Mentor Graphics Brings Process Variability Data into the Design Flow

A couple of years ago, in the pages of EDN, I spoke about the need to create an integrated team among system houses, masks makers, and foundries in order to achieve acceptable yields on products manufactured with processes below 90 nm in feature size. Last week Mentor Graphics Corporation announced availability of the Calibre(R) LFD(TM) (Litho-Friendly Design) product, signaling a major rethinking of the IC design creation flow, and expanding the design for manufacturing (DFM) solutions from Mentor. Calibre LFD addresses the issue of how to manage process variability in the early stages of design creation.

Calibre LFD enables designers to make trade-off decisions on how to create a design that is more robust and less sensitive to the lithographic process window. Although designers need to consider lithography issues at the 90 nm technology node, attention to lithography is an absolute requirement at 65 nm, where process variations can greatly influence silicon results.

Independent device Manufacturers (IDMs) like AMD, have an easier time establishing and controlling the new flow than independent system houses because they control both the design and the fabrication process internally. Yet, Luigi Capodieci, principal member of technical staff at the company said that "By adding Calibre LFD to our existing flow, we can make layout modification trade-offs at the earliest stages of design creation, and dramatically improve layout robustness across the process window."

Foundries must provide an LDF kit to the designers, much in the same manner as a design rule checking (DRC) kit. The kit includes energy, dose and mask bias considerations, RET recipes, process models, and the parameterizable rules to be checked, all presented in a common results database. Of course most of this information is proprietary so the data is encrypted in a format proprietary to Mentor Graphics. The designer can run simulations to see how a layout will print under a particular lithographic process window. The goal is to drive the design to an 'LFD clean' as well as a 'DRC clean' sign-off.

Calibre LFD also calculates a Design Variability Index, or DVI(TM), as a way to measure how resilient the design is to process variations; a lower DVI value represents a more resilient design (figure 1). The DVI is used to compare different layout implementations and help designers select the one with the least sensitivity to variation.

Figure 1. The DVI guides the layout designers in making the design more robust against process variations.
Calibre LFD is built on the Calibre platform, and can be easily launched within popular layout environments through Calibre Interactive(TM). Calibre LFD plugs into a design flow much like an iterative design step, using the same layout editor used for the initial design. Designers can use a layout viewer/editor and a results viewing environment, such as Calibre RVE(TM) or Calibre DESIGNrev(TM), to view the check results and variability databases.

Pricing and Availability:

Calibre LFD is available immediately. Pricing starts at $246K (one year term license). More information is available at www.mentor.com or by calling 800-547-3000.