Dome-shaped phase change memory mushroom cell
A mushroom memory cell may be formed by depositing a second dielectric layer on top of a first dielectric layer and a heater, depositing a hard mask on top of the second dielectric layer, performing a directional reactive-ion etching to remove an exposed portion of the second dielectric layer, performing a lateral etching to remove a portion of the second dielectric layer under the hard mask, performing directional deposition of a phase change material (PCM) over the heater, depositing a covering dielectric over the PCM, performing a second directional etching to expose a top surface of the PCM, and depositing a top electrode on the surface of the PCM.
1. A method of creating a memory cell comprising:
depositing a second dielectric layer on top of a first dielectric layer and a heater;
depositing a hard mask on top of the second dielectric layer;
performing a directional reactive-ion etching to remove an exposed portion of the second dielectric layer;
performing a lateral etching to remove a portion of the second dielectric layer under the hard mask;
performing directional deposition of a phase change material (PCM) dome over the heater;
depositing a covering dielectric over and around the PCM dome;
performing a second directional etching to expose a top surface of the PCM dome; and
depositing a top electrode on the surface of the PCM dome.
2. The method of claim 1 , wherein the method further comprises:
depositing a conformal resistive liner on the heater and the exposed portion of the second dielectric layer and an exposed portion of the first dielectric layer.
3. The method of claim 1 , further comprising:
depositing a conductive metal on the PCM dome.
4. The method of claim 3 , wherein the conductive metal deposited on the PCM dome forms the top surface of the PCM dome.
5. The method of claim 1 , further comprising:
planarizing a surface of the cell to remove a portion of the covering dielectric.
6. The method of claim 1 , further comprising:
forming a bottom electrode on a substrate;
surrounding the bottom electrode with a dielectric;
depositing the first dielectric layer on the surface of the bottom electrode and the surrounding dielectric;
patterning a contact hole in the first dielectric layer; and
forming the heater connected to the bottom electrode.
7. The method of claim 6 , wherein the heater is formed by depositing metal in the hole.
8. A memory cell device comprising:
a phase change material (PCM) dome over a heater; and
a dielectric surrounding the PCM dome.
9. The memory cell of claim 8 further comprising:
a conformal resistive liner between the PCM dome and the heater.
10. The memory cell of claim 8 further comprising:
a conductive metal on the PCM dome.
11. The memory cell of claim 8 further comprising:
a substrate with a transistor;
a bottom electrode on the transistor;
a dielectric material surrounding the bottom electrode;
a first dielectric layer on the bottom electrode;
a contact hole in the first dielectric layer; and
a heater in the contact hole connected to the PCM dome.
12. A method comprising:
applying an electrical current to a bottom electrode of a memory cell;
increasing a temperature, based on the applied electrical current, of a heater electrically connected to the bottom electrode;
forming an amorphous dome in a shaped phase change material (PCM) thermally and electrically connected to the heater based on the increasing temperature of the heater; and
recording a resistance from the bottom electrode to a top electrode, where the top electrode is electrically connected to the PCM.
13. The method of claim 12 , wherein the PCM is electrically insulated by a surrounding dielectric.
14. The method of claim 12 , wherein the PCM is electrically insulated by a surrounding airgap.