An ellipsometer-oriented measurement consistency optimization method and device

Abstract

The application relates to a kind of ellipsometer-oriented measurement consistency optimization method and device, comprising: using standard sample to be calibrated ellipsometer measurement, the system calibration of ellipsometer is carried out, and the system parameter of ellipsometer is obtained;Mathematical analysis is carried out to the system parameter, and the parameter value of each optical device in ellipsometer measurement system is obtained;According to the deviation of the parameter value of the optical device obtained by analysis and standard value, the parameter value of each optical device is optimized by hardware debugging, so that the corresponding optical device parameter value and standard value remain consistent.By respectively carrying out system calibration and parameter extraction to multiple ellipsometers, the device of each instrument is optimized and adjusted, the system parameter value calibrated by each instrument is ensured, so that the measurement result consistency of multiple ellipsometers is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metrology for integrated circuit manufacturing, in particular to a kind of measurement consistency optimization method and device for ellipsometer. BACKGROUND

[0002] With the rapid development of integrated circuits, the node of semiconductor manufacturing is continuously reduced, and the influence of three-dimensional topographic parameters of nanostructure on the final performance of device is also more and more significant. Therefore, accurate measurement is an indispensable link for integrated circuit manufacturing.

[0003] As a kind of thickness and key size measurement equipment in integrated circuit manufacturing, ellipsometer realizes non-contact measurement by virtue of the advantage of optical measurement means, and has no damage to sample; measurement environment requirement is low, and measurement speed is fast, which is suitable for online measurement; model-based measurement method is not limited by optical resolution limit. The basic principle of ellipsometer is to project special elliptical polarized light to the surface of the structure to be measured (generally periodic structure) by polarizer, to obtain the polarization state change (including amplitude ratio and phase difference) of polarized light before and after reflection by measuring the zero-order diffraction light (scattered light) of the structure to be measured, and then to extract the key size information of the structure to be measured by solving inverse scattering problem. The optical measurement instrument based on ellipsometer has become an indispensable measurement equipment in IC manufacturing process line, and can realize key size and film thickness measurement of 22nm technology node.

[0004] In the process of semiconductor production and manufacturing, a large number of measurement equipment needs to be used to monitor process parameters, in order to ensure the process stability of manufacturing, multiple measurement equipment is required to have good measurement consistency result. The measurement equipment based on ellipsometer needs ellipsometer probe to have excellent measurement accuracy and accuracy. Not only can it adapt to different application scenarios, but also can maintain for a long time, and guarantee the measurement consistency of different measurement means or same measurement means measurement equipment becomes an important index of measurement equipment. SUMMARY

[0005] The present application provides a kind of measurement consistency optimization method and device for ellipsometer to solve the technical problems existing in the prior art.

[0006] The technical scheme for solving the above technical problems of the present application is as follows:

[0007] In the first aspect, the present application provides a kind of measurement consistency optimization method for ellipsometer, comprising:

[0008] Step 1, using standard sample to be calibrated ellipsometer to measure, the system calibration of ellipsometer is carried out, and the system parameter of ellipsometer is obtained;

[0009] Step 2, mathematically analyzing the system parameters to obtain the parameter values of each optical device in the ellipsometer measurement system;

[0010] Step 3, according to the deviation of the parameter values of the optical devices obtained by analysis from the standard values, optimizing the parameter values of each optical device through hardware debugging, so that the corresponding optical device parameter values are consistent with the standard values.

[0011] Further, the step 1 comprises:

[0012] measuring a sample with known thickness and optical constant using an ellipsometer to be calibrated to obtain a light intensity harmonic signal;

[0013] Fourier analyzing the light intensity harmonic signal to obtain Fourier coefficients of the light intensity harmonic signal;

[0014] obtaining the system parameters of the instrument by fitting the Fourier coefficients of the measured light intensity signal and the theoretical light intensity signal.

[0015] Further, in the step 1, the system calibration process satisfies the following formula:

[0016]

[0017] wherein, is the thickness of the sample, is the incident angle of the instrument, is the optical constant of the sample, are the amplitude ratio and the phase difference of the sample to be measured, respectively, are the measured light intensity of the sample to be measured and the system parameters of the ellipsometer, respectively.

