Spectrum library construction method, optical critical dimension measurement method and optical critical dimension measurement device

Abstract

The invention provides a spectrum library construction method and an optical critical dimension measurement method and device, and relates to the technical field of optical critical dimension measurement, and the method comprises the steps: respectively obtaining first-class spectrum library data of at least three periods of a period variable structure; under the condition that the spectrums of the first-class spectrum library data of the at least three periods have linear differences, determining second-class spectrum library data corresponding to the rest periods of the period variable structure one by one according to the first-class spectrum library data; and integrating the first type of spectrum library data and the second type of spectrum library data to construct the spectrum library. According to the method and the device, the structures corresponding to the at least three periods of the period-variable structure are modeled to obtain the first type of spectrum library data, the first type of spectrum library data is fitted to obtain the second type of spectrum library data of the structures corresponding to the other periods, and the modeling frequency required in the spectrum library construction process in OCD measurement is reduced, so that the construction time of the spectrum library is shortened; and the construction efficiency of the spectrum library is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical critical dimension measurement, and in particular to a method for constructing a spectrum library, and a method and device for measuring optical critical dimensions. Background Art

[0002] After light waves are reflected and scattered by an object, their polarization state will change, thus carrying many characteristic information of the object. By studying the changes in polarization of light waves before and after passing through an object, the polarization characteristics of the object can be obtained, and then information such as the object's structural morphology can be obtained. Traditional optical key dimension measurement obtains the spectrum of the periodic structure of the measured area, models it, and obtains a theoretical spectrum library, thereby obtaining three-dimensional structural parameters.

[0003] In the current measurement method, it is necessary to construct corresponding spectral libraries for periodic structures of different periods for the matching process during measurement, which has high construction costs and takes a long time. Summary of the invention

[0004] The present invention provides a method for constructing a spectral library, a method and a device for measuring optical critical dimensions, so as to solve the defects of high cost and long time in the prior art of constructing a spectral library, and realize an efficient method for constructing a spectral library.

[0005] The present invention provides a method for constructing a spectral library, comprising: respectively acquiring first-type spectral library data of at least three periods of periodic variable structures; In the case that there are linear differences in the spectra of the at least three periods of the first type of spectrum library data, determining the second type of spectrum library data corresponding to the remaining periods of the periodic variable structure according to the first type of spectrum library data; The first category of spectral library data and the second category of spectral library data are integrated to construct a spectral library.

[0006] According to a method for constructing a spectral library provided by the present invention, the periodically variable structure is a structure in which a critical dimension and / or spacing in a semiconductor process flow changes.

[0007] According to a method for constructing a spectral library provided by the present invention, the critical dimension includes sub-critical dimensions of the periodic variable structure in several directions, and when the critical dimension changes, the sub-critical dimension in at least one direction changes; The pitch includes sub-pitch of the periodically variable structure in several directions, and when the pitch changes, the sub-pitch in at least one direction changes.

[0008] According to a method for constructing a spectral library provided by the present invention, the step of respectively acquiring first-type spectral library data of at least three periods of a periodic variable structure specifically comprises: For each period of the at least three periods, obtaining a first theoretical spectrum of each period; Acquire a first period value and a first structure parameter of each period as a first index parameter; After establishing an index between the first theoretical spectrum of each period and the first index parameter, the first type of spectrum data of each period is determined.

[0009] According to a method for constructing a spectral library provided by the present invention, the step of obtaining the first theoretical spectrum of each period specifically includes: A rigorous coupled wave analysis is performed on the periodic variable structure in each period to obtain a first theoretical spectrum of each period.

[0010] According to a method for constructing a spectral library provided by the present invention, the step of fitting and determining the second type of spectral library data corresponding to the remaining periods of the periodic variable structure according to the first type of spectral library data specifically includes: Building a model of the period-variable structure based on the first theoretical spectrum of each period of the at least three periods, and determining second theoretical spectra corresponding to the remaining periods of the period-variable structure based on the model of the period-variable structure; Analyze each of the second theoretical spectra respectively to obtain a second theoretical period value and a second theoretical structure parameter corresponding to each of the second theoretical spectra; Correcting the second theoretical period value and the second theoretical structure parameter to obtain a second period value and a second structure parameter corresponding to the second theoretical spectrum as a second index parameter; After establishing an index between the second theoretical spectrum of each period in the remaining periods of the periodic variable structure and the second index parameter, the spectrum is determined as the second type of spectrum library data.

[0011] According to a method for constructing a spectral library provided by the present invention, the step of correcting the second theoretical period value and the second theoretical structure parameter to obtain the second period value and the second structure parameter corresponding to the second theoretical spectrum as the second index parameter specifically includes: Acquire a first theoretical cycle value and a first theoretical structure parameter of each cycle in the at least three cycles; Calculating a first period difference between the first theoretical period value and the first period value, and a first structure difference between the first theoretical structure parameter and the first structure parameter; Fitting the first period difference to obtain a second period difference of each period in the remaining periods of the period-variable structure, and fitting the first structure difference to obtain a second structure difference of each period in the remaining periods of the period-variable structure; The second period value is determined according to the second theoretical period value and the second period difference value, and the second structural parameter is determined according to the second theoretical structural parameter and the second structural difference value.

[0012] The present invention also provides a method for measuring an optical critical dimension, comprising: Obtaining the outgoing Mueller spectrum of the periodic structure to be measured; Matching the output Mueller spectrum in a spectrum library constructed by any of the above-mentioned spectrum library construction methods to obtain a matching spectrum with the highest similarity to the output Mueller spectrum; The index parameters obtained by matching the spectrum index are used as measurement parameters of the periodic structure to be measured.

