Electrochemical and Simulative Studies of Trench Filling Mechanisms in the Copper Damascene Electroplating Process

Abstract

The role of additives in copper electroplating baths in the damascene process has been investigated. We proposed a bottom-up filling model and confirmed it by comparing the experimental and simulation results. Janus Green B and Basic Blue 3 which absorb on the copper surface and suppress copper deposition were examined for additive use to improve filling capability. Damascene copper grew uniformly in the bath that contained Basic Blue 3. But it grew preferentially from the bottom of the trench for Janus Green B. Addition of Janus Green B produced a continuous concentration gradient in the sub-micron trench when the additive's diffusion rate and consumption rate on the copper surface were well balanced. We estimated filling profiles from numerical simulation using parameters that were determined by an electrochemical method. These profiles agreed well with the experimental results.

Electrochemical Deposition Process for ULSI Interconnection Devices

“…Lee and Park [61] calculated the strain energy caused by PEG incorporation by assuming that PEG is segregated at the grain boundary, and they concluded that the stress exerted by incorporated PEG on Cu atoms in the deposit is a significant factor of self-annealing. This result corresponds to the finding reported by Haba et al [71] that JGB is consumed during electrodepositon. To further investigate the effect of incorporation of additives on self-annealing, carbon microanalysis of the Cu electrodeposits was performed with the combustion-infrared absorption method.…”

Effects of Additives on Copper Electrodeposition in Submicrometer Trenches

“…Effect of JGB.-Haba et al 8 investigated the effect of JGB in the damascene copper electrodeposition without adding SPS. According to their report, the addition of JGB without SPS also achieves bottom-up filling when there is a suitable concentration gradient of JGB generated in a trench from the balance between the diffusion rate and the consumption rate of JGB.…”

“…In contrast to the effect of SPS ͑described in the preceding section͒, JGB is reported to be consumed on the copper surface during the copper deposition. 8 Thus, within the trenches, where the supply of additives from the bulk of the solution is retarded as compared with the outside of the trenches, the consumption of JGB should lead to a decrease in JGB concentration. Although the inhibition became greater at higher concentrations of JGB, not only the overfill phenomenon but also the bottom-up growth was inhibited at high concentrations of JGB.…”

“…JGB is regarded to serve as a leveling agent, flattening these bumps of copper deposits on the surface, 3,4 or to influence the filling properties. 2,8 However, the behavior of JGB, particularly its interaction with other additives, is not well understood.…”

Filling a Narrow and High Aspect-Ratio Trench with Electro-Cu Plating

“…2,3) A Cu filling process using electroplating is therefore needed to produce low-resistance, highly reliable Cu interconnects. Electroplating in comparison with electroless plating can provide higher deposition rate as well as electroplating solutions for copper deposition are more stable and easier to control.…”