液相沉積絕緣膜之高品質化探討

Abstract

由過去的研究，我們發現：液相沈積絕緣膜技術(LPD)具有室溫成長，自然含氟以及省能的諸多優點，使其在複晶系薄膜電晶體的製程上極具應用潛力。此外，在液相沈積絕緣膜製程中，我們必須先將矽基板做先期表面氧化處理，使得基板表面成長厚度約一奈米的前置氧化層。為了使絕緣膜的沈積最佳化，我們認為：該層氧化膜的品質必然十分重要。因此，本研究之目的之一為尋求絕緣膜的最佳化。經由實驗發現，加熱的硫酸與雙氧水約三比一的混合液所形成的氧化膜能使得絕緣膜同時具有低漏電流，高崩潰電壓以及較高可靠度的特性。儘管如此，該溶液所產生約160度的高溫將使得抗熱性較差的基板無法應用此製程。然而，許多的文獻指出，臭氧水具有強烈的氧化能力，能夠有效清除雜質與污染，更重要的是它能夠在室溫下於矽基版上成長絕佳的氧化膜，除此之外，臭氧水容易分解，並不會造成環境污染與廢水處理的問題，這對於半導體製造成本的降低有莫大的助益，因此，本研究的另一個重點就是探討運用臭氧水進行基板前處理在液相沈積絕緣膜技術上的可應用性。實驗發現：高濃度臭氧水所形成的前置氧化膜能得使絕緣膜具有低漏電流，高崩潰電壓，以及高可靠度的優良電特性。所以，臭氧水在液相沈積絕緣膜的應用上具有極大的優勢。

In the previous study, we find that LPD insulator technology having strengths of room-temperature process, incorporation with fluorine, and saving energy. These merits make it possesses a high potential of application in the fabrication of poly-Si TFT. In addition, In the process of LPD insulator, we must pre-oxidize the Si substrate in order to grow a pad oxide about 10Å before the deposition of LPD insulator. For the purpose of the improvement of LPD insulator, we are of the opinion that the quality of pad oxide dominates the quality of LPD insulator. Consequently, one of the goals in this study is to find an optimum method to enhance the LPD insulator. From the experiments, it is found that the mixture of H2SO4 (98%) which is pre-heated to 60oC and H2O2 (30%) with the ratio of 3/1 form a high quality pad oxide so that the LPD insulator is characterized by low leakage current, high breakdown field, and higher reliability. Nevertheless, the process temperature up to about 160oC induced by this pre-treatment will prohibit the application to the substrates with low thermal stability. Fortunately, Many science literatures point out that ozonized water has very high oxidation potential to effectively remove impurities and contamination in IC industry. To be more important, it can form high quality native oxide on substrates at room temperature. Moreover, ozone is easy to decompose by UV irradiation, and makes us free from the post-treatment of waste chemicals and environmental pollution such that the costs for semiconductor manufacturing can be effectively decreased. As a result, another focus in our study is to investigate the feasibility of ozonized water pre-treatment for LPD insulator technology. Experiments show that the LPD insulator in high concentration ozonized water pre-treatment exhibits excellent electrical characteristics such as low leakage current, high electric breakdown field, and high reliability. Therefore, the predominance of ozonized water pre-treatment is distinctly revealed for LPD insulator technology in the future.