3D NAND high aspect ratio structure etch
Embodiments of the present disclosure provide methods for forming features in a film stack. The film stack may be utilized to form stair-like structures with accurate profiles control in manufacturing three dimensional (3D) stacking of semiconductor chips. In one example, a method includes exposing a substrate having a multi-material layer formed thereon to radicals of a remote plasma to form one or more features through the multi-material layer, the one or more features exposing a portion of a top surface of the substrate, and the multi-material layer comprising alternating layers of a first layer and a second layer, wherein the remote plasma is formed from an etching gas mixture comprising a fluorine-containing chemistry, and wherein the process chamber is maintained at a pressure of about 2 Torr to about 20 Torr and a temperature of about −100° C. to about 100° C.
1. A method for processing a substrate in a process chamber, comprising:
forming one or more features extending in a multi-material layer formed on a substrate to expose a portion of a top surface of the substrate by exposing the substrate to radicals of a remotely formed plasma, the one or more features each including top portions of sidewalls of the multi-material layer, bottom portions of the sidewalls of the multi-material layer, and the exposed portion of the top surface of the substrate, and the multi-material layer comprising alternating layers of a first dielectric layer and a second dielectric layer,
wherein the remotely formed plasma is formed from an etching gas mixture comprising a fluorine-containing chemistry, and
wherein the process chamber is maintained at a pressure of about 2 Torr to about 20 Torr and a temperature of about −100° C. to about 100° C.;
subsequent to the forming of the one or more features, selectively oxidizing the top portions of the sidewalls of the multi-material layer and not oxidizing the bottom portions of the sidewalls of the multi-material layer, wherein a ratio of the height of the oxidized top portions to a depth of the one or more features is about 1:2 to about 1:8; and
subjecting the multi-material layer to an etch process.
2. The method of claim 1 , wherein the first dielectric layer is formed of a first conductive material and the second dielectric layer is formed of a second conductive material chemically different from the first conductive material.
3. The method of claim 2 , wherein the first conductive material and the second conductive material comprise n-type or p-type doped silicon, tungsten (W), tungsten silicide (WSi), tungsten polysilicon (W/poly), tungsten alloy, tantalum (Ta), titanium (Ti), copper (Cu), ruthenium (Ru), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), manganese (Mn), aluminum (Al), hafnium (Hf), vanadium (V), molybdenum (Mo), palladium (Pd), gold (Au), silver (Au), platinum (Pt), alloys thereof, or nitride compound thereof.
4. The method of claim 3 , wherein the first conductive material is W and the second conductive material is TiN or TaN.
5. The method of claim 1 , wherein the first dielectric layer is formed of a first dielectric material and the second dielectric layer is formed of a second dielectric material chemically different from the first dielectric material.
6. The method of claim 5 , wherein the first dielectric layer and the second dielectric layer comprise silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, or composite of oxide and nitride.
7. The method of claim 5 , wherein the first dielectric layer and/or the second dielectric layer comprise hafnium dioxide (HfO 2 ), zirconium dioxide (ZrO 2 ), hafnium silicon oxide (HfSiO 2 ), hafnium aluminum oxide (HfAlO), zirconium silicon oxide (ZrSiO 2 ), tantalum dioxide (TaO 2 ), aluminum oxide, aluminum doped hafnium dioxide, bismuth strontium titanium (BST), or platinum zirconium titanium (PZT).
8. The method of claim 1 , wherein the fluorine-containing chemistry in the etching gas mixture includes NF 3 , XeF 2 , ClF, ClF 3 , ClF 5 , or F 2 .
9. The method of claim 1 , wherein the etching gas mixture further comprises a halogen containing gas.
10. The method of claim 1 , further comprising:
biasing the substrate while exposing the substrate having the multi-material layer formed thereon to radicals of a plasma.
11. A method for processing a substrate in a process chamber, comprising:
exposing a substrate having a multi-material layer formed thereon to radicals of a remote plasma to form one or more features in the multi-material layer, the one or more features exposing a portion of a top surface of the substrate, and the multi-material layer comprising alternating layers of a first dielectric layer and a second dielectric layer that is chemically different from the first dielectric layer;
exposing top portions of sidewalls of the multi-material layer to an oxygen-containing gas to selectively oxidize the top portions of the sidewalls of the multi-material layer and not to oxidize bottom portions of the sidewalls of the multi-material layer, wherein a ratio of the coverage of the oxidized top portions of the sidewalls of the multi-material layer to a depth of the feature of the one or more features is 1:2 to about 1:8; and
purging the process chamber.
12. The method of claim 11 , wherein the remote plasma is formed from NF 3 , XeF 2 , ClF, ClF 3 , ClF 5 , or F 2 .
13. The method of claim 11 , wherein the first dielectric layer is formed from tungsten (W), and the second dielectric layer is formed from titanium nitride (TiN) or tantalum nitride (TaN).