電漿處理氧化鋁鉿閘極介電層之研究

Abstract

隨著場效電晶體的尺寸縮小到1.2奈米以下，以二氧化矽當作閘極介電層，將產生一些諸如電子穿遂效應的問題。摩爾定律將面臨無法繼續適用的窘境，因此需以高介電係數材料取代二氧化矽作為閘極絕緣層，其中鉿為基礎的氧化物就是目前被認為最有可能取代二氧化矽的材料。但是矽和高介電係數材料的介面卻會有缺陷過多的問題，我們利用電漿氮化來解決此問題。本實驗以鋁-鈦-氧化鋁鉿-矽之電容結構為分析元件。首先利用金屬有機化學沉積法沉積氧化鋁鉿介電層。接下來，試片在氧化後立刻去做快速熱退火及各種不同時間的電漿處理，其氣體來源分別是氮氣，氨氣及一氧化二氮，最後再做快速熱退火去修補電漿處理後的表面。在不同電漿處理條件下的薄膜電性，經由C-V 和I-V 量測得知。另外也藉由高溫熱處理、磁滯效應、應力引致漏電流測試、定電壓加壓測試及昇溫量測來討論各種電漿處理條件下元件的可靠度。在這些條件之中，其中以通三十秒一氧化二氮電漿的樣品呈現出第二大的電容值(增加了25.1%)，最小的漏電流(兩個數量級的下降)，以及優異的可靠度。這是因為一氧化二氮電漿處理中的氮原子會修補介面的缺陷，而氧原子會增加介面氧化層厚度來抑制漏電流，所以其電容值及漏電流在被電漿傷害破壞前，會因修補介面的效應而持續的改善。另一方面，氮氣和氨氣電漿處理在適當製程時間內依然是有效改良電性的方法。

When the MOSFET gate insulator is scaled below 1.2 nm, SiO2 as the gate insulator will has some serious problems such as direct tunneling. The moore’s law will face difficult condition to continue constantly. Therefore, high dielectric constant material is desired to replace SiO2. The oxide of using Hafnium-based is a most promising material for future MOSFET gate oxide applications. But the interface of between Si and high dielectric constant material has many defects, we will use plasma nitridation to solve this problem. In this study, we used Al-Ti-HfAlO-Si MIS capacitor as our analysis device. First, we used MOCVD system to deposit HfAlO. After oxidation process, we had an additional post-deposition annealing and then plasma treatment with N2, NH3, or N2O plasma for different process durations. Finally, the samples are treated by post-nitridation annealing to repair the surface of after plasma treatment. The electrical characteristics of the film under different oxidation conditions were discussed by C-V and I-V curves. Moreover, the reliability of the films under different plasma treatment conditions were discussed by high temperature treatment, hysteresis effect, SILC ( Stress Induced Leakage Current ) profile, CVS ( Constant Voltage Stress ) test and increasing temperature measurement. Among these conditions, the sample treated by N2O plasma for 30 sec represents the second capacitance ( 25.1 % increasing ), lowest leakage current ( 2 order reduction ), and excellent reliability. Since the nitrogen atoms of N2O plasma treatment can repair the defects of the interface, the oxygen atoms can form additional interfacial oxide between the high-k/Si interface to suppress the leakage current. The capacitance and the leakage current of the high-k dielectric can be improved by the N2O plasma treatment before the plasma damage occurring. On the contrary, the N2 and NH3 plasma treatment of the suitable time are also good methods to improve the interface characteristics.