma processing apparatus, a plasma processing method, and an etching system, as embodiments of the present invention, will be described with reference to the accompanying drawings. Based on the description of the structure of a plasma processing apparatus for etching with a film thickness / depth estimation unit, an embodiment of the present invention will be described of a film thickness / depth estimation method (plasma processing method) in the etching process of the plasma processing apparatus.

[0047] [Example 1]

[0048] A schematic diagram of the plasma processing apparatus used in this embodiment is shown below. Figure 1 The plasma processing apparatus 70 includes a plasma processing unit 55. The plasma processing unit 55 includes a vacuum processing chamber 10. Etching gas introduced into the vacuum processing chamber 10 from the gas introduction unit is excited and decomposed by electricity or microwaves generated using a high-frequency power supply, etc., to become plasma 12. This plasma 12 is used to perform etching processing (plasma processing) on ​​a processing object 16, such as a semiconductor wafer, placed on the sample stage 14. The plasma processing apparatus 70 is sometimes referred to as an etching processing apparatus.

[0049] In addition, such as Figure 1 As shown, the plasma processing apparatus 70, in addition to the plasma processing unit 55, also includes a film thickness / depth calculation unit 30, a control unit 40, and an endpoint determination unit 44. The film thickness / depth calculation unit 30 and the endpoint determination unit 44 will be described later.

[0050] The control unit 40 performs tasks such as introducing gas into the vacuum processing chamber 10, generating and controlling the plasma 12, and applying voltage to the object being processed using a high-frequency power supply. Through these controls, timing adjustments are made between each device to achieve the desired etching process. When the plasma 12 is pulsed, the pulse control is also performed by the control unit 40. In this case, the plasma 12 is pulsed by switching the on / off states of voltage application from a high-frequency power supply used for etching gas plasmaization, microwave irradiation, etc. Alternatively, plasma pulses can be implemented by time-modulating the introduction of the etching gas.

[0051] The plasma processing unit 55 includes a mechanism for measuring the etching amount, film thickness, and depth of the workpiece 16. Light emitted from the light source unit 18 is guided into the vacuum processing chamber 10 via the optical system 50, irradiating the workpiece 16 with the irradiation light 22. The light source unit 18 uses continuous light from ultraviolet to infrared, but only the wavelength required for measuring the film thickness and depth of the workpiece 16 needs to be used; it can also be continuous light in a specific band or a specific wavelength. The reflected light 24 from the workpiece 16 is guided to the detection unit 28 via the optical system 50.

[0052] Here, the light irradiation optical port in the optical system 50 that irradiates light into the vacuum processing chamber 10 is, for example, composed of an optical fiber that guides light from the light source unit 18 and a lens that irradiates light towards the processing object 16 inside the vacuum processing chamber 10. Additionally, the light receiving optical port in the optical system 50 that receives reflected light 24 is, for example, composed of a lens that focuses the reflected light 24 and an optical fiber that guides the focused light towards the detection unit 28. The light irradiation optical port and the light receiving optical port are not limited to the above structures; if these ports are composed of a single port, they can also be composed of an optical fiber bundle consisting of two optical fibers at each end and one optical fiber at each end, and a lens.

[0053] Furthermore, when measuring the reflected light 24 at multiple locations of the object being processed 16, it is sufficient to provide multiple light-illuminating optical ports and / or multiple light-receiving optical ports. The structure of these optical ports is not limited to using optical fibers and lenses; the light-illuminating optical ports can be constructed using planar light-emitting elements, and the light-receiving optical ports can be constructed using cameras with CCD or CMOS sensors.

[0054] When estimating film thickness and depth using a specific band and multiple wavelengths, the detection unit 28 is composed of a beam splitter to split the introduced light and detect the amount of light at each wavelength. When estimating film thickness and depth using a specific wavelength, the detection unit 28 is not limited to a beam splitter; a photodetector or similar device can also be used. In this case, if the light introduced into the detection unit 28 is only the desired specific wavelength, a photodetector can be used directly. If continuous light is introduced, a mechanism that selects only a specific wavelength using a monochromator or similar device can be set up before the photodetector. The detection of this light is continuously performed at fixed intervals during etching, such as 2Hz or 10Hz. The output data of the detection unit 28 is fed into the film thickness / depth calculation unit 30 to determine (estimate) the film thickness and depth. In other words, the detection unit 28 functions as a photodetector that receives reflected light from the wafer during plasma processing.

[0055] The above describes the case where light is incident from an external light source unit 18 as a light source. However, if the light from the plasma 12 is used as the light source, the light source unit 18 may not be used. When the plasma 12 is used as the light source, the light emitted from the plasma 12 is also reflected by the object being processed 16, and the reflected light 24 is detected in the same way as when the light source unit 18 is used.

[0056] An example of the structure of the functional block for calculating film thickness / depth 30 is shown. Figure 2 The film thickness / depth calculation unit 30 includes: a digital signal processing unit 100, a film thickness / depth determination unit 102, a film thickness / depth correction unit 104, and a waveform pattern database 122. Furthermore, "film thickness / depth" refers to the film thickness of a film formed on a wafer (processing object 16), and the depth of trenches or holes formed on the wafer. Also, the "film thickness" described in the claims, like "film thickness / depth," is not limited to the film thickness of a film formed on a wafer, but includes the depth of trenches or holes formed on the wafer.

[0057] The time series data D1 of light quantity at each wavelength imported from the detection unit 28 to the film thickness / depth calculation unit 30 is processed by the digital signal processing unit 100 to remove or correct various noises and variations, and is then supplied as time series data D2 to the film thickness / depth determination unit 102.

[0058] The digital signal processing unit 100 performs a given signal processing (first signal processing) on ​​the output data (intensity of reflected light received by the photodetector) of the detection unit 28 and outputs it. For example, the digital signal processing unit 100 uses a low-pass filter (LPF) to remove random noise from the time series data of the light quantity. For example, the relationship between the time series data D1 and D2 before and after signal processing in a Butterworth type LPF is as shown in Equation 1 below.

[0059] [Mathematical Expression 1]

[0060]

[0061] Equation 1 illustrates the LPF method using data from three time points, where λ is the wavelength, t is the time, and a and b are coefficients determined by the sampling rate of the time series data and the cutoff frequency of the LPF. For example, with a sampling rate of 0.5 sec and a cutoff frequency of 0.1 Hz, {a0, a1, a2, b1, b2} = {0.0201, 0.0402, 0.0201, -1.5610, 0.6414}.

[0062] For example, when removing light intensity offset from time series data of light intensity, signal processing is used to calculate the amount of light intensity change and its differential value between time points. For example, Savitzky-Golay is used in the differential value calculation, and the relationship between the time series data D1 and D2 before and after signal processing is shown in Equation 2 below.

[0063] [Mathematical Expression 2]

[0064]

[0065] In Equation 2, the method for calculating the first-order differential value is shown using data from five time points. 'a' is a coefficient determined by the number of time points used and the order of the differential. For example, when calculating the first-order differential value using data from five time points, {a0, a1, a2, a3, a4} = {2, 1, 0, -1, -2}.

