Achilleas Lazarides

Diagnostic characterization of ablation plasma ion implantation

Experiments are reported in which two configurations for ablation-plasma-ion-implantation (APII) are characterized by diagnostics and compared. The first configuration oriented the target parallel to the deposition substrate. This orientation yielded ion-beam-assisted deposition of thin films. A delay (>5 μs) between laser and high voltage was necessary for this geometry to avoid arcing between negatively biased substrate and target. The second experimental configuration oriented the target perpendicular to the deposition substrate, reducing arcing, even for zero/negative delay between the laser and the high voltage pulse. This orientation also reduced neutral atom, ballistic deposition on the substrate resulting in a pure ion implantation mode. Ion density measurements were made by resonant laser diagnostics and Langmuir probes, yielding total ion populations in the range of 1014. Implanted ion doses were estimated by electrical diagnostics, and materials analysis, including x-ray energy dispersive spect...

Ablation plasma ion implantation experiments: Measurement of Fe implantation into Si

Experiments have been performed demonstrating the feasibility of direct implantation of laser-ablated metal ions into a substrate. Initial experiments implanted iron ions into silicon substrates at pulsed, bias voltages up to negative 10 kV. Implantation of Fe ions into Si was confirmed by cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy. The 7.6 nm depth of damage layers below the Si surface is slightly less than predicted by code calculations for a maximum, effective ion energy of about 8 keV. The ion depth of penetration is limited by the overlying Fe film as well as the slow rise and fall of the voltage.

Ablation plasma ion implantation (APII) for deposition of metal coatings

Summary form only given, as follows. We present experimental results on a novel technique for deposition and implantation of metal coatings by means of ions generated by KrF laser ablation of metals. The pulse-biased substrate accelerates ablated ions. APII was initially demonstrated by implanting iron ions into silicon substrates at bias voltages up to negative 10 kV. Materials have been analyzed by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). Results definitively show that ion implantation has occurred, consistent with a maximum effective ion energy of about 8 keV. The lower effective energy is due to voltage droop and limited penetration of the overlying Fe film. XPS performed during an argon ion etch shows a depth profile confirming Fe implantation and deposition on the Si substrate. APII ion bombardment amorphizes the deposited film. Plasma diagnostics include: dye-laser interferometry, optical emission spectroscopy, Langmuir probe and Faraday cup for species identification as well as electron and ion densities and temperatures. Most recently, research has concentrated on ion implantation and deposition of hard coatings over softer metals, e.g., Ti over Al. Atomic force microscopy (AFM) data show that the APII deposited Ti film is smoother than the baseline laser-deposited film. A substrate bias voltage of -4 kV is adequate for smoothing to occur on Ti films over 6061 alloy Al substrates.

Analysis of materials processed by ablation plasma ion implantation

Summary form only given, as follows. Ablation plasma ion implantation (APII) utilizes laser ablation plasma plumes to implant metal ions into pulsed, negatively-biased substrates. Experiments have been performed in which plumes are ablated by a KrF excimer laser that generates 600 mJ pulses of 248 nm light of 25 ns duration. Ablation targets consist of pure iron pyramids that are rotated to spread the plume over a larger area. Substrates are silicon wafers which are biased to typical voltages of -10 kV for pulselengths of /spl sim/10 microseconds. Ion implanted films and substrates have been compared to laser deposited materials by HREM, cross-sectional TEM, XED, scratch tests and other techniques. APII results show a top Fe layer, an intermediate iron silicide layer with an underlying damage layer, which extends about 7 nm below the silicon substrate surface. These data agree with the results of the SRIM (stopping and range of ions in matter) code for an effective, maximum ion energy of 8 keV.