Improvement of elasticity of drawn gold bonding wire by texture control

细直径为~ 20μm的金线广泛用于半导体器件的连接。由于集成电路芯片尺寸的减小，要求开发具有更高的抗拉强度和弹性等机械性能的金线。对于金单晶，已知<111>方向的杨氏模量几乎是<100>方向的杨氏模量的3倍。因此，期望通过织构控制（即制造<111>取向的金属丝）可以获得具有高弹性的~多晶金线。利用取向分布函数（ODF）研究了细金键合丝在拉丝和退火过程中的织构演变。高纯金（99.999 wt.%）的冷拔织构由强纤维组分<111>和弱纤维组分<100>组成，收缩面积小于99%。面积减少99%以上，拉丝过程中发生再结晶，导致<100>组分增加。含有微量合金元素（纯度为99.95 wt.%）的金丝冷拔织构也由强纤维成分<111>和弱纤维成分<100>组成，类似于高纯度（99.999 wt.%）的金丝。而添加微量合金元素的金丝在面积收缩率99%以上未发生再结晶，因此在面积收缩率99%以上仍保留<111>织构成分。结果表明，在高纯金丝中添加微量合金有助于抑制拉丝过程中的再结晶，从而获得高度<111>取向的金丝。

Gold wires with fine diameter of 〜20μm are widely used for bonding semiconductor devices. Due to the decrease of IC chip size, the development of gold wires with increased mechanical properties such as tensile strength and elasticity is required. For gold single crystal, it is known that Young's modulus of a crystallographic <111> direction is almost three times as much as that of a crystallographic <100> direction. It is therefore expected that ~ polycrystalline gold wires with high elasticity are available by texture control (i.e., fabrication of <111> orientated wires). In the present study, texture evolution during wire drawing and annealing of fine gold bonding wire was investigated by means of the orientation distribution function (ODF). Cold drawing texture of high-purity gold (99.999 wt.%) consisted of strong <111> and weak <100> fiber components below 99% reduction in area. Above 99% reduction in area, recrystallization occurred during wire-drawing process, resulting in increased <100> component. Cold drawing texture of gold wires with trace alloying elements (99.95 wt.% purity) also consisted of strong <111> and weak <100> fiber components similar to high-purity (99.999 wt.%) gold wires. However, for gold wires added trace alloying elements, recrystallization did not occur above 99% reduction in area, and thereby the <111> textural component retained beyond 99% reduction in area. Consequently, it is found that trace alloying addition to high-purity gold wire is useful for suppression of recrystallization during wire-drawing process and results in highly <111> orientated gold wires.