Process optimization-the key to obtain highly reliable Cu interconnects

Process Technology for Copper Interconnects

“…Hence, the stress in Cu will be higher as the temperature of the capping layer deposition increases. To minimize void formation associated with confined grain growth, it is common practice in the industry to anneal the Cu after plating [134,145]. The copper plating process occurs at low temperatures (100°C), so that as-deposited Cu has a small grain size.…”

“…In order for a void to form, the strain energy release (associated with void formation) must exceed the change in interface energy (i.e., assuming the void forms at an interface) [146][147][148]. The nucleation barrier for void formation is also reduced if there are preexisting defects in the structure such as undercut from the via process [145] or poor fill during the plating process [150]. The critical stress depends on the adhesion between Cu and various barrier layers and on the modulus of the dielectric.…”

Process options for improving electromigration performance in 32nm technology and beyond

“…The common approach to improve electromigration is interface engineering [3]. Classical Cu surface cleaning approaches and oxidation removal options are not accomplishing for the needs in future technologies anymore.…”

“…For this process a standard PECVD system of the production line was used. RF power is capacitively coupled into the chamber which is plumbed to Si containing precursors like Trimethylsilane (SiH(CH) 3 ) among other gases. The advanced pretreatment sequence starts with the removal of the native Cu oxide followed by an insitu Si containing precursor treatment.…”

Effect of stress migration on electromigration for nano scale advanced interconnects

“…However, this type of voiding is much more strongly process dependent and is typically observed during early technology development. It can be suppressed by optimization of the via barrier [67], cleaning, and etch processes [68]. Thus, a much smaller void volume is required for failure, resulting in shorter lifetimes.…”