WO2007123696A2 - Métrologie optique sur puce - Google Patents

Métrologie optique sur puce Download PDF

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Publication number
WO2007123696A2
WO2007123696A2 PCT/US2007/007932 US2007007932W WO2007123696A2 WO 2007123696 A2 WO2007123696 A2 WO 2007123696A2 US 2007007932 W US2007007932 W US 2007007932W WO 2007123696 A2 WO2007123696 A2 WO 2007123696A2
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Prior art keywords
diffraction signal
measured
features
die structure
simulated
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PCT/US2007/007932
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English (en)
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WO2007123696A3 (fr
Inventor
Shifang Li
Junwei Bao
Vi Vuong
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Tokyo Electron Limited
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Publication of WO2007123696A2 publication Critical patent/WO2007123696A2/fr
Publication of WO2007123696A3 publication Critical patent/WO2007123696A3/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
    • G03F7/70605—Workpiece metrology
    • G03F7/70616—Monitoring the printed patterns
    • G03F7/70625—Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness

Definitions

  • the present application generally relates to examining a structure formed on a semiconductor wafer using optical metrology, and, more particularly, to determining one or more features of an in-die structure formed on a semiconductor wafer using optical metrology.
  • Optical metrology involves directing an incident beam at a structure, measuring the resulting diffracted beam, and analyzing the diffracted beam to determine a feature of the structure.
  • optical metrology is typically used for quality assurance. For example, after fabricating a test structure, such as a grating array, in a test pad, in proximity to a die on a semiconductor wafer, an optical metrology system is used to determine the profile of the test structure. By determining the profile of the test structure, the quality of the fabrication process utilized to form the test structure, and by extension the die proximate the test structure, can be evaluated.
  • test structure in the test pad has the same profile as a structure in the die (i.e., an in-die structure).
  • This assumption has limitations because the local environment can affect the fabrication process and alter the profile of the test structure in the test pad relative to the in-die structure.
  • a correlation is determined between one or more features of a test structure to be formed on a test pad and one or more features of a corresponding in-die structure.
  • a measured diffraction signal measured off the test structure is obtained.
  • One or more features of the test structure are determined using the measured diffraction signal.
  • the one or more features of the in-die structure are determined based on the one or more determined features of the test structure and the determined correlation.
  • Fig. 1 is an exemplary optical metrology system
  • FIGs. 2A-2E depict exemplary hypothetical profiles
  • FIG. 3 depicts an exemplary wafer with dies and scribe lines
  • Fig. 4 depicts an exemplary process of determining one or more features of an in-die structure
  • Fig. 5 depicts an exemplary system configured to determine one or more features of an in-die structure
  • Fig. 6 depicts another exemplary process of determining one or more features of an in-die structure
  • Fig. 7 depicts still another exemplary process of determining one or more features of an in-die structure
  • Figs. 8A and 8B depicts profile parameters used to define hypothetical profiles
  • Fig. 8C depicts a multi-level in-die structure
  • Fig. 9 depicts another exemplary system configured to determine one or more features of an in-die structure.
  • an optical metrology system 100 can be used to examine and analyze a structure formed on a semiconductor wafer 104.
  • optical metrology system 100 can be used to determine one or more features of a periodic grating 102 formed on wafer 104, such as one or more critical dimensions, profile, and the like.
  • periodic grating 102 can be formed in a test pad on wafer 104, such as adjacent to a die formed on wafer 104.
  • Periodic grating 102 can be formed in a scribe line and/or an area of the die that does not interfere with the operation of the die.
  • optical metrology system 100 can include a photometric device with a source 106 and a detector 1 12.
  • Periodic grating 102 is illuminated by an incident beam 108 from source 106.
  • the incident beam 108 is directed onto periodic grating 102 at an angle of incidence ⁇ , with respect to normal n of periodic grating 102 and an azimuth angle ⁇ (i.e., the angle between the plane of incidence beam 108 and the direction of the periodicity of periodic grating 102).