[0013] The present invention also provides a device for constructing a spectral library, comprising: A first acquisition module is used to respectively acquire first-type spectral library data of at least three periods of the periodic variable structure; A second acquisition module is used to determine, when there are linear differences in the spectra of the at least three periods of the first-type spectrum library data, the second-type spectrum library data corresponding to the remaining periods of the periodic variable structure according to the first-type spectrum library data; A construction module is used to integrate the first category spectral library data and the second category spectral library data to construct a spectral library.

[0014] The present invention also provides a device for measuring optical critical dimensions, comprising: A receiving module, used for obtaining an outgoing Mueller spectrum of the periodic structure to be measured; A matching module, used for matching the output Mueller spectrum in a spectrum library constructed by any of the above-mentioned spectrum library construction methods, to obtain a matching spectrum with the highest similarity to the output Mueller spectrum; The determination module is used to use the index parameters obtained by matching the spectrum index as the measurement parameters of the periodic structure to be measured.

[0015] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for constructing a spectral library as described above is implemented.

[0016] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method for constructing a spectral library as described in any one of the above is implemented.

[0017] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the method for constructing a spectral library as described above is implemented.

[0018] The method for constructing a spectral library and the method and device for measuring optical critical dimensions provided by the present invention obtain first-type spectral library data by modeling structures corresponding to at least three periods of a periodic variable structure, obtain second-type spectral library data of structures corresponding to other periods of the periodic variable structure in process requirements based on fitting of the first-type spectral data, and construct a spectral library by integrating the first-type spectral library data and the second-type spectral library data, thereby reducing the number of modeling times required for the spectral library construction process in constructing the OCD measurement, thereby reducing the construction time of the spectral library and improving the construction efficiency of the spectral library. In addition, an unexpected effect is that the critical dimension measurement of structures corresponding to all periods of the periodic variable structure can be achieved through a constructed spectral library. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the process of constructing a spectral library provided by the present invention; Figure 2 It is a schematic diagram of a periodic variable structure in the method for constructing a spectral library provided by the present invention; Figure 3 It is a schematic diagram of a structure with at least three periods of a periodic variable structure selected in the method for constructing a spectral library provided by the present invention; Figure 4 (a) is a theoretical spectrum amplitude diagram mainly used to display a periodic variable structure with constant CD and changed space in the method for constructing a spectrum library provided by the present invention; Figure 4 (b) is a theoretical spectral phase diagram mainly used to display a periodic variable structure with constant CD and changed space in the method for constructing a spectral library provided by the present invention; Figure 5 (a) is a theoretical spectrum amplitude diagram mainly used to display a periodic variable structure with unchanged space and changed CD in the method for constructing a spectrum library provided by the present invention; Figure 5 (b) is a theoretical spectral phase diagram mainly used to display a periodic variable structure with constant space and changed CD in the method for constructing a spectral library provided by the present invention; Figure 6It is a schematic diagram mainly used to display a periodic variable structure with CD and space in multiple directions in the method for constructing a spectral library provided by the present invention; Figure 7 It is a schematic diagram mainly used to display the process flow and cycle involved in the semiconductor manufacturing process in the method for constructing the spectral library provided by the present invention; Figure 8 It is a schematic flow chart of the optical critical dimension measurement method provided by the present invention; Fig. 9 It is a structural schematic diagram of a device for constructing a spectral library provided by the present invention; Fig.10 It is a schematic structural diagram of the optical critical dimension measuring device provided by the present invention; Fig.11 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Combine the following Figures 1 to 5 The method for constructing the spectral library of the present invention is introduced as follows: Figure 1 As shown, including: Step 101, respectively acquiring first-type spectral library data of at least three periods of a periodic variable structure; A variable period structure is a structure whose period (pitch) changes during the semiconductor manufacturing process.

[0023] Alternatively, for example, a structure with a fixed CD (Critical Dimension) and a variable space (the distance between two unit structures), or a structure with a variable CD and a fixed space. Figure 2 shown.

[0024] Since the constructed spectral library is used to measure the critical dimensions of the periodic structure during the production process, it is possible to pre-design multiple periodic structures that cover the process requirements of the semiconductor process for the periodic structure that needs to be measured.

[0025] For example, for a fixed CD, there are 7 different spaces in the process requirements of a semiconductor manufacturing process, that is, the period-variable structure has 7 different periods in the process requirements.

[0026] At least three periods are determined from all the periods of the periodic variable structure, and first-category spectral library data of the periodic variable structure in these three periods are acquired.

[0027] In a specific embodiment, referring to Figure 3 Corresponding to the above-mentioned variable periodic structure with 7 different periods, the maximum period (period 3), the minimum period (period 1) and an intermediate period (period 2) required by the process are selected, and the periodic structures corresponding to the selected three periods are modeled respectively to obtain the first type of spectral library data corresponding to the three periods.

[0028] It can be understood that the first type of spectral library data represents the spectral library data obtained by modeling. The first type of spectral data of each period includes the theoretical spectrum of the period and the period value and structural parameters corresponding to the period.

[0029] In other feasible implementations, if the number of cycles required by the variable-cycle structure process is large, more cycles may be selected and modeled accordingly.

[0030] Step 102, when there are linear differences in the spectra of the at least three periods of the first type of spectrum library data, determining the second type of spectrum library data corresponding to the remaining periods of the periodic variable structure according to the first type of spectrum library data; Further, it is determined whether there are linear differences in the spectra of the first type of spectral library data of at least three periods. If so, the second type of spectral library data of the remaining periods of the periodic variable structure can be determined based on the first type of spectral library data.

[0031] In a specific embodiment, Figure 4 Figures (a) and (b) are schematic diagrams of theoretical spectra obtained by modeling three different periods of the periodic variable structure. The CD of the periodic variable structure is fixed at 40nm, and the space is changed to 70nm, 80nm and 90nm respectively.

