also approaching the substrate and the defect is also typically traveling more slowly it will be struck by more ions per unit of its mass and will be deflected much more than will the coating material in this way the technique selectively rejects larger particles but allows the coating material to pass through since the ion beam operates under similar conditions to most sputter coating processes the addition of the ion beam is highly compatible with existing coating technologies in contrast to other possible protection schemes such as a low energy gas curtain which operates at too high a pressure and too low of energies beams of ionized clusters of atoms u201c cluster ion beams u201d may be used as an alternate means of deflection of particles 0022 fig1 shows a low defect deposition tool within an evacuated chamber 10 an ion beam gun 12 directs an ion beam 14 onto target 16 a sputter plume 18 is generated and encompasses mask substrate 20 in addition to the sputter plume 18 reflected neutrals 22 of uncharged ar and other defect causing particles may also strike the mask substrate 20 thus multiple forces can act on a particle in the low defect deposition tool the ar ion beam may typically comprise ions having energies of about 800 ev the sputter plume may comprise mo or si atoms and have energies of about 5 ev the reflected neutrals i e uncharged ar may have energies of 100s of ev in the present invention another ion beam is used to protect the mask during coating as shown in fig2 the low defect deposition tool of fig1 is improved by adding a second ion gun 30 which produces a second.