非揮發性記憶體(NVM)在元件尺寸持續微縮下的需求為高密度記憶單元、低功率損耗、快速讀寫操作、以及良好的可靠度(Reliability)。傳統的非揮發性記憶體是利用複晶矽浮停閘(floating gate)作為載子儲存的單元，而在元件尺寸持續微縮下將面臨一些瓶頸。在操作過程中如果穿隧氧化層產生漏電路徑會造成所有儲存電荷流失回到矽基板，所以在資料保存時間(Retention)和耐操度(Endurance)的考量下，難以微縮穿隧氧化層的厚度。非揮發性奈米點記憶體被提出希望可取代傳統浮動閘極記憶體，利用半導體或金屬奈米點作為電荷儲存的單元，由於奈米點可視為電荷儲存層中彼此分離的儲存點，可以減少穿隧氧化層的厚度，增進小尺寸記憶體元件多次操作下的資料儲存能力，而不損失可靠性，進而降低操作電壓及操作速度增快。近年來發展許多方法來形成奈米點，大多數的方法都需長時間高溫的熱製程，此步驟會影響現階段半導體製程中的熱預算和產能。而超臨界二氧化碳(supercritical carbon dioxide, SCCO2)已有實驗證明能修補介電層的處理，且在高壓環境下降低反應活化能，因此評估其有製作奈米點的潛力。
本文中為了探討使用低溫超臨界二氧化碳成長奈米點技術的可行性，因此選用低熔點金屬錫(Sn)作為實驗材料，而為確定錫是否能成功製作奈米點元件，故先使用一般較成熟的熱退火技術嘗試製作。我們使用一個快速熱退火製程來增進奈米點的結晶性(crystalline)和記憶體的可靠度，熱處理可以減少奈米點周圍氧化矽中的缺陷(defect)。首先在矽晶圓穿隧氧化層上沈積錫與氧化矽(SiO2)共鍍的薄膜，在後續不同溫度的熱處理狀況下使錫奈米點析出，並分析其電性及材料性質的變化。另外又比較沈積錫與矽(Si)共鍍的薄膜，一樣在不同溫度熱處理下析出錫奈米點，研究儲存層中不同錫含量記憶效應以及電性分析。
之後選擇了錫與氧化矽共鍍的薄膜嘗試做超臨界二氧化碳的處理，製成元件後探討奈米點的記憶窗口以及電性做討論。由於這是種新穎的製作方式，詳細的製程機制與原理、參數改善與性能提升還需後續更深入的探討。

Current requirements of nonvolatile memory (NVM) are the high density cells, low-power consumption, high-speed operation and good reliability for the scaling down devices. However, all of the charges stored in the floating gate will leak into the substrate if the tunnel oxide has a leakage path in the conventional NVMs. Therefore, the tunnel oxide thickness is difficult to scale down in terms of charge retention and endurance. The nanocrystal nonvolatile memories are one of promising substitution, because the discrete storage nodes as the charge storage media have been effectively improve data retention under endurance test for the scaling down device. Many methods have been developed recently for the formation of nanocrystals. Generally, most methods need thermal treatment with high temperature and long duration. This procedure will influence thermal budget and throughput in current manufacture technology of semiconductor industry. And supercritical carbon dioxide (SCCO2) has been researched to the passivation of dielectric and reducing the activation energy. The research estimates SCCO2 is potential to form nanocrystals for these reason.
This research is to discuss the feasibility of fabricating nanocrystal NVMs device with low temperature SCCO2. The low melting point metal material Sn is used for the attempts. In order to check if Sn can be used for fabricating nanocrystal NVMs device, the research selects the conventional thermal annealing method first. It uses rapid thermal annealing to improve the crystalline of nanocrystals and reliability of the memory device. Compare to different Sn containment or chemistry and different process, analyze the electric characteristics and materials chemistry.
At last, select the Sn and SiO2 co-sputtering film to try the SCCO2 process and analyze these characteristics as well. Due to the novel technology, many physical mechanism and improvement of properties will be discuss following.

Chinese Abstract…………………………………………………….....Ⅰ
English Abstract………………………………………………………..Ⅱ
Contents…………………………………………………………...……Ⅲ
Figure Captions…………………………………………………….......Ⅴ
Chapter 1 Introduction
1.1 Overview of Nonvolatile Memory……………………………………...1
Chapter 2 Basic Principle of Nonvolatile Memory
2.1 Introduction.............................................................................................9
2.2 Basic Program/Erase Mechanisms........................................................10
2.2.1 Energy band diagram during program and erase operation…....10
2.2.2 Carrier injection mechanisms………………………...………...11
2.3 Basic Reliability of Nonvolatile Memory.............................................13
2.3.1 Retention……………………………………………………….14
2.3.2 Endurance……………………………………………………....14
2.4 Basic Physical Characteristic of Nanocrystal NVM.............................15
2.4.1 Quantum Confinement Effect………………………….……....15
2.4.2 Coulomb Blockade Effect………………………………...……15
2.5 Supercritical Carbon Dioxide (SCCO2)………………………………16
Chapter 3 Attempt to Fabricate Sn-NCs Nonvolatile Memory
3.1 Motivation…………………………………………………………….22
3.2 Experiment Procedures………………………………………………..22
3.3 Results and Discussion………………………………………………..23
3.4 Conclusions…………………………………………………………...26
Chapter 4 Advanced Fabrication by Tin Silicide (SnSi) Chemistry
4.1 Motivation…………………………………………………………...33
4.2 Experiment Procedures………………………………………………..33
4.3 Results and Discussion………………………………………………..34
4.4 Conclusions…………………………………………………………36
Chapter 5 Another Study of Reducing Sn Containment by Sandwich Structure at Storage Layer
5.1 Motivation…………………………………………………………….43
5.2 Experiment Procedures………………………………………………..43
5.3 Results and Discussion………………………………………………..44
5.4 Conclusions…………………………………………………………...46
Chapter 6 The SCCO2 Method to Fabricate Nanocrystal NVMs
6.1 Motivation…………………………………………………………….54
6.2 Experiment Procedures………………………………………………..54
6.3 Results and Discussion………………………………………………..55
6.4 Conclusions…………………………………………………………...57
Chapter 7 The Leakage Mechanism of Storage Layer with Sn Core-SnOx Shell Structure………………...……………….….62
7.1 Phenomenon………………………...………………………………...62
7.2 View of Energy Band……………...………………………………….62
7.3 View of Material Defects…………….………………………………..63
Chapter 2 Conclusions………………………………………………………..68
References…………………………………………………………………………69

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