[0066] For example, when removing and correcting for the magnitude variation of light intensity synchronized across the entire wavelength from the spectroscopic measurement data (spectral data) at each moment, signal processing is applied to standardize the light intensity of each wavelength by the average value and the sum of the absolute values ​​of the light intensity across the entire wavelength. Standardization by the sum of absolute values ​​is implemented, for example, by the following Equation 3.

[0067] [Mathematical Expression 3]

[0068]

[0069] The signal processing and data operations in the digital signal processing unit 100 are not limited to those described above. They can also perform the signal processing and data operations required for determining the film thickness / depth in the film thickness / depth determination unit 102, such as data reduction, sparsity, interpolation, smoothing, statistical processing, comparison, etc.

[0070] In the film thickness / depth determination unit 102, the film thickness / depth is determined (estimated) using the supplied time series data D2 and data supplied from the waveform pattern database 122. An example of the structure of the functional block of the film thickness / depth determination unit 102 is shown below. Figure 3 That is, the film thickness / depth determination unit 102 functions as a determiner that determines the film thickness of the wafer based on the intensity of reflected light that has been processed by the signal processor, according to a database.

[0071] The film thickness / depth determination unit 102 includes: a waveform comparator 302, a film thickness / depth determination unit 304, an optimal database determination unit 306, a suitable database calculator 308, and a film thickness / depth calculation model generator 310.

[0072] For example, the determination of the film thickness / depth can be implemented by comparing the spectrum 320 (i.e., time series data D2) obtained during etching, supplied from the digital signal processing unit 100, with a database 322 supplied from the waveform pattern database 122. Here, an example of the content of the spectrum 320 is shown. Figure 4 (a). The spectrum sp(t) at each time t is obtained by establishing a data table that corresponds wavelengths w1 to wM with light quantities I1,t to IM,t.

[0073] Additionally, an example of the contents of database 322 is shown below. Figure 4 (b) One database is a data table that establishes a correspondence between film thickness / depth d1 to dN and spectrum db-sp1 to db-spN. That is, database 322 establishes a correspondence between the intensity of light at a given wavelength and the thickness of the film formed on a reference wafer that serves as the reference for determining the film thickness.

[0074] In determining the film thickness / depth using a single database 322, the spectrum 320 and the database 322 are directly supplied to the waveform comparator 302. The waveform comparator 302 compares the spectrum sp(t) at each moment with each spectrum db-sp in the database 322, and supplies the calculated error (or similarity) to the film thickness / depth determiner 304. The film thickness / depth determiner 304 determines the optimal spectrum from the spectrum db-sp in the database based on the error (or similarity), and determines the film thickness / depth associated with the determined spectrum as the film thickness / depth in that spectrum sp(t). The determined film thickness / depth is then supplied to the film thickness / depth correction unit 104. By using a single database 322 to determine the film thickness / depth, the capacity of storage devices, etc., constituting the waveform pattern database 122 can be reduced, for example.

[0075] For example, the determination of the film thickness / depth can also be implemented by comparing the spectrum 320 supplied from the digital signal processing unit 100 with multiple databases 322 supplied from the waveform pattern database 122. That is, the waveform pattern database 122 may also store multiple databases. For example, the spectrum 320 and the multiple databases 322 are directly supplied to the waveform comparator 302, the spectrum sp(t) at each time moment is compared with the total spectrum db-sp of the multiple databases 322, their error is calculated, and the calculated error is supplied to the film thickness / depth determiner 304.

[0076] The calculated error is also supplied to the optimal database determiner 306, which determines an optimal database from multiple databases based on the error of the spectrum of each database, and supplies the identification information of the determined database to the film thickness / depth amount determiner 304.

[0077] In the film thickness / depth determination unit 304, the database to be used is determined using the identification information of the supplied database. Furthermore, the optimal database spectrum is determined using the error between the supplied database and the spectrum sp(t). The film thickness / depth associated with the determined spectrum is then determined as the film thickness / depth amount in the spectrum sp(t). The determined film thickness / depth amount is supplied to the film thickness / depth correction unit 104. By using multiple databases, even if the data within the databases is noisy, increasing the number of databases can ensure a certain level of accuracy.

[0078] Here, the suitable database calculator 308 can use the error amount of the supplied multiple databases 322 and the waveform comparator 302 to perform a weighted summation of the multiple databases 322, thereby generating a composite database with an error amount lower than the supplied error amount. Furthermore, the suitable database calculator 308 has the function of appending the generated composite database to the multiple databases. When it is necessary to improve the estimation accuracy of the film thickness / depth, the estimation of the film thickness / depth can also be performed based on the composite database generated using the suitable database calculator 308.

[0079] Alternatively, for example, the determination of the film thickness / depth can also be implemented using a spectrum 320 supplied from the digital signal processing unit 100 and a learning model (linear / nonlinear regression function, machine learning, deep learning, etc.) of spectrum and film thickness / depth created using multiple databases 322 supplied from the waveform pattern database 122. For example, multiple databases 322 are supplied to the film thickness / depth calculation model generator 310, and a learning model is created in the film thickness / depth calculation model generator 310.

[0080] The learning model created based on the correspondence between spectra and membrane thickness / depth from multiple databases includes, for example, regression functions created using kernel ridge regression, support vector machines, etc.; analysis / classification models created using random forests, k-nearest neighbors, etc.; and learning models created using neural networks, etc. The learning model created by the membrane thickness / depth calculation model generator 310 and the spectrum 320 supplied from the digital signal processing unit 100 are supplied to the membrane thickness / depth quantity determiner 304. In the membrane thickness / depth quantity determiner 304, the learning model is used to determine the membrane thickness / depth quantity corresponding to the spectrum sp(t). The determined membrane thickness / depth quantity is supplied to the membrane thickness / depth quantity correction unit 104. By using the learning model to determine the membrane thickness / depth quantity, the learned data can be processed correctly and quickly.

[0081] Therefore, the film thickness / depth amount supplied to the film thickness / depth correction unit 104 is as follows: Figure 2The time-series data D3 is used. In the film thickness / depth correction unit 104, the film thickness / depth at each time point can be corrected based on the calculated time-series data D3. For example, if there are fluctuations in the calculated time-series data D3 due to noise, a linear approximation is made to the time progression of the film thickness / depth to correct the film thickness / depth at each time point. The film thickness / depth data D4, corrected by the film thickness / depth correction unit 104, is then output to the outside.

[0082] Figure 1 The plasma processing apparatus 70 uses film thickness / depth data supplied from the film thickness / depth calculation unit 30 to perform endpoint determination in the endpoint determination unit 44. In the endpoint determination unit 44, the acquired film thickness / depth data is compared with a predetermined film thickness / depth as a target, and it is determined whether the current film thickness / depth has reached the target. If the target is reached, a stop signal for the etching process is supplied to the control unit 40. The control unit 40 stops the etching process based on the etching stop signal. Through this operation, the plasma processing apparatus 70 can perform endpoint determination using film thickness / depth monitoring. That is, the endpoint determination unit 44 functions as a determiner that determines the endpoint of the process based on the film thickness determined by the determiner.

[0083] As explained above, the digital signal processing unit 100 performs a signal processing step, the film thickness / depth determination unit 102 performs a determination step, and the endpoint determination unit 44 performs a determination step. Furthermore, as described later, the film thickness / depth determination unit 102 performs a data processing step.

