Pattern height measurement using an electron beam system

Abstract

This disclosure relates to the determination of the pattern height of a pattern produced in a resist film by extreme ultraviolet (EUV) lithography. This determination is performed using an electron beam system, particularly a scanning electron microscope (SEM). In this regard, the disclosure provides an apparatus for determining the pattern height, wherein the apparatus includes a processor. The processor is configured to acquire an SEM image of the pattern from the SEM. Furthermore, the processor is configured to determine a contrast value associated with the pattern based on the acquired SEM image. Subsequently, the processor is configured to determine the pattern height based on calibration data and the determined contrast value.

Description

Technical Field

[0001] This disclosure relates to the determination of the pattern height of a pattern produced in a resist film by extreme ultraviolet (EUV) lithography. The determination of the pattern height—also referred to herein as pattern height measurement—is performed using an electron beam system, particularly a scanning electron microscope (SEM). In this regard, this disclosure provides an apparatus and method for determining the pattern height, as well as a computer program for performing the method. Background Technology

[0002] Electron beam systems (such as SEM) can be used to measure top-down parameters to determine photolithographic patterning performance (e.g., determining the critical dimension (CD), line edge roughness, or linewidth roughness of a pattern produced by photolithography). However, electron beam systems are typically limited in measuring other critical parameters, such as resist thickness or, consequently, the pattern height of a pattern produced in a resist film by photolithography. Notably, in this disclosure, the pattern height of a pattern produced in a resist film can be (after patterning with photolithography) given by the difference between the thickness of the resist film in the unpatterned region (typically the mask region) and the thickness of the resist film in the patterned region (where the mask allows photolithography to reach the resist film). Patterns typically have a repeating structure of unpatterned and patterned regions.

[0003] The aforementioned limitations of electron beam systems have led to the proliferation of competing techniques such as scattering measurements. Furthermore, to alleviate these limitations, tilting can be introduced into the electron beam metrology system. Specifically, height information can be extracted by tilting the electron beam at a certain angle. However, a significant limitation of introducing such tilting is that, in the case of very thin resist films, the tilt angle needs to be quite large. However, in doing so, the electron beam system will lose resolution and may therefore become unable to measure very small features of the pattern. This tilting method is feasible at most for thick resist films.

[0004] Therefore, this tilting method is not suitable for patterns obtained using EUV in resist films, because EUV requires very thin resist films. This is because the CD (Cutoff Disc Reduction) shrinks as the wavelength used in lithography decreases (even more so for EUV), and this needs to be compensated for by using a larger numerical aperture (NA). However, the depth of field (DoF) decreases as the numerical aperture (squared) decreases, and a correspondingly thinner resist film is needed to maintain a lower aspect ratio.

[0005] Therefore, this tilting method is being used less and less, and there is no good solution, especially for EUV. Summary of the Invention

[0006] In view of the foregoing, the embodiments of this disclosure aim to determine the pattern height of a pattern produced in a resist film using EUV. Specifically, the purpose of this disclosure is to enable the metrology of EUV-generated patterns using an electron beam system / SEM. The determination of the pattern height should be simple yet effective, and of course, should produce accurate results.

[0007] These and other objectives are achieved through the embodiments of this disclosure as described in the appended independent claims. Advantageous implementations of these embodiments are further defined in the dependent claims.

[0008] Specifically, this disclosure provides a method for accurately measuring the relative thickness of the resist and the pattern height of the pattern produced in these resist films by using a process of estimating and calibrating contrast values.

[0009] A first aspect of this disclosure provides an apparatus for determining the pattern height of a pattern produced in a resist film by EUV lithography, the apparatus comprising a processor configured to: acquire a SEM image of the pattern from a SEM; determine a contrast value associated with the pattern based on the acquired SEM image; and determine the pattern height based on calibration data and the determined contrast value.

[0010] Therefore, SEM can be used to determine pattern height without tilting the electron beam. Nevertheless, SEM can be used even when patterns are generated using EUV lithography, i.e., with very thin resist films. The determination performed by this apparatus is efficient yet simple and achieves good accuracy. Overall, this apparatus enables the metrology of patterns generated by improved EUV lithography.

[0011] The calibration data can be predetermined and allows the processor to derive the pattern height of the pattern associated with the determined contrast value in the calibration data. The calibration data can be stored by the device, such as in memory connected to the processor, or it can be retrieved by the device on demand. The calibration data may include a lookup table in which the contrast value and pattern height are associated. The calibration data may also include one or more calibration curves as described below.

