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Design Automation

Manufacturability Enhancement Applications

Niagara is a program for manipulation complex, hierarchically-structured VLSI layouts (physical designs) that is widely used in IBM for physical design verification (e.g., design rule checking) and for manufacturability enhancement applications (e.g., optical proximity correction). Our project works with projects in IBM Microelectronics Division to improve the capabilities of the Niagara "base engine" and to extend applications of Niagara in several areas.

Niagara "Base Engine"

The Niagara "base engine" is a large collection of C++ code implemented on a number of Unix(tm) platforms. There is continuing effort to extend the functionality of this code (e.g., adding new geometric operations) dictated by new shape-processing applications, and ever-increasing need to improve the computational efficiency of Niagara, driven by the exponential increase in VLSI design complexity. Our project is working in several areas to improve computational efficiency:

  • Invention of efficient algorithms and structures for geometric operations like two-dimensionsional search and shape fracturing.
  • Implementation of an SMP-parallel version of Niagara.
  • Research on methods for characterizing and restructuring design hierarchies.

Logic-to-Layout Correspondence

A number of applications of Niagara relate to the correspondence between elements of a logical/electrical description of a VLSI circuit (devices, nets) and its physical representation (hierarchically-arranged 2D shapes). Originally, these applications, including layout-vs.-schematic (LVS) checking, electrical parasitic extraction, and design-probing, were developed separately, but we have abstracted the logic-to-layout correspondence component common to these applications and implementing that abstraction in a library of C++ templates, classes, and algorithms, including hierarchical graph-matching. Using these components, we have:

  • Implemented a new LVS application that is more efficient in time and storage, and provides greater flexibility, e.g., automatic symmetry-handling.
  • Created an "L2L engine" that is used in IBM's Microelectronics division in an application for cross-correlating faults found by optical inspection and electrical testing.
  • Created a GUI environment for diagnosing/fixing LVS errors, allowing cross-probing between logical and physical views of designs, using both the Cadence Virtuoso(tm) and IBM GYM design environments.
Manufacturability Enhancement

The rapid growth (shrinkage?) in VLSI technology, currently moving from .18um minimum features sizes to .15um, .13um, and .1um, places increasing demands on the capabilities of manufacturing processes, particularly lithographic pattern reproduction. Increasingly, those demands are met through a combination of improving the physical processes (e.g., using short wavelengths of light for optical projection) and resolution enhancement technology (RET) -- the use of shape-processing programs like Niagara for modelling and compensating for the shape-distorting effects of the physical processes. Our project works in several areas related to this:

  • Rule-based process-effect correction: These are applications coded in the same language ("DFFL") used for Niagara's design-rule checking, but serve the converse purpose: Instead of checking for geometries that would be problematic in Manufacturing and citing these as errors, the programs transform them into mask shapes that would produce the desired on-wafer patterns.
  • Model-based correction: In this approach, a first-principles or phenomenological model is developed to predict process effects, then this model is used in conjunction with an iterative solver to compensate for the predicted effects. Niagara's model-based Optical Proximity Correction is integrated into the SMP-enabled, hierarchical shape-processing software.

In addition to the Niagara-related work, members of our project have developed software that may be useful in other projects:

  • WebForum is a web-based tool for maintaining and viewing topic-indexed bulletin boards, similar to VM FORUMs but with additional capabilities and access from UNIX(tm) and Windows platforms.
  • The Niagara Template Library is a collection of templates for efficient, flexible container classes.

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