Aluminum Interconnect Cleaning and Drying
The cleaning challenges associated with the integration of Al are examined for post-tungsten plug, post-conductor line etching, and post-via etching. The different residues formed during these processing steps are described and the approaches to clean and remove these residues by wet processing are presented. The chemical formulations used to remove the residues are discussed; fluoride-containing and hydroxylamine mixtures are the main focus. The applications and the process parameters for successful cleaning are presented.
Keywords: aluminum cleaning, interconnect cleaning, via cleaning, metal line cleaning, tungsten plug cleaning, fluoride formulation, hydroxylamine, post-etch aluminum residue, post-etch residue removal
9.1 Introduction to Aluminum Interconnect Cleaning
Since the middle 1970’s, aluminum (Al) has been the predominant material for metallization used in integrated circuit (IC) manufacturing. Starting in the mid-1990’s, copper (Cu) has supplanted Al as the interconnect metal of choice for advanced logic devices, largely as a result of its higher electrical conductivity, better resistance to electromigration, higher reliability, and lower overall manufacturing cost [1, 2].
This transition, however, would not have been possible without the concurrent development of advanced planarization methods and damascene-style process integration, ...