The Reliabilaty Research Of Resistor Random Access Memory

With the development of modern integreted circuit manufacturing processes, the Flash memory based on floating gate structure is gradually toward tis physical size limit, the development of new memory has become the hot research point in institutions and major semiconductor manufacturers. The resistor random access memory(RRAM) with the advantages of low power, high speed, simple structure, easy to 3D integration, and compatible with conventional CMOS processes has caused wide range of concerns. However, since the mechanism of RRAM is not yet clear, and can not meet the reliability requirements of the market, therefore, it is mainly for the study in the laboratory. This article is based 1T1 R RRAM devices institutional problems in terms of reliability, and some methods is adopted to improve the uniformity of the device.The ‘T’ in 1T1 R structure uses standard 0.13 um technology, produced by the company and some RRAM devices with different materials are growed on the ‘T’ in order to achieve different properties. This paper experiments are mainly based on RRAM device with Cu / Hf Ox / Pt structure, the Cu electrode is the drain terminal of the transistor is formed after the CMP process, and determined the area of the device, while the functional layer and the upper electrode Pt is Hf Ox process to achieve different according to different needs.In the article, firstly, the reason that caused reliability issues in 1T1 R RRAM device is analysed. The information stored of RRAM device is realized through high and low resistance state, when the high and low resistance states are very closer, it is possible to cause the read error; on the other hand, the same device or different devices under the same operating conditions will display different state, resulting in information storage error. When the device is stayed in a long time, the state of resistance will will be also changed and caused error messages stored. These are some reason that caused reliability issues.In order to explain the reasons that caused reliability issues from the experiment, we do the endurance test on single device and retention test on 1T1 R array tests. In the endurance test, we studied distribution of low and high resistance states with long cycles test and found that the resistance will be decreased with increased number of cycles, especially for the low resistance state. In the retention test, we counted 1kb size of the array at different temperatures to analysis the relationship between the time the device resistance state, the low resistance state the device will fail in a high impedance state, and high impedance devices will become low-resistance state, or more a high resistance state.Meanwhile this paper also do the experiments on RRAM multi-value storage, and discusses the different property of multi-storage achieved by SET and RESET processes. Through the RTN(Random Telegraph Noise) test, the multi-value obtained by SET process is better than that achieved by RESET process.