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