Layout Template File Format

SYMMIC^TM Users Manual
Version 3.1.6
(TM) Trademark 2008 CapeSym, Inc.

Layout Template File Format

Like the device template, the layout template is an XML-formatted input file. The layout template describes the arrangement of devices in a MMIC. The XML syntax is defined in a Document Type Definition (DTD) file called mmic_format.dtd. This DTD file can be used to validate a layout template file by using an XML validator, such as validateXML.htm in Internet Explorer. (See the \validate folder on the installation CD.)

A template file begins with a reference to the DTD:

<?xml version="1.0"?>
<!DOCTYPE MMIC SYSTEM "mmic_format.dtd">

The next line of the file opens the MMIC element:

The MMIC element tag contains attributes for a title, the overall dimensions of the MMIC, and a meshsize. The title attribute specifies a string (enclosed in quotes) that describes the layout. This string is limited to 255 characters, and quotation marks, commas, less than signs (<) and greater than signs (>) are not allowed. The length and width attributes specify the extent of the rectangular layout area in microns. Length is in the x-direction, and width is in the y-direction.

The last two attributes specify how to mesh the layout between devices. (The specification of meshes within devices occurs in the device template files.) For a layout of multiple devices, the areas outside of devices are represented with a regular mesh of square elements, the size of which is specified by the meshsize attribute. A fine resolution will improve the representation of the solution close to hot devices, but a coarse resolution will produce a smaller solution file. The final solution mesh is not solved directly, however, so this efficiency is not a big concern for performance. As each device is solved in a superposition, the device mesh is extended with biasing to the edges of the whole MMIC. The bias factor used for mesh expansion to the periphery is specified by the borderbias attribute. This bias factor can have a big effect on how quickly the problem is solved. A conservative value of 1.25 is used by default, but a larger (more efficient) value can often be tolerated with little loss of accuracy.

An additional MMIC attribute

checkDeviceOverlap=”false”

allows device overlap checking to be disabled. Normally, whenever a layout model is built (or rebuilt, e.g. after a parameter change,) a check for overlap between adjacent devices is performed. Disabling the overlap check will improve loading time for layouts containing large numbers of devices.

DeviceTemplate

A MMIC element contains one or more <DeviceTemplate> elements, followed by a closing tag, as in the following example:

Each DeviceTemplate element tag may contain the following attributes:

file	File path string which can be relative or absolute
xpos	Floating point specifying the x-location of the device
ypos	Floating point specifying the y-location of the device
center	Boolean (“true”,“false”) whether (xpos,ypos) refers to the center of device
angle	Floating point specifying 1 of 4 possible rotations (0, 90, -90, 180)
flip	Boolean indicating whether the device is flipped vertically
mirror	Boolean indicating device is mirrored around its maximum x-extent

The file path attribute must be present; the rest of the attributes are optional. See the DTD for the default value used when an attribute is not explicitly given in the tag. Generally, booleans default to false and floating point values default to zero.

The (xpos,ypos) gives the location of the lower left corner of the device template file specified in the file attribute, unless the center attribute is true. When the center attribute is true, (xpos,ypos) give the location of the center of the device. The device is first mirrored in x, then flipped vertically, then rotated by the angle, before the (xpos,ypos) positioning is applied.

Export

A MMIC element may also contain a single <Export> element, but this tag is optional. If present, the Export element specifies the parameters for creating a device from the layout.

The Export element tag may contain the following attributes:

toFile	File string (relative or absolute path) for the exported device
name	String name of the exported device
appendFile	File path string to device template containing layers to append
appendLayers	Number of layers from the appendFile to append
appendTop	Boolean indicating whether the append layers go on top or bottom
resolve	Floating point number indicating the degree of feature smoothing

The Export element allows command line access to the export operation as specified in the Create device template... item from the File menu. The parameters of this dialog are precisely the attributes of the Export element tag. So for more details on the meaning of these attributes, see the description of this operation elsewhere in the manual.