Influence of grid and target radius and ion neutral collisions on grid-enhanced plasma source ion-implantation process

Wang, J L; Zhang, G L; Fan, S H; Yang, Wei; Yang, Sui

doi:10.1088/0022-3727/36/10/307

Cited by 11 publications

(3 citation statements)

References 22 publications

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“…By varying the external parameters in the calculation, it is found that larger gap distance, higher gas pressure, and lower negative potential can reduce the gridshadow effect, which is consistent with the corresponding experimental results. However, it should be pointed out that, such selection of parameters for mitigating the grid-shadow effect are undesirable for improving the ion impact energy [12], and will accordingly reduce the surface hardness of the processed sample [15]. Now we are revising our experimental devices to reduce the grid-shadow effect, e.g.…”

Section: Discussionmentioning

confidence: 99%

“…When a negative voltage pulse is applied on the target, positive ions within the region between the grid electrode and the inner surface can be accelerated into the target. Experimental and theoretical studies [9][10][11][12][13] have demonstrated the advantages of this new technique over other ion implantation techniques for inner surface modification of a cylindrical bore [5,7,14]. However, grid-like patterns are observed on the inner surface processed by GEPSII (see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Grid-shadow effect in grid-enhanced plasma source ion implantation

Wang

Zhang

Wang

et al. 2005

Surface and Coatings Technology

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-A grid-shadow effect is observed in grid-enhanced plasma source ion implantation, in which ions produced within the plasma region are extracted through a grid electrode and then accelerated to the inner surface of a cylindrical bore for implantation. By simulating the ion transportation behaviors from the grid electrode to the inner surface using a Monte Carlo model, we find that the grid-shadow effect results from grid blocking of the ion emission on the grid electrode, and it varies with the experimental parameters such as the gap distance between the grid electrode and the inner surface, the gas pressure, and the applied negative potential.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Grid-shadow effect in grid-enhanced plasma source ion implantation

Wang

Zhang

Wang

et al. 2005

Surface and Coatings Technology

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“…Secondly, we modified our fluid model by considering the collision effects, and investigated the effects of grid electrode radius, target radius and gas pressures on the ion dose and impact energy [51] . The calculated results can give some guidance for the selection of experimental parameters such as the gas pressure, plasma density and grid electrode radius.…”

Section: Studies On the Ion Sheath Dynamics In Inner Surface Psiimentioning

confidence: 99%

Simulation methods of ion sheath dynamics in plasma source ion implantation

Wang¹

2004

Chinese Sci Bull

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Progress of the theoretical studies on the ion sheath dynamics in plasma source ion implantation (PSII) is reviewed in this paper. Several models for simulating the ion sheath dynamics in PSII are provided. The main problem of nonuniform ion implantation on the target in PSII is discussed by analyzing some calculated results. In addition, based on the relative researches in our laboratory, some calculated results of the ion sheath dynamics in PSII for inner surface modification of a cylindrical bore are presented. Finally, new ideas and tendency for future researches on ion sheath dynamics in PSII are proposed.Keywords: plasma sheath simulation, plasma source ion implantation, fluid model, particle simulation, inner surface plasma source ion implantation.Plasma source ion implantation (PSII) has been a well-known technique to modify surface properties of materials. It has many advantages over conventional ion beam implantation, i.e. it is non-line-of-sight accessible, cost-effective and it can be easily operated. In PSII, a target is immersed in a plasma. When a series of negative high-voltage ( 10 100 kV) pulses are applied to the target, ions are extracted directly from the plasma and accelerated to the target for implantation. Since the technique was proposed by Conrad in 1986 [1,2] , many experiments have performed and shown its superiorities in improving the surface hardness, the resistance to wear and corrosion of materials [3 6] .The ion dose and impact energy are the most important factors to determine the result of PSII, and the two factors depend mainly on the dynamics of ion sheath evolution. Therefore, theoretical studies on the ion sheath dynamics emerged and have been continuously developing, giving guidance for the PSII techniques. The physical model of ion sheath forming and expanding in PSII (Fig. 1) is: When a sudden negative voltage is applied to the target, initially, in the time scale of the inverse electron plasma frequency ( pe 1 ), electrons near the target are driven away, on this time scale the ion motion is negligible so that as the electrons recede, they leave behind a region of nearly uniform ion space charge around the target, which is called the "ion-matrix sheath". Subsequently, on the time scale of the inverse ion plasma frequency ( pi 1 ), ions within the sheath are accelerated into the target as they fall through the ion-matrix sheath. This, in turn, drives the sheath-plasma edge further away, exposing new ions that are extracted. Finally, on a longer time scale, the system evolves toward a steady-state Child law sheath. Fig. 1. Schematic diagram of ion sheath evolution in PSII.Based on the above physical model, before the sheath expansion, the ion density in the sheath can be assumed uniform. Thus the sheath thickness, the electric field and potential distributions within the ion-matrix sheath can be calculated by Poisson's equation [1,8 10] . During the period of sheath propagation, the ion velocity, energy, flux, dose and incidence angle at different positions of the target...

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