Method and system providing high flux of point of use activated reactive species for semiconductor processing

A system for treating a surface of a workpiece with electromagnetic radiation, said system comprising:

• a first gas source configured to provide a transmission gas defined by a first radiation absorption coefficient;
• a second gas source configured to provide a gaseous constituent defined by a second radiation absorption coefficient such that said gaseous constituent is more absorptive of said electromagnetic radiation than said transmission gas;
• a chamber comprising:
• a workpiece-containing portion;
• and
• an inlet configured to establish fluid communication between said first and second gas sources and said chamber such that a gaseous atmosphere is defined therein, said gaseous atmosphere comprising a first region spaced from said workpiece surface and configured to accept said transmission gas, and a second region disposed between said first region and said workpiece surface and configured to accept said gaseous constituent;
• and
• an electromagnetic radiation source configured such that upon operation of said electromagnetic radiation source, a beam produced thereby converges in said second region in close proximity to, but not on, said workpiece surface to dissociate said gaseous constituent into an activated species that chemically reacts with said workpiece surface.