Surface Metrology Research Articles

Methodology for pad conditioning sweep optimization for advanced nodes

With increasing focus on 3D integration of devices, there is an increasing demand for polishing thick silicon dioxide films. The impact of changes in the CMP pad thickness profiles on high silicon dioxide film rates and profiles are studied. A simulator was used to predict pad thickness profiles for different pad conditioning sweeps. Subsequently, these different pad conditioning sweep profiles were used to study their impact on pad thickness profiles and material removal rates (MRR) experimentally on an Applied Materials' (AMAT) 300 mm wafer Reflexion® LK polisher. The pad thickness profiles were measured using laser confocal microscopy and AMAT's state-of-the-art full pad surface metrology tool. The difference in the pad thickness values provided by all the 3 methods was <5%. It has been validated that the pad thickness profiles provided by confocal microscopy and full pad metrology measurements matches the profile predicted by the simulator.

The intertwined roles of particle shape and surface roughness in controlling the shear strength of a granular material

Both the shape of individual particles and their surface properties contribute to the strength of a granular material under shear. Here we show the degree to which these two aspects can be intertwined. In experiments on assemblies of 3D printed, convex lens-shaped particles, we measure the stress–strain response under repeated compressive loading and find that the aggregate’s shear strength falls rapidly when compared to other particle shapes. We probe the granular material at mm-scales with X-ray computed tomography and $$\upmu $$ m-scales with high-resolution surface metrology to look for the cause of the degradation. We find that wear due to accumulated deformation smooths out the lens surfaces in a controlled and systematic manner that correlates with a significant loss of shear strength observed for the assembly as a whole. The sensitivity of lenses to changes in surface properties contrasts with results for assemblies of 3D printed tetrahedra and spheres, which under the same load cycling are found to exhibit only minor degradation in strength. This case study provides insight into the relationship between particle shape, surface wear, and the overall material response, and suggests new strategies when designing a granular material with desired evolution of properties under repeated deformation.

Investigation on multi-body dynamics based approach to the toolpath generation for ultraprecision machining of freeform surfaces

This article presents an innovative approach to toolpath generation for ultraprecision machining of freeform optic surfaces based on the principle of Automatic Dynamics Analysis of Mechanical Systems. As components with freeform surfaces often have non-rotational symmetry, there are potential challenges facing their ultraprecision machining through single-point diamond turning, such as the projected points in complex large sag surfaces, which likely find it difficult to communicate with the control system and, thus, do not perform successfully. In ultraprecision machining, to achieve the highest performance in freeform surface resolution, the factors of dynamics, material and mechanical stiffness, frictions, tooling and accuracy of the servo component should be considered. The investigation is focused on an integrated approach and the associated scientific understanding of precision engineering design, ultraprecision machining and metrology of freeform surfaces as well as their application perspective. In this approach, the toolpath for very complex freeform surfaces can be generated using the Newton–Raphson method to solve the kinematics and dynamics equations of motion. The effect of friction and contact force are also investigated for accurate toolpath curve generation. Moreover, the Gear stiff (GSTIFF)/ Wielenga stiff (WSTIFF) integrator for solving the non-linear equations of motion is employed, and the result shows the time step size, playing a critical role in generating toolpath curves with a higher accuracy and resolution.

A generic parallel computational framework of lifting wavelet transform for online engineering surface filtration

