Ion Implantation and Ion Beam Analysis

Ion Implantation and Ion Beam Analysis

Ion Implantation

With more than twenty years experience in the field of ion implantation we offer a very wide range of services. Now acknowledged as a European Centre of Excellence, the Central Facility was originally formed in 1978 by the then Science Research Council. The Facility's primary task was to support research in the U.K. investigating applications of ion beams to semiconductor processing. Since that time the S.E.R.C. has awarded over 100 full grants to users of the Facility.

(Right) 0.2mA beam of argon being deflected into the beam line. Doubly charged and neutral beams are faintly visible. Flourescence was obtained by a deliberately poor vacuum.

Current research includes ion beam synthesis of compounds, control of implantation profiles by multiple ion implants and ion beam mixing of quantum wells for the fabrication of opto-electronic devices. We were the first to use rapid thermal annealing for dopant activation in ion implanted GaAs, and have also been closely involved with the development of SIMOX material, a oxide produced by implanting oxygen into silicon. Our new 2MV implanter will support growing interest in deep device structures in both silicon and III-V technology.

Processing

Rapid Thermal Annealing was developed at Surrey in the mid seventies and forms a basis for thermal treatment of samples after implantation. A newly installed R.T.A. furnace also capable of 1300 C for 6 hours can be seen. Such systems are complemented by more conventional flow furnaces and encapsulation systems for use with III-V materials. A PECVD rig for depositing silicon nitride encapsulants can be seen.

Multi-target sputtering (DC or RF) and evaporation systems are available for the deposition of thin films, with ellipsometry and Talystep available for thickness measurements.

Electrical and optical equipment is available to measure Hall effect, CV, IV and photoluminescence spectra at temperatures from 4K to 500K. Stripping Hall effect and CV are also available to provide depth resolved carrier concentration and mobility profiles, with a four point probe wafer mapper available for assessing process uniformity.

To provide the Facility for either selective area implantation or pilot device fabrication, photolithography and wet and dry processing are available in house, for dimensions down to one micron. Probe stations for testing completed devices are also available.

Ion Beam Analysis

Rutherford backscattering is a powerful method of depth profiling of sub-micron films. High energy light ion beams are used. The information is in the energy of particles scattered in backward direction. The required dose is quite small and does little damage to most samples. With channelling the beam can be aligned on a single crystal to give a depth profile of disorder and strain.

The example shown is of a metal bilayer being investigated for use as an ohmic contact resistant to high temperatures. 1.5MeV He+ RBS data taking 5 mins to collect after annealing at 350 C. Box shows unannealed structure.

Various related techniques can often be used simultaneously with RBS. Trace element analysis is available by detecting the characteristic X-rays. Good lateral resolution down to 0.01 mm is obtainable with the microbeam. Light elements can often be detected with nuclear reactions, and hydrogen can be detected in a forward scattering geometry.



Elemental depth profile calculated from the raw data above using the data reduction program SQUEAKIE.

Use Ion Beam Analysis to charaterise your thin films.

Simulation of Ion Implantation

Many computer simulation packages are available for the calculation of ion implantation effects, from implantation range profiles to full cascade calculations. Different calculation techniques can be employed. Analytical calculations are used in SUSPRE and Monte Carlo trajectory simulations in TRIM and CRYSTAL. Many body calculations, using full many body potentials, are used in Molecular Dynamics programs to study low energy implantation.



Monte Carlo cascade simulation of 11 separated ion impacts for 150 keV Arsenic implantation into a silicon substrate. Different colours represent different recoil generations. The edge of the box is 250nm.



A full Molecular Dynamics simulation of a 200 eV copper ion cascade in a copper target. The cascade is shown at different times as the energy is dissipated through the target. Colours represent increasing particle energies - white, red, green, blue.

Details of Accelerator Facilities Available

Implantation

There are three implanters giving range of currents, energies and ions:

Doubly charged species are often available giving implantation energies up to 4 MV with reduced beam current.

Very flexible sample handling, including whole wafers, as available at various implantation temperatures.



Ion Beam Analysis

There is a 2 MV Van de Graaff accelerator with several beam lines and various techniques available often simultaneously:

Processing

Dielectric/metals deposition, annealing including RTP, optical and electrical characterisation, lithography, wet & dry etching.


C.Jeynes@ee.surrey.ac.uk - Facility Liason
B.Sealy@ee.surrey.ac.uk - Research group leader
30th May, 1995