| 摘要 |
Methods are described to fabricate, program, and sense a multilevel one-time-programmable memory cell including a steering element such as a diode and two, three, or more dielectric antifuses in series. The antifuses may be of different thicknesses, or may be formed of dielectric materials having different dielectric constants, or both. The antifuses and programming pulses are selected such that when the cell is programmed, the largest voltage drop in the memory cell is across only one of the antifuses, while the other antifuses allow some leakage current. In some embodiments, the antifuse with the largest voltage drop breaks down, while the other antifuses remain intact. In this way, the antifuses can be broken down individually, so a memory cell having two, three, or more antifuses may achieve any of three, four, or more unique data states.
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