Nowadays, complex geometrical surface texture measurement and evaluation require advanced filtration techniques. Discrete wavelet transform (DWT), especially the second-generation wavelet (Lifting Wavelet Transform – LWT), is the most adopted one due to its unified and abundant characteristics in measured data processing, geometrical feature extraction, manufacturing process planning, and production monitoring. However, when dealing with varied complex functional surfaces, the computational payload for performing DWT in real-time often becomes a core bottleneck in the context of massive measured data and limited computational capacities. It is a more prominent problem for the areal surface texture filtration by using 2D DWT. To address the issue, this paper presents a generic parallel computational framework for lifting wavelet transform (GPCF-LWT) based on Graphics Process Unit (GPU) clusters and the Compute Unified Device Architecture (CUDA). Due to its cost-effective hardware design and the powerful parallel computing capacity, the proposed framework can support online (or near real-time) engineering surface filtration for micro- and nano-scale surface metrology through exploring a novel parallel method named LBB model, the improved algorithms of lifting scheme and three implementation optimizations on the heterogeneous multi-GPU systems. The innovative approach enables optimizations on individual GPU node through an overarching framework that is capable of data-oriented dynamic load balancing (DLB) driven by a fuzzy neural network (FNN). The paper concludes with a case study on filtering and extracting manufactured surface topographical characteristics from real surfaces. The experimental results have demonstrated substantial improvements on the GPCF-LWT implementation in terms of computational efficiency, operational robustness, and task generalization.

On-machine surface measurement and applications for ultra-precision machining: a state-of-the-art review

Surface measurement is essential to enhance accuracy and efficiency in ultra-precision machining. In order to increase the measurement availability and efficiency, offline lab-based solutions are shifting towards the use of surface metrology upon manufacturing platforms. With the lack of remounting errors, on-machine surface measurement (OMSM) allows the deterministic assessment of manufactured surfaces just-in-time and also provides valuable feedback to the process control of ultra-precision machining. This paper is aimed at reviewing the state-of-the-art OMSM and applications in the ultra-precision machining process. The benefits and considerations on the integration of metrology are discussed. The merits and limitations among different OMSM types are compared as well. Finally, the challenges and outlook of the ultra-precision machining-metrology integration are highlighted.

Here's the dirt: First applications of confocal microscopy for quantifying microwear on experimental ground stone earth working tools

Quantitative microscopy characterizing the surface texture of wear traces has helped develop a more standardized chipped stone tool microwear practice. However, to date, these surface metrology methods have not been used to characterize ground stone tool surfaces. To expand the range of raw materials and tool types tested with these methods, we explore the application of imaging confocal microscopy for the quantification of an assemblage of experimental hoes, modelled after Late Neolithic and Early Bronze Age artifacts from China. Surface texture properties of sediment wear are compared to wear from wooden hafts to identify whether confocal microscopy can distinguish between different wear types. The results show that there is a significant difference between sediment and hafting wear and suggests further research is needed to identify how experimental conditions affect polish measurements within wear types. This preliminary study indicates that imaging confocal microscopy has excellent potential for the quantification of microwear traces on ground stone tools and may contribute to our understanding of earth working tools in prehistory.

Investigation of the interaction between carbon nanotube tip and silicon sample through molecular dynamic simulation

Atomic Force Microscopy (AFM) has become a standard tool in experimental surface metrology, revealing atomic scale features of the surfaces. Carbon nanotube represents ideal structure for AFM tips because of their tiny diameter, high aspect ratio and high strength. This article employs molecular dynamics (MD) simulation approach to investigate the atomic-scale interaction between the AFM tips represented by carbon nanotube and sample. The interaction force between two different types of single walled carbon nanotube (SWCNT) tips including open ended carbon nanotube and capped carbon nanotube while the deformation mechanism during the measurement was discussed in detail. Firstly, the interaction force between SWCNT tips and sample in contact mode was simulated by using hybrid potential. The stiffness of the two different types of single walled carbon nanotubes were verified. The simulation results indicate that capped SWCNT tip is more prone to tilt than open ended SWCNT tip, but the ability to resist deformation is stronger. Then the dynamic model of tip-sample system in tapping mode was established. The relationship between the tip of load and the distance in the process of approaching to the sample was obtained by curve fitting. The numerical solution was achieved by solving the dynamic equation and frequency spectrum was obtained with the method of Fourier transforms.

