Demonstration and Understanding of Nano-RAM Novel One-Time Programmable Memory Application

In prior researches, carbon nanotube (CNT)-based nano-random access-memory (NRAM) uses reset initialization which obtains >10
¹¹
high write endurance for large-time programmable (LTP) application. In this paper, for the first time, NRAM one-time programmable (OTP) application is proposed by using set initialization for data archive. Specifically, virgin NRAM cells are all in high resistance state (HRS) for storing bit “0.” In contrast, set initialization uses reversed polarity voltage to obtain low resistance state (LRS) for bit “1.” Furthermore, physical models of set initialization and retention current degradation are proposed for the first time. The current increment during set initialization can be attributed to electron tunneling and CNT deformation. Retention current degradation may be due to variation of paralleled CNT contacts in bottleneck zone. As for OTP performance, median NRAM bit and 1% tail bit demonstrate more than 1 billion years and 15 years data retentions, respectively, on 150 °C. The tail bit activation energy is 2.41 eV. Finally, no LRS read disturb is found after 10 s 0.5-V stress on both polarities. The virgin NRAM cells in HRS should be more stable than set initialized NRAM cells in LRS for both retention time and read disturb.