  • Diffracted beam 1 10 leaves at an angle of ⁇ a with respect to normal and is received by detector 112.
  • Detector 112 converts the diffracted beam 1 10 into a measured diffraction signal, which can include reflectance, tan ( ⁇ ), cos( ⁇ ), Fourier coefficients, and the like.
  • Optical metrology system 100 also includes a processing module 114 configured to receive the measured diffraction signal and analyze the measured diffraction signal. As described below, one or more features of periodic grating 102 can then be determined using a library-based process or a regression-based process. 2. Library-based Process of Determining Feature of Structure
  • the measured diffraction signal is compared to a library of simulated diffraction signals. More specifically, each simulated diffraction signal in the library is associated with a hypothetical profile of the structure. When a match is made between the measured diffraction signal and one of the simulated diffraction signals in the library or when the difference of the measured diffraction signal and one of the simulated diffraction signals is within a preset or matching criterion, the hypothetical profile associated with the matching simulated diffraction signal is presumed to represent the actual profile of the structure. The matching simulated diffraction signal and/or hypothetical profile can then be utilized to determine whether the structure has been fabricated according to specifications.
  • processing module 114 then compares the measured diffraction signal to simulated diffraction signals stored in a library 116.
  • Each simulated diffraction signal in library 116 can be associated with a hypothetical profile.
  • the hypothetical profile associated with the matching simulated diffraction signal can be presumed to represent the actual profile of periodic grating 102.
  • the set of hypothetical profiles stored in library 116 can be generated by characterizing a hypothetical profile model using a set of profile parameters, then varying the set of profile parameters to generate hypothetical profiles of varying shapes and dimensions.
  • the process of characterizing a profile using a set of profile parameters can be referred to as parameterizing.
  • hypothetical profile 200 can be characterized by profile parameters hi and wl that define its height and width, respectively.
  • additional shapes and features of hypothetical profile 200 can be characterized by increasing the number of profile parameters.
  • hypothetical profile 200 can be characterized by profile parameters hi, wl, and w2 that define its height, bottom width, and top width, respectively.
  • the width of hypothetical profile 200 can be referred to as the critical dimension (CD).
  • profile parameter wl and w2 can be described as defining the bottom CD and top CD, respectively, of hypothetical profile 200.
  • the set of hypothetical profiles stored in library 116 can be generated by varying the profile parameters that characterize the hypothetical profile model. For example, with reference to Fig. 2B, by varying profile parameters hi, wl, and w2, hypothetical profiles of varying shapes and dimensions can be generated. Note that one, two, or all three profile parameters can be varied relative to one another.
  • the number of hypothetical profiles and corresponding simulated diffraction signals in the set of hypothetical profiles and simulated diffraction signals stored in library 116 depends, in part, on the range over which the set of profile parameters and the increment at which the set of profile parameters are varied.
  • the hypothetical profiles and the simulated diffraction signals stored in library 116 are generated prior to obtaining a measured diffraction signal from an actual structure.
  • the range and increment (i.e., the range and resolution) used in generating library 116 can be selected based on familiarity with the fabrication process for a structure and what the range of variance is likely to be.
  • the range and/or resolution of library 116 can also be selected based on empirical measures, such as measurements using AFM, X-SEM, and the like.
  • the measured diffraction signal is compared to a simulated diffraction signal (i.e., a trial diffraction signal).
  • the simulated diffraction signal is generated prior to the comparison using a set of profile parameters (i.e., trial profile parameters) for a hypothetical profile.
  • the measured diffraction signal and the simulated diffraction signal do not match or when the difference of the measured diffraction signal and one of the simulated diffraction signals is not within a preset or matching criterion, another simulated diffraction signal is generated using another set of profile parameters for another hypothetical profile, then the measured diffraction signal and the newly generated simulated diffraction signal are compared.
  • the hypothetical profile associated with the matching simulated diffraction signal is presumed to represent the actual profile of the structure.