[0012] The SEM can be a conventional SEM, which can operate under the control of a processor and / or device.

[0013] In one implementation of the device, the processor is configured to determine the contrast value based on the maximum and minimum intensity in the acquired SEM image.

[0014] In one implementation of this device, the contrast value is determined as follows:

[0015]

[0016] Where I max It is the maximum intensity in the obtained SEM image, while I min It is the minimum strength.

[0017] This allows for precise determination of contrast values ​​and corresponding pattern heights.

[0018] In one implementation of the device, the processor is configured to further determine the pattern height based on the nominal film thickness of the resist film.

[0019] The nominal film thickness, which is the target thickness of the resist film when it is formed (e.g., by coating or deposition), is a parameter that affects the contrast value for a given pattern height. Therefore, the device is advantageously adapted to take this nominal film thickness into account, meaning that calibration data can depend on the nominal film thickness.

[0020] In one implementation of the device, the processor is configured to further determine the pattern height based on the type of resist film.

[0021] The type of film, such as the material of the resist film and / or the material of the underlying layer on which the resist film is provided, is a parameter that affects the contrast value for a given pattern height. Therefore, the device is advantageously adapted to take this film type into account, meaning that calibration data can be dependent on the film type.

[0022] In one implementation of this device, the nominal thickness of the resist film is in the range of 5-50 nm; and / or the pattern height is in the range of 1-25 nm.

[0023] In one implementation of this device, the resist film is of either spin-coated glass (SOG) type or carbon substrate type.

[0024] In one implementation of the device, the calibration data includes calibration datasets for each of one or more nominal membrane thicknesses and / or one or more membrane types.

[0025] In one implementation of the device, each calibration dataset includes a calibration curve that indicates the relationship between a plurality of predetermined contrast values ​​and a plurality of predicted patterns.

[0026] In one implementation of the device, the pattern height of the predicted quantity in the calibration dataset is based on atomic force microscopy (AFM) measurements.

[0027] In one implementation of the device, the processor is further configured to: obtain multiple SEM images of a pattern from a SEM, wherein each SEM image is associated with one of multiple realizations or portions of the pattern; determine a corresponding contrast value associated with the pattern based on each of the multiple SEM images; and determine the pattern height of the pattern based on calibration data and an average contrast value calculated from the corresponding contrast values.

[0028] In one implementation of the device, the device is configured to control the SEM to scan an electron beam across a pattern to obtain an SEM image; and / or the device includes or is contained within an SEM.

[0029] Specifically, the processor can be configured to control the SEM. The processor can be one or more processors of the SEM.

[0030] A second aspect of this disclosure provides a method for determining the pattern height of a pattern produced in a resist film by EUV lithography, the method comprising: obtaining a SEM image of the pattern from a SEM; determining a contrast value associated with the pattern based on the obtained SEM image; and determining the pattern height based on calibration data and the determined contrast value.

[0031] In one implementation of the method, the method includes determining a contrast value based on the maximum and minimum intensities in the obtained SEM image.

[0032] In one implementation of this method, the contrast value is determined as follows:

[0033]

[0034] Where I max It is the maximum intensity in the obtained SEM image, while I min It is the minimum strength.

[0035] In one implementation of the method, the method includes further determining the pattern height based on the nominal film thickness of the resist film.

[0036] In one implementation of the method, the method includes further determining the pattern height based on the type of the resist film.

[0037] In one implementation of this method, the nominal thickness of the resist film is in the range of 5-50 nm; and / or the pattern height is in the range of 1-25 nm.

[0038] In one implementation of this method, the resist film is either a spin-coated glass type or a carbon substrate type.

[0039] In one implementation of this method, the calibration data includes a calibration dataset for each of one or more nominal membrane thicknesses and / or one or more membrane types.

[0040] In one implementation of the method, each calibration dataset includes a calibration curve indicating the relationship between a plurality of predetermined contrast values ​​and a plurality of predicted patterns.

[0041] In one implementation of this method, the pattern height of the predicted quantities in the calibration dataset is based on atomic force microscopy (AFM) measurements.

[0042] In one implementation of the method, the method includes: obtaining a plurality of SEM images of a pattern from a SEM, wherein each SEM image is associated with one of a plurality of realizations or portions of the pattern; determining a corresponding contrast value associated with the pattern based on each of the plurality of SEM images; and determining the pattern height of the pattern based on calibration data and an average contrast value calculated from the corresponding contrast values.

