Self-aligned method of making phase-shifting lithograhic masks having three or more phase-shifts

A method of making a phase-shifting mask comprising the steps of

• a) introducing first, second, third, and fourth mutually different dose levels of actinic radiation into first, second, third, and fourth regions, respectively, of an original resist layer, having a uniform composition and a uniform thickness, located on a planar top surface of a body that is transparent with respect to a prescribed wavelength, whereby the first, second, third, and fourth regions have mutually different rates of thickness reduction during step (b) herein;
• b) subjecting the resist layer to a first treatment that reduces the thicknesses of the first, second, third, and fourth regions of the original resist layer to mutually different amounts, and in particular that reduces the thickness of the first region to an amount that is less than those of the second, third, and fourth regions;
• c) subjecting the remaining resist layer and a first region of the body, underlying the first region of the original resist layer, to a second treatment that etches the first region of the body down to a predetermined depth beneath its planar surface;
• d) subjecting the remaining resist layer to a third treatment that reduces the thicknesses of the remaining second, third, and fourth regions of the remaining resist layer to mutually different amounts, and in particular that reduces the thickness of the remaining second region of the remaining resist layer to an amount that is less than those of the remaining third and fourth regions of the remaining resist layer;
• e) subjecting a second region of the body underlying the second region of the original resist layer, and the first region of the body, and the remaining resist layer to a fourth treatment that etches the first and second regions, respectively, of the body down to prescribed unequal respective depths beneath the major planar surface, no actinic radiation being introduced into the remaining resist layer subsequent to step (b).

A method of making a phase-shifting mask comprising the steps of:

• a) introducing first, second, and third mutually different dose levels of actinic radiation into respective first, second, and third regions of an original resist layer, having a uniform composition and a uniform thickness, located on a planar surface of a body that is transparent with respect to optical radiation of a prescribed wavelength, whereby the first, second, and third regions have mutually different rates of thickness reduction during step (b);
• b) subjecting the original resist layer to a first treatment that reduces the thicknesses of the first, second, and third regions of the resist layer to mutually different amounts, and in particular that reduces the thickness of the first region to an amount that is less than those of the second and third regions;
• c) subjecting the remaining resist layer and a first region of the body that underlies the first region of the original resist layer to a second treatment that etches the first region of the body down to a predetermined depth beneath its planar surface;
• d) subjecting the remaining resist layer to a third treatment that reduces the thickness of the remaining second region of the remaining resist layer to an amount that is less than that of the remaining third region of the remaining resist layer;
• and
• e) subjecting the remaining third region of the remaining resist layer and a second region of the body that underlies the second region of the resist layer to a fourth treatment that etches the first and second regions of the body to different predetermined first and second depths, respectively, beneath its planar surface, followed by the step of removing the remaining third region of the remaining resist layer.