Anisotropy in the Anodic Oxidation of Silicon in KOH Solution

Philipsen, Harold; Kelly, John J.

doi:10.1021/jp052595w

Cited by 38 publications

(42 citation statements)

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“…Because of its importance in the technology of microelectromechanical systems (MEMS), anisotropic etching and anodic passivation of Si in alkaline solution have been widely studied [13][14][15]. Surprizingly, little work has been done on the electrochemistry of SiC at high pH.…”

Section: Introductionmentioning

confidence: 99%

Photoelectrochemistry of 4H–SiC in KOH solutions

Dorp

Kelly

2007

Journal of Electroanalytical Chemistry

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The photoelectrochemical oxidation of n-type 4H-SiC in KOH solution shows surprising features. While a limiting anodic photocurrent is observed at low light intensity, the semiconductor passivates at high intensity. The photocurrent corresponding to the passivation peak increases linearly with photon flux but decreases when mass transport in the system is enhanced. Characteristic current oscillations are observed. Possible reasons for these results are considered, as is the use of photoanodic etching for practical applications.

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Section: Introductionmentioning

confidence: 99%

Photoelectrochemistry of 4H–SiC in KOH solutions

Dorp

Kelly

2007

Journal of Electroanalytical Chemistry

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“…It is interesting to note that the current density required to passivate SiC is about two orders of magnitude larger than that needed for Si [18][19][20]. This difference is attributed to the presence of C in the SiC lattice [13].…”

Section: Electrochemistry Of P-type Sicmentioning

confidence: 99%

Anodic etching of SiC in alkaline solutions

Dorp

Weyher

Kelly

2007

J. Micromech. Microeng.

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The photoelectrochemistry of silicon carbide in alkaline solution was investigated with a view to wet-chemical etching applications. Anodic dissolution and passivation of the p-type semiconductor was observed in the dark; illumination with supra-bandgap light was required for oxidation of the n-type electrode. At low KOH concentrations and low light intensities, diffusion-controlled etching is observed for n-type SiC. We show that open-circuit photoetching can be used for defect revealing. Furthermore, based on the electrochemical properties of silicon carbide and silicon, we expect various material-selective etching processes to be possible.

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“…13,14,18,19,22,23 V-grooves and inverted pyramids are formed in the case of rectangular and square mask openings, respectively. 1,13,20 During the process, the silicon is etched chemically at open-circuit potential and slow-etching ͑111͒ facets * Electrochemical Society Active Member.…”

Section: Principle Of Approachmentioning

confidence: 99%

“…A detailed discussion on the mechanism of anisotropic etching and the electrochemistry of the two crystal planes can be found elsewhere. 19 By measuring the peak currents taken from voltammograms at various stages of V-groove formation we can determine the relative areas of the faces and thus the geometry of the groove; this allows us to follow the ͑100͒ etch rate. If etching is carried out at potentials positive with respect to the open-circuit value, i.e., in the anodic range, the etch rate can be determined simply by measuring the current as a function of time at that potential.…”

Section: Principle Of Approachmentioning

confidence: 99%

“…With an aligned mask V-grooves defined by ͑111͒ facets are etched in a ͑100͒ substrate. 12,14,18 Because the electrochemistry of the two faces is also strongly anisotropic, 19,20 in situ anodic current measurements can be used to determine accurately the change in geometry of the grooves as a result of etching. In a second but complementary method optical microscopy combined with a flow cell 21 is used to map the sample geometry, which also allows a continuous determination of etch rates.…”

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Exploiting Anisotropy for In Situ Measurement of Silicon Etch Rates in KOH Solution

Philipsen

Smeenk

Ligthart

et al. 2006

Electrochem. Solid-State Lett.

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Anisotropic etching of V-grooves in a masked substrate provides the basis for two simple methods for in situ measurement of etch rates of Si͑100͒. The width of the ͑100͒ facet defining the base of the groove and thus its surface area decreases at a rate which is determined by the etch rate in the ͑100͒ direction. By measuring voltammograms at regular intervals during etching we were able to monitor the change in geometry of the groove. In a complementary approach, in situ optical microscopy was used for determining etch rates in real time. An application of the method is described. Anisotropic etching of silicon is an essential step in device fabrication.1,2 Microelectromechanical systems ͑MEMS͒ and optoelectronics rely on the characteristic forms that result from the differences in etch rate of different crystallographic orientations. [3][4][5] It is therefore essential to be able to measure etch rates accurately and to detect any changes that may occur in these rates during a fabrication process. In addition, it may be necessary to develop a new etchant or to adapt an existing one, e.g., to determine the influence of an additive in a wide concentration range or to investigate the effect of temperature or of a shift in potential of the sample on the dissolution rates.Methods based on the etching of wagon-wheel patterns 6-8 or of semiconductor ͑hemi͒spheres 9-11 have the advantage of yielding dissolution rates for a whole range of orientations in a single experiment. These methods have a number of disadvantages: they are not simple, analysis of the results is cumbersome and, most importantly, the etching conditions generally differ from those used for device fabrication, e.g., sample geometry, hydrodynamics, gas evolution and galvanic interaction between facets may be important in determining etch rate and morphology. 12,13 At the other extreme, one can measure etch rates simply by masking a wafer of a given orientation and, after etching, determining the etched depth with a profilometer. In addition, examination of the cleaved sample with optical microscopy or scanning electron microscopy ͑SEM͒ can give information about etch rates of other orientations ͑via the underetching 14 ͒. Because each etch rate requires a number of separate experiments this approach is tedious, especially if one wishes to screen a wide range of experimental conditions. Glembocki and coworkers adapted this approach by using strips of silicon masked with an oxide layer containing square windows.15 By retracting the sample stepwise from the solution they were able to vary the time that windows were exposed to the etchant and were therefore able to measure a range of etch rates ͑in their case as a function of potential͒ in a single experiment. A disadvantage of this approach is that etching close to the solution/air boundary is important. Conditions near this boundary are obviously not the same as in a typical etching experiment, in particular because gas is being evolved. In addition, quenching of the etching reaction above the solution a...

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Anisotropy in the Anodic Oxidation of Silicon in KOH Solution

Cited by 38 publications

References 35 publications

Photoelectrochemistry of 4H–SiC in KOH solutions

Photoelectrochemistry of 4H–SiC in KOH solutions

Anodic etching of SiC in alkaline solutions

Exploiting Anisotropy for In Situ Measurement of Silicon Etch Rates in KOH Solution

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