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Undercut (etching)
Undercuts from etching (microfabrication) are generally an unwanted side effect, however are sometimes used as a feature such as in the Niemeyer–Dolan technique. Undercuts from etching can occur from two common causes. The first is over etching, which means the etchant was applied too long. The second is due to an isotropic etchant, which means the etchant etches in all directions equally. To overcome this problem an anisotropic Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's phys ... etchant is used.. References Bibliography *{{Citation , last1 = Degarmo , first1 = E. Paul , last2 = Black , first2 = J T. , last3 = Kohser , first3 = Ronald A. , title = Materials and Processes in Manufacturing , publisher = Wiley , year = 2003 , edition = 9th , isbn = 0-471-65653-4. Etchin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Etch Anisotropy
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Etch may refer to: * to carry out an etching process * Etch (protocol), a network protocol * Etch (''Toy Story''), a character from the film ''Toy Story'' * Etch, the codename of version 4.0 of the Debian Linux operating system * East Tennessee Children's Hospital East Tennessee Children's Hospital is a private, independent, not-for-profit, 152-bed pediatric medical center in Knoxville, Tennessee. The hospital's primary service area includes 16 counties in East Tennessee, and its secondary service area in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Etching (microfabrication)
Etching is used in microfabrication to chemically remove layers from the surface of a wafer during manufacturing. Etching is a critically important process module, and every wafer undergoes many etching steps before it is complete. For many etch steps, part of the wafer is protected from the etchant by a "masking" material which resists etching. In some cases, the masking material is a photoresist which has been patterned using photolithography. Other situations require a more durable mask, such as silicon nitride. Orientation-Dependent Etching * KOH pellets dissolved in water (self-heating) * Etch Rate > >> ** KOH has a slower etching orientation for the planes ** You cannot use this KOH photoresist as a etching mask, because the oxide attacks too slowly, so this resist will not survive * Photoresist can be used a etching mask, and the best photoresist for etching is nitride * For example, the etch rate of Si in KOH Depends on Crystallographic Plane * At low temper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Niemeyer–Dolan Technique
The Niemeyer–Dolan technique, also called the Dolan technique, angular evaporation, or the shadow evaporation technique, is a thin-film lithographic method to create nanometer-sized overlapping structures. This technique uses an evaporation mask that is suspended above the substrate (see figure). The evaporation mask can be formed from two or more layers of resist, to allow creation of the extreme undercut needed. Depending on the evaporation angle, the shadow image of the mask is projected onto different positions on the substrate. By carefully choosing the angle for each material to be deposited, adjacent openings in the mask can be projected onto the same spot, creating an overlay of two thin films with a well-defined geometry. Efforts to create multilayered structures are complicated by a need to align each layer with those below it; as all openings are on the same mask, shadow evaporation reduces this need by being self-aligning. Additionally, this allows the substrate to b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Milling
Chemical milling or industrial etching is the subtractive manufacturing process of using baths of temperature-regulated etching chemicals to remove material to create an object with the desired shape. Other names for chemical etching include photo etching, chemical etching, photo chemical etching and photochemical machining. It is mostly used on metals, though other materials are increasingly important. It was developed from armor-decorating and printing etching processes developed during the Renaissance as alternatives to engraving on metal. The process essentially involves bathing the cutting areas in a corrosive chemical known as an etchant, which reacts with the material in the area to be cut and causes the solid material to be dissolved; inert substances known as maskants are used to protect specific areas of the material as resists. History Organic chemicals such as lactic acid and citric acid have been used to etch metals and create products as early as 400 BCE, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotropic
Isotropy is uniformity in all orientations; it is derived . Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence '' anisotropy''. ''Anisotropy'' is also used to describe situations where properties vary systematically, dependent on direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. Mathematics Within mathematics, ''isotropy'' has a few different meanings: ; Isotropic manifolds: A manifold is isotropic if the geometry on the manifold is the same regardless of direction. A similar concept is homogeneity. ; Isotropic quadratic form: A quadratic form ''q'' is said to be isotropic if there is a non-zero vector ''v'' such that ; such a ''v'' is an isotropic vector or null vector. In complex geometry, a line through the origin in the direction of an isotropic vect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anisotropic
Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physical or mechanical properties ( absorbance, refractive index, conductivity, tensile strength, etc.). An example of anisotropy is light coming through a polarizer. Another is wood, which is easier to split along its grain than across it. Fields of interest Computer graphics In the field of computer graphics, an anisotropic surface changes in appearance as it rotates about its geometric normal, as is the case with velvet. Anisotropic filtering (AF) is a method of enhancing the image quality of textures on surfaces that are far away and steeply angled with respect to the point of view. Older techniques, such as bilinear and trilinear filtering, do not take into account the angle a surface is viewed from, which can result in ali ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
