UCLA

Design Rules (DRs) are the biggest design-relevant quality metric for a technology. Even small changes in DRs can have significant impact on manufacturability as well as circuit characteristics including layout area, variability, power, and performance. To systematically evaluate design rules several works have been published. The most recent among them is the Design Rule Evaluator (UCLA_DRE), a tool developed by NanoCad lab at UCLA, for fast and systematic evaluation of design rules and layout styles in terms of major layout characteristics of area, manufacturability, and variability. The framework essentially creates a virtual standard-cell library and performs the evaluation based on the virtual layout using first order models of variability and manufacturability (instead of relying on accurate simulation) and layout topology/congestion-based area estimates (instead of explicit and slow layout generation).

However, UCLA_DRE suffers from few major limitations. First, UCLA_DRE currently does not have the capability to evaluate the interaction between overlay design rules and overlay control, which is becoming more critical and more challenging with the move toward multiple-patterning(MP) lithography. Second, UCLA_DRE currently evaluates design rules at the cell level which may lead to misleading conclusions because most designs are routing-limited and, hence, not every change in cell area results in a corresponding change in chip area. Third, delay was not evaluated but it is well-known that delay-change can affect chip-area due to different buffering and gate sizing to meet timing requirements.

The first part of this dissertation offers a framework to study interaction between overlay design rules and overly control options in terms of area, performance and yield. The framework can also be used for designing informed, design-aware overlay metrology and control strategies. In this work, the framework was used to explore the design impact of LELE double-patterning rules and poly-line end extension rule defined between poly and active layer for different overlay characteristics (i.e., within-field vs. field-to-field overlay) and different overlay models at the 14nm node. Interesting conclusions can be drawn from the results. For example, one result shows that increasing the minimum mask-overlap length by 1nm would allow the use of a third-order wafer/sixth-order field-level overlay model instead of a sixth-order wafer/sixth-order field-level model with negligible impact on design.

In the second part of the dissertation, a new methodology called chipDRE, a framework to evaluate design rules at the chip-level, is described. chipDRE uses a good chips per wafer metric to unify area, performance, variability and functional yield. It uses UCLA_DRE to generate virtual standard-cell library and uses a mix of physical design and semi-empirical models to estimate area change at the chip-level due to both cell delay and cell area change. One interesting result for well to active spacing shows non-monotonic relationship of ``good chips per wafer" with the rule value