Mems device with controlled gas space chemistry

A MEMS device for modulating a UV light beam, comprising:

• a MEMS structure;
• a package having a window;
• and
• wherein the surfaces of said MEMS structure and said package window are coated with a metal-halide coating.

A UV photolithography system, comprising:

• a UV illumination source emitting a UV light beam along a first path;
• a condensing lens in said first light path sizing said light beam;
• light from said condensing lens coupled to the reflective surface of a MEMS device, said device being treated with a protective metal-halide coating to control the photochemical degradation of surfaces of said device caused by the reaction between UV optical flux and device package gases;
• an electronic controller coupled to the control input of said MEMS device for controlling the modulation of said device according to a digital photomask pattern;
• light being modulated according to said pattern reflected by the surface of said MEMS device along a second light path;
• a projection lens in said second light path receiving said modulated light;
• and
• light from said projection lens being projected onto and exposing a photosensitive surface.