| Byeong-Ok, C., Sung-Wook, H., Jung-Hyun, R., and Sang, H. M. |
| More vertical etch profile using a Faraday cage in plasma etching. |
| Review of Scientific Instruments v.70, n.5, pp.2458-2461. (1999). |
| Abstract: Scanning electron microscope images of sidewalls obtained by plasma etching of an SiO/sub 2/ film with and without a Faraday cage have been compared. When the substrate film is etched in the Faraday cage, faceting is effectively suppressed and the etch profile becomes more vertical regardless of the process conditions. This is because the electric potential in the cage is nearly uniform and therefore distortion of the electric field at the convex corner of a microfeature is prevented. The most vertical etch profile is obtained when the cage is used in fluorocarbon plasmas, where faceting is further suppressed due to the decrease in the chemical sputtering yield and the increase in the radical/ion flux on the substrate. (9 References). |
| Online at: Link to Online Reference
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|
| Cornet, C., Kwok, D. T. K., Bilek, M. M. M., and McKenzie, D. R. |
| Numerical simulation of metal plasma-immersion ion implantation and deposition on a cone. |
| Journal of Applied Physics v.96, n.11, pp.6045-6052. (2004). |
| Abstract: A two-dimensional particle-in-cell simulation in r-z cylindrical co-ordinates is used to model metal plasma-immersion ion implantation and deposition on a cone. We show that a sharp cone mounted on a plane or stage exhibits an ion-focusing effect, such that an increased ion dose at the sides of conical features will occur during the application of high negative voltage plasma-immersion ion implantation pulses. This focusing effect is due to the shape of the equilibrium sheath and is strongly enhanced by sharper cones. The focusing effect increases for sharper cones and the ion trajectories bend more sharply. However, this deflection of the trajectories is not strong enough to direct the ions normal to the cone surface. Consequently, sharper cones exhibit a more oblique incident angle for the implanted ions. (C) 2004 American Institute of Physics |
| Online at: Link to Online Reference
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|
| Donnelly, I. J. and Watterson, P. A. |
| Ion-Matrix Sheath Structure Around Cathodes of Complex Shape. |
| Journal of Physics D-Applied Physics v.22, n.1, pp.90-93. (1989). |
| Abstract: Numerical methods have been used to find the electric potential distribution in the stationary ion sheath that initially surrounds wedge-shaped cathodes in a plasma, following the application of a large negative voltage pulse. |
| Online at: Link to Online Reference
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|
| Donolato, C. |
| Application of Green's differential equation to the analysis of ion-matrix sheaths around wedge-shaped cathodes. |
| Journal of Physics D: Applied Physics v.38, n.3, pp.397-402. (2005). |
| Abstract: A relation between the gradient of the electric field and mean curvature of equipotential surfaces (Green's differential equation) is applied to a two-dimensional free-boundary problem arising in the study of ion sheaths
around wedge-shaped cathodes. With the assumption that the equipotential lines are hyperbolae, this relation leads to a nonlinear ordinary differential equation for the potential along the bisector line of the wedge. An
approximate solution is found, which yields, in particular, the sheath width along this line as a function of the wedge angle. The resulting values are in good agreement with published results obtained by numerically solving Poisson's equation. |
| Online at: Link to Online Reference
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|
| Ensinger, W., Hochbauer, T., and Rauschenbach, B. |
| Lateral implantation homogeneity of wedge-shaped samples treated by plasma immersion ion implantation. |
| Surface and Coatings Technology v.94-95, pp.352-355. (1997). |
| Abstract: Plasma immersion ion implantation (PIII) is a rapidly developing technique for ion implantation in metallurgical and semiconductor applications. In contrast to conventional beam-line ion implantation, the treatment of three-dimensional samples does not require complicated workpiece and ion beam manipulation. However, recent results have shown that, in addition to the shape of the workpiece, treatment homogeneity is strongly dependent on process parameters such as ion density and gas pressure. Knowledge of homogeneity is of great importance for the further development of PIII. In the present paper, homogeneity measurements of a model system are discussed. Wedge-shaped silicon specimens with different angles (30 [deg] to 90 [deg]) were treated by plasma immersion ion implantation with argon ions with 45 kV high-voltage pulses. The samples were analyzed for lateral implantation concentration by Rutherford backscattering measurements. The implanted concentration, the projected range and their gradient are a strong function of the edge angle. The results show that for acute angles (30 [deg]), gradients in implantation concentration up to a factor five develop |
