Structure and method for deep trench capacitor with reduced deformation

1 . A method, comprising:

patterning a substrate to form trenches;

etching the substrate, thereby modifying the trenches with round tips;

forming a stack including conductive layers and dielectric layers in the trenches, wherein the conductive layers and the dielectric layers alternate with one another within the stack;

forming an insulating compressive film of a compressive stress in the trenches, thereby sealing voids in the trenches, wherein the voids are entirely enclosed within the insulating compressive film and are spaced from the conductive layers by the insulating compressive film; and

forming conductive plugs connected to the conductive layers, respectively.

2 . The method of claim 1 , wherein the forming the insulating compressive film in the trenches includes performing an annealing process in an oxygen environment with annealing temperature ranging between 800° C. and 1200° C.

3 . The method of claim 1 , wherein the forming the insulating compressive film in the trenches includes forming at least one of a silicon oxide (SiO 2 ) layer, a silicon nitride layer, a polysilicon layer, a silicon carbide layer, and a combination thereof.

4 . The method of claim 1 , wherein the forming the insulating compressive film in the trenches includes performing a chemical vapor deposition process to form the insulating compressive film.

5 . The method of claim 4 , wherein the forming the insulating compressive film in the trenches includes forming at least one of a nitrogen-free anti-reflection layer (NFARL), a silicon oxide (SiO 2 ) layer, an undoped silica glass (USG) layer, a silicon carbide layer, and a combination thereof.

6 . The method of claim 1 , wherein

the patterning the substrate to form the trenches includes forming a first hard mask having first openings on the substrate; and

applying a first etching process to the substrate through the first openings of the first hard mask.

7 . The method of claim 6 , wherein the etching the substrate includes

forming a second hard mask having second openings on the substrate; and

applying a second etching process to the substrate through the second openings of the second hard mask, wherein the second openings of the second hard mask are different from the first openings of the first hard mask.

8 . The method of claim 1 , wherein the patterning the substrate to form the trenches includes patterning the substrate to form the trenches configured into a plurality of deep trench unit cells, wherein each of the deep trench unit cells includes a plurality of deep trenches longitudinally oriented in a same direction.

9 . The method of claim 8 , wherein the plurality of deep trench unit cells includes

a first deep trench unit cell having first deep trenches longitudinally oriented along a first direction;

a second deep trench unit cell having second deep trenches longitudinally oriented along a second direction;

a third deep trench unit cell having third deep trenches longitudinally oriented along a third direction; and

the first, second and third directions are different from each other.

10 . The method of claim 9 , wherein

the first and second directions are oriented with 120° therebetween;

the second and third directions are oriented with 120° therebetween; and

the third and first directions are oriented with 120° therebetween.

11 . The method of claim 8 , wherein each of the plurality of deep trench unit cells occupies an area having a shape of a parallelogram.

12 . A method, comprising:

patterning a substrate to form deep trenches;

etching the substrate, thereby modifying the deep trenches;

forming a stack including conductive layers and dielectric layers alternatively stacked and folded in the deep trenches; and

forming an insulating film of a compressive stress in the deep trenches, thereby sealing voids in the deep trenches, wherein the deep trenches are configured into a plurality of deep trench unit cells, wherein the deep trenches in each of the deep trench unit cells are oriented in a same direction, wherein the deep trenches in adjacent deep trench unit cells are oriented in different directions, and wherein the voids are entirely enclosed within the insulating film and are spaced from the conductive layers by the insulating film.

13 . The method of claim 12 , further comprising forming conductive plugs connected to the conductive layers, respectively, wherein

the patterning the substrate to form the trenches includes forming a first hard mask having first openings on the substrate;

applying a first etching process to the substrate through the first openings of the first hard mask; and

the etching the substrate further includes forming a second hard mask having second openings on the substrate, and applying a second etching process to the substrate through the second openings of the second hard mask, wherein the second openings of the second hard mask are different from the first openings of the first hard mask.

14 . The method of claim 12 , wherein the plurality of deep trench unit cells includes

a first deep trench unit cell having first deep trenches disposed in a first region and longitudinally oriented along a first direction;

a second deep trench unit cell having second deep trenches disposed in a second region and longitudinally oriented along a second direction;

a third deep trench unit cell having third deep trenches disposed in a third region longitudinally oriented along a third direction; and

the first, second and third directions are different from each other.

15 . The method of claim 12 , wherein

each of the plurality of deep trench unit cells is shaped to one of a parallelogram and a hexagon; and

the deep trenches in adjacent deep trench unit cells are not connected.

16 . The method of claim 12 , wherein the forming the insulating film in the deep trenches includes forming the insulating film of a compressive stress by performing an annealing process in an oxygen environment with annealing temperature ranging between 800° C. and 1200° C.

17 . A method, comprising:

forming a first hard mask having first openings on a substrate;

applying a first etching process to the substrate through the first openings of the first hard mask;

forming a second hard mask having second openings on the substrate;

applying a second etching process to the substrate through the second openings of the second hard mask, thereby forming deep trenches, wherein the second openings of the second hard mask are different from the first openings of the first hard mask;

forming a stack including conductive layers and dielectric layers alternatively stacked and folded in the deep trenches; and

forming an insulating film in the deep trenches, thereby sealing voids in the deep trenches, wherein the deep trenches are configured into a plurality of deep trench unit cells, wherein the deep trenches in each of the deep trench unit cells are oriented in a same direction, and wherein the deep trenches in adjacent deep trench unit cells are oriented in different directions, wherein the voids are entirely enclosed within the insulating film and are spaced from the conductive layers by the insulating film.

18 . The method of claim 17 , further comprising forming conductive plugs connected to the conductive layers, respectively, wherein the conductive plugs are configured in a line within a region between adjacent the deep trench unit cells.

19 . The method of claim 17 , wherein the plurality of deep trench unit cells includes

a first deep trench unit cell having first deep trenches disposed in a first region and longitudinally oriented along a first direction;

a second deep trench unit cell having second deep trenches disposed in a second region and longitudinally oriented along a second direction;

a third deep trench unit cell having third deep trenches disposed in a third region longitudinally oriented along a third direction; and

the first, second and third directions are different from each other.

20 . The method of claim 17 , wherein

each of the plurality of deep trench unit cells is shaped to one of a parallelogram and a hexagon; and

the deep trenches in adjacent deep trench unit cells are not connected.