Etching of Uncompensated Convex Corners with Sides along <n10> and <100> in 25 wt% TMAH at 80 °C

This paper presents etching of convex corners with sides along and crystallographic directions in a 25 wt% tetramethylammonium hydroxide (TMAH) water solution at 80 °C. We analyzed parallelograms as the mask patterns for anisotropic wet etching of Si (100). The sides of the parallelograms were designed along and crystallographic directions (1 and crystallographic directions were smaller than 45°. All the crystallographic planes that appeared during etching in the experiment were determined. We found that the obtained types of 3D silicon shape sustain when n > 2. The convex corners were not distorted during etching. Therefore, no convex corner compensation is necessary. We fabricated three matrices of parallelograms with sides along crystallographic directions and as examples for possible applications. Additionally, the etching of matrices was simulated by the level set method. We obtained a good agreement between experiments and simulations

Etched Parallelogram Patterns with Sides Along <100> and <n10> Directions in 25 wt % TMAH

In this paper, we present and analyze etching of parallelogram patterns in the masking layer on a (100) silicon in 25 wt % TMAH water solution at the temperature of 80 0C. Sides of parallelogram islands in the masking layer are designed along and crystallographic directions. A 3D simulation of the profile evolution from these patterns during etching of silicon using the level set method is also presented. We determined all crystallographic planes that appear during etching in the experiment and obtained simulated etching profiles of these 3D structures. A good agreement between dominant crystallographic planes through experiments and simulations is obtained

Kontrolisan raspored integrisanih prepreka u silicijumskim mikrokanalima nagrizanim u 25 mas.% rastvoru tetrametilamonijum hidroksida

In this paper, fabrication of silicon microchannels with integrated obstacles by using 25 wt.% tetramethylammonium hydroxide (TMAH) aqueous solution at the temperature of 80 C is presented and analysed. We studied basic island patterns, which present union of two symmetrical parallelograms with the sides along predetermined crystallographic directions (2. Acute angles of the parallelograms were smaller than 45o. We have derived analytical relations for determining dimensions of the integrated obstacles. The developed etching technique provides reduction of the distance between the obstacles. Before the experiments, we performed simulations of pattern etching based on the level set method and presented evolution of the etched basic patterns for the predetermined crystallographic directions . Combination of basic patterns with sides along the and crystallographic directions is used to fabricate a matrix of two row of silicon obstacles in a microchannel. We obtained a good agreement between the experimental results and simulations. Our results enable simple and cost-effective fabrication of various complex microfluidic silicon platforms with integrated obstacles.U ovom radu je prezentovana i analizirana izrada silicijumskih mikrokanala sa integrisanim preprekama u vodenom rastvoru 25 mas.% tetrametilamonijum hidroksida (TMAH) na temperaturi od 80 oC. Proučavani su osnovni oblici maski koji predstavljaju uniju dva simetrična ostrva u obliku paralelograma čije su stranice duž unapred određenih kristalografskih pravaca (2. Oštri uglovi paralelograma su manji od 45˚. Izvedene su formule za izračunavanje dimenzija integrisanih prepreka. Razvijena je tehnika nagrizanja koja smanjuje rastojanje između prepreka. Pre eksperimenata izvršene su simulacije osnovnih oblika koje se baziraju na metodi implicitno definisanih nivoa (engl. level set method). Prezentovan je razvoj nagrizanih osnovnih oblika maski za unapred određene kristalografske pravce . Kombinacija osnovnih oblika maski čije su stranice duž kristalografskih pravaca i je iskorišćena za izradu dva reda matrice silicijumskih prepreka u mikrokanalu. Dobijeno je dobro slaganje između eksperimenata i simulacija. Dobijeni rezultati omogućavaju jednostavnu i jeftinu izradu različitih kompleksnih mikrofluidnih silicijumskih platformi sa integrisanim preprekama

Particle-in-cell simulations of rf breakdown

Breakdown voltages of a capacitively coupled radio frequency argon discharge at 27 MHz are studied. We use a one-dimensional electrostatic PIC code to investigate the effect of changing the secondary emission properties of the electrodes on the breakdown voltage, particularly at low pd values. Simulation results are compared with the available experimental results and a satisfactory agreement is found.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

An analytical relation describing the dramatic reduction of the breakdown voltage for the microgap devices