| Online at: Link to Online Reference
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|
| Ensinger, W., Hochbauer, T., and Rauschenbach, B. |
| Treatment uniformity of plasma immersion ion implantation studied with three-dimensional model systems. |
| Surface and Coatings Technology v.103-104, pp.218-221. (1998). |
| Abstract: Plasma immersion ion implantation is a rapidly developing technique for ion-beam treatment of materials, mainly metals and semiconductors. This technique was developed initially to circumvent the line-of-sight restrictions of conventional beam-line ion implantation. In contrast to the latter, the treatment of three-dimensional samples does not require complicated manipulation of the workpiece and ion beam. With this concept, knowledge of treatment homogeneity is of particular importance for the further development of plasma immersion ion implantation.In the present paper, homogeneity measurements of model systems are discussed. Silicon wafer segments mounted on wedge-shaped and V-shaped sample holders with different edge angles (30[deg] to 120[deg]), and on a U-shaped sample holder (trench), were treated by plasma immersion ion implantation with argon ions of -45 kV high-voltage pulses. The samples were analysed for lateral implantation concentration by Rutherford backscattering spectrometry measurements. The results show that, for wedge-shaped samples, gradients in concentration of implanted argon by a factor of up to six develop, depending on the process parameters. In the case of trenches, differences of more than an order of magnitude between the implantation concentrations of the side walls and bottom of the trench were found |
| Online at: Link to Online Reference
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|
| Hochbauer, T., Ensinger, W., Schrag, G., Hartmann, J., Stritzker, B., and Rauschenbach, B. |
| Homogeneity measurements of plasma immersion ion-implanted complex-shaped samples. |
| Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms v.127-128, pp.869-872. (1997). |
| Abstract: It is commonly accepted, that one of the favourable features of plasma immersion ion implantation in comparison to conventional beam-line ion implantation is its ability to treat non-planar samples without complicated workpiece and beam manipulation. Therefore, it is of particular interest to study the homogeneity of PIII treatment of three-dimensional bodies. In the present paper, homogeneity measurements are of PIII treated model systems are discussed. Wedge-shaped specimens (V- and D-shaped) with different angles made of silicon were treated by plasma immersion ion implantation with argon ions. The voltage pulse heights ranged between 30 and 45 kV. The samples were analysed for retained implantation dose by lateral Rutherford backscattering measurements. These show that large gradients in implantation dose develop under the chosen PIII conditions. An explanation for these gradients is a misalignment of electric field lines, crooked near the edges of samples, and ion trajectories, due to the inertia of the ions |
| Online at: Link to Online Reference
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|
| Hong, M. P. and Emmert, G. A. |
| Two-dimensional fluid simulation of expanding plasma sheaths. |
| Journal of Applied Physics v.78, n.12, pp.6967-6973. (1995). |
| Abstract: The transient sheath expansion around square and cross-shaped targets is simulated numerically with a two-dimensional fluid model. The angular distribution of the ions impinging on the target surface and the nonuniformity of the incident ion dose are calculated. The incident ion dose peaks near, but not at, the convex corner and has a minimum at the concave corner. The dip of the dose profile at the convex corner is shown to be caused by the product of a decreasing normal velocity profile and an increasing ion density profile along the target surface from the center to the corner. (C) 1995 American Institute of Physics |
| Online at: Link to Online Reference
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|
| Husein, I. F., Chan, C., and Chu, P. K. |
| Chemical structure modification of silicone surfaces by plasma immersion ion implantation. |
| Journal of Materials Science Letters v.19, n.21, pp.1883-1885. (2000). |
|
|
Electronic copy at: Link to PDF |
|
| Husein, I. F., Chan, C., Qin, S., and Chu, P. K. |
| The effect of high-dose nitrogen plasma immersion ion implantation on silicone surfaces. |
| Journal of Physics D: Applied Physics v.33, n.22, pp.2869-2874. (2000). |
