Method of forming low resistance common source line for flash memory devices

摘要

A low resistance common source line (12) for high performance NOR-type flash memories cells in different bit-lines but on the same word-line is used to reduce the memory core cell size and to improve the circuit density as the device dimensions are scaled down. For advanced flash memory technology where shallow trench isolation (STI) (4) is used, the common source formation (12) is facilitated by a VCI implant (11) performed before STI field oxide fill (5). The process sequence is to first form the trenches (4) for the subsequent STI (4), then apply the VCI mask (10) and perform the VCI high energy ion implant (11) to form the “future” source line (12). Then field oxide fill (5) is deposited into the STI trench (4) to form the desired field isolation structures and the memory circuit is completed using conventional techniques.