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Polyamines are aliphatic hydrocarbons with terminal amino groups and are essential for biological activities. It has been reported that polyamines have health-promoting effects in animals, such as the extension of lifespan by polyamine intake. The identification of a high polyamine-producing bacterium from foods could lead to the development of a novel probiotic candidate. We aimed to identify high polyamine-producing bacteria from food, and isolated and collected bacteria from vegetables and fermented foods produced in Japan. We successfully acquired

Force measurement using zero-compliance mechanism is proposed and studied experimentally. A zero-compliance mechanism is composed of two suspensions connected in series; one of them is operated to ...

In the next generation SAOP (Self-aligned Octuplet patterning) process, the line width and LWR (Line Width Roughness) measurement of lines with sub-10 nm is required. We have already proposed a novel method of line width and LWR measurement with sub-nanometer uncertainty by using FIB (Focused Ion Beam) processing, and TEM (Transmission Electron Microscope) images as reference metrology. In the previous report, we applied the method to SAQP features. A specimen of the SAQP FinFET line and space device is coated with carbon and cut horizontally into a thin planar sample by the FIB sampling system. The thin sample is observed by using planar-TEM. The average PSD of LWR of SAQP FinFET sample at the upper and lower positions calculated from planar-TEM images. In this article, we apply the methodology to line width and roughness measurement of advanced features by SAOP process. The features are vertically or horizontally sliced as a thin specimen by FIB micro sampling system. LWR is calculated from the edges positions, and PSD (Power Spectrum Density) is analyzed for the reference metrology.

We have previously demonstrated our method to obtain unbias dense line’s LER (Line Edge Roughness) processed by EUV (Extreme Ultra-Violet) lithography. No special edge-detection, simulation modeling, beam-scan, nor image processing is required, except optimization of beam-dose parameters. For instance, threshold method that is a conventional edge-detection is used on SEM (Scanning Electron Microscopy) image taken by a conventional beam-scanning with a conventionally used beam-conditions. However, especially for EUV-lithographed features we must determine carefully landing voltage and beam-dose that cause artificial reduction of LER and LWR (Line Width Roughness) due to shrink of photo resist materials. Note that we made edge-detection interval at every 5 nm, that is as small as probe-beam diameter. For instance, we set the vertical magnification, the pixel-density, and the sum-line-per-point parameter at 52.7k, 1024, and 2, respectively. Although we can make the interval as small as sub-nanometer, it is not reliable to measure the sub-nanometer object that is only one-tenth of the probe-beam diameter. Then, we verified accuracy of our unbiased LWR by using two independent experimental methods: TEM and FIB-SEM. We obtained spectra of PSD (Power Spectrum Density) from the TEM, the FIB-SEM and our unbiassing CDSEM-method. We found the three PSDs agreed very well to each others. This result strongly implies that three independent methods measured an identical PSD, of true LWR. By our unbiassing CDSEM-method we can measure the true LWR which is calculated from the true PSD. In this work, by using the similar experimental-methods we verify accuracy of our wiggling measurement. Wiggling is a hot issue in production yield of post dry-etch process. Especially about 20 nm or less in the line-width, wiggling starts appearing due to decreased elastic-stiffness of the line feature. A reason why we study the accuracy of LER, LWR, and wiggling is inline monitor of stochastic failures. As they increase significantly in EUV lithography process, production yield may not be promising. Bisshop et al. [1] investigated pitch and/or space-width correlate to incidence of stochastic-failures, such as breaking-line and bridging-line, down to ppm (parts per million). However, the incidence of the stochastic failures should be reduced less to ppb (parts per billion) or ppt (parts per trillion) which is as small as tolerable particle contamination on a wafer. This implies significance of accurate LWR and/or wiggling monitor because in narrow line or space a-few-nanometer-LWR narrows locally them the more and causes the more stochastic failures. In this work, in order to control ppb-stochastic failures we figure out a correlation between LWR and the failures’ incidence. We need to measure billions of features, that requires too long measurement time for practical process-monitor. To shorten the measurement time we test an effective method to estimate such very few number of failures. Reference [1] Stochastic effects in EUV lithography: random, local CD variability, and printing failures, Peter De Bisschop, J. of Micro/Nanolithography, MEMS, and MOEMS, 16(4), 041013 (2017).

