IONIZED PHYSICAL VAPOR-DEPOSITION OF CU FOR HIGH-ASPECT-RATIO DAMASCENE TRENCH FILL APPLICATIONS

The ionized physical vapor deposition technique is used to fill high a spect ratio trenches with copper. This technique allows directional fi lling of embedded features? known as damascene, by sputtering metal at oms into a high density plasma. Large metal-atom ionized-Aux fractions are achievable (approximate to 85%) leading to high directionality of deposition at thr biased substrate. In this article, we report quanti tative measurements of fill directionality of Cu using an inductively coupled plasma (ICP) high density source. Copper is deposited into fai rly aggressive (depth/width less than or equal to 1.5) damascene trenc hes. Metal ion flux fractions are estimated from direct measurement of the trench step coverage and compared to simulation. Estimates of the Cu+/Ar+ density ratios are also made to understand the influence of a pplied ICP power and Cu atom density (magnetron power) on fill directi onality. It is found that at high magnetron powers (high copper atom d ensities) the plasma becomes ''copper rich,'' where the flux of copper ions exceeds that of the argon ions. At low magnetron power and high ICP power, we find the trench fill to be highly directional. As magnet ron power is increased, directionality suffers due to cooling of the p lasma by higher copper atom flux. (C) 1996 American Vacuum Society.