Bottom-type perpendicular magnetic tunnel junction (pMTJ) element with thermally stable amorphous blocking layers
View Patent ↗The invention provides a bottom-type perpendicular magnetic tunnel junction (pMTJ) element with thermally stable amorphous blocking layers for high-density nonvolatile data storage. The first blocking layer, preferably formed of an amorphous nonmagnetic film, blocks a polycrystalline diffusion barrier layer with a body-center-cubic (bcc) <110> texture in order for the keeper and lower reference layers of the bottom-type pMTJ element to freely grow with a face-centered-cubic (fcc) <111> texture, thereby developing strong perpendicular magnetic anisotropy (PMA). The second blocking layer, preferably formed of an amorphous ferromagnetic film, blocks the keeper and lower reference layers of the bottom-type pMTJ element in order for the upper reference, barrier and storage layers of the bottom-type pMTJ element to freely grow with a <001> texture, thereby exhibiting a strong tunneling magnetoresistance (TMR) effect.
1. A bottom-type perpendicular magnetic tunnel junction (pMTJ) element comprising:
a barrier layer sandwiched between a lower stack and an upper stack;
the lower stack comprising:
a first blocking layer;
a seed layer on the first blocking layer;
a keeper layer on the seed layer;
a spacer layer on the keeper layer;
a lower reference layer on the spacer layer;
a second blocking layer on the lower reference layer; and
an upper reference layer on the second blocking layer;
the upper stack comprising:
a storage layer on the barrier layer;
a lower cap layer on the storage layer; and
an upper cap layer on the lower cap layer.
2. The bottom-type pMTJ element as in claim 1 , wherein the first blocking layer is amorphous and has a thickness ranging from 0.8 to 80 nm.
3. The bottom-type pMTJ element as in claim 1 , wherein the first blocking layer contains at least two chemical elements, the first being selected from one of a first group including Ni, Co, Fe, Cr and Ti with a content ranging 70 to 94 at %, and the second being selected from one of a second group including Nb, Zr, Hf and Y with a content ranging from 6 to 30 at %.
4. The bottom-type pMTJ element as in claim 1 , wherein the second blocking layer is amorphous ferromagnetic and has a thickness ranging from 0.4 to 20 nm.
5. The bottom-type pMTJ element as in claim 1 , wherein the second blocking layer contains at least three chemical elements, the first being selected from one of a first group including Ni, Co, Fe, Cr and Ti with a content ranging 42 to 84 at %, the second being selected from one of a second group including Nb, Zr, Hf and Y with a content ranging from 8 to 24 at %, and the third being selected from one of a third group including O, N, C and B with a content ranging from 8 to 24 at %.
6. A spin transfer torque magnetic random access memory (STT-MRAM) cell including
a complementary metal-oxide-semiconductor (CMOS) transistor;
a first interconnect;
a bottom-type perpendicular magnetic tunnel junction (pMTJ) element comprising
a barrier layer sandwiched between a lower stack and an upper stack;
the lower stack comprising:
a first blocking layer;
a seed layer on the first blocking layer;
a keeper layer on the seed layer;
a spacer layer on the keeper layer;
a lower reference layer on the spacer layer;
a second blocking layer on the lower reference layer; and
an upper reference layer on the second blocking layer;
the upper stack comprising:
a storage layer on the barrier layer;
a lower cap layer on the storage layer; and
an upper cap layer on the lower cap layer;
a second interconnect; and
an insulator.
7. The STT-MRAM cell as in claim 6 , wherein the first blocking layer is amorphous and has a thickness ranging from 0.8 to 80 nm.
8. The STT-MRAM cell as in claim 6 , wherein the first blocking layer contains at least two chemical elements, the first being selected from one of a first group including Ni, Co, Fe, Cr and Ti with a content ranging 70 to 94 at %, and the second being selected from one of a second group including Nb, Zr, Hf and Y with a content ranging from 6 to 30 at %.
9. The STT-MRAM cell as in claim 6 , wherein the second blocking layer is amorphous ferromagnetic and has a thickness ranging from 0.4 to 20 nm.
10. The STT-MRAM cell as in claim 6 , wherein the second blocking layer contains at least three chemical elements, the first being selected from one of a first group including Ni, Co, Fe, Cr and Ti with a content ranging 42 to 84 at %, the second being selected from one of a second group including Nb, Zr, Hf and Y with a content ranging from 8 to 24 at %, and the third being selected from one of a third group including O, N, C and B with a content ranging from 8 to 24 at %.