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In this work, hafnium zirconium oxide (HZO)-based 100 × 100 nm2 ferroelectric tunnel junction (FTJ) devices were implemented on a 300 mm wafer platform, using a baseline 65 nm CMOS process technology. FTJs consisting of TiN/HZO/TiN were integrated in between metal 1 (M1) and via 1 (V1) layers. Cross-sectional transmission electron microscopy and energy dispersive x-ray spectroscopy analysis confirmed the targeted thickness and composition of the FTJ film stack, while grazing incidence, in-plane x-ray diffraction analysis demonstrated the presence of orthorhombic phase Pca21 responsible for ferroelectric polarization observed in HZO films. Current measurement, as a function of voltage for both up- and down-polarization states, yielded a tunneling electroresistance (TER) ratio of 2.28. The device TER ratio and endurance behavior were further optimized by insertion of thin Al2O3 tunnel barrier layer between the bottom electrode (TiN) and ferroelectric switching layer (HZO) by tuning the band offset between HZO and TiN, facilitating on-state tunneling conduction and creating an additional barrier layer in off-state current conduction path. Investigation of current transport mechanism showed that the current in these FTJ devices is dominated by direct tunneling at low electric field ( E 0.4 MV/cm). The modified FTJ device stack (TiN/Al2O3/HZO/TiN) demonstrated an enhanced TER ratio of ∼5 (2.2× improvement) and endurance up to 106 switching cycles. Write voltage and pulse width dependent trade-off characteristics between TER ratio and maximum endurance cycles (Nc) were established that enabled optimal balance of FTJ switching metrics. The FTJ memory cells also showed multi-level-cell characteristics, i.e., 2 bits/cell storage capability. Based on full 300 mm wafer statistics, a switching yield of >80% was achieved for fabricated FTJ devices demonstrating robustness of fabrication and programming approach used for FTJ performance optimization. The realization of CMOS-compatible nanoscale FTJ devices on 300 mm wafer platform demonstrates the promising potential of high-volume large-scale industrial implementation of FTJ devices for various nonvolatile memory applications.

Measurement and control of line edge roughness (LER) is one of the most challenging issues facing patterning technology. As the critical dimensions (CD) of patterned structures decrease, LER of only a few nanometers can negatively impact device performance. Here, Mueller matrix spectroscopic ellipsometry (MMSE) based scatterometry is used to determine LER in periodic line-space structures in 28 nm pitch Si fin samples fabricated by directed selfassembly (DSA) patterning. The optical response of the Mueller matrix (MM) elements is influenced by structural parameters like pitch, CD, height, and side-wall angle (SWA), as well as the optical properties of the materials. Evaluation and decoupling MM element response to LER from other structural parameters requires sensitivity analysis using simulations of optical models that include LER. Here, an approach is developed that quantifies Si fin LER by comparing the optical responses generated by systematically varying the grating shape and measurement conditions. Finally, the validity of this approach is established by comparing the results obtained from top down scanning electron microscope (SEM) images and cross-sectional TEM image of the 28 nm pitch Si fins.

Simulations of Mueller matrix spectroscopic ellipsometry (MMSE) based scatterometry are used to predict sensitivity to dimensional changes and defects in directed self-assembly (DSA) patterned contact hole structures fabricated with phase-separated polystyrene-b-polymethylmethacrylate (PS- b -PMMA) before and after etch. The optical signature of Mueller matrix (MM) elements has a complex dependence on the structure topography and orientation, depolarization, and optical properties of the materials associated with the surface and any underlying layers. Moreover, the symmetry properties associated with MM elements provide an excellent means of measuring and understanding the topography of periodic nanostructures. A forward problem approach to scatterometry or optical model based simulations is used to investigate MMSE sensitivity to various DSA based contact hole structures and its limits to characterize DSA induced defects such as hole placement inaccuracy, missing vias, profile inaccuracy of the PMMA cylinder, and process induced defects such as presence of residual PMMA after etching.

