銅鎳奈米複合材料電遷移現象之研究

Abstract

應用於低功率電磁式微致動元件上製程最佳化之銅鎳奈米複合材料，本論文使用Blech結構並為了防止測試時材料嚴重氧化現象發生而於其上覆蓋一層1微米厚的二氧化矽來探討其電遷移現象。在溫度275 oC 測試電流密度1.19×106 A/cm2條件之下，銅鎳奈米複合材料的原子漂移速度為每小時565奈米，臨界長度為14微米，臨界值為1714 A/cm，原子擴散之活化能為0.39電子伏特。而純銅對照組在相同測試條件下相對應的值分別為每小時88奈米，20微米，2365 A/cm，1.09電子伏特。銅鎳奈米複合材料展現出比較嚴重的電遷移現象歸因於在電鍍製備此材料時，其表面呈現的粗糙輪廓導致於此材料與其上之保護氧化層接面處產生了裂縫。此裂縫會加強複合材料中銅原子的表面擴散因而惡化其電遷移現象。

The thesis investigates the electromigration behavior of Cu-Ni nanocomposite with an optimal composition for low- power electromagnetic microactuator fabrication. Blech stripes covered with a 1μm-thick PECVD oxide were designed and utilized for the behavior characterization. The drift velocity, critical length, critical product, and activation energy of the Cu-Ni nanocomposite, which are 565nm/hr, 14μm, 1714 A/cm, and 0.39eV respectively, have been measured at 275 □C and with a stress current density of 1.19×106 A/cm2. The activation energy of the Cu-Ni nanocomposite is about 0.39eV in the temperature range of 275-305 □C. In comparison with the values of Cu which are 88nm/hr, 20μm, 2365 A/cm, and 1.09eV, respectively, the poor electromigration behavior of the nanocomposite can be attributed to an as-plated rough surface morphology which will result in void formation in the interface between itself and the passivation oxide. The voids would ease the surface diffusion of Cu atoms in the composite and aggravate the electromigration phenomenon.