發(fā)布時(shí)間：2018-01-19 08:25

  本文關(guān)鍵詞： 阻變存儲(chǔ)器 電致電阻效應(yīng) ZnO CuO_x/Si WO_3　出處：《武漢理工大學(xué)》2013年博士論文　論文類型：學(xué)位論文

【摘要】：電阻型隨機(jī)存儲(chǔ)器(RRAM)是一類非常有前途的新型非易失性半導(dǎo)體存儲(chǔ)器�；谶^渡金屬氧化物材料的RRAM器件具有“價(jià)格低,功率小,速度快,與CMOS工藝兼容性更好及物理性能更豐富”等優(yōu)點(diǎn),是新一代非易失性存儲(chǔ)器的有力候選者。經(jīng)過十多年地發(fā)展,相關(guān)器件的制備和新材料體系的開發(fā)上有了明顯進(jìn)展。然而RRAM領(lǐng)域中仍然存在很多問題需要解決,物理機(jī)制還不清晰,而阻變參數(shù)分散和阻變位置的不可控性等問題也困擾著RRAM的應(yīng)用。本文以ZnO, CuOx/Si和WO3氧化物材料作為研究對(duì)象,在微結(jié)構(gòu)、工作機(jī)理以及研究方法等方面對(duì)RRAM的關(guān)鍵技術(shù)進(jìn)行研究,主要得到以下結(jié)果： (1)通過在Ag/Zn0.8Mg0.2O之間添加緩沖層AgOx,成功得到具有穩(wěn)定阻變性能及極小轉(zhuǎn)變閾值電壓的雙極性Ag/AgOx/Zn0.8Mg0.2O/Pt器件。該雙極性器件具有非常窄的轉(zhuǎn)變閾值電壓和高低組態(tài)電阻值分布,σ/μ值分別為6.7%(Vset),11.8%(Vreset),9%(LRS),29.5%(HRS)。同時(shí),該器件與其他已報(bào)道的氧化物基RRAM器件相比具有最小的轉(zhuǎn)變閾值電壓值(Vset:0.11V～0.19V; Vreset:-0.14V～-0.18V),大大降低了器件在使用過程中的能量消耗。 同時(shí)我們?cè)贏g/AgOx/Zn0.8Mg0.2O/Pt器件中實(shí)現(xiàn)了雙極性和單極性兩種轉(zhuǎn)變方式的可控轉(zhuǎn)換。研究表明Ag/AgOx/Zn0.8Mg0.20/Pt器件的電阻轉(zhuǎn)變過程中焦耳熱效應(yīng)和電場(chǎng)致離子遷移運(yùn)動(dòng)并存,相互競(jìng)爭(zhēng)。當(dāng)離子遷移運(yùn)動(dòng)占主導(dǎo)地位時(shí),器件表現(xiàn)出雙極性轉(zhuǎn)變行為。通過對(duì)雙極性器件的高阻態(tài)進(jìn)行短時(shí)脈沖處理,該器件從雙極性轉(zhuǎn)變轉(zhuǎn)換為單極性轉(zhuǎn)變。脈沖處理使Zn0.8Mg0.2O層中的絲通道發(fā)生變形,焦耳熱效應(yīng)起主導(dǎo)作用,器件表現(xiàn)出單極性轉(zhuǎn)變行為。隨后對(duì)單極性器件進(jìn)行負(fù)向偏壓掃描,一定條件下,器件的阻變類型轉(zhuǎn)換為雙極性轉(zhuǎn)變。這種特性使該器件能夠根據(jù)不同的需要在兩種轉(zhuǎn)變方式之間進(jìn)行轉(zhuǎn)換,擴(kuò)展了器件的應(yīng)用范圍。 (2)利用CuOx/Si界面氧化還原反應(yīng)生成結(jié)構(gòu)均勻的SiOx絕緣層,成功制備了具有類均勻轉(zhuǎn)變特性的Pt/CuOx/Si/Pt器件。該器件具有漸變的電形成過程(GE過程),隨著電壓掃描次數(shù)的增加,電阻值逐漸增加,同時(shí)電容值逐漸減小。我們通過對(duì)比試驗(yàn)、復(fù)阻抗譜圖、I-V曲線的對(duì)稱性、氧化還原反應(yīng)公式、界面層有效厚度的計(jì)算及AES深度剖析逐步證實(shí)了CuOx/Si界面SiOx層的存在,并且該層對(duì)器件類均勻轉(zhuǎn)變特性起了至關(guān)重要的作用。GE過程實(shí)質(zhì)上是電壓掃描過程中界面處發(fā)生氧化還原反應(yīng),SiOx層厚度逐漸增加導(dǎo)致。 通過對(duì)I-V曲線和交流電導(dǎo)率的分析對(duì)器件的電輸運(yùn)特性,低阻態(tài)的弛豫行為和電阻轉(zhuǎn)變機(jī)制進(jìn)行了詳細(xì)地研究。器件的電輸運(yùn)特性表現(xiàn)為空間電荷限制電流機(jī)制(SCLC),初始態(tài)器件中SiOx層結(jié)構(gòu)較為完整,缺陷含量少,因此不存在淺陷阱控制的SCLC過程。經(jīng)過電壓掃描后,Cu+/Cu2+離子進(jìn)入SiOx層中,成為電子躍遷的陷阱,使器件表現(xiàn)出淺陷阱控制的SCLC過程。在低阻態(tài)弛豫的過程中,SiOx層的厚度沒有發(fā)生變化,電阻增加后,Cu+/Cu2+離子的弛豫時(shí)間和擴(kuò)散系數(shù)也隨之增加,離子濃度降低,即低阻態(tài)的弛豫過程由Cu+/Cu2+離子擴(kuò)散出SiOx層導(dǎo)致。