Plasma Cleaning  [ Return towards  Applications  ]

This higher energy level allows these particles to be able to bond with most compounds that they come into contact with. Plasma typically comes in two types, chemical and physical. A physical plasma is one where atoms are accelerated in a straight line towards a surface in order to etch the surface. A chemical plasma is where the atoms become disassociated and highly active. In this case, the gas is then flowed over a surface, like a cloud of gas, in order to react with any impurities or oxides

In many processes, plasma cleaning is used either to remove oxides and reducible compounds from a surface, or to physically etch a surface. In IC packaging, plasma cleaning is used in several places to clean surfaces prior to bonding, encapsulation, and die attach. Gases typically used in plasmas can include combinations of argon, nitrogen, hydrogen, oxygen, and other less common gases (see table below). Most plasma equipment currently requires the use of a vacuum since the plasma is designed to be used at extremely low pressures.

However, recent work by AIR LIQUIDE and Acxys Technologies allows the use of plasma at ambient pressure and temperature. By having the plasma exist at atmospheric pressure, true in-line processing can be done with out the need for a batch style vacuum step. This plasma cleaning process should provide cost savings and thus have a future in IC packaging.

Gas Source Type vs. Plasma Surface Enhancements
(source Advanced Packaging Magazine, 02/02)