To use the interface, the technology file must be set up appropriately. This involves adding keywords to the physical layer blocks of the technology file, which define physical attributes of the materials. This can be done by editing the technology file with a text editor, or through use of the Extraction Parameter Editor from within Xic. In the latter approach, the Save Tech command can be used to dump an updated technology file.
The interface will determine a sequence of layers from the technology file. The first layer is a conductor, and is assumed to contact the substrate. Additional layers alternate between insulators and conductors.
It may be necessary to create ``dummy'' layers in order to accommodate layer sequences that are not as above. For example, suppose that one has a substrate covered by dielectric, followed by a conductor. One can define a dummy conductor layer between the substrate and the insulator, but not create any geometry on this layer. The effective sequence is then that desired, and the preprocessor will correctly handle input. Note, however, that the effective thickness of the dielectric is the specified thickness plus the thickness of the dummy conductor (which is arbitrary but must be larger than zero). This is due to the assumption of planarization, where ``holes'' in the dummy layer are filled with the covering dielectric.
Only layers that are visible will be used in the interface. The visibility of layers can be toggled from the layer menu by clicking with mouse button 2. The default layer visibility is set with the Invisible technology file layer block keyword. Making a layer invisible is a quick way to eliminate it from the data set used in the interface. When a conductor layer is made invisible, the via layers associated with the conductor will also be eliminated from consideration.
Layers that are recognized as conductors must have the following properties:
These keywords a described fully in 11.1.1.
Layers that are recognized as insulating via layers must have the following properties:
There is also a possible passivation insulator layer, that will cover the top conductor. If it exists, this layer is assumed to be everywhere present, and any actual patterning is ignored. A passivation layer must have the following properties:
The ordering of the layers in the technology file (and the layer menu) is generally independent of the ordering of the layers when sequenced by the interface. There are two exceptions:
The interface will perform the layer sequencing when a FastCap or FastHenry file is created, or whenever the sequencing is needed. A table of layer ordering is printed in a FastCap/FastHenry input file created.
Below is a listing of the physical layer block keywords that are used by the interface.
These keywords can be applied to the layer blocks in the technology file with a text editor, or can be introduced with the Extraction Parameter Editor in the Extract Menu.
The conductor layers can be given a resistivity or conductivity with the Rho and Sigma keywords, respectively. These are used by FastHenry (FastCap assumes perfect conductors). Additionally, the Lambda parameter, which specifies the London penetration depth for superconductors, can be specified. This is for the convenience of Xic users in the superconducting electronics R&D community. In this case, Rho/Sigma specify the unpaired conductivity from the two-fluid model.
The dielectric constant of the insulators is specified with the EpsRel parameter. If a Via layer is not given an EpsRel specification, 3.8 is assumed. A passivation layer must have EpsRel specified. These values are used only by FastCap.
The relative dielectric constant of the substrate can be altered by setting the SubstrateEps attribute keyword in the technology file. The keyword can be placed in the attributes section of the technology file, after all layer blocks and Device blocks, and the relative dielectric constant should follow the keyword. If not set, the value for silicon (11.9) is assumed. This parameter can be set with the Extraction Parameter Editor, or by editing the technology file. This is used only by FastCap.