[0032] It can be seen that when the CD of the periodic variable structure is fixed and the space changes, the spectral amplitude increases by about 0.2 with every 10nm increase in space at a wavelength of 400 to 440nm; the spectral amplitude increases by about 0.05 with every 10nm increase in space at a wavelength of 600 to 900nm. The spectral phase decreases by about 0.125 with every 10nm increase in space at a wavelength of 420 to 460nm, and decreases by about 0.1 with every 10nm increase in space at a wavelength of 540 to 680nm.

[0033] Figure 5 Figures (a) and (b) are schematic diagrams of theoretical spectra obtained by modeling three different periods of the periodic variable structure. The space of the periodic variable structure is fixed at 80nm, and the CD is changed to 30nm, 40nm and 50nm respectively.

[0034] It can be seen that when the space of the periodic variable structure is fixed and the CD changes, the peak position of the spectral amplitude shifts by about 40nm with every 10nm increase in CD at a wavelength of 300 to 540nm; the spectral amplitude decreases by about 0.15 with every 10nm increase in CD at a wavelength of 660 to 900nm; the spectral phase shifts by about 40nm with every 10nm increase in CD at a wavelength of 380 to 540nm, and the phase valley shifts by about 40nm with every 10nm increase in CD at a wavelength of 540 to 640nm, and the phase value decreases by about 0.4 with every 10nm increase in CD at a wavelength of 10nm.

[0035] That is to say, when in the spectral amplitude and spectral phase diagrams of at least three periods, at at least one wavelength, there is a linear relationship between the spectral amplitude and the spectral phase as the period changes, it can be considered that there are linear differences in the spectra of the first type of spectral data of at least three periods.

[0036] For periodic variable structures, since the spectrum of periodic changes has obvious linear differences, it is believed that the theoretical spectrum of other periods of the periodic variable structure can be determined by at least three known theoretical spectra, so that the corresponding structural parameters can be obtained according to the theoretical spectrum analysis of other periods, and then the second type of spectral library data corresponding to other periods can be obtained.

[0037] It can be understood that the second type of spectral library data represents the spectral library data obtained by fitting. The second type of spectral library data includes the theoretical spectrum, period value and structure parameter value obtained by fitting each period.

[0038] Step 103: integrating the first category of spectral library data and the second category of spectral library data to construct a spectral library.

[0039] By integrating the first type of spectral library data obtained by modeling and the second type of spectral library data obtained by fitting and putting them into the same spectral library, a spectral library for OCD measurement (Optical Critical Dimension Metrology) can be constructed.

[0040] It should be noted that the spectral library constructed at this time contains the spectral library data corresponding to all periods of the periodic variable structure in the process requirements. Therefore, in the production process, a constructed spectral library can be matched with the output spectra of all periods of the periodic variable structure to obtain the measurement results of each period of the periodic variable structure.

[0041] The present invention obtains first-category spectral library data by modeling structures corresponding to at least three periods of a periodic variable structure, obtains second-category spectral library data of structures corresponding to other periods of the periodic variable structure in process requirements based on fitting of the first-category spectral data, and constructs a spectral library by integrating the first-category spectral library data and the second-category spectral library data, thereby reducing the number of modeling times required for the spectral library construction process in OCD measurement, thereby reducing the construction time of the spectral library and improving the construction efficiency of the spectral library. In addition, an unexpected effect is that the critical dimension measurement of structures corresponding to all periods of the periodic variable structure can be achieved through a constructed spectral library.

[0042] In the method for constructing a spectrum library of the present invention, the periodically variable structure is a structure in which key dimensions and / or spacings change in a semiconductor process flow.

[0043] In the case where the period-variable structure is a structure whose period varies in one direction, such as Figure 2 As shown, specifically, it is a structure in which CD remains unchanged and space changes, or CD changes and space remains unchanged in a semiconductor process flow.

[0044] In the case where the period-variable structure is a structure with periodic variations in multiple directions, such as Figure 6 As shown, there are CDs and spaces in the X-axis and Y-axis directions. It can also be a structure in which the CD and space in one direction are changed while the CD and space in other directions remain unchanged.

[0045] Among them, some typical semiconductor process flows include gate etching (Poly Etch), sidewall deposition (OSW Dep), shallow trench etching (STI Etch), metal layer copper planarization (Metal Cu CMP), and typical cycles in the process such as Figure 7 shown.

[0046] In the method for constructing a spectral library of the present invention, the critical dimension includes sub-critical dimensions of the periodic variable structure in several directions, and when the critical dimension changes, the sub-critical dimension in at least one direction changes; The pitch includes sub-pitch of the periodically variable structure in several directions, and when the pitch changes, the sub-pitch in at least one direction changes.

[0047] Specifically, Figure 6 As shown, in the case where a pattern feature includes a sub-critical dimension CD2 and a sub-spacing space2 in the X-axis direction, and a sub-critical dimension CD1 and a sub-spacing space1 in the Y-axis direction, if CD1 and / or CD2 change and space1 and space2 remain unchanged, or if space1 and / or space2 change and CD1 and CD2 remain unchanged, it can also be confirmed as a periodic variable structure.

[0048] At the same time, if CD and space in one direction change at the same time, for example, CD1 and space1 change, CD2 and space2 remain unchanged, or CD2 and space2 change, CD1 and space1 remain unchanged, it can also be confirmed as a periodic variable structure.

[0049] In the method for constructing a spectral library of the present invention, the step of respectively acquiring the first type of spectral library data of at least three periods of the periodic variable structure specifically comprises: For each period of the at least three periods, obtaining a first theoretical spectrum of each period; The first type of spectrum library data at least includes theoretical spectra for matching with the output spectrum, and structural parameters corresponding to each theoretical spectrum.

