Method for manufacturing magnetic tunnel junction pillars using photolithographically directed block copolymer self-assembly and organometallic gas infusion
A method for manufacturing a magnetic random access memory array at a density greater than would be possible using photolithography. A template is formed having a pattern that is configured to define a memory array. A block copolymer material is deposited onto the template and annealed to form narrow cylinders of ordered block copolymer material. A metal oxide is then diffused into the cylinders to form narrow metal oxide cylinders. The metal oxide cylinders can then be used as mask structures to pattern a hard mask layer. An ion milling process can then be performed to transfer the image of the patterned hard mask onto an underlying magnetic memory material to form an array having features sizes smaller than what would be possible using photolithography.
1. A method for manufacturing a magnetic random access memory device, the method comprising:
providing a substrate;
depositing a magnetic memory element material over the substrate:
forming a template over the magnetic memory element material, the template having an opening;
depositing a block chain copolymer material over the template a portion of the block chain copolymer being deposited into the opening in the template;
annealing the block chain copolymer to form cylindrical pillars within the openings in the template;
diffusing a metal into the pillars to form metal oxide pillars; and
using the metal oxide pillars as a mask to form magnetic memory pillars in the underlying magnetic memory element material;
wherein the diffusing a metal into the pillars comprises exposing the pillars to trimethylaluminum vapor and exposing the pillars to H 2 O vapor; and
further comprising, before forming the template, depositing a hard mask layer, and wherein process of using the metal oxide pillars as mask to form magnetic memory pillars in the underlying magnetic memory element material further comprises:
performing a reactive ion etching to transfer the image of metal oxide pillars onto the underlying hard mask; and
performing an ion milling to transfer the image of the hard mask onto the underlying magnetic memory element material.
2. The method as in claim 1 , wherein the exposure to trimethylaluminum vapor and H 2 O vapor is repeated for a plurality of cycles.
3. The method as in claim 1 , wherein the openings in the template are configured as circular openings.
4. The method as in claim 1 , wherein the openings in the template are configured as trenches.
5. The method as in claim 4 , wherein the trenches have a width that is configured to cause the block chain copolymer to form a single row of pillars in each opening.
6. The method as in claim 4 , wherein the trenches have a width that is configured to cause the block chain copolymer to form multiple rows of pillars in each opening.
7. The method as in claim 6 , wherein the pillars arrange in a hexagonal close packed lattice.
8. The method as in claim 4 , wherein the trench have a dimension that is a multiple of a period of the block copolymer.
9. The method as in claim 1 , wherein forming the template further comprises:
depositing a hard mask layer;
depositing a photoresist layer over the hard mask layer;
patterning the photoresist layer to form a photoresist mask; and
performing a reactive ion etching to transfer the pattern of the photoresist mask onto the underlying hard mask.
10. The method as in claim 1 , wherein the annealing of the block copolymer to form into ordered block copolymer pillars.
11. The method as in claim 1 , wherein the diffusing of metal into the pillars further comprises annealing in a reaction chamber in the presence of one or more of an organo-metallic gas or organo-semiconductor gas.
12. The method as in claim 1 , further comprising, before depositing a block chain copolymer material, depositing a brush layer.
13. The method as in claim 12 , wherein the brush layer is a monomolecular material.
14. The method as in claim 12 , wherein the brush layer is a mixture of styrene and methacrylate molecules with a hydroxylated end.
15. The method as in claim 1 , wherein the block chain copolymer is poly styrene-b-polymethylmethacrylate.