用邊緣移動技術研究共晶銲錫之電遷移

Abstract

本論文報導利用邊緣移動技術來計算共晶錫鉛受電致遷移之參數。試片結構使用經圖案化後銅/鈦結構，經由迴流與拋光銲錫形成Blech結構。利用原子力顯微鏡來對通電前後體積變化做計算，可獲得平均原子飄移速度。經過通電後我們觀察到在陽極部份產生突出物，陰極部份則產生孔洞。在80度、100度與120度下施予不同電流密度，得到在80度、100度與120度的臨界電流密度分別為1.2*10^3 A/cm^2、1.8*10^3 A/cm2 及2.9*10^3 A/cm2,並求得活化能為0.34eV;D0Z*為-9.71*10^6 cm^2/sec。

In this study, we have successfully developed a technique that can precisely measure the important parameters of solder electromigration. By applying currents in the Blech specimen and by measuring the depletion volume at appropriate conditions, electromigration flux and other electromigration parameters can be obtained. We have developed a technique to fabricate solder Blech specimens, in which the depletion volume caused by electromigration can be measured precisely. Solder Blech specimens were fabricated on patterned Cu/Ti films in Si trenches. Electromigration eutectic PbSn Blech structure has been investigated. Depletion occurred at the cathode end of the Blech sample, and hillocks were observed at the anode end for most stressing conditions. By employing atomic force microscope to measure the depletion volume on the cathode end, the electromigration rate can be measured. Drift velocity was measured at the current density ranging from 9.1 x 103 to 9.7 x 104 A/cm2 at 80, 100, and 120 □C. The drift velocity increased when the applied current increased. The calculated threshold current density is 1.2*10^3 A/cm^2 at 80℃, 1.8*10^3 A/cm^2 at 100 ℃, and 2.9*10^3 A/cm^2 at 120℃, respectively. The measured activation energy was 0.34 eV. With the activation energy, the values of D0Z* was calculated to be -9.71 □ 106 cm2/sec.