過(guò)渡金屬氧化物阻變存儲(chǔ)器動(dòng)態(tài)特性的蒙特卡洛仿真


摘要

　　　隨著集成電路工藝技術(shù)的發(fā)展，以FLASH存儲(chǔ)器為代表的傳統(tǒng)非易失性存儲(chǔ)器在集成電路特征尺寸不斷減小的情況下遇到越來(lái)越多的問(wèn)題。新型非易失性阻變存儲(chǔ)器(RRAM)因其表現(xiàn)出的特征尺寸可縮小性良好、存儲(chǔ)單元結(jié)構(gòu)簡(jiǎn)單、與現(xiàn)代半導(dǎo)體工藝相兼容等特點(diǎn)，引起國(guó)內(nèi)外業(yè)界與學(xué)術(shù)界的廣泛研究。RRAM器件工作過(guò)程中功能層的微觀效應(yīng)和阻變機(jī)理尚未完全明確，影響了RRAM器件的進(jìn)一步研發(fā)與應(yīng)用。
　　　本文中采用動(dòng)力學(xué)Monte Carlo方法，首先對(duì)基于電化學(xué)原理的雙極型RRAM的阻值變化過(guò)程進(jìn)行了仿真，并根據(jù)功能層厚度等因素對(duì)RRAM器件的電特性進(jìn)行了模擬和分析，從而完善了已有的雙極型RRAM模型。
　　　在準(zhǔn)確模擬阻變功能層轉(zhuǎn)變過(guò)程的基礎(chǔ)上，以RRAM器件二維尺寸變化為評(píng)價(jià)標(biāo)準(zhǔn)，分別從電學(xué)性質(zhì)變化、參數(shù)均勻性變化和局域熱效應(yīng)的角度，對(duì)雙極RRAM的工作性能變化進(jìn)行了分析。從模擬結(jié)果可以看出，通過(guò)調(diào)整優(yōu)化RRAM器件的二維尺寸，可以得到較為理想的器件性能，從而應(yīng)用于未來(lái)的存儲(chǔ)器生產(chǎn)中。
　　　其次，通過(guò)對(duì)一維氧空位模型電子占有率的計(jì)算，確定了基于VCM原理的RRAM器件中氧空位產(chǎn)生和復(fù)合發(fā)生的幾率。運(yùn)算所得到的氧空位電子占有率在代入二維動(dòng)力學(xué)Monte Carlo模型后，對(duì)VCM原理的RRAM器件進(jìn)行了電學(xué)轉(zhuǎn)變過(guò)程的仿真。
　　　最后，為了同仿真結(jié)果進(jìn)行對(duì)比討論，驗(yàn)證建模仿真工作的準(zhǔn)確性，制備了W/VOx/Cu阻變存儲(chǔ)單元結(jié)構(gòu)，從而以實(shí)驗(yàn)與建模仿真結(jié)合的方式對(duì)阻變存儲(chǔ)器存儲(chǔ)機(jī)理進(jìn)行了探索。
　　　本文探討了過(guò)渡金屬氧化物RRAM在未來(lái)作為新一代非易失存儲(chǔ)器的電學(xué)特性，尤其是工作過(guò)程中的動(dòng)態(tài)特征，所得到的分析結(jié)果對(duì)將來(lái)RRAM器件的建模理論分析有一定的指導(dǎo)意義，并且對(duì)RRAM器件制備及應(yīng)用也具有一定的指導(dǎo)意義。