  • the matching simulated diffraction signal and/or hypothetical profile can then be utilized to determine whether the structure has been fabricated according to specifications.
  • the processing module 1 14 can generate a simulated diffraction signal for a hypothetical profile, and then compare the measured diffraction signal to the simulated diffraction signal. As described above, if the measured diffraction signal and the simulated diffraction signal do not match or when the difference of the measured diffraction signal and one of the simulated diffraction signals is not within a preset or matching criterion, then processing module 114 can iteratively generate another simulated diffraction signal for another hypothetical profile.
  • the subsequently generated simulated diffraction signal can be generated using an optimization algorithm, such as global optimization techniques, which includes simulated annealing, and local optimization techniques, which includes steepest descent algorithm.
  • the simulated diffraction signals and hypothetical profiles can be stored in a library 116 (i.e., a dynamic library).
  • the simulated diffraction signals and hypothetical profiles stored in library 116 can then be subsequently used in matching the measured diffraction signal.
  • simulated diffraction signals are generated to be compared to measured diffraction signals.
  • the simulated diffraction signals can be generated by applying Maxwell's equations and using a numerical analysis technique to solve Maxwell's equations. It should be noted, however, that various numerical analysis techniques, including variations of RCWA, can be used.
  • RCWA In general, RCWA involves dividing a hypothetical profile into a number of sections, slices, or slabs (hereafter simply referred to as sections). For each section of the hypothetical profile, a system of coupled differential equations generated using a Fourier expansion of Maxwell's equations (i.e., the components of the electromagnetic field and permittivity (£) ⁇ ). The system of differential equations is then solved using a diagonal ization procedure that involves eigenvalue and eigenvector decomposition (i.e., Eigen-decomposition) of the characteristic matrix of the related differential equation system. Finally, the solutions for each section of the hypothetical profile are coupled using a recursive-coupling schema, such as a scattering matrix approach.
  • a recursive-coupling schema such as a scattering matrix approach.
  • the simulated diffraction signals can be generated using a machine learning system (MLS) employing a machine learning algorithm, such as back-propagation, radial basis function, support vector, kernel regression, and the like.
  • MLS machine learning system
  • a machine learning algorithm such as back-propagation, radial basis function, support vector, kernel regression, and the like.
  • the simulated diffraction signals in a library of diffraction signals are generated using a MLS.
  • a set of hypothetical profiles can be provided as inputs to the MLS to produce a set of simulated diffraction signals as outputs from the MLS.
  • the set of hypothetical profiles and set of simulated diffraction signals are stored in the library.
  • the simulated diffractions used in regression-based process are generated using a MLS, such as MLS 118 (Fig. 1).
  • a MLS such as MLS 118 (Fig. 1).
  • an initial hypothetical profile can be provided as an input to the MLS to produce an initial simulated diffraction signal as an output from the MLS. If the initial simulated diffraction signal does not match the measured diffraction signal, another hypothetical profile can be provided as an additional input to the MLS to produce another simulated diffraction signal.
  • Fig. 1 depicts processing module 114 having both a library 116 and MLS 118. It should be recognized, however, that processing module 114 can have either library 116 or MLS 118 rather than both. For example, if processing module 114 only uses a library- based process, MLS 118 can be omitted. Alternatively, if processing module 114 only uses a regression-based process, library 116 can be omitted. Note, however, a regression- based process can include storing hypothetical profiles and simulated diffraction signals generated during the regression process in a library, such as library 116.
  • Fig. 3 depicts wafer 104 having a plurality of dies 302 and scribe lines 304 defined between the dies 302.
  • a test pad 306 is defined with a test structure 308 to be formed in test pad 306.
  • test pad 306 is depicted as being disposed within a scribe line 304. It should be recognized, however, that test pad 306 can be disposed within a die 302, such as in an area of die 302 large enough to accommodate test pad 306 without interfering with the operation of die 302. It should also be recognized that test pad 306 may not be an actual physical structure formed on wafer 104. Instead, test pad 306 may designate an area on wafer 104 in which test structure 308 is formed.