[0043] In one implementation of the method, the method includes controlling the SEM to scan an electron beam across a pattern to obtain an SEM image.

[0044] The method of the second aspect and its implementations achieve the same advantages as those described for the device and its corresponding implementation for the first aspect.

[0045] In a further implementation of the method, the method further includes constructing calibration data based on one or more corresponding calibration contrast values ​​obtained for one or more corresponding test patterns, wherein each corresponding calibration contrast value is determined based on one or more SEM images of one of the corresponding test patterns and AFM height measurements of the test pattern.

[0046] The calibration data can be constructed by the device of the first party, or it can be constructed by another device.

[0047] A third aspect of this disclosure provides a computer program including program code that, when executed by a processor, performs any of the methods or implementations thereof according to the second aspect.

[0048] Specifically, the processor may be the processor of the device of the first aspect and / or the processor of the SEM. The program code may be stored in the memory of at least one of the device of the first aspect, the processor, and the SEM. The program code may include instructions for performing the method. Attached Figure Description

[0049] The above aspects and implementations are explained in the following specific embodiments with reference to the accompanying drawings:

[0050] Figure 1 An apparatus according to an embodiment of the present disclosure is shown.

[0051] Figure 2 The calibration curve of an SOG-type resist film is shown, i.e., the resist film is set on an SOG substrate.

[0052] Figure 3 The calibration curves of a carbon-based resist film are shown, i.e., the resist film (with...) Figure 2The same) is set on the carbon substrate (UL).

[0053] Figure 4 Multiple SEM images taken for different membrane types (SOG, UL) and different nominal membrane thicknesses (FT) are shown.

[0054] Figure 5 Methods for determining contrast values ​​are shown, particularly based on the determination of gray-level pair positions in SEM images, and for different FTs.

[0055] Figure 6 A method according to an embodiment of this disclosure is shown. Detailed Implementation

[0056] Figure 1 An apparatus 10 according to an embodiment of the present disclosure is shown. The apparatus 10 is configured to determine the pattern height of a pattern 13. The pattern 13 is formed in a resist film, specifically in a resist film 14 by EUV lithography. The resist film 14 may be a resist material layer suitable for EUV (conventional materials may be used). The resist material layer may be provided on an underlying layer of a particular material, as described below. However, the apparatus 10 is also capable of determining the pattern height of patterns in the resist film 14 that are not formed by EUV but, for example, by another lithography technique. The apparatus 10 is particularly capable of determining small pattern heights in the resist film 14 having a small nominal FT (where nominal FT refers to the target thickness of the resist film 14 before it is patterned by lithography). For example, the nominal FT of the resist film 14 may be in the range of 5-50 nm. Furthermore, the pattern height of the pattern 13 in the resist film 14 may be in the range of 1-25 nm. The pattern height can be a height step between the area of ​​the resist film 14 that is patterned by photolithography (e.g., illuminated with EUV) and the area of ​​the resist film 14 that is not patterned by photolithography (e.g., not illuminated with EUV, for example due to a mask).

[0057] Device 10 includes a processor 11. Processor 11 can be configured to perform, conduct, or initiate various operations of device 10, as described in this disclosure. Processor 11 may include hardware and / or be software-controlled. Hardware may include analog circuit systems or digital circuit systems, or both. Digital circuit systems may include components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors.

[0058] Device 10 may also include a memory circuitry that stores one or more instructions executable by processor 11, specifically under software control. For example, the memory circuitry may include a non-transitory storage medium storing executable software code that, when executed by processor 11, causes various operations of device 10 to be performed.

[0059] In one embodiment, processor 11 includes one or more processing units and non-transitory memory connected to the one or more processing units. The non-transitory memory may carry executable program code that, when executed by the one or more processing units of processor 11, causes device 10 to perform, conduct, or initiate the operations or methods described in this disclosure.

[0060] Specifically, processor 11 is configured to acquire an SEM image 12 of pattern 13 from SEM 15. For example, device 10 can receive SEM image 12 from SEM 15 upon request. For this purpose, a wired or wireless connection can exist between device 10 and SEM 15. Device 10 can be configured to control SEM 15 to scan an electron beam across pattern 13 in resist film 14 (e.g., on a wafer or die) to obtain SEM image 12. SEM 15 can then provide SEM image 12 to device 10. Device 10 can also read SEM image 12 from SEM 15 (e.g., dedicated storage). Furthermore, device 10 may also include SEM 15, and processor 11 may use an internal control protocol to control SEM 15. Alternatively, device 10 may be included in SEM 15, and processor 11 may be one of one or more processors of SEM 15 and may be connected to SEM image storage of SEM 15.

