Depth control of focused ion-beam milling from a numerical model of the sputter process

Vasile, M. J.; Xie, Jushan; Nassar, Raja

doi:10.1116/1.590959

Cited by 61 publications

(46 citation statements)

References 13 publications

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“…The latter requirement is especially significant because the yield curve predicted by the Sigmund response function agrees qualitatively with that measured on many materials-at least for nongrazing incidence. 39 All of our analysis proceeds with the same methodology: the integral for S y ͑b͒ in Eq. ͑7͒ is dominated by contributions near the minimum of b , which we call ͕x min , y min ͖.…”

Section: Bradley-harper Theory Revisitedmentioning

confidence: 99%

On the stabilization of ion sputtered surfaces

2007

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The classical theory of ion beam sputtering predicts the instability of a flat surface to uniform ion irradiation at any incidence angle. We relax the assumption of the classical theory that the average surface erosion rate is determined by a Gaussian response function representing the effect of the collision cascade, and consider the surface dynamics for other physically motivated response functions. We show that although instability of flat surfaces at any beam angle results from all Gaussian and a wide class of non-Gaussian erosive response functions, there exist classes of modifications to the response that can have a dramatic effect. In contrast to the classical theory, these types of response render the flat surface linearly stable, while imperceptibly modifying the predicted sputter yield vs incidence angle. We discuss the possibility that such corrections underlie recent reports of a "window of stability" of ion-bombarded surfaces at a range of beam angles for certain ion and surface types, and describe some characteristic aspects of pattern evolution near the transition from unstable to stable dynamics. We point out that careful analysis of the transition regime may provide valuable tests for the consistency of any theory of pattern formation on ion sputtered surfaces.

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Section: Bradley-harper Theory Revisitedmentioning

confidence: 99%

On the stabilization of ion sputtered surfaces

2007

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“…The method [1][2][3] we employ involves numerical determination of the dose required per pixel to attain a user-specified shape. Of note, the method accounts for the sputter yield variation with incidence angle (Y(θ)) when solving for the required dose.…”

Section: Resultsmentioning

confidence: 99%

“…There have been few attempts at 3-dimensional ion milling or sculpting for the purpose of controlling feature shape [1][2][3][4][5]. The method [1][2][3] we employ involves numerical determination of the dose required per pixel to attain a user-specified shape.…”

Section: Resultsmentioning

confidence: 99%

Focused Ion Beam Sculpting Curved Shapes

Adams

Vasile

2005

MAM

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A focused ion beam (FIB) is used to accurately sculpt predetermined micron-scale, curved shapes in a number of solids. Using a digitally scanned ion beam system, various features are sputtered including hemispheres and sine waves having dimensions from 1-50 µm. Ion sculpting is accomplished by changing pixel dwell time within individual boustrophedonic scans. The pixel dwell times used to sculpt a given shape are determined prior to milling and account for the materialspecific, angle-dependent sputter yield, Y(θ), as well as the amount of beam overlap in adjacent pixels. A number of target materials, including C, Au and Si, are accurately sculpted using this method. For several target materials, the curved feature shape closely matches the intended shape with milled feature depths within 5% of intended values. Results and DiscussionThere have been few attempts at 3-dimensional ion milling or sculpting for the purpose of controlling feature shape [1][2][3][4][5]. The method [1-3] we employ involves numerical determination of the dose required per pixel to attain a user-specified shape. Of note, the method accounts for the sputter yield variation with incidence angle (Y(θ)) when solving for the required dose. For sculpting, an initially planar sample is fixed with the angle of ion incidence set at 0 o (normal incidence), and an area is outlined in plan view. The dose required per pixel is then partitioned according to the number of user-specified scan repeats.The angular dependence of yield is determined experimentally prior to sculpting. We have completed this determination for a number of materials and find that the yield depends on angle similar to the formulation put forth by Yamamura [6]. In general, the yield depends on the incident energy, E, and angle of incidence, θ, as Y(E,θ) = Y(E) t f exp[-Σ(t-1) ] with t = 1/cos θwhere f and Σ are parameters determined from a fit of the experimental data. Figure 1 plots the experimentally-determined yield for Si versus angle. This data was obtained by tilting a silicon specimen to different angles of incidence prior to separate mill steps. The line shown in this plot is a fit using the Yamamura formulation with f = 2.43 and Σ = 0.43. For Si the yield at 0 o (normal incidence) is measured to be 1.94 + 0.06. Additional values of yield, f and Σ are listed for C and Au in Table 1.Using the values listed in Table 1 a number of curved shaped features were ion beam sculpted. Figure 2 shows an example of a sinusoidal wave and a hemisphere sputtered into carbon. The maximum depth of these features comes close to the targeted values although consistently 10-15% 806

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“…composed of nanometer-size microfacets that form as a result of ion beam bombardment at near-grazing incidence angles. We expect that these features form as a result of a welldocumented sputter-induced morphological instability [23] and related phenomena [24]. The end view of the diamond tool is shown in Fig.…”

Section: Diamond Microtoolsmentioning

confidence: 96%

“…Previous research shows that a reactive gas can increase the material removal rate by lowering the binding energy of surface species thereby generating volatile etch products, or by changing the dynamics of the ion-generated al. 24 converts an initially planar surface into predetermined curved shapes in a single mill step. However, this procedure requires knowledge of Y(θ) when solving numerically for required pixel dwell times.…”

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Focused ion beam techniques for fabricating geometrically-complex components and devices.

Mayer¹,

Adams²,

Hodges³

et al. 2004

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We have researched several new focused ion beam (FIB) micro-fabrication techniques that offer control of feature shape and the ability to accurately define features onto nonplanar substrates. These FIB-based processes are considered useful for prototyping, reverse engineering, and small-lot manufacturing.Ion beam-based techniques have been developed for defining features in miniature, nonplanar substrates. We demonstrate helices in cylindrical substrates having diameters from 100 µm to 3 mm. Ion beam lathe processes sputter-define 10-µm wide features in cylindrical substrates and tubes. For larger substrates, we combine focused ion beam milling with ultra-precision lathe turning techniques to accurately define 25-100 µm features over many meters of path length. In several cases, we combine the feature defining capability of focused ion beam bombardment with additive techniques such as evaporation, sputter deposition and electroplating in order to build geometrically-complex, functionally-simple devices. Damascene methods that fabricate bound, metal microcoils have been developed for cylindrical substrates.Effects of focused ion milling on surface morphology are also highlighted in a study of ion-milled diamond.

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Depth control of focused ion-beam milling from a numerical model of the sputter process

Cited by 61 publications

References 13 publications

On the stabilization of ion sputtered surfaces

On the stabilization of ion sputtered surfaces

Focused Ion Beam Sculpting Curved Shapes

Focused ion beam techniques for fabricating geometrically-complex components and devices.

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