Introduction of a Surface Characterization Parameter Sdrprime for Analysis of Re-entrant Features

Producing components using metal additive manufacturing processes, such as powder bed fusion, presents manufacturing and measurement challenges, but also significant opportunities. The as-built surface may include overhanging (re-entrant) features not intentionally included in the design, but that aid in component functionality. In addition, the additive manufacturing process presents opportunities to design and manufacture re-entrant features intentionally. Re-entrant features increase the specific surface area and, in addition, produce mechanical locking to the surface. These re-entrant features may be intended to improve surface performance in areas such as biological cell attachment, coating adhesion, electrical capacitance and battery plate design, fluid flow and material cooling. Re-entrant features may prove difficult or impossible to measure and characterise using conventional line-of-sight surface metrology instrumentation, however the correct measurement of these surfaces may be vital for functional optimisation. X-ray computed tomography does have the ability to image internal and re-entrant features. This paper reports on the measurement of re-entrant features using X-ray computed tomography and the extraction of actual surface area information (including re-entrant surfaces) from sample additively manufactured surfaces. A proposed new surface texture parameter, Sdrprime, is discussed. This parameter is applicable to true 3D data, including re-entrant features, and is intended to relate directly to the component surface functional performance. The errors produced when using line-of-sight instruments and height map parameter generation per ISO 25178-2 to evaluate surfaces that include re-entrant features are discussed. Measurement results for electron beam melting and selective laser melting additively manufactured components, together with simulated structured surfaces, are presented.

Design, additive manufacturing, processing, and characterization of metal mirror made of aluminum silicon alloy for space applications

Metal mirrors are used for spaceborne optical systems, such as telescopes and spectrometers. In addition to the optical performance, the mechanical needs and the mass restrictions are important aspects during the design and manufacturing process. Using the additive manufacturing process, optimized internal lightweight structures are realized to reduce the weight of the system while keeping the mechanical stability. A mass reduction of ≈60.5 % is achieved. Using the aluminum silicon alloy AlSi40, the thermal mismatch of the mirror base body to a necessary electroless nickel-polishing layer is minimized. Based on an exemplary mirror design, the optimization of the interior lightweight structure is described, followed by the manufacturing process from additive manufacturing to diamond turning, plating, and polishing. Finally, the results of surface metrology and light scattering measurements are presented. A final form deviation below 80 nm p . − v . and a roughness of ∼1 nm rms could be demonstrated.

Advances in Pad Conditioning for Enhancement of CMP Process Stability over Pad Life

There is an increasing demand for deposition of thick films because of increasing focus on 3D integration of devices. These thick films will require higher removal rates during the chemical mechanical planarization/polishing (CMP) process in order to avoid significantly high polish times for minimizing impact on throughput of the polisher. Aggressive polishing conditions will be required to achieve high removal rates, which in turn will need aggressive pad conditioning to maintain desired surface texture and prevent glazing of the pad. In this paper, the impact of different pad conditioning sweep profiles on CMP pad thickness profile and removal rate WIWNU & WTWNU will be discussed. A methodology is developed that uses a simulator to predict pad thickness profiles for different pad conditioning sweep profiles. Subsequently, these different pad conditioning sweep profiles are evaluated experimentally to study their impact on pad thickness profiles and material removal rates (MRR) on Applied Materials’ 300mm wafer polisher Reflexion® LK. The pad thickness profiles are characterized by confocal microscopy and state-of-the-art full pad surface metrology tool. Pad thickness profiles predicted by the simulator are compared with those measured using confocal microscopy and full pad metrology tool. It is validated that the pad profile trend predicted by the simulator matches with the actual pad thickness profile obtained on the polisher. Advantage of using full pad metrology tool relative to confocal microscopy is highlighted.

