MTJ manufacturing method utilizing in-situ annealing and etch back
View Patent ↗The present invention is directed to a method for manufacturing spin transfer torque magnetic random access memory (STTMRAM) devices. The method, which utilizes in-situ annealing and etch-back of the magnetic tunnel junction (MTJ) film stack, comprises the steps of depositing a barrier layer on top of a bottom magnetic layer and then depositing an interface magnetic layer on top of the barrier layer to form an MTJ film stack; annealing the MTJ film stack at a first temperature and then cool the MTJ film stack to a second temperature lower than the first temperature; etching away a top portion of the interface magnetic layer; and depositing at least one top layer on top of the etched interface magnetic layer. The method may further include the step of annealing the MTJ film stack at a third temperature between the first and second temperature after the step of depositing at least one top layer.
1. A method of manufacturing a magnetic tunnel junction (MTJ) film stack comprising the steps of:
a) first depositing a barrier layer on top of a bottom magnetic layer and then depositing an interface magnetic layer on top of the barrier layer to form an MTJ film stack;
b) after depositing the interface magnetic layer, annealing the MTJ film stack at a first temperature;
c) after annealing the MTJ film stack at the first temperature, cooling down the MTJ film stack to a second temperature that is lower than the first temperature; and
d) after cooling down the MTJ film stack to a second temperature, depositing at least one top layer on top of the interface magnetic layer.
2. The method of manufacturing according to claim 1 , further comprising the step of annealing the MTJ film stack at a third temperature that is higher than the second temperature after depositing at least one top layer on top of the interface magnetic layer.
3. The method of manufacturing according to claim 1 , wherein the step of annealing the MTJ film stack at a first temperature and the step of depositing an interface magnetic layer are carried out within a deposition system without exposing the MTJ film stack to atmospheric environment.
4. The method of manufacturing according to claim 1 , wherein the steps (a), (b), (c), and (d) are carried out without exposing the MTJ film stack to atmospheric environment.
5. The method of manufacturing according to claim 1 , wherein the barrier layer is made of magnesium oxide, aluminum oxide, titanium oxide, or zinc oxide.
6. The method of manufacturing according to claim 1 , wherein the top layer is made of a material comprising at least one element selected from the group consisting of Co, Fe, B, Pd, Pt, Ta, Ru, Tb, Cr, Mg, O, Cu, Zn, and Hf.
7. The method of manufacturing according to claim 1 , wherein the top layer is formed by interleaving two different types of materials with at least one of the two different types being magnetic.
8. The method of manufacturing according to claim 1 , wherein the top layer is non-magnetic.
9. The method of manufacturing according to claim 1 , wherein the interface magnetic layer is made of an alloy comprising cobalt, iron, and boron.
10. The method of manufacturing according to claim 1 , wherein the interface magnetic layer is made of a material comprising at least one element selected from the group consisting of Co, Fe, B, Ta, Ti, Ni, Cr, Pt, Pd, Tb, Zn, O, Cu, and Zr.
11. The method of manufacturing according to claim 1 , wherein the bottom magnetic layer and the interface magnetic layer have magnetization directions that are substantially perpendicular to layer planes thereof.
12. The method of manufacturing according to claim 1 , wherein the bottom magnetic layer and the interface magnetic layer have magnetization directions that lie within planes that are substantially parallel to layer planes thereof.
13. The method of manufacturing according to claim 1 , wherein the step of annealing the MTJ film stack at a first temperature is carried out by rapid thermal annealing (RTA).
14. The method of manufacturing according to claim 1 , wherein the step of annealing the MTJ film stack at a first temperature is carried out by a heating element disposed beneath the MTJ film stack.
15. The method of manufacturing according to claim 1 , further comprising the step of etching away a top portion of the interface magnetic layer between the step of annealing the MTJ film stack and the step of depositing at least one top layer.
16. The method of manufacturing according to claim 15 , wherein the step of etching away a top portion of the interface magnetic layer is carried out by a dry etch process that utilizes a gas chemistry comprising at least one gas selected from the group consisting of He, Ar, Kr, Xe, Co, CO 2 , NH 3 , and CH 3 OH.
17. The method of manufacturing according to claim 1 , wherein the interface magnetic layer comprises a magnetic sublayer and a non-magnetic surface sublayer formed thereon.
18. The method of manufacturing according to claim 17 , wherein the non-magnetic surface sublayer is made of a material comprising at least one element selected from the group consisting of Ta, Pd, Ru, Mg, O, Hf, Tb, Pt, Ti, Cu, and Hf.
19. The method of manufacturing according to claim 17 , further comprising the step of etching away a top portion of the non-magnetic surface sublayer between the step of annealing the MTJ film stack and the step of depositing at least one top layer.
20. The method of manufacturing according to claim 17 , further comprising the step of etching away the non-magnetic surface sublayer and a top portion of the magnetic sublayer between the step of annealing the MTJ film stack and the step of depositing at least one top layer.
21. The method of manufacturing according to claim 1 , wherein the step of annealing the MTJ film stack at a first temperature is carried out by a heating element disposed above the MTJ film stack.
22. The method of manufacturing according to claim 21 , wherein the heating element is an optical or a radiation source.
23. The method of manufacturing according to claim 21 , wherein substrate temperature of a substrate on which the MTJ film stack forms is lower than the first temperature in the step of annealing the MTJ film stack.
24. The method of manufacturing according to claim 23 , wherein the substrate temperature is maintained by a substrate holder upon which the substrate rests in the step of annealing the MTJ film stack.