Jamil Kawa

Modeling and analysis of differential signaling for minimizing inductive cross-talk

Many physical synthesis tools interdigitate signal and power lines to reduce cross-talk, and thus, improve signal integrity and timing predictability. Such approaches are extremely effective at reducing cross-talk at circuit speeds where inductive effects are inconsequential. In this paper, we use a detailed distributed RLC model to show that inductive cross-talk effects are substantial in long busses associated with 0.18 micron technology. Simulation experiments are then used to demonstrate that cross-talk in such high speed technologies is much better controlled by re-deploying interdigitated power lines to perform differential signaling.

Managing on-chip inductive effects

With process technology and functional integration advancing steadily, chips are continuing to grow in area while critical dimensions are shrinking. This has led to the emergence of on-chip inductance to be a factor whose effect on performance and on signal integrity has to be managed by chip designers and has to be sometimes traded off against other performance parameters. In this paper, we cover several techniques to reduce on-chip inductance which in turn improve timing predictability and reduce signal delay and crosstalk noise. We present experimental results obtained from simulations of a typical high performance bus structure and a clock tree structure to examine the effectiveness of some of the different inductance reduction techniques.

A layout dependent full-chip copper electroplating topography model

In this paper, a layout dependent full-chip electroplating (ECP) topography model is developed based on the additive nature of the physics of the EP process. Two layout attributes: layout density, and feature perimeter sum are used to compute the post-ECP topography. Under a unified mechanism, two output variables representing the final topography: the array height and the step height are modeled simultaneously. Using the proposed model long-range effects of the ECP process can be incorporated easily as well. The simulation results of our model were verified with test structure experimental data published in the literature and are presented in this paper. The results show that the errors are less than 5%. This model is not limited to the regular test structures; it can also be used for any practical design. The results of such partial application are shown here as well. Our proposed ECP model can be used to model systematic variations caused by an ECP process or by a chemical mechanical planarization (CMP) process. The potential applications of this model include: layout design evaluation for catastrophic failure prevention; yield aware design (design for manufacturability), and variation- aware timing analysis.

Accurate modeling of substrate resistive coupling for floating substrates

This article focuses on the formulation of the substrate resistive coupling using boundary element methods, specifically for substrates without grounded backplates (floating substrates). An accurate and numerically stable formulation is presented. Numerical results are shown to demonstrate the correctness and the numerical robustness of the formulation.

Design automation for mask programmable fabrics

Programmable circuit design has played an important role in improving design productivity over the last few decades. By imposing structure on the design, efficient automation of synthesis, placement and routing is possible. We focus on a class of programmable circuits known as mask programmable circuits. In this paper, we describe key issues in design and tool methodology that need to be addressed in creating a programmable fabric. We construct an efficient design flow that can explore different logic and routing architectures. The main advantage of our work is that we tailor tools designed for standard cell design, that are readily available in the market, to work on a programmable fabric. Our flow requires some additional software capability. A special router that understands programmable routing constructs to complete connections is described. In addition, a tool that packs logic efficiently after synthesis is also presented.

An IC manufacturing yield model considering intra-die variations

In deep submicron, feature sizes continue to shrink aggressively beyond the natural capabilities of the 193 nm lithography used to produce those features thanks to all the innovations in the field of resolution enhancement techniques (RET). With reduced feature sizes and tighter pitches die level variations become an increasingly dominant factor in determining manufacturing yield. Thus a prediction of design-specific features that impact intra-die variability and correspondingly its yield is extremely valuable as it allows for altering such features in a manner that reduces intra-die variability and improves yield. In this paper, a manufacturing yield model which takes into account both physical layout features and manufacturing fluctuations is proposed. The intra-die systematic variations are evaluated using a physics-based model as a function of a designs physical layout. The random variations and their across-die spatial correlations are obtained from data harvested from manufactured test structures. An efficient algorithm is proposed to reduce the order of the numerical integration in the yield model. The model can be used to (i) predict manufacturing yields at the design stage and (ii) enhance the layout of a design for higher manufacturing yield

A min-variance iterative method for fast smart dummy feature density assignment in chemical-mechanical polishing

Dummy feature filling is an efficient approach for reducing wafer-topography variation in chemical-mechanical polishing (CMP), which is the key planarization process in modern VLSI fabrication. In this paper, we present a new min-variance iterative method for fast smart dummy feature density assignment and post-CMP topography variation reduction. This method iteratively selects target areas using an efficient CMP low-pass filter model and a variance-minimizing heuristic, and assigns/removes dummy features accordingly. Because of the efficient usage of the 2D fast Fourier transform (FFT), the computational cost of this new method is close to O(nlog(n)), making it much faster than the existing linear programming method that costs O(n/sup 3/). Numerical experiments show the computational cost of our new method is almost negligible when compared with the LP method and its solution is very close to the optimal solution.

Crosstalk-Induced Delay, Noise, and Interconnect Planarization Implications of Fill Metal in Nanoscale Process Technology

In this paper, we investigate the crosstalk-induced delay, noise, and chemical mechanical polishing (CMP)-induced thickness-variation implications of dummy fill generated using rule-based wire track fill techniques and CMP-aware model-based methods for designs implemented in 65 nm process technology. The results indicate that fill generated using rule-based and CMP-aware model-based methods can have a significant impact on parasitic capacitance, interconnect planarization, and individual path delay variation. Crosstalk-induced delay and noise are significantly reduced in the grounded-fill cases, and designs with floating fill also experience a reduction in average crosstalk-induced delay and noise, which is in contrast to the predictions of previous studies on small-scale interconnect structures. When crosstalk effects are included in the analysis, the observed delay behavior is significantly different from the delay modeled without considering crosstalk effects. Consequently, crosstalk-induced delay and noise must be simultaneously considered in addition to parasitic capacitance and interconnect planarization when developing future fill generation methods.

EDA Challenges in Nano-scale Technology

Since the onset of the 90 nm node the challenges associated with further transistor scaling while maintaining a consistently functional, reliable, and yielding design have increased substantially. While those challenges carry across the spectrum of the manufacturing, the EDA, and the design communities, we believe it is the responsibility and the goal of the EDA industry to deal with those issues as thoroughly and as seamlessly as possible to make those challenges transparent to the designer. In this paper we expose and analyze a plurality of those challenges and briefly go over the solutions EDA tools are offering for dealing with them. We also look forward and cover some of the future challenges associated with the integration of the emerging bottoms-up nano-materials flow with the traditional CMOS top-down process flow which has also entered the nano-era

Accurate modeling of substrate coupling for substrates without grounded backplates

An accurate and numerically stable formulation is presented for the substrate resistive coupling using boundary element methods, for floating substrates (without grounded backplates).