Mechanics of Ultra-sensitive Nanoelectromechanical Silicon Cantilevers: A Combined Experimental-Theoretical Approach

Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin

EUV blank defect and particle inspection with high throughput immersion AFM with 1nm 3D resolution

Inspection of EUV mask substrates and blanks is demanding. We envision this is a good target application for massively parallel Atomic Force Microscopy (AFM). We envision to do a full surface characterization of EUV masks with AFM enabling 1nm true 3D resolution over the entire surface. The limiting factor to do this is in the sensor itself: throughput is limited by the time that a cantilever needs to adjust its oscillation amplitude to the surface topography while scanning. We propose to use heavily damped cantilevers to maximize the measurement bandwidth. We show that using up to 20.000 cantilevers in parallel we can then reach a throughput of one 152×152mm2 substrate per 2 days with 1nm resolution

Report on the Enabling Technology Programme Optomechatronics

The last four years the research Programme Optomechatronics focused on the development of new key technologies for manufacturing and testing equipment and scientific instrumentation. The challenge is to develop instruments with higher accuracy, less costs and higher throughput than we can achieve today. This is relevant for developing the next generation semiconductor equipment, for space and scientific instruments and for improving manufacturing equipment. Four research lines were conducted contributing to capabilities beyond conventional instruments and equipment

Study on the size dependent effective Young modulus by EPI method based on modified couple stress theory

\u3cp\u3eVarious experimental and theoretical researches have been shown the size-dependence behavior of the effective Young modulus (EYM) in the micron and sub-micron scales. One of the most accurate methods is the electrostatic pull-in instability (EPI) method that is based on the bending of the classical beam under the electrostatic force. In this paper, the modified couple stress theory (MCST) is employed to calculate the EYM of silicon nanocantilevers. The MCST compensates the inability of the classical continuum mechanic to predicting the size-dependent behavior of the nano-scale structures. Next, as a case study the EYM of silicon nanocantilevers have been calculated and results compared with classical EPI. The governing equation is solved by the Galerkin method and obtained results show significant size-dependent behavior in the EYM. From the other hand, a new value for the material length scale parameter is introduced based on the dimension of the crystal or grain size of the material.\u3c/p\u3

Automatic alignment of optical beam deflection system for AFM cantilevers

The optical beam deflection (OBD) technique is used in many Atomic Force Microscopes to measure the motion of a cantilever as it probes the scanned surface. From the measured rotation, surface and sub-surface properties of the sample can be deduced. To maximize the sensitivity of the measurement, the combination of laser and cantilever should be aligned such that the laser impinges on the cantilever as close to its end tip as possible. Table-top AFM systems often use manual alignment. For industrial applications automatic alignment is necessary. This paper describes a method to automate this alignment procedure, using a laser induced thermo-mechanical response to actively bend the cantilever. This method also has applications in the characterization of bi-material cantilevers in a non-contact and non-destructive manner. The details of this characterization and the mathematical derivation are published elsewhere

Phase lag deduced information in photo-thermal actuation for nano-mechanical systems characterization

In photo-thermal actuation, heat is added locally to a micro-cantilever by means of a laser. A fraction of the irradiation is absorbed, yielding thermal stresses and deformations in the structure. Harmonic modulation of the laser power causes the cantilever to oscillate. Moreover, a phase lag is introduced which is very sensitive to the spot location and the cantilever properties. This phase lag is theoretically predicted and experimentally verified. Combined with thermo-mechanical properties of the cantilever and its geometry, the location of the laser spot, the thermal diffusivity, and the layer thicknesses of the cantilever can be extracted.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin

Transient Tip-Sample Interactions in High-Speed AFM Imaging of 3D nano structures

The maximum amount of repulsive force applied to the surface plays a very important role in damage of tip or sample in Atomic Force Microscopy(AFM). So far, many investigations have focused on peak repulsive forces in tapping mode AFM in steady state conditions. However, it is known that AFM could be more damaging in transient conditions. In high-speed scanning, and in presence of 3D nano structures (such as FinFET), the changes in topography appear in time intervals shorter than the response time of the cantilever. In this case, the tip may crush into the sample by exerting much higher forces than for the same cantilever-sample distance in steady state situations.In this study the effects of steep upward steps in topography on the tip-sample interactions have been investigated, and it has been found that the order(s) of magnitude higher forces can be applied. The information on the worst case scenario obtained by this method can be used for selection of operation parameters and probe design to minimize damage in high-speed imaging. The numerically obtained results have been verified with the previous works in steady state regime. Based on this investigation the maximum safe scanning speed has been obtained for a case study

Image-based overlay and alignment metrology through optically opaque media with sub-surface probe microscopy

\u3cp\u3eNondestructive subsurface nanoimaging through optically opaque media is considered to be extremely challenging and is essential for several semiconductor metrology applications including overlay and alignment and buried void and defect characterization. The current key challenge in overlay and alignment is the measurement of targets that are covered by optically opaque layers. Moreover, with the device dimensions moving to the smaller nodes and the issue of the so-called loading effect causing offsets between between targets and product features, it is increasingly desirable to perform alignment and overlay on product features or so-called on-cell overlay, which requires higher lateral resolution than optical methods can provide. Our recently developed technique known as SubSurface Ultrasonic Resonance Force Microscopy (SSURFM) has shown the capability for high-resolution imaging of structures below a surface based on (visco-)elasticity of the constituent materials and as such is a promising technique to perform overlay and alignment with high resolution in upcoming production nodes. In this paper, we describe the developed SSURFM technique and the experimental results on imaging buried features through various layers and the ability to detect objects with resolution below 10 nm. In summary, the experimental results show that the SSURFM is a potential solution for on-cell overlay and alignment as well as detecting buried defects or voids and generally metrology through optically opaque layers.\u3c/p\u3

Non-contact distance measurement and profilometry using thermal near-field radiation towards a high resolution inspection and metrology solution

Optical near-field technologies such as solid immersion lenses and hyperlenses are candidate solutions for high resolution and high throughput wafer inspection and metrology for the next technology nodes. Besides sub-diffraction limited optical performance, these concepts share the necessity of extreme proximity to the sample at distances that are measured in tens of nanometers. For the instrument this poses two major challenges: 1) how to measure the distance to the sample? and 2) how to position accurately and at high speed? For the first challenge near-field thermal radiation is proposed as a mechanism for an integrated distance sensor (patent pending). This sensor is realized by making a sensitive calorimeter (accuracy of 2:31nW root sum squared). When used for distance measurement an equivalent uncertainty of 1nm can be achieved for distances smaller than 100 nm. By scanning the distance sensor over the sample, thermal profilometry is realized, which can be used to inspect surfaces in a non-intrusive and non-contact way. This reduces wear of the probe and minimizes the likelihood of damaging the sample.Structural Optimization and Mechanic