Method, program product and apparatus for performing double exposure lithography

A computer program product for controlling a computer comprising a storage device readable by the computer, means recorded on the storage device for directing the computer to perform a process of generating files representing complementary masks based on a target pattern having features to be imaged on a substrate, said complementary masks for use in a multiple-exposure lithographic imaging process, the process comprising the steps of:

• defining an initial H-mask corresponding to said target pattern;
• defining an initial V-mask corresponding to said target pattern;
• identifying horizontal critical features in said H-mask, said horizontal critical features having a width which is less than a predetermined critical width;
• identifying vertical critical features in said V-mask, said vertical critical features having a width which is less than a predetermined critical width;
• assigning a first phase shift and a first percentage transmission to said horizontal critical features, said horizontal features to be formed in said H-mask so as to exhibit said first phase shift and said first percentage transmission;
• assigning a second phase shift and a second percentage transmission to said vertical critical features;
• said vertical features to be formed in said V-mask so as to exhibit said second phase shift and said second percentage transmission;
• determining a maximum allowable width for horizontal and vertical scattering bars using a simulation of the multiple-exposure lithographic imaging process such that no residual scattering bars appear in a final image resulting from the multiple-exposure process;
• applying horizontal scattering bars in said H-mask that extend parallel to edges of certain of said horizontal features;
• and
• applying vertical scattering bars in said H-mask that extend parallel to edges of certain of said vertical features.

A device manufacturing method comprising the steps of:

• (a) providing a substrate that is at least partially covered by a layer of radiation-sensitive material;
• (b) providing a projection beam of radiation using an imaging system;
• (c) generating a plurality of masks utilized to endow the projection beam with a pattern in its cross-section;
• (d) projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material using a multiple-exposure lithographic imaging process, wherein, in step (c), said masks are formed by a method comprising the steps of
• defining an initial H-mask corresponding to a target pattern;
• defining an initial V-mask corresponding to said target pattern;
• identifying horizontal critical features in said H-mask, said horizontal critical features having a width which is less than a predetermined critical width;
• identifying vertical critical features in said V-mask, said vertical critical features having a width which is less than a predetermined critical width;
• assigning a first phase shift and a first percentage transmission to said horizontal critical features, said horizontal features to be formed in said H-mask so as to exhibit said first phase shift and said first percentage transmission;
• assigning a second phase shift and a second percentage transmission to said vertical critical features;
• said vertical features to be formed in said V-mask so as to exhibit said second phase shift and said second percentage transmission;
• determining, by using a computer, a maximum allowable width for horizontal and vertical scattering bars using a simulation of the multiple-exposure lithographic imaging process such that no residual scattering bars appear in a final image resulting from the multiple-exposure process;
• applying horizontal scattering bars in said H-mask that extend parallel to edges of certain of said horizontal features;
• and
• applying vertical scattering bars in said V-mask that extend parallel to edges of certain of said vertical features.

A method of imaging a wafer using a multiple-exposure lithographic imaging process comprising the steps of:

• defining a target pattern to be imaged on said substrate;
• defining an initial H-mask corresponding to said target pattern;
• defining an initial V-mask corresponding to said target pattern;
• identifying horizontal critical features in said H-mask, said horizontal critical features having a width which is less than a predetermined critical width;
• identifying vertical critical features in said V-mask, said vertical critical features having a width which is less than a predetermined critical width;
• assigning a first phase shift and a first percentage transmission to said horizontal critical features, said horizontal features to be formed in said H-mask so as to exhibit said first phase shift and said first percentage transmission;
• assigning a second phase shift and a second percentage transmission to said vertical critical features;
• said vertical features to be formed in said V-mask so as to exhibit said second phase shift and said second percentage transmission;
• determining, by using a computer a maximum allowable width for horizontal and vertical scattering bars using a simulation of the multiple-exposure lithographic imaging process such that no residual scattering bars appear in a final image resulting from the multiple-exposure process;
• applying horizontal scattering bars in said H-mask that extend parallel to edges of certain of said horizontal features;
• applying vertical scattering bars in said V-mask that extend parallel to edges of certain of said vertical features;
• imaging said H-mask utilizing a first source illumination;
• and
• imaging said V-mask utilizing a second source illumination.