金屬有機高分子析出奈米金顆粒之記憶效應研究

Abstract

奈米顆粒記憶體利用不連續的charge traps 做為介電層的儲電器有希望取代傳統DRAM或Flash memories，引起許多學術研究的注意。雖然DRAM有良好的開關特性，但高功率的消耗造成自記憶時間減短。另外高密度的DRAMs製作也是非常困難的。Flash memories因穿隧氧化層很厚而有高操作電壓和慢讀寫速度的缺點。經由work function engineering，金奈米顆粒被推薦為進一步提高此類元件性能的方法之一。本論文中，我們使用金屬有機高分子將金奈米粒子析出的方法取代用金薄膜快速升溫退火以獲得更均勻的金奈米粒子。旋轉塗佈方式只需要少量metal-organic polymer即可完成沉積奈米顆粒的製備，比起典型用自組裝來製備奈米金顆粒--需要相當久的時間才能達到高密度奈米粒子的覆蓋率。另外，自組裝法需要大量的奈米粒子溶液才能將欲製備的基材做完整的浸泡，這些因素都會增加製程的成本。金屬有機高分子於旋佈機上經過45秒的旋佈，一層含有金原子的聚合物經適合的方式以碳一碳建結在晶圓上，接著將晶圓加溫250oC，經25至55分鐘後即可沉積奈米顆粒，過程中有機高分子轉變成二氧化碳和水將被帶走。我們將金屬有機高分子旋佈在SiO2(10nm)/Si並以250 ℃烤25至55分鐘得到金奈米顆粒，接著使用PECVD疊上10奈米的SiO2，最後於SiO2和晶背再鍍上Au/Ti做為電極以量測其儲電的特性，並觀察到其記憶特性。

Nanoparticles memories employing discrete charge traps as the charge storage media have attracted a lot of research attention as the promising candidates to replace conventional DRAM or Flash memories. DRAMs allow fast write/erase, but suffer from high power consumption due to their short retention time. It is also very difficult to fabricate high density DRAMs. Flash memories have the drawbacks of high operation voltage and slow write/erase because of their relatively thick tunnel oxide. Gold nanoparticles memories have been proposed as one of the approaches to further enhance the performance of such devices through work function engineering. In this study, we used a novel and simple approach to perform gold nanoparticles layers onto SiO2/Si sample by using metal-organic polymer spin deposition, to displace gold nanoparticles from RTA for evenly nanoparticles. Metal-organic polymer is designed for application with a spinner. After 45 seconds of spinning, a fairly hard film will form on the wafer which contains gold atoms attached through suitable groupings to the carbon-carbon backbone forming the polymer. The wafer is then heated to 250 ℃ to 300 ℃. In 25 to 55 minutes gold decomposition will occur, and CO2 and H2O which pass out the diffusion tube. We have been adopted to provide metal-organic polymer spin deposition onto SiO2 (10 nm)/Si to generate nanopatterns and followed by 250□C bake process for 25 to 55 minutes. Next, the silicon dioxide layer with 10 nm in thickness by using the PECVD process was deposited on the samples. After Au/Ti metallic layer was deposited on double sides, contact pads were defined with conventional lithography and lift-off process for electrical characteristic measurement. In this study, we have successfully utilized the decomposition metal-organic polymer such that gold nanoparticles formed onto silicon oxide surface and memory effect observed.