[0018] Further, the step 2 comprises:

[0019] mathematically analyzing the system parameters using an ellipsometer system model of a polarization state generation unit or an analysis unit with multiple devices considering a wave plate model to obtain the parameter values of each optical device in the ellipsometer measurement system;

[0020] The ellipsometer system model of the polarization state generation unit or the analysis unit with multiple devices considering the wave plate model is as follows:

[0021]

[0022] wherein, , is the azimuth angle reading value of the polarizer, , is the azimuth angle reading value of the phase retarder, , is the equivalent phase retardation of the phase retarder, , is an equivalent optical rotation angle of the phase retarder, , is an equivalent optical axis azimuth angle of the phase retarder, , is an incident light and an exit light of the system.

[0023] Further, the hardware debugging includes structural optimization of a device installation azimuth angle and accurate debugging of an electrical control scheme.

[0024] In a second aspect, the present application provides a measurement consistency optimization device for an ellipsometer, comprising:

[0025] a system calibration module, which calibrates a system of the ellipsometer by using a standard sample to be calibrated, and obtains system parameters of the ellipsometer;

[0026] a parameter analysis module, which mathematically analyzes the system parameters to obtain parameter values of each optical device in the ellipsometer measurement system;

[0027] a hardware debugging module, which optimizes the parameter values of each optical device by hardware debugging according to deviations of the parameter values of the optical devices obtained by analysis from standard values, so that the parameter values of the corresponding optical devices are consistent with the standard values.

[0028] Further, the system calibration module comprises:

[0029] a measurement module, which measures a sample with known thickness and optical constant by using the ellipsometer to be calibrated, and obtains a light intensity harmonic signal;

[0030] an analysis module, which performs Fourier analysis on the light intensity harmonic signal to obtain Fourier coefficients of the light intensity harmonic signal;

[0031] a fitting module, which obtains system parameters of the instrument by fitting the Fourier coefficients of the measured light intensity signal and the theoretical light intensity signal.

[0032] Further, the parameter analysis module is specifically configured to mathematically analyze the system parameters by using an ellipsometer system model of a polarization state generation unit or an analysis unit with multiple devices considering a wave plate model, to obtain parameter values of each optical device in the ellipsometer measurement system;

[0033] The ellipsometer system model of the polarization state generation unit or the analysis unit with multiple devices considering the wave plate model is as follows:

[0034]

[0035] wherein, , is the azimuth angle reading of the polarizer, 、 is the azimuth reading of the phase retarder, 、 is the equivalent phase delay of the phase retarder, 、 is the equivalent optical rotation angle of the phase retarder, 、 is the equivalent optical axis azimuth of the phase retarder, 、 are the incident light and the outgoing light of the system.

[0036] In a third aspect, the present invention provides an electronic device, comprising:

[0037] Memory for storing computer software programs;

[0038] The processor is used to read and execute the computer software program, thereby implementing the measurement consistency optimization method for ellipsometers described in the first aspect of the present invention.

[0039] In a fourth aspect, the present invention provides a non-transitory computer-readable storage medium, in which a computer software program is stored for implementing the measurement consistency optimization method for an ellipsometer as described in the first aspect of the present invention.

[0040] The beneficial effects of the present invention are: by performing system calibration and parameter extraction on multiple ellipsometers respectively, the components of each instrument are optimized and adjusted, and the system parameter values ​​calibrated by each instrument are guaranteed, thereby improving the consistency of the measurement results of multiple ellipsometers. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic flow chart of a measurement consistency optimization method for an ellipsometer is provided for an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of a dual rotating ellipsometer measurement system provided by an embodiment of the present invention;

[0043] Figure 3 A schematic structural diagram of a measurement consistency optimization device for an ellipsometer is provided in accordance with an embodiment of the present invention;

[0044] Figure 4 A schematic diagram of an electronic device according to an embodiment of the present invention;

[0045] Figure 5 A schematic diagram of an embodiment of a computer-readable storage medium provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0047] In the description of the present application, the terms "first", "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly specified.

[0048] In the description of the present application, the term "for example" is used to indicate "as an example, illustration or explanation". Any embodiment described as "for example" in the present application is not necessarily interpreted as more preferred or more advantageous than other embodiments. The following description is given in order to enable any person skilled in the art to implement and use the present application. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can realize the present application without using these specific details. In other examples, well-known structures and processes will not be described in detail to avoid unnecessary details making the description of the present application obscure. Therefore, the present application is not intended to be limited to the shown embodiments, but is consistent with the broadest scope of principles and features disclosed in the present application.

[0049] As Figure 1 shown, the embodiment of the present application provides an ellipsometer-oriented measurement consistency optimization method, comprising:

[0050] Step 1, using the standard sample to be calibrated to measure the ellipsometer, system calibration is performed on the ellipsometer to obtain the system parameters of the ellipsometer.