[0084] Here, the determination of film thickness / depth mentioned above is used Figure 2 The waveform pattern database 122 is acquired before estimating the film thickness / depth of the wafer to be processed. For example, an example of a method for acquiring the database by etching a test sample is shown below. Figure 5 (a) In this method, firstly, the film thickness / depth of the test sample before etching is measured (S11). The test sample is evaluated under non-destructive measurement conditions, and under destructive measurement conditions, a test sample equivalent to the test sample is measured.

[0085] Next, the test sample is etched, and the spectrum during etching is measured (acquired) (S12). Furthermore, the film thickness / depth of the etched test sample is measured non-destructively or destructively (S13). Using the measured spectrum and the film thickness / depth before and after etching, film thickness / depth allocation is performed on the spectrum at each moment during etching (S14), and the desired digital signal processing is performed on the spectral data, thereby creating and acquiring a database (S15). That is, the light intensity and film thickness contained in the database before correction are obtained based on the results of processing using a pre-prepared test sample (a sample wafer prepared in advance as a reference wafer). Furthermore, by generating the database using the test sample, each data point can be reliably acquired.

[0086] Reference Figure 5 (b) to explain Figure 5 (a) The method of assigning film thickness / depth to the spectrum at each time point (S14) and the signal processing of the spectral data (S15). Figure 5 In table (b), column c1 represents the moment when the spectrum was acquired during etching, column c2 represents the acquired spectrum, column c3 represents the film thickness / depth corresponding to each moment, and column c4 represents the result of signal processing (second signal processing) on ​​the spectrum. Here, the film thickness / depth in column c3 is determined, for example, by linearly interpolating the initial value d1 measured before etching and the endpoint value dN measured after etching and assigning them to each moment.

[0087] The signal processing (second signal processing) method used in determining the spectral data in column c4 can, for example, be combined with... Figure 2 The signal processing performed by the digital signal processing unit 100 on the time series data D1 is the same. That is, the first signal processing and the second signal processing can also be the same. In this case, by performing the same signal processing on the spectral data and database used in determining the film thickness / depth, their comparison can be performed correctly. For example, as long as the determination of the film thickness / depth can be performed, the signal processing can be different from that of the digital signal processing unit 100. In this way, the created database becomes Figure 5 The table data corresponding to column c3 of film thickness / depth and column c4 of spectrum in (b) (database before correction).

[0088] Here, the creation of the database is not limited to Figure 5 The method of etching the test sample (a) can also be created, for example, using simulations based on optical calculations. In this case, since the relationship between film thickness / depth and the spectrum is known, it is possible to avoid performing [the necessary steps]. Figure 5 Create the database in S11 to S14 of (a).

[0089] The database obtained by the above method can be used to correct the correspondence between film thickness / depth and spectrum as needed. For example, it can also be used in... Figure 5 In the signal processing of S15 of (a), if there is a difference in the correspondence between time and / or film thickness / depth and spectrum before and after signal processing, the correspondence after signal processing is corrected. The method for correcting the correspondence between time and / or film thickness / depth and spectrum is shown below. Figure 6 (a)

[0090] For example, calculate the time delay Δt caused by the signal processing (S21), and shift the correspondence between time and spectrum in the database by Δt (S22). Figure 6 (b) shows the corrected results for the database using the calculated time delay Δt. Figure 6 (b) column c4 and Figure 5 The c4 column of (b) is the same. Here, the time t corresponding to each spectrum c4 column in the database is shifted to t-Δt, and the corresponding time column c5 is newly calculated.

[0091] Next, use Figure 5 Calculate the correspondence between columns c1 and c3 in (b). Figure 6 The d' corresponding to each t-Δt in column (b)c5 determines column c6. Furthermore, the correspondence between column c6 of film thickness / depth and column c4 of the spectrum is determined as the corrected database. That is, the time delay caused by signal processing is calculated, and based on this time delay, the correspondence between light intensity and film thickness is corrected. Through this correction, the correspondence between film thickness / depth and spectrum in the database caused by changes in the correspondence between time and spectrum can be made consistent (fixed) before and after signal processing. In particular, it can eliminate contradictions between databases when estimating film thickness / depth using multiple databases, and can suppress the reduction in the accuracy of the estimation.

[0092] The above revisions Figure 6 The time delay Δt in S21 of (a) is calculated, for example, by... Figure 7 The method shown is implemented using test signals. In Figure 7 In this process, a sine wave of a specific frequency that can be observed based on the time delay of signal processing is prepared as the test signal I(t) (S31). Next, signal processing is performed on the test signal I(t) to obtain the signal-processed test signal I'(t) (S32). Furthermore, Δt is calculated by comparing the test signals I(t) before and after signal processing with I'(t) (S33).

[0093] For example, the time delay Δt can also be calculated by... Figure 8 The method shown uses measured signals for implementation. Here, firstly, according to... Figure 5 Step (a) creates the database, preparing to... Figure 5 In (b), column c3 (film thickness / depth) and column c2 (spectrum) are used to establish a corresponding database DB (S41).

[0094] In addition, a corresponding database DB' is prepared to be established between column c3 (film thickness / depth) and column c4 (spectrum after signal processing) (S42). Furthermore, DB is set as the database in the film thickness / depth estimation, and DB' is set as the spectrum of the estimation object for film thickness / depth estimation, and film thickness / depth estimation is performed (S43).

[0095] Using the film thickness / depth estimated by d'i and the film thickness / depth di in DB', the film thickness / depth retardation is calculated according to Δdi = (d'i - di). Figure 5 The relationship between column c1 (time) and column c3 (film thickness / depth) in (b) is used to calculate the time delay Δt based on the film thickness / depth delay Δdi (S44). The time delay Δt is calculated, for example, using the average value Δdave of the film thickness / depth delay Δdi, based on Δdave × (tN-t1) / (dN-d1).

[0096] By using the time delay Δt calculated according to these methods, the correspondence between film thickness / depth and spectrum in the database can be corrected.

[0097] The above describes the reason why Figure 5 In the case where the signal processing in S15 of (a) produces a difference in the correspondence between film thickness / depth and spectrum, but in the case where the signal processing in S15 does not produce a difference in the correspondence between film thickness / depth and spectrum, it is not necessary to rely on the above-mentioned signal processing. Figure 5 The correction of the correspondence between film thickness / depth and spectrum in the database of (a). That is, signal processing itself can also be data processing that keeps the correspondence between light intensity and film thickness unchanged.

[0098] For example, in the low-pass filter of Equation 1, after the low-pass filter calculation is performed on the data time series from time t1 to time tN in the database, the low-pass filter calculation is performed again on the data series from time tN to time t1. As a result, the time delay generated in the first calculation is canceled out by the second calculation, and the time delay of the time series data after the second calculation becomes zero.

[0099] For example, in the calculation of the differential value in Equation 2, the calculation process is changed to Equation 4 below, so that the time delay is zero.

[0100] [Mathematical Expression 4]

[0101]

[0102] In this calculation process, the data from times tn+1 and tn+2, which are ahead of time tn, are used in the calculation of the differential value at time tn. Therefore, when this calculation process is used on data acquired in real time during etching, the real-time performance of the output is reduced. On the other hand, since the database contains data that has already been acquired, this calculation process can eliminate the time delay of the data after the differential value is calculated.

