VLSI drawings transferring limitations (AKA ‘conversion problem’)

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-inCAD 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

VLSI drawings transferring limitations (AKA ‘conversion problem’)