Sign-off Driven Layout in Laker Custom Layout
In advanced technology nodes, both the number of design rules and the complexity of those rules are increasing at a rapid pace. There are approximately twice as many rules at 28nm as there were at 90nm and many of the new rules are difficult to comprehend. Yes, there are more layers of metal, but there are also many new rules,
Source: Mentor Graphics
such as dense end-of-line rules, designed to avoid DFM issues. In addition, front-end (device) rules have increased by 80% without any major increase in the number of layers, as we begin to deal with the layout dependent effects and DFM issues that are endemic in advanced technology nodes. This trend will accelerate for 22nm and 16nm
Figure 1: Physical verification Treands: Increasing DRC Complexity
Source: Mentor Graphics
nodes as the number of rules grows and their complexity compounds with pattern matching and double-exposure rules. These advanced rules are non-intuitive and the fixes are even less so. It is not uncommon for advanced DRC error flags to elicit as many “???” as “!!!” these days. This means that DRC repair of advanced rule violations can easily cause new violations that are equally difficult to fix.
Analog design
A good analog circuit is based on four factors: precision modeling, accurate simulation, good layout arrangement, and parasitic component extraction, with each step dependent on the successful completion of the prior one. After you have spent many hours cleaning up complex design rule violations, the last thing you want is for your LVS fixes to start a lengthy new round of DRC check-and-repair cycles. In advanced technology nodes, layout dependent effects can cause even DRC- and LVS-clean layout to fail post-layout simulation and the resulting layout corrections can initiate yet another DRC/LVS cycle at the critical tapeout time.
Figure: Typical custom design flow
A solution
As you have no doubt heard by now, on March 10 at The Design Technology Forum, Mentor Graphics and SpringSoft announced the launch of Calibre® RealTime, a platform that provides instantaneous Calibre design rule checking (DRC) in the Laker™ OpenAccess (OA) layout environment using the foundry sign-off rule decks. This unique capability enables users of the Laker system to generate high quality custom layouts in less time and get to foundry sign-off sooner, even at the most advanced technology nodes.
Figure: A sign-off driven design
flow
Although SpringSoft offers, and continues to evolve, a variety of rule-driven capabilities within the Laker Custom Layout Automation System - from dynamic DRC flagging to near sign-off DRC-clean digital routing, and a schematic-driven layout flow that dramatically reduces LVS issues – we recognized that real-time, sign-off DRCs using the “golden” foundry design rule deck would also be an attractive offering.
The SpringSoft and the Mentor® teams worked very closely to ensure that the Calibre RealTime DRC platform is easy to use and intuitive for users of the Laker system. Their efforts focused on providing both real-time and single-click operations with virtually instantaneous results. Every time designers edit a polygon, path, or placement in the Laker OpenAccess (OA) layout environment, the Calibre RealTime product detects the change and automatically runs DRC on that change. Users can run
Figure: A RealTime DRC flag with mouse-over description
more rules or different rule sets at any time with a single click. Full-chip DRCs are still available at anytime using the standard Laker-Calibre DRC interface.
In addition, a graphical user interface enables users of the Laker system to easily define custom rule sets for different design styles or stages of layout, all without editing the ‘golden’ rule file. Feedback is immediate and all error navigation is entirely within the Laker environment using a built-in Calibre RealTime error review toolbar. Users can focus on creating DRC-clean layout without all the window clutter normally associated with multiple tool flows.
Conclusions
By teaming up the Laker Custom Layout Automation System with Calibre RealTime, it is now possible to incrementally create sign-off ready layout at the most advanced nodes using the Laker system’s interoperability and the same Calibre engine and DRC rule decks that are used for sign-off DRC by most major foundries. Whether you are fixing final interface DRCs on the final layout or placing the first MCell, real-time, sign-off DRCs are now available in the Laker Custom Layout Automation System.
