1. Introduction
As the design of high performance VLSI becomes more complex and integrated, the number of components and clock frequency increase and the chip size decreases accordingly [1]. With the higher complexity in a chip, the power dissipation and consequently the temperature are higher. Temperature can have a dramatic impact on circuit performance, power consumption and reliability. Even though development of CAD tools has been significant in recent years, the lack of a reliable electro-thermal simulator is noticeable.