Dual trench alternating phase shift mask fabrication

A semiconductor device fabricated at least in part by using a dual-trench alternating phase shift mask (PSM) fabricated at least in part by performing a method comprising:

• patterning an chromium layer over a mask layer over a quartz layer of the PSM according to a semiconductor design;
• first dry etching the mask layer according to deep trenches of an alternating PSM design to remove the mask layer from the deep trenches of the alternating PSM design;
• first dry etching a first plurality of times the quartz layer through a first photoresist layer applied over the chromium layer and patterned according to the deep trenches of the alternating PSM design by using backside exposure, to initially form deep trenches of the PSM;
• second dry etching the mask layer according to shallow trenches of the alternating PSM design to remove the mask layer from the shallow trenches of the alternating PSM design;
• and,
• second dry etching a second plurality of times the quartz layer through a second photoresist layer applied over the chromium layer and patterned according to the shallow trenches and the deep trenches of the alternating PSM design by using backside exposure, to completely form shallow trenches and the deep trenches of the PSM.

A dual-trench alternating phase shift mask (PSM) fabricated at least in part by performing a method comprising:

• patterning an chromium layer over a mask layer over a quartz layer of the PSM according to a semiconductor design;
• first dry etching the mask layer according to deep trenches of an alternating PSM design to remove the mask layer from the deep trenches of the alternating PSM design;
• for each of a first plurality of times,
• applying a first photoresist layer over the chromium layer;
• backside exposing the first photoresist layer;
• developing the first photoresist layer to remove exposed parts of the first photoresist layer;
• dry etching the quartz layer through the exposed parts of the first photoresist layer to initially form deep trenches of the PSM;
• second dry etching the mask layer according to shallow trenches of the alternating PSM design to remove the mask layer from the shallow trenches of the alternating PSM design;
• for each of a second plurality of times,
• applying a second photoresist layer over the chromium layer;
• backside exposing the second photoresist layer;
• developing the second photoresist layer to remove exposed parts of the second photoresist layer;
• dry etching the quartz layer through the exposed parts of the second photoresist layer to completely form shallow trenches and the deep trenches of the PSM;
• and,
• removing the second photoresist layer.