Ferroelectric device
Example embodiments relate to ferroelectric devices. An example ferroelectric device layer structure includes a first electrode. The ferroelectric device layer structure also includes a second electrode. Additionally, the ferroelectric device layer structure includes a ferroelectric layer of hafnium zirconate (HZO). Further, the ferroelectric device layer structure includes an oxide layer of Nb 2 O 5 or Ta 2 O 5 arranged on the ferroelectric layer. The ferroelectric layer and the oxide layer are arranged between the first electrode and the second electrode.
1. A ferroelectric device layer structure comprising:
a first electrode;
a second electrode;
a ferroelectric layer of hafnium zirconate (HZO); and
an oxide layer of Nb 2 O 5 or Ta 2 O 5 arranged on the ferroelectric layer,
wherein the ferroelectric layer and the oxide layer are arranged between the first electrode and the second electrode, and
wherein the ferroelectric layer and the oxide layer have an orthorhombic crystal structure:
producible by an annealing step performed at an annealing temperature in a range of 350° C.-750° C. if the oxide layer is made of Nb 2 O 5 ; and
producible by an annealing step performed at corresponding to an annealing temperature in a range of 350° C.-900° C. if the oxide layer is made of Ta 2 O 5 .
2. The ferroelectric device layer structure according to claim 1 , wherein at least 30% of the ferroelectric layer and the oxide layer have the orthorhombic crystal structure.
3. The ferroelectric device layer structure according to claim 1 , further comprising an interfacial layer between the oxide layer and the second electrode.
4. The ferroelectric device layer structure according to claim 1 , wherein the ferroelectric layer is a doped HZO layer.
5. The ferroelectric device layer structure according to claim 1 , wherein the oxide layer is between 0.5 nm and 3 nm thick.
6. A ferroelectric device comprising:
the ferroelectric device layer structure according to claim 1 ; and
a doped semiconductor substrate having a front side and a back side, wherein the ferroelectric device layer structure is arranged on the front side.
7. A method for fabricating a ferroelectric device, wherein the method comprises:
forming a ferroelectric device layer structure comprising:
a first electrode;
a second electrode;
a ferroelectric layer of hafnium zirconate (HZO); and
an oxide layer of Nb 2 O 5 or Ta 2 O 5 arranged on the ferroelectric layer,
wherein the ferroelectric layer and the oxide layer are arranged between the first electrode and the second electrode; and
annealing the layers of the ferroelectric device layer structure at a temperature in a range of 350° C.-750° C. if the oxide layer is made of Nb 2 O 5 and in a range of 350° C.-900° C. if the oxide layer is made of Ta 2 O 5 .
8. The method according to claim 7 , further comprising:
depositing additional metal on the second electrode after the annealing step; and
patterning the metal to form the second electrode.
9. The method according to claim 7 , wherein forming a ferroelectric device layer structure comprises:
depositing a metal for forming the first electrode on a front side of a semiconductor substrate;
depositing HZO for forming the ferroelectric layer on the first electrode;
depositing Nb 2 O 5 or Ta 2 O 5 for forming the oxide layer on the ferroelectric layer; and
depositing a metal for forming the second electrode.
10. The method according to claim 9 , further comprising forming an aluminum layer on a back side of the semiconductor substrate.
11. The method according to claim 9 , wherein the depositing steps use atomic layer deposition (ALD).
12. The method according to claim 11 , wherein the ALD is performed with a reactor temperature in a range of 150° C.-450° C.
13. The method according to claim 11 , wherein the ALD comprises plasma-enhanced ALD or thermal ALD.
14. A ferroelectric device formed according to a method comprising:
forming a ferroelectric device layer structure comprising:
a first electrode;
a second electrode;
a ferroelectric layer of hafnium zirconate (HZO); and
an oxide layer of Nb 2 O 5 or Ta 2 O 5 arranged on the ferroelectric layer,
wherein the ferroelectric layer and the oxide layer are arranged between the first electrode and the second electrode; and
annealing the layers of the ferroelectric device layer structure at a temperature in a range of 350° C.-750° C. if the oxide layer is made of Nb 2 O 5 and in a range of 350° C.-900° C. if the oxide layer is made of Ta 2 O 5 .
15. The ferroelectric device according to claim 14 , further comprising:
depositing additional metal on the second electrode after the annealing step; and
patterning the metal to form the second electrode.
16. The ferroelectric device according to claim 14 , wherein forming a ferroelectric device layer structure comprises:
depositing a metal for forming the first electrode on a front side of a semiconductor substrate;
depositing HZO for forming the ferroelectric layer on the first electrode;
depositing Nb 2 O 5 or Ta 2 O 5 for forming the oxide layer on the ferroelectric layer; and
depositing a metal for forming the second electrode.
17. The ferroelectric device according to claim 16 , further comprising forming an aluminum layer on a back side of the semiconductor substrate.
18. The ferroelectric device according to claim 16 , wherein the depositing steps use atomic layer deposition (ALD).
19. The ferroelectric device according to claim 18 , wherein the ALD is performed with a reactor temperature in a range of 150° C.-450° C.
20. The ferroelectric device according to claim 18 , wherein the ALD comprises plasma-enhanced ALD or thermal ALD.