Patterning mask and method of formation of mask using step double patterning
A method of forming a mask for use in fabricating an integrated circuit includes forming first non-removable portions of a photoresist material through a mask having a plurality of apertures, shifting the mask, forming second non-removable second portions of the photoresist material overlapping the first portions, and removing removable portions of the photoresist material arranged between the first and second portions. The formed photoresist mask may be used to form vias in an integrated circuit. The pattern of vias produced have the capability to exceed the current imaging resolution of a single exposure treatment.
1. A method of forming an integrated circuit structure, the method comprising:
arranging a mask having a plurality of apertures over a first material;
making first portions of the first material non-removable by exposure through the plurality of apertures;
shifting the mask so that the plurality of apertures overlap a portion of the first portions of the first material; and
making second portions of the first material non-removable by exposure through the plurality of apertures, wherein the first portions and the second portions overlap in such a way so as to produce removable portions of the first material arranged between the first portions and second portions; and
removing the removable portions of the first material.
2. The method of claim 1 , further comprising removing the removable portions to form a plurality of openings in the first material.
3. The method of claim 2 , further comprising providing a second material below the first material and etching the second material through the openings in the first material to form a plurality of vias in second material.
4. The method of claim 3 , further comprising forming electrical connections in the plurality of vias formed in the second material.
5. The method of claim 4 , further comprising forming a conductive material over and in contact with at least one of the electrical connections.
6. The method of claim 1 , wherein the first material is a photoresist material.
7. The method of claim 6 , wherein formation of the first portions of the first material comprises exposing the first portions of the first material to radiation and formation of the second portions of the second material comprises exposing the second portions of the second material to radiation.
8. The method of claim 1 , wherein the plurality of apertures are square shaped.
9. The method of claim 8 , wherein the plurality of apertures are arranged at a forty-five degree angle to an edge of the mask.
10. The method of claim 8 , wherein the plurality of apertures are arranged in a grid.
11. The method of claim 10 , wherein the mask is shifted by a distance such that the center of the apertures are aligned at or approximately at locations centered between four first portions.
12. The method of claim 10 , wherein the plurality of apertures are arranged such that a pitch of a point of a square shape measured diagonally across the square shape is at or about 1.41 times the pitch of a point of a square shape measured along an edge of the square shape.
13. The method of claim 1 , wherein the plurality of apertures are in the shape of a first square overlapped by four smaller squares, wherein each of the smaller square overlaps one of the corners of the first square.
14. The method of claim 13 , wherein the plurality of apertures are arranged in a grid.
15. The method of claim 14 , wherein the mask is shifted by a distance such that the center of the apertures are aligned at or approximately at locations centered between four cured first portions.
16. The method of claim 14 , wherein the plurality of apertures are arranged such that a pitch of a point of a smaller square measured diagonally across the aperture is at or about 1.41 times the pitch of a point of a smaller square measured along an edge of the aperture.
17. A method of forming electrical connections in an integrated circuit, the method comprising:
providing a material to be patterned over a substrate;
providing a photoresist material over the material to be patterned;
providing a mask having a plurality of apertures over the photoresist material;
exposing the photoresist material through the plurality of apertures during a first exposure to form non-removable first portions of the photoresist material;
shifting the mask so that the plurality of apertures overlap a portion of the first portions of the photoresist material;
exposing the photoresist material through the plurality of apertures during a second exposure to form non-removable second portions of the photoresist material;
removing removable portions of the photoresist located between the overlapping first portions and second portions of the photoresist;
etching the material to be patterned through areas previously occupied by the removable portions of the photoresist to form a plurality of openings.
18. The method of claim 17 , wherein the openings are vias.
19. The method of claim 18 , further comprising filling the vias with conductive material to form a plurality of electrical connections.
20. The method of claim 17 , wherein the plurality of apertures comprise square shapes and are arranged in a grid.
21. The method of claim 20 , wherein the plurality of apertures are arranged such that a pitch of a point of a square shape measured diagonally across the square shape is 1.41 times the pitch of a point of a square shape measured along an edge of the square shape.
22. The method of claim 20 , wherein the plurality of apertures each comprise five overlapping square shapes.
23. A method of forming a mask, comprising:
changing a physical property a first material by irradiating the first material a first time through a mask having a plurality of apertures;
shifting the mask relative to the first material and irradiating the material a second time through the mask to change the physical property of the first material not changed by said first irradiating, and
producing a mask from the first material by removing one of either portions of the first material having a changed physical property or portions of the first material which do not have a changed physical property.
24. The method of claim 23 , further comprising removing portions of the first material which do not have a changed physical property.