Method for improving CD micro-loading in photomask plasma etching

A method of etching an absorber layer disposed on a photomask, comprising:

• transferring a film stack disposed on a substrate into an etching chamber, the film stack having a chromium containing layer disposed on a molybdenum containing layer, wherein the chromium containing layer is partially exposed through a patterned photoresist layer;
• providing an etching gas mixture including Cl2, O2 and at least one hydrocarbon gas in to a processing chamber, wherein the Cl2 and O2 gases are supplied at a flow rate Cl2:O2 ratio between about 10:1 to 20:1 and the hydrocarbon gas is supplied between 2 percent and about 20 percent to the etching gas mixture by volume;
• supplying a RF source power to form a plasma from the etching gas mixture;
• providing a plasma bias power of between about 10 Watts and about 300 Watts;
• and
• etching the chromium containing layer through the patterned photoresist layer in the presence of the plasma.