| Focused ion beams are a new technology that has recently emerged and is widely used in the semiconductor manufacturing industry due to its ability to sputter and deposit micro and nano structures with high precision.The focused helium ion beam can be used to process finer micro and nano structures due to its small sputtering yield compared to conventional focused ion beams.The energy deposition and the low solubility of helium in the focused helium ion beam can cause amorphous damage and helium bubble damage in the substrate.The paper investigates the damage in both silicon and silicon carbide materials by both numerical modeling and experimental simulations.A helium bubble damage prediction model is constructed for silicon and silicon carbide materials to investigate the relationship between process parameters and helium bubble formation.The main points of this paper are as follows.(1)The causes of amorphization and helium bubble damage are explained based on the mechanism of interaction between ions and substrate atoms during incidence.By analyzing the energy transfer between particles during ion motion and the slowing down process of ions in the substrate,the variation law of amorphization damage is explained.The defects involved in the nucleation of helium bubbles are classified into four categories: movable defects,transition defect clusters,stable helium bubble nuclei,and intrinsic defects,based on the formation of point defects and their activity mechanism in the substrate.The types of compound defects in the nucleation evolution of helium bubbles in silicon and silicon carbide were determined.(2)Focused helium ion processing damage experiments on Si and SiC were conducted to investigate the variation of amorphization damage and helium bubble damage with incident energy and dose in both materials.The energy mainly affects the range of the helium ions,and the amorphization damage effect is more pronounced for higher energy helium ions with a wider distribution in the substrate.The increase in dose increases the amorphous damage and the helium bubble damage effect,where the amorphous damage cannot increase significantly after reaching high doses due to the limitation of the ion range,while the helium bubble damage has an increasing radius with increasing dose.In the case of helium bubble damage,the radius of the helium bubble increases with increasing dose.(3)Based on the multi-scale evolutionary mechanism of helium bubbles,a set of reaction rate equations for helium bubble nucleation in silicon and silicon carbide materials was constructed and derived.A program based on Matlab was developed to solve and visualize the concentration and radius of helium bubbles at different locations in the cross section of the substrate.The program uses the point defect distribution calculated by the Monte Carlo model as input and the ADI alternating implicit difference format as the solution of the equations.And for the aggregation effect of small helium bubbles,an aggregation mechanism is added to the model.By comparing the simulation and experimental results,the helium bubbles derived from the rate equation are consistent with the experiment in terms of size variation as well as distribution pattern.(4)The effect of energy and dose on the damage is explained by the simulation results.When comparing the simulation results for different energies and doses,it is found that an increase in energy leads to a more discrete deposition of helium ions,which results in smaller bubble sizes and lower concentrations for the same material and dose,while an increase in dose leads to an increase in the total amount of helium and vacancies,resulting in an increase in the radius and concentration of helium bubbles.In this paper,an experimental study is carried out to explain and simulate the variation of helium bubble damage with process parameters during incidence based on the energy damage mode and defect evolution mechanism of ions in solids,and the established helium bubble damage model has good accuracy. |
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