Three-dimensional memory device having stressed vertical semiconductor channels and method of making the same
Three-dimensional memory devices include structures that induce a vertical tensile stress in vertical semiconductor channels to enhance charge carrier mobility. Vertical tensile stress may be induced by a laterally compressive stress applied by stressor pillar structure. The stressor pillar structures can include a stressor material such as a dielectric metal oxide material, silicon nitride, thermal silicon oxide or a semiconductor material having a greater lattice constant than that of the channel. Vertical tensile stress may be induced by a compressive stress applied by electrically conductive layers that laterally surround the vertical semiconductor channel, or by a stress memorization technique that captures a compressive stress from sacrificial material layers. Vertical tensile stress can be generated by a source-level pinning layer that prevents vertical expansion of the vertical semiconductor channel. Vertical tensile stress can be induced by using a layer stack including polysilicon and a silicon-germanium alloy for the vertical semiconductor channel.
1. A three-dimensional memory device, comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate;
a memory stack structure vertically extending through the alternating stack, wherein the memory stack structure comprises a memory film that contains a vertical stack of memory elements located at levels of the electrically conductive layers, and a vertical semiconductor channel that contacts the memory film; and
a stressor pillar structure located on a side of the vertical semiconductor channel, wherein:
the stressor pillar structure applies a vertical tensile stress to the vertical semiconductor channel;
a lateral extent of the stressor pillar structure is defined by at least one substantially vertical dielectric sidewall surface that provides a closed periphery around the stressor pillar structure;
the stressor pillar structure consists essentially of a stressor material and does not include any solid or liquid material therein other than the stressor material; and
the stressor material is selected from a dielectric metal oxide material, silicon nitride deposited under stress, thermal silicon oxide, or a semiconductor material having a greater lattice constant than that of the vertical semiconductor channel.
2. The three-dimensional memory device of claim 1 , wherein the stressor material is a dielectric metal oxide material selected from tantalum oxide, aluminum oxide, hafnium oxide, aluminum silicate, or hafnium silicate.
3. The three-dimensional memory device of claim 1 , wherein:
the stressor material is a dielectric metal oxide material; and
the stressor pillar structure directly contacts a substantially vertical sidewall of the vertical semiconductor channel.
4. The three-dimensional memory device of claim 1 , wherein:
the stressor material is a dielectric metal oxide material; and
a silicon oxide liner is located between, and contacts sidewalls of, the vertical semiconductor channel and the stressor pillar structure.
5. The three-dimensional memory device of claim 1 , wherein:
the stressor material is silicon nitride deposited under compressive or tensile stress; and
the stressor pillar structure directly contacts a substantially vertical sidewall of a respective one of the vertical semiconductor channel.
6. The three-dimensional memory device of claim 1 , wherein:
the stressor material is thermal silicon oxide; and
the stressor pillar structure directly contacts a substantially vertical sidewall of a respective one of the vertical semiconductor channel.
7. The three-dimensional memory device of claim 1 , wherein:
the stressor material is thermal silicon oxide; and
a silicon nitride liner is located between, and contacts sidewalls of, the vertical semiconductor channel and the stressor pillar structure.
8. The three-dimensional memory device of claim 1 , wherein the vertical semiconductor channel comprises intrinsic polysilicon or p-type doped polysilicon having a boron doping concentration less than 1×10 17 cm −3 , and the stressor material is a semiconductor material having a greater lattice constant than the intrinsic polysilicon or the p-type doped polysilicon having the boron doping concentration less than 1×10 17 cm −3 .
9. The three-dimensional memory device of claim 1 , wherein:
the stressor pillar structure has a circular cylindrical shape or a laterally-elongated cylindrical shape;
the vertical semiconductor channel laterally surrounds the stressor pillar structure; and
the memory film laterally surrounds the vertical semiconductor channel.
10. The three-dimensional memory device of claim 1 , wherein:
the memory cell comprises a semi-cylindrical outer sidewall surface; and
the stressor pillar structure includes a pair of planar sidewalls that vertically extend through all levels of the electrically conductive layers and laterally extends with a uniform lateral separation distance therebetween.
11. The three-dimensional memory device of claim 1 , wherein:
the memory film comprises a pair of substantially vertical planar sidewall surfaces; and
the stressor pillar structure includes a pair of laterally undulating lengthwise sidewalls that vertically extend through all levels of the electrically conductive layers and laterally spaced apart with an undulating lateral separation distance.