Vertical FinFet formation using directional deposition
Disclosed herein are approaches for forming contacts in a 4F 2 vertical dynamic random-access memory device. One method includes forming a hardmask over a plurality of pillars and over a plurality of anchors, wherein the pillars are separated from one another by a STI, and removing the STI and etching through the hardmask to form a plurality of gate trenches. The method may further include delivering a capping material to the pillars at a non-zero angle relative to a perpendicular extending from an upper surface of the pillars, wherein the capping material forms a capping layer along an upper portion of the pillars without forming the capping layer along a lower portion of the pillars. The method may further include etching the pillars to trim the lower portion of the pillars, and forming a plurality of contacts in the upper portion of the pillars.
1. A method, comprising:
forming a hardmask over a plurality of pillars and over a plurality of anchors, wherein the plurality of pillars are separated from one another by a shallow trench isolation (STI);
removing the STI and etching through the hardmask to form a plurality of gate trenches;
delivering a capping material to the plurality of pillars at a non-zero angle relative to a perpendicular extending from an upper surface of the plurality of pillars, wherein the capping material forms a capping layer along an upper portion of the plurality of pillars without forming the capping layer along a lower portion of the plurality of pillars;
etching the plurality of pillars to trim the lower portion of the plurality of pillars; and
forming a plurality of contacts in the upper portion of the plurality of pillars.
2. The method of claim 1 , further comprising:
forming the plurality of pillars from an epitaxial layer, wherein the epitaxial layer is formed atop a buried bitline, and wherein the plurality of pillars extend in a first direction; and
forming a plurality of anchor trenches through the plurality of pillars and the STI, wherein the plurality of anchor trenches extend in a second direction, and wherein each anchor of the plurality of anchors is formed within a corresponding anchor trench of the plurality of anchor trenches.
3. The method of claim 2 , wherein forming the plurality of pillars comprises:
forming a plurality of pillar trenches through the epitaxial layer and through the buried bitline; and
depositing an STI material within the plurality of pillar trenches.
4. The method of claim 2 , further comprising:
removing the capping layer;
forming a gate device within each of the plurality of gate trenches; and
forming the plurality of contacts in the upper portion of the plurality of pillars after forming the gate device within each of the plurality of gate trenches.
5. The method of claim 2 , further comprising forming the plurality of anchors by: depositing a nitride layer within the plurality of anchor trenches; and
depositing an oxide layer over the nitride layer.
6. The method of claim 1 , further comprising forming the capping layer atop the upper surface of the plurality pillars and atop the plurality of anchors.
7. The method of claim 1 , wherein etching the plurality of pillars to trim the lower portion of the plurality of pillars increases a first width of a lower section of each gate trench of the plurality of gate trenches.
8. The method of claim 7 , wherein a second width of an upper section of each gate trench of the plurality of gate trenches is less than the first width of the lower section of each gate trench of the plurality of gate trenches.
9. The method of claim 1 , further comprising forming an upper source/drain and a lower source/drain in each of the plurality of pillars.
10. A method of forming a 4F 2 vertical dynamic random-access memory device, the method comprising:
forming a hardmask over a plurality of pillars and over a plurality of anchors;
etching through the hardmask to form a plurality of gate trenches and a plurality of vertical pillar structures;
delivering a capping material to the plurality of vertical pillar structures at a non-zero angle relative to a perpendicular extending from an upper surface of the plurality of vertical pillar structures, wherein the capping material forms a capping layer along an upper portion of the plurality of vertical pillar structures without forming the capping layer along a lower portion of the plurality of vertical pillar structures;
etching the plurality of vertical pillar structures to trim the lower portion of the plurality of vertical pillar structures; and
forming a plurality of contacts in the upper portion of the plurality of vertical pillar structures.
11. The method of claim 10 , further comprising:
forming the plurality of pillars from an epitaxial layer, wherein the epitaxial layer is formed atop a buried bitline, and wherein the plurality of pillars extend in a first direction; and
forming a plurality of anchor trenches through the plurality of pillars and through a shallow trench isolation, wherein the plurality of anchor trenches extend in a second direction, and wherein each anchor of the plurality of anchors is formed within a corresponding anchor trench of the plurality of anchor trenches.
12. The method of claim 11 , wherein forming the plurality of pillars comprises:
forming a plurality of pillar trenches through the epitaxial layer and through the buried bitline; and
depositing a source trench isolation within the plurality of pillar trenches.
13. The method of claim 11 , further comprising:
removing the capping layer;
forming a gate device within each of the plurality of gate trenches;
forming the plurality of contacts in the upper portion of the plurality of vertical pillar structures after forming the gate device within each of the plurality of gate trenches; and
forming an upper source/drain and a lower source/drain in each of the plurality of vertical pillar structures, wherein the plurality of contacts are positioned over the upper source/drain.
14. The method of claim 11 , further comprising forming the plurality of anchors by: depositing a nitride layer within the plurality of anchor trenches; and
depositing an oxide layer over the nitride layer.
15. The method of claim 10 , further comprising forming the capping layer atop the upper surface of the plurality vertical pillar structures and atop the plurality of anchors.
16. The method of claim 10 , wherein etching the plurality of pillars to trim the lower portion of the plurality of pillars increases a first width of a lower section of each gate trench of the plurality of gate trenches, and wherein a second width of an upper section of each gate trench of the plurality of gate trenches is less than the first width of the lower section of each gate trench of the plurality of gate trenches.