Traditional ellipsometric measurements of copper gratings are limited to Angstrom resolution and are rather insensitive to changes in the critical dimension (CD) or pitch of the structure. By adding another grating per- pendicular and with larger CD and pitch, sensitivity is greatly enhanced. The spectra of one dimensional grat- ings is largely featureless over a wide range of CDs while crossed-gratings exhibit large minima which shift with changing CDs of less than an Angstrom. This improvement is due to plasmonic activity in the crossed-grating, demonstrated in detail here. Mueller matrix element analysis under azimuthal rotation provides information about cross-polarization and plasmon coupling conditions.

Directed self-assembly (DSA) based block copolymer (BCP) lithography shows promise as a cost-effective manufacturing technique for advanced sub-20 nm patterning. Characterization of types of defects and their levels in the sub-20 nm DSA patterns is a challenge for the current state-of-the-art metrology. Scatterometry has the capability of measuring important feature dimensions of DSA structures quickly and non-destructively at multiple steps in the process. This work is a report on the use of Mueller matrix spectroscopic ellipsometry (MMSE) based measurements of 28 nm pitch Si fins fabricated from DSA line patterns consisting of polystyrene-block-polymethylmethacrylate (PS-b-PMMA) fabricated using a chemical epitaxy process. A regression-based (inverse-problem) scatterometry approach was used to calculate the CD, line shapes, and thickness of the developed Si fin patterns. Sensitivity of MMSE to defectivity and line edge roughness (LER) in Si fin samples is discussed. At DSA dimensions the characterization of LER is crucial due to increase in the ratio between LER and target line width. HR-XRD and SEM imaging is also conducted as a comparative metric for scatterometry. This paper emphasizes the effectiveness of MMSE based scatterometry as a technique for optical characterization of Si fins fabricated with DSA lithography.

Directed self-assembly (DSA) shows considerable promise as a cost-effective manufacturing technique for advanced sub-20 nm patterning. Along with continued progress, the patterning process requires advances in both CD metrology and high-speed characterization of DSA defectivity. This work is a report on the study of Mueller matrix spectroscopic ellipsometry (MMSE) scatterometry measurements of 28 nm pitch DSA line/space patterns consisting of polystyrene- block - polymethylmethacrylate (PS- b -PMMA) block copolymer sample fabricated using a chemical epitaxy process. Generalized ellipsometric data (all 16 Mueller elements) is collected over a spectral range from 245 to 1700 nm for various different pre-pattern pitch/guide strip combinations created by modulating the pre-pattern photoresist CD. Scatterometry is used to evaluate and calculate the CD, line shapes, and thicknesses of the plasma developed PS patterns (PMMA removed). Likewise, spectral comparisons based on anisotropy and depolarization are used to determine the DSA pattern defectivity. CD-SEM metrology and imaging is also conducted as a comparative metric for scatterometry. The sensitivity of MMSE to pre-pattern pitch and pitch multiplication on PS line CD and defectivity is demonstrated. Slight imperfections in the line/space pattern as well as fingerprint like patterns (undirected assembly) can be distinguished from aligned patterns using MMSE scatterometry.

Although fin metrology presents many challenges, the single crystal nature of the fins also provides opportunities to use a combination of measurement methods to determine stress and pitch. While the diffraction of light during a scatterometry measurement is well known, X-ray diffraction from a field (array) of single crystal silicon fins can also provide important information. Since some fins have Si 1-x Ge x alloys at the top of the fin, determination of the presence of stress relaxation is another critical aspect of fin characterization. Theoretical studies predict that the bi-axially stressed crystal structure of pseudomorphic alloy films will be altered by the fin structure. For example, one expects it will be different along the length of the fin vs the width. Reciprocal space map (RSM) characterization can provide a window in the stress state of fins as well as measure pitch walking and other structural information. In this paper, we describe the fundamentals of how RSMs can be used to characterize the pitch of an array of fins as well as the stress state. We describe how this impacts the optical properties used in scatterometry measurement.

