自我鈍化型銅鉿合金薄膜之抗氧化性及電性研究

本研究主要探討Cu(Hf)合金薄膜之自我鈍化特性，由於Cu元素較Al元素有較低的電阻率與較高的抗電致遷移的特性。因純銅無法自我鈍化且與玻璃基板的附著性差，所以在TFT-LCD製程中Cu導線的應用卻被受限制。因此本研究製備低電阻率、具有自我鈍化能力之Cu(Hf)合金薄膜，期望能取代傳統鋁金屬導線應用於TFT-LCD與半導體製程之元件。本實驗利用磁控共濺鍍法(Magnetron Co-sputtering)在康寧Eagle2000玻璃基板上製備Cu1-xHfx (x =0.62-7.93 at.% )合金薄膜，藉由改變靶材濺鍍功率以獲得不同Hf含量的合金薄膜。薄膜成分以EDS分析，並利用快速退火爐(Rapid Thermal Annealer )對薄膜進行200 - 600˚C持溫10 - 30分鐘熱處理，最後以XRD、FPP、TEM、AES 、Scotch Tape Test等分析，探討Cu(Hf)合金薄膜經熱處理前後之結構及電性變化。結果顯示，在氧氣環境下熱處理Hf會擴散至薄膜表面形成HfO2/Cu/SiO2之自我鈍化薄膜，結構分析顯現除了Cu與HfO2結晶相外並無其他介金屬化合物生成。且薄膜電阻率亦隨著Hf含量比例減少而有降低的趨勢，當Hf含量為0.62 at.% 之合金薄膜經600˚C 30分鐘熱處理後可達到2.17 μΩcm之最佳電阻率。在電性量測之結果顯示，對MOS電容器施加一外加電壓時，純銅初鍍膜之MOS電極電容器與初鍍Cu(7.93 at.% Hf)合金薄膜之MOS電極電容器漏電流皆約 10-7~10-8 A/cm2。但經600˚C 15分鐘退火後，純銅MOS電極電容器之電流漏電流值明顯上升(0.1169 A/cm2)，而Cu (7.93 at.% Hf)合金薄膜之MOS電極電容器漏電流並無增加 (1.968×10-8 A/cm2)。由結果得知添加Hf元素之Cu(Hf)電極電容器明的可靠度較佳。

關鍵字

磁控濺鍍；低電阻率；自我鈍化；銅鉿合金薄膜；附著性

並列摘要

In this study, the characteristics of Cu(Hf) alloy thin films and its applications as the materials of interconnect were investigation. Driven by copper has much lower electrical resistivity and higher electron migration (EM) resistance than that of aluminum. Hower, the copper suffers from poor adhesion with glass substrated and can not form self-passivation layer after annealed. This work aims at preparing a low resistivity, high adhesion, oxidation resistance and self-passivated Cu(Hf) alloy thin film, which will be potentially adopted as gate material on TFT-LCD and interconnection on microelectronics . Cu1-xHfx (x = 0.62-7.93 at.%) films were prepared on glass substrate by a co-sputtering method and were subsequently annealed by a RTA in a temperature range of 200°C - 600°C for 10-30 min in oxygen ambient. Self-passivated Cu thin film in the form of HfO2/Cu/SiO2 was therefore obtained because Hf diffused easily from matrix to the surface and reacted with oxygen by forming HfO2, thus oxidation of copper film can be prevented. The formation of HfO2/Cu/SiO2 improved the resistivity, adhesion to SiO2, oxidation resistance and passivative behavior of the studied film. The Cu (0.62 at.% Hf) thin film had the lowest resistivity of 2.17 μΩcm, and exhibited a superior passivated behavior among the studied films. The current-voltage measurement using metal-oxide-semiconductor (MOS) capacitor structure reveals low leakage current (10-7~10-8 A/cm2) for capacitors with as-deposited pure Cu and Cu (7.93 at.% Hf) metal gates. However, after annealing at 600˚C for 15 min, leakage current of MOS capacitors using pure copper gate exhibited a dramatic increase in leakage current, while leakage current of capacitors with Cu (7.93 at.% Hf) gate remaind at 1.968×10-8 A/cm2, indicating that the Cu (7.93 at.% Hf)/SiO2 system possessed a superior reliability to the Cu/SiO2 system.