Double patterning method for creating a regular array of pillars with dual shallow trench isolation
A method is disclosed for forming vertical bipolar junction transistors including a regular array of base contact pillars and emitter contact pillars with a width below the minimum lithographical resolution F of the lithographic technique employed. In an embodiment, the pillar array features have a dimension of approximately F/2, though this dimension could be reduced down to other values compatible with embodiments of the invention. A storage element, such as a phase change storage element, can be formed above the regular array of base contact pillars and emitter contact pillars.
1. A method of fabricating an array of vertical bipolar junction transistors, the method comprising:
forming an array of base contact pillars and an array of emitter contact pillars with a lithographic technique having a minimum lithographical resolution F, the base contact pillars and the emitter contact pillars each having a width below the minimum lithographical resolution F, the forming of the array of base contact pillars and the array of the emitter contact pillars including forming a first set of shallow trench isolation regions extending at least to a first doped region and forming a second set of shallow trench isolation regions which do not extend to the first doped region, the first doped region being a common collector, the second set of shallow trench isolation regions being formed substantially perpendicular to the first set of shallow trench isolation regions; and
forming a storage element above the array of base contact pillars and the array of emitter contact pillars.
2. The method of claim 1 , further comprising forming a first level base contact plug in electrical contact with a plurality of base contact pillars.
3. The method of claim 1 , wherein the base contact pillars and emitter contact pillars have a width of F/2.
4. The method of claim 1 , wherein the first doped region comprises a p-type material.
5. The method of claim 1 , wherein forming the array of base contact pillars and the array of emitter contact pillars comprises a first double patterning technique and a second double patterning technique.
6. The method of claim 5 , wherein the first double patterning technique and the second double patterning technique comprise:
partially removing a dielectric material from between a patterned etch stop layer after filling a shallow trench isolation with the dielectric material; and
removing the patterned etch stop layer after partially removing the dielectric material from between the patterned etch stop layer.
7. The method of claim 5 , wherein the first double patterning technique includes:
forming a first dielectric layer, a first etch stop layer, and a first fin patterning layer over a substrate;
lithographically patterning the fin patterning layer with an array of first strips having a width approximately equal to a minimum lithographical resolution F;
forming an array of first fins having a width of approximately F/2;
depositing a conformal layer over the fins, the conformal layer having a thickness of approximately F/2 on the sidewalls of the fins;
anisotropically etching back the fins;
selectively removing the fins; and
etching through the first etch stop layer and first dielectric layer, and into the substrate to form a first set of shallow trench isolation regions which define first-direction active area strips, a patterned first dielectric layer, and patterned first etch stop layer.
8. The method of claim 7 , further comprising:
depositing a second dielectric layer over the substrate filling the first set of shallow trench isolation regions and covering the top surface of the patterned etch stop layer;
removing the second dielectric layer on top of the patterned etch stop layer;
partially removing the second dielectric layer between patterned etch stop layer; and
selectively removing the patterned etch stop layer.
9. The method of claim 8 , wherein partially removing the second dielectric layer between the patterned etch stop layer comprises removing a thickness corresponding to at least 80% of the original thickness of the patterned etch stop layer.
10. The method of claim 8 , further comprising:
forming a second etch stop layer and a second fin patterning layer over the substrate;
lithographically pattering the second fin patterning layer with an array of second strips having a width approximately equal to a minimum lithographical resolution F;
forming an array of second fins having a width of approximately F/2;
depositing a second conformal layer over the second fins, the second conformal layer having a thickness of approximately F/2 on the sidewalls of the second fins;
anisotropically etching back the second fins;
selectively removing the second fins; and
etching through the second etch stop layer and first dielectric layer, and into the substrate to form a second set of shallow trench isolation regions defining second-direction active area strips perpendicular to the first-direction active area strips, a patterned first dielectric layer, and patterned second etch stop layer.
11. The method of claim 10 , further comprising:
depositing a third dielectric layer over the substrate filling the second set of shallow trench isolation regions and covering the top surface of the patterned second etch stop layer;
removing the third dielectric layer on top of the patterned second etch stop layer;
partially removing the third dielectric layer between patterned second etch stop layer; and
selectively removing the patterned second etch stop layer.
12. The method of claim 10 , further comprising:
forming a p+ dopant into to the pillars which will become p+ emitter contacts; and
forming an n+ dopant into the pillars which will become n+ base contacts.
13. A method of fabricating an electronic device, the method comprising:
forming an array of base contact pillars and an array of emitter contact pillars with a lithographic technique having a minimum lithographical resolution F, the base contact pillars and the emitter contact pillars each having a width below the minimum lithographical resolution F, the forming of the array of base contact pillars and the array of the emitter contact pillars including a double-patterning technique comprising forming a first set of shallow trench isolation regions extending at least to a first doped region and forming a second set of shallow trench isolation regions which do not extend to the first doped region, the double-patterning technique including
partially removing a dielectric material from between a patterned etch stop layer after filling each set of shallow trench isolation regions with the dielectric material; and
removing the patterned etch stop layer after partially removing the dielectric material from between the patterned etch stop layer; and
forming a storage element above the array of base contact pillars and the array of emitter contact pillars.
14. A method of fabricating an array of vertical bipolar junction transistors, the method comprising:
forming an array of base contact pillars and an array of emitter contact pillars with a lithographic technique having a minimum lithographical resolution F, the base contact pillars and the emitter contact pillars each having a width below the minimum lithographical resolution F, the forming of the array of base contact pillars and the array of the emitter contact pillars including forming a first set of shallow trench isolation regions extending at least to a first doped region and forming a second set of shallow trench isolation regions which do not extend to the first doped region, the forming of the array of base contact pillars and the array of emitter contact pillars comprises a first double patterning technique and a second double patterning technique, the first double patterning technique and the second double patterning technique comprise:
partially removing a dielectric material from between a patterned etch stop layer after filling a shallow trench isolation with the dielectric material; and
removing the patterned etch stop layer after partially removing the dielectric material from between the patterned etch stop layer; and
forming a storage element above the array of base contact pillars and the array of emitter contact pillars.