[0061] Furthermore, processor 11 is configured to determine a contrast value associated with pattern 13 based on the acquired SEM image 12. Specifically, processor 11 can determine the contrast value from SEM image 12. To do this, processor 11 can be configured to analyze the intensity (intensity value) of the pixels in SEM image 12. For example, processor 11 can be configured to determine the contrast value based on the maximum and minimum intensity in SEM image 12, for example, according to the following formula:

[0062]

[0063] Where I max It is the maximum strength, while I min It is the minimum intensity. The processor 11 can determine the maximum intensity in the SEM image 12, determine the minimum intensity in the SEM image 12, and then calculate the contrast value.

[0064] Furthermore, processor 11 is configured to determine the pattern height based on calibration data 16 and the determined contrast value. Optionally, this determination may be further based on the nominal FT of the resist film 14 and / or further based on the film type of the resist film 14. For example, processor 11 may be configured to retrieve calibration data 16 from the memory of device 10 and may perform a matching process between the determined contrast value and calibration data 16. Calibration data 16 may include one or more calibration curves, each of which may indicate a relationship between a plurality of predetermined contrast values ​​and a plurality of predicted pattern heights. In this case, processor 11 may select one of the calibration curves (e.g., based on the nominal FT and / or film type of the resist film 14 including the pattern 13 imaged by SEM image 12) and may find a predetermined contrast value that matches the determined contrast value determined based on SEM image 12. Processor 11 may then determine the pattern height of pattern 13 as equal to the predicted pattern height, which, for the selected calibration curve, is associated with the predetermined contrast value that matches the determined contrast value.

[0065] Similar to the process described above, processor 11 can also obtain multiple SEM images 12 of pattern 13 from SEM 15 (the aforementioned SEM image 12 may be one of multiple SEM images 12), wherein each SEM image 12 may be associated with one of multiple different implementations or portions of pattern 13. For example, pattern 13 may be implemented on multiple dies (e.g., on the same wafer), wherein the dies are processed in parallel. Each of the multiple SEM images 12 may correspond to one of the multiple dies. Processor 11 may then be configured to determine a corresponding contrast value associated with pattern 13 based on or according to each of the multiple SEM images 12. In other words, processor 11 may obtain multiple contrast values ​​and may also be configured to determine the pattern height of pattern 13 based on calibration data 16 and an average contrast value, wherein processor 11 is configured to determine the average contrast value according to the multiple contrast values.

[0066] The following exemplary embodiments describe a complete method for determining the pattern height of pattern 13 in resist film 14, wherein device 10 and top-down SEM images (e.g., CD-SEM images) are used:

[0067] • Coat one or more calibration wafers with a resist film 14 of the required range of nominal FT (e.g., coat the calibration wafers with resist films 14 having 10, 15, 20, 25 and 30 nm FT respectively).

[0068] • A mask is used to expose the wafer (e.g., using EUV), where at least one test pattern is generated in the resist film 14. This at least one test pattern may be designed to allow subsequent AFM pattern height measurement. One or more SEM images are collected from one or more calibration wafers. Specifically, these are SEM images of one or more dies (e.g., five dies) on the calibration wafer. Thus, the SEM images can be obtained individually at the optimal focus-through dose for the calibration wafer.

[0069] • For all dies and all calibration wafers, calculate the contrast values ​​of the test patterns in the SEM images to obtain one or more calibration contrast values. The number of SEM images may depend on how accurately the contrast values ​​must be determined (e.g., for high accuracy, 50 SEM images per die may be obtained). Each corresponding calibration contrast value can be determined based on the maximum and minimum intensities in the SEM images. For example, each calibration contrast value can be calculated as follows:

[0070]

[0071] Where I max and I min These are the maximum and minimum intensities in the SEM image, respectively.

[0072] • Collect AFM (or other technology) pattern height measurements for the same one or more dies, and calculate calibration contrast values ​​for these measurements to obtain the predicted pattern height.

[0073] • Construct one or more calibration curves (each calibration curve representing a predicted pattern height against a predetermined calibration contrast value). Different calibration curves can be constructed for different nominal FTs and / or different types of resist films. Calibration curves can be collected together to form calibration data16. It is worth noting that a single calibration curve can be applied to the exact same combination of the resist film FT and the underlying substrate used to support the resist film.

