Memory device with manufacturable cylindrical storage node
View Patent ↗A high capacitance embedded capacitor and associated fabrication processes are disclosed for fabricating a capacitor stack in a multi-layer stack to include a first capacitor plate conductor formed with a cylinder-shaped storage node electrode formed in the multi-layer stack, a capacitor dielectric layer surrounding the cylinder-shaped storage node electrode, and a second capacitor plate conductor formed from a conductive layer in the multi-layer stack that is sandwiched between a bottom and top dielectric layer, where the cylinder-shaped storage node electrode is surrounded by and extends through the conductive layer.
1. A method for fabricating a DRAM device, the method comprising:
forming a transistor having a source/drain region in a semiconductor substrate;
forming a vertical conductive structure directly on the source/drain region;
forming a first layered structure on the vertical conductive structure, the first layered structure comprising at least a first dielectric layer;
forming a first hole in the first layered structure such that an upper surface portion of the vertical conductive structure is exposed;
forming a first capacitor dielectric layer within the first hole, the first capacitor dielectric layer partially filling the first hole;
forming a first conductive layer within the first hole and over the first capacitor dielectric layer, the first conductive layer partially filling the first hole;
etching the first conductive layer and the first capacitor dielectric layer using an anisotropic etch process such that a sidewall portion of the first conductive layer along the height of the first hole and a sidewall portion of the first capacitor dielectric layer along the height of the first hole remain and a bottom portion of the first conductive layer and a bottom portion of the first capacitor dielectric layer within the first hole are at least partially removed such that the upper surface portion of the vertical conductive structure is partially exposed;
forming a second conductive layer within the first hole and on the first conductive layer such that the second conductive layer is in direct contact with the first conductive layer and the vertical conductive structure, and such that the second conductive layer has an upper surface;
forming an upper capacitor structure on the second conductive layer, such that an electrode is formed in direct contact with the upper surface of the second conductive layer.
2. The method of claim 1 , wherein forming the upper capacitor structure comprises:
forming a sacrificial dielectric layer above the second conductive layer and subsequently forming a second hole in the sacrificial dielectric layer such that the second hole is at least partially aligned with the second conductive layer;
forming a bottom conductive electrode layer over the sacrificial dielectric layer and inside the second hole;
removing portions of the bottom conductive electrode layer above the sacrificial dielectric layer, leaving portions of the bottom conductive electrode layer at least within the second hole;
removing the sacrificial dielectric layer;
forming a second capacitor dielectric layer over the bottom conductive electrode layer; and
forming a common plate electrode over the second capacitor dielectric layer.
3. The method of claim 1 , wherein forming the vertical conductive structure comprises:
forming a contact plug on the source/drain region; and
forming a contact pad on the contact plug,
wherein the first capacitor dielectric layer is formed in direct contact with the contact pad;
and wherein etching the first conductive layer comprises exposing the contact pad.
4. The method of claim 1 , wherein forming the first layered structure comprises:
forming a bottom dielectric layer;
forming a middle conductive layer above the bottom dielectric layer; and
forming a top dielectric layer above the middle conductive layer.
5. The method of claim 1 , wherein etching the first capacitor dielectric layer leaves a horizontal portion of the first capacitor dielectric layer unremoved on the surface of the vertical conductive structure.
6. The method of claim 1 , wherein the first conductive layer comprises poly-silicon.
7. The method of claim 1 , wherein the first conductive layer comprises at least one of TiN and TaN.
8. The method of claim 1 , wherein the electrode of the upper capacitor structure is crown-shaped.