鎢化鈦對銅的電遷移效應之影響

Abstract

銅及，或鎢化鈦是經由直流濺鍍系統覆在矽晶片上的聚亞醯銨。測試 的金屬線採用微影曝光及掀去法(Lift-off)製作。電遷移現象經由不同的 溫度、電流密度、金屬線的幾何形狀、及氣氛下量測電阻得到。 在銅 的電遷移實驗中，在測試溫度介於190度至230度的情形下 有鎢化鈦的樣 品之活化能(1.73 電子伏特)比沒有鎢化鈦的樣品(0.77 電子伏特)高。在 銅/聚亞醯銨的系統中，適合使用鎢化鈦的電流密度的範圍，是低於2.42 MA/cm2。在電阻法經驗式中的電流密度的指數n，在銅/鎢化鈦膜系統中， n為5.41。而在銅膜系統中，n為3.58。造成這些結果的可能機制被詳細討 論。 有鎢化鈦阻絕層的樣品，不論有、無退火的製程，均有較長的生 命期。電阻法經驗式中的參數A，與金屬導線長度成反比。在944 sccm 的 連續氮氣提供，電流密度1.54 MA/cm2 及190度的測試環境下沒有觀察到 電遷移現象。 Copper with and without TiW films were deposited onto polyimide coated siliconsubstrate with D.C. sputtering. The test metal lines were fabricated with photolithography and lift- off process. The electromigration tests were done by measuring resistance at various temperatures, current densities, geometries ofmetal line, and atmosphere. Samples with TiW barrier layer to Cu electromigration has higher activation energy (1.73 eV) than those without TiW (0.77 eV) between 190-C and 230-C. Acurrent density below 2.42 MA/cm2 is suitable to use TiW barrier metal in Cu/polyimide system. The current density exponent n obtained with resistance method of Cu/TiW films is 5.41 and Cu films is 3.58. The possible mechanismsof these results are discussed in detail. Samples with TiW barrier layer and/or with post-deposition annealing exhibitlonger lifetime. The pre-exponential factor A of empirical formula is inversely proportional to the length of metallization. Electromigration was not observed when continuously blowing nitrogen at a mass flow rate 944 sccm, current density of 1.54 MA/cm2 and testing temperature of 190-C.