新穎記憶體及生物感測器元件結構設計、製造與應用

Abstract

奈米科技的發展對於現代的科學、工業、甚至是我們的生活都是一項重要的改革。由於尺寸的微小化，使得物質的物理、化學、及生物特性都與原本相異。本論文係以奈米的技術與材料應用在現今的電子及生物領域，期望能夠讓不同領域的結合迸出火花。本論文分為三個部分，我們將其內容摘要說明如後。 第一部分我們探討矽化鎳薄膜於接面二極體的製程改善。由於電子元件的縮小已達奈米尺度，金屬-半導體接面的工程更形重要。我們研究不同的金屬覆蓋層於矽化鎳薄膜上對於接面二極體的電氣特性影響。我們發現無覆蓋及氮化鈦覆蓋的元件比鈦覆蓋的特性較好，這是由於在鈦覆蓋的樣品中會生成一高阻值的鎳-鈦-矽化合物，而影響元件特性。我們也研究矽化鎳在矽鍺上的熱穩定性。我們發現使用矽/矽鍺堆疊結構會改善矽化鎳薄膜的熱穩定性。另外，矽化鎳於奈米尺度的矽鍺線上會有所謂的窄線效應，但若是在矽/矽鍺堆疊結構的奈米線上則相對穩定。此結果歸因於矽/矽鍺疊層結構的應力作用限制矽化鎳的晶粒成長而延緩其退化。 本論文第二部分探討以溶膠-凝膠法成長奈米微晶粒的機制。我們研究不同的回火溫度對於形成奈米微晶粒的影響。我們發現薄膜於600 °C開始形成島狀，並在900 °C完全轉換成微晶粒。我們提出一個模型來解釋此轉變機制。我們並將奈米微晶粒應用於快閃記憶體的載子補陷層，成功的製作出特性良好的記憶體，其在125 °C、106秒的資料保存力其電荷流失可以小於30%。另外，我們也研究溶劑對於形成奈米微晶粒的影響。我們發現以乙醇為溶劑所形成的奈米微晶粒為分離狀，而以異丙醇為溶劑則為連續狀。此原因歸咎為以乙醇為溶劑所旋轉塗佈而形成的薄膜較薄，此現象有助於形成分離狀的奈米微晶粒。以乙醇系統形成的奈米微晶粒記憶體其記憶視窗比異丙醇系統來的要大，且其資料保存力也較好。我們並製作出一鈦-鋯-矽-氧的化合物奈米微晶粒記憶體，並以新穎的熱電洞作為寫入方式。此記憶體具有4.3伏的記憶視窗、高的資料保存力等特色。此優異的特性歸因於高密度的奈米微晶粒與深井缺陷，因此不會有嚴重的橫向與縱向漏電流。 最後，我們探討以奈米線/奈米帶場效電晶體作為生物分子的感測元件。我們發展一矽奈米線場效電晶體來偵測與癌症相關的BRAFV599E變異基因。我們發現當變異基因接到晶片上時，此奈米線場效電晶體的啟始電壓會變大，而當變異基因脫離時，啟始電壓又會回復到原來的地方。此感測元件也具有分辨一個及五個錯配基因的能力。我們更利用了局部氧化的技術製作一矽奈米帶場效電晶體，並用它來早期偵測肝癌相關的生物記號。此技術的優點是完全相容於互補式金氧半場效電晶體製程，同時又可避免使用較為昂貴的微影設備。為了增加肝癌偵測的精確性及避免假陽性問題，我們分別偵測了甲型胎兒蛋白的抗原、B型肝炎的DNA片段及溶液的酸鹼值-這些都可以當作肝癌偵測的指標。結合微流道系統，我們的奈米帶感測器可以即時、免標定以及高靈敏度的偵測這三種生物指標，或許未來可作為肝癌的早期偵測工具。

