1.1 Review of Previous Work



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1.1 Review of Previous Work

Technology Computer-Aided Design (TCAD) systems have become an indispensable   and integral part in modern technology design and fabrication. They contribute significantly in the reduction of design and development time and in the improvement of manufacturing yield. Whereas each system has its particular characteristics [34][29], TCAD systems commonly provide capabilities beyond those of individual process and device simulation tools. Facilities for tool invocation, coupling, and for the definition and execution of TCAD tasks are widely availablegif. By enabling the user to operate at the task rather than tool level, TCAD fulfills the need for higher level analyses brought about by the increase in design complexity and miniaturization. Typical TCAD high-level task applications include optimization, characterization, and statistical analysis. They offer a higher level, application oriented, conceptual means for the representation of design and characterization methodologies.

In [1] the basic architecture of a TCAD Framework     is described. Building on a unified representation and centralized software support, the framework was mainly divided in three layers:

Most of the early research and development efforts were concentrated at the data level rather than the task level. It was felt that a common data representation would provide the foundations for tool integration and development in the framework. Different implementations of the basic idea of a Profile Interchange Format (PIF) [26] are available   (e.g. [108][94][28][12]). More recently, the Semiconductor Wafer Representation (SWR) [75][10] defined an object-oriented application interface for data representation.  

Development work and the resulting implementations at the task level were less sophisticated and more unstructured. Early systems provided limited capabilities. The MASTIF system [11] focused on improving   the ease of use of individual TCAD tools. EASE [66], a   TCAD system with an application oriented user interface, supported the delivery of pre-defined task-oriented capabilities to users. In the MECCA system [83][62], command scripting was used to   integrate and drive the underlying tools as well as higher level applications. The need for a programmable tool control language for the definition, management and execution of TCAD tasks was formulated in [51]. This is an instance of a command extension language with specialized TCAD syntax and semantics such as commands to run the simulation tools and extract the relevant values from the output files. Various implementations of such a task language exist. They range from a script and template driven approach [64] to the use of special interface programs [4].

A closely related task level concept is the Process Flow Representation   (PFR) [75][13]. A PFR consists of the basic design, and/or manufacturing activities information. From a TCAD perspective, the PFR stores the sequence of simulation and analysis steps and their control data. This is the simulation flow controller role of the PFR [80].   By integrating the task language procedural aspects with the PFR and coupling it to the data representation layer, a uniform and homogenous interface layer to TCAD frameworks can be constructed [36]. This makes the task level the main contact point of the framework to the external world. This is a major feature of the Viennese Integrated System for Technology CAD Applications (VISTA) [35]. In the following   section the VISTA system and its architecture are overviewed with particular emphasis placed on the task level features.



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Next: 1.2 VISTA Up: 1 Introduction Previous: 1 Introduction



Martin Stiftinger
Tue Aug 1 19:07:20 MET DST 1995