Three-dimensional ferroelectric memory device and method of making thereof

A method of forming a three-dimensional memory device, comprising:

• forming an alternating stack of insulating layers and sacrificial material layers over a substrate;
• forming vertical semiconductor channels through the alternating stack;
• and
• replacing the sacrificial material layers with combined spacers, each of which comprises a ferroelectric liner and an electrically conductive layer, after forming the vertical semiconductor channels,
• wherein the method comprises at least one feature selected from:
• a first feature that the method further comprises:
• forming a backside trench through the alternating stack of the insulating layers and the sacrificial material layers, and removing the sacrificial material layers by providing an etchant that etches the sacrificial material layers selective to the insulating layers through the backside trench, wherein backside recesses are formed in volumes from which the sacrificial material layers are removed, wherein the combined spacers are formed in the backside recesses;
• a second feature that the method further comprises:
• patterning the alternating stack to form a terrace region in which each sacrificial material layer except a topmost sacrificial material layer has a greater lateral extent than overlying sacrificial material layers, forming a retro-stepped dielectric material portion over the alternating stack in the terrace region, and forming a plurality of contact via structures through the retro-stepped dielectric material portion and on a top surface of a respective one of the electrically conductive layers within the terrace region;
• and
• a third feature that that the ferroelectric material liners comprise an orthorhombic metal oxide of which a unit cell has a permanent non-zero electric dipole moment, and the orthorhombic metal oxide comprises an orthorhombic hafnium doped zirconium oxide or an orthorhombic hafnium oxide doped with a dopant having an atomic radius that is between 40% smaller than to 15% larger than the atomic radium of hafnium.

A method of operating a ferroelectric three-dimensional memory device comprising an alternating stack of word lines and insulating layers, a vertical semiconductor channel, a source region, a drain region and a ferroelectric memory elements, the method comprising:

• writing a selected first ferroelectric memory material element between a selected word line and the vertical semiconductor channels into a state that locally decreases a threshold voltage inside the vertical semiconductor channel at a level of the selected word line by applying:
• a current flow bias voltage across the source region and the drain region of the vertical semiconductor channel;
• a selected word line voltage to the selected word line, wherein the selected word line voltage is a greater positive voltage with respect to voltages applied to the source region and the drain region;
• and
• an unselected word line voltage to each unselected word line that is less positive than the selected word line voltage.