Improved sputter-depth profiles using two ion guns

Sykes, D. E.; Hall, D. D.; Thurstans, R.E.; Walls, John M.

doi:10.1016/0378-5963(80)90122-1

Cited by 49 publications

(7 citation statements)

References 11 publications

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“…Although continuous specimen rotation during milling is a common technique to produce flat specimen surfaces (Sykes, 1980; Zalar, 1985, 1986; Shapuur, 1992), its application for FIB milling seems impossible. FIB‐prepared areas are always small – tens of micrometres in diameter or less.…”

Section: Discussionmentioning

confidence: 99%

“…The use of two ion guns at opposing angles of incidence reduces uneven milling in Auger electron spectrometry depth profiling (Cirlin et al , 1990). Also continuous specimen rotation in Auger electron spectrometry (Zalar, 1985, 1986) and in secondary ion mass spectrometry (Sykes, 1980) often reduces loss of depth resolution caused by beam‐induced surface roughening. Ion polishing at glancing incidence is another method to produce very smooth surfaces, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Uniform ion beam milling of a non‐flat surface at off‐normal incidence and four azimuths

Alkemade

Docter

Kutchoukov

2007

Journal of Microscopy

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Summary Atom removal from surfaces via bombardment by ion beams –ion beam sputtering or ion milling– is a widely employed technique to form geometric structures in materials. In this work we present and test a new method to achieving uniform material removal from an irregular surface. The method is based on ion milling at off‐normal incidence under four consecutive perpendicular azimuthal specimen orientations. Mathematical analysis shows that uniform ion milling of an uneven surface is achieved at the polar angle of incidence θ where the quantity has its maximum [Y(θ) is the number of removed atoms per incident ion]. The four‐azimuth milling procedure is tested successfully for a 30 keV Ga+ beam on a suspended but wrinkled Si3N4/Au bilayer foil and on truncated Si pyramids with slopes up to 40°. Despite the variations in local surface orientations, uniform milling is achieved at a polar incidence angle of 45° and four consecutive azimuths of 0°, 90°, 180° and 270°.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Uniform ion beam milling of a non‐flat surface at off‐normal incidence and four azimuths

Alkemade

Docter

Kutchoukov

2007

Journal of Microscopy

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“…Rotating the sample bombarded by a beam not normally incident onto the sample surface leads to a more uniform erosion by averaging over different bombardment directions. For the same reason the use of two ion guns has led to improvements (181). In some cases reduction of surface roughness has been reported if the ion energy is decreased (185).…”

Section: Initial Sample Roughness--any Original Surface Roughnessmentioning

confidence: 97%

“…A number of experimental studies on thin sandwich and multilayer films have shown how the depth resolution depends on the roughness of the substrate (118,179,180). This effect is strongly enhanced during depth profiling of porous structures like A1 oxides (155,181). Remedies.--A number of precautions and measures can be taken to reduce surface roughness and thereby increase depth resolution.…”

Section: Initial Sample Roughness--any Original Surface Roughnessmentioning

confidence: 99%

Sputter Depth Profiling of Microelectronic Structures

Zinner

1983

J. Electrochem. Soc.

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Reviewed are the principles and applications of sputter depth profiling for the analysis of semiconductor and microelectronic materials. Various techniques are based on sputter removal whereby either the sputtered species (in SIMS, SCANIIR) or the remaining surface (AES, XPS, ISS) are investigated. In spite of its increasing importance, there are many problems associated with sputter etching. After a general survey of the principles, a detailed discussion is devoted to the many effects which can distort sputter depth profiles and limit depth resolution. These effects can be caused by instrumental factors (nonuniformity of erosion, beam impurities, vacuum contaminants) and the sample composition or can be due to the analysis method used (information depth, matrix effects, detection limit, sample consumption). Most important are the effects caused by the sputtering ion beam itself. Among these are notably preferential sputtering, atomic mixing, surface roughness as a result of the sputter process, sample charging, surface transport, and chemical reduction. The review of applications concentrates on the measurement of the distribution of dopants and impurities in semiconductors, on the study of insulating films (in particular the Si/SiO~ interface and the oxidation of GaAs), and on the metallization problem in Si and GaAs technology.The ever-increasing miniaturization of electronic devices in VLSIC technology (1) places new demands on analytical techniques for their characterization (2, 3). Of special interest is the measurement of elemental distributions, in particular the measurement of dopant distributions in the semiconductor substrate (4, 5) and the analysis of diffusive and reactive processes between metal, semiconductor, and dielectric films (6, 7) which are the basic elements of microelectronic structures. The analytical requirements for measurement techniques include good spatial resolution as well as elemental sensitivity and specificity. Although there are interesting questions to be asked with respect to lateral dimensions, because of the planar structure of most microelectronic devices, methods for the measurement of elemental concentrations as a function of depth are of special importance. An example for the requirements for the depth resolution of such methods is given in Fig. 1 which shows calculated depth distributions of dopants in base and camel collector of a monolithic hot electron transistor (MHET) with an extremely shallow barrier raising implant.An overview of methods for the measurement of depth profiles is given in Table I. The so-called nondestructive techniques are so named n~t because they necessarily leave the sample undamaged, but because the sample surface does not have to be removed in order to obtain information about the inside. The sample interior is rather probed with penetrating ion or electron beams whereby the depth information is obtained via the energy loss experienced by the particles while traversing the sample. Rutherford backscattering spectroscopy (RBS) is based on the ...

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“…A major advance in sputter-depth profiling was the discovery of the tremendous improvement in-depth resolution and the reduction of bombardment-induced topography [15]. This led to the development of sample rotation [16] during sputter-depth profiling.…”

Section: Profile Distortion: Interdiffusion Surface Roughening and Cmentioning

confidence: 99%

Ultra-high depth resolution SIMS for the interface analysis of complex low-dimensional structures

Chakraborty

2008

Nuclear Instruments and Methods in Physics Research Section B:

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Improved sputter-depth profiles using two ion guns

Cited by 49 publications

References 11 publications

Uniform ion beam milling of a non‐flat surface at off‐normal incidence and four azimuths

Uniform ion beam milling of a non‐flat surface at off‐normal incidence and four azimuths

Sputter Depth Profiling of Microelectronic Structures

Ultra-high depth resolution SIMS for the interface analysis of complex low-dimensional structures

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