| Abstract: The effect of plasma immersion ion implantation (PIII) treatment on silicone surfaces was investigated by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR-ATR), and scanning electron microscopy (SEM). Low-energy (at voltages of 4 and 8 kV) and high-fluence (8 x 10(17) cm(-2)) implantation of nitrogen was performed using an inductively coupled plasma source (ICP) at low pressure (similar to0.03 Pa). The IR absorption spectra showed a significant decomposition in the CH3, Si-CH3, and C-F groups of the silicone surface after PIII treatment. The percentage of decomposition was dependent on the implantation energy. The WS C 1s spectra of the PIII modified surfaces showed an increase in the polar carboxyl (O-C=O) groups and a decrease in the CF3 groups. PIII treatment shifted the XPS Si 2p peak of silicone to a higher binding energy (around 103.2 eV) and the N 1s peak to lower binding energy (around 398.5 eV). The modified Si 2p, N 1s, and O 1s spectra suggest the formation of SiOx phases, silicon oxynitrides, and silicon nitrides on the silicone surface after PIII treatment |
| Online at: Link to Online Reference
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|
| Kostov, K. G., Barroso, J. J., and Ueda, M. |
| Two Dimensional Computer Simulation of Plasma Immersion Ion Implantation. |
| Brazilian Journal of Physics v.34, n.4B, pp.1689-1695. (2004). |
| Abstract: The biggest advantage of plasma immersion ion implantation (PIII) is the capability of treating objects with irregular geometry without complex manipulation of the target holder. The effectiveness of this approach relies on the uniformity of the incident ion dose. Unfortunately, perfect dose uniformity is usually difficult to achieve when treating samples of complex shape. The problems arise from the non-uniform plasma density and expansion of plasma sheath. A particle-in-cell computer simulation is used to study the time-dependent evolution of the plasma sheath surrounding two-dimensional objects during process of plasma immersion ion implantation. Before starting the implantation phase, steady-state nitrogen plasma is established inside the simulation volume by using ionization of gas precursor with primary electrons. The plasma self-consistently evolves to a non-uniform density distribution, which is used as initial density distribution for the implantation phase. As a result, we can obtain a more realistic description of the plasma sheath expansion and dynamics. Ion current density on the target, average impact energy, and trajectories of the implanted ions were calculated for three geometrical shapes. Large deviations from the uniform dose distribution have been observed for targets with irregular shapes. In addition, effect of secondary electron emission has been included in our simulation and no qualitative modifications to the sheath dynamics have been noticed. However, the energetic secondary electrons change drastically the plasma net balance and also pose significant X-ray hazard. Finally, an axial magnetic field has been added to the calculations and the possibility for magnetic insulation of secondary electrons has
been proven. |
|
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|
| Kwok, D. T.-K., Chu, P., and Chung, C. |
| Ion dose uniformity for planar sample plasma immersion ion implantation. |
| IEEE Transactions on Plasma Science v.26, n.6, pp.1669-1679. (1998). |
| Abstract: In spite of recent progress on plasma immersion ion implantation (PIII) in semiconductor processing, for example, formation of silicon on insulator and shallow junctions, ion dose, and energy uniformity remains a major concern. We have recently discovered that the sample stage (chuck) design can impact ion uniformity significantly. Using a theoretical model, we have investigated three different chuck designs and conclude that insulators on the stage can alter the adjacent electric field and ion trajectories. Even though the conventional stage design incorporating a quartz shroud reduces the load on the power supply and contamination, it yields ion dose and energy nonuniformity unacceptable to the semiconductor industry. Thus, for semiconductor applications, the stage should be made of a conductor, preferably silicon or silicon coated materials and free of quartz |
|
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|
| Malik, S. M., Muller, D. E., Sridharan, K., Fetherston, R. P., Tran, N., and Conrad, J. R. |
| Distribution of Incident Ions and Retained Dose Analysis for A Wedge-Shaped Target in Plasma Source Ion-Implantation. |
| Journal of Applied Physics v.77, n.3, pp.1015-1019. (1995). |
| Abstract: A wedge-shaped target was implanted with nitrogen ions using the plasma source ion implantation process, in order to understand the effects of the target edges on the energy and fluence distribution of incident ions. Experimental measurements and analysis of retained dose on silicon samples affixed on the surface of the target, showed results consistent with those predicted by theoretical models. Higher retained dose and greater implantation depths were observed in the vicinity of the edge contained by the normal angle as compared to the edges contained by the acute angles. The target face with smaller area accumulated, on the average, higher dose compared to the face with the larger area. |
| Online at: Link to Online Reference
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|
| Paulus, M., Stals, L., Rude, U., and Rauschenbach, B. |
| Two-dimensional simulation of plasma-based ion implantation. |
