Maverick and Guardian - Enhancements
Introduction
The latest release of Layout versus Schematic tools
from CELEBRITY CAD suite (Maverick full-chip
parametric netlist extractor and Guardian hierarchical netlist
comparator) delivers a number of significant advances. The engines of
both tools were tuned up to achieve essential reduction of running time
while processing huge designs. Maverick and Guardian
became integrated more with other CELEBRITY systems. They
provide extended setups that are easily customized, and offer new functions
that serve to achieve better precision for parameter extraction. Maverick
and Guardian reduce the number of verification/ modification
iterations.
LVS Cross-View Navigator
LVS Cross-View Navigator provides easy and convenient
way to analyze the results of the LVS run and to make necessary corrections
in the design. Using this tool (Figure 1) makes it possible to view all
nodes mentioned in reports directly on layout and schematic graphical
views from the perspective of both netlists (extracted from layout and
derived from schematic) involved in comparison.
Figure 1. Workbench of LVS Navigator.
Utilizing the capabilities of Silvaco Intertool Communication Server (Figure
2), LVS Navigator provides drive among basic LVS results, points out the
relevant node names on target report and netlists (Figure 3) and highlights
images of devices (Figure 4) or nets (Figure 5) simultaneously in Expert
Layout Processor and Scholar Schematic Capture.
Figure 2. Reference Panel of Inter-Tool
Communication Server.
Figure 3. Combined View of Compared
Netlists and Active LVS Report
Figure 4. Device Cross-View
initiated by LVS Navigator
Figure5. Highlighting of nets in
Expert and Scholar drawings.
SHOW SCOPE: The user of Cross-View Navigator
is offered with the possibility to trace any subset or full scope of the
related views:
- Post-run LVS report from one of the predefined categories (see below)
- SPICE Netlist extracted from layout cell
- SPICE Netlist produced by schematic capture
- Layout presented in the active window of Expert layout processor
- Schematic drawing loaded in Scholar schematic capture graphical window
The flexible scope gives the user the convenience of having a small number of views necessary for the particular verification activity on the screen.
NODE TYPE: As long as all basic LVS reports (matches, discrepancies, etc.) are split between relations involving nets and devices, LVS navigator works in one of the two corresponding modes - to show nets or instances (devices) inside all views included into the show scope.
REPORT CATEGORY: The set of design elements to be browsed during particular navigation session is defined by the nature of the report under consideration. LVS Cross-View Navigator supports (Figure 6) four categories of reports for browsing control:
- Matched Nodes (based on LVS report which is contained in .MTC file)
- Unmatched Nodes (based on .UNM file)
- Discrepancies (based on .UNM file)
- Parameter Errors (based on .PAR file)
Figure 6. Choice of Report Categories
in LVS Cross-View Navigator
Note the difference between discrepancies and unmatched nodes. Both of
them reference nets and instances (devices) that had not been matched
by Guardian. For discrepancies, potential matches are generated
by the tool (in most cases it means that if some local errors were fixed,
these nodes would match), while for unmatched nodes they are not produced.
For example, if one of the netlists contains some extra device which cannot
be merged with other ones and has no equivalent in another netlist, the
mentioned device should be classified as an unmatched node.
ACTIVE NETLIST / BROWSE STRATEGY: These settings affect the order of LVS report processing in the case of hierarchical netlists. ACTIVE NETLIST determines the netlist whose hierarchy will be taken into account while applying the selected strategy. STRATEGY, in turn, can be Top-Down or Down-up. The first choice means that references from the active netlist that are taken from the root (top) subcircuit are processed first, then the references are taken from primary instances from the root, and so on down to the leaf subcircuits (which do not contain instances of the other subcircuits).
SUBCIRCUIT: The choice of a subcircuit from the active netlist is provided to reduce navigation to those nodes that are contained in this subcircuit.
NAVIGATION COMMANDS: The "Start" command serves to activate the browsing list after changing any options (category, strategy etc.). The "Next" and "Previous" commands provide the initiation (highlighting) of nodes which are mentioned in the browsing list after or before the currently processed ones.
Extended Specifications for Resistor Parameters in Maverick
Maverick extracts geometry-dependent resistance
value for resistors. The efficient numerical procedure implemented in
Maverick provides high accuracy of extracted resistance
values for resistors of arbitrary configuration. Theoretically, those
values like head and contact resistance traditionally prescribed to some
resistors are not needed, because the head shape is taken into account
automatically. For contacts a separate type of resistor could be defined.
However, to meet common approaches, some extensions in definition of resistors
were made (Figure 7). This provides more flexibility in definition of
device recognition layers for various types of resistors.
Figure 7. Extended resistor setup.
To extract the value of the resistance, the user has to specify non-zero value for at least sheet resistance. Contact resistance is treated as the resistance of a single contact shape. If actual connection of a resistor head has been designed using a group of contact shapes, resistances of all of those shapes are summed as usual parallel resistors.
If resistor heads are parts of resistor recognition layers (see, for instance, grey area in Figure 8), then the head resistance is calculated from geometrical information and sheet resistance value is specified. The value of head resistance shown in Figure 7 is ignored in this case. If the resistor recognition shape (see the hatched area in Figure 9) does not cover the resistor head's areas, then the head resistance is not calculated. The extractor utilizes the value of head resistance shown in Figure 7 instead.
Figure 8. Resistor heads are parts of
recognition layers: automatic
calculation of head resistance.
Figure 9. Resistor heads are not in
recognition layers: head resistance
should be prescribed.
Resistance extraction routines need sheet resistance
value (in Ohms/square) to be specified for the resistor recognition layer
in the technology file. This can be done in the way as the following fragment
of Expert technology file shows.
Layer
{
Name = "N-Act"
...
Material
{
MaterialName = ""
Resistivity = 555
Permittivity = -1.00
Thickness = 1.00
}
}
The layer N-Act is the resistor recognition layer with sheet resistance
equal to 555 Ohm/square. The whole set of resistor parameters is specified
using the set of the following constructions within Device statement.
DevParam
{
NameP = "XXXXXXXXX"
ValueP = 100
}
NameP can be one of the following predefined strings:
"SheetRes" for sheet resistance
"DeltaW " for width outdiffusion parameter
"DeltaL" for length outdiffusion parameter
"HeadRes" for head resistance
"ContRes" for contact resistance
ValueP indicates the actual numerical value of the parameter
Conclusion
Silvaco's verification suite (Maverick, Guardian, Savage, Dragon) is a dynamically developing system, permanently adjusting to the diversity of customer needs. The evolution of verification tools is followed by their tight integration with layout processor and schematic capture. This allows the designers to run complicated projects much faster and more accurately.