VLSI drawings transferring limitations (AKA ‘conversion problem’)
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Transcript of VLSI drawings transferring limitations (AKA ‘conversion problem’)
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VLSI drawings transferring limitations
(AKA ‘conversion problem’)
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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 …
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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
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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.
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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
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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
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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
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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
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DXF -> J01 -> J51
• Simplest and reliable way
• Inconvenient for multiple layer layout
• It has many vital limitations
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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)
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• 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
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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!)
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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