The uses of strained channel became prevalent at the 65 nm node and have continued to be a large part of logic device performance improvements in every technology generation. These material and integration innovations will continue to be important in sub-22nm devices, and are already being applied in finFET devices where total available in-channel strains are potentially higher. The measurement of structures containing these materials is complicated by the intrinsic correlation of the measured optical thickness and variation of optical properties with strain, as well as the dramatic reduction in total volume of the device. Optical scatterometry has enabled characterization of the feature shape and dimensions of complex 3D structures, including non-planar transistors and memory structures. Ellipsometric methods have been successfully applied to the measurement of thin films of SiGe and related strained structures. A direction for research is validating that the thin film stress results can be extended into the much more physically complex 3D shape. There are clear challenges in this: the stress in a SiGe fin is constrained to match the underlying Si along one axis, but the sides and top are free, leading to very large strain gradients both along the fin width and height. Practical utilization of optical techniques as a development tool is often limited by the complexity of the scatterometry model and setup, and this added material complexity presents a new challenge. In this study, generalized spectroscopic ellipsometric measurements of strained grating was undertaken, in parallel with reference cross sectional and top down SEM data. The measurements were modeled for both anisotropy calculations, as well as full scatterometry calculations, fitting the strain and structure. The degree to which strain and CD can be quickly quantified in an optical model is discussed. Sum decomposition method has been implemented to extract the effective anisotropic coefficients and a discussion on the effect of anisotropy toward modeling is presented. Finally, errors in the scatterometry measurement are analyzed, and the relative strengths and limitations of these optical measurements compared.

Directed self-assembly (DSA) is a potential patterning solution for future generations of integrated circuits. Its main advantages are high pattern resolution (∼10 nm), high throughput, no requirement of high-resolution mask, and compatibility with standard fab-equipment and processes. The application of Mueller matrix (MM) spectroscopic ellipsometry-based scatterometry to optically characterize DSA patterned contact hole structures fabricated with phase-separated polystyrene-b-polymethylmethacrylate (PS-b-PMMA) is described. A regression-based approach is used to calculate the guide critical dimension (CD), DSA CD, height of the PS column, thicknesses of underlying layers, and contact edge roughness of the post PMMA etch DSA contact hole sample. Scanning electron microscopy and imaging analysis is conducted as a comparative metric for scatterometry. In addition, optical model-based simulations are used to investigate MM elements’ sensitivity to various DSA-based contact hole structures, predict sensitivity to dimensional changes, and its limits to characterize DSA-induced defects, such as hole placement inaccuracy, missing vias, and profile inaccuracy of the PMMA cylinder.

Our manuscript contained data from unconverged rigorous coupled wave approximation (RCWA) simulations that resulted in incorrect description of minima locations. Here, converged RCWA simulations are presented with corrected minima behavior described. The principle of plasmonic enhancement and its use in ellipsometric test structures is maintained.

Measurement and control of line edge roughness (LER) is one of the most challenging issues facing patterning technology. As the critical dimensions (CDs) of patterned structures decrease, an LER of only a few nanometers negatively impacts device performance. Here, Mueller matrix (MM) spectroscopic ellipsometry-based scatterometry is used to characterize LER in periodic line-space structures in 28-nm pitch Si fin samples fabricated by directed self-assembly patterning. The optical response of the MM elements is influenced by structural parameters like pitch, CDs, height, and side-wall angle, as well as the optical properties of the materials. Evaluation and decoupling MM element response to LER from other structural parameters requires sensitivity analysis using scatterometry models that include LER. Here, an approach is developed that can be used to characterize LER in Si fins by comparing the optical responses generated by systematically varying the grating shape and measurement conditions. Finally, the validity of this approach is established by comparing the results obtained from power spectral density analysis of top down scanning electron microscope images and cross-sectional transmission electron microscope image of the 28-nm pitch Si fins.

Patterning based on directed self-assembly (DSA) of block copolymer (BCP) has been demonstrated to be a cost-effective manufacturing technique for advanced sub-20-nm structures. This paper describes the application of Mueller matrix spectroscopic ellipsometry (MMSE) based scatterometry to optically characterize polystyrene-b-polymethylmethacrylate patterns and Si fins fabricated with DSA. A regression-based (inverse-problem) approach is used to calculate the line-width, line-shape, sidewall-angle, and thickness of the DSA structures. In addition, anisotropy and depolarization calculations are used to determine the sensitivity of MMSE to DSA pattern defectivity. As pattern order decreases, the mean squared error value increases, depolarization value increases, and anisotropy value decreases. These specific trends are used in the current work as a method to judge the degree of alignment of the DSA patterns across the wafer.

