Plasma Treatment and Surface Analysis of Polyimide Films for Electroless Copper Buildup Process
Plasma Treatment and Surface Analysis of Polyimide Films for Electroless Copper Buildup Process
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用于化学镀铜沉积工艺的聚酰亚胺薄膜的等离子处理和表面分析
DOI：
10.1149/1.2006587
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发表时间：
2005
影响因子：
3.9
通讯作者：
P. Kohl
中科院分区：
文献类型：
--
作者：
D. Bhusari;H. Hayden;R. Tanikella;S. Allen;P. Kohl
本文报道了等离子体处理和化学镀铜改性后聚酰亚胺（PI）薄膜的表面化学状态和形貌的详细表征。利用nh3和Ar等离子体处理成功地实现了PI表面的形态和化学修饰，从而可以进行化学镀铜。测量了化学镀铜与PI表面的结合强度，并将其与等离子体诱导的PI表面的化学和物理修饰相关联。nh3等离子体主要通过在PI表面产生氮基团（即-N=C<）引起PI表面的化学变化。氩等离子体处理带来的主要是表面的物理变化（即表面粗化）。复合等离子体处理（Ar等离子体和nh3等离子体）结合了每种处理的理想化学和物理效果，产生具有更高粗糙度的PI表面，用于物理锚定铜和表面键合位点（氮和氧位点）。在氯化锡和氯化钯的化学镀铜表面活化步骤中，锡主要与表面的氧结合，而钯除了与表面的氮结合外，还与氯化锡结合。表面钯浓度与表面-N=C<位的丰度之间存在直接关系。这表明在nh3等离子体过程中产生的氮自由基被结合到表面，并作为钯的键合位点。在随后的化学镀铜过程中，钯的表面浓度与Cu的覆盖率有直接的关系。化学镀铜与PI的结合强度与表面改性和等离子体处理条件密切相关。首次在PI表面发现了一种特殊的键构型，可以促进钯的吸附，从而促进与Cu的共价键。讨论了表面粗糙度和化学结合对粘接强度的相对重要性。
We report here a detailed characterization of the surface chemical states and morphology of polyimide (PI) films following modifications by plasma treatment and electroless copper deposition. NH 3 and Ar plasma treatmentshave been successfully used to achieve morphological and chemical modification of the PI surface so that electroless copper plating can occur. The adhesion strength of the electroless copper to the PI surface was measured and correlated with the plasma-induced chemical and physical modifications of the PI surface. The NH 3 plasma causes primarily chemical changes to the PI surface through creation of nitrogen moieties (i.e., -N=C<) on the surface. The Ar plasma treatment brings about mainly physical changes to the surface (i.e., surface roughening). The combined-plasma treatment (Ar plasma followed by NH 3 plasma) combines the desirable chemical and physical effects of each treatment, yielding a PI surface with higher roughness for physical anchoring of the copper and surface bonding sites (nitrogen and oxygen sites). During the electroless copper surface activation step with tin chloride and palladium chloride, tin bonds mainly with the oxygen on the surface, whereas palladium reacts with tin chloride as well as with the surface nitrogen. A direct relationship has been observed between surface palladium concentration and the abundance of the -N=C< sites on the surface. This suggests that the nitrogen radicals created during the NH 3 plasma are incorporated into the surface and serve as bonding sites for the palladium. In the subsequent electroless Cu deposition, there was a direct correlation between the palladium surface concentration and Cu coverage. The adhesion strength of the electroless copper to the PI correlated well to the surface modifications and plasma treatment conditions. For the first time, a specific bonding configuration on the PI surface is shown to promote adsorption of palladium, which in turn promotes covalent bonding with Cu. The relative importance of surface roughness and chemical bonding on the adhesion strength is discussed.