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Technology File Setup

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:

  1. The layer must be visible.
  2. The layer must have the conductor attribute. This will be true if any of the Conductor, Routing, Contact, or one of the ground plane keywords has been applied.
  3. The layer does not have the Contact keyword applied. These layers are not used in the layer sequence, but geometry from Contact layers will be merged with the geometry from the target layer of the Contact specification, if that layer is in the sequence.
  4. The layer must have the Thickness keyword applied, with a positive layer thickness value.

These keywords a described fully in 13.1.2.

Layers that are recognized as insulating via layers must have the following properties:

  1. The layer must be visible.
  2. The layer must have the Via keyword applied, and the target conductors must be in the list of recognized conductors.
  3. The layer must have the Thickness keyword applied, with a positive layer thickness value.

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:

  1. The layer must be visible.
  2. The layer must not have a conductor attribute or the Via keyword applied.
  3. The layer must appear in the layer menu to the right of (above) the topmost conductor used in the sequence.
  4. The layer must have the Thickness keyword applied, with a positive layer thickness value.
  5. The Layer must have the EpsRel keyword given, with a dielectric constant value larger than 1.0.

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:

  1. The passivation layer, if one appears, must be defined after all of the conductor layers in the technology file (or appear above the conductor layers in the layer menu).
  2. The lowest conductor must be listed before the topmost conductor in the technology file (or appear below the topmost conductor in the layer menu).
The ordering is otherwise determined from the Via references, which is not necessarily the order in which the layers appear in the technology file or layer menu.

The layer sequencing will be performed when objects are initially saved in the interface. A log file is created, named ``fch_sequence.log'', which is kept in a temporary directory along with other log files. The Log Files button in the main window Help Menu can be used to access the log files. If an error is detected during processing, a window displaying the log appears.

A comment showing a layer ordering table is printed in any top-level FastCap/FastHenry input file created.

Below is a listing of the physical layer block keywords that are used by the interface.

$\textstyle \parbox{4in}{\sf
Conductor\\
Routing\\
Contact\\
GroundPlane\\
GroundPlaneClear}$
Each of these keywords applies a conductor attribute to the layer. A layer must have the conductor attribute to be recognized as a conductor by the interface.

Via
This keyword indicates that the layer is an insulator, and is used to make contact between two conductors.

Thickness
This specifies the physical thickness of the layer, in microns. Only layers with nonzero thickness will be used by the interface.

Rho/Sigma
Either of these parameters can be applied to a conductor layer to provide a resistivity/conductivity value, in MKS units. This value will be used in the FastHenry input. If not specified, FastHenry will use its own default, which is the conductivity of copper. Only one of these should be applied per layer.

Lambda
This provides the superconducting London penetration depth of a conductor, and if nonzero will signal FastHenry to treat the conductor as a superconductor. The value must be given in microns.

EpsRel
This provides a relative dielectric constant to insulating layers.

DarkField
This is implied by Via and GroundPlaneClear, and indicates that the physical material is the inverse of the patterning shown on-screen.

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.


next up previous contents index
Next: Geometry Specification Up: The FastCap/FastHenry Interface Previous: FastCap/FastHenry Interface Limitations   Contents   Index
Stephen R. Whiteley 2012-04-01