電感耦合式電漿氮化和氟化處理對鉿矽化合物薄膜之影響

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，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。其中鉿類氧化物為主的材料被認為是目前最有可能來取代二氧化矽。本實驗以鋁-鈦-氧化矽鉿-矽之MIS 結構為分析元件。首先，我們利用化學氣相沉積方法在矽晶片上沉積氧化矽鉿，然後進行500C~800C 不同溫度的沉積後退火步驟，找出最適當的退火溫度。接著再分別進行在氮氣、氨氣、氧化氮和四氟化碳等氣體環境下的表面電漿處理，然後再進行600C30秒的電漿後高溫快速熱退火，最後再沉積鈦和鋁當電極進行量測。我們利用量測電容-電壓曲線和漏電流-電壓曲線去探討氧化層薄膜的基本特性。另外藉由磁滯效應、CVS(constant voltage stress)測試來討論經過電漿處理和沒有經過電漿處理元件的可靠度分析。我們可以發現經過電漿處理的晶片可以承受較高的溫度卻不會降低原本的電容值。這是因為電漿源中的氮原子可以抑制介電層和矽之間的氧化層成長，氟原子可以修補介面處的缺陷降低漏電流，而且電漿處理過後，電容較容易累積電荷，電容值會較高。

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 100 nm, the gate thickness will scale down below 1.2nm, 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. Hf-based dielectric is a most suitable material for future MOSFET gate oxide applications. In this study, we analysis the Al-Ti-HfSiOx-Si MOS structure. First, we deposited HfSiOx on Si wafers individually by chemistic-vapor-deposition (CVD) system. Then, the films received 500oC~800oC different post-deposition-annealing temperature. Find the most appropriate annealing temperature. After PDA, we had additional plasma treatment in different conditions like N2, NH3, N2O and CF4. And then received post-nitridation annealing 600oC 30seconds(PNA). Final, we deposited Ti and Al as electrode to see its electrical characteristic. The electrical characteristics of the film were discussed by C-V and I-V curves. The reliability of the film with nitridation or not were discussed by hystersis effect, CVS(Constant Voltage Stress) test. We could find that that the film with nitridation could sustain high thermal stress, and its capacitance did not decrease. It might be that nitrogen could suppress the formation of interfacial layer between the high-k/Si interface, the fluorine also can repair defects at interface to decrease the leakage current. And the films after nitridation will more easier accumulate charges, the capacity values will be more higher.