We have developed a high-resolution x-ray microscope with spatial resolution better than 100 nm. The utilized x-ray energy of the microscope is 17.5 keV that can penetrate through standard silicon substrate and enables to observe embedded nanoscale metal structure and defects, nondestructively. We have applied the present x-ray microscope for investigating 3D flash memory devices and observed precise metal filling structure in there. In addition, defects in the circuit area were also found.
KEYWORDS: Tin, X-rays, Scattering, Transmission electron microscopy, Semiconducting wafers, 3D modeling, X-ray detectors, 3D metrology, Silicon, Film thickness
We have evaluated two types of high aspect ratio (HAR) structures of semiconductor memory devices by adopting small-angle x-ray scattering in transmission geometry (T-SAXS). One is the thin TiN thickness on the sidewall of 1.4 μm deep holes. The results indicate that T-SAXS is capable of determining sidewall thickness profiles with sub-nanometer accuracy. The other is the precise three-dimensional shape of 4.2 μm deep holes. The results show that the shape of the hole cross-section parallel to the sample surface changes drastically in the depth direction. These evaluation results of the two structures are consistent with that of transmission electron microscope, respectively.
An etching process for high-aspect ratio (HAR) structure is one of key technologies in the recent semiconductor device fabrication. In the development and control of etching processes, it is very critical to evaluate depth, shape profile, and tilting. Critical dimension small angle X-ray scattering (CD-SAXS) is a powerful measurement technique to characterize such shape parameters of HAR structures. In this paper, we evaluated the measurement sensitivity of CD-SAXS for changing shape parameters (average CD, depth, side wall shape, tilting) of HAR holes using simulation results. The simulation results show that CD-SAXS has sufficient sensitivity to characterize shape parameters of HAR structures. We also demonstrated the performance of CD-SAXS by measurement of 1μm depth holes on the 300 mm wafer. As a result, we were able to obtain detailed hole profiles, distribution of average CD and tilt angle across the entire wafer.
A wavefront measurement method in the microscope (magnifying) geometry can help achieve the required high accuracy for deformable mirrors. This study proposes an image-based wavefront measurement method based on a series of images of a small area near the focus. In this method, phase retrieval calculation using multiple images is performed. A proof-of-concept experiment was performed using multilayer AKB mirrors and an FZP to form the small area. Consequently, wavefront aberration was successfully retrieved using 60 images of a 30-nm-diameter area near the focus.
Nanoimprint lithography (NIL) is one of the highest potential candidates for next generation lithography (NGL) in semiconductors. NIL is very useful technology for fine pattern fabrications compared to conventional optical lithography. NIL technology makes use of replication from quartz templates. The cross-sectional profile of the template is directly transferred to the resist profile on a wafer. In relationship to that, the management of cross-sectional profile in quartz templates is needed much more than that of photomask.
In our past reports, we had studied the performance of measuring cross-sectional profiles using grazing-incidence small-angle X-ray scattering (GISAXS). GISAXS has made it possible to analyze the periodic nanostructure patterns using 2D scattering X-ray intensity distribution. After much research we had found the application to not only sub-20nm hp lines-and-spaces(LS) patterns but also hole patterns was very effective.
We have been developing templates for more scaling, “sub-15nm” by applying Self-Aligned Double Patterning (SADP). We showed the specific issues in SADP and the solution for quality assuranc In this report, we demonstrate the capabilities of measuring the cross-sectional profiles for sub-15 nm patterns using GISAXS. Taking into complicated periodic structures of SADP, we optimize the structural models to meet the demands. This report reveals GISAXS technique has potential for the sub-15nm metrology.
Spatial resolution of full-field X-ray microscopes based on total-reflection mirrors was limited by grazing-incidence angle of the mirrors. At practical conditions, achievable spatial resolution is approximately 30 nm. To overcome the limitation, multilayer advanced Kirkpatrick-Baez mirrors and full-field X-ray microscopes with this objective mirrors have been developed in Osaka University and RIGAKU Corp. One of the remarkable points in this design is an achievable spatial resolution of less than 20 nm owing to large grazing-incidence angle and multilayer (Pt/C) with narrow period. Also, the advanced Kirkpatrick-Baez mirrors comprise two mirror pairs based on the Wolter type I and type III optics, respectively, to have sufficiently large magnification even at a compact setup with the whole length of 2 m (between a sample and a camera). The compactness makes it possible to apply the optics to laboratory-based X-ray microscopes, which is another ongoing project.
