A Geometry Walker

This application is intended for finding very small objects (or slivers) that might be "buried" under the confusion of complicated layers. It arises from a common problem - imagine that you are comparing two IC layouts that are almost completely identical.

To make the comparison you do an XOR between each layer in the two databases.

The result is a third layout file (GDSII) that contains the differences - in many cases the differences are very tiny and scattered across the extents of the chip.

If you attempt to view the XOR layer on top of the one of the source layers you find it is difficult or even impossible to see the slivers. (Imagine a 0.2 um sliver on a chip that is 20,000 x 20,000 um in size)

What you need is a tool that will allow you to jump to the location of each sliver and zoom in around it so that you can examine it and decide what action to take.

What you Need

You will need two GDSII files - one of the source files used to generate the XOR and a second file that contains the XOR results (or slivers). The second file must be flat i.e. it cannot contain any hierarchy other than the top cell. It may contain data on multiple layers. (This limitation could be lifted on a more sophisticated version of Geo Walker)

How it Works

The user opens a GDSII or OASIS file. The user then starts the Geometry Walker and selects the XOR (sliver) file. The plug-in identifies the first coordinate of each boundary in the sliver file and makes an entry for it in the list box. The user can click on any entry and the display will be centered around the coordinate, it will be zoomed in (per the margin setting) and a marker will be drawn over the coordinate.

User Interface

The Geometry Walker user interface is described below:

Starting the Geometry Walker Plug-In (UNIX)

Load a GDSII or OASIS file into Qckvu3. Then from the Tools drop down menu select: Geometry Walker.

The Geometry Walker Plug-in Dialog

The dialog is at right:

Geometry File
a GDSII file containing the XOR results or slivers. Must be flat but may have multiple layers).

Layer - the layer on which this sliver is located

Extent - the coordinates of the lower left and upper right bounding box

All - selects all slivers in the table

Clear - clears all selections

Invert - inverts the selection

Playing Controls

You can have the display jump from line to line by using the Play button. The delay between screens is controlled by the Delay slider.


Preserve View - if this is checked then there is no zoom in/out based on the margin setting. This is normally used if you want a birds eye view of the various locations in the list.

Margin - the distance from the center to the edges of the display for each coordinate provided.

Delay - delay time between frames when in "play" mode.


    Shape - choose from a list of markers shapes.

    Color - click on the colored box and select the marker's color.

    Thickness - adjust the slider to make the marker strokes thicker or thinner (pixels)

    Size - adjust the slider to control the marker's size (pixels)

    Fill Geometry - if checked, the sliver geometry is filled with color making it easier to see.

At right, you can see what the dialog looks like once a sliver file has been loaded.


Below you can see an example where the display has been zoomed in and a marker shows the coordinate read from the CSV file.


For more information please contact: Steve DiBartolomeo, Applications Manager, Artwork Conversion Software, Inc. steve@artwork.com, Tel: 831 426.6163.

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