[0103] The above describes a method to ensure that the correspondence between film thickness / depth and spectrum in the database remains consistent (unchanged) before and after signal processing. However, it is also possible to use a database whose correspondence between film thickness / depth and spectrum has changed due to signal processing to correct the output estimated film thickness value, thereby reducing the difference in estimated film thickness value caused by the database used.

[0104] For example, for each database, through Figure 6 In step S21 of (a), the time delay Δt is calculated using data from the database. Figure 5 The etching rate calculated from columns c1 (time) and c3 (film thickness / depth) in the data table of (b) determines the film thickness / depth change Δd corresponding to the time delay Δt. In film thickness / depth estimation using various databases, the film thickness / depth change Δd from these databases is used to correct the film thickness / depth estimation values ​​obtained at each time. Thus, the corrected film thickness / depth estimation values ​​at each time become unique, independent of the database used. Even using this method, the same effect as methods that ensure consistency between the film thickness / depth and spectrum correspondence in the database before and after signal processing can be achieved.

[0105] Signal processing that does not produce a difference in the correspondence between film thickness / depth and spectrum is not limited to the above. Any signal processing that does not change the correspondence between film thickness / depth and spectrum before and after signal processing, such as zero-phase filters, is acceptable.

[0106] The above describes a method to ensure consistency between the film thickness / depth and spectrum in the database before and after signal processing. However, in the object of film thickness / depth estimation, namely spectrum 320, it is also desirable that the correspondence between the measurement time and spectrum remains unchanged before and after signal processing. This is because, in the spectrum 320 of the object of film thickness / depth estimation, differences (time delays) may sometimes occur in the correspondence between time and spectrum due to signal processing. Depending on the amount of time delay, the correspondence between time and spectrum, that is, the correspondence between film thickness / depth and spectrum, changes.

[0107] Therefore, the film thickness / depth values ​​estimated from the spectrum will vary depending on the time delay. Here, the correspondence between the measurement time and the spectrum refers to, for example,... Figure 10 The relationship between peaks, troughs, etc., in the time series variation of light intensity and time. For spectrum 320, signal processing that does not change the correspondence between the measurement time and the spectrum can be achieved, for example, by implementing a low-pass filter twice in both ascending and descending directions of the time axis as described above, by calculating using the differential value of Equation 4, or by using a zero-phase filter. In this case, the real-time performance of the film thickness / depth estimation may sometimes be reduced, but by correctly outputting the film thickness / depth estimation value of a time earlier than the current time in etching, and by extrapolating the film thickness / depth of the current time based on the output film thickness / depth estimation value, the film thickness / depth of the current time can be estimated.

[0108] The above-mentioned database acquisition and database correction operations ( Figures 5 to 8 This is mainly performed by the film thickness / depth calculation unit 30. That is, the film thickness / depth calculation unit 30 functions as a data processor that performs signal processing (second signal processing) on ​​the intensity of light contained in the waveform pattern database 122 and performs data processing to make the correspondence between light intensity and film thickness consistent before and after signal processing.

[0109] Furthermore, the computational processing, such as database acquisition and database correction, is not limited to being performed by the plasma processing apparatus 70 (film thickness / depth measurement calculation unit 30). For example, it can also be performed by... Figure 1 The main computer 60 in the system executes. Figure 1 The figure shown with reference numeral 80 also illustrates an etching system consisting of a host computer 60 and a plasma processing device 70.

[0110] The main computer 60 is network-connected to the plasma processing unit 70 via a communication cable or wirelessly, and uses spectral data and other data supplied from the plasma processing unit 70 to create a database. The main computer 60 then supplies the created database to the plasma processing unit 70. Furthermore, the main computer 60 also has the function of generating learning models used for film thickness / depth estimation, and can also use the database supplied from the plasma processing unit 70 to generate learning models for estimating film thickness / depth, and supply the created learning models to the plasma processing unit 70. In other words, the main computer 60 functions as a data processing unit for generating the database, performing data processing that ensures the correspondence between light intensity and film thickness is consistent before and after the second signal processing during database generation.

[0111] Here, as mentioned above, Figure 2The function of the film thickness / depth correction unit 104 is described, which includes methods to reduce the variation of the determined value of film thickness / depth caused by noise, etc., but the correction of film thickness / depth is not limited to this. For example, when the correspondence between the determined value of film thickness / depth and the actual processed film thickness / depth changes due to the etching rate of the wafer during etching, the determined film thickness / depth can also be changed by a given calculation.

[0112] For example, the film thickness / depth determined by the time delay Δt caused by the signal processing is corrected. This time delay Δt is used in data processing to ensure that the correspondence between the film thickness / depth and the spectrum in the database is consistent before and after the signal processing. An example of the functional block of the film thickness / depth correction unit 104 is shown below. Figure 16 The film thickness / depth determination value 1620 supplied from the film thickness / depth determination unit 102 up to the current time is input to the etching rate detector 1602 of the film thickness / depth correction unit 104.

[0113] In the etching rate detector 1602, the etching rate is calculated using the film thickness / depth values ​​at each moment. For example, the relationship between time and film thickness / depth values ​​can be approximated by a straight line, and the etching rate can be calculated based on its slope. Alternatively, the material can be supplied to the etching rate detector 1602 via a path not shown. Figure 2 In the case of etching using the measured spectral data (i.e., time series data D2) and the spectral data from the waveform pattern database 122, the etching rate is calculated using the measured spectral data and the spectral data from the database. For example, a dynamic time-scaling method can be used to detect the time range of the spectral data from the database that is most similar to the measured spectral data, and the etching rate of the measured spectral data can be calculated using the width of the time range of the measured spectral data and the width of the detected time range of the database.

[0114] The etching rate calculated by the etching rate detector 1602 is supplied to the film thickness / depth correction unit 1604. In the film thickness / depth correction unit 1604, the determined value of the film thickness / depth is corrected using the supplied etching rate and the time delay Δt caused by the signal processing supplied via a path not shown. For example, the correction is performed by adding the product of the etching rate ER(t) and the time delay Δt to the determined value d(t) of the film thickness / depth at that moment. This is because the spectrum of past moments corresponds to each moment through signal processing, thus correcting the past film thickness / depth determined based on the spectrum to the film thickness / depth at the current time point.

[0115] The correction determination value of the film thickness / depth amount corrected by the film thickness / depth amount corrector 1604 is supplied as the film thickness / depth amount data to Figure 1The endpoint determination unit 44 performs the endpoint determination operation in the same way as described above. Furthermore, these computational processes can also be performed by the main computer 60 in the same manner as the data processing during database generation.

[0116] Next, the endpoint determination results of the film thickness / depth estimation of the present invention using the plasma processing apparatus 70 will be described below.

[0117] In this embodiment, multiple databases are obtained through actual measurements, and the correspondence between film thickness / depth and spectrum in the databases is corrected using test simulation signals. The results of using these multiple databases to estimate film thickness / depth are described.