In this paper, we propose a cross-grating structure to enhance the critical dimension sensitivity of one dimensional nanometer scale metal gratings. Making use of the interaction between slight changes in refractive index and localized plasmons, we demonstrate sub-angstrom scale sensitivity in this structure. Compared to unaltered infinite metal gratings and truncated finite gratings, this cross-grating structure shows robust spectra dependent mostly on the dimension of the smaller line width and pitch. While typical scatterometry simulations show angstrom resolution at best, this structure has demonstrated picometer resolution. Due to the wide range of acceptable specifications, we expect experimental confirmation of such structures to soon follow.

Although the treatment of water by chlorine or hypochlorite has been very extensively practised for several years, it is a regrettable fact that comparatively few investigations have been made into this process with a view to elucidating the basic principles and the modifications required to meet various conditions. When chlorination was first introduced for the sterilization of water and sewage, all that was required was the addition of the hypochlorite; after this the process was supposed to take care of itself. Now we realize that, to obtain the best results, the process requires careful supervision and close attention to certain points. It is the purpose of the author to draw attention to some of these details in this paper.

D URING the early part of 1912 the author made a number of experiments in the laboratories of the Toronto Filtration Plant with the object of determining what was the most suitable media that might be used for making bacterial counts of the various waters examined. These experiments extended over a penrod of six months and cover various seasons but are not as extensive as could be desired. A change of appointments, however, brought them abruptly to a close and until now no opportunity has been afforded of preparing these results in a form fit for publication. The recent criticisms of Whipple, Baton, and others of the report of the Committee on Standard Methods of Water Examination of the American Public Health Association has -once again brought this subject to the fore and the author takes this opportunity of presenting his results inthe hope that they may aid in reaching a solution of this difficult problem. The majority of the samples examined in the laboratories were in connection with the filtration plant and consisted of raw and filtered waters, but as a chlorinating plant was' also being supervised it was important that chlorinated waters should also be considered. The object of the experiments was not to ascertain what media would show the largest-percentage purification effected by the filters but to select 48E a medium which would most effectively and speedily determine the sanitary value of the various waters submitted for examination. The various points considered in this connection were: (1) Agreement with B. coli results. (2) Time required to obtain results. (3) Delicacy. (4) Convenience. It seemed to the author that the primary essential was to correlate the results with the B. coli figures, as it is largely upon these latter that the bacteriological evidence of the sanitary value of a water is based. While acknowledging the weakness of this basis, it was used on account of the total inadequacy of all others that have been suggested. The time required for securing results is obviously of the fiirst importance if the results are to be of practical utility. Delicacy and convenience are bf minor importance. At -first nutrient gelatine at 20°C., agar at 377C. and mixtures of agar and geIatine at 20°C. were employed but various changes were afterwards deemed advisable and effected.

The studies reported in this paper are a continuation of those recorded in last year's Journal (vol. 3, 1916, 439-449) and constitute a partial attempt to place water chlorination on a scientific basis. Until comparatively recently the data that we possessed were a disconnected mass of empirically established facts, and it is a regrettable feature that although it is on this continent that the art of chlorination has progressed the most rapidly, it is in Europe, under the stimulus of war, that it is being developed as a science. As chlorination becomes more general it becomes increasingly evident that our stock of information regarding the conditions that tend to successful results is very meagre, and that the dosage is largely determined by the trial and error method. We are also lamentably ignorant as to the reason why some waters have but very small margins between the dose required for satisfactory purification and that which causes complaints as to tastes and odors, while others have much greater ones and can easily absorb slight excesses of the sterilizing agent. Complaints that arise in this way are often ascribed to auto-suggestion by water works and health officials, but they are too often based upon solid fact to be disposed of in this manner, and the time and energy that have been devoted to deluding the public might much better have been spent in improving present methods and so eliminating the cause for complaints. Chlorination is such a cheap and simple process that it is often considered the ultima thule of chemical sterilization, but there is no reason to doubt that the present methods will be modified and considerably improved. A simple modification that has yielded good results with some waters will be described later, but before treating that in detail a few general factors will be considered. In the last paper, the author gave results showing the effect of time, mechanical admixture, temperature, and organic matter upon chlorination by

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