Magnetic memory devices
A magnetic memory device includes a substrate, a circuit device on the substrate, a lower electrode electrically connected to the circuit device, a magnetic tunnel junction structure (MTJ structure) on the lower electrode, and an upper electrode on the MTJ structure. The MTJ structure includes a pinned layer structure including at least one crystalline ferromagnetic layer and at least one amorphous ferromagnetic layer, a free layer, and a tunnel barrier layer between the pinned layer structure and the free layer.
1. A magnetic memory device, comprising:
a substrate;
a circuit device on the substrate;
a lower electrode electrically connected to the circuit device;
a magnetic tunnel junction structure (MTJ structure) on the lower electrode, the MTJ structure including:
a pinned layer structure including at least one crystalline ferromagnetic layer and at least one amorphous ferromagnetic layer, wherein a surface roughness of the amorphous ferromagnetic layer is less than that of the crystalline ferromagnetic layer;
a free layer; and
a tunnel barrier layer between the pinned layer structure and the free layer; and
an upper electrode on the MTJ structure.
2. The magnetic memory device as claimed in claim 1 , wherein:
the crystalline ferromagnetic layer includes a ferromagnetic metal or an alloy of ferromagnetic metals, the crystalline ferromagnetic layer being substantially devoid of a non-magnetic element, and
the amorphous ferromagnetic layer includes a ferromagnetic metal alloy doped with a non-magnetic element.
3. The magnetic memory device as claimed in claim 2 , wherein the non-magnetic element included in the ferromagnetic metal alloy of the amorphous ferromagnetic layer is at least one of boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), sulfur (S), aluminum (Al), tantalum (Ta), or tungsten (W).
4. The magnetic memory device as claimed in claim 3 , wherein:
the crystalline ferromagnetic layer includes a cobalt-platinum alloy (CoPt) or an iron-platinum alloy (FePt), and
the amorphous ferromagnetic alloy includes CoPtB or FePtB.
5. The magnetic memory device as claimed in claim 1 , wherein a saturation magnetization (Ms) of the amorphous ferromagnetic layer is less than that of the crystalline ferromagnetic layer.
6. The magnetic memory device as claimed in claim 5 , wherein:
the Ms of the amorphous ferromagnetic layer is in a range from about 150 emu/cc to about 800 emu/cc, and
the Ms of the crystalline ferromagnetic layer is in a range from about 1,000 emu/cc to about 2,000 emu/cc.
7. The magnetic memory device as claimed in claim 1 , wherein the pinned layer structure further includes an anti-ferromagnetic spacer between the crystalline ferromagnetic layer and the amorphous ferromagnetic layer.
8. The magnetic memory device as claimed in claim 7 , wherein:
the crystalline ferromagnetic layer has a body-centered cubic (bcc) structure or a face-centered cubic (fcc) structure, and
the anti-ferromagnetic spacer has a hexagonal close packing (hcp) structure.
9. The magnetic memory device as claimed in claim 1 , wherein:
the pinned layer structure includes a lower pinned layer, an anti-ferromagnetic spacer and an upper pinned layer, which are sequentially stacked, and
the crystalline ferromagnetic layer is included in each of the lower pinned layer and the upper pinned layer.
10. The magnetic memory device as claimed in claim 9 , wherein the amorphous ferromagnetic layer is included in at least one of the lower pinned layer and the upper pinned layer.
11. The magnetic memory device as claimed in claim 10 , wherein:
the amorphous ferromagnetic layer is included in each of the lower pinned layer and the upper pinned layer, and
the amorphous ferromagnetic layer in the upper pinned layer contacts a top surface of the anti-ferromagnetic spacer, and the amorphous ferromagnetic layer in the lower pinned layer contacts a bottom surface of the anti-ferromagnetic spacer.
12. The magnetic memory device as claimed in claim 11 , wherein the crystalline ferromagnetic layer in the upper pinned layer contacts the free layer and the crystalline ferromagnetic layer in the lower pinned layer contacts the lower electrode.
13. A magnetic memory device, comprising:
a substrate;
a circuit device on the substrate;
a lower electrode electrically connected to the circuit device;
a magnetic tunnel junction structure (MTJ structure) on the lower electrode, the MTJ structure including:
a pinned layer structure including a plurality of pinned layers that have different saturation magnetizations (Ms) and surface roughnesses;
a free layer; and
a tunnel barrier layer between the pinned layer structure and the free layer; and
an upper electrode on the MTJ structure.
14. The magnetic memory device as claimed in claim 13 , wherein the pinned layer structure includes:
a crystalline ferromagnetic layer; and
an amorphous ferromagnetic layer having an Ms and a surface roughness less than an Ms and a surface roughness of the crystalline ferromagnetic layer.
15. The magnetic memory device as claimed in claim 14 , wherein:
the Ms of the amorphous ferromagnetic layer is in a range from about 150 emu/cc to about 800 emu/cc, and
the Ms of the crystalline ferromagnetic layer is in a range from about 1,000 emu/cc to about 2,000 emu/cc.
16. The magnetic memory device as claimed in claim 14 , wherein:
the pinned layer structure includes a lower pinned layer, an upper pinned layer and an anti-ferromagnetic spacer separating the lower pinned layer and the upper pinned layer, and
at least one of the upper pinned layer or the lower pinned layer includes a stack structure of the crystalline ferromagnetic layer and the amorphous ferromagnetic layer.
17. The magnetic memory device as claimed in claim 16 , wherein the amorphous ferromagnetic layer directly contacts the anti-ferromagnetic spacer.
18. A magnetic memory device, comprising:
a plurality of first conductive lines extending in a first direction;
a plurality of second conductive lines located over the first conductive lines, the second conductive lines extending in a second direction crossing the first direction; and
magnetic tunnel junction (MTJ) structures interposed between the first conductive lines and the second conductive lines, each MTJ structure including:
a pinned layer pattern including at least one crystalline ferromagnetic pattern and at least one amorphous ferromagnetic pattern, wherein a saturation magnetization (Ms) and a surface roughness of the amorphous ferromagnetic pattern are less than an Ms and a surface roughness of the crystalline ferromagnetic pattern;
a free layer pattern; and
a tunnel barrier pattern between the pinned layer pattern and the free layer pattern.