[NanoIC topic] Advanced microelectronic interconnects: low-frequency noise as a tool to understand reliability.

Join imec, one of the world’s premier research centers in nanotechnology, at its headquarters in Leuven, Belgium, to study the stochastic current fluctuations within metal conductors. Understanding the link with their reliability properties is key in shaping the technologies of tomorrow.

Constant progress in lithography has enabled a steady decrease in transistor dimensions, resulting in a significant rise in integrated circuits (IC) performances. From a few transistors in 1958, ICs are now composed of several billions devices connected by kilometers of interconnects.

Today’s advanced technologies interconnect widths are around 20 nm or less. Even very low operating currents lead to current densities which are significantly above 10⁶ A/cm². These high current densities make interconnects very vulnerable to electromigration. Electromigration is the movement of atoms under the influence of an electric current. The constant impact of electrons on metal ions produces an exchange of momentum, ultimately leading to the displacement of atoms and the creation of voids. Electromigration reliability is classically tested using constant current stresses at elevated temperatures on packaged interconnects. Traditionally, these tests are very long and destructive.

Recently, imec proved that a link exists between the stochastic fluctuation of the current (low-frequency noise, see Fig. 1) in interconnects and their electromigration behavior [1]. The goal of this internship is to use this method to compare different metallization schemes for copper and advanced metal interconnects. The study should lead to the following achievements:

• By comparing different metallization schemes using various liners and capping materials, the contribution from each interface in the degradation mechanism will be deduced. Ultimately it will allow us to select the most reliable process.
• Using our new measurement setup, measurements at higher temperatures will be carried, and will allow us to study higher activation energies.
  
   
  
  The following activities are foreseen:

• Deep understanding of the link between the physics of electromigration and the low-frequency noise in metals.

• Data will be collected on a wide range of copper metallization schemes using our advanced low-frequency noise tester.

• Data preparation and data analyses will be performed by the student.

• Perform package level electromigration stresses to compare LFN and EM activation energies.