Method of forming via holes

A method of forming via holes, said method comprising:

• exposing one or more via pitch reduction patterns in a photoresist layer, wherein the one or more via pitch reduction patterns have a width and length Y and are pinched-in at a plurality of pinched-in points along the length Y of the one or more via pitch reduction patterns, said pinched-in points are separated from each other by a distance Z;
• developing the one or more via pitch reduction patterns to remove a photoresist material in the one or more via pitch reduction patterns;
• etching a middle layer below the photoresist layer using a polymer gas;
• etching a bottom layer below the middle layer to form a plurality of openings in the bottom layer, said openings in the bottom layer having a pitch of Z;
• and
• etching a dielectric layer below the bottom layer to form via holes having a pitch of Z,
• wherein the pitch of Z is smaller than a minimum spacing of the exposing operation.

A method of forming via holes, said method comprising:

• exposing a plurality of peanut-shaped patterns in a photoresist layer, wherein the plurality of peanut-shaped patterns are arranged to have a pitch of X along a long side of the plurality of peanut-shaped patterns;
• developing the plurality of peanut-shaped patterns to remove a photoresist material in the plurality of peanut-shaped patterns;
• etching a middle layer below the photoresist layer using a first polymer gas;
• etching a bottom layer below the middle layer using a second polymer gas different from the first polymer gas to form two openings in the bottom layer for every peanut-shaped pattern, said openings in the bottom layer having a pitch of X/2;
• and
• etching a dielectric layer below the bottom layer to form via holes having a pitch of X/2.