Michigan Ion Beam Laboratory - Capabilities

The Laboratory provides a wide range of capabilities for both surface modification and analysis. The 1.7 MV Tandetron accelerator is capable of implantation at energies above 0.5 MeV and to a maximum energy that depends on the ion charge state. A wide variety of ions can be produced by a Torvis type, a duoplasmatron or a sputter ion source. Currents of up to 75 µA of H + and several µA of metal ions are routinely employed. The implantation end station operates at pressures in the 10 ^-9 to 10 ^-10 Torr range and samples can be either heated or cooled during irradiation. The 200 kV implanter can produce over 20 different ions at energies from 5 to 200 keV. Its end station has stages for implantation at high temperatures down to liquid nitrogen temperature at pressures of 10 ^-6 to 10 ^-7 Torr. The ion beam assisted deposition (IBAD) system can produce films or coatings of many materials by electron beam evaporation with simultaneous bombardment by a low energy ion beam in ultra high vacuum. Deposition rates up to 2 nm/s are possible and ion fluxes equal to the vapor flux can be achieved. Metals, semiconductors and ceramics can be deposited at temperatures ranging from -100°C to 1000°C in thicknesses up to 10 microns.

Ion beam analysis

• Rutherford backscattering spectrometry is used to determine the composition profile of the surface to depths of up to one micron and with a resolution of better than 10 nm. The technique provides a determination of the surface composition vs. depth profile and the number of atoms per unit area in the target.
• Ion channeling is a variant of RBS which utilizes the crystallographic nature of the target for the purpose of determining the lattice location of species and the quality of the crystal. Helium ions, accelerated along open channels in selected crystallographic directions return information on the location of interstitial atoms (solutes or impurities), the amount of damage or imperfections in the crystal, and the thickness of an amorphous layer.
• Nuclear reaction analysis is highly sensitive to small quantities of light elements which are difficult to "see" using RBS. The product of a nuclear reaction between the incoming ion and the target atom  is used to quantify the impurity level in the substrate or film. Very small concentrations of elements, in the parts per million range, can be detected with this technique.
• Elastic recoil detection,He ions are directed toward a target at a glancing angle, scattering H atoms out of the surface layer. This technique is used to determine the concentration of hydrogen in the surface of the target and is excellent for detecting hydrogen in metal films or the surface hydrogen content of polymers.

Ion Irradiation and Ion Implantation

• Main Capabilities
  ion implantation, ion beam mixing, radiation damage
• Ions from gases and sputtered materials 
  Both the Tandem accelerator and the new Ion Implanter have the capability of producing a variety of ion beams. Some the beams produced in the Tandem are: H, He, D, O, Ar, Ni. The Tandem is equipped with a Torvis type source and a Duoplasmatron and a Sputtering source that could be used interchangeably on the same beamline
  The ion implanter can (theoretically) produce beams with any element in the Periodic Table. It is equipped with a very versatile source from Danfisyk - model 921, that can produce beams from gasses, vapors and solids
  
• Wide range for ion energy
  The accelerator can operate for energies between .5 and 3.4 MV for H beams and much higher if double ionized beams are used. The Implanter operates in the 10-400 KV energy range
• Ion current range
  In the Tandem in excess of 70 microA for protons coulp be put on the targets;
  For surface analysis more than 200 nanoA for He could be generated. In the implanter currents in excess of 200 microA could be achieve with an Ar beam, and more than 25 microA for most of the other beams.
• Target chamber vacuum
  All the chambers (Tandem and Implanter) achieve a vacuum better than 10 ^-8 Torr 
• Sample temperature control
  Ion implanter: -196°C to 800°C 
  Tandem: room temperature to 1300⁰C.
• Sample Handling
  Ion Implanter: wafer holder capable of loading five 4 inch wafers or four 6 inch wafers.
  Tandem: rapid interchange device, two irradiation stages available for samples switching, and a sample holder that allows higher flexibility in sample orientation.

Ion Beam Assisted Deposition

Characteristics:


• Ion type: inert, nitrogen, oxygen mix 
• Ion energy range: 100-1200 eV 
• Ion current range: 100 mA 
• Electron beam guns: 10 and 15 cc capacity 
• Deposition rate: 2.0 nm/s 
• Target chamber vacuum: 10 ^-10 Torr 
• Sample manipulation: tilt, rotate 
• Sample temperature control: -196°C to 1000°C 
• Deposition area: 10 cm ²

Additional facilities in the laboratory provide capabilities for a number of experiments:

• Vacuum thermal treatment of implanted samples or films at temperatures up to 1100°C at 1 x 10 ^-8 Torr.
• Determination of surface roughness (with nm level resolution) of implanted samples or films made by IBAD. Thickness of films made by deposition can also be determined which, combined with the area-atom density provided by RBS, can be used to determine the bulk density of films.
• Vacuum deposition of films without an ion beam. 
• Determination of the residual stress in substrates onto which deposits have been made or which have been ion implanted.
• Hardness measurements can be performed with one of the recent additions to the lab: a Buehler Hardnes Indenter.