關(guān)鍵詞： 阻變存儲(chǔ)器 電化學(xué)原理 Monte Carlo仿真 氧空位導(dǎo)電

Abstract

　　With fast development of modern integrated circuit design and technology, conventional non-volatile memory such as FLASH memory is faced with more issues as it is reaching its physical limitation when critical dimension is scaling down. The emerging resistive RAM (RRAM) is attracting much attention from both manufactures and colleges for its great scalability, simple memory cell structure and good compatibility with IC process. However, the switching mechanism of RRAM device is not thoroughly studied so far, and the local effect in the functional layer of RRAM device is still under debate, all of which hinder further research and fabrication of RRAM.
　　In this paper, we adopted kinetic Monte Carlo method to model the resistive switching process of the device. The electrical characteristics of RRAM device are analyzed with device thickness scaling down, and the current is improved through the simulation.
　　Besides the prediction on switching process of RRAM functional layer, we analyzed the two dimensional impact on the electrical characteristics, parameter uniformity and local heat effect of bipolar RRAM device. From the simulation results it is concluded that through optimizing the device size of RRAM, the switching characteristics of device can be controlled, and RRAM memory with better performances could be expected in further application.
　　With calculation on electron occupancy of one dimensional oxygen vacancy chain, the formation probability of oxygen vacancy (VOs) is obtained. The switching process of valance change RRAM is simulated based on above parameters.
　　In order to discuss with the simulation results to verify the accuracy of the modeling simulation work, the resistive switching device of Si substrate W/VOx/Cu structure was fabricated, and the experiment and modeling simulation are combined for deeper exploration of the resistance change storage mechanism
　　 Above all, the switching process of transitional metal oxide based RRAM were studied in this paper. Switching properties and the aspects of dynamic process of RRAM were systematically studied, which contributes to the further studies of RRAM and its application.
　　
　　Key words：RRAM, Electrochemical Metallization, Monte Carlo method, Oxygen Vacancy Conduction

目    錄
第一章 緒論  1
1.1 引言  1
1.2 阻變存儲(chǔ)器的工作機(jī)理  3
1.2.1 熔絲-反熔絲模型  4
1.2.2 電化學(xué)原理（ECM）模型  5
1.2.3 離子價(jià)變（VCM）模型  6
1.3 阻變存儲(chǔ)器模擬的國(guó)內(nèi)外研究現(xiàn)狀  7
1.4 Monte Carlo方法模擬  8
1.5 本論文的研究意義與內(nèi)容  9
第二章 基于電化學(xué)原理RRAM的Monte Carlo仿真分析  11
2.1電化學(xué)導(dǎo)電細(xì)絲RRAM的Monte Carlo模擬仿真流程  11
2.2 基于陰極導(dǎo)電細(xì)絲的ECM RRAM的KMC模擬仿真步驟  13
2.3 陰極導(dǎo)電細(xì)絲機(jī)理的RRAM仿真結(jié)果與分析  15
2.3.1仿真I-V曲線及導(dǎo)電細(xì)絲生長(zhǎng)的非均勻性  15
2.3.2 阻變層厚度對(duì)阻變轉(zhuǎn)變時(shí)間的影響  17
2.3.3 導(dǎo)電細(xì)絲的形貌分析  18
2.4 本章小結(jié)  19
第三章 雙極型RRAM器件二維尺寸因素影響的模擬分析  20
3.1 雙極型RRAM結(jié)構(gòu)仿真計(jì)算方法  20
3.2 二維尺度效應(yīng)：器件電學(xué)特性變化  20
3.3二維尺度效應(yīng)：均勻性的改善  21
3.4二維尺度效應(yīng)：局域熱效應(yīng)  22
第四章 VCM原理RRAM的仿真模擬  24
4.1基于勢(shì)阱輔助隧穿效應(yīng)的電子占有率計(jì)算  24
4.2電子占有率計(jì)算模型的建立  26
4.3電子占有率模擬仿真結(jié)果分析  27
4.4雙極型氧空位器件阻變過(guò)程描述與建模 29
4.5 Forming阻變過(guò)程的模擬仿真 30
4.6 Reset阻變過(guò)程的模擬仿真  31
4.7本章總結(jié)  33
第五章 Cu/VOx/W結(jié)構(gòu)阻變存儲(chǔ)器的制備與表征  34
5.1 VOx阻變器件的制備  34
5.2 VOx阻變器件物理特性表征  35
5.3 VOx器件的電學(xué)性能表征與分析  37
5.4 Cu/VOx/W結(jié)構(gòu)器件電學(xué)性質(zhì)與電化學(xué)模型仿真的比較與分析  40
第六章 總結(jié)與展望  41
參考文獻(xiàn)  43
發(fā)表論文和科研情況說(shuō)明  48
致   謝  50