VLSI drawings transferring limitations (AKA ‘conversion problem’)

Pattern transferring flowchart: Preparation with drawing software (AutoCAD, LEdit, CleWin, LASI) If necessary, conversion to JEOL supported file formats: Calma GDS-II (stream), J01 (local) JEOL-51 …

File formats DXF is AutoCAD Drawing Interchange Format (ASCII or binary) (Win) CIF (Caltech Intermediate Format) – supported by CleWIN (Win) LASI TLC File Format (open!) (Win, GNU) Calma GDS-II (stream): standard file format for transferring / archiving 2D graphical design data (Win, Sun, Unix, GNU) JEOL01: custom format, has many limitations

AutoCAD-DXF The DXF format is a tagged data representation of all the information contained in an AutoCAD drawing file Virtually all user-specified information in a drawing file can be represented in DXF format.

Calma GDS-II (stream) Binary format that is platform independent, because it uses internally defined formats for its data types The pattern data is considered to be contained in a library of cells. Cells may contain geometrical objects such as polygons (boundaries), paths, and other cells. Objects in the cell are assigned to layers of the design. Supports ONLY polygons and wires. The GDS-II format specification limits the number of vertices per polygon (boundary) and wire (path) to not more than 200 pairs of coordinates

CIF (Caltech Intermediate Format) CIF provides a limited set of graphics primitives that are useful for describing the two-dimensional shapes on the different layers of a chip. The basic drawing primitives are boxes, circles, wires and polygons; CIF2.0+ : donuts and symbol scaling

LASI TLC TLC is the file format used by the LASI layout editor LASI allows converting DXF -> TLC, TLC GDS-II TLC uses one file per cell A complex layout consists of several TLC files in one directory

Conversion issues Compatibility with JEOL e-beam file formats (DXF, GDS-II) Limitations: circuit complexity vs. size and compatibility Home-made vs. commercial converters: most formats are “protected” MC2 “design rule” is based on LEdit and GDS-II stream format AutoCAD is still powerful and traditional tool to create IC’s

DXF -> J01 -> J51 Simplest and reliable way Inconvenient for multiple layer layout It has many vital limitations

AutoCAD DXF -> Calma GDS-II Bengt Nilsson, SnL, v3.10 February 2000 LASI DXF->TLC->GDS-II Cadence (Sun, UNIX) LinkCAD (commercial, BAY Tech.INC)

Built-in CAD Viewer Supported formats: ASCII, PostScript, DXF, GDS-II, txt-GDS, CIF, TLC and others Batch file conversion: automatically convert several files within minutes. Easy selection of file formats and unique setup of the format are available. Interactively checks and repairs broken and open polygons / polylines. Flatten command will remove hierarchy from files for use in hierarchy sensitive applications. Easy selection of cells and layers to be converted

Design rules: Rule 1: Use zero-width closed polylines Rule 2: Don't use hatching to draw filled structures. Use solid lines instead Rule 3: Avoid drawing polylines with more than 200 vertices. GDS-II format does not accept this Rule 4: No self-intersection. A polyline may not self-intersect. If it does, the result is unpredictable (but it can touch itself!)

Some conclusions: Optimal conversion strategy depends on complexity There are several opportunities to convert files from AutoCAD to GDS-II or JEOL01 If the drawing is created in AutoCAD and very complex, LinkCAD affords the best way to convert it into GDS-II format