Method for manufacturing high density magnetic random access memory devices using diamond like carbon hard mask
A method for manufacturing magnetic random access memory. The method allows very high density magnetic memory elements to be formed on a magnetic memory chip. A magnetic memory element material is deposited and a diamond like carbon (DLC) hard mask is formed over the magnetic memory element material. An ion or atom bombardment process such as ion milling is performed to remove portions of the magnetic memory element material that are not protected by the hard mask to form a plurality of magnetic memory element pillars. Because the diamond like carbon hard mask is resistant to the material removal processes such as ion milling, it can be made very thin (10-20 nm), which reduces shadowing while still allowing a process such as ion milling to be used to define the magnetic data element pillars. This advantageously allows the pillars to be formed with well defined, vertical sidewalls, and avoiding shorting.
1. A method for manufacturing magnetic random access memory, the method comprising:
providing a substrate;
depositing a magnetic memory element material over the substrate;
depositing a layer of diamond like carbon over the magnetic memory element material;
patterning the diamond like carbon to form a diamond like carbon hard mask that is configured to define a plurality of pillars; and
performing a material removal process to remove portions of the magnetic memory element material that are not protected by the diamond like carbon hard mask to form pillars of magnetic memory element material, wherein the material removal process is an ion or atom bombardment process.
2. The method as in claim 1 , wherein the material removal process comprises ion milling.
3. The method as in claim 1 , wherein the magnetic memory element material includes a plurality of material layers configured to form a magnetic tunnel junction element.
4. The method as in claim 1 , wherein the magnetic memory element material includes first and second magnetic layers and a thin layer of non-magnetic, electrically insulating material located between the first and second magnetic layers.
5. The method as in claim 1 , wherein the patterning of the diamond like carbon layer further comprises:
depositing a layer of photoresist;
patterning the layer of photoresist; and
performing a reactive ion etching to remove portions of the diamond like carbon layer that are not protected by the patterned layer of photoresist.
6. The method as in claim 5 , wherein the patterning of the photoresist layer further comprises photolithographically patterning the layer of photoresist.
7. The method as in claim 5 , wherein the patterning of the photoresist layer further comprises electron beam exposure.
8. The method as in claim 1 , wherein the layer of diamond like carbon has a thickness of 10-20 nm.
9. The method as in claim 1 , wherein the layer of diamond like carbon is deposited by sputter deposition.
10. The method as in claim 1 , wherein the layer of diamond like carbon is deposited by plasma vapor deposition.
11. The method as in claim 1 , wherein the layer of diamond like carbon is deposited by filtered cathodic arc deposition.
12. The method as in claim 1 , further comprising, after performing the material removal process, depositing a thin, electrically insulating layer, the thin, electrically insulating layer being deposited in-situ.
13. The method as in claim 12 , further comprising, after depositing the thin layer of electrically insulating material, depositing an insulating fill layer, performing a chemical mechanical polishing process and removing the remaining diamond like carbon hard mask by reactive ion etching in an atmosphere that contains one or more of CO 2 and O 2 .
14. The method as in claim 1 , wherein the material removal process is performed in a chamber under a vacuum, and further comprising after performing the material removal process, depositing a thin, electrically insulating layer by a conformal deposition process in the chamber without breaking the vacuum.
15. A method for manufacturing magnetic random access data memory, the method comprising:
depositing a first magnetic layer;
depositing a thin, non-magnetic, electrically insulating barrier layer over the first magnetic layer;
depositing a second magnetic layer over the thin, non-magnetic, electrically insulating layer;
depositing a layer of diamond like carbon;
patterning the layer of diamond like carbon to form a hard mask;
performing a first material removal process to remove portions of the second magnetic layer that are not protected by the hard mask, the first material removal process being terminated before all of the first magnetic layer;
after performing the first material removal process, depositing a thin electrically insulating layer by a conformal deposition process; and
after depositing the thin electrically insulating layer, performing a second material removal process to remove portions of the first magnetic layer that are not protected by the second magnetic layer;
wherein the first and second material removal processes comprise an ion or atom bombardment process.
16. The method as in claim 15 , further comprising, after performing the second material removal process, depositing a non-magnetic, electrically insulating fill material.
17. The method as in claim 15 , wherein the first and second material removal processes comprise ion milling.
18. The method as in claim 15 , wherein the layer of diamond like carbon is deposited to a thickness of 10-20 nm.