Method for manufacturing nonvolatile memory device

1. A method for manufacturing a nonvolatile memory device including a plurality of memory cells,

each of the plurality of memory cells including:

a base layer including a first electrode;

a magnetic tunnel junction device provided on the base layer; and

a second electrode provided on the magnetic tunnel junction device,

the magnetic tunnel junction device including:

a first magnetic layer;

a tunneling barrier layer provided on the first magnetic layer; and

a second magnetic layer provided on the tunneling barrier layer,

the method comprising etching a portion of the second magnetic layer and a portion of the first magnetic layer by irradiating gas clusters onto a portion of a surface of the second magnetic layer or a portion of a surface of the first magnetic layer while reducing voltage accelerating the gas cluster ions.

2. The method according to claim 1 , wherein the gas clusters are ionized.

3. The method according to claim 1 , wherein the gas clusters are irradiated perpendicularly to a major surface of the base layer.

4. The method according to claim 1 , wherein the gas clusters are irradiated non-perpendicularly to a major surface of the base layer.

5. The method according to claim 1 , wherein

the first magnetic layer has an easy magnetization axis in a direction substantially perpendicular to a major surface of the first magnetic layer, and a magnetization direction of the first magnetic layer is changeable, and

the second magnetic layer has an easy magnetization axis in a direction substantially perpendicular to a major surface of the second magnetic layer, and a magnetization direction of the second magnetic layer is fixed.

6. The method according to claim 2 , wherein

a kinetic energy per one of atoms or one of molecules included in the gas clusters directly prior to the irradiating of the gas clusters onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer is not more than 30 eV, and

the kinetic energy is adjusted to be not more than 30 eV after the gas clusters are formed, the gas clusters being ionized.

7. The method according to claim 1 , wherein the gas clusters are first gas clusters including a first gas or second gas clusters including a second gas having a gas type different from a gas type of the first gas, the first gas clusters and the second gas clusters are ionized, and the first gas clusters and the second gas clusters are alternately irradiated onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer.

8. The method according to claim 1 , wherein the gas clusters are irradiated onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer while changing at least one selected from a kinetic energy per one of atoms or one of molecules included in one of the gas clusters and a number of the atoms or molecules included in one of the gas clusters.

9. The method according to claim 1 , wherein the gas clusters are irradiated onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer while changing at least one selected from a kinetic energy per one of atoms or one of molecules included in one of the gas clusters and a number of the atoms or molecules included in one of the gas clusters in a multistep fashion.

10. The method according to claim 1 , wherein at least one material selected from the group consisting of tantalum, tungsten, titanium nitride, titanium silicon nitride, tantalum silicon nitride, silicon oxide, aluminum oxide, carbon, and silicon carbide is used as a mask material of the first magnetic layer and a mask material of the second magnetic layer when etching the portion of the second magnetic layer and the portion of the first magnetic layer.

11. The method according to claim 1 , wherein the gas clusters are irradiated onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer after forming an etching stop layer under the base layer.

12. The method according to claim 1 , wherein not less than 1000 and not more than 10000 atoms or molecules are included in the gas clusters.

13. The method according to claim 1 , wherein the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer is exposed to a reaction gas in the etching.

14. The method according to claim 13 , wherein the reaction gas includes at least one type of gas selected from the group consisting of a halogen-containing gas, nitric acid, phosphoric acid, sulfuric acid, hydrogen peroxide, acetic acid, formic acid, carbon dioxide, carbon monoxide, nitrogen, oxygen, ammonia, dinitrogen monoxide and methyl ether.

15. The method according to claim 1 , wherein ion beam etching or reactive ion etching is performed before the gas clusters are irradiated onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer.

16. The method according to claim 1 , wherein the gas clusters are not ionized.

17. The method according to claim 16 , wherein a kinetic energy per one of atoms or one of molecules included in one of the gas clusters directly prior to the irradiating of the gas clusters onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer is not more than 1 eV.

18. The method according to claim 16 , wherein the gas clusters include at least one type of gas selected from the group consisting of a halogen-containing gas, carbon dioxide, carbon monoxide, nitrogen, oxygen, ammonia, dinitrogen monoxide, methyl ether, nitric acid, phosphoric acid, sulfuric acid, hydrogen peroxide, acetic acid, formic acid, and a noble gas.

19. The method according to claim 1 , wherein the gas clusters include first gas clusters including a first gas or second gas clusters including a second gas having a gas type different from a gas type of the first gas, the first gas clusters and the second gas clusters are ionized, and the first gas clusters and the second gas clusters are simultaneously or alternately irradiated onto the portion of the surface of the second magnetic layer or the portion of the surface of the first magnetic layer.

20. The method according to claim 1 , wherein the gas clusters include at least one type of gas selected from the group consisting of CHF 3 , CF 4 , C 2 F 6 , C 2 HF 5 , CHClF 2 , ClF 3 , HCl, CClF 3 , CHCl 3 , CBrF 3 , and methyl ether.

21. The method according to claim 1 , wherein the gas clusters includes at least one type of gas selected from the group consisting of halocarbon, two or more kinds of halogen, acid, and ether.