[0118] An example of the database obtained through actual testing is shown below. Figure 9 There are five databases. During the etching process when acquiring these databases, the film thickness ranged from approximately 230 nm to approximately 200 nm; however, the etching rate varied for each database. Figure 2 The digital signal processing unit 100 performs digital signal processing by sequentially performing a combination of Equation 1 (low-pass filter), Equation 2 (first-order differential calculation), Equation 1 (low-pass filter), and Equation 3 (spectral normalization). Figure 2 The film thickness / depth determination method in the film thickness / depth determination unit 102 is set to use Figure 3 The method of determining film thickness / depth via multiple databases 322 through waveform comparator 302 and film thickness / depth quantity determiner 304.

[0119] The correction of the correspondence between film thickness and spectrum in each database is performed using the following method: The time delay Δt caused by signal processing is calculated using a test signal created through simulation. The signal processing used is the same as that performed by the digital signal processing unit 100 for film thickness estimation. A sine wave is used for the test signal, and the result comparing the time shift of the test signal before and after signal processing is displayed. Figure 10 .

[0120] Compared to before signal processing (Before_Proc), it can be seen that after signal processing (After_Proc), the time of minimum light intensity around 30-35 seconds has shifted to a later time. This shift is the time delay, and the time delay amount Δt is calculated based on this. The calculated time delay amount Δt is used to correct the correspondence between film thickness and spectrum in each database.

[0121] The results of etching a single sample and estimating the film thickness using the spectra obtained during the etching process, based on modified databases, are shown below. Figure 11(a) shows that the estimated film thickness at each moment during etching is not fixed depending on the database used. Here, for comparison, the results of film thickness estimation using the databases before correction are presented. Figure 11 (b) shows that the estimated film thickness at each moment during etching varies depending on the database used. Thus, if the uncorrected database is used, the estimated film thickness varies depending on the database, making it impossible to accurately implement film thickness estimation using multiple databases. On the other hand, it can be confirmed that by using the corrected database, the estimated film thickness is fixed regardless of the database, and film thickness estimation using multiple databases can be accurately implemented.

[0122] In the endpoint determination using film thickness estimation based on the above-mentioned modified multiple databases, since there is no deviation in the film thickness estimation value at each time, it is possible to correctly determine whether the film thickness estimation value has reached the target film thickness, thus achieving high-precision endpoint determination.

[0123] [Example 2]

[0124] In this embodiment, the film thickness / depth estimation method in Embodiment 1 describes the results of film thickness / depth estimation and endpoint determination using a learning model of spectrum and film thickness / depth created through kernel ridge regression. Other than this, as in Embodiment 1, descriptions are omitted in this embodiment. Furthermore, in Embodiments 1 to 6, it is self-evident that the creation and correction of the learning model and database can be performed by the aforementioned film thickness / depth determination unit 102 and main computer 60.

[0125] Similar to Example 1, an etching process was performed on one sample, and the film thickness was estimated using the modified databases obtained during the etching process, as described above. Figure 11 As in (a). Since the correspondence between film thickness and spectrum in each database is consistent, the estimated film thickness at each time point is fixed and independent of the database. Using such a database, by Figure 2 The film thickness / depth calculation model generator 310 creates a learning model through kernel ridge regression.

[0126] For example, by integrating the corresponding spectral and membrane thickness data from the entire database, setting the spectrum as the explanatory variable and the membrane thickness as the target variable, optimization of a nonlinear or linear regression model can be performed. In the optimization process, for instance, using the corresponding spectral and membrane thickness data from the entire database, the optimal values ​​of the parameters used in the regression model are calculated through cross-validation. Thus, the resulting regression model is a learning model that takes the spectrum as input and outputs membrane thickness.

[0127] In this embodiment, the learning model created above is used to estimate the film thickness based on the spectrum during etching and to determine the etching endpoint. Among the multiple databases used in creating the learning model, as mentioned above, there are no contradictions in the correspondence between film thickness and spectrum; therefore, the film thickness output value based on the spectrum from the created learning model is always unique. Thus, in the endpoint determination using the film thickness estimation based on this learning model, since there is no deviation in the estimated film thickness value at any given time, it is possible to correctly determine whether the estimated film thickness has reached the target film thickness, achieving high-precision endpoint determination.

[0128] In this embodiment, kernel ridge regression is used to create the learning model, but the method for creating the learning model is not limited to this. For example, regression functions created using kernel ridge regression, support vector machines, etc., can be used; analytical / classification models created using random forests, k-nearest neighbors, etc., and neural networks, etc. Even when using these methods, since there are no contradictions in the correspondence between film thickness and spectrum among the multiple corrected databases used in creating the learning model, the created learning model can output a unique film thickness for the input spectrum. Therefore, achieving high-precision film thickness estimation and endpoint determination is evident.

[0129] [Example 3]

[0130] In this embodiment, the results of film thickness / depth estimation and endpoint determination are described when the following method is used in the film thickness / depth estimation method of Example 1: using Figure 3 One database 322 in the image determines the film thickness / depth via a waveform comparator 302 and a film thickness / depth quantity determiner 304. Other than this, as in Embodiment 1, is omitted from description in this embodiment.

[0131] Database usage Figure 9 In DB1, similar to Example 1, the time delay Δt caused by signal processing is calculated to correct the correspondence between film thickness and spectrum in the database. Ten wafers were used for the film thickness estimation using this database, and all wafers were etched to achieve a film thickness of approximately 201 nm after etching. The etching conditions and formulations differed for each evaluation sample.

[0132] The results of estimating the film thickness of each evaluated wafer are shown below. Figure 12 (a) Figure 12In (a), the horizontal axis represents the wafer number being evaluated, and the vertical axis represents the estimated film thickness at the etching endpoint. The estimated film thickness is identical across all evaluated wafers, with a very small deviation, as small as 0.3 nm. Therefore, by using the film thickness estimation method of this embodiment, the estimated film thickness can be calculated with high accuracy without relying on the evaluated wafer. Here, as a comparative example, the results of film thickness estimation using the database before correction are shown. Figure 12 (b) The estimated film thickness at the etching endpoint differs among the evaluation wafers by a deviation of 3.3 nm, indicating that film thickness cannot be accurately estimated using the evaluation wafers. Thus, it can be confirmed that even when using a single database for film thickness estimation, film thickness estimation with high accuracy can be achieved independently of the evaluation wafers by correcting the correspondence between film thickness and spectrum in the database.

[0133] In the endpoint determination using the film thickness estimate based on the modified database described above, there is no deviation based on the film thickness estimate of the evaluation wafer at the etching endpoint and at any point during etching. Therefore, it is possible to accurately determine whether the film thickness estimate has reached the target film thickness, achieving high-precision endpoint determination.

[0134] [Example 4]

[0135] In this embodiment, the results of film thickness / depth estimation and endpoint determination are described when multiple databases from Example 1 are obtained using simulation. Other than this, as in Example 1, are omitted from the description in this embodiment.

[0136] By using optical simulations of the construction of the evaluation sample and information based on etch-based structural changes, the spectra in each construction are calculated, thereby creating data representing the correspondence between film thickness / depth and spectrum for each database. This is achieved by performing optical simulations across multiple databases, varying the etch rate and etch-based structural changes. In other words, the light intensity and film thickness contained in the uncorrected database are based on simulation results.

