| 摘要 |
<p>PROBLEM TO BE SOLVED: To make narrower the width of threshold distribution, after a product for one-time writing has been erased by reducing the manufacturing unit price of a chip as much as possible by separately forming chips for one application in which the rewriting of electric data is performed repeatedly and another application in which writing is performed only once. SOLUTION: A method for manufacturing nonvolatile semiconductor storage device includes a wafer manufacturing process (ST1) for commonly manufacturing an electrical erasable and programmable ROM(EEPROM) in which data rewriting is repeatedly performed against a memory cell array and one time programmable ROM(OTPROM), in which data writing is done only once in the state of wafers, an initial erasing process (ST3) in which at least the OTPROM is erased by irradiating the OTPROM with ultraviolet rays, and a process (ST4), in which the chips of the EEPROM and OTPROM are packaged by covering the chips with a material which does not transmit ultraviolet rays. It is preferable to protect the OTPROM from erasure, by inhibiting the output of an erasure permission signal to the memory cell array side, and so on, by the use of a nonvolatile memory element which is conducted, when the element is irradiated with the ultraviolet rays (ST3) in the manufacturing process.</p> |