  • test structure 308 in test pad 306 has a corresponding structure 310 to be formed in die 302 (i.e., a corresponding in-die structure 310).
  • Test structure 308 can be designed and fabricated under conditions such that some of its properties are correlated to in-die structure 310.
  • test structure 308 can be a thin-film stack fabricated with materials and having dimensions that are similar to in-die structure 310.
  • test pad 306 can include a set of test structures 308 that vary in material, shape, and dimensions.
  • test structures 308 can be periodic gratings of varying pitch, grating orientations, and/or line to width ratios.
  • a set of test pads 306 be designed with varying sensitivity to the profile parameters of the in-die structures.
  • the features to be determined for the in-die structure include top CD, bottom CD, thickness of stack films, and line-end shortening.
  • One test structure can be designed to have thin film pads that have same stack or stacks as the stack or stacks in the in-die structure.
  • Another test structure can be designed with CD that correlates well with line-end shortening of the indie structure.
  • Fig. 4 depicts an exemplary process of determining one or more features of an in-die structure using a correlation determined between a test structure in a test pad and a corresponding in-die structure.
  • any number of test pads 306 and any number of test structures 308 can be defined to correspond to in-die structure 310.
  • test pad 306 can be formed in scribe lines 304 or in a die 302.
  • a correlation between test structure 308 and corresponding in-die structure 310 is determined.
  • the correlation can be determined through simulation or actual fabrication.
  • a set of test structures 308 and a set of in-die structures 310 can be simulated or fabricated on one or more test wafers.
  • One or more features of the test structures 308 in the simulated or fabricated set of test structures 308 can be correlated to one or more features of the in-die structures 310 in the simulated or fabricated set of in-die structures 310.
  • a bottom CD of the test structures 308 can be correlated to a bottom CD of the in-die structures 310.
  • the correlation can be linear, parabolic, and the like.
  • step 402 After the correlation has been determined in step 402 (Fig. 4), an actual production wafer is fabricated with test structure 308 formed on the production wafer.
  • step 404 Fig. 4 of the present exemplary process, a measured diffraction signal measured off test structure 308 formed on the production wafer is obtained.
  • the measured diffraction signal can be measured using a photometric device of an optical metrology system.
  • the measured diffraction signal can be obtained directly from the photometric device, or obtained from a buffer, memory, or other storage medium.
  • step 406 (Fig. 4), one or more features of test structure 308 are determined based on the measured diffraction signal.
  • a library-based or regression-based process can be used to determine one or more features, such as the profile, of test structure 308.
  • step 408 one or more features of a corresponding in-die structure 310 is determined based on the one or more features of test structure 308 determined in step 406 (Fig. 4) and the correlation determined in step 402 (Fig. 4).
  • a bottom CD of test structure 308 was determined in step 406 (Fig. 4).
  • a bottom CD of in-die structure 310 is determined based on the bottom CD determined for test structure 308 in step 406 (Fig. 4) and the correlation between the bottom CD of in-die structure 310 and the bottom CD of test structure 308 determined in step 402 (Fig. 4).
  • the one or more features of in-die structure 310 determined in step 408 are of an in-die structure 310 that is formed on the same production wafer as test structure 308.
  • in-die structure 310 is formed adjacent to test structure 308 on the same production wafer.
  • the one or more features of in-die structure 310 determined in step 408 are of an in-die structure 310 that is formed on another production wafer as test structure 308.
  • in-die structure 310 can be determined without actually examining in-die structure 310. This may be particularly advantageous when it is difficult to actually measure in-die structure 310.
  • in-die structure 310 may be formed in an area of a die that is not big enough to measure using an optical metrology system.
  • Fig. 5 depicts an exemplary system 500 configured to determine one or more features of an in-die structure.
