微波電漿氮化二氧化鈦轉化成磊晶氮化鈦之研究

Abstract

本論文主要探討以微波電漿氮化非晶與單晶型TiO2，非晶型是利用原子層氣相沉積法(ALD)於Si (100)上成長出厚50 nm之TiO2薄膜，而單晶型則是以Rutile結構之單晶TiO2 (001)，分別進行氮化反應。所形成之氮化物或磊晶TiN將比較其結晶關係與鍵結情形，並研究氮原子在TiO2中轉化成磊晶TiN的氮擴散置換機制。 論文第一部份主要探討非晶型TiO2在不同氮化製程參數下之影響，藉以利用氫氣混合氮氣所形成的氮氫電漿、甲烷混合氮氣所形成的氮碳電漿，與最單純而穩定的純氮氣電漿進行不同氣體的氮化製程比較，研究在非晶TiO2 / Si基板下所造成的氮化效果，並找出最佳的氮化製程參數；而第二部份則以單晶型TiO2作為基材，探討在相同於非晶TiO2所使用的三種電漿氮化氣體下所造成的氮化結果，並與非晶TiO2的結果進行分析與比較。 分析技術方面，利用掃描式電子顯微鏡來觀察氮化後的表面形貌；高解析X光繞射儀進行晶體結構分析；X光光電子能譜儀則用來確認元素縱深分部與化學鍵結組成；最後利用掃描穿透式電子顯微鏡分析TiN與TiO2界面的結晶結構與成份關係。 在研究結果方面，含氫之氮電漿的氮化速率較高，但同時伴隨較嚴重之蝕刻。以非晶型TiO2搭配低壓低功率在三種不同氣體形成的微波電漿氮化後，均能產生結晶性之TiN，具<001>優選方向。另一方面，使用相同實驗條件在單晶型TiO2中進行微波電漿氮化則可以成功氮化出磊晶TiN。 在氮氫電漿的氮化下，可將單晶TiO2表層氮化成(011)面之TiN，直接對應到基板所形成的方向關係為<110> TiO2 // <100> TiN；另外，將輔助氮化氣體由氫氣改為甲烷後，將會產生(001)面之TiN，其磊晶關係為<110> TiO2 // <110> TiN與(001) TiO2 // (001) TiN。最後，在純氮電漿的氮化條件中，形成的氮化鈦如同在氮氫電漿下所得到的(011) TiN，並以<110> TiO2 // <100> TiN與(001) TiO2 // (011) TiN的磊晶關係進行堆疊。

This thesis focuses on the study of nitriding process on different TiO2 templates by using microwave plasma. One of the templates is a 50 nm thick amorphous TiO2 film coated by atomic layer deposition on Si (100), and the other is single crystalline TiO2 of rutile structure in (001). The formed TiN is characterized for its microstructure with crystal orientation and chemical bonding. In the first part of this thesis, the evolution of the amorphous TiO2 for nitridation under different microwave plasma process conditions will be presented. Plasma nitriding processes have been performed with three different gases including N2 / H2 mixture, N2 / CH4 mixture, and pure N2. The second part is devoted to plasma nitriding of rutile TiO2 single crystal in (001) under similar conditions for nitriding amorphous TiO2 / Si. Finally, the results on the single crystal TiO2 will be compared with those on the amorphous TiO2 / Si. The morphology, crystallinity and chemical bonding of TiN after nitridation of TiO2 were characterized by using scanning electron microscopy, high-resolution x-ray diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy and scanning transmission electron microscopy. The results show that the nitrogen plasma with hydrogen can have a higher nitriding rate, while it may have a more significant etching effect. After nitridation of the amorphous TiO2 on Si, polycrystalline TiN in <001> preferred orientation is formed. In contrast, epitaxial TiN can be successfully obtained upon nitridation of the single crystalline TiO2. In the use of nitrogen-hydrogen plasma nitriding, the surface of rutile TiO2 can be nitrided to (011) TiN, and the orientation relationship can be indicated by <110> TiO2 // <100> TiN. In addition, the (001) TiN will be produced when replacing nitrogen-hydrogen plasma to nitrogen-carbon plasma, the epitaxial relationship is <110> TiO2 // <110> TiN and (001) TiO2 // (001) TiN. Finally, for the pure nitrogen plasma, epitaxial (011) TiN is obtained with the same relationship with TiO2 as for the nitrogen-hydrogen plasma.