Low current phase-change memory device
A semiconductor structure for a phase-change memory device includes a heater element on a portion of a bottom electrode in a first dielectric material. The semiconductor structure includes a layer of phase-change material that surrounds a portion of a second dielectric material, where the layer of phase-change material forms a three-dimensional shape around the portion of the second dielectric material. A conductive liner is under a first portion of the layer of phase-change material and surrounds a portion of a bottom surface of a hardmask layer and vertical portions of the hardmask layer. A conductive material is on a portion of a top surface of the second dielectric material and abuts the vertical portions of the layer of phase-change material below the conductive liner and the hardmask layer. A top electrode is on a top surface of the conductive material.
1. A semiconductor structure for a phase-change memory device, the semiconductor structure comprising:
a heater element in a first dielectric material, wherein the heater element is on a portion of a bottom electrode;
a layer of phase-change material surrounds a portion of a second dielectric material; and
a conductive liner is on a first portion of the first dielectric material, under a first portion of the layer of phase-change material, and surrounds a portion of a bottom surface of a hardmask layer and vertical portions of the hardmask layer.
2. The semiconductor structure of claim 1 , further comprising:
a conductive material on a portion of a top surface of the second dielectric material and abuts vertical portions of the conductive liner on the vertical portions of the hardmask layer and a vertical portion of the layer of phase-change material under a portion of the conductive liner that surrounds the portion of the bottom surface of the hardmask layer, wherein the conductive material has a lower bottom surface in a center portion of the conductive material; and
a top electrode is on at least a exposed top surface of the conductive material and the conductive liner.
3. The semiconductor structure of claim 1 , wherein the layer of phase-change material surrounds the portion of the second dielectric material forms a three-dimensional shape.
4. The semiconductor structure of claim 3 , further comprises:
a first horizontal portion of the layer of phase-change material is on the heater element and on a second portion of the first dielectric material, wherein a vertical edge of the first horizontal portion of the layer of phase-change material on the second portion of the first dielectric material abuts a vertical edge of the conductive liner on the first portion of the first dielectric material;
a second horizontal portion of the layer of phase-change material is a bottom portion of the conductive liner on the first portion of the first dielectric material;
a third horizontal portion of the layer of phase-change material is under a top portion of the conductive liner, wherein the top portion of the conductive liner is under the portion of the bottom surface of the hardmask layer; and
a vertical portion of the layer of phase-change material on a vertical portion of the conductive liner residing on vertical sides of a third dielectric material.
5. The semiconductor structure of claim 1 , wherein the layer of phase-change material surrounds the portion of a second dielectric material has a uniform thickness.
6. The semiconductor structure of claim 3 , wherein the layer of phase-change material forms the three-dimensional shape around the portion of the second dielectric material provides a uniform electrical contact resistance with the conductive liner along each side of the layer of the phase change material contacting the conductive liner.
7. The semiconductor structure of claim 3 , wherein the first horizontal portion of the layer of phase-change material on the heater element and on the first portion of the first dielectric material provides a small volume of the phase-change material allowing the layer of phase-change material adjacent to the heater element to quickly attain a temperature for a phase transition of the phase-change material.
8. The semiconductor structure of claim 4 , wherein the vertical edge of the first horizontal portion of the layer of phase-change material on the second portion of the first dielectric material abuts the vertical edge of the conductive liner on the first portion of the first dielectric material provides better electrical contact resistance than the electrical contact resistance of the phase-change material that has vertical edges that have been directionally etched.
9. The semiconductor structure of claim 2 , wherein a width of a portion of the conductive material and the conductive liner that contacts a bottom surface of the top electrode is less than a width of the second dielectric material.
10. The semiconductor structure of claim 9 , wherein the width of the portion of the conductive material and the conductive liner that contacts the bottom surface of the top electrode is the same width as the width of the first horizontal portion of the layer of phase-change material on the heater element and on the first portion of the first dielectric material.
11. The semiconductor structure of claim 1 , wherein the conductive liner is composed of an electrically conductive material that does not react with the layer of phase-change material at elevated temperatures.
12. The semiconductor structure of claim 3 , wherein the first horizontal portion of the layer of phase-change material on the heater element and on the first portion of the first dielectric material with a small volume of the layer of phase-change material requires less energy from the heater element in the first dielectric material to change an atomic structure of the phase-change material.
13. A semiconductor structure for a phase-change memory device, the semiconductor structure comprising:
a heater element in a first dielectric material, wherein the heater element is on a portion of a bottom electrode;
a resistive liner on the heater element and on a first portion of the first dielectric material;
a layer of phase-change material surrounds a portion of a second dielectric material, wherein the layer of phase-change material forms a three-dimensional shape around the portion of the second dielectric material; and
a conductive liner is under a first portion of the layer of phase-change material and surrounds a portion of a bottom surface of a hardmask layer and vertical portions of the hardmask layer.
14. The semiconductor structure of claim 13 , further comprising:
a conductive material on a portion of a top surface of the second dielectric material and abuts vertical portions of the conductive liner on the vertical portions of the hardmask layer and a vertical portion of the layer of phase-change material that is under a portion of the conductive liner that surrounds the portion of the bottom surface of the hardmask layer, wherein the conductive material has a lower portion in a center portion of the conductive material; and
a top electrode is over at least exposed portion of the conductive material and the conductive liner.
15. The semiconductor structure of claim 13 , wherein the layer of phase-change material surrounds the portion of the second dielectric material, further comprises:
a first horizontal portion of the layer of phase-change material is on the resistive liner;
a second horizontal portion of the layer of phase-change material is on the conductive liner on a second portion of the first dielectric material;
a third horizontal portion of the layer of phase-change material is under a portion of the conductive liner that is under the portion of the bottom surface of the hardmask layer; and
a vertical portion of the layer of phase-change material on a vertical portion of the conductive liner residing on a vertical side of a third dielectric material.
16. The semiconductor structure of claim 15 , wherein the resistive liner is composed of a material with an electrical resistivity that is higher than the electrical resistivity of the phase-change material in a crystalline atomic structure and lower than the electrical resistivity of the phase-change material in an amorphous atomic structure.
17. A method of forming a semiconductor structure, the method comprising:
depositing a layer of a first dielectric material above a bottom electrode;
forming a heater element in the first dielectric material;
depositing a second dielectric material over the heater element and the first dielectric material;
depositing a hardmask material;
removing a portion of the hardmask material and the second dielectric material stopping on a top surface of the heater element and the first dielectric material;
performing a lateral etch of a portion of the second dielectric material to form a recess;
conformally depositing a conductive liner;
perform a directional etch removing exposed horizontal portions of the conductive liner;
conformally depositing a layer of a phase-change material over exposed portions of the hardmask, the conductive liner, the first dielectric material, and the heater element;
deposit a third dielectric material and perform a chemical-mechanical polish;
directionally etching a top portion of the third dielectric material;
isotropically etching an exposed portion of the phase-change material;
deposit a conductive material and perform the chemical-mechanical polish; and
form a top electrode.
18. The method of claim 17 , wherein conformally depositing the layer of the phase-change material, further comprises:
conformally depositing a layer of an electrically resistive material over the exposed portions of the hardmask, the conductive liner, the first dielectric material, and the heater element; and
conformally depositing the phase-change material on the layer of the resistive material.
19. The method of claim 17 , wherein the phase-change material is of one a doped phase-change material or an undoped phase-change material.
20. The method of claim 17 , wherein a thickness of the layer of the phase-change material is between five and thirty nanometers.