Typically, monatomic oxygen plasma is created by exposing oxygen gas (O 2) at a low pressure to high power radio waves, which ionise it. This process is done under vacuum in order to create a plasma. As the plasma is formed, many free radicals and also oxygen ions are created. These ions could damage the wafer due to the electric field build up between the plasma and the wafer surface. Newer, smaller circuitry is increasingly susceptible to these charged particles that can get implanted into the surface. Originally, plasma was generated in the process chamber, but as the need to get rid of the ions has increased, many machines now use a downstream plasma configuration, where plasma is formed remotely and the desired particles are channeled to the wafer. This allows electrically charged particles time to recombine before they reach the wafer surface, and prevents damage to the wafer surface.