Methods for forming arrays of small, closely spaced features
Methods of forming arrays of small, densely spaced holes or pillars for use in integrated circuits are disclosed. Various pattern transfer and etching steps can be used, in combination with pitch-reduction techniques, to create densely-packed features. Conventional photolithography steps can be used in combination with pitch-reduction techniques to form superimposed patterns of crossing elongate features with pillars at the intersections. Spacers are simultaneously applied to sidewalls of both sets of crossing lines to produce a pitch-doubled grid pattern. The pillars facilitate rows of spacers bridging columns of spacers.
1. An array of features for computer memory fabrication, comprising:
a middle tier comprising a grid with crossing grid lines extending on a same level, holes between the grid lines, and grid line intersections where the grid lines cross, the grid lines having sidewalls;
a lower tier comprising a surface upon which the grid is positioned, the holes extending to the lower tier; and
a higher tier comprising pillars positioned on the grid at the grid line intersections, the pillars having sidewalls and substantially localized at the grid line intersections.
2. The array of claim 1 , further comprising spacer material adhered to the sidewalls of the grid lines and the sidewalls of the pillars.
3. The array of claim 2 , wherein the spacer material forms continuous spacer lines, each spacer line serially and alternatingly adhering to sidewalls of grid lines and to sidewalls of pillars and extending along the length of each of the grid lines.
4. The array of claim 2 , wherein the spacer material forms continuous undulating spacer lines that adhere to the sidewalls of the grid lines and to the sides of the pillars, wherein the spacer material defines sides of the holes between the grid lines.
5. The array of claim 2 , wherein the spacer material forms a spacer grid having crossing spacer lines that adhere to the grid lines and bridge across the crossing grid lines by adhering to the pillar sidewalls.
6. The array of claim 1 , wherein the grid and the pillars comprise the same material.
7. The array of claim 1 , wherein the grid and the pillars comprise amorphous carbon.