Method of making a self-aligned ferroelectric memory transistor

A method of making a self-aligned ferroelectric memory transistor, comprising:

• preparing a substrate, including forming a p-well, depositing a first dielectric layer over the p-well, and forming a layer of n+ polysilicon over the first dielectric layer;
• forming shallow wenches for use in a shallow trench isolation process, wherein the shallow trenches extend through the polysilicon, the first dielectric layer, and about 500 nm of the substrate;
• depositing silicon oxide in the shallow trenches;
• removing the polysilicon except in active areas;
• depositing a bottom electrode on the polysilicon;
• forming a self-aligned gate stack, including:
• depositing a layer of silicon nitride to a thickness of between about 200 nm to 400 nm thick;
• patterning and selectively etching the silicon nitride, the bottom electrode and the polysilicon, wherein the patterned and etched bottom electrode defines a bottom electrode area;
• selectively etching the polysilicon to the level of the first dielectric layer;
• and
• implanting and activating ions to form a source region and a drain region, wherein the source region and drain region are aligned with the bottom electrode area and wherein neither the source region nor the drain region underlie the bottom electrode area;
• depositing a layer of silicon oxide, wherein the silicon oxide layer is between about 1.5 times to 2.0 times the thickness of the gate stack;
• planarizing the silicon oxide layer to the level of the silicon nitride;
• removing the silicon nitride;
• forming a sidewall barrier layer by depositing a layer of barrier metal in a thickness of between about 5 nm to 30 nm;
• depositing a layer of ferroelectric material on the bottom electrode covering the bottom electrode area and aligned therewith;
• forming a top electrode structure on the ferroelectric material including depositing top electrode metal on the ferroelectric stack, including depositing a material taken from the group of materials consisting of Ir, Pt, and Ir—Pt alloy, wherein the top electrode structure coven the bottom electrode area and is aligned therewith;
• and
• finishing the structure, including passivation, oxide depositing and metallization.

A method of making a self-aligned ferroelectric memory transistor, comprising:

• preparing a substrate, including forming a p-well, depositing a first dielectric layer over the p-well, and forming a layer of n+ polysilicon over the first dielectric layer;
• forming shallow trenches for use in a shallow trench isolation process, wherein the shallow trenches extend through the polysilicon, the first dielectric layer, and about 500 nm of the substrate;
• depositing silicon oxide in the shallow trenches;
• removing the polysilicon except in active areas;
• depositing a bottom electrode on the polysilicon;
• forming a gate stack, including:
• depositing a layer of silicon nitride to a thickness of between about 200 nm to 400 nm;
• patterning and selectively etching the silicon nitride, the bottom electrode and the polysilicon, wherein the patterned and etched bottom electrode has an outer margin;
• selectively etching the polysilicon to the level of the first dielectric layer;
• and
• implanting and activating ions to form a source region and a drain region, wherein the source region and the drain region each have an edge aligned with the bottom electrode outer margin and wherein the source region and drain region do not underlie any portion of the bottom electrode;
• depositing a layer of silicon oxide, wherein the silicon oxide layer is between about 1.5 times to 2.0 times the thickness of the gate stack;
• planarizing the silicon oxide layer to the level of the silicon nitride;
• removing the silicon nitride;
• forming a sidewall barrier layer by depositing a layer of barrier metal in a thickness of between about 5 nm to 30 nm;
• depositing a layer of ferroelectric material on the bottom electrode, the ferroelectric material having margins coincident with the bottom electrode outer margin;
• forming a top electrode structure on the ferroelectric material including:
• depositing a layer of silicon nitride to a thickness of between about 100 nm to 300 nm on the ferroelectric stack;
• etching the silicon nitride layer to form a control gate placeholder;
• depositing a layer of oxide over the structure and planarizing the oxide to the top of the silicon nitride layer;
• removing the silicon nitride;
• and depositing top electrode metal on the ferroelectric stack, wherein the top electrode overlays the ferroelectric material and the bottom electrode, and wherein the margins of the top electrode are coincident with the bottom electrode outer margin;
• and
• finishing the structure, including passivation, oxide depositing and metallization.