臺灣博碩士論文加值系統

近年來，懸浮閘極記憶體已經被廣泛低使用在非揮發性的資料儲存上。然而，對於利用複晶矽當作儲存電荷層的傳統式懸浮閘極記憶體元件來說，有幾項主要的缺點是極需被克服的，例如:元件尺寸微縮所面臨的瓶頸、較高的操作電壓、較差的資料保存時間。為了解決上文所述的這些問題，一種擁有分離式儲存電荷節點的奈米點記憶體已經被發表出來，並且極有可能去取代掉原本的懸浮閘極記憶體。
在此篇論文當中，對於非揮發性快閃式記憶體的應用方面，我們提出了一種釓金屬的奈米點記憶體，同時也找出最適合此結構的退火溫度。經過適當退火溫度的處理後，釓金屬的奈米點記憶體展現出高的釓金屬奈米點密度(6.1×1011/cm2)和大的記憶視窗(>3V)。此種記憶體的寫入速度可達1ms，抹除速度大概在1s。除此之外，我們對於在不同退火溫度、不同儲存電荷層厚度、不同上氧化層厚度上，均做了資料保存的特性研究。由此可辨別，直接穿隧的漏電流是經由上氧化層或是穿隧氧化層。由綜合以上的量測結果，在85℃下以及相同電場的條件下，擁有較厚儲存電荷層之釓金屬的奈米點記憶體的電荷流失率與其它厚度的電荷流失率比較起來要來的小，相同的現象也發生在擁有較厚上氧化層的記憶體上。最後，具最佳條件的釓金屬的奈米點記憶體也展現出極佳的耐久特性。

Recently, floating gate memory devices widely be used in non-volatile data storage application. However, there are some major issues including devices scaling limitation, higher operation voltage and poor data retention time needed to overcome for conventional floating gate memory which employed poly-silicon as the charge storage layer. In order to solve these above issues, the nanocrystal memory devices which with discrete charge storage nodes have been proposed to be a possible candidate for the replacement of floating gate memory.
In this thesis, we propose a Gadolinium (Gd) nanocrystal memory structure for nonvolatile flash memory application and also find the optimized post deposition annealing (PDA) temperature. The Gd nanocrystal memory with optimum PDA treatment exhibits high Gd-NC density (6.1×1011/cm2) and large memory window (>3V). The speed of program can be at 1ms and erase at 1s. Besides, data retention time for various (PDA) temperature treatment, blocking oxide layer and charge storage layer has been investigated. It can be discriminated the direct tunneling through the tunneling oxide or blocking. Concluding the measurement results, the memory with thicker charge storage layer shows smaller charge loss rate than other ones at 85℃ and the constant electric field. It also shows the same phenomenon of the memory with thicker blocking. Finally, the Gd nanocrystal memory with optimum condition as well as exhibits superior data endurance characteristics.

Acknowledgement………………………………………………………i
Chinese abstract……………………………………………………ii
English abstract……………………………………………………iii
Content..………………...…………………………………………iv
Content of figure.…………………………………………………vi

Content
Chapter 1 Introduction
1-1 Background ………..…...……………………………………………1
1-2 Metal Nanocrystal memory.………………………….……………2
1-3 The motivation of this study……………………..……………3
1-4 Thesis Organization …………………………………….……....3



Chapter 2 The Property And Material Analysis of Gd Nanocrystal Memory By Transmission Electron Microscope (TEM)
2-1 Introduction ………………………………………..………………...9
2-2 Experiment ……………...…………………………………………...9
2-3 Results and Discussion…………………….………..…………….10
2-4 Summaries ……………………………………….….………........11


Chapter 3 The Characterization of Gd Nanocrystal Memory With Different RTA Treatment
2-1 Introduction ………………………………………..……………….24
2-2 Experiment ……………...………………………………………….24
2-3 Results and Discussion…………………….………..…………….25
2-4 Summaries ……………………………………….….………........28



Chapter 4 The Characterization of Gd Nanocrystal Memory With Different Gd2O3 Thickness
3-1 Introduction ……………………………….…………….………….50
3-2 Experiment ………………………………….…………….………..50
3-3 Results and Discussion……………………………………………..51
3-4 Summaries ……………………………………….…….……........52



Chapter 5 The Characterization of Gd Nanocrystal Memory With Different Blocking Oxide Thickness
4-1 Introduction ……………………………….…………….………….61
4-2 Experiment ………………………………….…………….………..61
4-3 Results and Discussion……………………………………………..62
4-4 Summaries ……………………………………….………….........63


Chapter 6 Conclusions and Future Works
5-1 Conclusion …………….....…….…………………….….…………75
5-2 Future work…………………………………………………………76

