SilicideTechnology for Integrated Circuits
This detailed text provides guidance on the development and application of metal silicide technology as it emerges from the scientific to the prototype and manufacturing stages.
TABLE OF CONTENTS SilicideTechnology for Integrated Circuits
Chapter 4: Cobalt Silicide Technology
T. Kikkawa, K. Inoue and K. Imai
4.1 SCOPE OF THE CHAPTER
According to the scaling rule [1], the device dimensions of complementary metal oxide semiconductor (CMOS) transistors have been reduced to improve the performances for ultra-large-scale integrated circuits (ULSI). The shrinkage of the feature size has caused the increase of resistances in both source/drain regions and poly-silicon gate electrodes of the CMOS transistors, resulting in degradation of electrical characteristics. In order to reduce the parasitic resistances in scaled CMOS transistors, self-aligned silicide (salicide) [2] technologies have been developed. Although titanium (Ti) silicide was used for 0.35 0.18 ?m technology nodes [3, 4], cobalt (Co) silicide has been introduced as a replacement of Ti silicide due to its scaling limitation [5, 6, 7, 8, 9, 10].
This chapter describes the basic properties of Co silicide as well as the advantages and issues of Co salicide processes. First, crystallographic and material properties are described, and then fabrication technologies and electrical characteristics are covered.
4.2 MATERIAL PROPERTIES
4.2.1 Introduction
Since Co silicide is formed by solid phase reaction between Co and silicon (Si), it is important to understand the material properties of Co and its silicide phases. From this point of view, the crystal structures of Co, Si and CoSi 2 and phase diagram of various Co silicides are shown in this section.
4.2.2 Crystal structure
Cobalt has two crystal structures, cubic and hexagonal. ?-Co possesses a cubic close-packing (ccp) structure and its lattice constant is a 0 = 0.35446 nm...
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