復(fù)電導(dǎo)率實(shí)部隨頻率變化的曲線高頻下符合.fβ型(β～1)的交流電導(dǎo)行為,表明弛豫中心或躍遷勢(shì)壘分布均勻,Cu+/Cu2+離子在SiO、層中分布較均勻，進(jìn)而使器件表現(xiàn)為類均勻轉(zhuǎn)變。該工作為制備均勻轉(zhuǎn)變器件提供了新的思路和方法。 (3)采用C-AFM技術(shù)研究了WO3-x阻變薄膜的導(dǎo)電特性。發(fā)現(xiàn)Au/WO3-x/Au平面器件的導(dǎo)電通道的電阻狀態(tài)分為兩部分,其中靠近白色區(qū)域(與電極相連的高阻區(qū))的弧形區(qū)域電阻最低,遠(yuǎn)離白色區(qū)域的部分電阻稍高。WO3-x/glass薄膜顆粒表現(xiàn)出顆粒邊界導(dǎo)電的特性,同時(shí)邊界的導(dǎo)電性具有不均勻性。WO3-x/Pt薄膜顆粒則表現(xiàn)出晶粒內(nèi)部導(dǎo)電的特點(diǎn)。WO3-x/Pt薄膜顆粒存在均勻?qū)щ姾筒痪鶆驅(qū)щ妰煞N導(dǎo)電行為。顆粒的不均勻?qū)щ娛怯深w粒內(nèi)部氧缺陷分布不均勻造成。
[Abstract]:Resistive random access memory (RRAM) is a very promising new type nonvolatile semiconductor memory device. RRAM transition metal oxide based material has low price, small power, speed, and better physical properties and CMOS process compatibility more abundant advantages, is a new generation of non easily lost strong candidates memory. After more than 10 years of development, has been significant progress in the development of related devices and new material preparation system. However, in the field of RRAM there are still many problems to be solved, the physical mechanism is not clear, but the resistance variable parameter dispersion and resistance change position is not controllable and other problems plaguing RRAM the application of ZnO. In this paper, CuOx/Si and WO3 oxide materials as the research object, in the micro structure, the paper studies the key technology of RRAM's working mechanism and research methods, the main results are as follows:
(1) by adding AgOx buffer layer between Ag/Zn0.8Mg0.2O with bipolar Ag/AgOx/Zn0.8Mg0.2O/Pt device performance and minimal change threshold voltage stability resistance successfully. The bipolar device has a very narrow transition threshold voltage and low resistance value distribution configuration, sigma / mu = 6.7% (Vset), 11.8% (Vreset). 9% (LRS), 29.5% (HRS). At the same time, the device with other reported oxide based RRAM devices compared with the change of the minimum threshold voltage (Vset:0.11V ~ 0.19V; Vreset:-0.14V ~ -0.18V), greatly reduce the energy consumption in the process of the device in use.
