| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
D3, In Situ Spectroscopic Ellipsometric Analysis of Thin Silver Films Deposited Using DC Magnetron Sputtering and HiPIMS Techniques |
| Author(s) |
Lirong Sun, Neil R. Murphy, Adam R. Waite, John G. Jones, Rachel Jakubiak |
| On-Site Speaker (Planned) |
Lirong Sun |
| Abstract Scope |
Very dense, thin films of noble metals are required in many optical coating and metamaterial applications. Using DC magnetron sputtering (DCMS) the initial growth of Ag on an oxide substrate follows the Volmer-Weber model with island formation followed by percolation and eventually continuous growth (coalescence). The islands and voids can be problematic in optical coatings because of losses due to scattering and strong optical absorptions associated with plasmonic resonances [1]. Additionally, below the coalescence threshold the optical dispersion in the visible and near IR regions deviates significantly from that of bulk Ag [2]. Highly energetic deposition methods such as high power impulse magnetron sputtering (HiPIMS) decrease the coalescence threshold by improving the cohesion between the Ag film and the substrate. This can be measured in real time using in situ spectroscopic ellipsometry (SE). In situ SE is a non-intrusive and non-destructive method for obtaining film thickness and optical dispersion in real-time during film growth. This real-time analysis provides valuable information about the dynamic optical properties of each stage of film growth starting with island formation, followed by percolation and coalescence into a continuous film. With this data in hand the growth of the films can be stopped at an optimal thickness. Ag films grown on Si and glass substrates using DCMS and HiPIMS with a 2-inch diameter Ag target were studied and compared. The in situ SE data, ψ and ∆, at an incidence angle of 700 at 593 wavelengths in the range of 371-1678 nm were acquired every 16 seconds with the acquisition period synchronized with the substrate rotation period. The film thickness, the index of refraction and the extinction coefficient were determined with dynamic fittings of a Lorentz oscillator model. The film thickness as a function of deposition time was virtually monitored; thereby the coalescence threshold was detected in real time during film growth. The Ag film deposited by DCMS at 4mTorr of pressure grew linearly with deposition time above 10 nm. Below 10 nm, the surface roughness is maximized at 8.6 nm, and it dropped significantly between 8.6 to 10 nm. This indicates the coalescence threshold is at a thickness of 10 nm. The Ag thin films prepared via HiPIMS were investigated by varying process pressure, pulse duty cycle, time-average power. Monitoring with in situ SE, the HiPIMS process was optimized to grow a fully continuous film at the lower percolation threshold with low surface roughness compared to those deposited by DCMS. |
| Proceedings Inclusion? |
Undecided |