Method of making high aspect ratio openings in a semiconductor device using ion implanted regrown cladding mask
A method of patterning a structure includes forming an alternating stack of first material layers and second material layers over a substrate, forming an etch mask material layer over the alternating stack, forming openings in an upper portion of the alternating stack by performing a first anisotropic etch process that transfers a pattern in the etch mask material layer through a first subset of layers within the alternating stack, anisotropically depositing a cladding material on the etch mask material layer to form a cladding material layer, ion implanting dopant atoms into the cladding material layer, and vertically extending the openings downward in the alternating stack by performing a second anisotropic etch process. The dopant atoms decrease an etch rate of the cladding material layer during the second anisotropic etch process.
1 . A method of patterning a structure, comprising:
forming an alternating stack of first material layers and second material layers over a substrate;
forming an etch mask material layer over the alternating stack;
forming openings in an upper portion of the alternating stack by performing a first anisotropic etch process that transfers a pattern in the etch mask material layer through a first subset of layers within the alternating stack;
anisotropically depositing a cladding material on the etch mask material layer to form a cladding material layer;
ion implanting dopant atoms into the cladding material layer; and
vertically extending the openings downward in the alternating stack by performing a second anisotropic etch process, wherein the dopant atoms decrease an etch rate of the cladding material layer during the second anisotropic etch process.
2 . The method of claim 1 , wherein the dopants atoms comprise carbon atoms.
3 . The method of claim 1 , wherein the dopants atoms comprise Si, Ge, N, P or As atoms.
4 . The method of claim 1 , wherein the dopant atoms comprise Ne, Ar or Kr atoms.
5 . The method of claim 1 , wherein the dopant atoms comprise metal atoms.
6 . The method of claim 1 , wherein the step of ion implanting the dopant atoms comprises a tilted ion implantation process.
7 . The method of claim 6 , further comprising rotating the substrate during the tilted ion implantation process.
8 . The method of claim 6 , wherein the tilted ion implantation process comprises multiple tilted ion implantation steps in which a respective ion beam direction is tilted relative to a vertical direction by a same tilt angle along different azimuthal tilt directions.
9 . The method of claim 6 , wherein an ion beam direction is tilted relative to a vertical direction perpendicular to a top surface of the substrate by a tilt angle is greater than an arctangent of a ratio of a maximum lateral dimension of openings after formation of the cladding material layer to 0.9 times a maximum height of a combination of the etch mask material layer and the cladding material layer as measured above a horizontal plane including a topmost surface of the alternating stack.
10 . The method of claim 9 , wherein the tilt angle is in a range from 10 degrees to 45 degrees.
11 . The method of claim 1 , wherein the cladding material is anisotropically deposited by an non-conformal physical vapor deposition process.
12 . The method of claim 1 , wherein the cladding material is anisotropically deposited by a chemical vapor deposition or atomic layer deposition process.
13 . The method of claim 1 , wherein the cladding material layer comprises carbon.
14 . The method of claim 13 , wherein the etch mask material layer comprises a carbon-based material comprising carbon atoms at an atomic concentration greater than 50%.
15 . The method of claim 1 , wherein sidewalls of the etch mask material layer have a first taper angle relative to a vertical direction perpendicular to a top surface of the substrate after performing the first anisotropic etch process.
16 . The method of claim 15 , further comprising performing a profile-shaping process that increases a tilt angle of the sidewalls of the etch mask material layer to a second taper angle that is greater than the first taper angle prior to the step of anisotropically depositing the cladding material layer.
17 . The method of claim 16 , wherein a difference between the second taper angle and the first taper angle is in a range from 0.1 degree to 6 degrees.
18 . The method of claim 1 , wherein:
the first material layers comprise silicon oxide layers; and
the second material layers comprise silicon nitride layers.
19 . The method of claim 1 , wherein the openings are vertically extended to a top surface of the substrate during the second anisotropic etch process or during a subsequent anisotropic etch process that is performed after the second anisotropic etch process.
20 . The method of claim 1 , further comprising:
removing remaining portions of the etch mask material layer and the cladding material layer; and
forming memory opening fill structures in the openings, wherein each of the memory opening fill structures comprises a respective memory film, a respective vertical semiconductor channel, a respective dielectric core, and a respective drain region.