| 摘要 |
PURPOSE:To execute a nondestructive screening in a short time by erasing data while being changed up to a region in which all bits in a memory region are erased from a region sufficiently weaker than a rated value and discriminating acceptable or defective devices from the form of distribution of an obtained erasing rate when screening an erasable ROM. CONSTITUTION:Program voltage and program width are set previously under conditions sufficiently weaker than rated values in an initial input process at a step 1, and data are written under rated writing conditions are at a step 2. Data are erased under erasing conditions set at the step 1 in an erasing process at a step 3, and an erasing rate is obtained are recorded previously to a tape an an erasing-rate computing process at a step 4. The erasing of all bits is decided at a step 5, and either of said voltage or width is changed at a step 6 and data are returned to the step 2 on a non-erasing. The erasing rate is acquired at a step 7 on an erasing, and acceptable or defective devices are judged from the form of distribution of the erasing rate. |
