Mechanism And Experimental Study Of Copper Plating On TSV With High Aspect Ratio Under The Action Of Single Inhibitor

As one of the core technologies of 3 D integration,through silicon via(TSV)provides a high-density vertical interconnectivity solution for miniaturization and high-performance integration.At present,TSV manufacturing technology is still not mature enough,especially in the TSV copper plating filling link,there are problems such as complex additive system,low large depth and width ratio TSV filling rate and process optimization difficulties.A simulation model of TSV with a single inhibitor was carried out with 3:1,6:1 and10:1 at different current densities using a single inhibitor PEG8000.In addition,the process improvement assisted by the optimized physical external field solves the problem of a large number of copper bumps on the wafer surface after electroplating.The main research work and findings are as follows:1.The finite element model of TSV(200 m: 20 m)based on COMSOL software and the simulation was verified.The characteristics of the clamp,"v type",equal thickness,and bottom up were explained by analyzing the inhibitor concentration,inhibitor coverage,cathode current density distribution,and copper ion concentration.Simsimulation results show that the concentration of inhibitor can affect the growth pattern of copper deposition in the blind hole.The filling morphology was obtained with PEG8000 blind wells.2.The effect of a single inhibitor PEG8000 on three blind TSV holes(3:1,6:1,10:1)was investigated,and appropriate concentrations were selected for bottom-up filling.The study found that when the TSV blind hole is 6:1 and 10:1,and PEG concentration is 0.05g/L,6:1TSV blind holes can be filled in current density of 0.3ASD-3ASD and 10:1TSV blind holes within 0.3ASD-1.0ASD.By testing the CV curve of different concentrations of PEG,the hysteresis current is the largest at PEG concentrations of 0.01 g / L and 0.05 g / L,and TSV copper deposition can achieve the bottom-up filling mode,which matches the results of filling experiments.3.We explored the effect of the physical external field on the realization of TSV,and the effects of temperature,ultrasonic vibration and forced convection on TSV were investigated.It was found that low temperature affects the additive diffusion and copper deposition rate,Will extend the plating time,At a high temperature of 40℃,the diffusion rate of copper ions in the plating solution is faster,and the inhibitor consumption cannot completely inhibit the copper deposition in the hole with "V" filling growth;it reveals the effect of ultrasonic cavitation effect on the diffusion layer filled by TSV and promoting the diffusion of reaction particles;Forced convection cannot promote the diffusion of reactive particles in the TSV,Failure to effectively improve the electroplating process,However,high-speed mixing can reduce the defect size of the TSV blind hole.4.In view of the wafer surface copper bulge problem after copper plating under a single inhibitor PEG,the rectifier TU,2M5 S and PN were respectively selected to solve the surface copper bulge problem.It was found that when PEG concentration was 0.05 g / L,TU added 0.05 g / L,the appropriate concentration of 2M5 S was 0.005 g / L,and the appropriate concentration of PN was 0.04 g / L.By studying the mechanism of levelfier by electrochemical test,the mechanism of PEG8000 used with TU and TSV filling by PN.