Based on the bulk free energy density and the degenerate mobility constructed by the
quartic double-well potential function, a phase field model is established to
simulate the evolution of inclusions in interconnects due to interface diffusion
in an electric field. The corresponding phase field governing equations are
derived and the reliability of the program is proved by the agreement
between the numerical simulation results and the theoretical analysis of the
inclusion. The evolution of elliptical inclusions under different electric fields
, different aspect ratios
, and different electric
conductivity ratios
is calculated using the mesh adaptation finite element method. The results show that the
drift velocity of the circular inclusion is proportional to the electric field and inversely
proportional to the electric conductivity ratio. There exist critical values of the electric field
, the aspect ratio
and the electric
conductivity ratio
.
When
,
or
,
the elliptical inclusions will split into several small inclusions. When
,
or
, the
elliptical inclusions will drift along the direction of the electric field as a relatively
stable shape. The smaller the electric conductivity ratio of the inclusions
, the greater the
electric field
or
the aspect ratio
,
the easier it is for the elliptical inclusions to split. Moreover, the time required for
splitting increases with increasing the electric conductivity ratio or the aspect ratio,
and decreases with increasing the electric field. In addition, the interconnect line with
two inclusions is more complex, and the inclusions will split into more small ones
under the high electric field strength, and the phenomenon of multiple merging and
multiple splitting will occur.
Keywords
phase field method, electromigration, interface diffusion,
finite element method, inclusion evolution