超薄二氧化鉿閘極絕緣層之特性研究

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於P型和N型矽基板上，所沉積的金屬鉿厚度為20 Å，接著以低溫通氧氣的爐管，分別在200℃、300℃、400℃和500℃下以15分鐘或30分鐘氧化金屬鉿，得到氧化鉿薄膜，其中部份試片在氧化後立刻以850℃的快速熱退火處理30秒。在不同氧化條件下的薄膜電性，經由C-V和I-V量測得知，並討論量子效應的漏電流機制，另外也藉由磁滯效應、崩潰分佈、定電流加壓測試和在高溫下量測來討論各種氧化條件下元件的可靠度。在相同的等效厚度下，二氧化鉿薄膜在1伏特下的漏電流比二氧化矽薄膜少了兩個數量級以上。在相同的氧化條件下，P型二氧化鉿電容比N型二氧化鉿電容有較好的電特性及可靠度，氧化溫度越高會產生越厚的介面層，使得薄膜等效厚度增加，可靠度也變差，但可改善磁滯效應。此外，以快速熱退火處理二氧化鉿薄膜無法改善薄膜特性。

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 20 Å hafnium metal on p-type and n-type silicon substrate. Then we proceeded with furnace under 200℃, 300℃, 400℃ and 500℃ oxidation temperature and 15 or 30 minutes oxidation time to prepare HfO2 thin film. After oxidation process, we had an additional RTA treatment at 850℃ for 30 seconds. The electrical characteristics of the film under different oxidation condition were discussed by C-V and I-V curves. Moreover, the conduction mechanism with quantum effect was also analyzed. The reliability of the film under different oxidation condition was discussed by hysteresis effect, breakdown distribution, constant current stress and high temperature measurement. With the same equivalent oxide thickness (EOT), the magnitude of leakage current of HfO2 film is less than that of SiO2 film over 2 orders at 1 V. Under the same oxidation condition, p-type HfO2 capacitor has better electrical characteristics and reliability than n-type HfO2 capacitor. Under higher oxidation temperature, it would result in thicker interfacial layer, larger EOT, worse reliability but better hysteresis. In addition, RTA treatment couldn’t improve the quality of HfO2 film.