[0051] Figure 2 The system schematic diagram of the double-rotation ellipsometer measurement system provided by the embodiment of the present application is shown, wherein the first motor 3 and the second motor 7 drive the polarizing arm end wave plate 4 and the analyzing arm end wave plate 6 to rotate synchronously at a constant speed ratio, respectively. The ellipsometer further comprises a xenon lamp light source 1, a polarizer 2, a sample detection table 5, an analyzer 8 and a spectrometer 9. The wavelength range of the ellipsometer is 240nm-900nm. The finite-order optical periodic light beam reflected by the sample to be measured is collected using the above-mentioned ellipsometer, and the finite-order light intensity harmonic signal of the sample to be measured is obtained. The Fourier coefficients of the measured light intensity signal and the theoretical light intensity signal are fitted to obtain the system parameters of the instrument.

[0052] When the ellipsometer is calibrated, the system calibration process satisfies the following formula:

[0053]

[0054] wherein, is the thickness of the sample, is the incident angle of the instrument, is the optical constant of the sample, are the amplitude ratio and the phase difference of the sample to be measured, respectively, are the measured light intensity of the sample to be measured and the system parameters of the ellipsometer, respectively.

[0055] Step 2, mathematically analyzing the system parameters to obtain the parameter values of each optical device in the ellipsometer measurement system.

[0056] In a typical ellipsometric measurement system, it is generally divided into a polarization state generation unit (PSG) and a polarization state analysis unit (PSA). Each unit includes at least one polarizing device, and when each unit contains multiple polarizing devices, the calibrated system parameters will be coupled, and the detailed parameter values of the single device cannot be obtained. Therefore, the optical model of the device is needed to mathematically analyze the system parameters, and the parameter values of each optical device are obtained through mathematical analysis.

[0057] The common polarization optical model can be characterized as follows:

[0058]

[0059]

[0060] wherein are the azimuth angles of the fast axis of the polarizer, which can be expressed as:

[0061]

[0062] wherein are the azimuth angle reading values of the polarizer, is the initial azimuth angle of the polarizer.

[0063] The common wave plate optical model can be characterized as follows:

[0064]

[0065] wherein and represent the phase delay and the azimuth angle of the fast axis, respectively, and are the eigenmatrix and the rotation Mueller matrix thereof, which can be expressed as

[0066]

[0067]

[0068] In summary, the Mueller matrix of the single waveplate is:

[0069]

[0070] The equivalent parameters of the composite waveplate are further obtained as

[0071]

[0072] wherein, and represent the phase retardation and the optical axis azimuth of the unit waveplate, respectively, is the total number of unit waveplates, , and represent the equivalent optical rotation angle, the equivalent optical axis azimuth and the equivalent phase retardation, respectively.

[0073] The Mueller matrix of the composite waveplate can be expressed as

[0074]

[0075] wherein The eigen Mueller matrix of the linear phase retarder with dichroic absorption is as follows

[0076]

[0077] Therefore, the relationship between the Mueller matrix elements of the composite waveplate and the polarization characteristic parameters of the composite waveplate can be derived as follows:

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092] wherein,

[0093]

[0094] wherein, The Mueller expression of the composite wave-plate polarization characteristic parameters can be obtained as

[0095]

[0096]

[0097]

[0098]

[0099] In the ellipsometer system with the multi-device polarization state generation or analysis unit, the system model is,

[0100]

[0101] The system model after considering the wave-plate model is,

[0102]

[0103] wherein, , is the azimuthal reading value of the polarizer, , is the azimuthal reading value of the phase retarder, , is the equivalent phase retardation of the phase retarder, , is the equivalent optical rotation angle of the phase retarder, , is the equivalent optical axis azimuthal angle of the phase retarder, , is the incident light and the outgoing light of the system.

[0104] The system parameters are mathematically analyzed by using an ellipsometer system model with a polarization state generation unit or an analysis unit having multiple devices considering a wave plate model, and parameter values of each optical device in the ellipsometer measurement system are obtained.

[0105] In step 3, according to the deviation of the parameter values of the optical devices obtained by analysis from standard values, the parameter values of each optical device are optimized by hardware debugging, so that the parameter values of the corresponding optical devices are consistent with the standard values.

[0106] The debugging method mainly includes structural optimization of a fast axis azimuth angle of a device installed polarizer and accurate debugging of an electrical control scheme.

[0107] Steps 1-3 are performed on multiple ellipsometers, so that the device installation angle values and the parameter values of each ellipsometer are consistent, the same system parameters are obtained, and the system parameters of the multiple ellipsometers are more consistent after debugging.

