Low Temperature Copper Deposition by PE-ALD
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1195-B12-05
Low Temperature Copper Deposition by PE-ALD Jiajun Mao1, Eric Eisenbraun1, Vincent Omarjee2, Clement Lansalot2 and Christian Dussarrat2 College of Nanoscale Science and Engineering, the University at Albany, Albany, New York, USA. 2 American Air Liquide, Delaware Research and Technology Center, 200 GBC Drive, Newark, Delaware, USA. 1
ABSTRACT With the continuing scaling in device sizes, sputtered copper is not expected to achieve the conformality and surface coverage requirements to be an effective seed layer for electrochemical deposition in sub-32nm features. Additionally, the metallization demands of high aspect ratio TSVs in 3D-architectures pose similar challenges. In this work, a manufacturable low temperature Cu PE-ALD process has been developed employing a novel O and F-free precursor. The ALD process conditions are correlated with key film properties, including deposition rate, composition, step coverage, and resistivity. Additionally, the influence of precursor substituents on the deposition rate and preliminary integration performance are discussed. INTRODUCTION Copper-based interconnects are widely used for high performance integrated circuits. This approach employs an electroplated Cu layer grown on top of a Cu seeding layer, traditionally deposited by sputtering. This seed layer, in turn, is deposited on a diffusion barrier/liner stack, which is also sputter-deposited. The use of sputtered Cu seed layers has proven to be a robust, reliable technique for interconnects in high performance chips down to the 45-nm technology node.[1,2] However, as allowable seed layer thicknesses decrease to below 10 nm inside damascene structures, the conformality achievable by PVD-based film deposition can become a limiting factor in extendibility of the technology.[3,4,5] Likewise, while approaches such as atomic layer deposition are under consideration for emerging interconnect applications, the intrinsic tendency for Cu to agglomerate even at moderate deposition temperatures is a major challenge to the use of these techniques at very small layer thicknesses.[6] As such, the development of low temperature ALD-based processes for the deposition of copper is of interest for applications in nanoscaled electronics, in addition to other key application drivers such as integration with thermally fragile polymeric substrates. Plasma-based processes hold potential for reducing deposition temperatures owing to the plasma providing strongly reactive species to assist in the ALD half reaction.[7] In particular, the reduction of the Cu metal centers in metalorganic precursors can be assisted by the presence of a strong reducing agent, such as plasma-activated hydrogen species. This paper describes the use of a novel Cu ALD precursor for low-temperature plasma-enhanced ALD (PEALD) process development. EXPERIMENT PEALD process development was carried out on a modified Tokyo Electron Limited (TEL) PhoenixTM 200-mm wafer capable CVD cluster tool. This system, which includes dual
warm-wall, vertical flow processing cham
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