| 摘要 |
A method of forming a high transmittance attenuated phase-shifting mask blank, comprising the following steps. An attenuated phase-shifting mask is provided that includes a shifter layer overlying a transparent substrate. The attenuated phase-shifting mask having a first transmittance and an initial phase angle. The attenuated phase-shifting mask and more specifically the shifter layer is treated with an aqueous solution of NH4OH:H2O2 for a first predetermined time increasing the first transmittance to a second transmittance and decreasing the initial phase angle to a second phase angle. The attenuated phase-shifting mask is then treated with a selected acid or base for a second predetermined time increasing the second transmittance to a third, predetermined transmittance and increasing the phase angle to a third, predetermined phase angle. The third phase angle is preferably substantially identical to the initial phase angle.
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