Co Liner Impact on Microstructure of Cu Interconnects

Abstract

The microstructure of Cu interconnects fabricated with Ta and Co liner materials had been examined by transmission electron microscopy and correlated to the electrical characteristics. Cu lines of 40 nm width were fabricated on 300 mm Si wafers by conventional CMOS backend processing. Electrical measurements performed immediately after fabrication of these Cu lines showed similar electrical resistance for Co and Ta liners. However, a 2.5-hour anneal at 375°C led to 5% more resistance reduction for Cu lines with the Ta liner than with the Co liner. Microstructure analyses showed that Cu lines with the Ta liner had 24% coherent Σ3 grain boundaries while lines with the Co liner yielded only 6% of coherent grain boundaries. In addition, Cu with Ta liner had a stronger 〈111〉 texture along the line width direction. However, the overall grain size distribution was similar between Ta and Co liners. These results suggest Co liner has some impact on Cu microstructures, which may be a root cause for the relatively higher line resistance.

Control of the Cu morphology on Ru-passivated and Ru-doped TaN surfaces – promoting growth of 2D conducting copper for CMOS interconnects

“…In this area, studies of potential liner materials are carried out in conjunction with a barrier material, whether known or novel, or in testing of a potential combined barrier and liner material. [7,15,34,16,[27][28][29][30][31][32][33] In experimental work, the primary characteristics of a potential liner for Cu deposition include adhesion of Cu to the liner, [15,29,32,34] wettability of Cu, [7,15,30,32] resistivity [27][28][29][30][31][32] and electromigration reliability. [31,33] Adhesion is studied through a simple tape exfoliation test: if the metal and liner remain adhered, then the adhesion is deemed strong enough for typical manufacturing conditions.…”

Atomic Layer Deposition of Cobalt Using H2-, N2-, and NH3-Based Plasmas: On the Role of the Co-reactant

“… 32 First, Co has been suggested as a viable candidate as the liner for Cu interconnects because Co can be thinner than the conventional Ta liner, which leaves more space for Cu. 33 , 34 Moreover, Co is also being investigated for the replacement of Cu or W in small-dimension interconnects in the front-end of line. 35 , 36 It is therefore valuable to select Co ALD as a model system for studying the influence of the co-reactant.…”

“…Co is a ferromagnetic transition metal used in, for instance, magnetoresistive random-access memory and CoSi 2 contacts. − Currently, Co mostly receives much attention for applications in interconnect technology, in order to reduce the resistance–capacitance delay in state-of-the-art devices . First, Co has been suggested as a viable candidate as the liner for Cu interconnects because Co can be thinner than the conventional Ta liner, which leaves more space for Cu. , Moreover, Co is also being investigated for the replacement of Cu or W in small-dimension interconnects in the front-end of line. , It is therefore valuable to select Co ALD as a model system for studying the influence of the co-reactant. A wide range of precursors and co-reactants have been investigated for the ALD of Co, as shown in Table .…”

Control of Cu morphology on Ru-passivated and Ru-doped TaN Surfaces – promoting growth of 2D conducting copper for CMOS interconnects

“…In this area, studies of potential liner materials are carried out in conjunction with a barrier material, either known or novel, or in testing of a potential combined barrier and liner material. 7,15,16,[27][28][29][30][31][32][33][34] In experimental work, the primary characteristics of a potential liner for Cu deposition include adhesion of Cu to the liner, 15,29,32,34 wettability of Cu, 7,15,30,32 resistivity [27][28][29][30][31][32] and electromigration reliability. 31,33 Adhesion is studied through a simple tape exfoliation test: if the metal and liner remain adhered, then the adhesion is deemed strong enough under typical manufacturing conditions.…”