| 摘要: | 近年來，在半導體封裝領域，電鍍奈米雙晶銅因其能在不大幅影響電性的前提下去提升機械強度，使其逐漸受到重視；更有研究指出，奈米雙晶銅具有良好的熱穩定性及一定的電遷移抗性，讓雙晶銅材料在高頻高速的產品封裝領域佔有一席之地。本研究的第一部分為利用不同濃度的吉利丁添加劑製作出不同雙晶密度的電鍍奈米雙晶銅膜，進行拉伸性質研究，藉此實驗提出了柱狀雙晶結構的銅薄膜，在受到平行於基板的拉伸應力時，所發生的塑性變形過程。去雙晶區域內的柱狀雙晶結構會接續發生:聚結(coalescence)、晶粒尺寸縮小(grain-size reduction)及晶粒細化(grain refinement)等過程。而在此類雙晶薄膜在受到平行於基板的拉伸應力時，所發生的雙晶消失過程(de-twinning process)，可分為兩個主要步驟:(1)壁架(ledge)結構的產生及(2)兩個反方向的壁架移動使雙晶結構消失。也證實薄膜的強度與雙晶界密度高度相關。我們的實驗結果也顯示具有較大雙晶界密度的電鍍奈米雙晶銅膜比具有較小雙晶界密度的電鍍奈米雙晶銅膜有更大的斷裂強度。第二部分闡述超高正向應力下，具有平行於基板雙晶結構銅的變形機制及塑性變形發生後，雙晶晶界處平行於雙晶晶界的疊差是如何產生的。差排以奈米雙晶銅柱頂端不平處為差排生成處，在起始超高應力下，以觀察不到的速度，在銅柱頂端發生超快速塑性變形，不平處在受到超高應力後，成為支點不移動，持續施加應力的情況下，支點間平面受應力後，發生彈性變形，形成彎曲輪廓(bending contour)，彎曲平面應力環達到曲率極限時，由彈性變形轉為塑性變形，產生差排，塑性變形持續發生。藉由施密特定律(Schmid’s law)及雙湯普森四面體(double Thompson tetrahedron)，我們可推斷出超高正向應力下，塑性變形發生後，雙晶晶界處平行於雙晶晶界的疊差是來自於30°肖克萊部分差排(Shockley partial dislocation)在雙晶晶界上的橫滑移(cross-slip)及接續產生的階梯狀解離差排(stair-rod dislocation dissociation)、60°全差排(perfect dislocation)及90°肖克萊部分差排在雙晶晶界上的橫滑移及其穿過(transmit across)雙晶晶界時，所產生的疊差。;In recent years, electroplating nano-twinned Cu has gradually attracted a very attention in the field of the package because it can improve the mechanical properties without greatly affecting the electrical properties. Some studies also have pointed out that nano-twinned Cu has good thermal stability and certain electromigration resistance, which makes nano-twinned Cu materials having a place in the field of high-frequency and high-speed product packaging. The first part of this study is to use different concentrations of gelatin additives to produce electroplated nano-twinned Cu films with different twin boundary densities, then, conduct tensile properties research. This experiment proposes a Cu film with a columnar twin crystal structure. When the tensile stress is parallel to the substrate, processes such as coalescence, grain-size reduction, and grain refinement will occur successively. When this type of Cu film with twin structure is subjected to tensile stress parallel to the substrate, the de-twinning process that occurs can be divided into two steps: (1) the ledge formation by the engagement of the dislocations with the twin boundaries and (2) the collapse of the ledges with the opposite twin-boundaries which make the twin structure disappear. It is also confirmed that the strength of the film is highly correlated with the twin boundary density. The electroplated nano-twinned Cu film with a larger twin boundary density has greater fracture strength than the electroplated nano-twinned Cu film with a smaller twin boundary density. The second part explains the deformation mechanism of Cu with twin structure parallel to the substrate under ultra-high normal stress and how the stacking faults parallel to the twin boundary at the twin boundary occurs after the plastic deformation. The dislocation takes the protrusions on the top of the pillar as the place where the dislocation is generated. Under the initial ultra-high stress, ultra-rapid plastic deformation occurs at the top of the Cu pillar at an unobservable speed. The protrusions are subjected to ultra-high stress. After that, it becomes a fulcrum without moving, and under the condition of continuous application of stress, the plane between the fulcrums undergoes elastic deformation after being stressed, forming a bend contour. When the bending plane reaches the curvature limit, the elastic deformation turns into plastic deformation. Using Schmid′s law and double Thompson tetrahedron, we can infer that under ultra-high normal stress, the stacking faults parallel to the twin boundary come from the cross-slip of the 30° Shockley partial dislocation on the twin boundary with the subsequent stair-rod dislocation dissociation, 60° perfect dislocation, 90° Shockley partial dislocation cross-slip onto the twin boundary and its transmission across the twin boundary. |