  • exemplary system 500 includes a correlation 502 of test structures and in-die structure. As described above, correlation 502 can be determined in advance through simulation or fabrication of test wafers. Correlation 502 can be embodied in any storage medium, such as a portion of memory, disk drive, and the like.
  • Exemplary system 500 also includes optical metrology system 100 with a photometric device 504, which can include source 106 and detector 112 (Fig. 1). When correlation 502 is determined in advance from fabricating test wafer, optical metrology system 100 can be used to determine the features of the test structures and in-die structures used in determining correlation 502.
  • photometric device 504 is used to measure a measured diffraction signal from a test structure in a test pad on a wafer.
  • Processor 506 can obtain the measured diffraction signal directly from photometric device 504 or from a buffer, memory, or other storage medium.
  • Processor 506 in processing module 114 is configured to determine one or more features of the test structure in the test pad using the measured diffraction signal.
  • Processor 506 is also configured to determine one or more features of the corresponding in-die structure based on the determined one or more features of the test structure and correlation 502.
  • processing module 114 need not include both library 116 and MLS 118.
  • MLS 118 can be omitted.
  • library 116 can be omitted.
  • exemplary system 500 can be implemented as an in-line system, meaning that exemplary system 500 is integrated with a fabrication tool or line 508 to examine and evaluate wafers as the wafers are being processed in fabrication tool or line 508.
  • exemplary system 500 can be implemented as an off-line system, meaning that exemplary system 500 is used to examine and evaluate wafers after they have been processed by fabrication tool or line 508. For example, after being processed on fabrication tool or line 508, wafers can be transferred to exemplary system 500 to be examined and evaluated.
  • Fig. 6 depicts an exemplary process of determining one or more features of an in-die structure using a correlation determined between a test structure in a test pad and a corresponding in-die structure and a measured diffraction signal from the in-die structure.
  • the in-die structure is examined using an optical metrology system.
  • step 602 of the present exemplary process a correlation between a test structure and a corresponding in-die structure is determined.
  • the correlation determined in the present step of the present exemplary process can be similar to the correlation determined in step 402 of the exemplary process depicted in Fig. 4 and described above.
  • step 604 of the present exemplary process a measured diffraction signal measured off the test structure formed on the production wafer is obtained.
  • the measured diffraction signal can be measured using a photometric device of an optical metrology system.
  • the measured diffraction signal can be obtained directly from the photometric device, or obtained from a buffer, memory, or other storage medium.
  • Step 604 of the present exemplary process can be similar to step 404 of the exemplary process depicted in Fig. 4 and described above.
  • step 606 one or more features of the test structure are determined based on the measured diffraction signal.
  • a library-based or regression- based process can be used to determine one or more features, such as the profile, of the test structure.
  • Step 606 of the present exemplary process can be similar to step 406 of the exemplary process depicted in Fig. 4 and described above.
  • step 608 one or more features of the corresponding in-die structure are determined based on the one or more features of the test structure determined in step 606 and the correlation determined in step 602.
  • step 608 of the present exemplary process one or more features of the corresponding in-die structure is determined based on a measured signal measured off the corresponding in-die structure formed on the production wafer.
  • step 608 includes a step 702 in which a measured diffraction signal measured off a corresponding in-die structure is obtained.
  • the measured diffraction signal measured off the corresponding in-die structure can be measured using the same photometric device used to obtain the measured diffraction signal measured off the test structure on the production wafer in step 604.
  • the measured diffraction signal in step 702 was measured off a corresponding in-die structure formed adjacent to the test structure on the same wafer from which the measured diffraction signal in step 604 (Fig. 6) was measured.
  • measured diffraction signal in step 702 was measured off a corresponding in-die structure that is formed on a different wafer than the wafer on which the test structure from which the measured signal in step 604 (Fig. 6) was measured was formed on.
  • step 704 one or more profile parameters of a hypothetical profile of the corresponding in-die structure to be used in determining one or more features of the corresponding in-die structure are fixed based on the one or more features of the test structure determined in step 606 and the correlation determined in step 602.