A 1,4-addition strategy using an enone and a copper reagent was studied for the synthesis of (-)-piperitylmagnolol. A MOM-protected biphenol copper reagent was added to BF3·OEt2-activated 4-isopropylcyclohexenone, whereas 1,4-addition of protected monophenol reagents possessing an allyl group was found to be unsuccessful. The allyl group was later attached to the p-,p'-diiodo-biphenol ring by Pd-catalyzed coupling with allylborate. The aforementioned iodide was synthesized using a new method for ortho-selective deiodination of o-,p-diiodophenols.

LER (Line Edge Roughness) and LWR (Line Width Roughness) of the semiconductor device are an important evaluation scale of the performance of the device. Conventionally, LER and LWR is evaluated from CD-SEM (Critical Dimension Scanning Electron Microscope) images. However, CD-SEM measurement has a problem that high frequency random noise is large, and resolution is not sufficiently high. For random noise of CD-SEM measurement, some techniques are proposed. In these methods, it is necessary to set parameters for model and processing, and it is necessary to verify the correctness of these parameters using reference metrology. We have already proposed a novel reference metrology using FIB (Focused Ion Beam) process and planar-TEM (Transmission Electron Microscope) method. In this study, we applied the proposed method to three new samples such as SAQP (Self-Aligned Quadruple Patterning) FinFET device, EUV (Extreme Ultraviolet Lithography) conventional resist, and EUV new material resist. LWR and PSD (Power Spectral Density) of LWR are calculated from the edge positions on planar-TEM images. We confirmed that LWR and PSD of LWR can be measured with high accuracy and evaluated the difference by the proposed method. Furthermore, from comparisons with PSD of the same sample by CD-SEM, the validity of measurement of PSD and LWR by CD-SEM can be verified.

A new metrology method of quantitatively measuring wiggling patterns in a Self-Aligned Double Patterning (SADP) process for 2D NAND technology has been developed with a CD-SEM metrology program on images from a Review-SEM system. The metrology program provided accurate modeling of various wiggling patterns. The Review-SEM system provided a-few-micrometer-wide Field of View (FOV), which exceeds precision-guaranteed FOV of a conventional CD-SEM. The result has been effectively verified by visual inspection on vertically compressed images compared with Wiggling Index from this new method. A best-known method (BKM) system has been developed with connected HW and SW to automatically measure wiggling patterns.

Measurement of line edge roughness (LER) is discussed from four aspects: edge detection, PSD prediction, sampling strategy, and noise mitigation, and general guidelines and practical solutions for LER measurement today are introduced. Advanced edge detection algorithms such as wave-matching method are shown effective for robustly detecting edges from low SNR images, while conventional algorithm with weak filtering is still effective in suppressing SEM noise and aliasing. Advanced PSD prediction method such as multi-taper method is effective in suppressing sampling noise within a line edge to analyze, while number of lines is still required for suppressing line to line variation. Two types of SEM noise mitigation methods, "apparent noise floor" subtraction method and LER-noise decomposition using regression analysis are verified to successfully mitigate SEM noise from PSD curves. These results are extended to LCDU measurement to clarify the impact of SEM noise and sampling noise on LCDU.

For EUV lithography features we want to decrease the dose and/or energy of CD-SEM’s probe beam because LER decreases with severe resist-material’s shrink. Under such conditions, however, measured LER increases from true LER, due to LER bias that is fake LER caused by random noise in SEM image. A gap error occurs between the right and the left LERs. In this work we propose new procedures to obtain true LER by excluding the LER bias from the measured LER. To verify it we propose a LER’s reference-metrology using TEM.

The addition of MeLi to boron enolates produced by the 1,4-addition of Ar2Cu(CN)Li2 to BF3·OEt2-activated enones was followed by the reaction with ClP(O)(OEt)2 to afford the corresponding enol phosphates in moderate to good yields. The scope of this method was examined with sterically hindered or electronically biased enones and/or reagents. This activation of boron enolates was successfully applied to the synthesis of the methyl ether of Δ(9)-tetrahydrocannabinol.