[0074] Now, using the device 10 as described above, by using calibration data 16 and based on the SEM image 12 taken from the pattern 13, any mask can be used to further determine the pattern height of any pattern 13 produced in any resist film 14.

[0075] Figure 2 and Figure 3 Two examples of calibration data 16 for the same resist film 14 on different substrates are shown. Specifically, Figure 2 Calibration data 16 is shown for an SOG type resist film 14, i.e., the resist film 14 is disposed on an SOG substrate. Figure 3Calibration data 16 is shown for a carbon substrate type resist film 14, i.e., the resist film 14 is provided on a carbon substrate (specifically, referred to as UL1).

[0076] Figure 2 The calibration data 16 is shown to include multiple calibration datasets 21-24 for different resist films 14 of SOG type, specifically one calibration dataset for each of multiple nominal film thicknesses (15nm, 20nm, 25nm, and 30nm) of the resist film 14. For calibration datasets with lower nominal FT, the contrast values ​​are lower. Furthermore, as... Figure 2 As shown, each calibration dataset 21-24 can be represented as a calibration curve indicating the relationship between several predetermined contrast values ​​('contrast' as normalized values ​​between 0 and 1 on the y-axis) and several predicted pattern heights ('resist array height' in nm on the x-axis). It can be concluded that for each calibration dataset 21-24, a lower contrast value corresponds to a smaller pattern height.

[0077] Figure 3 The calibration data 16 is shown to also include multiple calibration datasets 31-34 for different resist films 14 of type UL1, specifically one calibration dataset for each of multiple nominal film thicknesses (15 nm, 20 nm, 25 nm, and 30 nm) of the resist film 14. In other words, calibration data 16 may include calibration datasets 21-24 and 31-34, i.e., one calibration dataset for each of one or more film types and one or more FTs of one or more resist films 14. Similarly, it can be seen from... Figure 3 It was found that for each calibration dataset 31-34, lower contrast values ​​corresponded to smaller pattern heights.

[0078] Note that in Figure 2 and Figure 3 The study demonstrated that minute changes in pattern height have a significant impact on contrast value, to the extent that they are significant enough to accurately determine the pattern height (and distinguish it from other pattern heights by different contrast values).

[0079] Figure 4 Exemplary SEM images taken for different membrane types (SOG, UL1, and UL2) and different nominal FT values ​​are shown. Specifically, Figure 4 (a) shows different SEM images of the SOG type resist film 14 at different nominal FT (10-30 nm). Figure 4 (b) shows different SEM images of the resist film 14 of carbon-based UL type (UL1) at different nominal FT (10-30 nm). Figure 4(c) Shows different SEM images 12 of different resist film types 14 (SOG, UL1 and another UL type (referred to as UL2)) for the same nominal (or target) resist FT (i.e. 15 nm).

[0080] from Figure 4 It can be concluded that the contrast value of pattern 13 in SEM image 12 depends on the nominal FT (where a lower nominal FT results in a lower contrast value), and further depends on the type of resist film 14 (where SOG results in a lower contrast value than UL1 and UL2 at the same nominal FT). Therefore, device 10 can be configured to further determine the pattern height of pattern 13, which is generated in resist film 14, based on the nominal film thickness and / or film type of resist film 14.

[0081] Figure 5 The diagram illustrates how contrast values ​​can be determined from SEM image 12 for different Fourier Transform (FT) values ​​(here, for example, 11.3 nm, 16.1 nm, 19.4 nm, and 20.6 nm). It can be seen that the gray levels (8 bits, on the y-axis) of SEM image 12 follow a pattern 13 generated in the resist film 14 (i.e., at different locations on the resist film 14, the gray levels are different due to pattern 13 and exhibit periodic behavior). The variation in gray levels is particularly pronounced for higher nominal FTs. From these gray levels, contrast values ​​can be derived, for example, based on the maximum and minimum intensities (related to the gray level) as described above.

[0082] Figure 6 A method 60 according to an embodiment of this disclosure is illustrated. Method 60 can be used to determine the pattern height of a pattern 13 produced by EUV lithography in a resist film 14. Method 60 can be derived from, for example... Figure 1 The device 10 shown and described above is used to perform this action.

