Critical dimension controlled method of plasma descum for conventional quarter micron and smaller dimension binary mask manufacture

A method of forming a metal mask from a chromium metal layer deposited upon a quartz substrate patterned for exposure of a workpiece to radiation of a specific range of wavelengths with said substrate being transparent to said radiation, said method comprising the sequential steps as follows:

• form said chromium metal layer superjacent to said quartz substrate,
• form a passivated chromium layer on said chromium metal layer,
• form a photoresist layer superjacent to said passivated chromium layer,
• expose said photoresist layer to a pattern,
• develop said photoresist to form a photoresist mask with at least one opening therethrough down to said passivated chromium layer, with sidewalls of said at least one opening having sidewall angles θ substantially less than an ideal vertical angle (90°),
• bake said photoresist mask, said passivated chromium layer, said metal layer and said quartz substrate,
• perform a descum operation to form more vertical sidewalls of said photoresist mask,
• perform an isotropic etching of said metal layer with a wet etchant etching through said at least one opening through said photoresist mask to form said metal mask providing an undercut beneath the edge of said photoresist mask,
• perform an after etching inspection dimension measurement of said metal mask,
• strip said photoresist mask, and
• perform an after stripping inspection dimension measurement of said metal mask with a laser interferometric system.