Nitride barrier layer for protection of ONO structure from top oxide loss in a fabrication of SONOS flash memory

A method for fabricating a SONOS device having a buried bit-line including the steps of:

• providing a semiconductor substrate having an ONO structure overlying the semiconductor substrate;
• forming a silicon nitride barrier layer on the ONO structure to form a four-layer stack;
• forming a patterned photoresist layer on the nitride barrier layer;
• implanting ions through the four-layer stack to form a bit-line buried under the ONO structure;
• stripping the photoresist layer and cleaning an exposed surface of the four-layer stack;
• and
• consolidating the four-layer stack by applying an oxidation cycle.

A method for fabricating a SONOS device having a buried bit-line including the steps of:

• providing a semiconductor substrate having an ONO structure overlying the semiconductor substrate;
• forming a nitride barrier layer on the ONO structure to form a four-layer stack;
• forming a patterned photoresist layer on the nitride barrier layer;
• implanting ions through the four-layer stack to form a bit-line buried under the ONO structure;
• stripping the photoresist layer and cleaning an upper surface of the four layer stack;
• and
• consolidating the four-layer stack by applying an oxidation cycle, wherein implanted ions are driven from the ONO structure into the bit-line.