鈀薄膜奈米蝕刻技術應用在成長層狀薄膜合成

Abstract

本論文研究目的在於開發一個金屬鈀的原子層蝕刻製程技術，未來能應用在其成長硫化物層數的控制。蝕刻的過程由兩個步驟組成，分別為表面改質與化學移除。第一步，我們選用快速升溫加熱的方法對金屬鈀薄膜進行表面氧化改質; 第二步，藉由高溫蒸發甲酸溶液進行氧化層移除，甲酸可以選擇性蝕刻掉鈀跟氧的結而不蝕刻鈀。蝕刻率取決於氧化過程中所形成之氧化鈀層的厚度。在 300oC進行氧化並利用濃度 0.1M的甲酸進行蝕刻，得最小蝕刻率 0.684 奈米/循環。此蝕刻製程經多次重複循環得之誤差值小，證明甲酸蝕刻製程的穩定與再現性。本實驗同時進行鈀金屬的硫化物開發，利用傳統加熱爐，將硫粉和試片放在爐中，藉由改變硫粉用量、反應溫度與加熱速率，在溫度為450oC，經由 Raman 、 XRD與 TEM分析得知成功合成均勻二硫化鈀層狀薄膜。這二硫化鈀材料具半導體性，我們分別將它製作成電晶體跟光感測器來探討它的特性。作為電晶體元件，我們從量測的曲線中萃取出的載’子遷移率與開關比分別為 217.9 cm2/Vs 以及 103。在光感測器方面，我們在特定電壓下利用不同波長的光源照射，量測其特性。其中以638nm照射下有最佳的響應值22 毫安培/瓦、外部量子效率=7.48%、D*=4.68×1011。當二硫化鈀厚度降低光電響應效果更為明顯。相較二硫化鉬，二硫化鈀除了同樣有不錯的光、電特性外，也有較佳的室溫穩定特性與較低的製程溫度，對後段三維元件堆疊整合發展是相當具有發展潛力的材料與應用。In this study, we investigate an approach for Palladium film etch which is suitable for layer formation control in Palladium sulfide synthesis. The etch process is divided into two steps including the surface modification and modified layer removal. In the first step, rapid thermal oxidation process was used to change the surface conditionfor oxide formation. Following by the soaked in formic acid steam to remove the oxided layer. After the XPS analysis, formic acid could selectively etch the oxide layer and nearly no etch loss examined in Palladium film. The etch rate is closely depent on the formed oxie thickness and the minimum etch rate 0.65nm/cycle was obtained at 300oC with 0.1M formic acid concentration. A stable etch results performed after cyclic etch process with the same etch condition shown that the etch process is reliable and repeatable.The sulfuization process of Palladium film was interested to developed. The Palladium film was sputtered on SiO2/Si substrate before sulfurization. The sample and sulfer powder were loaded into a conventional furnace within an atmosphere of 5%H2 and Ar. The optimal silfirized layered PdS2 data examined by Raman, XRD and TEM was obtained when the temperature was 450oC. The layered PdS2 was semiconductor and was interest for field effect transistor and photodiode device fabrication. For transistor device, the extracted field effect mobility and on/off ratio are 217.9 cm2/Vs and 103, respectively. For photodiode device, variant wavelength of light sources were applied to elluminate the PdS2 film under a contained bias. The highest response was obtained when the wavelength was 638nm and the calculated Responsibility (S), EQE and the Detectivity(D*) were 22 mA/W, 7.48 % and 4.68×1011, respectively. The thinner PdS2 film has better optical response performance. Compared to the well developed MoS2 film, except the good electrical and optical properties, layered PdS2 film with excellent room temperature stability and lower synthesis temperature are promising to integrate into the existing back-end process for 3D device stacking IC application.