  • a library-based or regression-based process can be used to determine one or more features of a structure in optical metrology.
  • the profile of the structure is characterized using a hypothetical profile defined using a set of profile parameters.
  • one or more of the profile parameters used in a library-based or regression-based process are fixed based on the one or more features of the test structure determined in step 606 and the correlation determined in step 602.
  • steps 702 and 704 can be performed in any order.
  • step 702 can be performed in advance of step 704
  • step 704 can be performed in advance of step 702, or steps 702 and 704 can be performed concurrently.
  • step 706 one or more features of the in-die structure are determined based on the measured diffraction signal obtained in step 702 and the one or more profile parameters fixed in step 704. In particular, the profile parameters that were not fixed in step 704 can be determined in step 706.
  • a hypothetical profile 802 for the test structure is defined by two profile parameters (i.e., wl (corresponding to the bottom CD of the test structure) and h (corresponding to the height of the test structure)).
  • a hypothetical profile 804 for the in-die structure is defined by three profile parameters (i.e., wl 1 (corresponding to the bottom CD of the indie structure), w2' (corresponding to the top CD of the in-die structure), and h' (corresponding to the height of the in-die structure)).
  • step 606 the bottom CD (corresponding to profile parameter wl) and the height (corresponding to profile parameter h) of the test structure is determined based on the measured diffraction signal measured off the test structure in step 604 (Fig. 6).
  • step 702 a measured diffraction signal measured off the in-die structure is obtained.
  • step 704 values for profile parameters wl' and h' of hypothetical profile 804 for the in-die structure are fixed based on the values of the bottom CD and the height determined for the test structure in step 606 (Fig. 6) and the correlation determined in step 602 (Fig. 6).
  • step 706 Fig.
  • the top CD of the in-die structure can be determined based on the measured diffraction signal obtained in step 702 (Fig. 7) and the values for the bottom CD (corresponding to profile parameter wl') and height (corresponding to profile parameter h') fixed in step 704 (Fig. 7).
  • profile parameters can define characteristics of layers of materials, including compositions and thicknesses, that form the structure and one or more underlying layers.
  • in-die structure 310 is a complex structure having a bottom structure 806 and a top structure 808.
  • test structure 308 is formed to correspond to only bottom structure 806 of in-die structure 310.
  • step 602 the correlation between test structure 308 and the bottom structure 806 of in-die structure 310 is determined.
  • step 604 a measured diffraction signal measured off test structure 308 formed on a production wafer is obtained.
  • step 606 one or more features of test structure 308 are determined. For the sake of example, assume a bottom CD 810 of test structure 308 is determined.
  • step 702 a measured diffraction signal measured off in-die structure 310 having bottom structure 806 and top structure 808 is obtained.
  • step 704 Fig.
  • one or more profile parameters of the hypothetical profile of in-die structure 310 are fixed based on the one or more features of test structure 308 determined in step 606 (Fig. 6) (in this example, bottom CD 810) and the correlation determined in step 602 (Fig. 6).
  • step 706 (Fig. 7) one or more features of the in-die structure are determined based on the measured diffraction signal obtained in step 702 (Fig. 7) and the one or more profile parameters fixed in step 704 (Fig. 7) (in this example, the profile parameter corresponding to bottom CD 810).
  • the measured diffraction signal obtained in step 604 can be obtained after the wafer has been processed to form test structure 308 and bottom section 806 of in-die structure 310, but before the top section 808 of indie structure 310 has been formed.
  • the measured diffraction signal obtained in step 702 can then be obtained after the wafer has been processed to form top section 808 of in-die structure 310.
  • the measured diffraction signal obtained in step 604 can be obtained after the wafer has been processed to form test structure 308 and both bottom section 806 and top section 808 of in-die structure 310.
  • Fig. 9 depicts an exemplary system 900 configured to determine one or more features of an in-die structure using a correlation determined between a test structure in a test pad and a corresponding in-die structure and a measured diffraction signal from the in-die structure.