A performance test using a Siemens star chart at an X-ray energy of 8 keV was performed in SPring-8 BL29XUL. The results showed lines with approximately 30-nm width could be resolved. Also, tests of stability and energy dependence confirmed usability of this system.
Nanoimprint lithography (NIL) is one of the highest potential candidates for next generation lithography (NGL) in semiconductors[1][2]. NIL is very useful technology for pattern fabrication in high resolutions and low costs compared to conventional optical lithography[3]. NIL technology makes use of replication from quartz templates. The cross-sectional profile of the template is directly transferred to the resist profile on a wafer. In relationship to that, the management of the cross-sectional profile on the template pattern is much more important than that of photomask[4]. In our past reports, we had studied the performance of measuring cross-sectional profiles using grazing-incidence small-angle X-ray scattering (GISAXS). GISAXS has made it possible to analyze the repeated nanostructure patterns with a 2D X-ray scattering pattern. After much research, we have found the application is very effective using the method of cross-sectional profiling in sub-20 nm half-pitch lines-and-spaces (LS) patterns[5] and additionally in hole patterns[6]. However, regarding the measurement for hole patterns, around a few hours are needed to get one result. We have considered new method for measuring cross-sectional profiles of hole patterns with GISAXS to improve the measurement throughput. We propose the new method to combine GISAXS with SEM images for measuring crosssectional profiles of hole patterns. Using this new method, measurement throughput is achieved less than one hour while almost the same accuracy as the conventional method. We report the results of the cross-sectional profile measurement of hole patterns with new method in comparison to conventional method.
Nanoimprint lithography (NIL) is one of the highest potential candidates for next generation lithography in
semiconductors. NIL is very useful technology for pattern fabrication in high resolution compared to conventional
optical lithography. NIL technology makes use of replication from quartz templates. The cross-sectional profile of the
template is directly transferred to the resist profile on a wafer. Accordingly, the management of the cross-sectional
profile on the template pattern is much more important than on each photomask.
In our previous report, we had studied the performance of measuring cross-sectional profiles using grazing-incidence
small-angle X-ray scattering (GISAXS). GISAXS has made it possible to analyze the repeated nanostructure patterns
with a 2D X-ray scattering pattern. After various researches, we found the application is very effective in the method of
cross-sectional profiling of sub-20 nm half-pitch lines-and-spaces (LS) patterns.
In this report, we investigated the capabilities of measuring cross-sectional profiles for hole patterns using GISAXS.
Since the pattern density of hole patterns is much lower than that of LS patterns, the intensity of X-ray scattering in hole
measurements is much lower. We optimized some measurement conditions to build the hole measurement system.
Finally, the results suggested that 3D profile measurement of hole pattern using GISAXS has sufficient performance to
manage the cross-sectional profile of template. The measurement system using GISAXS for measuring 3D profiles
establishes the cross-sectional profile management essential for the production of high quality quartz hole templates.
KEYWORDS: Nanoimprint lithography, X-rays, Scattering, Quartz, 3D metrology, Scanning electron microscopy, Transmission electron microscopy, Nanostructures, Critical dimension metrology, 3D modeling
Nanoimprint lithography (NIL) is one of the highest potential candidates for next generation lithography in
semiconductors. NIL is very useful technology for pattern fabrication in high resolution compared to conventional
optical lithography. NIL technology makes use of replication from quartz templates. The cross-sectional profile of the
template is directly transferred to the resist profile on a wafer. Accordingly, the management of the cross-sectional
profile on the template pattern is much more important than on each photomask.
In our previous report, we had studied the performance of measuring cross-sectional profiles using grazing-incidence
small-angle X-ray scattering (GISAXS). GISAXS has made it possible to analyze the repeated nanostructure patterns
with a 2D X-ray scattering pattern. After various researches, we found the application is very effective in the method of
cross-sectional profiling of sub-20 nm half-pitch lines-and-spaces (LS) patterns.
In this report, we investigated the capabilities of measuring cross-sectional profiles for hole patterns using GISAXS.
