Method for forming ferrocapacitors and FeRAM devices
View Patent ↗Ferrocapacitors having a vertical structure are formed by a process in which a ferroelectric layer is deposited over an insulator. In a first etching stage, the ferroelectric material is etched to form openings in it, leaving the insulating layer substantially intact. Then a conductive layer is deposited into the openings formed in the ferroelectric layer, forming electrodes on the sides of the openings. Further etching is performed to form gaps in the Al 2 O 3 layer, for making connections to conductive elements beneath it. Thus, by the time the second etching step is performed; there are already electrodes overlying the sides of the ferroelectric material, without insulating fences in between.
1. A method for forming a vertical ferrocapacitor comprising:
depositing a ferroelectric material on an insulating layer;
a first etching step of etching of the ferroelectric material to form openings in the ferroelectric material;
depositing an electrode layer on the openings in the ferroelectric material;
a second etching step, after depositing the electrode layer, of etching to form gaps in the electrode layer and the insulating layer at the bottom of the openings; and
inserting conductive material into the gaps at least on a portion of the electrode layer.
2. A method according to claim 1 in which the first etching step leaves a film of ferroelectric material remaining at the bottom of the openings, and the film of ferroelectric material is removed during the second etching step.
3. A method according to claim 1 further comprising planarizing to form a flat upper surface on the ferroelectric material and depositing an insulating layer over it, after inserting the conductive material.
4. A method according to claim 3 in which the conductive material substantially fills the openings at least up to the planarization level.
5. A method according to claim 1 wherein the electrode layer has a thickness in the range of 15 nm to 20 nm.
6. A method according to claim 1 wherein the insulating layer is Al 2 O 3 .
7. A method according to claim 1 wherein the ferroelectric material is PZT.
8. A method according to claim 1 wherein the electrode layer contains iridium.
9. A method according to claim 1 wherein the conductive material contains iridium.
10. A method for forming a ferrocapacitor includes the steps of:
depositing a ferroelectric material over an insulating layer;
a first etching step of etching of the ferroelectric material to form openings in the ferroelectric material, but leaving a film of ferroelectric material remaining at the bottom of the openings;
depositing an electrode layer into the openings formed in the ferroelectric material;
a second etching step, after depositing the electrode layer, of etching the film of the ferroelectric material and the insulating layer at the bottom of the openings to form gaps; and
inserting conductive material into the gaps.
11. A method for forming a vertical ferrocapacitor comprising:
depositing a ferroelectric material over an insulating layer;
a first etching step of etching of the ferroelectric material to form openings in the ferroelectric material;
depositing an electrode layer into the openings formed in the ferroelectric material;
a second etching step, after depositing the electrode layer, of etching to form gaps in the electrode layer and the insulating layer at the bottom of the openings;
inserting conductive material into the gaps; and
planarizing to form a flat upper surface on the ferroelectric material and depositing an insulating layer over the upper surface, after inserting the conductive material.
12. A method according to claim 11 in which the conductive material substantially fills the openings at least up to the planarization level.
13. A method for forming a vertical ferrocapacitor comprising:
depositing a ferroelectric material over an insulating layer;
a first etching step of etching of the ferroelectric material to form openings in the ferroelectric material;
depositing an electrode layer into the openings formed in the ferroelectric material, the electrode layer has a thickness in the range of 15 nm to 20 nm;
a second etching step, after depositing the electrode layer, of etching to remove the electrode layer and the insulating layer at the bottom of the openings; and
inserting conductive material into the gaps.
14. A method for forming a vertical ferrocapacitor comprising:
depositing a ferroelectric material over an insulating layer, the insulating layer is Al 2 O 3 ;
a first etching step of etching of the ferroelectric material to form openings in the ferroelectric material;
depositing an electrode layer into the openings formed in the ferroelectric material;
a second etching step, after depositing the electrode layer, of etching to create gaps in the electrode layer and the insulating layer at the bottom of the openings; and
inserting conductive material into the gaps.
15. A method for forming a vertical ferrocapacitor comprising:
depositing a ferroelectric material over an insulating layer;
a first etching step of etching of the ferroelectric material to form openings in the ferroelectric material;
depositing an electrode layer into the openings formed in the ferroelectric material, wherein the electrode layer contains iridium;
a second etching step, after depositing the electrode layer, of etching to create gaps in the electrode layer and the insulating layer at the bottom of the openings; and
inserting conductive material into the gaps.
16. A method for forming a vertical ferrocapacitor comprising:
depositing a ferroelectric material over an insulating layer;
a first etching step of etching of the ferroelectric material to form openings in the ferroelectric material;
depositing an electrode layer into the openings formed in the ferroelectric material;
a second etching step, after depositing the electrode layer, of etching to create gaps in the electrode layer and the insulating layer at the bottom of the openings; and
inserting conductive material into the gaps, wherein the conductive material contains iridium.