A novel method of sub-nanometer uncertainty for the 3D-profile measurement and LWR (Line Width Roughness) measurement by using FIB (Focused Ion Beam) processing, and TEM (Transmission Electron Microscope) and CD-SEM (Critical Dimension Scanning Electron Microscope) images measurement is proposed to standardize 3D-profile measurement through reference metrology. In this article, we apply the methodology to line profile measurements and roughness measurement of advanced FinFET (Fin-shaped Field-Effect Transistor) features. The FinFET features are horizontally sliced as a thin specimen by FIB micro sampling system. Horizontally images of the specimens are obtained then by a planar TEM. LWR is calculated from the edges positions on TEM images. Moreover, we already have demonstrated the novel on-wafer 3D-profile metrology as "FIB-to-CDSEM method" with FIB slope cut and CD-SEM measuring. Using the method, a few micrometers wide on a wafer is coated and cut by 45-degree slope using FIB tool. Then, the wafer is transferred to CD-SEM to measure the cross section image by top down CD-SEM measurement. We applied FIB-to-CDSEM method to a CMOS image sensor feature. The 45-degree slope cut surface is observed using AFM. The surface profile of slope cut surface and line profiles are analyzed for improving the accuracy of FIB-to-CDSEM method.

A method of sub-nanometer uncertainty for the 3D-profile measurement using TEM (Transmission Electron Microscope) images is proposed to standardize 3D-profile measurement through reference metrology. The proposed method has been validated for profiles of Si lines, photoresist features and advanced-FinFET (Fin-shaped Field-Effect Transistor) features in our previous investigations. However, efficiency of 3D-profile measurement using TEM is limited by measurement time including processing of the sample. In this article, we demonstrate a novel on-wafer 3D-profile metrology as "FIB-to-CDSEM method" with FIB (Focused Ion Beam) slope cut and CD-SEM (Critical Dimension Secondary Electron Microscope) measuring. Using the method, a few micrometer wide on a wafer is coated and cut by 45 degree slope using FIB tool. Then, the wafer is transferred to CD-SEM to measure the cross section image by top down CD-SEM measurement. We apply FIB-to-CDSEM method to CMOS sensor device. 3D-profile and 3D-profile parameters such as top line width and side wall angles of CMOS sensor device are evaluated. The 3D-profile parameters also are measured by TEM images as reference metrology. We compare the 3D-profile parameters by TEM method and FIB-to-CDSEM method. The average values and correlations on the wafer are agreed well between TEM and FIB-to- CDSEM methods.

For yield improvement of 3D-device manufacturing, metrology for the variability of individual device-features is on hot issue. Transmission Electron Microscope (TEM) can be used for monitoring the individual cross-section. However, efficiency of process monitoring is limited by the speed of measurement including preparation of lamella sample. In this work we demonstrate speedy 3D-profile measurement of individual line-features without the lamella sampling. For instance, we make a-few-micrometer-wide and 45-degree-descending slope in dense line-features by using Focused Ion Beam (FIB) tool capable of 300mm-wafer. On the descending slope, obliquely cut cross-section of the line features appears. Then, we transfer the wafer to Critical-Dimension Secondary Electron Microscope (CDSEM) to measure the oblique cross-section in normal top-down view. As the descending angle is 45 degrees, the oblique cross-section looks like a cross-section normal to the wafer surface. For every single line-features the 3D dimensions are measured. To the reference metrology of the Scanning TEM (STEM), nanometric linearity and precision are confirmed for the height and the width under the hard mask of the line features. Without cleaving wafer the 60 cells on the wafer can be measured in 3 hours, which allows us of near-line process monitor of in-wafer uniformity.

The addition of MeLi to boron enolates produced by the 1,4-addition of Ar2Cu(CN)Li2 to BF3·OEt2-activated enones was followed by the reaction with ClP(O)(OEt)2 to afford the corresponding enol phosphates in moderate to good yields. The scope of this method was examined with sterically hindered or electronically biased enones and/or reagents. This activation of boron enolates was successfully applied to the synthesis of the methyl ether of Δ9-tetrahydrocannabinol.

