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

由电子碰撞引起的动量交换引起的原子定向流动称为电迁移。可观测到的电迁移现象是宏观的静态现象，它会导致窄金属互连的严重可靠性问题。本工作的目的是从原子的角度理解电迁移相关现象的机理，并控制薄膜结构以提高抗电迁移引起的失效的寿命。我们对Al-2%Cu互连的电迁移进行了原位观察，发现AlCu合金沉淀物向阳极方向移动，这些沉淀物成为空洞形成的根源。我们还首次发现了直流电迁移引起的电阻的非线性振荡。它们被认为是来自空洞或空位的湮灭和形成，当然是故障早期阶段的迹象。我们研究了两种新的物理气相沉积方法：强磁场ECR溅射和持续自溅射。前者是在新观察到的电子回旋共振在2倍更高的磁场，并使高度电离溅射。我们已经成功地用这种方法将Al填充到横向沟槽中，并建立了形成高度可靠的通孔的方法。后者有效地消除任何气体污染的薄膜，因为溅射等离子体保持只有金属离子。我们证实了Ar夹杂可以忽略不计，并用这种方法在Si（100）衬底上外延了Cu（110）薄膜。因此，提出了提高薄膜互连电迁移寿命的新方法，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.