不同表面處理對二氧化鉿與二氧化鋯推疊式高介電常數材料薄膜之效果

Abstract

隨著金氧半場效電晶體的微縮，傳統使用二氧化矽當作閘極介電層將面臨到物理和電性的限制。當電晶體的閘極通道長度微縮到100奈米以下時，閘極介電層厚度將縮小至1.2奈米以下，以二氧化矽當作氧化層將會面臨到很多的挑戰，影響最嚴重的就是太薄的二氧化矽絕緣層會使大量載子直接穿隧造成大量的漏電流，為了有效抑制此漏電流，需要使用高介電係數材料來取代二氧化矽作為閘極氧化層，高介電係數氧化層可以在維持相同的等效氧化層厚度(維持相同的電容值)的情況下，增加實際介電層厚度來抑制穿遂電流的形成。其中二氧化鉿與二氧化鋯為主的材料被認為是目前最有可能來取代二氧化矽。 本研究製造了鈦-二氧化鉿-二氧化鋯-矽金屬絕緣層矽(MIS)結構之電容,作為分析的樣品。首先，我們探討二氧化鋯介面層有無做沉積後退火處理和矽表面上有無氟化處理的電性比較。接下來，在二氧化鉿薄膜上，使用不同氣體(氮氣、氧化氮與氨氣)做不同時間下的電漿處理，並且從這些不同條件中挑選最佳的電漿處理條件。最後，我們比較了沒做任何處理、沉積後退火處理、氟化處理與氮化處理等不同表面處理方法，探討對特性的影響。在論文中，由結果可以發現經過退火與電漿處理後的介電質薄膜，可以得到較高的電容密度、較低的漏電流以及較小的磁滯現象。這是因為退火處理可以有效改善薄膜品質、電漿源中的氟原子可以抑制介電層和矽之間的氧化層成長並且修復介電質中的缺陷，而氮原子可以修補介電層的缺陷。

The aggressive scaling of MOS devices is quickly reaching the fundamental and electric limits of convention SiO2 as the gate insulator. When the gate length scales down below 100nm, the gate thickness will scale down below 1.2 nm, the SiO2 gate dielectric will face severe challenges, the most critical influence is that too thin SiO2 gate dielectric will let a lot of carriers direct tunnel to form large leakage current. Therefore, high dielectric constant gate oxide with large physical thickness while identical equivalent oxide thickness (equivalent capacity value) have been used to replace SiO2 in order to reduce gate leakage current. HfO2 and ZrO2 dielectric are the most suitable materials for future MOSFET gate oxide applications. In this study, we fabricated Ti-HfO2-ZrO2-Si MIS capacitor as our analysis device. First, we compared the electrical characteristics with PDA treatment and without on ZrO2 layer. Then, we compared the electrical characteristics with fluorination treatment and without on Si surface. Second, the HfO2 thin films were treated in different source gas (N2, N2O, and NH3) for different time, and we selected the best conditions among these conditions. Final, the various surface treatments such as without treatment, PDA treatment, fluorination, and nitridation are compared and studied. In this thesis, after PDA and plasma treatment, the results show higher capacitance, lower leakage current density, and lower hysteresis voltage. It might be that PDA can effectively improve gate dielectric quality, the fluorine could suppress the formation of interfacial layer between the ZrO2/Si interface, the nitrogen also can repair defects at bulk dielectric to decrease the leakage current.