The black silicon method: a universal method for determining the parameter setting of a fluorine-based reactive ion etcher in deep silicon trench etching with profile control

Very deep trenches (up to 200 µm) with high aspect ratios (up to 10) in silicon and polymers are etched using a fluorine-based plasma (SF6/O2/CHF3). Isotropic, positively and negatively (i.e. reverse) tapered as well as fully vertical walls with smooth surfaces are achieved by controlling the plasma chemistry. A convenient way to find the processing conditions needed for a vertical wall is described: the black silicon method. This new procedure is checked for three different reactive ion etchers (RIE), two parallel-plate reactors and a hexode. The influence of the RF power, pressure and gas mixture on the profile will be shown. Scanning electron microscope (SEM) photos are included to demonstrate the black silicon method, the influence of the gases on the profile, and the use of this method in fabricating microelectromechanical systems (MEMS)

Novel Cooling Strategy for Electronic Packages: Directly Injected Cooling

This publication discusses domain integration of various engineering disciplines as an effective methodology to design new and innovative products. A case study illustrates how this approach is applied to the design process of a high performance electronic product. A novel and improved method for the cooling of electronic packages is presented. Standard package types, as for instance ball grid arrays, are equipped with directly injected cooling. The developed design is a very cost effective solution, as fewer productions steps and fewer procured parts are required compared to traditional cooling. The new design is also easily scalable, as multiple components on an electronic product can be cooled both uniformly and simultaneously. This allows for more overall design flexibility, which can result in a more integrated product design with advantages in terms of performance, volume, weight and production efficiency

Electrostatic microactuators with integrated gear linkages for mechanical power transmission

In this paper a surface micromachining process is presented which has been used to fabricate electrostatic microactuators that are interconnected with each other and linked to other movable microstructures by integrated gear linkages. The gear linkages consist of rotational and linear gear structures and the electrostatic microactuators include curved electrode actuators, comb drive actuators and axial gap wobble motors. The micromechanical structures are constructed from polysilicon. Silicon dioxide has been used as a sacrificial layer and silicon nitride was used for electrical insulation. A cyclohexane freeze drying technique is used to prevent problems with stiction. The actuators, loaded with various mechanisms, have been driven successfully by electrostatic actuation. The work is a first step towards mechanical power transmission in micromechanical system

3-D coupled electric mechanics for MEMS: Applications of COSOLVE-EM

Micro-electro-mechanical systems (MEMS) are often designed on scales at which electrostatic forces are capable of moving or deforming the parts of the system. In this regime accurate prediction of device behavior may require 3D coupled simulations between the electrostatic and mechanical domains. We have recently developed CoSolve-EM, a coupled solver for 3D quasi-static electro-mechanics. In this paper, we demonstrate the application of CoSolve-EM to five classes of electro-mechanical problems that are often intractable to other techniques. These classes are: devices with electrostatic pull-in instabilities, devices in which precise deformations are required, devices driven by multiple conductors, capacitive sensors that make use of surface contact, and actuators that make use of surface contact

Nonlinearity and hysteresis of resonant strain gauges

Nonlinearity and hysteresis effects of electrostatically activated, voltage driven resonant microbridges have been studied theoretically and experimentally. It is shown, that, in order to avoid vibration instability and hysteresis to occur, the choices of the ax. and d.c. driving voltages and of the quality factor of a resonator, with a given geometry and choice of materials, are limited by a hysteresis criterion. The limiting conditions are also formulated as hysteresis-free design rules. An expression for the maximum attainable figure of merit is also given. Experimental results, as obtained from electrostatically driven vacuum-encapsulated polysilicon microbridges, are presented and show good agreement with the theory

Anisotropic reactive ion etching of silicon using SF₆/O₂/CHF₃ gas mixtures

Reactive ion etching of silicon in an RF parallel plate system, using SF6/O2/CHF3, plasmas has been studied. Etching behavior was found to be a function of loading, the cathode material, and the mask material. Good results with respect to reproducibility and uniformity have been obtained by using silicon as the cathode material and silicon dioxide as the masking material for mask designs where most of the surface is etched. Etch rate, selectivity, anisotropy, and self-bias voltage have been examined as a function of SF6 flow, O2 flow, CHF3 flow, pressure, and the RF power, using response surface methodology, in order to optimize anisotropic etching conditions. The effects of the variables on the measured responses are discussed. The anisotropic etch mechanism is based on ion-enhanced inhibitor etching. SF6 provides the reactive neutral etching species, O2 supplies the inhibitor film forming species, and SF6 and CHF3 generate ion species that suppress the formation of the inhibitor film at horizontal surfaces. Anisotropic etching of high aspect ratio structures with smooth etch surfaces has been achieved. The technique is applied to the fabrication of three-dimensional micromechanical structures

Modeling printed circuit board curvature in relation to manufacturing process steps

This paper presents an analytical method to predict deformations of Printed Circuit Boards (PCBs) in relation to their manufacturing process steps. Classical Lamination Theory (CLT) is used as a basis. The model tracks internal stresses and includes the results of subsequent production steps, such as bonding, multilayer press cycles and patterning processes. The aim of this research is to develop a model that can be applied to predict laminate deformations in the production of complex PCBs. Initial experimental results of simplified test specimens show that the modeling approach is valid and capable of accurately predicting laminate deformations for standard bi-layer bonding and multiple press cycles. In the future, the evolved model can be used to analyze PCB manufacturing processes and optimize PCB desig