Ferroelectric memory and manufacturing method thereof
View Patent ↗Provided is a ferroelectric memory including a silicon substrate, a transistor formed on the silicon substrate, and a ferroelectric capacitor formed above the transistor. The ferroelectric capacitor includes a lower electrode, a ferroelectric film formed on the lower electrode, an upper electrode formed on the ferroelectric film, and a metal film formed on the upper electrode.
1. A ferroelectric memory comprising:
a semiconductor substrate;
a transistor formed on the semiconductor substrate; and
a ferroelectric capacitor formed over the transistor, wherein the ferroelectric capacitor includes:
a lower electrode;
a ferroelectric film formed over the lower electrode;
an upper electrode formed over the ferroelectric film;
a metal film formed over the upper electrode;
an insulating film covering the ferroelectric capacitor;
a hole formed through the insulating film and the metal film; and
a conductive plug formed in the hole and being contact to the upper electrode.
2. The ferroelectric memory according to claim 1 , wherein the upper electrode has a laminated structure of a first oxide film and a second oxide film.
3. The ferroelectric memory according to claim 2 , wherein each of the first oxide film and the second oxide film is an iridium oxide film.
4. The ferroelectric memory according to claim 1 , wherein the metal film contains titanium.
5. The ferroelectric memory according to claim 1 , wherein the metal film is made of noble metal.
6. The ferroelectric memory according to claim 5 , further comprising:
an insulating film covering the ferroelectric capacitor and including a hole over the metal film; and
a conductive plug formed in the hole and electrically connected to the upper electrode, wherein
a concave portion is formed in the metal film below the hole.
7. The ferroelectric memory according to claim 1 , wherein the metal film has a film thickness in a range from 20 nm to 30 nm.
8. A method of manufacturing a ferroelectric memory, comprising:
forming a transistor on a semiconductor substrate;
forming a lower electrode film over the transistor;
forming a ferroelectric film over the lower electrode film;
forming a first upper electrode film over the ferroelectric film;
forming a second upper electrode film over the first upper electrode film; and
forming a metal film over the second upper electrode film;
forming an insulating film covering the ferroelectric capacitor;
forming a hole through the insulating film and the metal film; and
forming a conductive plug in the hole, the conductive plug being contact to the upper electrode.
9. The method of manufacturing a ferroelectric memory according to claim 8 , further comprising:
forming the hole through in the metal film by wet etching after forming the hole through the insulating film.
10. The method of manufacturing a ferroelectric memory according to claim 9 , wherein the wet etching uses an etchant with which the metal film is etched at a faster etching rate than the first upper electrode film and the second upper electrode film are etched.
11. The method of manufacturing a ferroelectric memory according to claim 10 , wherein
oxide iridium films are formed as the first upper electrode film and the second upper electrode film,
a film containing titanium is formed as the metal film, and
an ammonium hydrogen peroxide mixture is used as the etchant.
12. The method of manufacturing a ferroelectric memory according to claim 8 , wherein a noble metal film is formed as the metal film.