[0050] Therefore, for at least three selected periods, firstly, their first theoretical spectra are respectively obtained by conventional modeling means. It can be understood that the first theoretical spectrum represents the actual spectral data obtained by modeling, including at least spectral amplitude and spectral phase.

[0051] Acquire a first period value and a first structure parameter of each period as a first index parameter; Furthermore, a first period value and a first structure parameter corresponding to the structure of each period in the selected at least three periods are obtained as a first index parameter.

[0052] Among them, the first period value represents the structural periodic parameters corresponding to the structure of each selected period, including the CD of a pattern feature (poly) and the interval space between two pattern features; the first structural parameters represent the three-dimensional parameters of the structure of each selected period, such as line width, height and angle, which are determined according to the specific structure of the variable periodic structure.

[0053] Specifically, through physical property characterization analysis, the first period value and the first structural parameter corresponding to each periodic structure are directly obtained.

[0054] After establishing an index between the first theoretical spectrum of each period and the first index parameter, the first type of spectrum data of each period is determined.

[0055] An index is established between the first theoretical spectrum and the first index parameter of each period, so that during the OCD measurement, the first index data matching the theoretical spectrum can be found according to the index of the matched theoretical spectrum.

[0056] It can be understood that the first index data represents the data obtained according to the index query, that is, the periodicity value and structural parameters corresponding to the theoretical spectrum.

[0057] The first index parameter X is expressed as X=(P0, X1, X2, ..., X n ). In the formula, P0 represents the first period value, X n Represents the nth first structural parameter.

[0058] In the method for constructing a spectral library of the present invention, the step of obtaining the first theoretical spectrum of each period specifically includes: A rigorous coupled wave analysis is performed on the periodic variable structure in each period to obtain a first theoretical spectrum of each period.

[0059] Rigorous Coupled-Wave Analysis (RCWA) is a numerical method for calculating the propagation of light waves in periodic structures by considering the propagation and reflection of electromagnetic waves as a superposition of coupled waves propagating in the periodic structure.

[0060] Specifically, according to the structures corresponding to at least three selected periods, the geometric shape, material parameters and periodic characteristics of the structure corresponding to each period are defined. Then the structure is simulated, and RCWA decomposes the periodic structure into multiple spatial harmonic components based on the Fourier modal method, which affect each other through coupled wave equations.

[0061] Then, by solving the coupled wave equation, the propagation characteristics of electromagnetic waves in the periodic structure are analyzed, and the first theoretical spectrum of each period is obtained based on the simulation results.

[0062] In the method for constructing a spectral library of the present invention, the step of determining the second type of spectral library data corresponding to the remaining periods of the periodic variable structure according to the first type of spectral library data specifically includes: Building a model of the period-variable structure based on the first theoretical spectrum of each period of the at least three periods, and determining second theoretical spectra corresponding to the remaining periods of the period-variable structure based on the model of the period-variable structure; To determine the second type of spectral library data based on the first spectral library data of at least three periods obtained through modeling, it is first necessary to determine the second theoretical spectra corresponding to the remaining periods of the periodic variable structure.

[0063] It is understandable that although the RCWA method can obtain relatively accurate theoretical spectral data, the steps of the RCWA method are relatively cumbersome. If the theoretical spectral data of each period of the periodic variable structure is modeled by the RCWA method, it will take a long time to build the spectral library.

[0064] Therefore, the present invention obtains the second theoretical spectrum of each period in the remaining periods by fitting the first theoretical spectrum of each period in at least three periods.

[0065] Specifically, firstly, based on the first theoretical spectrum fitting of each period in at least three periods, a model of the periodic variable structure is constructed, and then based on the constructed model, a second theoretical spectrum of the periodic variable structure in each period in the remaining periods is generated.

[0066] Analyze each of the second theoretical spectra respectively to obtain a second theoretical period value and a second theoretical structure parameter corresponding to each of the second theoretical spectra; In a feasible implementation, the second period value and the second structure parameter corresponding to each period of the period-variable structure can be obtained by directly performing physical property characterization analysis on the structures corresponding to the remaining periods.

[0067] However, in order to further improve the speed of constructing the spectral library, the present invention determines the second period value and the second structural parameter by analyzing the second theoretical spectrum.

[0068] Specifically, for the second theoretical spectrum corresponding to each period in the remaining periods, since the incident spectrum can be predetermined according to the spectrum of the incident light used for OCD measurement, the second theoretical spectrum is used as the output spectrum, and the Mueller matrix is ​​constructed based on the incident spectrum and the second theoretical spectrum, as shown below: ; In the formula, S n,IN Indicates the amount of incident light loss, S n,OUT Indicates the amount of light loss at the output. n is 0, 1, 2, or 3, S 0 means total light intensity, S 1 means the sum of the horizontal and the event polarization components, S2 represents the difference between the 45° and 135° polarization components, S 3 represents the difference between right-handed and left-handed circular polarization components; M ij Represents the matrix i The Stokes parameters are j The contribution of the Stokes parameters, for example, M 21 express S 0,IN right S 1,OUT contribution.

[0069] By analyzing the matrix elements of the Mueller matrix, the theoretical parameters of the structure corresponding to the Mueller matrix can be obtained. That is, based on the second theoretical spectrum corresponding to each period in the remaining periods, the second theoretical period value and second theoretical structure parameter corresponding to each period in the remaining periods can be obtained.

