Wafer redeposition impact on etch rate uniformity in IPVD system

Summary form only given. The ionized PVD technique is used for barrier and seed layer metallization in advanced IC wafers. It provides good sidewall and bottom coverage in via and trench structures, and it is promising to extend performance up to sub-mum technology. To control deposition and etching rates at substrate during liner and seed deposition process and provide optimal conditions for good coverage of the high aspect features an RF bias power is applied at substrate electrode. However, at increased pressures some of the sputtered material will be scattered back. Generally, it is accepted that during etching processes, some of the removed (etched) material returns to the surface of the substrate in the form of re-deposition. The ionized PVD is realized in pressure range from several mtorr to 90 mtorr. At very low pressures (<5 mT), this re-deposited amount has negligible impact on process performance and can be discounted. At pressures greater than 5 mT, the amount of re-deposition to the substrate can be significant and affect actual feature coverage. When substrate feature sizes are very small, the impact of re-deposition to the substrate can be obscure and feature etching performance unrealized. The re-deposited material to the substrate can have ionization properties very different from the original deposited material. To investigate the effect we developed a technique to isolate the redeposition from the actual etch rate performance to understand the impact of re-deposition on 60-200 nm features. The process pressure and table bias power were examined in wide range to investigate a re-deposition impact on etch uniformity. We develop a model to simulate this effect, and evaluated the re-deposition effect quantitatively at given process conditions