Method of forming microelectronic or micromechanical structures
The invention relates to transferring, in one exposure, a single-mask feature to form two features on an underlying material. Specifically, a doubled walled structure (i.e. a center opening flanked by adjacent openings) is formed. Advantageously, the openings may be sub-resolution openings. The center opening may be a line flanked by two other lines. The center opening may be circular and surrounded by an outer ring, thus forming a double wall ring structure. In an electronic fuse embodiment, the double wall ring structure is a via filled with a conductor that contacts a lower and upper level metal. In deep trench embodiment, the double wall ring structure is a deep trench in a semiconductor substrate filled with insulating material. In such a way the surface area of the trench is increased thereby increasing capacitance.
1. A method of making a double walled structure, the method comprising:
forming a center opening in a target material, wherein forming the center opening in the target material includes:
forming an opening in a photoresist to expose an upper hardmask wherein the upper hardmask is above the target material;
etching, using a first etch, to form a first opening in the upper hardmask and the center opening in the target material; and
forming at least one lateral opening in the target material after the forming of the center opening in the target material, wherein the forming of the at least one lateral opening includes:
etching, using a second etch, a second opening in the upper hardmask wherein the second opening is larger than first opening in the upper hardmask; and
etching, using a third etch, the at least one lateral opening in the target material,
wherein the at least one lateral opening is bordered by an outer wall and an inner wall and wherein the inner wall separates the center opening from the at least one lateral opening.
2. The method of claim 1 , wherein the center opening is sub-resolution relative to the upper hardmask.
3. The method of claim 2 , wherein the at least one lateral opening is sub- resolution relative to the upper hardmask.
4. The method of claim 1 ,
wherein the center opening is smaller than the opening in the photoresist.
5. The method of claim 1 , wherein the first etch is a polymerizing etch.
6. The method of claim 5 , wherein the etching using a first etch further comprises:
etching the upper hardmask; and
etching a lower hardmask wherein the lower hardmask is between the upper hardmask and the target material;
wherein a polymer is created on sidewalls of the center opening.
7. The method of claim 6 , wherein
the third etch,
includes using the polymer as a third mask to create the inner wall.
8. The method of claim 1 , further comprising:
filling the center and lateral openings with a fill material; and
planarizing the fill material to be coplanar with the outer wall such that a top surface of the inner wall is covered with the fill material.
9. The method of claim 1 , further comprising:
filling the center and lateral openings with a fill material; and
planarizing the fill material to be coplanar with the inner wall.
10. The method of claim 1 , wherein the etching of the upper hard mask includes etching the upper hard mask in a tapering fashion.
11. The method of claim 6 , wherein the etching of the lower hard mask includes etching the lower hard mask in a tapering fashion.
12. The method of claim 1 , wherein the second opening includes a top critical dimension that is larger than the opening in the photoresist and a bottom critical dimension that is smaller than the opening in the photoresist.
13. The method of claim 1 , wherein the forming of the at least one lateral opening includes forming a first lateral opening and a second lateral opening, and
wherein the center opening is disposed between the first lateral opening and the second lateral opening.
14. A method of making a double walled structure, the method comprising:
providing a stack including a target material on a substrate, a lower hardmask over the target material, an upper hardmask over the lower hardmask, and a photoresist over the upper hardmask;
forming an first opening in the photoresist to expose a portion of the upper hardmask thereunder;
etching, using a first etch, to create a center opening in the target material;
etching, using a second etch, to create a second opening in the upper hardmask, wherein the second opening is larger than the center opening; and
etching, using a third etch, to create lateral openings in the target material on opposing sides of the center opening,
wherein the lateral openings are each bordered by an outer wall and an inner wall and wherein the inner wall separates the center opening from each of the lateral openings.
15. The method of claim 14 , wherein the center opening is smaller than the first opening in the photoresist.
16. The method of claim 14 , wherein the first etch is a polymerizing etch.
17. The method of claim 16 , wherein the etching using a first etch further comprises:
etching the upper hardmask; and
etching the lower hardmask,
wherein a polymer is created on sidewalls of the center opening during the etch.
18. The method of claim 17 , wherein the third etch includes using the polymer as a third mask to create the inner wall.
19. The method of claim 14 , further comprising:
filling the center and lateral openings with a fill material; and
planarizing the fill material to be coplanar with the outer wall such that a top surface of the inner wall is covered with the fill material.
20. The method of claim 14 , further comprising:
filling the center and lateral openings with a fill material; and
planarizing the fill material to be coplanar with the inner wall.