| Journal of Applied Physics v.85, n.2, pp.761-766. (1999). |
| Abstract: A particle-in-cell simulation is used to study the time-dependent evolution of the potential and the electrical field surrounding two-dimensional objects during a high voltage pulse in the context of plasma immersion ion implantation. The numerical procedure is based on the solution of Poisson's equation on a grid and the determination of the movement of the particles through the grid. Ion current density, implanted concentration, average impact energy, and impact angle of the ions were calculated using this method for two geometrical shapes, a square and an L-shaped object. The nonuniformity of the sheath potential near convex and concave corners is shown. The divergence of the electrical field in the vicinity of corners leads to dramatically reduced concentration of the incident ions. The simulation also shows that a large ion flux hits the surface during the rise time of the pulse. Directly after the rise time, more than 40% of the whole concentration is implanted. Hence, the average impact energy of the ions is reduced during the rise time of the pulse. In the vicinity of corners the incident ions strike the surface under oblique angles. The interior sides of the objects are characterized by smaller average impact angles than the exterior sides. In addition, the dependence of the impact angle and the energy distribution on the pulse time is presented. The influence of the shape of the objects on the average energy of the ions turns out to be slight for both geometries. The results of the particle-in-cell simulation are in good agreement with the published measurements. |
| Online at: Link to Online Reference
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|
| Sheridan, T. E. |
| Ion focusing by an expanding, two-dimensional plasma sheath. |
| Applied Physics Letters v.68, n.14, pp.1918-1920. (1996). |
| Abstract: The temporal evolution of the collisionless, pulsed plasma sheath around a square bar is studied using a two-dimensional particle-in-cell code. It is found that the incident ion dose is peaked near to, but not on, the corner. This effect is explained physically by considering ion trajectories across the sheath, yielding an estimate for the dose in good agreement with the simulation results. The present results are compared to those from a fluid simulation [T. E. Sheridan and M. J. Alport, Appl. Phys. Lett. 64, 1783 (1994)], and it is found that the fluid simulation erroneously underestimates the ion dose near the corner of the bar. |
| Online at: Link to Online Reference
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|
| Sheridan, T. E. |
| Sheath expansion at a corner. |
| Journal of Physics D-Applied Physics v.29, n.10, pp.2725-2728. (1996). |
| Abstract: Collisionless plasma sheath expansion away from a square corner is studied using a particle-in-cell simulation. It is found that the sheath edge, ion impact angle and ion flux are essentially self-similar. This near self-similarity is due to the quasi-static expansion of a scale-invariant Child-Langmuir sheath |
| Online at: Link to Online Reference
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|
| Sheridan, T. E. |
| Effect of target size on dose uniformity in plasma-based ion implantation. |
| Journal of Applied Physics v.81, n.11, pp.7153-7157. (1997). |
| Abstract: Plasma-based ion implantation of a square bar is modeled using a particle-in-cell plasma simulation for three different size bars. When the sheath width is significantly greater than the bar width, it is found that the incident ion dose is largest at the center of the bar and decreases precipitously at the corners. When the sheath width is comparable to the bar width, the incident dose is largest near to, but not at, the corners. It may be possible to optimize dose uniformity by straddling these two regimes. (C) 1997 American Institute of Physics |
| Online at: Link to Online Reference
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|
| Sheridan, T. E. |
| Simulation of plasma-based ion implantation of a sawtooth target. |
| Surface and Coatings Technology v.93, n.2-3, pp.225-228. (1997). |
| Abstract: Plasma-based ion implantation of a two-dimensional target consisting of a periodic array of symmetric, 90 degrees, triangular sawteeth is studied using a particle-in-cell plasma simulation. The average ion flux, ion impact angle, ion impact energy and the energy-resolved dose are computed. When the sheath width is large compared to the tooth size, the sheath edge becomes planar, the ion flux is nearly uniform and ions impact the surface of the target at approximate to 45 degrees. The incident dose is greatest near the convex corner, and least in the concave corner. (C) 1997 Elsevier Science S.A |
| Online at: Link to Online Reference
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|
| Sun, Q., Gu, C. X., Ma, X. X., and Xia, L. F. |
| Treatment homogeneity and conformal analysis of plasma based ion implanted 3D target. |
| Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms v.217, n.2, pp.300-306. (2004). |