Line edge roughness (LER) and linewidth roughness (LWR) of a semiconductor device are important measures for evaluating its performance. Conventionally, LER and LWR have been evaluated from critical dimension scanning electron microscope (CD-SEM) images. However, the problem with CD-SEM measurement is that the high-frequency image noise is large, and the resolution is not sufficiently high. In order to overcome the problem of image noise in CD-SEM measurement, some techniques have been proposed. In these methods, it is necessary to set the parameters for the model and processing, and it is required to verify the correctness of these parameters using reference metrology. We have already proposed a reference metrology using the focused ion beam process and planar transmission electron microscope (planar-TEM) method. In this study, we apply the proposed method to three new samples, namely self-aligned quadruple patterning fin-shaped field-effect transistor device, extreme ultraviolet lithography (EUV) conventional resist, and EUV new material resist. The LWR and the power spectral density (PSD) of LWR are calculated from the edge positions on planar-TEM images. We confirm that the LWR and the PSD of LWR can be measured with high accuracy and evaluate the difference between PSD by the proposed method and that by CD-SEM images. Furthermore, from comparisons with the PSD of the same sample obtained using CD-SEM, the validity of measurement of PSD and LWR by CD-SEM is verified.

Measurement of line edge roughness (LER) is discussed from four aspects: edge detection, power spectrum densities (PSD) prediction, sampling strategy, and noise mitigation. General guidelines and practical solutions for LER measurement today are introduced. Advanced edge detection algorithms such as the wave-matching method are shown to be effective for robustly detecting edges from low SNR images, whereas a conventional algorithm with weak filtering is still effective in suppressing SEM noise and aliasing. An advanced PSD prediction method such as the multitaper method is effective in suppressing sampling noise within a line edge to analyze, whereas a number of lines are still required for suppressing line-to-line variation. Two types of SEM noise mitigation methods, such as the “apparent noise floor” subtraction method and LER-noise decomposition using regression analysis, are verified to successfully mitigate SEM noise from PSD curves. These results are extended to local critical-dimension uniformity (LCDU) measurement to clarify the impact of SEM noise and sampling noise on LCDU.

The critical-dimension scanning electron microscope (CD-SEM) is an essential tool for semiconductor fabrication process control because of its high resolution and high precision. However, in ArF lithography, the CD of resist changes during CD-SEM measurement due to shrinkage caused by the electron beam irradiation. This shrinkage can be reduced by measurement parameters; however, there is a trade-off relationship between shrinkage and precision. Thus, measuring the CD of an ArF resist pattern precisely with small shrinkage is difficult. The authors propose an optimization method using the Taguchi method. Four measurement parameters were chosen as control factors for an L18 orthogonal array: probe current, acceleration voltage, horizontal length of field-of-view, and number of image acquisitions. As a result, high prediction accuracy was obtained that is smaller than 0.2 nm for shrinkage and 0.1 nm for precision. Moreover, an optimum measurement condition that achieves 0.28 nm shrinkage and 0.37 nm precision was also obtained. Thus, the proposed method was demonstrated as a promising method to optimize CD measurement parameters.

To establish a method of measuring interconnect line-edge roughness (LER), low-k line patterns were observed and electric field concentration was simulated on the basis of observation results. Wedge-shaped LERs were observed at the edges of low-k lines, and the bottom and the top widths of the average wedge feature were 60 and 7 nm (or smaller), respectively. Simulation showed that LER causes serious electric field concentration, which may cause the degradation of time-dependent dielectric breakdown (TDDB) lifetime at 100-nm-pitch Cu/low-k interconnects. The maximum electric field strength depends on the conventional LER metric 3Rq, but depends more strongly on the wedge angle, the curvature of the tip. That is, other metrics such as wedge angle can predict fatal electric field concentration caused by LER than the conventional metric 3Rq.

A metrological definition and a target value for linewidth roughness (LWR) in a gate pattern of MOSFETs are proposed. The effects of sampling interval gate-LWR measurements by critical-dimension scanning electron microscopy on measurement accuracy were examined by both experiment and simulation. It was found that a 10-nm interval is sufficiently small to fully characterize roughness in a typically chosen 2-mum-long line. Random image noise and intrinsic LWR variations are found to have larger effects on the measured LWR value than the finiteness of the sampling interval. A practical procedure for improving the measurement accuracy is also devised. Moreover, a methodology for establishing the gate-LWR target is proposed. Threshold-voltage shift caused by gate-LWR is determined from the LWR spectrum and the I-V curves of a transistor without LWR (i.e., ideal I-V curves).

