沉積後電漿處理對二氧化鉿金氧半導體結構電特性之影響

Abstract

當場效電晶體的閘極介電層厚度微縮至1.5 奈米厚時，將產生一些諸如電子穿遂效應等嚴重的問題。因此極需以高介電係數材料取代二氧化矽作為閘極絕緣層，其中二氧化鉿就是目前被認為最有可能取代二氧化矽的材料。本實驗以鋁-二氧化鉿-矽之MIS 電容結構為分析元件。首先利用直流濺鍍法沉積鉿金屬，接著以低溫通氧氣的爐管氧化金屬鉿，而得到氧化鉿薄膜。接下來，試片在氧化後立刻去做各種不同時間的電漿處理，其氣體來源分別是氮氣，一氧化二氮，氧氣。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，並討論二次離子質譜儀的特性圖。另外也藉由磁滯效應、SILC特性、定電壓加壓測試和崩潰電荷分佈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，其中以通一分鐘氮氣電漿的樣品的呈現出最大的電容質(增加了50%)，最小的漏電流(兩個數量級的下降)，以及優異的可靠度。這是因為氮氣電漿處理會抑制介面氧化層的成長，所以其電容值在被電漿傷害破壞前，會因修補介面的效應而持續的增加。另一方面，雖然一氧化二氮和氧氣電漿處理在較短的製程時間內依然是可行的改良電性的方法，但由於其容易促生額外氧化層的特性，使得其電容值還是比氮氣電漿處來得小。

When the MOSFET gate insulator is scaled below 1.5 nm, some serious problems such as direct electric tunneling will occur. Therefore, high dielectric constant material is very desirable to replace SiO2. Hafnium oxide is a most promising material for future MOSFET gate oxide applications. In this study, we used Al-HfO2-Si MIS capacitor as our analysis device. First, we used DC sputter system to deposit hafnium metal and then proceeded with furnace under oxidation at low temperature to prepare HfO2 thin film. After oxidation process, we had an additional plasma treatment with N2, N2O, or O2 plasma for different process durations. The electrical characteristics of the film under different oxidation conditions were discussed by C-V and I-V curves. Moreover, the SIMS (Secondary Ion Mass Spectrometer) profile was also analyzed. The reliability of the film under different plasma treatment conditions were discussed by hysteresis effect, SILC ( Stress Induced Leakage Current ) profile, CVS ( Constant Voltage Stress ) test, and QBD ( charge-to-breakdown ) distribution. Among these conditions, the sample treated by N2 plasma for 1 minute represents the largest capacitance ( 50%increasement ), lowest leakage current ( 2 order reduction ), and excellent reliability. Since the N2 plasma treatment can suppress the the formation of interfacial oxide between the high-k/Si interface, the capacitance of the high-k dielectric can take advantage from the N2 plasma treatment before the plasma damage occur. On the contrary, the N2O and O2 plasma can improve the interface characteristics in short period, the property that they are easy to form an additional oxide layer in the high-k/Si interface will degrade the dielectric’s capacitance when compared with N2 plasma treatment