Radical Treatment in Supercritical Fluid for Gate Dielectric Quality Improvement to CFET Structure

A method, comprising:

• providing a semiconductor structure having top channels;
• forming a first dielectric layer that is wrapping around the top channels in the top channels;
• performing a first radical treatment to the first dielectric layer in a first supercritical carbon dioxide fluid having a first radical chemical dissolved therein;
• forming a second dielectric layer over the first dielectric layer and wrapping around the top channels, the second dielectric layer having a dielectric constant greater than that of the first dielectric layer;
• and
• performing a second radical treatment to the second dielectric layer in a second supercritical carbon dioxide fluid having a second radical chemical dissolved therein, the second radical chemical being different from the first radical chemical.

A method, comprising:

• forming bottom channels vertically stacked on a bottom substrate;
• forming a bottom source and a bottom drain on the bottom substrate, the bottom source and the bottom drain being interposed by the bottom channels;
• forming a bottom interfacial layer wrapping around each of the bottom channels;
• performing a thermal annealing process to the bottom interfacial layer at a first temperature greater than 900° C.;
• forming a semiconductor stack of first semiconductor layers and second semiconductor layers alternatively stacked on a top substrate;
• bonding the semiconductor stack formed on the top substrate to the bottom substrate;
• thinning down the top substrate such that the semiconductor stack is exposed;
• patterning the semiconductor stack to form an active region;
• forming a top source and a top drain in the active region interposed by top channels;
• forming a top gate dielectric layer wrapping around the top channels;
• and
• performing a radical treatment to the top gate dielectric layer in a supercritical carbon dioxide fluid at a second temperature less than 200° C.