Method for fabricating pitch-doubling pillar structures
View Patent ↗A method of making a semiconductor device includes forming at least one device layer over a substrate, forming at least two spaced apart features over the at least one device layer, forming sidewall spacers on the at least two features, filling a space between a first sidewall spacer on a first feature and a second sidewall spacer on a second feature with a filler feature, selectively removing the sidewall spacers to leave the first feature, the filler feature and the second feature spaced apart from each other, and etching the at least one device layer using the first feature, the filler feature and the second feature as a mask.
1. A method of making a pillar shaped nonvolatile memory device array, comprising:
forming a plurality of bottom electrodes over a substrate;
forming at least one semiconductor device layer over the plurality of bottom electrodes;
forming a plurality of spaced apart features over the at least one semiconductor device layer;
providing alignment edge features adjacent to a device array boundary, wherein the alignment edge features have a larger size than the plurality of spaced apart features;
forming sidewall spacers on the plurality of spaced apart features;
forming a filler film over and between the plurality of spaced apart features;
planarizing the filler film to expose upper portions of the plurality of spaced apart features and upper portions of the sidewall spacers to leave a plurality of filler features located between the sidewall spacers;
forming a photoresist layer over the plurality of filler features and over the plurality of spaced apart features;
exposing the photoresist layer using the alignment edge features during alignment;
patterning the exposed photoresist layer to form a photoresist pattern covering a device array area;
etching the filler film in areas outside of the device array boundary that are not covered by the photoresist pattern to remove the filler film from areas outside of the device array boundary;
selectively removing the sidewall spacers to leave the plurality of spaced apart features and the plurality of filler features spaced apart from each other;
etching the at least one semiconductor device layer using the plurality of spaced apart features and the plurality of filler features as a mask to form a plurality of pillar shaped diode containing nonvolatile memory cells; and
forming a plurality of upper electrodes contacting the plurality of nonvolatile memory cells.
2. The method of claim 1 , wherein:
the plurality of spaced apart features and the plurality of filler features comprise a first material and the sidewall spacers comprise a second material different from the first material; and
the step of selectively removing comprises selectively etching the second material of the sidewall spacers without substantially removing the first material.
3. The method of claim 1 , wherein:
the plurality of spaced apart features comprise a first material, and the plurality of filler features comprise a second material and the sidewall spacers comprise a third material different from the first and the second material; and
the step of selectively removing comprises selectively etching the third material of the sidewall spacers without substantially removing the first or the second material.
4. The method of claim 1 , wherein:
the plurality of spaced apart features comprise tungsten covered by a silicon nitride or titanium nitride hard mask material;
the plurality of filler features comprise tungsten; and
the sidewall spacers comprise silicon oxide.
5. The method of claim 4 , wherein the plurality of spaced apart features comprise at least a portion of the upper electrodes.
6. The method of claim 1 , wherein:
the plurality of spaced apart features comprise silicon oxide;
the plurality of filler features comprise silicon oxide; and
the sidewall spacers comprise silicon nitride.
7. The method of claim 6 , further comprises removing the plurality of spaced apart features and the plurality of filler features after the step of etching the at least one semiconductor device layer.
8. The method of claim 1 , wherein each of the plurality of spaced apart features has a substantially cylindrical shape and each of the plurality of filler features has a substantially rectangular or square shape with concave sidewalls.
9. The method of claim 1 , wherein the step of forming sidewall spacers comprises forming the sidewall spacers on the plurality of features, such that the sidewalls spacers on adjacent features along at least two predetermined directions contact each other to form fully enclosed interstitial spaces located between the sidewall spacers.