A new method of evaluating line-edge or linewidth roughness (LER/LWR) is proposed. Conventional, directly measured LER/LWR values always contain a random noise contribution called LER/LWR bias. Our method can separate this bias artifact from the true LER/LWR using a single image of the pattern. The idea is based on the dependence of calculated LER/LWR value on the image-processing parameter for noise reduction. Both the conventional and the new bias-free LER/LWR were calculated using a series of images with different signal integration times (numbers of frames) but a fixed field of view. The LER/LWR obtained by our method was independent of the number of frames, and agreed with the conventional LER/LWR as measured using an image with a sufficiently large number of frames. It is concluded that the proposed bias-free LER/LWR measurement method will be a powerful tool in lithography metrology, especially for achieving practical and accurate LER/LWR measurement with little sample damage.

A novel method of sub-nanometer uncertainty for the line profile measurement using TEM (Transmission Electron Microscope) images is proposed to calibrate CD-SEM (Critical Dimension Scanning Electron Microscope) line width measurement and to standardize line profile measurement through reference metrology. The proposed method has been validated for profile of Si line and photoresist features in our previous investigations. In this article, we apply the methodology to line profile measurements of advanced-FinFET (Fin-shaped Field-Effect Transistor) features. The FinFET features are sliced as thin specimens of 100 nm thickness by FIB (Focused Ion Beam) micro sampling system. Cross-sectional images of the specimens are obtained then by TEM. The profiles of fin, hardmask and dummy gate of FinFET features are evaluated using TEM images. The width of fin, the length of hardmask, and the length of dummy gate of FinFET features are measured and compared to CD-SEM measurement. The TEM results will be used to implement CD-SEM and CD-AFM reference metrology.

The design rule of semiconductor devices in 1984s, when optical microscope was used for critical dimension measurement of device patterns, was around 1.3 µm. Instead of the optical microscope which did not provide enough resolution for the further device shrinkage, CD-SEM (Critical-Dimension Scanning Electron Microscope) was used for 1 µm or smaller design rule. This report introduces recent CD-SEM technologies and future prospect for such smaller design rule. Furthermore, evaluation of CD-measurement accuracy is introduced. It consists of short-term and long-term repeatabilities and tool-to-tool matching. A new linewidth-measurement algorithm is implemented for better short-term repeatability. A method of contrast-gradient is used for tool-to-tool matching. A traceable standard-sample for magnification calibration is also used.

General property of line-edge roughness (LER) in resist pattern and its transferability to under-lying layer were investigated. Longer-period components were found to have larger amplitudes in a resist pattern and to remain after dry etching. In addition, long-period LER strongly affects a transistor performance. Long-period LER in resist patterns, therefore, is as important as short-period LER. Metrology of LER was reconsidered to evaluate the both LER properly, and a guideline for choosing measurement parameters was proposed from a viewpoint of device performance estimation.

We have proposed a new method for correcting electron beam (EB)-induced photoresist shrinkage in two-dimensional pattern contours extracted from a scanning electron microscope image. This method restores the original shrinkage-free contour from the experimentally determined “shrunk contour”, based on a shrinkage model which takes into account of the elastic nature of the shrinkage phenomena caused by the photoresist-volume reduction. Verification of this shrinkage model was demonstrated by using ArF resist patterns as follows. First, the model was calibrated with the shrinkage data of several line patters with different linewidth prior to the contour correction. Next, the amount of shrinkage of elbow patterns was measured by comparing its contours obtained with small and sufficiently large EB dosages. It was found that the shrinkage of the inner edge of the elbow corner was smaller than that of the outer edge, which can be interpreted as a result of the elastic deformation. Finally, validity of shrinkage correction was examined. The model calculation correctly reproduced the observed shrinkage including its dependence on the location in the pattern. The restored contour showed a good consistency with the experimental results and the total root-mean-square error of the shrinkage correction was 0.5 nm. This result confirmed that our shrinkage model adequately describes the shrinkage of two dimensional patterns. Consequently, proposed shrinkage correction method is expected to improve the accuracy of contour measurements by a critical dimension-scanning electron microscope.