| Abstract: A prismoid-shaped target was treated by plasma based ion implantation (PBII) with nitrogen plasma, in order to study the lateral homogeneity in the near region of square corner after treatment. Auger electron spectroscopy was used to execute sputter depth profiling to obtain nitrogen depth distribution and retained dose on the silicon wafer. It showed that, in addition to process parameters of PBII such as pulse voltage, pulse width and radio frequency power, treatment homogeneity is strongly dependent on the shape and dimensions of the workpiece being treated. The ion retained dose and its gradient of distribution are a strong function of the factors mentioned above. Due to enhanced sputtering effect induced by the oblique ion impact, lower retained dose and shallower implantation depth were observed in the vicinity of the edge contained by square corner. The gradient of retained dose distribution exhibits a higher value with higher pulse voltage, lower plasma density, longer pulse width and smaller target size. Aided by the results of numerical simulation, sheath expanding tendency and ion impact mode under various conditions were discussed. Through conformal condition analysis of plasma sheath and the resulting characteristic of ion impingement, a better understanding of the treatment homogeneity can be achieved. (C) 2003 Elsevier B.V. All rights reserved |
| Online at: Link to Online Reference
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|
| Tian, X. B. and Chu, P. K. |
| Multiple ion-focusing effects in plasma immersion ion implantation. |
| Applied Physics Letters v.81, n.20, pp.3744-3746. (2002). |
| Abstract: In plasma immersion ion implantation, the sample is negatively biased and a plasma sheath forms. Ions are accelerated to the sample surface through this sheath. The electric field contours dictate the shape of the plasma sheath that wraps around corners and tends to be smoother and rounder than the surface topography, for instance, at a sharp corner. Our theoretical and experimental studies reveal ion flux focusing effects leading to lateral nonuniformity of the incident ion dose. Ion focusing occurs not only at the sample edge but also in the central region even for a planar sample (wafer). In this work, we numerically and experimentally investigate this ion focusing effect and ion dose nonuniformity. A simple geometric model is also presented in this letter to understand the mechanism. The results demonstrate that ion focusing originates from plasma sheath convergence that is time and space dependent. Consequently, multiple ion focusing may occur at different local sites when the target shape and processing parameters vary, and a small plasma sheath relative to the target is of paramount importance for uniform implantation. (C) 2002 American Institute of Physics |
| Online at: Link to Online Reference
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|
| Tian, X. B., Yang, S. Q., Huang, Y. X., Gong, C. Z., Xu, G. C., Fu, R. K. Y., and Chu, P. K. |
| Two-dimensional numerical simulation of non-uniform plasma immersion ion implantation. |
| Surface and Coatings Technology v.186, n.1-2, pp.47-52. (2004). |
| Abstract: One of the biggest advantages of plasma immersion ion implantation (PIII) is the capability of treating objects with irregular geometries without complex manipulation of target holder or beam rastering. The effectiveness of this approach depends on the uniformity of the incident ion dose. However, it is known that the lateral dose variation (non-uniformity) is less than optimal in some applications. Ion dose non-uniformity may lead to large variations in the biocompatibility for biomaterial implants. Therefore, ion dose uniformity is an issue frequently investigated since the inception of PIII. Unfortunately, perfect dose uniformity is usually difficult to achieve when treating samples with a complex shape. The problem arises from the non-uniformity of the plasma density and self-consistent expansion of the plasma sheath. Concave surfaces frequently receive a smaller ion dose compared to convex surfaces since ions in a limited volume are competing for more surfaces and are depleted more readily. An effective solution is to produce non-uniform plasmas. For example, at the concave site, a higher plasma density may be helpful to weaken the ion competition and delay the depletion time. Consequently, the ion dose uniformity can be improved. In the work described here, we conduct two-dimensional numerical simulation of PIII into a trench target with the novel notion of non-uniform plasma |
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|
| Tian, X. B., Zeng, Z. M., Zeng, X. C., Tang, B. Y., and Chu, P. K. |
| Efficacy of high-frequency, low-voltage plasma immersion ion implantation of a bar-shaped target. |
| Journal of Applied Physics v.88, n.5, pp.2221-2225. (2000). |