[0070] Correcting the second theoretical period value and the second theoretical structure parameter to obtain a second period value and a second structure parameter corresponding to the second theoretical spectrum as a second index parameter; It should be noted that since the structural parameters obtained based on the Mueller matrix analysis are theoretical values, there is a certain difference between them and the actual values ​​obtained through physical property characterization analysis. Therefore, after the second theoretical period value and the second theoretical structural parameter corresponding to each period in the remaining periods are obtained through analysis, the above theoretical values ​​need to be corrected to obtain the second period value and the second structural parameter representing the actual value as the second index parameter finally stored in the spectral library.

[0071] In a feasible implementation, the difference between the theoretical period value data and theoretical structure value data corresponding to each period in at least three periods and the first period value and first structure parameter obtained by physical property characterization analysis can be obtained, and the second theoretical period value and the second theoretical structure parameter can be corrected based on the difference.

[0072] After establishing an index between the second theoretical spectrum of each period in the remaining periods of the periodic variable structure and the second index parameter, the spectrum is determined as the second type of spectrum library data.

[0073] After an index is established between the second theoretical spectrum corresponding to each period in the remaining periods of the periodic variable structure and the second index parameter, it is determined as a piece of second-category spectrum library data corresponding to the period.

[0074] The present invention obtains a second theoretical spectrum of the remaining periods of the periodic variable structure by fitting a first theoretical spectrum of at least three periods having a linear relationship, and obtains a second period value and a second structure parameter as a second index parameter based on the second theoretical period value and the second theoretical structure parameter obtained by analyzing the second theoretical spectrum. That is, based on the modeling data of at least three periods, the spectral library data of the remaining periods of the periodic variable structure are fitted, thereby effectively improving the construction speed of the spectral library for OCD measurement.

[0075] In the method for constructing a spectral library of the present invention, the step of correcting the second theoretical periodicity value and the second theoretical structure parameter to obtain the second periodicity value and the second structure parameter corresponding to the second theoretical spectrum as the second index parameter specifically includes: Acquire a first theoretical cycle value and a first theoretical structure parameter of each cycle in the at least three cycles; In order to correct the second theoretical period value and the second theoretical structural parameter more accurately, the present invention corrects the second theoretical period value and the second theoretical structural parameter based on the difference between the first period value and the first structural parameter and their corresponding theoretical values.

[0076] Therefore, in order to obtain the above difference, it is first necessary to determine the theoretical value corresponding to each first period value and first structural parameter.

[0077] Optionally, for each period of the structure in the selected at least three periods, the incident spectrum is recorded respectively. S in1 , S in2 ,……, S inn , where n represents the number of selected periods. After the incident light acts on the structure of the corresponding period, the output Mueller spectrum of each selected period structure is obtained by ellipsometer. S OUT1 , S OUT2 ,……, S OUTn .

[0078] For each of the above periods, based on the recorded incident spectrum and the collected output Mueller spectrum information, the matrix elements of the Mueller matrix are constructed and analyzed to obtain the first theoretical period value and the first theoretical structure parameter corresponding to each period. The method is the same as the method for obtaining the second theoretical period value and the second theoretical structure parameter, so it will not be repeated here.

[0079] Calculating a first period difference between the first theoretical period value and the first period value, and a first structure difference between the first theoretical structure parameter and the first structure parameter; Fitting the first period difference to obtain a second period difference of each period in the remaining periods of the period-variable structure, and fitting the first structure difference to obtain a second structure difference of each period in the remaining periods of the period-variable structure; The first period difference between the first theoretical period value and the first period value, and the first structure difference between each first theoretical structure parameter and the first structure parameter corresponding thereto are calculated respectively.

[0080] In a feasible implementation, the first index parameter X=(P 0真实 , X 1真实 , X 2真实 , X 3真实 , X 4真实 ), where P 0真实 represents the first period value, X n真实 represents the first structural parameter, and the theoretical structural parameter X is obtained by analyzing the Mueller matrix 理论 =(P 0理论 , X 1理论 , X 2理论 , X 3理论 , X 4理论 ), where P 0理论 represents the second theoretical cycle value, X n理论 represents the second structural parameter, and the theoretical structural parameter X 理论 Put it into a separate preliminary spectrum library, and at the same time, the determined first theoretical spectrum, second theoretical spectrum, second theoretical period value and second theoretical structure parameter are also put into the preliminary spectrum library.

[0081] Calculate P 0真实 With P 0理论 The first period difference between the two is used to calculate each structural parameter X n真实 With X n理论 The first structural difference between them, in this implementation manner, corresponds to four first structural difference values.

[0082] The first period difference values ​​corresponding to at least three periods are fitted to obtain the second period difference values ​​corresponding to all other periods; for each first structural difference value, the first structural difference values ​​corresponding to at least three periods are fitted to obtain the second structural difference values ​​corresponding to all other periods.

[0083] The second period value is determined according to the second theoretical period value and the second period difference value, and the second structural parameter is determined according to the second theoretical structural parameter and the second structural difference value.

[0084] The second period value is obtained by calculating the second theoretical period value and the second period difference in the same manner as the first period difference.

[0085] For example, when the first cycle difference is the first theoretical cycle value minus the first cycle value, the second cycle value is the second theoretical cycle value minus the second cycle difference; when the first cycle difference is the first cycle value minus the first theoretical cycle value, the second cycle value is the second theoretical cycle value plus the second cycle difference.

[0086] The method of determining the second structural parameter based on the second theoretical structural parameter and the second structural difference is the same as that thereof, and thus will not be described in detail.

[0087] In a feasible implementation, the fitted second period difference and each second structure difference are added into a pre-constructed preliminary spectral library accordingly, and the second theoretical period value and the second theoretical structure parameter stored in the preliminary spectral library are updated to the second period value and the second structure parameter, that is, the constructed spectral library is obtained by updating the preliminary spectral library.

