1. Electromigration in Semiconductor Devices
Most electromigration cases on semiconductor devices occurs on the metallic materials used to interconnect active devices.
Electromigration also occurs between metal contacts to immediate semiconductor layer.
Dopant electromigration on semiconductor materials.

2. Dopant electromigration
In semiconductor device physics, dopants are generally treated as immobile under normal operating condition.
The issue of dopant drift is especially relevant for a p-n junction under reverse bias. Applying reverse bias adds the built-in electrical potential difference across the junction.
Sufficient strong electric fields can create non-equilibrium concentration profiles of electrically active defects in semiconductors.

3. Displacement of Dopants
Classical work of Fuller and Severiens showed that Li migration in p-Si and p-Ge at ~ C and ~10V/cm (Li is donor in Si and Ge).
A p-Si wafer with a small piece of Li metal on top of it was annealed to obtain a relatively high concentration of Li in Si.
The initial location of the diffusion region in the semiconductor was determined from the location of the p-n junction.
The sample was subjected to a electric field and a new position of the p-n junction was located.

4. n-i-p & transistor structure creation
Pell’s investigation shows Li will drift in a reverse biased n-p junction.
An intrinsic semiconductor region can be produced when reverse bias voltage was applied at high temperature (Li ions becomes appreciably mobile).
Lithium distribution is also affected by the electric field of the space charge region of the n-p junction.
Transistor structure can be produced when avalanche conditions were maintained and high localized heating gives Li ion mobility eight orders of magnitude higher than at room temperature.
Li ions move towards the cathode then get redistributed. The area where the collection of ions takes place becomes n+ and the area depleted of ions transform back to p-type.

5. Effects of dopant electromigration
Dopant electromigration would produce performance degradation on semiconductor devices such as LED (ZnSe compound semiconductor).
Haase presented C-V evidence of electromigration in Li-doped epitaxial films of ZnSe where net acceptor (NA-ND, where ND is donor con concentration).
After 10V reverse bias was applied to the sample for few minutes (corresponding to an electric field of ~5x105 V/cm), the C-V profile changes significantly.
The high electric fields that occur in the depletion region of the Schottky barrier push the Li away from the surface causing it accumulate near the edge of the depletion region.
Electromigration of Li can affect the behavior of ZnSe LED during the hole injection at avalanche breakdown. The p-layer is compensated by Li which reduce the operating voltage by removing compensating Li near the interface then causes locally higher NA-ND and higher electric field . This phenomenon will produce avalanche injection at a lower voltage.

6. Effects of dopant electromigration
Theories on how dopant electromigration could affect the performance of MOSFET devices if operated above it’s datasheet rating.

7. Conclusions Electromigration also occurs on doped semiconductor layer.
Occurrence of dopant electromigaration can affect the reliability and performances of semiconductor devices.
Sufficient strong electric fields can create non-equilibrium concentration profiles of electrically active defects in semiconductors.
Dopant electromigration factors the semiconductor device miniaturization. However, electric field induced changes of local electrical properties can be a key to technologies for micro or even nanofabrication. Electric field induced doping may create sub-micrometer device structures without involving electron beam lithography.

8. References:
Dopant Electromigration in Semiconductors by David Cahen & Leonid Chernyak
Mobility of Impurity Ions in Germanium and Silicon C. S. Fuller and J. C. Severiens (Bell Telephone Laboratories, Murray Hill, New Jersey)
Lithium has been shown to migrate as a singly-charged positive ion in single crystals of both Ge and Si in temperature ranges of °C and °C, respectively. The mobility of the Li+ in crystalline Ge and Si has been measured as a function of temperature. Through the use of the Einstein relation between diffusion constant and mobility, values of the diffusion constants in cm2/sec of Li+ in Ge and Si are obtained as follows: D=25×10-4exp{( ) / RT} for Ge and D=23×10-4exp{( ) / RT} for Si, in satisfactory agreement with previously published results on the thermal diffusion of Li+. A curious reversion of conductivity type of solid solutions of Li in Ge is discussed. Copper has likewise been found to move as a positive ion in germanium in the temperature range 800°-900°C leading to diffusivities in agreement with previously published results.