Two-color self-aligned double patterning (SADP) to yield static random access memory (SRAM) and dense logic
First lithography and etching are carried out on a semiconductor structure to provide a first intermediate semiconductor structure having a first set of surface features corresponding to a first portion of desired fin formation mandrels. Second lithography and etching are carried out on the first intermediate structure, using a second mask, to provide a second intermediate semiconductor structure having a second set of surface features corresponding to a second portion of the mandrels. The second set of surface features are unequally spaced from the first set of surface features and/or the features have different pitch. The fin formation mandrels are formed in the second intermediate semiconductor structure using the first and second sets of surface features; spacer material is deposited over the mandrels and is etched back to form a third intermediate semiconductor structure having a fin pattern. Etching is carried out on same to produce the fin pattern.
1. A method of forming a semiconductor region, the method comprising:
providing a first set of features corresponding to a first lithography process, each feature of the first set of features having a first width;
subsequent to providing the first set of features, forming a second set of features corresponding to a second lithography process;
forming a first set of mandrels corresponding to the first set of features and a second set of mandrels corresponding to the second set of features, wherein a first mandrel of the first set of mandrels is adjacent to a first mandrel of the second set of mandrels;
concurrently forming spacers on the first and second sets of mandrels, wherein the mandrels of the first set of mandrels have substantially the first width when the spacers are formed;
removing the first and second sets of mandrels to form an intermediate fin pattern, the intermediate fin pattern comprising:
first and second intermediate fins corresponding to spacers on opposite sides of the first mandrel of the first set of mandrels; and
third and fourth intermediate fins corresponding to spacers on opposite sides of the first mandrel of the second set of mandrels, wherein the second and third intermediate fins are adjacent intermediate fins; and
performing an etch to transfer the intermediate fin pattern to a substrate to form first, second, third, and fourth semiconductor fins.
2. The method of claim 1 , wherein the features of the second set of features each have a second width, and wherein the mandrels of the second set of mandrels have substantially the second width when the spacers are formed.
3. The method of claim 1 , further comprising:
performing the first lithography process using a first mask; and
performing the second lithography process using a second mask.
4. The method of claim 3 , wherein the first mask is different from the second mask.
5. The method of claim 1 , wherein a pitch between the first and second semiconductor fins is different than a pitch between the second and third semiconductor fins.
6. The method of claim 5 , wherein the first, second, third, and fourth semiconductor fins comprise fins of an SRAM.
7. The method of claim 6 , further comprising removing a portion of the third semiconductor fin.
8. The method of claim 6 , further comprising removing a portion of the second semiconductor fin and removing a portion of the third semiconductor fin.
9. The method of claim 6 , wherein a centerline spacing of the first and second semiconductor fins is approximately 56 nm.
10. The method of claim 6 , wherein a centerline spacing of the second and third semiconductor fins is approximately 48 nm.
11. The method of claim 5 , wherein the first, second, third, and fourth semiconductor fins comprise fins of a same transistor.
12. The method of claim 5 , wherein:
the intermediate fin pattern further comprises fifth and sixth intermediate fins corresponding to spacers on opposite sides of a second mandrel of the first set of mandrels;
the fifth intermediate fin is adjacent to the fourth intermediate fin; and wherein:
performing the etch to transfer the intermediate fin pattern to the substrate to form the first, second, third, and fourth semiconductor fins further forms fifth and sixth semiconductor fins.
13. The method of claim 12 , wherein the first, second, third, fourth, fifth, and sixth semiconductor fins are connected by a same gate.
14. The method of claim 11 , wherein a centerline spacing of the first and second semiconductor fins is approximately 30 nm.
15. The method of claim 11 , wherein a centerline spacing of the second and third semiconductor fins is approximately 36 nm.
16. The method of claim 11 , wherein a centerline spacing of the fourth and fifth semiconductor fins is approximately 84 nm.
17. The method of claim 1 , wherein a pitch between the first and second semiconductor fins is approximately the same as a pitch between the second and third semiconductor fins.
18. The method of claim 17 , wherein the first, second, third, and fourth semiconductor fins comprise fins of a same transistor.
19. The method of claim 17 , wherein:
the intermediate fin pattern further comprises fifth and sixth intermediate fins corresponding to spacers on opposite sides of a second mandrel of the first set of mandrels;
the fifth intermediate fin is adjacent to the fourth intermediate fin; and wherein:
performing the etch to transfer the intermediate fin pattern to the substrate to form the first, second, third, and fourth semiconductor fins further forms fifth and sixth semiconductor fins.
20. The method of claim 19 , wherein the first, second, third, fourth, fifth, and sixth semiconductor fins are connected by a same gate.
21. The method of claim 18 , wherein a centerline spacing of the first and second semiconductor fins is approximately 30 nm.
22. The method of claim 19 , wherein a centerline spacing of the fourth and fifth semiconductor fins is approximately 90 nm.