A photomask mask assembly includes a reflective photomask and a protection structure. The reflective photomask includes a substrate and a reflective multilayer on a first substrate surface of the substrate at a front side of the reflective photomask. The protection structure is on a second substrate surface of the substrate at a backside of the reflective photomask, and is detachable from the reflective photomask at a temperature below 150 degree Celsius.

A substrate is provided with a patterned layer, for example, a photo resist layer, which may exhibit line roughness. In one exemplary embodiment, the patterned layer may be an extreme ultraviolet (EUV) photo resist layer. In one method, selective deposition of additional material is provided on the EUV photo resist layer after patterning to provide improved roughness and lithographic structure height to allow for more process margin when transferring the pattern to a layer underlying the photo resist. The additional material is deposited selectively thicker in areas above the photo resist than in areas where the photo resist is not present, such as exposed areas between the photo resist pattern. Pattern transfer to a layer underlying the photo resist may then occur (for example via an etch) while the patterned photo resist and additional material above the photo resist may collectively operate as an etch mask.

A substrate is provided with a patterned layer, for example, a photo resist layer, which may exhibit line roughness. In one exemplary embodiment, the patterned layer may be an extreme ultraviolet (EUV) photo resist layer. In one method, selective deposition of additional material is provided on the EUV photo resist layer after patterning to provide improved roughness and lithographic structure height to allow for more process margin when transferring the pattern to a layer underlying the photo resist. The additional material is deposited selectively thicker in areas above the photo resist than in areas where the photo resist is not present, such as exposed areas between the photo resist pattern. Pattern transfer to a layer underlying the photo resist may then occur (for example via an etch) while the patterned photo resist and additional material above the photo resist may collectively operate as an etch mask.

An apparatus for reducing hydrogen permeation of a mask is provided when generating extreme ultraviolet (EUV) radiation. The apparatus includes a mask stage configured to hold the mask, a hydrogen dispensing nozzle configured to eject hydrogen below the mask, and a trajectory correcting assembly. The trajectory correcting assembly includes a correcting nozzle and a gas flow detector. The correcting nozzle is configured to dispense at least one flow adjusting gas to adjust a trajectory of the hydrogen away from the mask to reduce hydrogen permeation at an edge of the mask. The gas flow detector is configured to measure a variation of an airflow of the hydrogen adjusted by the at least one flow adjusting gas.

An apparatus for reducing hydrogen permeation of a mask is provided when generating extreme ultraviolet (EUV) radiation. The apparatus includes a mask stage configured to hold the mask, a hydrogen dispensing nozzle configured to eject hydrogen below the mask, and a trajectory correcting assembly. The trajectory correcting assembly includes a correcting nozzle and a gas flow detector. The correcting nozzle is configured to dispense at least one flow adjusting gas to adjust a trajectory of the hydrogen away from the mask to reduce hydrogen permeation at an edge of the mask. The gas flow detector is configured to measure a variation of an airflow of the hydrogen adjusted by the at least one flow adjusting gas.

An overlay mark includes a first, a second, a third, and a fourth component. The first component is located in a first region of the first overlay mark and includes a plurality of gratings that extend in a first direction. The second component is located in a second region of the first overlay mark and includes a plurality of gratings that extend in the first direction. The third component is located in a third region of the first overlay mark and includes a plurality of gratings that extend in a second direction different from the first direction. The fourth component is located in a fourth region of the first overlay mark and includes a plurality of gratings that extend in the second direction. The first region is aligned with the second region. The third region is aligned with the fourth region.

An adhesive for an EUV mask includes an epoxy resin composition in an amount of 50 wt % to 80 wt % based on a total weight of the adhesive, the epoxy resin composition including an epoxy resin, a hardener, a toughening agent, a filler, and a curing accelerator, and an inorganic filler in an amount of 20 wt % to 50 wt % based on the total weight of the adhesive, the inorganic filler including one or more of aluminum hydroxide or calcium carbonate.

An adhesive for an EUV mask includes an epoxy resin composition in an amount of 50 wt % to 80 wt % based on a total weight of the adhesive, the epoxy resin composition including an epoxy resin, a hardener, a toughening agent, a filler, and a curing accelerator, and an inorganic filler in an amount of 20 wt % to 50 wt % based on the total weight of the adhesive, the inorganic filler including one or more of aluminum hydroxide or calcium carbonate.

An extreme ultraviolet lithography (EUVL) method includes providing at least two phase-shifting mask areas having a same pattern. A resist layer is formed over a substrate. An optimum exposure dose of the resist layer is determined, and a latent image is formed on a same area of the resist layer by a multiple exposure process. The multiple exposure process includes a plurality of exposure processes and each of the plurality of exposure processes uses a different phase-shifting mask area from the at least two phase-shifting mask areas having a same pattern.

An extreme ultraviolet lithography (EUVL) method includes providing at least two phase-shifting mask areas having a same pattern. A resist layer is formed over a substrate. An optimum exposure dose of the resist layer is determined, and a latent image is formed on a same area of the resist layer by a multiple exposure process. The multiple exposure process includes a plurality of exposure processes and each of the plurality of exposure processes uses a different phase-shifting mask area from the at least two phase-shifting mask areas having a same pattern.