[0083] Method 60 includes step 61 of obtaining an SEM image 12 of pattern 13 from SEM 15. Method 60 also includes step 62 of determining a contrast value associated with pattern 13 based on the obtained SEM image 12. Subsequently, method 60 includes step 63 of determining the pattern height of pattern 13 based on calibration data 16 (e.g., as described above and constructed above) and based on the determined contrast value.

[0084] In summary, embodiments of this disclosure achieve at least the following advantages: It enables the determination of the pattern height of any pattern 13 in the resist film 14 via SEM 15. Specifically, it uses EUV-generated patterns 13, which are particularly generated in thin resist films 14 (e.g., below 100 nm, even 50 nm, or less). Once calibration data 16 (e.g., calibration curves) is generated, any SEM image 12 can be determined by contrast analysis related to the pattern height, for example, by contrast analysis performed by the device 10 described in this disclosure.

Claims

1. An apparatus (10) for determining the pattern height of a pattern (13) produced in a resist film (14) by extreme ultraviolet (EUV) lithography, the apparatus (10) comprising a processor (11) configured to: SEM image (12) of the pattern (13) was obtained from scanning electron microscope (SEM) (15); The contrast value associated with the pattern (13) is determined based on the obtained SEM image (12); and The pattern height is determined based on the calibration data (16) and the determined contrast value.

2. The device (10) according to claim 1, characterized in that, The processor (11) is configured to determine the contrast value based on the maximum and minimum intensity in the obtained SEM image (12).

3. The device (10) according to claim 2, characterized in that, The contrast value is determined as follows: Where I max It is the maximum intensity in the obtained SEM image (12), while I min It is the minimum strength.

4. The device (10) according to any one of claims 1 to 3, characterized in that, The processor (11) is configured to further determine the pattern height based on the nominal film thickness of the resist film (14).

5. The device (10) according to any one of claims 1 to 3, characterized in that, The processor (11) is configured to further determine the pattern height based on the film type of the resist film (14).

6. The device (10) according to any one of claims 1 to 3, characterized in that: The nominal thickness of the resist film (14) is in the range of 5-50 nm; and / or The pattern height is in the range of 1-25 nm.

7. The device (10) according to any one of claims 1 to 3, characterized in that, The resist film (14) is of either spin-coated glass type or carbon substrate type.

8. The device (10) according to any one of claims 1 to 3, characterized in that, The calibration data (16) includes calibration datasets (21-24, 31-34) for each of one or more nominal membrane thicknesses and / or one or more membrane types.

9. The device (10) according to claim 8, characterized in that, Each calibration dataset (21-24, 31-34) includes calibration curves that indicate the relationship between multiple predetermined contrast values ​​and multiple predicted patterns.

10. The device (10) according to claim 9, characterized in that, The pattern height of the predicted quantities in the calibration dataset (21-24, 31-34) is based on atomic force microscopy (AFM) measurements.

11. The device (10) according to any one of claims 1 to 3, characterized in that, The processor (11) is configured to: Multiple SEM images (12) of the pattern (13) are obtained from the SEM (15), wherein each SEM image (12) is associated with one of multiple implementations or portions of the pattern (13); A corresponding contrast value associated with the pattern (13) is determined based on each of the plurality of SEM images (12); as well as The pattern height of the pattern (13) is determined based on the calibration data (16) and the average contrast value calculated from the corresponding contrast value.

12. The device (10) according to any one of claims 1 to 3, characterized in that: The device (10) is configured to control the SEM (15) to scan an electron beam across the pattern (13) to obtain the SEM image (12); and / or The device (10) includes the SEM (15) or is included in the SEM (15).

13. A method (60) for determining the pattern height of a pattern (13) produced in a resist film (14) by extreme ultraviolet (EUV) lithography, the method (60) comprising: (61) SEM image (12) of the pattern (13) was obtained from scanning electron microscope (SEM) (15). The contrast value associated with the pattern (13) is determined (62) based on the obtained SEM image (12); as well as The pattern height (63) is determined based on the calibration data (16) and the determined contrast value.

14. The method (60) according to claim 13, characterized in that, Also includes: The calibration data (16) is constructed based on one or more corresponding calibration contrast values ​​obtained for one or more corresponding test patterns. Each corresponding calibration contrast value is determined based on one or more SEM images (12) of one of the corresponding test patterns and the AFM height measurement of that test pattern.

15. A computer program product comprising program code, which, when executed by a processor (11), is used to perform the method (60) according to claim 13.

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