[0137] By obtaining the database in this way, because Figure 5 Steps S11 to S14 in the database acquisition step (a) are obvious and can therefore be omitted. Signal processing step S15 is then performed on the acquired database. Therefore, the number of steps for database generation is reduced, and setting conditions is also easier. Subsequently, similar to Example 1, the correspondence between film thickness / depth and spectrum is corrected based on the time delay Δt in the database for film thickness / depth estimation. Therefore, since film thickness / depth estimation is performed without contradiction in the correspondence between film thickness / depth and spectrum in multiple databases, the film thickness / depth estimation values ​​for a specific time for the same evaluation sample from each database become fixed, similar to Example 1.

[0138] Therefore, in the endpoint determination using film thickness estimates based on multiple databases obtained from the above simulations, there is no deviation based on the film thickness estimate of the evaluation wafer at the etching endpoint and at any point during etching. Thus, it is possible to accurately determine whether the film thickness estimate has reached the target film thickness, achieving high-precision endpoint determination.

[0139] [Example 5]

[0140] In this embodiment, the results of estimating film thickness / depth and determining the endpoint are described when the time delay Δt in Example 1 is calculated using measured data. Other than this, as in Example 1, are omitted from the description.

[0141] use Figure 8 To implement the steps Figure 9 Corrections to the correspondence between film thickness and spectrum from multiple databases are shown. DB1 is used as the test waveform pattern database for S41. The results of film thickness estimation using DB1 before and after signal processing according to S42 and S43 are shown. Figure 13 The membrane thickness at each time point in the signal-processed database is denoted as "Actual," while the estimated membrane thickness using the unprocessed database is denoted as "Estimated."

[0142] By estimating the film thickness using the above combination, it is evident that an error exists between the "actual" and "estimated" values. The time delay Δt in S44 is calculated by measuring the time deviation between the "actual" and "estimated" values ​​for each film thickness. In this embodiment, since an estimation error occurs in the estimated film thickness value (estimated) due to the influence of signal processing after the initial etching step, the average value of the time deviation after 20 seconds is calculated as the time delay Δt. The correction of the correspondence between film thickness and spectrum from multiple databases is implemented using the calculated time delay Δt.

[0143] The time delay Δt calculated in this embodiment is approximately the same as the time delay Δt calculated in Embodiment 1. Therefore, it can be said that the corrected multiple databases obtained in this embodiment are equivalent to those in Embodiment 1. Thus, in the endpoint determination using the multiple databases based on the time delay Δt calculated using the aforementioned measured data, there is no deviation based on the estimated film thickness value of the evaluation wafer at the etching endpoint and at each moment during etching. Therefore, it is possible to accurately determine whether the estimated film thickness has reached the target film thickness, achieving high-precision endpoint determination.

[0144] [Example 6]

[0145] In this embodiment, the results of film thickness / depth estimation and endpoint determination are described when the database of Example 1 is created using signal processing that does not produce a difference in the correspondence between film thickness / depth and spectrum. Other than this, as in Example 1, descriptions are omitted in this embodiment.

[0146] In Example 1, the signal processing performed on the database and the above-described process performed on the film thickness estimation object are... Figure 2 The signal processing in the digital signal processing unit 100 is the same as that in the digital signal processing unit, which sequentially implements a low-pass filter of Equation 1, a first-order differential calculation of Equation 2, a low-pass filter of Equation 1, and a spectral normalization of Equation 3. In this embodiment, signal processing is implemented that achieves the same function as these signal processing combinations and does not produce any difference in the correspondence between film thickness and spectrum before and after signal processing.

[0147] Specifically, the low-pass filter in Equation 1 performs signal processing once in the forward direction and once in the reverse direction along the time series of the spectra acquired from each database. The first derivative of Equation 2 is calculated using Equation 4. As for Equation 3, it performs signal processing on the spectra at each time point, and since there is no difference in the correspondence between film thickness and spectrum, it is used directly.

[0148] The results of performing the above signal processing on the light intensity data at specific wavelengths in a specific database at each time point are shown below. Figure 14 .exist Figure 14 In the figures, reference numeral a represents the result before signal processing (No signal processing), reference numeral b represents the result of signal processing without time-delay in this embodiment, and reference numeral c represents the result of signal processing with time-delay in embodiment 1.

[0149] Since the minimum light intensity before signal processing is consistent with that in this embodiment, it can be seen that no time delay is generated by the signal processing in this embodiment. Even compared with Embodiment 1 (reference numeral c) shown by reference, it is clear that there is no time delay by the signal processing in this embodiment.

[0150] Multiple databases were created using signal processing that did not produce a difference in the correspondence between film thickness and spectrum before and after signal processing. The results of film thickness estimation using the spectra obtained from the etching of a single sample from each database are shown below. Figure 15It can be seen that the estimated film thickness at each moment during etching becomes fixed regardless of the database used. Therefore, it can be confirmed that by creating a database using signal processing that does not produce a difference in the correspondence between film thickness and spectrum before and after signal processing, the estimated film thickness becomes fixed regardless of the database, and film thickness estimation using multiple databases can be accurately implemented.

[0151] In the endpoint determination using film thickness estimates based on multiple databases corrected by the method of this embodiment, since there is no deviation in the film thickness estimate at any time, it is possible to correctly determine whether the film thickness estimate has reached the target film thickness, thus achieving high-precision endpoint determination.

[0152] [Example 7]

[0153] In this embodiment, in the method for estimating the film thickness / depth in Example 1, in Figure 2 The waveform pattern database 122 uses one database, and the film thickness / depth determination unit 102 calculates the determined value of the film thickness / depth. The description also mentions that the film thickness / depth correction unit 104 performs the correction. Figure 16 The results of film thickness / depth estimation and endpoint determination are shown after correcting the determined values ​​of the film thickness / depth shown. Other than this, as in Example 1, descriptions are omitted in this example.

[0154] Database usage Figure 9 In DB2, similar to Example 1, the time delay Δt caused by signal processing is calculated to correct the correspondence between film thickness and spectrum in the database. Ten wafers were used for film thickness estimation using this database. Each wafer underwent etching to achieve a film thickness of approximately 200 nm. The etching conditions and etching rates differed for each evaluation sample.

[0155] In estimating the film thickness of each evaluated wafer, the following procedures were implemented. Figure 16 The correction of the determined value of the film thickness / depth amount shown. In the etching rate detection unit 1602, at each moment during etching, the etching rate ER(t) is calculated using the determined value of the film thickness determined at that moment and the moment before that moment. In this embodiment, the correlation between the time and the determined value of the film thickness is approximated by a straight line, and the etching rate ER(t) is calculated based on the slope of the obtained approximate straight line. Using the calculated etching rate ER(t) and the time delay amount Δt mentioned above, the determined value of the film thickness d(t) is corrected in the film thickness / depth corrector 1604. The correction is performed at each moment by using the determined value of the film thickness d(t), the etching rate ER(t), and the time delay amount Δt calculated by the following Equation 5.

[0156] [Mathematical Expression 5]

[0157]

[0158] Here, d'(t) is the corrected film thickness determination value. In the endpoint determination, the corrected film thickness determination value d'(t) is used as the film thickness estimate value and compared with the target film thickness of the endpoint determination.