The field-emission–related effects play a significant role in the deviation of the breakdown voltage from that predicted by Paschen's law in the range of micrometer gaps. Beginning from a certain gap spacing, breakdown voltage diverges from the climbing curve seen in the left half of the Paschen curve. In this paper, the equation governing the DC breakdown in microgaps has been solved analytically. The derived analytical relation indicates that the DC breakdown voltage in microgaps depends on the gap size d and the pressure p, particularly, rather than on the product pd. The new theoretical expression allows key features to be identified suggesting that the inclusion of the field emission at micron and submicron gaps is necessary to describe properly the experimental data. The expression presented here can receive a wider interest due to its applicability to the breakdown voltage for a series of gases, gaps and pressures and can serve as ready-to-use guidelines for system engineers and designers

Finite element analysis of the effect of microwave ablation on the liver, lung, kidney, and bone malignant tissues

Microwave ablation becomes a promising thermal modality for treating cancerous tumor cells in patients who are non-surgical candidates. To ensure the destruction of cancer cells with minimal damage to healthy tissue, the elevation of temperature and the evolution of the necrotic tissue need to be controlled. Besides experimental methods, computer modeling evolves into a powerful approach for improving the performance of the ablative treatment. This letter reports on the numerical studies of the microwave ablation effect on the liver, lung, kidney, and bone tumoral tissues. Calculations were performed by using the COMSOL Multiphysic based on a multi-component plasma fluid model. Simulation conditions include the microwave frequency of ${\rm 2.45\, GHz}$ , the input power of ${\rm 10\,W}$ , and taking into account the temperature dependence of dielectric properties of the tissue. The total loss power density, the temperature distribution, the fraction of the tissue damage, and the specific absorption rate have been determined. It was shown that the temperature distribution has an ellipsoidal shape reaching the maximal values required for effective cancer treatment but to avoid damaging healthy cells near the antenna slot. From the degree of tissue injury, the fraction of damage has been estimated revealing that the microwave ablation zones are concentrated around the tip and slot of the antenna. Also, the ablation of the tumor cells can be achieved over a long period without damaging healthy cells when small input power is used. The obtained results confirm that simulations can be very useful for predicting optimal conditions for the minimal damage of the healthy tissue during microwave ablation, and therefore may be implemented into treatment planning

Three-Dimensional Simulations of the Anisotropic Etching Profile Evolution for Producing Nanoscale Devices

Refined control of etched profiles is one of the most important tasks of micro (nano) electro mechanical systems manufacturing process. In spite of its wide use, the simulation of etching for micro (nano) electro mechanical systems applications has been so far a partial success only, although a great number of commercial and academic research tools dedicated to this problem are developed. In this paper we describe an application of the sparse field method for solving level set equations in 3D anisotropic wet etching of silicon with potassium hydroxide (KOH). Angular dependence of the silicon etching rate is determined on the basis of the silicon crystal symmetry properties. Some examples illustrating developed methodology are given

Breakdown Phenomena in Water Vapor Microdischarges

The gas breakdown at the large gap sizes is reasonably well understood. However, the breakdown phenomenon in microgaps is still not sufficiently explored. The high electric fields realized in small gaps combined with the lowering of the potential barrier, seen by the electrons in the cathode as ion approaches lead to ion-enhanced field emission leading to deviations from the standard Paschen law. In this paper, semi-empirical expressions for the breakdown voltage based on the fitting of numerical solutions of the DC breakdown criteria in microdsicharges have been derived. In the standard breakdown criteria the secondary emission coefficient that incorporates the enhancement of the secondary electron emission has been included. The obtained expressions can be used for determination the pressure and the gap dependence of the breakdown field strength in the water vapor, separately

Microwave field strength computing for the resonator designs and filters

Recent development of microwave pulse generators, which are now capable of delivering very short and very intensive pulses requires properly generalized classical breakdown theory. On the other hand, the trend to design microwave devices as small and compact as possible, leads to a concern about the concomitant breakdown strength of the construction, involving more complicated geometries, such as in microwave resonators and filters. In this paper, several aspects of microwave breakdown field strength in commercially available resonator designs and filters are presented and analyzed. The numerical predictions based on the Slater theorem are compared with the analytical results and predictions of the fluid approach, demonstrating very good agreement