Jozefien Goossens

High depth resolution analysis of Si/SiGe multilayers with the atom probe

The laser assisted atom probe has been proposed as a metrology tool for next generation semiconductor technologies requiring subnanometer depth resolution. In order to support its routine application, we carried out a quantitative assessment of the performance of the atom probe on semiconductor stacks. We analyzed a silicon, silicon-germanium multilayer-structure with atom-probe tomography (APT), secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM), and high-resolution x-ray diffraction (HRXRD). We demonstrate that APT outperforms SIMS by a factor of 3 in terms of depth-resolution providing a decay length of 0.2–0.6 nm/decade whereas the compositions and layer thicknesses are in close agreement with SIMS, HRXRD, and TEM.

Experimental studies of dose retention and activation in fin field-effect-transistor-based structures

With emerging three-dimensional device architectures for advanced silicon devices such as fin field-effect-transistors (FinFETs), new metrology challenges are faced to characterize dopants. The ratio of dopant concentration in the top surface and sidewalls of FinFETs may differ significantly, thereby influencing the performance of these devices. In this work, a methodology involving secondary ion mass spectrometry (SIMS) is presented to study the dose conformality in fins. However, SIMS is limited to probe the quantitative chemical dopant concentration (i.e., top/sidewall of fins). The fraction of the active dopant concentration determining the performance of FinFETs would still be unknown. Additionally, the concept based on SIMS is unable to provide information on the lateral junction depth. Thus, to obtain the unknown active dopant concentration and their spatial distribution, the authors extend their study by measuring the cross section of the fins with scanning spreading resistance microscopy and extracting the quantitative active carrier concentration in the fins.With emerging three-dimensional device architectures for advanced silicon devices such as fin field-effect-transistors (FinFETs), new metrology challenges are faced to characterize dopants. The ratio of dopant concentration in the top surface and sidewalls of FinFETs may differ significantly, thereby influencing the performance of these devices. In this work, a methodology involving secondary ion mass spectrometry (SIMS) is presented to study the dose conformality in fins. However, SIMS is limited to probe the quantitative chemical dopant concentration (i.e., top/sidewall of fins). The fraction of the active dopant concentration determining the performance of FinFETs would still be unknown. Additionally, the concept based on SIMS is unable to provide information on the lateral junction depth. Thus, to obtain the unknown active dopant concentration and their spatial distribution, the authors extend their study by measuring the cross section of the fins with scanning spreading resistance microscopy and extr...

Shear properties of glycerol by interface wave laser ultrasonics

Acoustic waves at the interface between a polymeric solid and a glass-forming liquid are studied through impulsive stimulated thermal scattering (ISTS), a photoacoustic method. The transverse character of the interface waves provides a unique window into the shear relaxation dynamics of supercooled liquids. Real and imaginary parts of the shear modulus of glycerol are extracted as functions of temperature and acoustic frequency. Extension of ISTS to interface waves permits characterization of shear dynamics even under conditions of very strong acoustic damping which preclude more conventional ultrasonic methods.

Laser-based surface acoustic wave dispersion spectroscopy for extraction of thicknesses, depth, and elastic parameters of a subsurface layer: Feasibility study on intermetallic layer structure in integrated circuit solder joint

Laser beam deflection in combination with optical heterodyne diffraction is used to detect surface acoustic waves that are generated by impulsive laser light on a Sn–CuxSny–Cu–Si multilayer structure with layer thicknesses of the order of 1 μm. The acoustic phase velocity dispersion curves of the lowest two-surface acoustic wave modes are determined by spectral analysis of the experimental signals. The sensitivity of the dispersive behavior to the thickness and elastic properties of the individual layers is analyzed on the basis of the experimental data and of simulated data with noise added. The elastic parameters of the CuxSny intermetallic alloy are determined. Statistical least squares and most squares uncertainties on all best fitting material parameters are determined, giving a quantitative measure of the feasibility of parameter extraction by this method. The feasibility of solving the inverse problem of elastic depth profiling of a multilayer by the proposed wideband and multimode SAW dispersion s...