The novel method of sub-nanometer uncertainty for the line width measurement and the line profile measurement using STEM (Scanning Transmission Electron Microscope) images is proposed to calibrate CD-SEM line width measurement and the standardization of line profile measurement as reference metrology. In accordance with the proposed method, we already have established the methodology of profile of Si line and photoresist feature for reference metrology. In this article, we applied the proposed method to the sidewall roughness measurement of photoresist features and line profile measurement of finFET features. Using the proposed method, specimens of photoresist feature and finFET feature are sliced as thin specimens of 100 nm thickness by FIB (Focused Ion Beam) micro sampling system. Then the cross-sectional images of the specimens are obtained by STEM and TEM. The sidewall roughness of photoresist features is estimated by the maximum slope of the image intensity graph at the edge. Then, the sidewall roughness is also measured by CD-AFM (Critical Dimension Atomic Force Microscope); we compared the results by STEM image and CD-AFM. Moreover, the line profile of finFET features is defined using TEM images for reference metrology. We compared the line width of fin measured by the proposed method and CD value by CD-SEM measurement.

The chemical reaction of residues formed on a quartz surface in an electron cyclotron resonance plasma during the etching of Al and resist film by Cl2 and BCl3 plasma was characterized in situ by infrared reflection absorption (IRA) spectroscopy and quadrupole mass spectrometry (QMS). The plasma was generated in a chamber with a structure similar to a conventional production machine. Incident ions and molecules impacting onto a quartz surface at the chamber wall were analyzed by QMS. Then the residue formed on a quartz film on a sample mounted on the chamber wall was analyzed by IRA spectroscopy. The residue was identified as B2O3 which is formed by incident boron chloride ions that diffuse down through the B2O3 residue to the quartz surface and, there, thermally react with OH in the quartz. The residue film produced on the quartz surface could be identified by etching a 1-μm-thick Al film ten times at the etching rate of 12 nm/s. This combination of IRA and QMS is a promising technique for refining on-li...

Metrology of line-edge roughness (LER) or line-width roughness (LWR) reduced less than a few nanometers in recent advanced-process is one of issues because measured LER is strongly dependent on measurement conditions such as magnification and beam dose. It may happen that different organizations measure different LERs on an identical sample. By using an ultra-low LER sample we demonstrate intolerable change of measured LER between with and without necessary key-points in the measurement conditions of critical-dimension secondary electron microscope (CD-SEM).

The mechanism of photoresist shrinkage induced by electron-beam (EB) irradiation was studied. A precise cross-sectional profile of a photoresist pattern was obtained by a scanning transmission electron microscope (STEM) after atomic layer deposition of HfO2 on the sample patterns. Photoresist lines and spaces fabricated with positive-tone development and negative-tone development were exposed to an EB with much higher dose than a practical dose (to accelerate shrinkage intentionally). The obtained STEM images of the patterns before and after EB irradiation show that the shrinkage of the negative-tone-developed patterns is smaller than that of the positive-tone-developed patterns. This observation is explained by the fact that negative-tone-developed photoresist molecules do not contain protection groups, whose volatilization caused by EB irradiation is one of the origins of shrinkage. Another finding is that the EB irradiation causes top-rounding and necking of the pattern profile as well as linewidth slimming. The rounding of the pattern top profile suggests that the pattern’s shape was elastically deformed. In addition, EB irradiation only onto the spaces caused sidewall shrinkage and a necking profile, although no electrons were irradiated directly onto the pattern. These phenomena are considered to be due to the electrons scattered from the spaces to the pattern sidewall. Finally, a Monte Carlo simulation of electron scattering showed that the distribution of the deposited EB energy on the pattern surface corresponds to the above-described change in pattern shape. Consequently, these observations and simulation results clarify the importance of the effect of elastic shape change and the impact of the electrons scattered from the underlying layer onto the sidewall in the mechanism of photoresist shrinkage.

One of the main issues with overlay error metrology accuracy is the bias between results based on overlay (OVL) targets and actual device overlay error. In this study, we introduce the concept of Device Correlated Metrology (DCM), which is a systematic approach to quantifying and overcoming the bias between target-based overlay results and device overlay issues. For systematically quantifying the bias components between target and device, we introduce a new hybrid target integrating an optical OVL target with a device mimicking CD-SEM (Critical Dimension – Scanning Electron Microscope) target. The hybrid OVL target is designed to accurately represent the process influence found on the real device. In the general case, the CD-SEM can measure the bias between target and device on the same layer at AEI (After Etch Inspection) for all layers, the OVL between layers at AEI for most cases and at ADI (After Develop Inspection) for limited cases such as DPL (Double Patterning Lithography). The results shown demonstrate that for the new process compatible hybrid targets the bias between target and device is small, of the order of CD-SEM measurement uncertainty. Direct OVL measurements by CD-SEM show excellent correlation with optical OVL measurements in certain conditions. This correlation helps verify the accuracy of the optical measurement results and is applicable for imaging based OVL metrology methods using AIM or AIMid OVL targets, and scatterometry-based overlay methods such as SCOL (Scatterometry OVL). Future plans include broadening the hybrid target design to better mimic each layer’s process conditions such as pattern density. We are also designing hybrid targets for memory devices.

