Here, the front and back faces of the section have been swapped, which results in the section displayed on the page being flipped:Ģ. The initial dimensions of the section on the page are determined by the size of the section plane, and its orientation on the page is determined by the front (F) and back (B) faces of the section plane. Check the section’s extents and orientation. Once you have created a section but before you start creating the section layout, take the following steps.ġ. This topic describes how to work with section layouts. Periodically save your changes to the section layout to see the effects of those changes in the scene. Detach the section layout tab from the main window and position it adjacent to the scene window. Wet etch undercut with a 1.3 lateral etch rate.Some sections will be too large to display in the scene, which will be indicated in the section layout editor.ĭisplaying section layouts in the scene is useful when you are editing a section layout and wish to see the effect of changes. You'll want to be clear if you are referring to the total change in the feature size or the sizing per side. For example, a square that is 1.25um per side that is sized -0.125um per side will shrink the square to 1.00um per side, a total shink of -0.25um in both X and Y dimensions. Sizing per side means the distance each edge of a polygon moves towards the interior or exterior of the polygon. Sizing is typically specified at drawn dimensions (1X) before reticle scaling is applied. You'll want to be clear which process you are referring to but the concepts apply equally well to both. Sizing is typically applied both in the mask process (by the maskshop) and in the wafer process (by the mask designer). The type of sizing your apply depends on the type of photoresist (positive or negative) and the type of etch (wet or dry). Sizing is a bias applied to your digitized data to account for lateral edge growth during etching. The next wavelength we expect to use for photolithography in a production mode will be 13.5nm in the extreme ultraviolet (EUV). Photolithography started with wavelengths in the optical spectrum (436nm) and has advanced to near ultraviolet (365nm) and deep ultraviolet (248nm, 193nm) wavelengths. Shortening the wavelength of light produces higher resolution and smaller features. The wavelength of the light is one of the key factors that determines the resolution of the pattern. The hard polymer is then removed leaving the substrate (silicon wafer or chrome) etched with the same pattern that was exposed with light.We etch the exposed substrate (where the polymer was removed) with an acid (wet etch) or a plasma (dry etch).We use this hard polymer as a template to etch the substrate. The soft polymer is washed away leaving a pattern of hard polymer on top of the substrate.Depending on the type of polymer used, it either softens or hardens where it is exposed to light. We expose the polymer with a pattern of light.the substrate) is covered with a layer of photo-sensitive polymer (a photoresist). A silicon wafer or a thin film of chrome on a photomask(i.e.In basic terms, the process of photolithography involves: This is the fundamental process used to mass-produce the integrated circuits and electrical components used inside almost all of today's digital devices. Photolithography is essentially a patterning technology using light as the transfer medium. Absorbance, a closely related term, considers only absorption within the optical component but not scattering. Mathematically, o ptical density is a logarithmic scale of how much light is transmitted through the absorber material: OD = Log (Power transmission factor).įor example, an optical density of 3 attenuates the light power by a factor of 10^3 (1,000). An optical density of 4 attenuates the light power by a factor of 10^4 (10,000). This optical attenuation may result from not only absorption of light but also from scattering of light. Technically, optical density is the amount of attenuation - or gradual intensity loss - that occurs when light passes through an optical component. So decades ago, when the industry standardized on chrome as the absorber of choice, it was determined that an optical density of 3.0 was sufficiently opaque at common exposure wavelengths in the UV spectrum. We want the coating to be thick enough to attenuate most of the light, but we also want it as thin as possible to get the best dimensional control on the mask since the thinner the chrome, the less etching is required.
The purpose of the metallic coating on a photomask, such as chrome, is to attenuate the intensity of light enough that photoresist on the other side will not be activated. If you hold a chrome mask up to a light, you can vaguely see the light shining through the chrome, much like the light leaking through a solar eclipse filter or welding goggles.
0 kommentar(er)
