DISCUS: AN ADVANCED SYSTEM FOR DIGITAL IMAGING OF SEMICONDUCTORS USING THE SCANNING ELECTRON MICROSCOPE

A new system for the computer-aided failure analysis of integrated circuits using the scanning electron microscope is presented. This system employs hierarchical constructs such as those found in a multitasking computer operating system (OS) to address problems inherent in the SEM IC failure analysis procedure. In operation, the system overlays the resident operating system in the same manner in which a typical operating system overlays the computer hardware. Thus, DISCUS forms a hierarchical layer (a "meta operating system") above the resident OS with which the user interacts. Some of the structural components of DISCUS are identical to principle elements of a typical operating system; the command-line parser, the memory manager and the display drivers are all of standard design. The unique features which DISCUS provides are two-fold: (1) a new medium and low-level scheduling algorithm, and (2) an object-oriented data management scheme in a SEM failure analysis system. The new scheduling algorithm is an implementation of the Kleinrock model, which provides the means for an adaptive, high-level process scheduler mechanism. The capabilities of this scheduler are used to maximize data acquisition throughput given the current system hardware configuration. This algorithm is applicable to a wide variety of multitasking process scheduling systems. The application of the object-oriented programming approach to a SEM failure analysis system is a natural extension of the current tendency towards hierarchical IC design style. The advantages of such a system are in its modularity and easy adaptability to new data formats and in its efficient use of the resources available in the computer-controlled SEM system. An overview of the design of the DISCUS system is presented and the implementation of some of its features are discussed in detail.