Date of Award

12-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Materials Science and Engineering

Committee Member

Dr. Kathleen Richardson, Committee Co-Chair

Committee Member

Dr. Yaw Obeng, Committee Co-Chair

Committee Member

Dr. Igor Luzinov

Committee Member

Dr. Marian Kennedy

Committee Member

Dr. Fei Peng

Abstract

Copper interconnects in microelectronics have long been plagued with thermo-mechanical reliability issues. Control over the copper deposition process and resulting microstructure can dictate its material properties and reduce stresses as well as defects that form in the copper. In this thesis, pulse electrodeposition processing parameters were evaluated for their impact on the copper microstructure (grain size, texture, and twin density and stress state) through electron backscattering diffraction and wafer curvature measurements. Varying levels of constraint were also investigated for their effect on the copper microstructure to better understand the microstructures of more complex three-dimensional interconnects. Highly texture blanket copper films were deposited with various pulse frequencies and duty cycle, which was found to control grain size, orientation, and twin density. Higher twin densities were also observed in the films with lower residual stress. The findings from blanket film studies were carried over to trench deposited samples, where the influence of organic additives, typically used in the electrolytic bath to produce defect-free filling of advanced geometries, on the copper microstructure was studied. With the addition of organic additives, depositions produced finer grained structures with an increased contribution from the microstructure of the trench sidewall seed layer, especially with increasing trench aspect ratio. In addition, the increased constraint of the copper, resulted in larger stresses within the features and higher twin densities. The core of this dissertation demonstrated the ability to alter the resulting Cu microstructure through variations in pulse electrodeposition parameters.

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