Dual resistance heater for phase change memory devices
In various examples, a dual resistance heater for a phase change material region is fabricated by forming a resistive material. Prior to forming the phase change material region over the resistive material, at least an upper portion of the resistive material is exposed to an implantation or plasma that increases the resistance of an upper portion of the resistive material relative to the remainder, or bulk, of the resistive material. As a result, the portion of the resistive material proximate to the phase change material region forms a heater because of its high resistance value, but the bulk of the resistive material has a relatively lower resistance value and, thus, does not increase the voltage drop and current usage of the device. Other methods and devices are disclosed.
1. A method of fabricating a memory device, the method comprising:
forming a dielectric layer over a conductive material;
forming a first opening in the dielectric layer;
forming a dielectric spacer within the first opening in the dielectric layer, the spacer defining a second opening;
forming at least one resistive heater material within the second opening in the dielectric spacer;
wherein a top surface region of the at least one resistive heater material is recessed below the uppermost portion of the dielectric layer;
implanting ions into the recessed top surface region of the at least one resistive heater material, resulting in two regions of the resistive heater material, a top surface region and a bulk region, the top surface region having a higher resistance than the bulk region; and
forming a phase change material comprising a chalcogenide alloy, the phase change material programmable between different phase states having different resistances, the phase change material overlying and electrically coupled to the recessed top surface region of the at least one resistive heater material, the phase change material layer extending within the second opening to contact the recessed top surface region of the at least one resistive heater material, the phase change material filling the second opening to at least the height of the uppermost portion of the dielectric layer, the phase change material having a smaller lateral dimension adjacent the top surface region than at the height of the uppermost portion of the dielectric layer.
2. The method of claim 1 , wherein implanting ions into the top surface region increases the resistance value of the top surface region.
3. The method of claim 2 , wherein the implanted ions comprise silicon.
4. The method of claim 1 , wherein implanting ions into the recessed top surface region comprises exposing at least the top surface region to a plasma treatment.
5. The method of claim 4 , further comprising diffusing oxygen atoms into the top surface region through the plasma treatment.
6. The method of claim 1 , further comprising forming the top surface region of the at least one resistive heater material to have a smaller volume than the bulk region of the at least one resistive heater material.
7. The method of claim 1 , further comprising forming the first opening in the dielectric layer to be open to the conductive material; and forming the second opening in the dielectric spacer to be open to the conductive material.
8. The method of claim 1 , wherein the heater material comprises titanium nitride; and wherein the top surface region comprises titanium silicon nitride.