METHOD FOR FORMING A HIGH-k GATE STACK WITH REDUCED EFFECTIVE OXIDE THICKNESS

A method for forming a gate dielectric stack, the method comprising:

• providing a silicon-containing substrate;
• forming a silicon oxide interface layer on the silicon-containing substrate,
• the silicon oxide interface layer having a first equivalent oxide thickness;
• depositing a rare earth oxide first high-k film on the silicon oxide interface layer;
• heat-treating the rare earth oxide first high-k film and the silicon oxide interface layer to a temperature that forms a modified interface layer having a second equivalent oxide thickness that is equal to or lower than the first equivalent oxide thickness;
• and
• depositing a hafnium-oxygen-based second high-k film on the modified interface layer.

A method for forming a gate dielectric stack, the method comprising:

• providing a silicon-containing substrate;
• forming a silicon oxide interface layer on the silicon-containing substrate, the silicon oxide interface layer having a first equivalent oxide thickness;
• depositing a lanthanum oxide first high-k film on the silicon oxide interface layer by an atomic layer deposition process;
• heat-treating the lanthanum oxide first high-k film and the silicon oxide interface layer to a temperature equal to or greater than 900° C. to form a modified interface layer having a second equivalent oxide thickness that is equal to or lower than the first equivalent oxide thickness;
• and
• depositing a second high-k film on the modified interface layer.