Since the pattern density of hole patterns is much lower than that of LS patterns, the intensity of X-ray scattering in hole
measurements is much lower. We optimized some measurement conditions to build the hole measurement system.
Finally, the results suggested that 3D profile measurement of hole pattern using GISAXS has sufficient performance to
manage the cross-sectional profile of template. The measurement system using GISAXS for measuring 3D profiles
establishes the cross-sectional profile management essential for the production of high quality quartz hole templates.
Nanoimprint lithography (NIL) is one of the most potential candidates for the next generation lithography for semiconductor. It will achieve the lithography with high resolution and low cost.
High resolution of NIL will be determined by a high definition template. Nanoimprint lithography will faithfully transfer the pattern of NIL template to the wafer. Cross-sectional profile of the template pattern will greatly affect the resist profile on the wafer. Therefore, the management of the cross-sectional profile is essential.
Grazing incidence small angle x-ray scattering (GI-SAXS) technique has been proposed as one of the method for measuring cross-sectional profile of periodic nanostructure pattern. Incident x-rays are irradiated to the sample surface with very low glancing angle. It is close to the critical angle of the total reflection of the x-ray. The scattered x-rays from the surface structure are detected on a two-dimensional detector. The observed intensity is discrete in the horizontal (2θ) direction. It is due to the periodicity of the structure, and diffraction is observed only when the diffraction condition is satisfied. In the vertical (β) direction, the diffraction intensity pattern shows interference fringes reflected to height and shape of the structure. Features of the measurement using x-ray are that the optical constant for the materials are well known, and it is possible to calculate a specific diffraction intensity pattern based on a certain model of the cross-sectional profile. The surface structure is estimated by to collate the calculated diffraction intensity pattern that sequentially while changing the model parameters with the measured diffraction intensity pattern. Furthermore, GI-SAXS technique can be measured an object in a non-destructive. It suggests the potential to be an effective tool for product quality assurance. We have developed a cross-sectional profile measurement of quartz template pattern using GI-SAXS technique. In this report, we will report the measurement capabilities of GI-SAXS technique as a cross-sectional profile measurement tool of NIL quartz template pattern.
Critical dimension small-angle x-ray scattering (CD-SAXS) with a grazing-incidence geometry, which was recently developed by the authors, has been successfully applied to the cross-sectional profile measurements of different types of L/S- and hole-type patterns on photoresist surfaces. We have calculated diffraction intensities from the nanostructures based on a distorted wave Born approximation method to take the refraction and the reflection at the interfaces between layers into account, and the average cross-sectional profiles have been analyzed by a model-based least-square method. From the precise analyses, slight cross-sectional profile differences of a few nanometers scale generated by using different material and exposure conditions have been identified. The obtained cross-sectional profiles showed good agreements with the results obtained by cross-sectional scanning electron microscopy (SEM). These results demonstrate the applicability of the CD-SAXS to the nanoscale structural metrology. It is expected that the CD-SAXS is also applicable to even smaller scale structures, e.g., those of EUV, NIL, or DSA, as the x-ray wavelength is well shorter than the critical lengths of these structures.
We have developed high-resolution grazing incidence x-ray diffraction (HRGIXD) pitch calibration system with
wavelength of 0.1540593 nm (Cu K α1 line). In order to ensure accuracy of this calibration system, we measured average
pitch of a 100-nm pitch grating reference, which is being used for magnification calibration of a current critical-dimension
scanning electron microscope (CD-SEM), and compared with the results of deep ultra violet (DUV) laser
diffraction pitch calibration system with wavelength of 193 nm. The average pitch determined by the HRGIXD system
agrees with that determined by the DUV laser diffraction system within the range of uncertainty. We measured average
pitch of a fine 25-nm pitch grating, which will be used for magnification reference. In the DUV laser diffraction,
wavelength of 193 nm no longer satisfies diffraction condition for the 25-nm pitch grating, because wavelength must be
shorter than twice of the pitch size. On the other hand, wavelength of x-ray is much shorter than the pitch size. We have
successfully detected more than ten sharp diffraction peaks corresponding to the 25-nm period. The average pitch of the
grating is measured in very high-accuracy with standard uncertainty of less than 10 pm.