The development of nanotechnology is an important revolution to science, industry, and even our life. Because of size-miniaturization, the physical, chemical, and biological properties of the materials are apparently different to original ones. In this thesis, nano-technology and nano-materials are applied to the electronic and biology fields. This thesis is divided into three sections, and is described below briefly. In the first section, the improvement of nickel silicide on the junction diode was demonstrated. Because the device continues to shrink to nano size, the issue about metal-semiconductor interface becomes more and more important. The effects of capping layers on formation and electrical properties of Ni-silicided junctions were investigated. The uncapped and TiN-capped samples were shown to exhibit better thermal stability than the Ti-capped samples. A high-resistivity NixTiySiz compound layer is formed on the surface during silicidation for the Ti-capped sample. In addition, the thermal and morphological stability of NiSi on SiGe film was also investigated. We found that NiSi films formed on poly-Si/poly-SiGe stack layers possessed continuous, smooth structures. Moreover, nickel germanosilicide [Ni(Si,Ge)] line formed on the poly-SiGe exhibited a fine-line effect, whereas NiSi line formed on the poly-Si/poly-SiGe stack layer was very stable. A model for the stress-confined grain growth and recrystallization is proposed to explain the improved properties of the poly-Si-buffered film. In the second section, the formation of nanocrystal by using sol-gel spin-coating method was studied. The formation of the nanocrystals at various annealing temperatures was demonstrated. We found the film started to form the islands at 600 oC anneal, and finally transferred into NCs at 900 °C. A model was proposed to explain the transformation of thin film. The retention for 900 oC annealed nanocrystal memory exhibited less than 30% charge loss after 106 sec at 125 oC measurement. The solvent effect on the formation of nanocrystal was also investigated. The morphology of the nanocrystals for precursors in ethanol system was isolated type, while was interconnected form in IPA system. Ethanol as preparation solvent formed a thinner sol-gel film for spinodal decomposition, and was benefit for formation of isolated nanocrystals. The ethanol system derived NC memory demonstrated a large memory window (9.8 V) than IPA system (3.8 V) due to the isolated NCs. The ethanol system derived NC memory also exhibited better memory performance of retention times for < 5% and < 10% charge loss at 25 °C and 85 °C measurement, respectively. Moreover, a TixZrySizO nanocrystal memory was operated by a novel hot hole trapping method. The memory window of the nanocrystal memory by hot hole trapping can be up to 4.3 V; long retention times are extrapolated up to 106 sec with about 8%, 11%, and 25% charge loss at 25, 85, and 125 °C measurement, respectively. The good electrical performance is attributed to the effects of the high-density isolated nanocrystals and hole-trapped into the deep trap energy level, hence no significant lateral and vertical charge leakage occurs. Finally, high-sensitivity nanowire/nanobelt field effect transistor (FET) was fabricated and for biosensing application. We developed a silicon nanowire FET that allows deoxyribonucleic acid (DNA) biosensing. We employed the BRAFV599E mutation gene, which correlates to the occurrence of cancers, as the target DNA sequence. The threshold voltage of the NWFET increased when the mutation gene was hybridized with the capture DNA strands on the nanowire, and decreased to the original level after de-hybridization of the gene. The detection results of mismatched DNA sequences, including one- and five-base–mismatched DNA strands, could be distinguished from complementary DNA gene by this sensor. Futhermore, we used the local oxidation of silicon (LOCOS) process to fabricate a silicon nanobelt field effect transistor (NB FET). This approach is completely compatible with complementary metal oxide semiconductor (CMOS) technology, yet it avoids the need for expensive lithography tools to define the nanoscale pattern. We employed the fabricated NB FET as a biomolecular sensor for the early, real-time, label-free screening of hepatocellular carcinoma (HCC). To increase the accuracy of HCC screening and prevent false positive identification, we tested the ability of our NB FET to determine alpha-fetoprotein (AFP) as a cancer marker, a DNA fragment from hepatitis B virus (HBV), and the solution pH—all of which can be used as markers for the onset of HCC. This multiplex sensing of AFP, HBV, and the solution pH suggests that our direct, label-free, ultrasensitive biosensor in a microfluidic chip might be applicable as an HCC detector in real samples.