[0088] The present invention obtains a first theoretical spectrum of at least three periods of a periodic variable structure, and fits it to obtain a second theoretical spectrum of the remaining periods of the periodic variable structure. By fitting the difference between the theoretical structural parameters and the actual structural parameters of at least three periods, the theoretical structural parameters obtained from the analysis of the second theoretical spectrum are corrected to obtain the second period value and the second structural parameter, thereby realizing the fitting of the second theoretical spectral library data of the remaining periods based on the first theoretical spectral library data of at least three periods, effectively reducing the time required for separately modeling the structure of each period to form a spectral library, and improving the construction speed of the spectral library.

[0089] The present invention also provides a method for measuring optical critical dimensions, such as Figure 8 As shown, including: Step 801, obtaining an emission Mueller spectrum of the periodic structure to be measured; The outgoing Mueller spectrum after the incident light acts on the periodic structure to be measured is obtained by using an ellipsometer or other spectral measurement device.

[0090] The periodic structure to be tested is a periodically variable structure, that is, a structure whose CD and / or space changes during the semiconductor manufacturing process.

[0091] Step 802, matching the output Mueller spectrum in a spectrum library constructed by the spectrum library construction method described in the above methods, to obtain a matching spectrum with the highest similarity to the output Mueller spectrum; The acquired outgoing Mueller spectrum is matched against a pre-built spectral library.

[0092] Specifically, the spectrum library pre-constructed by the methods described above contains spectrum library data of all periods of the periodic variable structure corresponding to the periodic structure to be measured.

[0093] The outgoing Mueller spectrum of the periodic structure to be measured is matched with the first theoretical spectrum and the second theoretical spectrum in the spectrum library to obtain a matching spectrum with the highest similarity to the outgoing Mueller spectrum.

[0094] In this embodiment, the spectrum matching method is not limited, and it only needs to be able to quickly obtain the matching spectrum corresponding to the output Mueller spectrum.

[0095] Step 803: Using the index parameters obtained by matching the spectrum index as measurement parameters of the periodic structure to be measured.

[0096] The index parameters corresponding to the obtained matching spectrum index are obtained, wherein the index parameters include the period value of the matching spectrum and various structural parameters, which are used as measurement parameters of the periodic structure to be measured, that is, the measurement result of its optical critical dimension measurement is obtained.

[0097] The present invention uses a pre-constructed spectral library model. When realizing the measurement of a periodic variable structure, the pre-constructed spectral library can be used to measure the period value and structural parameters of the periodic variable structure at any period. An unexpected effect is that the construction time of the spectral library required for measurement is reduced, thereby reducing the total time required for measurement and improving the efficiency of optical critical dimension measurement.

[0098] The following is a description of a device for constructing a spectral library provided by the present invention. The device for constructing a spectral library described below and the method for constructing a spectral library described above can be referred to in correspondence with each other.

[0099] like Fig. 9 As shown, the device for constructing a spectrum library includes a first acquisition module 901, a second acquisition module 902 and a construction module 903: A first acquisition module 901 is used to respectively acquire first-type spectral library data of at least three periods of a periodic variable structure; A variable period structure is a structure whose period (pitch) changes during the semiconductor manufacturing process.

[0100] Alternatively, for example, a structure with a fixed CD (Critical Dimension) and a variable space (the distance between two unit structures), or a structure with a variable CD and a fixed space. Figure 2 shown.

[0101] Since the constructed spectral library is used to measure the critical dimensions of the periodic structure during the production process, multiple periodic structures that cover the process requirements of the semiconductor process for the periodic structure to be measured can be designed in advance.

[0102] For example, for a fixed CD, there are 7 different spaces in the process requirements of a semiconductor manufacturing process, that is, the period-variable structure has 7 different periods in the process requirements.

[0103] At least three periods are determined from all the periods of the periodic variable structure, and first-category spectral library data of the periodic variable structure in these three periods are acquired.

[0104] In a specific embodiment, referring to Figure 3 Corresponding to the above-mentioned variable periodic structure with 7 different periods, the maximum period (period 1), the minimum period (period 3) and an intermediate period (period 2) required by the process are selected, and the periodic structures corresponding to the selected three periods are modeled respectively to obtain the first type of spectral library data corresponding to the three periods.

[0105] It can be understood that the first type of spectral library data represents the spectral library data obtained by modeling. The first type of spectral data of each period includes the theoretical spectrum of the period and the period value and structural parameters corresponding to the period.

[0106] In other feasible implementations, if the number of cycles required by the variable-cycle structure process is large, more cycles may be selected and modeled accordingly.

[0107] A second acquisition module 902 is configured to determine, based on the first type of spectrum library data, second type of spectrum library data corresponding to the remaining periods of the periodic variable structure in a one-to-one manner when there are linear differences in the spectra of the first type of spectrum library data of the at least three periods; Further, it is determined whether there are linear differences in the spectra of the first type of spectral library data of at least three periods. If so, the second type of spectral library data of the remaining periods of the periodic variable structure can be determined based on the first type of spectral library data.

[0108] In a specific embodiment, Figure 4 Figures (a) and (b) are schematic diagrams of theoretical spectra obtained by modeling three different periods of a periodic variable structure. The CD of the periodic variable structure is fixed at 40nm, and the space is changed to 70nm, 80nm, and 90nm respectively.

[0109] It can be seen that when the CD of the periodic variable structure is fixed and the space changes, the spectral amplitude increases by about 0.2 with every 10nm increase in space at a wavelength of 400 to 440nm; the spectral amplitude increases by about 0.05 with every 10nm increase in space at a wavelength of 600 to 900nm. The spectral phase decreases by about 0.125 with every 10nm increase in space at a wavelength of 420 to 460nm, and decreases by about 0.1 with every 10nm increase in space at a wavelength of 540 to 680nm.

