Method for preventing electron secondary injection in a pocket implantation process

A method for preventing electron secondary injection in a pocket implantation process, the pocket implantation process performed to form a nitride read only memory (NROM), the NROM comprising an oxide-nitride-oxide (ONO) layer formed on a silicon substrate, and a plurality of bit line masks having a columnar arrangement formed on the surface of the ONO layer, a plurality of N-type bit lines formed in a region of the substrate that is not covered by the bit line masks, the method comprising:

• performing a pocket implantation process that uses Indium ions and an implantation angle that is nearly parallel to the ONO layer to perform an implantation to the region of the substrate that is not covered by the bit line masks to form a plurality of P-type ultra-shallow doped areas;
• and
• activating the Indium ions in the ultra-shallow doped area so as to form an ultra-shallow junction on the surface of the silicon substrate;
• wherein the pocket implantation process is an ion implantation process that uses a low energy and a high dosage to prevent electron secondary injection in the pocket implantation process.