本文關鍵詞： 阻變存儲器 電致電阻效應 ZnO CuO_x/Si WO_3　出處：《武漢理工大學》2013年博士論文　論文類型：學位論文

【摘要】：電阻型隨機存儲器(RRAM)是一類非常有前途的新型非易失性半導體存儲器�；谶^渡金屬氧化物材料的RRAM器件具有“價格低,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,是新一代非易失性存儲器的有力候選者。經過十多年地發(fā)展,相關器件的制備和新材料體系的開發(fā)上有了明顯進展。然而RRAM領域中仍然存在很多問題需要解決,物理機制還不清晰,而阻變參數分散和阻變位置的不可控性等問題也困擾著RRAM的應用。本文以ZnO, CuOx/Si和WO3氧化物材料作為研究對象,在微結構、工作機理以及研究方法等方面對RRAM的關鍵技術進行研究,主要得到以下結果： (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,該器件與其他已報道的氧化物基RRAM器件相比具有最小的轉變閾值電壓值(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。 同時我們在Ag/AgOx/Zn0.8Mg0.2O/Pt器件中實現了雙極性和單極性兩種轉變方式的可控轉換。研究表明Ag/AgOx/Zn0.8Mg0.20/Pt器件的電阻轉變過程中焦耳熱效應和電場致離子遷移運動并存,相互競爭。當離子遷移運動占主導地位時,器件表現出雙極性轉變行為。通過對雙極性器件的高阻態(tài)進行短時脈沖處理,該器件從雙極性轉變轉換為單極性轉變。脈沖處理使Zn0.8Mg0.2O層中的絲通道發(fā)生變形,焦耳熱效應起主導作用,器件表現出單極性轉變行為。隨后對單極性器件進行負向偏壓掃描,一定條件下,器件的阻變類型轉換為雙極性轉變。這種特性使該器件能夠根據不同的需要在兩種轉變方式之間進行轉換,擴展了器件的應用范圍。 (2)利用CuOx/Si界面氧化還原反應生成結構均勻的SiOx絕緣層,成功制備了具有類均勻轉變特性的Pt/CuOx/Si/Pt器件。該器件具有漸變的電形成過程(GE過程),隨著電壓掃描次數的增加,電阻值逐漸增加,同時電容值逐漸減小。我們通過對比試驗、復阻抗譜圖、I-V曲線的對稱性、氧化還原反應公式、界面層有效厚度的計算及AES深度剖析逐步證實了CuOx/Si界面SiOx層的存在,并且該層對器件類均勻轉變特性起了至關重要的作用。GE過程實質上是電壓掃描過程中界面處發(fā)生氧化還原反應,SiOx層厚度逐漸增加導致。 通過對I-V曲線和交流電導率的分析對器件的電輸運特性,低阻態(tài)的弛豫行為和電阻轉變機制進行了詳細地研究。器件的電輸運特性表現為空間電荷限制電流機制(SCLC),初始態(tài)器件中SiOx層結構較為完整,缺陷含量少,因此不存在淺陷阱控制的SCLC過程。經過電壓掃描后,Cu+/Cu2+離子進入SiOx層中,成為電子躍遷的陷阱,使器件表現出淺陷阱控制的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+離子的弛豫時間和擴散系數也隨之增加,離子濃度降低,即低阻態(tài)的弛豫過程由Cu+/Cu2+離子擴散出SiOx層導致。復電導率實部隨頻率變化的曲線高頻下符合.fβ型(β～1)的交流電導行為,表明弛豫中心或躍遷勢壘分布均勻,Cu+/Cu2+離子在SiO、層中分布較均勻，進而使器件表現為類均勻轉變。該工作為制備均勻轉變器件提供了新的思路和方法。 (3)采用C-AFM技術研究了WO3-x阻變薄膜的導電特性。發(fā)現Au/WO3-x/Au平面器件的導電通道的電阻狀態(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,遠離白色區(qū)域的部分電阻稍高。WO3-x/glass薄膜顆粒表現出顆粒邊界導電的特性,同時邊界的導電性具有不均勻性。WO3-x/Pt薄膜顆粒則表現出晶粒內部導電的特點。WO3-x/Pt薄膜顆粒存在均勻導電和不均勻導電兩種導電行為。顆粒的不均勻導電是由顆粒內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.

【學位授予單位】：武漢理工大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TP333

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