Investigation and control of a directional atomic flow induced by a high density electron current in an ultra fine metalic interconnection

由电子碰撞产生的动量交换引起的定向原子流动称为电迁移。可观测到的电迁移现象属于宏观统计现象，在狭窄的金属互连中造成严重的可靠性问题。本研究的目的是从原子的角度了解电迁移相关现象的机制，并控制薄膜结构以提高电迁移诱导失效的寿命。对A1-2%Cu界面进行了原位电迁移观察，发现AlCu合金析出相向阳极方向移动，这些析出相成为空穴形成的根源。我们还首次发现了由直流电迁移引起的电阻非线性振荡。它们被认为来自于湮灭和空洞或空缺的形成，当然是失败早期阶段的标志。我们研究了两种新的物理气相沉积方法；高磁场下ECR溅射，持续自溅射。前者在新观察到的电子回旋共振中工作，磁场高2倍，并能实现高电离溅射。用这种方法成功地将铝填筑在侧沟中，建立了一种形成高可靠通孔的方法。由于溅射等离子体仅由金属离子维持，后者有效地消除了薄膜中的任何气体污染。我们证实了Ar夹杂物可以忽略不计，并通过该方法获得了Si（100）衬底的外延Cu（110）薄膜。因此，提出了提高薄膜互连电迁移寿命的新方法，并对电迁移的基本认识取得了重要进展。

Directional atomic flow which is caused by a momentum exchange by eletron collision is called electromigration. Observable electromigration related phenomena are macroscopic statitical ones which causes a severe reliability problem in narrow metallic interconnections. The aims of the present work are to understand the mechanisms of the elctromigration related phenomena from atomistic point of view, and to controll thin film structures for improving life time against electromigration induced failures. We have carried out in-situ observation of electromigration of A1-2%Cu interconections, and found that AlCu alloy precipitates moved to anode direction and these precipitates becames to be origines of void formations. We also found nonlinear oscillation of the resistance induced by a direct current electromigration for the first time. They are considered to come from annihilation and formation of voids or vacancies, and certainly are sign of the early stage of the failures. We investigated two new methods of physical vapor depositions ; ECR sputtering at high magnetic field, and sustained self sputtering. The former is operated at the newly observed electron cyclotron resonance at 2 times higher magnetic field, and enables a highly ionized sputtering. We have succeeded in filling of Al into a lateral trench by this methods and established a methods to form highly reliable via holes. The latter one efficient to eliminate any gaseous contamination in a film since sputtering plasma is maintained only by metal ions. We have confilrmed Ar inclusion is negligible, and obtained epitaxial Cu (110) film of Si (100) substrate by this method. Thus, new methods for improving electromigration life time in thin film interconnections are proposed, and important progress for basic understanding of electromigration are made.