[0159] The results of using these methods to estimate the film thickness of each evaluated wafer are shown in... Figure 17 . Figure 17 The horizontal axis represents the wafer number being evaluated, and the numbers in parentheses indicate the etching rate during the etching process. The vertical axis represents the estimated film thickness error at the etching endpoint, which is the difference between the estimated film thickness and the actual film thickness. Figure 17 The shaded bar charts show the results of correcting the film thickness estimate using the present invention, while the shaded bar charts show the results estimated using conventional methods without the correction. It is evident that with the correction of the film thickness estimate using the present invention, the film thickness estimate error is reduced in any given wafer, enabling high-precision film thickness estimation regardless of formulation conditions such as wafer etching rate. On the other hand, it is evident that in conventional methods without correction of the estimated film thickness, the film thickness estimate error varies depending on the wafer etching rate, making accurate film thickness estimation impossible.

[0160] Therefore, in the film thickness estimation using the correction of the determination value of the film thickness / depth amount mentioned above, the film thickness estimation value corresponds to the actual film thickness value with high precision. By using the endpoint determination of the film thickness estimation value of this method, the film thickness deviation between wafers after processing disappears, and high-precision processing is achieved.

[0161] [Example 8]

[0162] In this embodiment, the result of estimating the film thickness / depth in the case where the calculation method for the time delay Δt and the etching rate ER(t) is changed in the film thickness / depth estimation method modified using the determined value of the film thickness / depth in Example 7. Other than this, as in Example 1, descriptions are omitted in this embodiment.

[0163] In this embodiment, the database uses Figure 9 In the same manner as in Example 5, DB2, which is based on measured data, is used to calculate the time delay Δt caused by signal processing, and to correct the correspondence between film thickness and spectrum in the database. The evaluation wafer used for film thickness estimation using this database is the same as in Example 7.

[0164] In estimating the film thickness of each evaluated wafer, the following procedures were implemented. Figure 16The correction of the determined value of the film thickness / depth shown. In the etching rate detection unit 1602, the etching rate ER(t) is calculated using time-series data of the spectrum from the digital signal processing unit supplied by a path not shown, and time-series data of the spectrum from the waveform pattern database. In this embodiment, the etching rate ER(t) is calculated by using DTW (Dynamic Time Warping), one of the dynamic time scaling methods, to calculate the similar time path of the spectral similarity between the DB and the evaluation target wafer. Here, in this embodiment, the spectral similarity is numerically represented by cosine similarity, but the error of the feature quantity calculated by the L1 norm, L2 norm, etc. of Euclidean distance can also be used, or dimensionality compression techniques or machine learning can be used. An example of calculating the similar time path of the time point with 100 time data points of the evaluation target wafer is shown below. Figure 18 The horizontal and vertical axes represent the time numbers (sample data numbers) in the spectral time series data of DB and the evaluation object wafer, respectively. In this similar time path, the continuously rising straight line represents the interval where similar spectra were observed. The width of this interval in DB is calculated as ΔNdb(t), and the width in the evaluation object wafer is calculated as ΔNtest(t). The etching rate ER(t) at this time is calculated using the etching rate ERdb of DB via Equation 6 below.

[0165] [Mathematical Expression 6]

[0166]

[0167] Using the calculated etching rate ER(t) and the aforementioned time delay Δt, the film thickness determination value d(t) was corrected in the film thickness / depth corrector 1604. The correction method is the same as in Example 7.

[0168] The error between the corrected film thickness value and the actual film thickness value obtained by the above method is... Figure 17 Similarly, as described above, in the film thickness estimation using the correction of the determination value of the film thickness / depth quantity, the estimated film thickness value corresponds to the actual film thickness value with high precision. By using the endpoint determination of the film thickness estimation value of this method, the film thickness deviation between wafers after processing disappears, achieving high-precision processing.

[0169] [Example 9]

[0170] In this embodiment, the result of estimating the film thickness / depth using the film thickness / depth estimation method of Example 7 without correcting the correspondence between film thickness and spectrum in the database is described. Other than this, as in Example 1, descriptions are omitted in this embodiment.

[0171] In this embodiment, the database uses Figure 9 DB2 in the database calculates the time delay Δt caused by signal processing using the same method as in Example 7, but the correspondence between film thickness and spectrum in the database is used for film thickness / depth estimation without correction. The evaluation wafer used for film thickness estimation using this database is the same as in Example 7.

[0172] In estimating the film thickness of each evaluated wafer, the same procedure was performed as in Example 7. Figure 16 Corrections to the determined values ​​of the film thickness / depth shown. The results of calculating the estimated film thickness error at the endpoint of each evaluated wafer are presented below. Figure 19 It is known that when the film thickness determination value correction of the present invention is implemented, the average error in film thickness estimation is about 2 nm, but the deviation converges to less than 1 nm. On the other hand, when the film thickness determination value correction is not implemented, the deviation is also relatively large in addition to the average error of about 2 nm. Therefore, even without correcting the correspondence between film thickness and spectrum in the database as in this embodiment, by implementing the film thickness determination value correction of the present invention, the film thickness estimation value corresponds to the actual film thickness with high precision. By using the endpoint determination of the corrected film thickness determination value, the film thickness deviation between wafers after processing disappears, and high-precision processing is achieved.

[0173] Here, without correcting the correspondence between film thickness and spectrum in the database, a shift error occurs in the determined value of film thickness. This is because without correcting the database, the correspondence between film thickness and spectrum in the database is in a deviated state. In contrast, by correcting the determined value of film thickness, the correspondence between film thickness and spectrum of the evaluated wafer becomes non-deviated. As a result, the deviation in the correspondence between film thickness and spectrum in the database manifests as a shift in the determined value of film thickness.

[0174] [Example 10]

[0175] In this embodiment, the results of estimating the film thickness / depth using a method that corrects the determined value of the film thickness / depth in Example 7 are described, using multiple databases. Other than this, as in Example 1, are omitted from the description in this embodiment.

[0176] In this embodiment, the database uses Figure 9 The five databases shown are used to calculate the time delay Δt caused by signal processing using the same method as in Example 7, and the correspondence between film thickness and spectrum in each database is corrected. The evaluation wafer used for film thickness estimation using this database is the same as in Example 7. In this embodiment, film thickness estimation using multiple databases is performed according to the following steps. First, the film thickness is estimated using multiple databases... Figure 3The waveform comparator 302 takes into account the spectral data of the evaluation target wafer supplied from multiple pattern databases and the digital signal processing unit, and provides the waveform comparison results between each database and the spectral data of the evaluation target wafer to the optimal database determiner 306. In the optimal database determiner 306, the optimal database to be used for film thickness estimation of the evaluation target wafer is determined, and the determination result information is provided to the film thickness / depth amount determiner 304 to calculate the determined value of film thickness at each moment during etching.

[0177] The results of calculating the estimated film thickness error at the endpoint of each evaluated wafer are as follows: Figure 17 Similarly, as described above, even in film thickness estimation using multiple databases, by correcting the film thickness / depth value determined by the present invention, the estimated film thickness value corresponds to the actual film thickness value with high precision. By using the endpoint determination of the film thickness estimation value of this method, the film thickness deviation between wafers after processing disappears, achieving high-precision processing.

[0178] The invention made by the inventors has been specifically described above based on the embodiments. However, the invention is not limited to the described embodiments, and it is self-evident that various modifications can be made without departing from its spirit.

