Methods for isolation process control and structures thereof
Methods for forming a dielectric isolation region between two active regions are disclosed herein. A mandrel is formed on a substrate, then etched to form a trench. Spacers are formed on the sidewalls of the mandrel. The mandrel is removed, and the substrate is etched to form fins extending in a first direction in the two active regions, and of fins extending in a second direction. A mask is formed that exposes the substrate between the fins extending in the second direction. The substrate is etched to form a trench. The trench is filled with a dielectric material up to the top of the fins to form the dielectric isolation region. The methods provide better depth control during etching between the two active regions, and also permit the trench to extend deeper into the substrate due to reduced depth/width ratios during the etching steps.
1 . A method for forming a dielectric structure between a first active region and a second active region, comprising:
forming a mandrel extending in a first axis over a substrate;
etching to form a trench in the mandrel in a second axis normal to the first axis in a desired location for the dielectric structure;
forming spacers on sidewalls of the mandrel;
removing the mandrel;
etching into the substrate to form at least a first fin located in the first active region that extends in the first axis, a second fin located in the second active region that extends in the first axis, and a plurality of fins extending in the second axis;
removing the spacers;
forming a CPODE etch mask that exposes the substrate between the plurality of fins extending in the second axis; and
etching into the substrate through the CPODE etch mask to form a trench;
filling the trench with a dielectric material up to at least a fin height, to form the dielectric structure between the first active region and the second active region.
2 . The method of claim 1 , wherein the etching into the substrate also forms a third fin in the first active region that extends in the first axis and a fourth fin in the second active region that extends in the first axis, and wherein the method further comprises:
forming a fin etch mask that exposes the third fin and the fourth fin; and
etching to remove the third fin and the fourth fin.
3 . The method of claim 2 , wherein the third fin and the fourth fin are removed prior to forming the CPODE etch mask, or after filling the trench with the dielectric material.
4 . The method of claim 2 , wherein a portion of the plurality of fins extending in the second axis are also removed during the etching to remove the third fin and the fourth fin.
5 . The method of claim 1 , further comprising, prior to removing the mandrel:
forming a spacer etch mask that exposes at least one spacer formed on one sidewall of the mandrel extending in the first axis; and
etching to remove the exposed at least one spacer.
6 . The method of claim 1 , wherein the CPODE etch mask also exposes at least a portion of a fin extending in the second axis.
7 . The method of claim 1 , wherein the plurality of shorter fins extending in the second axis are not covered by the dielectric material that forms the dielectric structure.
8 . The method of claim 1 , wherein the dielectric structure has a depth of about 1100 angstroms to about 1300 angstroms.
9 . The method of claim 1 , wherein the dielectric structure has a width of about 150 angstroms to about 400 angstroms.
10 . A method for forming a first active region and a second active region, comprising:
forming a mandrel over a substrate;
etching to form a trench in the mandrel;
etching into the substrate to form a first fin and a third fin located in the first active region, a second fin and a fourth fin located in the second active region, and a plurality of fins separating the first active region and the second active region;
forming a fin etch mask that exposes the third fin and the fourth fin;
etching to remove the third fin and the fourth fin;
forming a CPODE etch mask that exposes the substrate between the plurality of fins separating the first active region and the second active region;
etching into the substrate through the CPODE etch mask to form a trench; and
filling the trench with a dielectric material to form an isolation region between the first active region and the second active region.
11 . The method of claim 10 , wherein the third fin and the fourth fin are removed prior to forming the CPODE etch mask, or after filling the trench with the dielectric material.
12 . The method of claim 10 , wherein a portion of the plurality of fins separating the first active region and the second active region are also removed during the etching to remove the third fin and the fourth fin.
13 . The method of claim 10 , wherein the CPODE etch mask also exposes at least a portion of a fin in the plurality of fins separating the first active region and the second active region.
14 . The method of claim 10 , wherein the plurality of fins separating the first active region and the second active region are not covered by the dielectric material that forms the isolation region.
15 . The method of claim 10 , wherein a plurality of hardmask layers are located between the substrate and the mandrel.
16 . The method of claim 10 , wherein the isolation region has a depth of about 1100 angstroms to about 1300 angstroms.
17 . The method of claim 10 , wherein the isolation region has a width of about 20 nanometers to about 30 nanometers.
18 . A method for forming a dielectric structure between a first active region and a second active region, comprising:
forming a mandrel over a substrate;
etching to form a trench in the mandrel;
etching into the substrate to form at least a first fin located in the first active region that extends in a first axis, a second fin located in the second active region that extends in the first axis, and a plurality of fins extending in a second axis;
forming a CPODE etch mask that exposes the substrate between the plurality of fins extending in the second axis; and
etching into the substrate through the CPODE etch mask to form a trench;
filling the trench with a dielectric material to form the dielectric structure between the first active region and the second active region.
19 . The method of claim 18 , wherein the etching into the substrate also forms a third fin in the first active region that extends in the first axis and a fourth fin in the second active region that extends in the first axis, and wherein the method further comprises:
forming a fin etch mask that exposes the third fin and the fourth fin; and
etching to remove the third fin and the fourth fin.
20 . The method of claim 18 , further comprising, prior to removing the mandrel:
forming a spacer etch mask that exposes at least one spacer formed on one sidewall of the mandrel extending in the first axis; and
etching to remove the exposed at least one spacer.