[0108] A series of standard samples with different thicknesses are measured by using multiple ellipsometers, and the measured thickness results before and after the system parameter adjustment consistency are compared, as shown in Table 1.

[0109] Table 1

[0110]

[0111] As shown in Figure 3 , the embodiment of the present application also provides a measurement consistency optimization device for an ellipsometer, which comprises:

[0112] A system calibration module calibrates the system of the ellipsometer by measuring a standard sample by using the ellipsometer to be calibrated, and obtains system parameters of the ellipsometer.

[0113] A parameter analysis module mathematically analyzes the system parameters, and obtains parameter values of each optical device in the ellipsometer measurement system.

[0114] A hardware debugging module optimizes the parameter values of each optical device by hardware debugging according to the deviation of the parameter values of the optical devices obtained by analysis from standard values, so that the parameter values of the corresponding optical devices are consistent with the standard values.

[0115] Further, the system calibration module comprises:

[0116] A measurement module measures a sample with known thickness and optical constant by using the ellipsometer to be calibrated, and obtains an optical intensity harmonic signal.

[0117] An analysis module is configured to perform Fourier analysis on the light intensity harmonic signal to obtain Fourier coefficients of the light intensity harmonic signal.

[0118] A fitting module is configured to obtain system parameters of the instrument by fitting the Fourier coefficients of the measured light intensity signal and the theoretical light intensity signal.

[0119] Further, the parameter analysis module is specifically configured to perform mathematical analysis on the system parameters by using an ellipsometer system model of a polarization state generation unit or an analysis unit with multiple devices considering a wave plate model to obtain parameter values of each optical device in the ellipsometer measurement system.

[0120] Referring to Figure 4 , Figure 4 An embodiment of an electronic device provided by the present application is shown in FIG. 5. As shown in FIG. 5, the electronic device 500 includes a memory 510, a processor 520, and a computer program 511 stored in the memory 510 and executable on the processor 520. When the processor 520 executes the computer program 511, the following steps are implemented. Figure 4

[0121] A standard sample is measured by using the ellipsometer to be calibrated to calibrate the system of the ellipsometer and obtain system parameters of the ellipsometer.

[0122] The system parameters are mathematically analyzed to obtain parameter values of each optical device in the ellipsometer measurement system.

[0123] According to the deviation between the parameter values of the optical devices obtained by analysis and standard values, the parameter values of each optical device are optimized by hardware debugging, so that the parameter values of the corresponding optical devices are consistent with the standard values.

[0124] Referring to Figure 5 , Figure 5 An embodiment of a computer readable storage medium provided by the present application is shown in FIG. 6. As shown in FIG. 6, the present embodiment provides a computer readable storage medium 600, which stores a computer program 611. When the computer program 611 is executed by a processor, the following steps are implemented. Figure 5

[0125] A standard sample is measured by using the ellipsometer to be calibrated to calibrate the system of the ellipsometer and obtain system parameters of the ellipsometer.

[0126] The system parameters are mathematically analyzed to obtain parameter values of each optical device in the ellipsometer measurement system.

[0127] According to the deviation between the parameter values of the optical devices obtained by analysis and standard values, the parameter values of each optical device are optimized by hardware debugging, so that the parameter values of the corresponding optical devices are consistent with the standard values.​​

[0128] It should be noted that the description of the various embodiments has been presented for purposes of clarity and that it is not necessary to describe each and every embodiment separately or enumerate all its possible variations. It will be apparent to those skilled in the art that additional embodiments can be practiced which depart from the specific details of the described embodiments.

[0129] Those skilled in the art will appreciate that embodiments of the present application can be readily used as a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0130] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 means for (an apparatus with) one or more functions specified in one or more of the flowchart illustrations and / or block diagrams.

[0131] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 means for (an apparatus with) one or more functions specified in one or more of the flowchart illustrations and / or block diagrams.

[0132] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in one or more of the flowchart illustrations and / or block diagrams. Figure 1 means for (an apparatus with) one or more functions specified in one or more of the flowchart illustrations and / or block diagrams.

[0133] While the preferred embodiments of the application have been described, additional variations and modifications can be made to these embodiments by those skilled in the art once they have the benefit of the present disclosure without departing from the spirit and scope of the application. Accordingly, it is intended that the appended claims include all such modifications and variations as fall within the scope of the present application.

