4 Microstructure and Mechanical Reliability Issues of TSV
73
Fig. 4.1 Variation of (a) average hardness and (b) yield strength of filler material with average
grain size of Cu. The broken line shows the best curve fit using Hall-Petch type of relationship
between hardness in a and yield strength in b and the inverse of the square root of grain size. The
data for (a) and (b) are taken from Refs. [6, 7], respectively
shown in Fig. 4.2, and hence do not display generalized polycrystalline behavior. It
has been shown that electrolytes with impurities can enhance the yield strength of
the fillers [15]. Therefore, attention should be paid to the methods used to estimate
the mechanical behavior of TSVs [8, 9]. In addition, the conventional parameter of
an average grain size may not be sufficient to characterize the grain structure of TSV
fillers. In the current materials genome initiative [10], new methods that consider
Fig. 4.2 (a) Electron back scatter diffraction (EBSD) patterns showing inverse pole figure (IPF)
maps of cross-section of Cu fillers: (i) as-deposited and (ii) after annealing at 420 °C for 20 min
followed by annealing at 300 °C for additional 15 min [6]. (b) FIB micrographs showing grain
structure of Cu filler: (i) as-deposited and (ii) after annealing at 400 °C for 1 h [13]
73
Fig. 4.1 Variation of (a) average hardness and (b) yield strength of filler material with average
grain size of Cu. The broken line shows the best curve fit using Hall-Petch type of relationship
between hardness in a and yield strength in b and the inverse of the square root of grain size. The
data for (a) and (b) are taken from Refs. [6, 7], respectively
shown in Fig. 4.2, and hence do not display generalized polycrystalline behavior. It
has been shown that electrolytes with impurities can enhance the yield strength of
the fillers [15]. Therefore, attention should be paid to the methods used to estimate
the mechanical behavior of TSVs [8, 9]. In addition, the conventional parameter of
an average grain size may not be sufficient to characterize the grain structure of TSV
fillers. In the current materials genome initiative [10], new methods that consider
Fig. 4.2 (a) Electron back scatter diffraction (EBSD) patterns showing inverse pole figure (IPF)
maps of cross-section of Cu fillers: (i) as-deposited and (ii) after annealing at 420 °C for 20 min
followed by annealing at 300 °C for additional 15 min [6]. (b) FIB micrographs showing grain
structure of Cu filler: (i) as-deposited and (ii) after annealing at 400 °C for 1 h [13]