Method, program product and apparatus for performing double exposure lithography

1. A computer-implemented method of generating 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, said method 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, by the computer, 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, by the computer, 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 V-mask that extend parallel to edges of certain of said vertical features.

2. A method of generating complementary masks according to claim 1 , further comprising assigning chrome to all non-critical features in said H-mask and said V-mask, said non-critical features having a width which is greater than or equal to said predetermined critical width, said non-critical features to be formed in said H-mask and said V-mask utilizing chrome.

3. A method of generating complementary masks according to claim 2 , wherein said first phase shift and said second phase shift are equal, and said first percentage transmission and said second percentage transmission are equal.

4. A method of generating complementary masks according to claim 2 , further comprising the steps of:

applying chrome shielding to vertical edges of features in said H-mask; and

applying the horizontal scattering bars to said H-mask after applying the chrome shielding.

5. A method of generating complementary masks according to claim 2 , further comprising the steps of:

applying chrome shielding to horizontal edges of features in said V-mask; and

applying the vertical scattering bars to said V-mask after applying the chrome shielding.

6. 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.

7. A computer program product according to claim 6 , wherein the process farther comprises the step of assigning chrome to all non-critical features in said H-mask and said V-mask, said non-critical features having a width which is greater than or equal to said predetermined critical width, said non-critical features to be formed in said H-mask and said V-mask utilizing chrome.

8. A computer program product according to claim 7 , wherein said first phase shift and said second phase shift are equal, and said first percentage transmission and said second percentage transmission are equal.

9. A computer program product according to claim 7 , wherein the process further comprises the steps of:

applying chrome shielding to vertical edges of features in said H-mask; and

applying the horizontal scattering bars to said H-mask after applying the chrome shielding.

10. A computer program product according to claim 7 , further comprising the steps of:

applying chrome shielding to horizontal edges of features in said V-mask; and

applying the vertical scattering bars to said V-mask after applying the chrome shielding.

11. 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.

12. A device manufacturing method according to claim 11 , wherein step (c) further comprises the steps of assigning chrome to all non-critical features in said H-mask and said V-mask, said non-critical features having a width which is greater than or equal to said predetermined critical width, said non-critical features to be formed in said H-mask and said V-mask utilizing chrome.

13. A device manufacturing method according to claim 12 , wherein said first phase shift and said second phase shift are equal, and said first percentage transmission and said second percentage transmission are equal.

14. A device manufacturing method according to 12 , wherein step (c) further comprises the steps of:

applying chrome shielding to vertical edges of features in said H-mask; and

applying the horizontal scattering bars to said H-mask after applying the chrome shielding.

15. A device manufacturing according to claim 12 , wherein step (c) further comprises the steps of:

applying chrome shielding to horizontal edges of features in said V-mask; and

applying the vertical scattering bars to said V-mask after applying the chrome shielding.

16. 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.

17. A method of imaging a wafer according to claim 16 , further comprising assigning chrome to all non-critical features in said H-mask and said V-mask, said non-critical features having a width which is greater than or equal to said predetermined critical width, said non-critical features to be formed in said H-mask and said V-mask utilizing chrome.

18. A method of imaging a wafer according to claim 17 , wherein said first phase shill and said second phase shill are equal, and said first percentage transmission and said second percentage transmission are equal.

19. A method of imaging a wafer according to claim 17 , further comprising the steps of:

applying chrome shielding to vertical edges of features in said H-mask; and

applying the horizontal scattering bars to said H-mask after applying the chrome shielding.

20. A method of imaging a wafer according to claim 17 , further comprising the steps of:

applying chrome shielding to horizontal edges of features in said V-mask; and

applying the vertical scattering bars to said V-mask after applying the chrome shielding.

21. A method of imaging a wafer according to claim 16 , wherein said first source illumination and said second source illumination are dipole illuminations.

22. A method of imaging a wafer according to claim 16 , wherein said first source illumination is a dipole illumination and said second source illumination is a non-dipole illumination.

23. A method of imaging a wafer according to claim 22 , wherein said second source illumination is one of QUASAR illumination or annular illumination.