16th International Conference on Metrology and Properties of Engineering Surfaces (Met & Props 2017)

PrefaceProceedings of the 16th International Conference, Gothenburg, Sweden, 26th– 29th June, 2017Organized by:The International Program Committee of The International Conference Metrology and Properties of Engineering Surfaces, Met&PropsHalmstad University, SwedenGreetings from Chairman of the Local Organizing CommitteeOn behalf of the International Programme Committee, I am proud to acknowledge and thank the hard work of the members of the Local Organizing- and International Scientific Committees in preparations and implementations for the successful 16’th conference held in Gothenburg and for the third time in Sweden (1997 in Gothenburg and 2003 in Halmstad). It was my privilege and pleasure to welcome you all to the 16th International Conference on Metrology and Properties of Engineering Surfaces in Gothenburg at Hotel Clarion Post.The conference 2017 resulted in four successful days of: 121 delegates, 9 exhibitors, participants from 17 countries and 5 continents, 7 invited speakers, 59 oral presentations, and 28 posters.List of International Programme Committee, International Scientific Committee, Local Organizing Committee are available in this pdf.

3-in-1 X-ray Computed Tomography

For over 30 years, X-ray Computed Tomography (CT) has been used for Non-Destructive Testing (NDT) of manufactured components for validation of internal integrity [1]. More recently the first X-ray CT systems dedicated to dimensional metrology applications have reached the market. Since then, the field of dimensional X-ray CT has gained much interest, especially for inspection of Additively Manufactured (AM) components [2]. This novel manufacturing route has brought new challenges for inspection due to internal or inaccessible features and unique surface characteristics. Recent research has demonstrated the feasibility for surface metrology with commercially available micro-CT systems [3] [4]. The potential for performing dimensional, integrity and surface analysis within a single process has made X-ray CT highly desirable for AM inspection. Further innovation is required however, in order to produce a commercial hardware and software that can complete the complex workflow required for 3-in-1 inspection.

High Resolution Surface Metrology Using Microsphere‐Assisted Interference Microscopy

The authors review some of the latest results of a new high resolution optical metrology technique using small glass microspheres placed on the sample to enhance the lateral resolution in optical microscopy. Experimental results are shown of high resolution 2D images of gratings and microelectronic structures. The results of simulations and experimental measurements for 2D imaging through glass microspheres show an increase in magnification of 3–5 times and a lateral resolution as small as 100 nm in air. Experimental results are also shown of 3D measurements of different nanostructures using microspheres that have successfully been incorporated into Mirau and Linnik type interferometers. Results are shown on grooves in Blu‐Ray discs, narrow etched gratings in Si, nanotextured stainless steel surfaces, and on Ag nanodots. Measurements using SEM and AFM are given for comparison. Some of the artefacts and sources of errors in the microsphere‐assisted measurements are presented and discussed. The authors thus demonstrate that microsphere‐assisted interference microscopy is a promising new optical tool for nanometrology.

Experimental research on tribological properties of liquid phase exfoliated graphene as an additive in SAE 10W-30 lubricating oil

Abstract In this study, the graphene was prepared by liquid phase exfoliation method, and then through microfluidization technique it was uniformly dispersed into SAE 10W-30 lubricating oil. The lubricating oils without graphene and with four different graphene concentrations were tested twice respectively on a pin-on-disc tribometer under high specific pressure of 10 MPa and low linear velocity of 0.3 m/s. After testing, the scratches on discs were observed by scanning electron microscope (SEM) and three-dimensional (3D) surface metrology system. The oil with 0.05 wt% graphene exhibited the minimum friction coefficient, lowest specific wear rate and slightest scratch. The results illustrated that the graphene dispersed into SAE 10W-30 oil with optimum concentration improved the anti-friction and anti-wear performances.

Ultraprecision machining of microlens arrays with integrated on-machine surface metrology.

Microlens arrays (MLAs) are increasingly applied in high-end photonics and imaging systems. Advanced diamond turning machining with tool servo technique is a superior method of fabricating micro-structured arrays with sub-micrometer form accuracy and nanometer surface finish. This paper proposes an innovative framework for ultraprecision machining of MLA. The established metrology-integrated machining platform consists of a 3-axis ultraprecision turning machine and a nanometric interferometric probe. On-machine surface measurement enables the in situ inspection and characterization of MLA features while preserving the consistency between the machining and measurement coordinate. The dedicated surface error characterization method and 3D corrective machining strategy are also presented. An experimental study is carried out in order to prove the proposed MLA characterization's and 3D corrective machining's effectiveness in improving the MLA surface accuracy.

