Patent ID: 7666556

Claim:
A method for manufacturing a photomask, comprising the steps of: forming a mask pattern to be transferred onto a wafer over a transparent substrate; transferring the mask pattern to the wafer to form a wafer pattern; selecting a critical dimension modification region requiring line width modification in the wafer pattern transferred onto the wafer; coating a resist layer covering a front side surface of the mask substrate; performing back side exposure on a back side surface of the modification region of the substrate to selectively irradiate a portion of the resist layer between the mask patterns; selectively developing the irradiated portion of the resist layer to form a resist pattern covering and being self-aligned with the mask pattern to selectively expose a portion of the substrate between the mask pattern; varying light transmittance of the exposed portion of the substrate by implanting ions into said exposed portion using the resist pattern as an ion implantation mask to protect the mask pattern from being damaged by the implanting ions; and selectively removing the resist pattern.