At the same time we realized controllable bipolar and unipolar two mode conversion in Ag/AgOx/Zn0.8Mg0.2O/Pt devices. The results show that the Joule heat resistance transformation process of Ag/AgOx/Zn0.8Mg0.20/Pt device in the electric field induced effect and ion migration movement coexist, compete with each other. When the ion migration is dominant, the device exhibits bipolar short pulse transition behavior. By dealing with the high resistance state of bipolar devices, the device from bipolar transformation for unipolar pulse processing transformation. The wire channel in the Zn0.8Mg0.2O layer is deformed, the Joule heat effect should play a leading role, the device exhibits unipolar behavior. Then the unipolar device for negative bias scanning, certain under the condition of device type conversion for bipolar resistive transition. This feature allows the device to be according to different needs in between the two ways of transformation The conversion extends the application range of the device.
(2) the reduction reaction of uniform structure SiOx insulation layer using CuOx/Si interface oxidation, Pt/CuOx/Si/Pt device with uniform change characteristics were prepared successfully. The formation process of the electric device has a gradual (GE process), with the increase of voltage scanning frequency, the resistance value increases gradually, while the capacitance decreases. We compared test, complex impedance spectra, the symmetry of the I-V curve, the redox reaction formula, calculation and AES depth analysis of the effective thickness of interface layer gradually confirmed the CuOx/Si interface SiOx layer, and the layer of uniform change characteristics of the device class played a crucial role in the.GE process is essentially a voltage scanning process at the interface the redox reaction, the thickness of SiOx layer leads to a gradual increase.
Through the analysis of I-V curve and AC conductivity on device electrical transport properties, relaxation behavior and resistance change mechanism of the low resistance state were studied in detail. The electric performance device transport properties for the space charge limited current mechanism (SCLC), the initial state of SiOx in device layer structure is complete, the content of defects less, so there is no SCLC shallow trap control. After scanning voltage after Cu+/Cu2+ ion into the SiOx layer, become the electronic transition trap, the device showed SCLC process control. The shallow trap in the process of low resistance state relaxation, SiOx layer thickness does not change, the resistance increased after. The relaxation time and diffusion coefficient of Cu+/Cu2+ ions increases, ion concentration decreased, the low resistance relaxation process by Cu+/Cu2+ ion diffusion SiOx layer. In the real part of the complex conductivity with frequency variation curve under high frequency with.F beta (beta - 1). AC conductance behavior indicates that the distribution of relaxation centers or transition barriers is uniform. The distribution of Cu+/Cu2+ ions in SiO layer is more uniform, which makes the devices behave like homogeneous transformation. This work provides new ideas and methods for the preparation of uniform transformation devices.
(3) to study the characteristics of WO3-x conductive resistive films using C-AFM technology. It was found that the resistance state of conductive channel Au/WO3-x/Au planar device is divided into two parts, which is close to the white area (high resistance region connected with the electrodes) arc area resistance minimum, away from the white area of slightly higher resistance.WO3-x/glass film grains show conductive properties of grain boundaries, while conductivity boundary has inhomogeneity of.WO3-x/Pt thin films showed the internal characteristics of grain particles of.WO3-x/Pt thin film conductive particles exist uniform conductive and nonuniform conductive behavior. Two kinds of conductive particles by nonuniform conductive particles inside the oxygen defect distribution is not uniform.

【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TP333

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