An Isotropic Areal Filter Based on High-Order Thin-Plate Spline for Surface Metrology

Isotropy, end effect suppression, calculation efficiency and robustness are basic requirements of areal filters for surface metrology. However, current areal filters cause problems in different aspects, which cripples the operation of surface metrology like roughness evaluation. In this paper, a high-order thin-plate spline (TPS) filter is proposed to construct a real isotropic areal spline filter with minimum end effects and high efficiency, aiming to provide a more universal and efficient topography filtration method. The new filter is structured by approximating Gaussian filter to ensure uniform transmission characteristics. The robust algorithm is derived to process surface data with outliers and defects. A fast implementation is also provided in this paper. Performances of various areal metrology filters are illustrated by processing both simulated and practical surfaces, through which the proposed high-order TPS filter herein manifests real isotropy, higher calculation efficiency, slighter end effect as well as robustness comparing to current areal surface metrology filters. Comparing with the ISO 16610-61, the new areal filter can obtain more ideal results, therefore it can take the place of ISO 16610-61 on most occasions.

Оптическая 3D-метрология поверхности от компании Mahr

Оптическая 3D-метрология поверхности от компании Mahr

Characterization of surface texture in electropolishing processes using 3D surface topography parameters

Surface engineering requires new technology for the evaluation of surface texture. Profiling methods for the characterization of surface finish do not permit the detailed analysis of surface microgeometry. Thus, advances in the field of surface metrology have led to the development of topographic profilometer systems capable of the three-dimensional topographical reconstruction of real surface texture using phase shift scanning of surfaces, with instruments able to measure microgeometric form, waviness, and roughness, individually or integrated. The innovative three-dimensional evaluation methods, using contact and non-contact technology, enable the virtual reconstruction of surfaces for the evaluation of area roughness parameters, three-dimensional topographic maps with color scale, and profiling of sections in any area of a surface to provide the two-dimensional roughness parameters, among others. In this study a set of 3D surface parameters were analyzed: fractal analysis, area roughness parameters (Sa, Sz, and Spd), and three-dimensional surface topography, in order to determine the information provided by each in the analysis of surface texture. The topographic analysis performed detected deformations on the borders of the workpieces when high electropolishing times and current densities were combined, due to the lack of homogeneity in the elimination of the treated surface material. Finally, this study has determined electropolishing conditions and electrolytic effects on surface texture using the three-dimensional analysis of surface texture.

On-machine and in-process surface metrology for precision manufacturing

On-machine and in-process surface metrology are important for quality control in manufacturing of precision surfaces. The classifications, requirements and tasks of on-machine and in-process surface metrology are addressed. The state-of-the-art on-machine and in-process measurement systems and sensor technologies are presented. Error separation algorithms for removing machine tool errors, which is specially required in on-machine and in-process surface metrology, are overviewed, followed by a discussion on calibration and traceability. Advanced techniques on sampling strategies, measurement systems-machine tools interface, data flow and analysis as well as feedbacks for compensation manufacturing are then demonstrated. Future challenges and developing trends are also discussed.

Engineering fusion spatial modeling to enable areal measurement system analysis for optical surface metrology

Optical surface measurement (OSM) systems are able to reveal local surface variations in detail compared with stylus-based metrology. The major challenges of conducting measurement system analysis (MSA) for such an OSM include inconsistent measurement locations and a lack of characterization of gage capability at local surface areas (areal MSA). In this paper, an improved surface model is proposed to enable areal measurement system analysis for OSM by fusing surface manufacturing process information with spatially correlated data. Case studies discussed the MSA techniques developed from the proposed surface models and compared their performance in characterizing the areal MSA.