2015 Theses Doctoral
Characterization of Room Temperature Recrystallization Kinetics in Electroplated Copper Thin Films
The lack of an energetic model for the seemingly spontaneous room temperature recrystallization of electroplated copper thin ﬁlms has proven to be a technological bottleneck in the optimization of copper interconnect microstructure for the microelectronics industry. The inability to either achieve large grained interconnect microstructures by simple annealing or explain them by a posteriori analyses necessitates a new approach. Synchrotron x-ray diﬀraction was utilized to obtain real-time grain size, crystallographic texture, and strain data about the recrystallization in the geometrically simpler case of blanket electroplated Cu ﬁlms. The observation of a bimodal size distribution between as- deposited and recrystallizing grains during led to the development of a theoretical framework for combining x-ray data and the canonical Johnson-Mehl-Avrami-Kolmogorov (JMAK) kinetics model. Under this framework, analysis of variations in plated Cu ﬁlm and vapor deposited underlayer structures established that ﬁlm recrystallization speed is a function of initial 111 ﬁlm texture, and that this dependency is modulated by underlayer deposition conditions and plated ﬁlm thickness. Veriﬁcation of the new x-ray analysis was performed by combined use of complementary destructive and non-destructive characterization techniques which are more commonly accessible in the industrial setting. These included cross-sectional focused ion beam milling and scanning electron microscopy (x-FIB/SEM), electron back scatter diﬀraction (EBSD), and four-point probe electrical resistivity measurements. Comparative real-time in situ x-ray and resistivity studies revealed the formation of electron percolation paths which prematurely short-circuited the latter analysis. An eﬀective resistivity model is proposedto extend the current canonical one-dimensional analysis to be compatible with multi-dimensional recrystallization. X-ray analysis of plated ﬁlms whose initial stress state had been modiﬁed by delamination or the photoresist masking of substrate stresses revealed a signiﬁcant change to the recrystallization kinetics. Complementary real-time EBSD analysis localized the initiation of recrystallization to the free surface of the ﬁlm. The combination of this with quantitative activation energy measurements was then the basis for a comprehensive theoretical energetics model.
- Treger_columbia_0054D_12833.pdf binary/octet-stream 24.1 MB Download File
- Academic Units
- Materials Science and Engineering
- Thesis Advisors
- Noyan, Ismail C.
- Ph.D., Columbia University