Reference ……………………………………………..………….…….77



Content of Figure
Fig. 1-1 The schematic cross section of floating gate memory structure……………………………………………………..6
Fig. 1-2 The schematic cross section of SONOS memory structure...6
Fig. 1-3 The schematic cross section of the metal nanocrystal memory structure…………………………………………..7
Fig. 1-4 The band diagrams of Gd nanocrystal memory structure with (a) program, (b) erase and (c) retention mode……………...8
Fig. 2-1 The process flow of Gd nanocrystal memory……………..16
Fig. 2-2 The HRTEM image of Gd nanocrystal memory with PDA treatment at 950℃. (scale bar: 20 nm)…………………….17
Fig. 2-3 The HRTEM image of Gd nanocrystal memory with PDA treatment at 950℃. (scale bar: 10 nm)…………………….17
Fig. 2-4 The HRTEM image of Gd nanocrystal memory with PDA treatment at 950℃. (scale bar: 5 nm)……………………...18
Fig. 2-5 The HRTEM image of Gd nanocrystal memory with PDA treatment at 950℃. (scale bar: 2 nm)……………………...18
Fig. 2-6 The plane view of the Gd2O3 layer after PDA treatment at 950℃. (scale bar: 20 nm)……………………………19
Fig. 2-7 The plane view of the Gd2O3 layer after PDA treatment at 950℃. (scale bar: 10 nm)……………………………19
Fig. 2-8 The plane view of the Gd2O3 layer after PDA treatment at 950℃. (scale bar: 5 nm)……………………………20
Fig. 2-9 The elements percentage of the Gd2O3 layer after PDA treatment at 950℃…………………………………………21
Fig. 2-10 The lattice constant value of the Gd nanocrystal………….22
Fig. 2-11 The electron diffraction pattern of the Gd nanocrystal……23
Fig. 3-1 The process flow of Gd nanocrystal memory with different PDA temperature………………………………………….31
Fig. 3-2 The HRTEM images of Gd nanocrystal memory with PDA treatment at 800℃…………………………………………32
Fig. 3-3 The HRTEM images of Gd nanocrystal memory with PDA treatment at 850℃…………………………………………33
Fig. 3-4 The HRTEM images of Gd nanocrystal memory with PDA treatment at 900℃…………………………………………34
Fig. 3-5 The HRTEM images of Gd nanocrystal memory with PDA treatment at 950℃…………………………………………35
Fig. 3-6 The plane view of the Gd2O3 layer after PDA treatment at 800℃………………………………………………………36
Fig. 3-7 The plane view of the Gd2O3 layer after PDA treatment at 850℃………………………………………………………36
Fig. 3-8 The plane view of the Gd2O3 layer after PDA treatment at 900℃………………………………………………………37
Fig. 3-9 The plane view of the Gd2O3 layer after PDA treatment at 950℃………………………………………………………37
Fig. 3-10 The Gd-NC density dependence on PDA temperature….. 38
Fig. 3-11 C-V hysteresis of Gd-NC memory structures with 800℃ to 950℃ PDA treatment swept from -11V to +11V. Memory window of all samples was shown in inset………………..39
Fig. 3-12 C-V hysteresis curves of memory after PDA treatment at 800℃ demonstrated the memory is repeatable. ……………...40
Fig. 3-13 C-V hysteresis curves of memory after PDA treatment at 850℃ demonstrated the memory is repeatable. ……………...40
Fig. 3-14 C-V hysteresis curves of memory after PDA treatment at 900℃ demonstrated the memory is repeatable. ……………...41
Fig. 3-15 C-V hysteresis curves of memory after PDA treatment at 950℃ demonstrated the memory is repeatable. ……………...41
Fig. 3-16 Retention characteristics of Gd-NC memories measured at room temperature. ……………………………………….42
Fig. 3-17 Retention characteristics of Gd-NC memories measured at 55℃. ………………………………………………………42
Fig. 3-18 Retention characteristics of Gd-NC memories measured at 85℃. ………………………………………………………43
Fig. 3-19 Arrhenius plot of charge loss for Gd-NC memories.
The plots were obtained from charge loss characteristics at retention time for 10ks. …………………………………...43
Fig. 3-20 Schematic energy band diagrams of Gd-NC memory structure under thermal activation mode for 850℃ and 900℃ PDA treatment. …………………………………….44
Fig. 3-21 Retention characteristics of Gd-NC memories with constant electric field stress (flat-band). ……………………45
Fig. 3-22 Retention characteristics of Gd-NC memories with constant electric field stress (E=2.8MV/cm). …………………45
Fig. 3-23 Schematic energy band diagrams of Gd-NC memory structure under constant electric field mode for 850℃ and 900℃ PDA treatment. …………………………………….46
Fig. 3-24 The data endurance characteristic of Gd-NC memory structure after PDA treatment at 800℃. ………………….47
