In this paper, we discuss the use of low frequency (up to 300 MHz) radio waves (RF) to detect and characterize electrical defects present in the dielectrics of emerging integrated circuit devices. As an illustration, the technique is used to monitor the impact of thermal cycling on the RF signal characteristics (S-parameters, such as S11 and S21) of electrically active defects in three dimensional (3D) interconnects. The observed changes in the electrical characteristics of the interconnects were traced to changes in the chemistry of the isolation dielectric used in the through silicon via (TSV) construction; specifically to the conversion of chemical intermediates such as non-bridging silanol (Si-OH) to bridging siloxane (Si-O-Si). We suggest that these "chemical defects" inherent in the 'as-manufactured' products may be responsible for some of the unexplained early reliability failures observed in TSV enabled 3D devices. This low frequency RF technique could be optimized to complement, and in some cases compete favorably with, other thin film metrology techniques, such as ellipsometry and Fourier transform infrared spectroscopy (FTIR), for mass production environments.
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Helpful discussions with Dr. Martin Greene and Dr. Christina Hacker are acknowledged with sincere thanks. This work was supported in part by the National Institute of Standards and Technology (NIST) under grant 70NANB15H021. The manuscript was written through contributions of all authors.