[0110] Figure 5 Figures (a) and (b) are schematic diagrams of theoretical spectra obtained by modeling three different periods of the periodic variable structure. The space of the periodic variable structure is fixed at 80nm, and the CD is changed to 30nm, 40nm and 50nm respectively.

[0111] It can be seen that when the space of the periodic variable structure is fixed and the CD changes, the peak position of the spectral amplitude shifts by about 40nm with every 10nm increase in CD at a wavelength of 300 to 540nm; the spectral amplitude decreases by about 0.15 with every 10nm increase in CD at a wavelength of 660 to 900nm; the spectral phase shifts by about 40nm with every 10nm increase in CD at a wavelength of 380 to 540nm, and the phase valley shifts by about 40nm with every 10nm increase in CD at a wavelength of 540 to 640nm, and the phase value decreases by about 0.4 with every 10nm increase in CD at a wavelength of 10nm.

[0112] That is to say, when in the spectral amplitude and spectral phase diagrams of at least three periods, at at least one wavelength, there is a linear relationship between the spectral amplitude and the spectral phase as the period changes, it can be considered that there are linear differences in the spectra of the first type of spectral data of at least three periods.

[0113] For periodic variable structures, since the spectrum of periodic changes has obvious linear differences, it is believed that the theoretical spectrum of other periods of the periodic variable structure can be determined by at least three known theoretical spectra, so that the corresponding structural parameters can be obtained according to the theoretical spectrum analysis of other periods, and then the second type of spectral library data corresponding to other periods can be obtained.

[0114] It can be understood that the second type of spectral library data represents the spectral library data obtained by fitting. The second type of spectral library data includes the theoretical spectrum, period value and structure parameter value obtained by fitting each period.

[0115] The construction module 903 is used to integrate the first type of spectral library data and the second type of spectral library data to construct a spectral library.

[0116] By integrating the first type of spectral library data obtained by modeling and the second type of spectral library data obtained by fitting and putting them into the same spectral library, a spectral library for OCD measurement can be constructed.

[0117] It should be noted that the spectral library constructed at this time contains the spectral library data corresponding to all periods of the periodic variable structure in the process requirements. Therefore, in the production process, a constructed spectral library can be matched with the output spectra of all periods of the periodic variable structure to obtain the measurement results of each period of the periodic variable structure.

[0118] The present invention obtains first-category spectral library data by modeling structures corresponding to at least three periods of a periodic variable structure, obtains second-category spectral library data of structures corresponding to other periods of the periodic variable structure in process requirements based on fitting of the first-category spectral data, and constructs a spectral library by integrating the first-category spectral library data and the second-category spectral library data, thereby reducing the number of modeling times required for the spectral library construction process in OCD measurement, thereby reducing the construction time of the spectral library and improving the construction efficiency of the spectral library. In addition, an unexpected effect is that the critical dimension measurement of structures corresponding to all periods of the periodic variable structure can be achieved through a constructed spectral library.

[0119] The optical critical dimension measuring device provided by the present invention is described below. The optical critical dimension measuring device described below and the optical critical dimension measuring method described above can be referred to each other.

[0120] like Fig.10 As shown, the optical critical dimension measuring device includes a receiving module 1001, a matching module 1002 and a determining module 1003: A receiving module 1001 is used to obtain an outgoing Mueller spectrum of a periodic structure to be measured; The outgoing Mueller spectrum after the incident light acts on the periodic structure to be measured is obtained by using an ellipsometer or other spectral measurement device.

[0121] The periodic structure to be tested is a periodically variable structure, that is, a structure whose CD and / or space changes during the semiconductor manufacturing process.

[0122] A matching module 1002 is used to match the output Mueller spectrum in a spectrum library constructed by the spectrum library construction method described in the above methods to obtain a matching spectrum with the highest similarity to the output Mueller spectrum; The acquired outgoing Mueller spectrum is matched against a pre-built spectral library.

[0123] Specifically, the spectrum library pre-constructed by the methods described above contains spectrum library data of all periods of the periodic variable structure corresponding to the periodic structure to be measured.

[0124] The outgoing Mueller spectrum of the periodic structure to be measured is matched with the first theoretical spectrum and the second theoretical spectrum in the spectrum library to obtain a matching spectrum with the highest similarity to the outgoing Mueller spectrum.

[0125] In this embodiment, the spectrum matching method is not limited, and it only needs to be able to quickly obtain the matching spectrum corresponding to the output Mueller spectrum.

[0126] The determination module 1003 is configured to use the index parameters obtained by matching the spectrum index as the measurement parameters of the periodic structure to be measured.

[0127] The index parameters corresponding to the obtained matching spectrum index are obtained, wherein the index parameters include the period value of the matching spectrum and various structural parameters, which are used as measurement parameters of the periodic structure to be measured, that is, the measurement result of its optical critical dimension measurement is obtained.

[0128] The present invention uses a pre-constructed spectral library model. When realizing the measurement of a periodic variable structure, the pre-constructed spectral library can be used to measure the period value and structural parameters of the periodic variable structure at any period. An unexpected effect is that the construction time of the spectral library required for measurement is reduced, thereby reducing the total time required for measurement and improving the efficiency of optical critical dimension measurement.

[0129] Fig.11 An example of a physical structure diagram of an electronic device is shown in FIG. Fig.11 As shown, the electronic device may include: a processor 1110, a communication interface 1120, a memory 1130 and a communication bus 1140, wherein the processor 1110, the communication interface 1120 and the memory 1130 communicate with each other through the communication bus 1140. The processor 1110 may call the logic instructions in the memory 1130 to execute a method for constructing a spectral library, the method comprising: respectively obtaining first-class spectral library data of at least three periods of a periodic variable structure; fitting and determining second-class spectral library data corresponding to the remaining periods of the periodic variable structure according to the first-class spectral library data; and integrating the first-class spectral library data and the second-class spectral library data to construct a spectral library.

