Study of C4F8 gas for etch process in slow erase failure of flash memory devices

In manufacturing of flash memory devices, etch processes have a very critical role to make device of good qualities, especially etch-process of common source area has a strong impact on slow-erase failure of flash memory, so we have studied which is the effective parameter of etch process in slow-erase failure mode, finally we have found that the flow rate of C4F8 gas in etch-process of common source is the main effective parameter. The less the flow rate of C4F8 gas, the more the vertical loss of active area in common source region which leads to slow-erase failure. the vertical loss of active area in common source region extend the current path, eventually leads to higher resistance of the circuit of transistor, higher resistance reduces the drain current of floating gates which eventually leads to slow-erase.