We have developed a new x-ray metrology for measuring surface periodic grating of semiconductor device pattern. X-rays irradiate surface of the device area with a shallow glancing angle, which is close to the critical angle of total external reflection of the surface material. The measured x-ray diffraction pattern is reflected to the average cross-sectional profile of the grating. The pattern made from SiO2 on Si with100 nm-pitch is analyzed by the present x-ray metrology. The obtained profile, for example, line width, height of the grating and so on are well agreed with that
observed by cross-sectional transmission electron microscopy. The wavelength of x-ray that we use is 0.154093 nm and it is enough shorter than the critical length of the grating structure, even when the line width becomes 10 nm or less. Therefore, the resolution of the x-ray metrology will be maintained good enough for the analysis that will be required in the future. In addition, x-ray metrology can be measure the cross-sectional profile with nondestructively due to hightransmissivity of x-rays for the materials. Furthermore, the optical parameter of the materials for x-ray is well established, therefore, x-ray metrology is applicable for any materials of device patterns without uncertain empirical parameters.
Grazing incidence small-angle x-ray scattering (GISAXS) is proposed as one of the candidates for characterizing cross
section of nanostructure line grating pattern. GISAXS is expected as useful nondestructive tool for characterizing cross
section. We developed GISAXS and evaluated the capability using the 4X nm resist line patterns and the 3X nm silicon
gate line patterns. The GISAXS results are compared with TEM images to evaluate the reconstruction ability in cross
section contour profile. The correlation is investigated between GISAXS and the reference tools such as CD-SEM and
TEM in the values of CD, height and bottom corner radius. The static repeatability is also evaluated by performing measurement ten times. We report the results of GISAXS capability as cross sectional metrology tool in actual device of 4X and 3X generation.
We have developed a new x-ay metrology for profiling surface periodic structure of discrete track patterned
media. X-rays irradiate surface of the discrete track media with a shallow glancing angle, which is close to the critical
angle of total external reflection of the surface material. The measured x-ray scattering pattern is reflected to the average
cross-sectional profile of the grating. Resist pattern of circular discrete track with120 nm-pitch on 65 mmφ magnetic disc
is analyzed by the present x-ray metrology. The obtained profile, for example, line width, height of the track and so on
are well agreed with that observed by cross-sectional scanning electron microscopy. The wavelength of x-ray that we use
is 0.154093 nm and it is enough shorter than the critical length of the grating structure, even when the track width
becomes 10 nm or less. Therefore, the resolution of the x-ray metrology will be maintained well that of required in
future. In addition, x-ray metrology is able to profiling the cross-sectional structure with nondestructively due to hightransmissivity
of x-rays for the materials. Furthermore, the optical parameter of the materials is well established in x-ray
region, therefore, it is applicable not only resist patterns, but also real device patterns only with certain physical/optical
parameters.
For the rapid structural characterization of combinatorial epitaxial thin films, we developed an X-ray diffraction system. A convergent X-ray beam from a curved crystal monochromator is focused on sample surface about 0.1 mm X 10 mm in size. Diffraction patterns of this area are simultaneously observed on the 2D detector within a few degree. Thus, rocking curve profiles of combinatorial epitaxial thin films for one-column pixels can be measured rapidly with Bragg peak of substrate; the measurement time depends on the film thickness, but the most cases are within one minute.
The film thickness estimation is one of most important subject for the design up of photomask blanks. For control of photomask specifications, the thickness measurement technology is the key of well-designed photomask blanks. The grazing- incidence X-ray reflectivity technology is very useful in order to measure thickness, density and interface roughness of photomask blank. In this paper, we reported the adaptation of the X-ray reflectivity technology to photomask evaluation. A Cr and ZrSi oxide thin photomask blanks were prepared with DC sputtering method. The X-ray reflectivities of those photomask blanks were measured with RIGAKU ATX-E diffractometer system. The thicknesses and densities of the photomask blanks were calculated with RIGAKU XDD degree(s) program. The coincidence between the calculated X-ray reflectivity curves with surface modified model which was defined with a surface oxidized layer is better than the calculated results without a surface oxidized layer. These results indicate that the photomask blanks have a surface oxidized layer. Thicknesses of the same position with same films were measured by ordinary technologies, for example, microscopic observation and thickness measurement technologies. The accuracy of those layer parameters which were calculated with X-ray reflectivity curves were better than those parameters measured with other microscopic and thickness measurement technologies.
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