Method for producing crystallographically textured electrodes for textured PZT capacitors
View Patent ↗A bottom electrode structure and manufacturing method is described for producing crystallographically textured iridium electrodes for making textured PZT capacitors that enables enhanced ferroelectric memory performance. The use of seed layers originating from hexagonal crystal structures with {0001} texture provides a smooth surface for growth of {111} textured iridium, which exhibits the face-centered cubic (“FCC”) structure. This seeding technique results in {111} textured iridium with a small surface roughness relative to the film thickness. The highly textured iridium supports {111} textured PZT dielectric layer growth. Textured PZT exhibits enhanced switched polarization, reduced operating voltage and also improves the reliability of PZT capacitors used in FRAM® memory and other microelectronic devices.
1. A bottom electrode structure for a ferroelectric capacitor comprising:
a seed layer; and
a bottom electrode layer, wherein the non-zero lattice mismatch between the bottom electrode layer and the seed layer is within ±25%.
2. The bottom electrode structure of claim 1 in which the seed layer comprises a hexagonal close-packed seed layer.
3. The bottom electrode structure of claim 1 in which the seed layer comprises a wurtzite crystal structure seed layer.
4. The bottom electrode structure of claim 1 in which the seed layer comprises a tetragonal crystal structure seed layer.
5. The bottom electrode structure of claim 1 in which the bottom electrode layer comprises an iridium layer.
6. The bottom electrode structure of claim 1 in which the bottom electrode layer comprises a layer of material selected from the group consisting of Pt, Pd, Ag, An, Cu, and Ni.
7. The bottom electrode structure of claim 1 in which the seed layer comprises a layer about 5 to 40 nm thick.
8. The bottom electrode structure of claim 1 in which the bottom electrode layer comprises a layer about 50 to 100 nm thick.
9. The bottom electrode structure of claim 1 in which the seed layer comprises a layer having a 002 rocking-curve FWHM of less than five degrees for hexagonal close-packed and wurtzite crystal structure seed layers.
10. The bottom electrode structure of claim 1 in which the seed layer comprises a layer having a 200 rocking-curve FWHM of less than five degrees for tetragonal crystal structure seed layers.
11. The bottom electrode structure of claim 1 in which the bottom electrode layer comprises a layer having a {111} rocking-curve FWHM of less than five degrees.
12. The bottom electrode structure of claim 1 in which the iridium bottom electrode layer comprises a layer having a {111} crystallographic texture.
13. The bottom electrode structure of claim 1 in which the seed layer comprises a titanium or titanium dioxide layer.
14. The bottom electrode structure of claim 1 in which the seed layer comprises a ruthenium or ruthenium dioxide layer.
15. The bottom electrode structure of claim 1 in which the seed layer comprises a cobalt or zirconium layer.
16. The bottom electrode structure of claim 1 in which the seed layer comprises a layer of material selected from the group consisting of BN, AlN, GaN, InN, and ZnO.
17. The bottom electrode structure of claim 1 in which the seed layer comprises:
a first layer of titanium or titanium dioxide; and
a second layer of platinum.
18. The bottom electrode structure of claim 1 in which the seed layer comprises:
a first layer having a wurtzite crystal structure; and
a second layer of platinum.