A new method for calculating critical dimension (CDs) at the top and bottom of three-dimensional (3D) pattern profiles from a critical-dimension scanning electron microscope (CD-SEM) image, called as “T-sigma method”, is proposed and evaluated. Without preparing a library of database in advance, T-sigma can estimate a feature of a pattern sidewall. Furthermore, it supplies the optimum edge-definition (i.e., threshold level for determining edge position from a CDSEM signal) to detect the top and bottom of the pattern. This method consists of three steps. First, two components of line-edge roughness (LER); noise-induced bias (i.e., LER bias) and unbiased component (i.e., bias-free LER) are calculated with set threshold level. Second, these components are calculated with various threshold values, and the threshold-dependence of these two components, “T-sigma graph”, is obtained. Finally, the optimum threshold value for the top and the bottom edge detection are given by the analysis of T-sigma graph. T-sigma was applied to CD-SEM images of three kinds of resist-pattern samples. In addition, reference metrology was performed with atomic force microscope (AFM) and scanning transmission electron microscope (STEM). Sensitivity of CD measured by T-sigma to the reference CD was higher than or equal to that measured by the conventional edge definition. Regarding the absolute measurement accuracy, T-sigma showed better results than the conventional definition. Furthermore, T-sigma graphs were calculated from CD-SEM images of two kinds of resist samples and compared with corresponding STEM observation results. Both bias-free LER and LER bias increased as the detected edge point moved from the bottom to the top of the pattern in the case that the pattern had a straight sidewall and a round top. On the other hand, they were almost constant in the case that the pattern had a re-entrant profile. T-sigma will be able to reveal a re-entrant feature. From these results, it is found that T-sigma method can provide rough cross-sectional pattern features and achieve quick, easy and accurate measurements of top and bottom CD.

The novel method of sub-nanometer uncertainty for the line width measurement and line profile measurement using STEM (Scanning Transmission Electron Microscope) images is proposed to calibrate CD-SEM line width measurement and standardization of line profile measurement as reference metrology. In accordance with the proposed method, we already have established the methodology of Si line profile and line width measurement for reference metrology. In this article, we applied the proposed method to edge determination methodology of the photoresist feature. Using the proposed method, a specimen of photoresist feature is coated with metal, and then it is sliced as a thin specimen of 100 nm thickness by FIB (Focused Ion Beam) micro sampling system. Then the dark-field cross-sectional images of the specimen are obtained by STEM. The edge position of the photoresist is defined at the distance of half metal coating thickness from the peak positions of metal coating area. Then the detected line profiles are compared with the measurement results by CD-AFM. From series of analyses, we established the edge detection methodology of photoresist feature for reference metrology.

As device design rule has been made pattern size shrink, overlay control has become one of the most critical issues for semiconductor manufacturing. Advanced lithographic exposure tools, such as EUV and i-ArF scanners, require high-order overlay corrections. In conventional overlay metrology, several overlay targets are arranged in scribe area on product wafer. However, the number of measurement point is not sufficient for high-order overlay corrections and these positions are too far from device patterns to estimate its overlay. High-order overlay corrections should be calculated from overlay measurement data by using a considerable number of in-die targets near device pattern. In this case, smaller target area size is expected for advanced lithography. In this paper we introduce in-die overlay metrology by using critical dimension scanning electron microscope (CD-SEM). It has several advantages over a conventional optical overlay measurement tool, 1) the target area size can be set smaller than 5 x 5 μm, 2) the size and feature of measurement pattern can be set similar to device design, therefore WIS (Wafer Induced Shift) is assumed to be small, 3) TIS (Tool Induced Shift) by CD-SEM, which we measure, is small. Furthermore, we show repeatability and accuracy of the overlay measurement by CD-SEM. And overlay distribution measured by die-to-die can be verified by sufficient number of the dedicated targets in-die.