| Abstract: Elevated-temperature plasma immersion ion implantation (PIII) increases the surface hardness and thickness of the modified layer and is traditionally performed at a high energy (typically above 5 keV) and low current density. In this article, we report the benefits of a different approach by high-frequency, low-voltage plasma immersion ion implantation (HLPIII). Experiments and a two-dimensional theoretical simulation are conducted to demonstrate the advantages of the process on a bar-shaped sample in terms of ion dose, dose uniformity, and modified layer thickness. Simulation of the sheath dynamics illustrates that the thinner plasma sheath in HLPIII is geometrically more conformal to the target surface, and the incident ion flux is more uniform along the exposed surface when compared to the traditional high-voltage PIII process. The higher ion dose and thicker modified layer can be attributed to the higher ion current density. HLPIII is thus the preferred technique to enhance the surface properties of large and complex-shaped specimens such as a metal track. (C) 2000 American Institute of Physics. [S0021-8979(00)02717-1] |
| Online at: Link to Online Reference
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|
| Watterson, P. A. |
| Child-Langmuir sheath structure around wedge-shaped cathodes. |
| Journal of Physics D: Applied Physics v.22, n.9, pp.1300-1307. (1989). |
| Abstract: The steady state Child-Langmuir sheath around a wedge-shaped cathode immersed in a plasma is calculated numerically. The ions drawn from the plasma may be employed to sputter material from the cathode, or may implant into the cathode, depending upon the magnitude of the applied negative voltage. The ion impact rate onto the cathode reaches 2.2 times higher near a square edge and 3.6 times higher near a knife edge than the rate for planar surfaces of the cathode. However, for a knife edge the rate falls to zero at the edge. All the ions strike the cathode with the same kinetic energy, but the angle of impact is nonperpendicular near the edge, which could reduce the implantation depth and increase sputtering. |
| Online at: Link to Online Reference
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|
| Zeng, Z. M., Chu, P. K., Tian, X. B., Tang, B. Y., and Kwok, D. T. K. |
| Ion implantation into race surfaces of aerospace ball bearings in a plasma immersion configuration. |
| IEEE Transactions on Plasma Science v.28, n.2, pp.394-402. (2000). |
| Abstract: Plasma immersion ion implantation (PIII) is an effective technique to improve the surface properties of industrial components possessing an irregular shape, such as ball bearings used in the aerospace industry. The implant uniformity and efficiency along both the inner and outer races of a ball bearing assembly is investigated experimentally and theoretically. We study the sample placement as well as different PIII processing conditions. The use of a three dimensional (3-D) model to investigate the influence of the sample stage on the implantation efficiency and dose uniformity is described. Based on the experimental results, under typical PIII conditions, the dose variation along the outward-facing groove of the inner ring of the ball bearing assembly is 60%, whereas that along the inward-facing groove of the outer ring is 51%, By using a shorter pulsewidth and higher plasma density, the nonuniformity is improved to about 35%, which is acceptable to the aerospace industry, The experimental observations are in agreement with simulation results, and the improvement can be attributed to the better conformability of the plasma sheath to the race surface, Our results demonstrate the viability of PIII to enhance the surface properties of both the inner and outer rings of industrial ball bearings |
| Online at: Link to Online Reference
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|
| Zeng, Z. M., Tian, X. B., Kwok, D. T. K., Tang, B. Y., and Chu, P. K. |
| Influence of sample placement on the dose uniformity in plasma immersion ion implantation of industrial ball bearings. |
| IEEE Transactions on Plasma Science v.27, n.4, pp.1203-1209. (1999). |
| Abstract: Plasma immersion ion implantation (PIII) is an effective technique to enhance the surface properties of industrial components possessing an irregular shape. However, it is difficult to achieve uniform implantation along the groove surface of a ball bearing. In this work, we focus on the PIII treatment of the are surface of an industrial ball bearing. Three practical sample placement configurations are investigated: I) direct placement on the sample stage platen, II) placement on a copper extension with the same diameter as the bearing race, III) placement on a copper plate erected on the sample stage by means of a small metal rod, Using theoretical simulation, the implant dose uniformity along the groove surface is determined for the three orientations. Our results reveal that configuration III) yields the largest implant dose along the groove surface and the dose uniformity is worse in configuration I). Hence, in order to improve the lateral dose uniformity along the race surface, the bearing should be elevated from the sample |
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|