[0130] In addition, the logic instructions in the above-mentioned memory 1130 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0131] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the method for constructing a spectral library provided by the above methods, which includes: obtaining first-category spectral library data of at least three periods of a periodic variable structure respectively; determining second-category spectral library data corresponding to the remaining periods of the periodic variable structure according to fitting of the first-category spectral library data; and integrating the first-category spectral library data and the second-category spectral library data to construct a spectral library.

[0132] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the method for constructing a spectral library provided by the above-mentioned methods, the method comprising: respectively acquiring first-category spectral library data of at least three periods of a periodic variable structure; determining second-category spectral library data corresponding one-to-one to the remaining periods of the periodic variable structure according to fitting of the first-category spectral library data; and integrating the first-category spectral library data and the second-category spectral library data to construct a spectral library.

[0133] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those of ordinary skill in the art may understand and implement it without creative effort.

[0134] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a spectral library, characterized in that: include: respectively acquiring first-type spectral library data of at least three periods of periodic variable structures; In the case that there are linear differences in the spectra of the at least three periods of the first type of spectrum library data, determining the second type of spectrum library data corresponding to the remaining periods of the periodic variable structure according to the first type of spectrum library data; The first category of spectral library data and the second category of spectral library data are integrated to construct a spectral library.

2. The method for constructing a spectral library according to claim 1, characterized in that: The periodically variable structure is a structure in which a critical dimension and / or a spacing changes during a semiconductor process.

3. The method for constructing a spectral library according to claim 2, characterized in that: The critical dimension includes sub-critical dimensions of the periodically variable structure in several directions, and when the critical dimension changes, the sub-critical dimension in at least one direction changes; The pitch includes sub-pitch of the periodically variable structure in several directions, and when the pitch changes, the sub-pitch in at least one direction changes.

4. The method for constructing a spectral library according to claim 1, characterized in that: The step of respectively acquiring first-type spectral library data of at least three periods of the periodic variable structure specifically includes: For each period of the at least three periods, obtaining a first theoretical spectrum of each period; Acquire a first period value and a first structure parameter of each period as a first index parameter; After establishing an index between the first theoretical spectrum of each period and the first index parameter, the first type of spectrum data of each period is determined.

5. The method for constructing a spectral library according to claim 4, characterized in that: The step of obtaining the first theoretical spectrum of each period specifically includes: A rigorous coupled wave analysis is performed on the periodic variable structure in each period to obtain a first theoretical spectrum of each period.

6. The method for constructing a spectral library according to claim 4 or 5, characterized in that: The step of determining the second type of spectral library data corresponding to the remaining periods of the periodic variable structure according to the first type of spectral library data specifically includes: Building a model of the period-variable structure based on the first theoretical spectrum of each period of the at least three periods, and determining second theoretical spectra corresponding to the remaining periods of the period-variable structure based on the model of the period-variable structure; Analyze each of the second theoretical spectra respectively to obtain a second theoretical period value and a second theoretical structure parameter corresponding to each of the second theoretical spectra; Correcting the second theoretical period value and the second theoretical structure parameter to obtain a second period value and a second structure parameter corresponding to the second theoretical spectrum as a second index parameter; After establishing an index between the second theoretical spectrum of each period in the remaining periods of the periodic variable structure and the second index parameter, the spectrum is determined as the second type of spectrum library data.

7. The method for constructing a spectral library according to claim 6, characterized in that: The step of correcting the second theoretical period value and the second theoretical structure parameter to obtain the second period value and the second structure parameter corresponding to the second theoretical spectrum as the second index parameter specifically includes: Acquire a first theoretical cycle value and a first theoretical structure parameter of each cycle in the at least three cycles; Calculating a first period difference between the first theoretical period value and the first period value, and a first structure difference between the first theoretical structure parameter and the first structure parameter; Fitting the first period difference to obtain a second period difference of each period in the remaining periods of the period-variable structure, and fitting the first structure difference to obtain a second structure difference of each period in the remaining periods of the period-variable structure; The second period value is determined according to the second theoretical period value and the second period difference value, and the second structural parameter is determined according to the second theoretical structural parameter and the second structural difference value.

8. A method for measuring an optical critical dimension, characterized in that: include: Obtaining the outgoing Mueller spectrum of the periodic structure to be measured; Matching the output Mueller spectrum in a spectral library constructed by the spectral library construction method according to any one of claims 1 to 7 to obtain a matching spectrum with the highest similarity to the output Mueller spectrum; The index parameters obtained by matching the spectrum index are used as measurement parameters of the periodic structure to be measured.

9. A device for constructing a spectral library, characterized in that: include: A first acquisition module is used to respectively acquire first-type spectral library data of at least three periods of the periodic variable structure; A second acquisition module is used to determine, when there are linear differences in the spectra of the at least three periods of the first-type spectrum library data, the second-type spectrum library data corresponding to the remaining periods of the periodic variable structure according to the first-type spectrum library data; A construction module is used to integrate the first category spectral library data and the second category spectral library data to construct a spectral library.

10. An optical critical dimension measuring device, characterized in that: include: A receiving module, used for obtaining an outgoing Mueller spectrum of the periodic structure to be measured; A matching module, configured to match the output Mueller spectrum in a spectral library constructed by the spectral library construction method according to any one of claims 1 to 7, to obtain a matching spectrum with the highest similarity to the output Mueller spectrum; The determination module is used to use the index parameters obtained by matching the spectrum index as the measurement parameters of the periodic structure to be measured.

Images