Ingeniería Mecatrónica (Mag.)

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Implementation of a four probes measuring system to determine the resistivity of thin films with temperature dependence
(Pontificia Universidad Católica del Perú, 2017-06-19) Salas Casapino, Carlos Alberto; Guerra Torres, Jorge Andrés; Ströhla, Tom
Resistivity measurements in thin film samples depending on the temperature and on the lm thickness is always a subject of interest, above all when it comes to new materials. This work presents the implementation of a measuring system for thin fi lm resistivity based on four probes showing the dependency of the resistivity on the temperature as well as on the film thickness. In order to change the temperature of the samples, a heat source based on a Peltier element was implemented into the measuring system. A Graphical User Interface using a LabVIEW software controls all the devices of the measuring system and allows the user to calculate the thin lm resistivity choosing between four measuring method: Van der Pauw, Modi ed Van der Pauw, Linear Van der Pauw and Linear Four Probes methods. Resistivity in aluminum and tungsten thin lm samples with 100, 300, and 600 nm thickness were measured at temperatures between 303K and 373K with increments of 5 K. The results obtained are higher than bulk resistivity values and agrees with the present theory. Moreover, it is shown that the resistivity values obtained and its corresponding temperature coeficients increases as the film thickness decreases.
FEM simulation of residual stresses of thin films for applications in MEMS
(Pontificia Universidad Católica del Perú, 2017-06-19) Macavilca Román, José Carlos; Ströhla, Tom; Rumiche Zapata, Francisco Aurelio
In MEMS sensors, such as resonators based on cantilever and doubly-clamped beams, the presence of residual stresses in the thin films disrupt their mechanical properties or eigenfrequencies and, in some cases, can destroy the structure. This thesis aims to simulate the residual stresses in wafers composed of thin films deposited over a substrate. The simulations were conducted with ANSYS Workbench R17.2, a finiteelement-method software. This work considered static simulations with a single-layer wafer geometry, since it is a first approach to the simulation of residual stresses. With the purpose of achieving that, three simulation types were performed. Simulation 1 applied the thermal loads as heating and cooling steps to a quadrant model. Simulation 2 added the birth and death technique with the purpose of representing the deposition of the thin film. Besides, it was split under the geometric model as flat axisymmetric section, curved axisymmetric section, i.e. with the initial curvature of the wafer, and curved quadrant model. On the other hand, simulation 3 generated the residual stresses by the activation of the contact between the thin film and the silicon dioxide layer, used as diffusive barrier. The simulation results were compared to calculated values from measurements performed by the methods of wafer curvature and X-ray diffraction. The comparison showed that the curved quadrant model allowed obtaining residual stresses and deflections closer to the calculated ones. In addition, the curved axisymmetric models allowed visualizing the residual stresses distribution in the layers and the substrate. Thus, the birth and death technique was useful to simulate the deposition of the thin film. The considerations described in this work can be used as input data for more complex simulations based on MEMS structures
Construction and implementation of a 4-probe measuring system to determinate the temperature dependent sheet resistance of thin films
(Pontificia Universidad Católica del Perú, 2017-04-12) Pacheco Arenas, Carlos Arturo; Ströhla, Tom; Rumiche Zapata, Francisco Aurelio
In order to build machines, electronic devices, it is necessary to know all properties of the materials. The machines and electronic devices use parts that are interconnected, the mechanical properties are important, but for some specific tasks the electrical properties are more important. In this sense it is necessary to predict the behavior of this parts in different temperatures to the environment. The present thesis focus on implementation of a 4-probe measuring system to determinate the sheet resistance of thin film samples showing the dependency of the resistivity on the film thickness as well as on the deposition temperature. The method used to determine the resistivity is the modified van der Pauw Method. Therefore, it is important the measurement of the current and the voltage drop in the sample. It is also important to measure the distance between tips, in order to calculate the resistivity. Furthermore, it is also important to find the correct transformation that maps any four point of a plane to a new plane with four collinear points. The measurements are controlled via LabVIEW and the measured data is displayed in the user interface.

Ingeniería Mecatrónica (Mag.)

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