Jose M. Carballo

Growth Rate Effect on 3C-SiC Film Residual Stress on (100) Si Substrates

SiC is a candidate material for micro- and nano-electromechanical systems (MEMS and NEMS). In order to understand the impact that the growth rate has on the residual stress of CVD-grown 3C-SiC hetero-epitaxial films on Si substrates, growth experiments were performed and the resulting stress was evaluated. Film growth was performed using a two-step growth process with propane and silane as the C and Si precursors in hydrogen carrier gas. The film thickness was held constant at ~2.5 µm independent of the growth rate so as to allow for direct films comparison as a function of the growth rate. Supported by profilometry, Raman and XRD analysis, this study shows that the growth rate is a fundamental parameter for low-defect and low-stress hetero-epitaxial growth process of 3C-SiC on Si substrates. XRD (rocking curve analysis) and Raman spectroscopy show that the crystal quality of the films increases with decreasing growth rate. From curvature measurements, the average residual stress within the layer using the modified Stoney’s equation was calculated. The results show that the films are under compressive stress and the calculated residual stress also increases with growth rate, from -0.78 GPa to -1.11 GPa for 3C-SiC films grown at 2.45 and 4 µm/h, respectively.

Micro-Scale Part Manipulation on a Liquid Interface Through Interface Curvature Effects

Microscale assembly has many factors that limit assembly rates [1]. At this scale, capillary interactions between particles and nearby substrates are significant, and can be utilized for controlling assembly processes [2,3]. Typically these assembly processes involve direct capillary bonding, but lateral capillary forces can also be applied to floating parts by changing the local curvature of the fluid interface [4]. In this work, we introduce some basic concepts of a microscale component integration system that utilizes local changes in the fluid interface curvature to manipulate floating prismatic parts. Two approaches for achieving fluidic micro-integration, on a water-oil interface, are proposed. The first technique is intended to individually acquire, re-position and release floating parts. It has the capability of short distance part translation/orientation. The second technique provides long-distance part conveying.Copyright

Self-Assembly Kinetics of Microscale Components: A Parametric Evaluation

At the microscale, assembly by grasp and release is challenging. Self-assembly (SA) is an alternative component assembly method to significantly reduce assembly equipment costs. However, successful application of SA requires high assembly rates and high yield (few process errors). Prior modeling efforts describe SA process performance (yield and rate) for specific system configurations, but they do not use measurable process parameters and provide limited ability to predict the impact of process changes. In this paper, an experimental SA system was designed that controls process parameters independently while measuring SA outcomes. This system is used to evaluate a simple parameterization model for SA rate. The travel direction of the parts is varied to measure the path dependence of the assembly probability in the limit of low-impact velocity. Moreover, effects from changing part geometry are evaluated and accounted for in the model. Experimental results show a strong part-geometry dependence and minimal dependence on part arrival angle. This information is a key step toward a parametric kinetic model of capillary SA and complements previous SA process modeling efforts.

Study of Part-Site Interactions in Microscale Capillary Self Assembly

Most common microscale assembly strategies are serial based, such as robotic grasp-and-release systems. Regardless of their high cost and limited throughput, these systems are well developed and thus are easily commercialized [1]. Self-assembly (SA) is a parallel process that, when adapted to microscale, offers high throughput. Furthermore, SA eliminates the need for expensive tooling [2–4]. Yet the lack of SA process knowledge hinders its commercial implementation.Copyright

Experimental Testing of Micro-Scale Self Assembly Process Model

Self assembly holds potential as a more efficient mass-production tool for integration of micro and nano-scaled devices, than traditional pick-and-place methods. While there has been significant innovation in self-assembly demonstrations, less progress has been made on models to predict the relationship between process rates and yields and key process parameters. This work is meant to gather experimental data on capillary self assembly process for micrometer scaled devices, using a controlled experimental assembly system. The purpose is to identify appropriate process variables that can be used to characterize self-assembly processes. Candidate process variables include kinetic energy, angle of impact, surface binding energy, shape and size of surfaces, and fraction area of assembly. Significant improvements to the previously reported self assembly test system are shown. While the experimental techniques continue to be refined, empirical relations are shown for various angles of impact, with fixed kinetic and binding energy values.Copyright