Control of the (111) Orientation in Copper Interconnection Layer

Abstract

This paper describes various parameters affecting to the ͑111͒ orientation in electroplating copper conductive layers. Control of this orientation is important because resistivity, stress, adhesion strength, and electromigration resistance of copper layer are affected largely by this orientation. This orientation cannot be controlled with varying electroplating conditions but can be controlled by the orientation of the copper seed layer used as substrate. That is, the ͑111͒ orientation of electroplating copper layer is closely related with that of the seed layer. Orientation of the seed layer is determined mainly by the barrier layer. Weakly and highly ͑111͒ oriented copper layer is obtained when the seed layer is deposited on tantalum nitride and Ta barrier layers, respectively. Still higher orientation is attained in the depositing of copper layer on a TaSiN barrier layer. Agglomeration does not occur with annealing in the highly oriented copper seed layer.

Effect of TaSiN Barrier Layer Composition on Resistivity of Electroplated Copper Interconnection Layers

“…2,8 However, seed layers deposited on the more usual Ta/TaN and Ta barrier layers have been highly stressed. 2,5 Much lower stress can be obtained in seed layers deposited on TaSiN barriers. 4 Nevertheless, more detailed analysis of the deposition of lower resistivity copper layers is required.…”

“…4 Thus, barrier layers of TaN and Ta/TaN have been used extensively in conventional copper interconnection systems, although the copper layer formed on these barriers is highly stressed. 5,6 Because the copper interconnection layer must be surrounded by a thick barrier layer of Ta/TaN, for instance, Ͼ15 nm thick, a layer with a smaller net cross-sectional area has been manufactured. In practice, higher sheet resistance interconnects have been used in present very largescale integrateds ͑VLSIs͒.…”

“…It has been reported that the resistivity of electroplated copper is affected to a great extent by the properties of the seed layer and materials of the barrier layer. 5,6 Low resistivity copper layer can be electroplated on a low stress seed layer. Such a low stress seed layer can be deposited on TaSiN 4,7 or WSiN 8 barrier layers, where optimization of the composition is required.…”

High rate of copper electrodeposition from the hexafluorosilicate bath

“…Extensive studies of copper electrodeposition employing the conventional sulphate bath have shown that these metal films perform lower conductivity and higher internal stress, compared to those of metallurgical samples [16,17].…”

Effect of Stress on the Properties of Copper Lines in Cu Interconnects

“…Grain size of the electroplating Cu is determined mainly by the stress and orientation of the Cu seed layer employed for electroplating. 4 To deposit or fabricate a low resistance Cu interconnection layer, correlation of the resistivity with many other parameters must be obtained. In this paper, We describe the effect of stress and grain growth in the seed and electroplated layer on the resistivity in the interconnection layer.…”