Method of making a three-dimensional memory device using composite hard masks for formation of deep via openings

A method of forming a semiconductor structure, comprising:

• forming an alternating stack of first material layers and second material layers over a substrate;
• forming a hard mask layer over the alternating stack;
• applying and patterning a photoresist layer over the hard mask layer, wherein openings are formed in the photoresist layer;
• forming cavities in the hard mask layer by performing a first anisotropic etch process that transfers a pattern of the openings in the photoresist layer through the hard mask layer;
• forming via openings through an upper portion of the alternating stack by performing a second anisotropic etch process that transfers a pattern of the cavities in the hard mask layer;
• forming a cladding liner on sidewalls of the cavities in the hard mask layer;
• and
• vertically extending the via openings through all layers within the alternating stack by performing a third anisotropic etch process that employs a combination of the cladding liner and the hard mask layer as an etch mask;
• wherein the cladding liner is deposited by a non-conformal deposition process that deposits a material of the cladding liner anisotropically with a variable thickness that decreases with a vertical distance from a horizontal plane including a top surface of the hard mask layer.

A method of forming a semiconductor structure, comprising:

• forming an alternating stack of first material layers and second material layers over a substrate;
• forming a hard mask layer over the alternating stack;
• applying and patterning a photoresist layer over the hard mask layer, wherein openings are formed in the photoresist layer;
• forming cavities in the hard mask layer by performing a first anisotropic etch process that transfers a pattern of the openings in the photoresist layer through the hard mask layer;
• forming via openings through an upper portion of the alternating stack by performing a second anisotropic etch process that transfers a pattern of the cavities in the hard mask layer;
• forming a cladding liner on sidewalls of the cavities in the hard mask layer;
• and
• vertically extending the via openings through all layers within the alternating stack by performing a third anisotropic etch process that employs a combination of the cladding liner and the hard mask layer as an etch mask;
• wherein the cladding liner comprises a metallic material selected from TiN, Ru, Co, Mo or W.

A method of forming a semiconductor structure, comprising:

• forming an alternating stack of first material layers and second material layers over a substrate;
• forming a hard mask layer over the alternating stack;
• applying and patterning a photoresist layer over the hard mask layer, wherein openings are formed in the photoresist layer;
• forming cavities in the hard mask layer by performing a first anisotropic etch process that transfers a pattern of the openings in the photoresist layer through the hard mask layer;
• forming via openings through an upper portion of the alternating stack by performing a second anisotropic etch process that transfers a pattern of the cavities in the hard mask layer;
• forming a cladding liner on sidewalls of the cavities in the hard mask layer;
• and
• vertically extending the via openings through all layers within the alternating stack by performing a third anisotropic etch process that employs a combination of the cladding liner and the hard mask layer as an etch mask;
• wherein the hard mask layer comprises a carbon-based hard mask layer comprising at least 60% of carbon in atomic concentration.

A method of forming a semiconductor structure, comprising:

• forming an alternating stack of first material layers and second material layers over a substrate;
• forming a hard mask layer over the alternating stack;
• applying and patterning a photoresist layer over the hard mask layer, wherein openings are formed in the photoresist layer;
• forming cavities in the hard mask layer by performing a first anisotropic etch process that transfers a pattern of the openings in the photoresist layer through the hard mask layer;
• forming via openings through an upper portion of the alternating stack by performing a second anisotropic etch process that transfers a pattern of the cavities in the hard mask layer;
• forming a cladding liner on sidewalls of the cavities in the hard mask layer;
• and
• vertically extending the via openings through all layers within the alternating stack by performing a third anisotropic etch process that employs a combination of the cladding liner and the hard mask layer as an etch mask;
• further comprising forming a memory film and a vertical semiconductor channel in each respective via opening and replacing the second material layers with electrically conductive word lines to form a three-dimensional memory device.

A method of forming a semiconductor structure, comprising:

• forming an alternating stack of first material layers and second material layers over a substrate;
• forming a vertical stack including a first hard mask layer comprising a boron doped carbon-based material and a second hard mask layer having a different material composition than the first hard mask layer over the alternating stack;
• applying and patterning a photoresist layer over second hard mask layer, wherein openings are formed in the photoresist layer;
• forming cavities in the vertical stack by performing a first anisotropic etch process that transfers a pattern of the openings in the photoresist layer through the vertical stack;
• forming via openings through an upper portion of the alternating stack by performing a second anisotropic etch process that transfers a pattern of the cavities in the layer stack;
• and
• vertically extending the via openings through all layers within the alternating stack by performing a third anisotropic etch process.