  • Exemplary system 900 includes a correlation 502 of test structures and in-die structure. As described above, correlation 502 can be determined in advance through simulation or fabrication of test wafers. Correlation 502 can be embodied in any storage medium, such as a portion of memory, disk drive, and the like.
  • Exemplary system 900 also includes optical metrology system 100 with a photometric device 504, which can include source 106 and detector 1 12 (Fig. 1).
  • optical metrology system 100 can be used to determine the one or more features of the test structures and in-die structures used in determining correlation 502.
  • photometric device 504 is used to measure a measured diffraction signal from a test structure in a test pad on a wafer.
  • Processor 506 can obtained the measured diffraction signal directly from the photometric device or from a buffer, memory, or other storage medium.
  • Processor 506 is configured to determine one or more features of the test structure in the test pad using the measured diffraction signal.
  • Processor 506 is also configured to determine one or more features of the corresponding in-die structure based on the determined feature of the test structure, correlation 502, and a measured diffraction signal measured off the in-die structure.
  • processor 506 is configured to obtain a measured diffraction signal measured off a corresponding in-die structure.
  • Processor 506 is configured to fix one or more profile parameters of a hypothetical profile of the corresponding in-die structure based on the determined one or more features of the test structure and correlation 502.
  • Processor 506 determines one or more features of the in-die structure based on the measured diffraction signal measured off the in-die structure and the fixed one or more profile parameters.
  • library 116 can include a first library 902 and a second library 904. It should be recognized that first library 902 and second library 904 can be portions of one library or separate libraries.
  • first library 902 includes sets of hypothetical profiles of the test structure and corresponding simulated diffraction signals. Thus, first library 902 is used in determining one or more features of the test structure based on a measured diffraction signal measured off the test structure.
  • Second library 904 includes sets of hypothetical profiles of the in-die structure with one or more profile parameters fixed and corresponding simulated diffraction signals. For example, returning to the example described above where a profile parameter corresponding to the bottom CD of the in-die structure is fixed based on the bottom CD determined for the test structure, second library 904 includes sets of hypothetical profiles with the fixed value for the profile parameter corresponding to the bottom CD. Second library 904 is used in determining one or more features of the in-die structure based on the measured diffraction signal measured off the in-die structure and the fixed one or more profile parameters, such as the profile parameter corresponding to the bottom CD described above.
  • the measured diffraction signal measured off the in-die structure can be compared only to the simulated diffraction signals in second library 904 with corresponding hypothetical profiles with the fixed values of the one or more profile parameters, such as the profile parameter corresponding to the bottom CD described above.
  • the simulated diffraction signals to be included in second library 904 can be generated by fixing values of the one or more profile parameters corresponding to the one or more features determined for the test structure. For example, assuming the bottom CD of the test structure is determined, the corresponding profile parameter of the bottom CD in the hypothetical profile of the in-die structure can be fixed in generating a corresponding simulated diffraction signal for the hypothetical profile. The simulated diffraction signal and the hypothetical profile are then stored in second library 904. [0077] Alternatively, in another exemplary embodiment, the simulated diffraction signals to be included in second library 904 can be generated by floating all profile parameters.
  • the measured diffraction signal measured off the in-die structure can be compared only to the simulated diffraction signals in second library 904 with corresponding hypothetical profiles with the fixed values of the one or more profile parameters. Additionally, the one or more profile parameters can be fixed during the time the measured diffraction signal is being compared to the simulated diffraction signals in second library 904. See U.S. Patent Application Ser. No. 10/735,212, titled PARAMETRIC OPTIMIZATION OF OPTICAL METROLOGY MODEL, filed on December 12, 2003, which is incorporated herein by reference in its entirety.
  • MLS 1 18 can include a first MLS 906 and a second MLS 908. It should be recognized that first MLS 906 and second MLS 908 can be portions of one MLS or separate MLSs.
  • first MLS 906 is configured to receive hypothetical profiles of the test structure as inputs and provide corresponding simulated diffraction signals as outputs.
