Fabrication methods of forming cylindrical vertical SI etched channel 3D switching devices
A method of forming a cylindrical vertical transistor; the method, according to one embodiment, includes: forming a cylindrical pillar from a single block of silicon, forming an oxide layer over an exterior of the cylindrical pillar and exposed surfaces of the block of silicon, coating the oxide layer with a spin-on-glass (SOG), depositing a source mask over a majority of the SOG coating, and removing a portion of the SOG coating and underlying oxide layer, where the portion removed is defined by the source mask. Other systems and methods are also described in additional embodiments herein which provide various different improved processes of forming the cylindrical gate contacts, the source contacts, and/or the drain contacts for vertical transistor structures which also include the aforementioned cylindrical pillar channel structures and cylindrical gate in comparison to conventional surface transistor structures.
1. A method of forming a cylindrical vertical transistor, comprising:
forming a cylindrical pillar from a single block of silicon;
forming an oxide layer over an exterior of the cylindrical pillar and exposed surfaces of the block of silicon;
coating the oxide layer with a spin-on-glass (SOG);
depositing a source mask over a majority of the SOG coating;
removing a portion of the SOG coating and underlying oxide layer, the portion being defined by the source mask, wherein removing the portion of the SOG coating and underlying oxide layer forms a source contact recess which abuts a base of the cylindrical pillar and extends to the silicon block therebelow;
ion-implanting the exposed silicon substrate at a base of the source contact recess; and
depositing a silicide material in the source contact recess, thereby forming a source contact;
activating the ion-implanting by performing a rapid thermal anneal procedure;
depositing a second silicide material over the SOG coating and the source contact;
performing a second rapid thermal anneal procedure;
removing the second silicide material;
removing a remainder of the SOG coating;
coating the oxide layer with a second SOG; and
remove the second SOG coating from vertical sides of the cylindrical pillar and a top of the cylindrical pillar.
2. The method as recited in claim 1 , wherein the second SOG coating forms an angled collar at a base of the cylindrical pillar.
3. The method as recited in claim 1 , wherein the second SOG is removed using a reactive ion etching process.
4. The method as recited in claim 1 , comprising:
depositing doped polysilicon over the second SOG coating and the exposed oxide layer on the vertical sides and the top of the cylindrical pillar; and
removing the doped polysilicon except from the vertical sides of the cylindrical pillar,
wherein the doped polysilicon deposited on the vertical sides of the cylindrical pillar form a gate contact.
5. The method as recited in claim 4 , wherein the doped polysilicon is removed using a maskless reactive-ion etching process.
6. The method as recited in claim 4 , wherein the doped polysilicon is deposited using a chemical vapor deposition process.
7. The method as recited in claim 4 , wherein a thickness of the deposited doped polysilicon is between about 200 angstroms (Å) and about 300 Å.
8. The method as recited in claim 4 , comprising:
depositing a poly silicide material over: the second SOG coating, the oxide layer on the top of the cylindrical pillar, and the doped poly on the vertical sides of the cylindrical pillar;
performing a third rapid thermal anneal procedure; and
removing portions of the poly suicide material that did not react to the third rapid thermal anneal procedure.
9. The method as recited in claim 8 , comprising:
depositing silicon dioxide;
coating the silicon dioxide with a third SOG; and
defining an upper surface of the third SOG coat by performing a chemical-mechanical planarization process,
wherein the chemical-mechanical planarization process exposes a drain contact.
10. The method as recited in claim 9 , comprising:
depositing a source and gate mask; and
simultaneously etching down to the gate contact and the source contact, thereby forming vias.
11. The method as recited in claim 10 , comprising:
depositing a first conductive metallic material in the via which extends to the gate contact; and
depositing a second conductive metallic material in the via which extends to the source contact.
12. The method as recited in claim 11 , wherein the first and second conductive metallic materials are non-magnetic.
13. The method as recited in claim 10 , comprising:
forming a magnetic tunnel junction (MTJ) sensor stack above the drain contact, such that a first end of the MTJ sensor stack is electrically coupled to the drain contact.
14. A magnetic device, comprising:
a plurality of cylindrical vertical transistors formed using the method as recited in claim 13 ,
wherein a second end of the MTJ sensor stack in each of the cylindrical vertical transistors is coupled to a common drain line,
wherein the source contact in each of the cylindrical vertical transistors is coupled to a common source line,
wherein the gate contact in each of the cylindrical vertical transistors is coupled to a common word line.