Metal Oxide Removal Using Atmospheric Pressure Plasma Technology for Electronic Applications

Abstract

Copper is one of the most commonly used metals in the electronics industry. For example, it is extensively used as a lead frame material in integrated circuit packaging due to its superior thermal and electrical conductivity and low production cost. However, the formation of a native oxide on the surface along with the presence of organic contaminants hinder wire bond strength. The work presented here will focus on a novel approach to remove copper and other oxide layers using a nitrogen/hydrogen (95%/5%) gas plasma chemistry that does not require a vacuum environment. The processes are run at temperature conditions lower than 200°C, and at speed up to 150 mm/s which make the technology attractive for industrial upscaling. Results from the elemental analysis using scanning electron microscopy (EDS-SEM) of the plasma-treated versus as-received copper surfaces will be presented. Also, a brief analysis of the gas plasma-surface interactions, process parameters leading to oxide reduction of various metals (Cu, Sn) and equipment details will be discussed. Aside from improving wire bond strength to lead frames and pads, plasmas can be used to improve die attachment to various metal solder materials for flip chip and other electronic applications.