High precision micro-scale Hall effect characterization method using in-line micro four-point probes

Accurate characterization of ultra shallow junctions (USJ) is important in order to understand the principles of junction formation and to develop the appropriate implant and annealing technologies. We investigate the capabilities of a new micro-scale Hall effect measurement method where Hall effect is measured with collinear micro four-point probes (M4PP). We derive the sensitivity to electrode position errors and describe a position error suppression method to enable rapid reliable Hall effect measurements with just two measurement points. We show with both Monte Carlo simulations and experimental measurements, that the repeatability of a micro-scale Hall effect measurement is better than 1 %. We demonstrate the ability to spatially resolve Hall effect on micro-scale by characterization of an USJ with a single laser stripe anneal. The micro sheet resistance variations resulting from a spatially inhomogeneous anneal temperature are found to be directly correlated to the degree of dopant activation.

Micro-uniformity during laser anneal: metrology and physics

Maintaining or improving device performance while scaling semiconductor devices, necessitates the development of extremely shallow ( In this work we use optimized metrology to probe such macro- and micro non-uniformity and determine the origin of the various components contributing to the observed non-uniformity patterns (laser stitching patterns, laser beam uniformity, optical path) and their impact on the local sheet resistance.

Effect of loading a plate with different liquids on the propagation of lamb-like waves studied by laser ultrasonics

Three experimental laser ultrasonic configurations-line excitation with scanning detection, grating excitation with single point detection, and grating excitation with scanning probe beam- are shown to consistently reveal the modified propagation properties of Lamb waves on a polyethylene terephthalate (PET) film that is in contact with different liquids on its two sides. Theoretical predictions concerning the physical nature of different wave modes in symmetric and asymmetric film loading configurations (i.e., their existence, velocity, damping, and polarization) are confirmed by the experimental results.

Surface acoustic wave depth profiling of a functionally graded material

The potential and limitations of Rayleigh wave spectroscopy to characterize the elastic depth profile of heterogeneous functional gradient materials are investigated by comparing simulations of the surface acoustic wave dispersion curves of different profile-spectrum pairs. This inverse problem is shown to be quite ill posed. The method is then applied to extract information on the depth structure of a glass-ceramic (alumina) functionally graded material from experimental data. The surface acoustic wave analysis suggests the presence of a uniform coating region consisting of a mixture of Al2O3 and glass, with a sharp transition between the coating and the substrate. This is confirmed by scanning electron microscope with energy dispersive x-ray analysis.

Advanced 2D/3D simulations for laser annealed device using an atomistic kinetic Monte Carlo approach and Scanning Spreading Resistance Microscopy (SSRM)

Atomistic modeling and optimized TCAD simulation strategy for Laser-only annealing device are shown. Multiple laser annealing scans are modeled by using atomistic KMC. KMC clarified that dopant diffusion is changed as a function of laser scan number. SSRM with 1 nm special resolution is used for the 2-dimensional carrier distribution measurement and dopant active level determination. It is shown that 2D profile mapping using SSRM is useful in TCAD simulations.

Impact of multiple sub-melt laser scans on the activation and diffusion of shallow Boron junctions

Sub-melt laser annealing is a promising technique to achieve the required sheet resistance and junction depth specifications for the 32 nm technology node and beyond. In order to obtain a production worthy process with minimal sheet resistance variation at a macroscopic and microscopic level, careful process optimization is required. While macroscopic variations can easily be addressed using the proper spatial power compensation it is more difficult to completely eliminate the micro scale non-uniformity which is intimately linked to the laser beam profile, the amount of overlaps and the scan pitch. In this work, we will present micro scale sheet resistance uniformity measurements for shallow 0.5 keV B junctions and zoom in on the underlying effect of multiple subsequent laser scans. A variety of characterization techniques are used to extract the relevant junction parameters and the role of different implantation and anneal parameters will be explored. It turns out that the observed sheet resistance decrease with increasing number of laser scans is caused on one hand by a temperature dependent increase of the activation level, and on the other hand, by a non-negligible temperature and concentration dependent diffusion component.