Methods for isolating portions of a loop of pitch-multiplied material and related structures
Different portions of a continuous loop of semiconductor material are electrically isolated from one another. In some embodiments, the end of the loop is electrically isolated from mid-portions of the loop. In some embodiments, loops of semiconductor material, having two legs connected together at their ends, are formed by a pitch multiplication process in which loops of spacers are formed on sidewalls of mandrels. The mandrels are removed and a block of masking material is overlaid on at least one end of the spacer loops. In some embodiments, the blocks of masking material overlay each end of the spacer loops. The pattern defined by the spacers and the blocks are transferred to a layer of semiconductor material. The blocks electrically connect together all the loops. A select gate is formed along each leg of the loops. The blocks serve as sources/drains. The select gates are biased in the off state to prevent current flow from the mid-portion of the loop's legs to the blocks, thereby electrically isolating the mid-portions from the ends of the loops and also electrically isolating different legs of a loop from each other.
1. A process for forming an integrated circuit, comprising:
forming a plurality of first lines extending along a first direction;
forming a plurality of second lines between the first lines, the second lines extending in pairs along the first direction and having opposing first and second ends, the first ends of each pair being interconnected and the second ends of each pair being interconnected;
selectively removing the first lines;
forming a first block of masking material extending laterally across the first ends of the second lines, the first blocks being over the interconnected first ends of the pairs;
forming a second block of masking material extending laterally across the second ends of the second lines, the second blocks being over the interconnected second ends of the pairs, the first and second blocks being spaced and non-contacting relative to one another, upper surfaces of the second lines being exposed between the first and second blocks;
transferring a pattern formed by the second lines and the first and second blocks of masking material to an underlying semiconductor substrate, thereby forming a plurality of lines of semiconductor material interconnected at each end of the lines of semiconductor material by blocks of semiconductor material; and
doping the lines of semiconductor material.
2. The process of claim 1 , wherein doping the lines of semiconductor material forms source/drain regions, and further comprising:
forming transistor gates directly over active areas in the lines of semiconductor material adjacent the source/drain regions.
3. The process of claim 1 , wherein the forming the second plurality of lines comprises:
etching a layer of material to form the first plurality of lines; and
subsequently forming the second plurality of lines along sidewalls of individual lines comprised by the first plurality of lines.
4. The process of claim 3 , wherein the layer of material is a layer of photoresist.
5. The process of claim 3 , wherein subsequently forming the second plurality of lines comprises:
blanket depositing a layer of spacer material on the first plurality of lines; and
etching the layer of spacer material to define second lines comprised by the second plurality of lines along sidewalls of lines comprised the first plurality lines, the second lines comprising the spacer material.
6. A process for forming an integrated circuit, comprising:
forming a plurality of first lines extending along a first direction;
forming a plurality of second lines between the first lines, the second lines extending along the first direction and having opposing first and second ends;
selectively removing the first lines;
forming a first block of masking material extending laterally across the first ends of the second lines;
forming a second block of masking material extending laterally across the second ends of the second lines, the first and second blocks being spaced and non-contacting relative to one another, upper surfaces of the second lines being exposed between the first and second blocks;
transferring a pattern formed by the second lines and the first and second blocks of masking material to an underlying semiconductor substrate, thereby forming a plurality of lines of semiconductor material interconnected at each end of the lines of semiconductor material by blocks of semiconductor material;
doping the lines of semiconductor material to form source/drain regions;
forming transistor gates directly over active areas in the lines of semiconductor material adjacent the source/drain regions; and
electrically shunting together the transistor gates and associated source/drain regions proximate the ends of the lines of semiconductor material.
7. A method of forming integrated circuitry, comprising:
forming a plurality of spaced apart lines over a substrate material, each of the lines of the plurality having a first end region, a second end region opposing the first end region and an intermediate region extending between the first end region and the second end region, the plurality of spaced apart lines comprising line pairs having interconnected first ends and having interconnected second ends;
forming first and second blocks of material over the spaced apart lines, the first and second blocks being distinct and non-contacting relative to one anther, the first block covering the first end regions and the second block covering the second end regions, the intermediate region of the lines being uncovered, the first and second blocks of material and the intermediate region of the lines forming a pattern;
transferring the pattern into the substrate to form patterned substrate material.