Improved Barrier and Adhesion Properties in Sputtered TaSiN Layer for Copper Interconnects

Abstract

The barrier effect for copper diffusion and the adhesion properties of copper seed layers were studied for sputtered TaSiN layers. The diffusion depth of copper following 400°C annealing is as deep as 25 nm using conventional tantalum nitride ͑TaN͒ barrier layers. With the doping of Si in this layer to form TaSiN, the diffusion depth decreases drastically, reaching 5.0 nm for an optimum Si composition of 0.06-0.09 The stress of thin copper seed layers deposited on TaSiN is much lower than that on conventional Ta barrier layers, decreasing rapidly with increasing Si composition. There appears to be no agglomeration in the low stress copper seed layer. The highest adhesion strength is attained in a copper layer deposited on a TaSiN adhesion layer with a Si composition of 0.16. Note that the optimized Si composition is different between two layers, that is, the barrier and adhesion layers.

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

“…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. Figure 1 shows the variation of stress in the copper seed layer deposited on TaSiN barrier layers of different compositions.…”

“…Composite targets of TaSi with different Si compositions were prepared for the control of Si composition in the deposited TaSiN. 4 The nitrogen composition was varied by adjusting the Ar:N 2 gas ratio in this deposition. 30 nm thick copper seed layers were deposited on these barrier layers using radio-frequency ͑rf͒ magnetron sputtering.…”

“…3 Until now, it has been considered that the actual diffusion barrier effect is the only important factor in the barrier layer. 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.…”

“…However, much lower sheet resistances can be attained in copper lines with larger cross sections as a result of incorporating a thinner TaSiN barrier layer. 2,4 However, there has been little development work on either improved barrier layers or the deposition of low resistivity copper layers. 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.…”

Integration of perovskite oxide dielectrics into complementary metal–oxide–semiconductor capacitor structures using amorphous TaSiN as oxygen diffusion barrier

“…The lack of fast diffusion paths and high crystallization temperatures makes it suitable for application as an oxygen diffusion barrier in stacked capacitor DRAM structures with perovskite oxide materials. [9][10][11][12] …”