Anyway, some older software only supports up to 200 vertices per polygon. In integrated circuit manufacturing, by far the largest application of GDS-II, most shapes are simple, orthogonal (sometimes called “Manhattan”) geometries. This has long been a problem-spot with GDS-II data interchange, in particular in research. If you’re making curved or complicated polygons, you can get shapes with many, many vertices in each polygon. For a 16-sided shape, the overhead quickly soars to 340% increase in exposure time - 3.4 times a long for the same area! The lesson: it pays to consider how many points to make your curves and circles. For one example, the increment in exposure time from a square to an octagon is about 30% increase in exposure time. But if you want to cover a large area with arrays of closely-spaced dots, the dot count can quickly become enormous - I’ve written ebeam dots at 2 x 10 10 dots per square centimeter, where shape overhead becomes very significant. If you’re making a few dozen or a few hundreds of dots, the difference is completely negligible. Why does shape count matter? Well, it directly impacts exposure time, and time is money, so the more sides per shape, the more money your exposure will cost. The 8 sided figure requires 4 shapes to expose, while the 16-sided dot has 17 shapes. If you choose to use 8, or 16 sides for your circle, be aware that the number of shapes the JEOL has to expose goes up quickly: You may well be able to use a simple square, which, given electron scattering and resist processing rounding, may come out to be a nice, round dot. The number of vertices in the curves you create will be controlled by two settings in the Setup/Preferences : Shapes : Defaults : Angle Resolution.Ĭonsider, for example, making very small circles with the JEOL ebeam. You can make circles, ellipses, arcs, sectors, and Bezier curves. One way to access these shapes is through the Utilities : Circular Tools. LayoutEditor has a very rich set of options for making curved structures, all of which will be output as polygons when the file is saved. You can also achieve the exact same result with the various Boolean Functions there is an entire menu of Boolean Tools under the Utilities menu.Īs mentioned elsewhere, there really are no curves in the GDS-II data format - all curves are approximated by polygons. Then choose menu item: Utilities : Misc : Punch With Selection. At this point in this example, there should be exactly 3 boxes (or polygons, depending on how they were created) selected - you can verify this by looking at the Select Counts in the lower right part of the screen: Then select the three squares, either by Shift-Clicking on each of the three, or by left-dragging a window across the three squares, but not the larger, enclosing rectangle - you don't want that one selected. If the top, left-click option is not "Select Element", then get to Select mode by either pressing "Escape", or click toolbar icon "Select/Edit". Well, first I select each of the three rectangles, in this case, by making sure I am in "Select" mode by checking the Mouse Help: LayoutEditor is, by default, smart about these two illegal polygon types, and will try to detect and repair polygons of this type - See the options in the Preferences/ Settings under Shapes : General : Polygon Checks.Ī common question, then is how do you create a shape with a “cut out” or hole in it, such as shown on the right above? In LayoutEditor, there are a few different ways.Ĭonsider the large rectangle here, and say I want to have 3 square holes cut through that rectangle, as drawn. Self-intersecting polygons, such as shown here, are not legal in any known mask-making or e-beam system.Īlthough self-intersection or self-overlapping polygons are illegal, self-touching polygons, in which one or more sides touches another side, but not overlaps, are allowed, and are a way to have “holes” inside of other shapes. It is possible to create various illegal polygons. There are some very important details about polygons of which you should be aware: Most mask shops specifically request that you do not send them flattened data (that is, data without hierarchy) because it adds too much to their overhead. It also makes design modifications much easier, and many times, it’s necessary to do design several iterations of design modifications to get your final desired lithography. For certain more advanced options such as proximity correction, the time/cost savings can be significant. It often makes both mask-masking and e-beam writing faster, and thus cheaper. To the extent reasonably possible, use hierarchy in your design. Let’s dig in a bit deeper with some more details. OK, so we’ve covered the basic objects, and how they are created, and we’ve covered hierarchical design, view levels and layers.
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