Computer Simulation of Ion Implantation in Crystalline Targets.

Available from UMI in association with The British Library. The aim of this work was to produce a new computer program to simulate ion implantation into crystalline targets. The model will allow the investigation of the effects of crystalline structure on the penetrating ion beam. The model was developed using the Universal potential function to obtain scattering angles and nuclear energy loss. The electronic energy loss is gained from an expression which takes into account the spatial distribution of the electrons around the nucleus. The modularity of the program design allows any regular structured material to be simulated, for example, body centred cubic, face centred cubic or diamond structures are easily set up as target structures, as are more complex structures such as polymer films. Thermal vibrations are incorporated in the model and are generated from the Debye temperature of the target material and gaussian distributed in a one thousand point array. The vibrations are uncorrelated. The option to exclude thermal vibrations is given. Provision is made for the correct treatment of head-on collisions for light and heavy ions. Multi-particle encounters are facilitated to give stability to the motion of an ion in a channel. Testing of the model is carried out by comparing its output with experimental data. These comparisons show excellent agreement for a range of ion species implanted into silicon and gallium arsenide. The model is also used to investigate lateral spread of the implantation profile and the data produced showed that lateral spread about the impact of the ion beam, is not uniform. This result has important significance for device fabrication.