[0179] -Explanation of Figure Markers-

[0180] 10 Vacuum Processing Chamber

[0181] 12 Plasma

[0182] 14 Sample Stage

[0183] 16. Processing Objects

[0184] 18 Light Source Section

[0185] 22 illumination light

[0186] 24. Reflected light

[0187] 28. Testing Department

[0188] 30 Film thickness / depth calculation part

[0189] 40 Control Department

[0190] 44. Endpoint Determination Department

[0191] 50 Optical System

[0192] 55 Plasma Processing Unit

[0193] 60 mainframe computers

[0194] 70 Plasma Treatment Unit

[0195] 80 Etching System

[0196] 100 Digital Signal Processing Department

[0197] 102 Film Thickness / Depth Measurement Determination Unit

[0198] 104 Film thickness / depth correction section

[0199] 122 Waveform Pattern Database

[0200] D1 Time series data supplied by the testing department

[0201] D2 Time series data supplied from the digital signal processing unit

[0202] D3 Time series data supplied from the film thickness / depth measurement unit

[0203] D4 Time series data supplied from the film thickness / depth correction unit

[0204] 302 Waveform Comparator

[0205] 304 film thickness / depth measurement determiner

[0206] 306 Best Database Decider

[0207] 308 Suitable for Database Calculators

[0208] 310 Film thickness / depth calculation model generator

[0209] 320 Spectrum supplied from the digital signal processing unit

[0210] 322 Database supplied from waveform pattern database.

Claims

1. A plasma processing apparatus for processing a wafer of a processing target disposed within a processing chamber inside a vacuum container using plasma formed within the processing chamber. The plasma processing device is characterized by having: A light receiver receives reflected light from the wafer being processed during the plasma processing. The signal processor performs first signal processing on the intensity of the reflected light received by the light receiver and outputs it. The database establishes a correspondence between the intensity of light at a given wavelength and the thickness of the film formed on a reference wafer that serves as the reference for determining the film thickness. The data processor performs a second signal processing on the light intensity contained in the database, and performs data processing to make the correspondence between the light intensity and the film thickness consistent before and after the second signal processing; The determiner, based on the database, determines the film thickness of the wafer to be processed according to the intensity of the reflected light after the first signal processing performed by the signal processor; and The determiner determines the endpoint of the plasma treatment based on the film thickness of the wafer being processed, as determined by the determiner.

2. The plasma treatment apparatus according to claim 1, wherein, The data processor calculates the time delay caused by the second signal processing, and corrects the correspondence between the light intensity and the film thickness based on the time delay.

3. The plasma treatment apparatus according to claim 2, wherein, The light intensity and film thickness contained in the database before the correction were obtained based on the results of processing with plasma using a sample wafer prepared in advance as the reference wafer.

4. The plasma treatment apparatus according to claim 2, wherein, The light intensity and film thickness contained in the database before the correction were obtained based on simulation results.

5. The plasma treatment apparatus according to claim 1, wherein, The determiner compares the intensity of the light contained in the multiple databases with the intensity of the reflected light after the first signal processing, determines the database with the smaller error, and in the determined database, determines the thickness of the film corresponding to the intensity of the light with the smaller error compared to the intensity of the reflected light after the first signal processing as the thickness of the film of the wafer to be processed.

6. The plasma treatment apparatus according to claim 1, wherein, The determiner compares the intensity of the light contained in one of the databases with the intensity of the reflected light after the first signal processing, and determines the thickness of the film corresponding to the intensity of the light with the smaller error as the thickness of the film of the wafer to be processed.

7. The plasma treatment apparatus according to claim 1, wherein, The plasma processing device further includes: a generator that generates a learning model based on multiple databases. The decision-maker determines the film thickness of the wafer being processed based on the learning model.

8. A plasma processing apparatus for processing a wafer of a processing target disposed within a processing chamber inside a vacuum container using plasma formed in the processing chamber. The plasma processing device is characterized by having: A light receiver that receives reflected light from the wafer being processed at a given moment during the process; The detector compares a database containing the intensity of reflected light at a given wavelength received by the photodetector with the remaining thickness of a film to be formed on a reference wafer, and the intensity of the reflected light at the given wavelength from the reference wafer during processing of the reference wafer, to detect the remaining thickness of the film during processing of the target wafer at the given moment; and The determiner determines the endpoint of the plasma treatment based on the thickness of the film on the wafer being processed, as detected by the detector. The detector corrects the first remaining thickness of the film obtained based on the database and the comparison of the intensity of the reflected light obtained in the processing, according to the difference between the correspondence between the intensity of the reflected light and the thickness of the film before and after the signal processing of the intensity of the reflected light, thereby detecting the second remaining thickness of the film.

9. The plasma treatment apparatus according to claim 8, wherein, The detector corrects the first remaining thickness based on the calculated time delay caused by the signal processing.

10. The plasma processing apparatus according to claim 9, wherein, The process is an etching process. The detector uses the product of the etching rate of the processed wafer in the process prior to the given time and the time delay to correct the first remaining thickness.

11. The plasma treatment apparatus according to claim 8 or 9, wherein, The intensity of the reflected light, the remaining thickness of the film, and the correspondence between the intensity of the reflected light and the remaining thickness of the film contained in the database are obtained based on the results of the plasma treatment performed using the reference wafer.

12. The plasma treatment apparatus according to claim 8 or 9, wherein, The intensity of the reflected light and the thickness of the film contained in the database before the correction were obtained based on simulation results.

13. A plasma processing method, performed by a plasma processing apparatus, wherein the plasma processing apparatus processes a wafer to be processed within a processing chamber disposed inside a vacuum container using plasma formed in the processing chamber. The plasma treatment method is characterized by having: The signal processing step performs first signal processing on the intensity of reflected light from the wafer being processed, obtained during the processing using the plasma, and outputs the signal. The determination process establishes a database corresponding to the intensity of light at a given wavelength and the thickness of the film formed on a reference wafer that serves as the reference for film thickness determination, and determines the film thickness of the wafer to be processed based on the intensity of the reflected light that has undergone the first signal processing by the signal processing process. The determination process, based on the film thickness of the wafer to be processed as determined by the decision process, determines the endpoint of the plasma treatment; and The data processing step involves performing a second signal processing on the light intensity contained in the database, and executing data processing to ensure that the correspondence between the light intensity and the film thickness is consistent before and after the second signal processing.

14. An etching system, characterized in that, It has an etching process device and a data processing device. The etching processing apparatus includes: A light receiver, in plasma processing, receives reflected light from the wafer being processed; The signal processor performs first signal processing on the intensity of the reflected light received by the light receiver and outputs it. The database establishes a correspondence between the intensity of light at a given wavelength and the thickness of the film formed on a reference wafer, which is set as the reference for determining the film thickness. The determiner, based on the database, determines the film thickness of the wafer to be processed according to the intensity of the reflected light after the first signal processing performed by the signal processor; and The determiner, based on the film thickness of the wafer being processed as determined by the determiner, determines the endpoint of the etching process. The data processing device acquires the intensity of light at a given wavelength and the thickness of the film formed on the reference wafer to generate the database. When generating the database, the data processing device performs a second signal processing on the intensity of the light, and performs data processing to make the correspondence between the intensity of the light and the thickness of the film consistent before and after the second signal processing.

Images