Vacancy-type defects in electroplated Cu films probed by using a monoenergetic positron beam

Abstract

Positron annihilation was used to probe vacancy-type defects in electroplated Cu films. Doppler broadening spectra of the annihilation radiation for Cu films deposited on samples with a Ta(20 nm)/SiO2(100 nm)/Si structure were measured with a monoenergetic positron beam. For an as-deposited Cu film, the line-shape parameter S measured 20 days after deposition was larger than that measured 1 day after deposition. The observed increase in the value of S was attributed to grain growth at room temperature and the corresponding increase in the fraction of positrons trapped by vacancy clusters in the grains. In isochronal annealing experiments, the value of S for an electroplated Cu film increased for annealing below 200 °C, suggesting agglomeration of vacancy-type defects (vacancy clusters). A decrease in the S value was observed for annealing above 300 °C, and this was attributed mainly to the decrease in the concentration of vacancy clusters. The annealing stages of the defects in electroplated Cu were found to agree with those for irradiated pure Cu.

Reduction of annealed-induced wafer defects in dual-damascene copper interconnects

“…The temperature at wafer edges is higher than at their center since they are exposed to the high temperature of the furnace wall. The edges will lose heat faster than the center during the cooling process [6,7]. Due to the non-uniform distribution of the wafer surface temperature during heating or cooling temperature transients in furnace annealing, the temperature ramp rates of a furnace are limited by the onset of plastic deformation of silicon wafers: dislocations will be induced if the yield strength of silicon is exceeded [7].…”

“…Annealing enlarges the grain size and increases the conductivity of the Cu where the grains span the full width of the line in a columnar structure [7][8][9].…”

“…Other possibility of embedded particles is a core defect in the barrier or seed layer prior to the ECP process. Previous study shows that surface particles (dielectric or metal) on top of the seed will be lifted up by the plated Cu layer and will remain on top after the copper electrochemical plating process [6,7]. If the core defect is smaller than 1 lm, the embedded defect appears dome-shaped with a particle sticking out of the top and if the core defects are bigger than 1 lm the defect takes up the appearance of the core defect.…”

A Study of Difference in Reflow Characteristics Between Electroplated and Sputtered Cu in a Dual-Damascene Fabrication Process for Silicon Semiconductor Devices

“…This result indicates that Cu films of 750 nm or 5000 nm thickness may not be very different in terms of microstructure and defect type. [39][40][41] …”

Frozen-in vacancies in PVD-Cu films with improved high-pressure reflowability studied using a slow positron beam

“…The value of S for the annihilation of positrons trapped by vacancies is larger than that for positrons annihilated from the interstitial sites. Recent positron annihilation spectroscopy studies have suggested that ECD-Cu films have a larger amount of vacancy clusters than PVD-Cu films [2][3][4]. In this paper, we investigate lattice defects in a PVD-CuSb dilute alloy film compared to a PVD-pure-Cu film by measuring the Doppler broadening of the annihilation radiation using a slow positron beam.…”