[0134] It is apparent that those skilled in the art can make various changes and modifications to the application without departing from the spirit and scope of the application. It is therefore intended that the present application cover all such changes and modifications that are within its scope.

Claims

1. A measurement consistency optimization method for ellipsometer, characterized in that: include: Using the ellipsometer to be calibrated to measure the standard sample, the ellipsometer is calibrated to obtain the system parameters of the ellipsometer; Performing mathematical analysis on the system parameters to obtain parameter values ​​of each optical component in the ellipsometer measurement system; According to the deviation between the parameter value of the optical device obtained by analysis and the standard value, the parameter value of each optical device is optimized through hardware debugging to make the corresponding optical device parameter value consistent with the standard value; The mathematical analysis of the system parameters to obtain the parameter values ​​of each optical device in the ellipsometer measurement system includes: Performing mathematical analysis on the system parameters using an ellipsometer system model having a polarization state generating unit or an analyzing unit with multiple components taking into account a wave plate model, thereby obtaining parameter values ​​of each optical component in the ellipsometer measurement system; Considering the wave plate model, the ellipsometer system model with a multi-device polarization state generating unit or analyzing unit is shown in the following equation: in, 、 is the azimuth angle reading of the polarizer, 、 is the equivalent phase delay of the phase retarder, 、 is the equivalent optical rotation angle of the phase retarder, 、 is the equivalent optical axis azimuth of the phase retarder, 、 are the incident light and the outgoing light of the system.

2. The method according to claim 1, characterized in that The method of measuring a standard sample using the ellipsometer to be calibrated, performing system calibration on the ellipsometer, and obtaining system parameters of the ellipsometer includes: The ellipsometer to be calibrated is used to measure a sample with known thickness and optical constants to obtain a light intensity harmonic signal; Performing Fourier analysis on the light intensity harmonic signal to obtain Fourier coefficients of the light intensity harmonic signal; The system parameters of the instrument are obtained by fitting the Fourier coefficients of the measured light intensity signal and the theoretical light intensity signal.

3. The method according to claim 2, characterized in that When calibrating the ellipsometer, the system calibration process satisfies the following formula: in, is the thickness of the sample, is the angle of incidence of the instrument, is the optical constant of the sample, are the amplitude ratio and phase difference of the sample to be tested, are the measured light intensity of the sample to be measured and the system parameters of the ellipsometer.

4. The method according to claim 1, wherein The hardware debugging includes: structural optimization of the device installation azimuth angle and precise debugging of the electrical control scheme.

5. A measurement consistency optimization device for an ellipsometer, characterized in that: include: The system calibration module uses the ellipsometer to be calibrated to measure the standard sample, performs system calibration on the ellipsometer, and obtains the system parameters of the ellipsometer; A parameter analysis module, which performs mathematical analysis on the system parameters to obtain parameter values ​​of each optical device in the ellipsometer measurement system; The hardware debugging module optimizes the parameter value of each optical device through hardware debugging based on the deviation between the parameter value of the optical device obtained by analysis and the standard value, so that the corresponding optical device parameter value is consistent with the standard value; The parameter analysis module is specifically used to: use an ellipsometer system model with a polarization state generating unit or analysis unit having multiple components taking into account a wave plate model to perform mathematical analysis on the system parameters to obtain parameter values ​​of each optical component in the ellipsometer measurement system; Considering the wave plate model, the ellipsometer system model with a multi-device polarization state generating unit or analyzing unit is shown in the following equation: in, 、 is the azimuth angle reading of the polarizer, 、 is the equivalent phase delay of the phase retarder, 、 is the equivalent optical rotation angle of the phase retarder, 、 is the equivalent optical axis azimuth of the phase retarder, 、 are the incident light and the outgoing light of the system.

6. The device according to claim 5, characterized in that The system calibration module includes: The measurement module uses the ellipsometer to be calibrated to measure the sample with known thickness and optical constants to obtain the light intensity harmonic signal; an analysis module, performing Fourier analysis on the light intensity harmonic signal to obtain Fourier coefficients of the light intensity harmonic signal; The fitting module obtains the system parameters of the instrument by fitting the Fourier coefficients of the measured light intensity signal and the theoretical light intensity signal.

7. An electronic device, characterized in that: include: Memory for storing computer software programs; A processor is used to read and execute the computer software program, thereby implementing the measurement consistency optimization method for ellipsometers as described in any one of claims 1 to 4.

8. A non-transitory computer-readable storage medium, characterized in that The storage medium stores a computer software program for implementing the measurement consistency optimization method for ellipsometers as described in any one of claims 1 to 4.

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