Process variations have a growing impact on circuit performance for today's integrated circuit (IC) technologies. The Non-Gaussian delay distributions as well as the correlations among delays make statistical timing analysis more challenging than ever. In this paper, we present an efficient block-based statistical timing analysis approach with linear complexity with respect to the circuit size, which can accurately predict Non-Gaussian delay distributions from realistic nonlinear gate and interconnect delay models. This approach accounts for all correlations, from manufacturing process dependence, to re-convergent circuit paths to produce more accurate statistical timing predictions. With this approach, circuit designers can have increased confidence in the variation estimates, at a low additional computation cost.

In this paper, we propose a new linear programming based timing driven placement framework for high performance designs. Our LP framework is mainly net-based, but it takes advantage of the path-based delay sensitivity with limited-stage slew propagation, thus it enjoys certain hybrid feature of net and path-based timing driven placement. Our LP formulation considers not only cells on the critical paths, but also cells that are logically adjacent to the critical paths (i.e., the criticality ad jacency network) in a unified manner. We further present a timing aware spreading method to preserve timing in legalization for high performance designs. Our algorithm has been tested on a set of 65nm industry circuits from a multi-GHz microprocessor, and shown to achieve much improved timing on hand-tuned circuits.

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A Computer Aided Design tool is being developed to automatically produce design raphs that will fadiilate the layout of phase-shift masks. This tool is a design inierfade which utilizes SPLAT for the aerial image simulations. The program accepts a user specified geomwy and the mask parameter spe to be explored. It then automatically extr information such as intensity, contrast, scewidth, linewidth, and intensity slope from the SPLAT results for each iteration. In this paper, we apply the design system to a number of phase-shift mask patterns to explore design rule tradeoffs. For dark field masks with isolated spes and Levenson arrays of spaces, we determine that a shrink of the mask combined with a bloat of open areas shows promise as a means of &sign-ing phase-shift masks if one is willing to sacrifice distance between light areas. By examining sevezal typical mask patterns, we also show that an overall shrink of the mask does not require special design rules for each type of feature, but better scaling could result by appropriately developing new rules for different patterns. Since printing clear field masks is also important, we further pmbe the scalability of phase transitions. We show that a phase transition of 0.6 A/NA is the optimum length to achieve the highest intensity throughout the phase transition region. For 90 degree transitions, a length of 0.6 A/NA is needed while for 60-120 degree transitions, each step transition region must be at least 0.6 A/NA long. Finally, we present a new mask pattern for chains of contacts that has high intensity slope for a pitch of 1.2 JNA and below.

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