  • first MLS 906 can be used in a regression-based process to determine one or more features of the test structure based on a measured diffraction signal measured off the test structure.
  • Second MLS 908 is configured to receive hypothetical profiles of the in-die structure with one or more profile parameters fixed as inputs and provide corresponding simulated diffraction signals as outputs. For example, returning to the example described above where a profile parameter corresponding to the bottom CD of the in-die structure is fixed based on the bottom CD determined for the test structure, second MLS 908 is configured to receive hypothetical profiles with the fixed value for the profile parameter corresponding to the bottom CD. Second MLS 908 can be used in a regression-based process to determine one or more features of the in-die structure based on the measured diffraction signal measured off the in-die structure and the fixed one or more profile parameters, such as the profile parameter corresponding to the bottom CD described above.
  • Second MLS 908 can be trained using hypothetical profiles of the in-die structure with one or more profile parameters fixed. Alternatively, second MLS 908 can be trained using hypothetical profiles of the in-die structure with all profile parameters floating. When second MLS 908 is trained with all profile parameters floating, the one or more profile parameters can be fixed when second MLS 908 is used in a regression-based process.
  • processing module 114 need not include both library 1 16 and MLS 118.
  • MLS 118 can be omitted.
  • library 116 can be omitted.
  • exemplary system 900 can be implemented as an in-line system, meaning that exemplary system 900 is integrated with a fabrication tool or line to examine and evaluate wafers as the wafers are being processed in the fabrication tool or line.
  • exemplary system 900 can be implemented as an off-line system, meaning that exemplary system 900 is used to examine and evaluate wafers after they have been processed by a fabrication tool or line. For example, after being processed on a fabrication tool or line, wafers can be transferred to exemplary system 900 to be examined and evaluated.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Testing Or Measuring Of Semiconductors Or The Like (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

Pour déterminer une ou plusieurs caractéristiques d'une structure intrapuce sur une puce formée sur une plaquette de semi-conducteur, on détermine une corrélation entre une ou plusieurs caractéristiques d'une structure de test destinée à être formée sur un plot de test, et une ou plusieurs caractéristiques d'une structure intrapuce correspondante. On obtient un signal de diffraction mesurée, la mesure étant effectuée à partir de la structure de test. On identifie une ou plusieurs caractéristiques de la structure de test à partir de ce signal de diffraction mesurée. La ou les caractéristiques de la structure intrapuce sont déterminées à partir d'une ou de plusieurs des caractéristiques identifiées sur la structure de test, ainsi que des corrélations déterminées.
PCT/US2007/007932 2006-03-30 2007-03-29 Métrologie optique sur puce WO2007123696A2 (fr)

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WO2016007413A1 (fr) * 2014-07-07 2016-01-14 Kla-Tencor Corporation Métrologie de réponse de signal basée sur des mesures de structures de substitution

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US20060009872A1 (en) * 2004-07-08 2006-01-12 Timbre Technologies, Inc. Optical metrology model optimization for process control

Cited By (5)

* Cited by examiner, † Cited by third party
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US7912679B2 (en) * 2007-09-20 2011-03-22 Tokyo Electron Limited Determining profile parameters of a structure formed on a semiconductor wafer using a dispersion function relating process parameter to dispersion
KR101365163B1 (ko) * 2007-09-20 2014-02-20 도쿄엘렉트론가부시키가이샤 구조물 시험 방법 및 구조물 시험 시스템
WO2016007413A1 (fr) * 2014-07-07 2016-01-14 Kla-Tencor Corporation Métrologie de réponse de signal basée sur des mesures de structures de substitution
US10151986B2 (en) 2014-07-07 2018-12-11 Kla-Tencor Corporation Signal response metrology based on measurements of proxy structures
TWI669500B (zh) * 2014-07-07 2019-08-21 美商克萊譚克公司 基於代理結構之量測之信號回應度量

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