Fig. 3-25 The data endurance characteristic of Gd-NC memory structure after PDA treatment at 850℃. ………………….48
Fig. 3-26 The data endurance characteristic of Gd-NC memory structure after PDA treatment at 900℃. ………………….49
Fig. 4-1 The process flow of Gd nanocrystal memory with different Gd2O3 thickness. …………………………………………53
Fig. 4-2 C-V hysteresis curves of the memory structure with Gd2O3 layer (deposition time: 20min). …………………………..54
Fig. 4-3 C-V hysteresis curves of the memory structure with Gd2O3 layer (deposition time: 25min). …………………………..54
Fig. 4-4 C-V hysteresis curves of the memory structure with Gd2O3 layer (deposition time: 30min). …………………………..55
Fig. 4-5 C-V hysteresis curves of Gd2O3 layer (deposition time: 20min) demonstrated the memory is repeatable. ………55
Fig. 4-6 C-V hysteresis curves of Gd2O3 layer (deposition time: 25min) demonstrated the memory is repeatable. ………56
Fig. 4-7 C-V hysteresis curves of Gd2O3 layer (deposition time: 30min) demonstrated the memory is repeatable. ………56
Fig.4-8 C-V curves of Gd2O3 layer (deposition time: 20min) which program +11V 10s and erase -11V 10s. …………………..57
Fig. 4-9 C-V curves of Gd2O3 layer (deposition time: 25min) which program +11V 10s and erase -11V 10s. …………………..57
Fig. 4-10 C-V curves of Gd2O3 layer (deposition time: 30min) which program +11V 10s and erase -11V 10s. …………58
Fig. 4-11 Retention characteristics of Gd-NC memories measured at room temperature. ……………………………………….58
Fig. 4-12 Retention characteristics of Gd-NC memories measured at 55℃. ………………………………………………………59
Fig. 4-13 Retention characteristics of Gd-NC memories measured at 85℃. ………………………………………………………59
Fig. 4-14 Retention characteristics of Gd-NC memories with constant electric field stress (flat-band). ……………………60
Fig. 4-15 Retention characteristics of Gd-NC memories with constant electric field stress (E=2.5MV/cm). …………………60
Fig. 5-1 The process flow of Gd nanocrystal memory with different Gd2O3 thickness. …………………………………………64
Fig. 5-2 C-V hysteresis curves of the memory structure with blocking oxide 5nm. ………………………………………………...65
Fig. 5-3 C-V hysteresis curves of the memory structure with blocking oxide 8.5nm. ………………………………………………65
Fig. 5-4 C-V hysteresis curves of the memory structure with blocking oxide 12nm. ……………………………………………….66
Fig. 5-5 C-V hysteresis curves of the memory with blocking oxide 5nm demonstrated the memory is repeatable. ……………66
Fig. 5-6 C-V hysteresis curves of the memory with blocking oxide 8.5nm demonstrated the memory is repeatable. …………67
Fig. 5-7 C-V hysteresis curves of the memory with blocking oxide 12nm demonstrated the memory is repeatable. ………….67
Fig. 5-8 C-V curves of the memory with blocking oxide 5nm which program +11V 10s and erase -11V 10s. …………………..68
Fig. 5-9 C-V curves of the memory with blocking oxide 8.5nm which program +11V 10s and erase -11V 10s. …………………..68
Fig. 5-10 C-V curves of the memory with blocking oxide 12nm which program +11V 10s and erase -11V 10s. …………………..69
Fig. 5-11 Retention characteristics of Gd-NC memories measured at room temperature. ……………………………………….69
Fig. 5-12 Retention characteristics of Gd-NC memories measured at 55℃. ………………………………………………………70
Fig. 5-13 Retention characteristics of Gd-NC memories measured at 85℃………………………………………………………..70
Fig. 5-14 Retention characteristics of Gd-NC memories with constant electric field stress (flat-band)………………………71
Fig. 5-15 Retention characteristics of Gd-NC memories with constant electric field stress (E=2.5MV/cm)……………………71
Fig. 5-16 The data endurance characteristic of Gd-NC memory structure with blocking oxide 5nm………………………..72
Fig. 5-17 The data endurance characteristic of Gd-NC memory structure with blocking oxide 8.5nm……………………...73
Fig. 5-18 The data endurance characteristic of Gd-NC memory structure with blocking oxide 12nm………………………74



List of Tables

Table 1. The parameters of Gd nanocrystal………………………12
Table 2. The TEM system………………...………………………...13
Table 3. The detail process of Gd nanocrystal memory ……14
Table 4. The detail process of Gd nanocrystal memory with different PDA temperature………………………………………….29

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