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Dislocation-pipe diffusion in nitride superlattices observed in direct atomic resolution

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ABSTRACT

Device failure from diffusion short circuits in microelectronic components occurs via thermally induced migration of atoms along high-diffusivity paths: dislocations, grain boundaries, and free surfaces. Even well-annealed single-grain metallic films contain dislocation densities of about 1014 m−2; hence dislocation-pipe diffusion (DPD) becomes a major contribution at working temperatures. While its theoretical concept was established already in the 1950s and its contribution is commonly measured using indirect tracer, spectroscopy, or electrical methods, no direct observation of DPD at the atomic level has been reported. We present atomically-resolved electron microscopy images of the onset and progression of diffusion along threading dislocations in sequentially annealed nitride metal/semiconductor superlattices, and show that this type of diffusion can be independent of concentration gradients in the system but governed by the reduction of strain fields in the lattice.

No MeSH data available.


Averaged diffusion spectrum in metals after (5).The diffusivity coefficient of Hf in ScN found in this study is inserted as green rectangle, and the only two other direct experimental finds of dislocation-pipe diffusion from the literature (both done on Al) are inserted for completeness2223.
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f4: Averaged diffusion spectrum in metals after (5).The diffusivity coefficient of Hf in ScN found in this study is inserted as green rectangle, and the only two other direct experimental finds of dislocation-pipe diffusion from the literature (both done on Al) are inserted for completeness2223.

Mentions: Figure 4 shows averages of typical diffusion spectra for various metals and diffusion paths after3. The diffusivity coefficient estimated from our data is inserted as green rectangle, about two orders of magnitude below the average Dd values for common metals at that T/Tm, but still 5–6 orders of magnitude above expected bulk diffusion values. The lower than average Dd is expected, since nitride films are used for that very reason as diffusion barriers. For completeness, the data from refs 22 and 23 are inserted as well. Those studies were however performed in Al and close to the melting point, which is at 933 K significantly lower than that of HfN (~3600 K) and hence cannot be directly compared to.


Dislocation-pipe diffusion in nitride superlattices observed in direct atomic resolution
Averaged diffusion spectrum in metals after (5).The diffusivity coefficient of Hf in ScN found in this study is inserted as green rectangle, and the only two other direct experimental finds of dislocation-pipe diffusion from the literature (both done on Al) are inserted for completeness2223.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382674&req=5

f4: Averaged diffusion spectrum in metals after (5).The diffusivity coefficient of Hf in ScN found in this study is inserted as green rectangle, and the only two other direct experimental finds of dislocation-pipe diffusion from the literature (both done on Al) are inserted for completeness2223.
Mentions: Figure 4 shows averages of typical diffusion spectra for various metals and diffusion paths after3. The diffusivity coefficient estimated from our data is inserted as green rectangle, about two orders of magnitude below the average Dd values for common metals at that T/Tm, but still 5–6 orders of magnitude above expected bulk diffusion values. The lower than average Dd is expected, since nitride films are used for that very reason as diffusion barriers. For completeness, the data from refs 22 and 23 are inserted as well. Those studies were however performed in Al and close to the melting point, which is at 933 K significantly lower than that of HfN (~3600 K) and hence cannot be directly compared to.

View Article: PubMed Central - PubMed

ABSTRACT

Device failure from diffusion short circuits in microelectronic components occurs via thermally induced migration of atoms along high-diffusivity paths: dislocations, grain boundaries, and free surfaces. Even well-annealed single-grain metallic films contain dislocation densities of about 1014 m−2; hence dislocation-pipe diffusion (DPD) becomes a major contribution at working temperatures. While its theoretical concept was established already in the 1950s and its contribution is commonly measured using indirect tracer, spectroscopy, or electrical methods, no direct observation of DPD at the atomic level has been reported. We present atomically-resolved electron microscopy images of the onset and progression of diffusion along threading dislocations in sequentially annealed nitride metal/semiconductor superlattices, and show that this type of diffusion can be independent of concentration gradients in the system but governed by the reduction of strain fields in the lattice.

No MeSH data available.