Engineering Questions with Answers - Multiple Choice Questions
Manufacturing Processes – Electrochemical Etching – 16
1 - Question
The configuration of the noble metal film is dependent on the deposition method used.
a) True
b) False
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Explanation: It is important to bear in mind that the morphology of the resulting noble metal films can vary with the deposition technique and the nature of the noble metal.
2 - Question
The stability of the noble metal in the etchant is dependent on its nature.
a) True
b) False
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Explanation: Regarding the stability of the noble metal in the etchant, this is highly dependent on its nature and some noble metals can be oxidised and dissolved in the course of the etching process according to the existing relationship between the electrochemical potentials of the noble metal and the oxidant.
3 - Question
Which of the following particles, leads to pores or wires with heterogeneous geometric features?
a) Ag
b) Au
c) Cu
d) Cr
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Explanation: Ag particles dissolve and re-deposit during the etching process as a result of the relatively low electrochemical potential of silver. Therefore, Ag particles can change their shape and morphology during this process, leading to pores or wires with heterogeneous geometric features and morphologies with depth.
4 - Question
Which of the following particles are used to produce pSi structures with well-defined geometric features?
a) Zn
b) Cd
c) Pd
d) Au
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Explanation: Usually, Au particles and films are preferably used to produce pSi structures with well-defined and precisely controlled geometric features and morphologies due to its stability in the etchant. For instance, Au meshes have been used to fabricate silicon wires of high aspect ratio (i.e. >200).
5 - Question
Illumination of light in metal-assisted etching of silicon affects the etching rate.
a) True
b) False
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Explanation: As far as the effect of light illumination in metal-assisted etching of silicon, this has a direct effect on the etching rate. It has been reported that the etching rates for p-type and n-type (100) silicon substrates of resistivity 1–10 Ω cm differ whether the etching process is conducted with or without illumination.
6 - Question
The etching rate of silicon wafers under light illumination is much slower than under dark conditions.
a) True
b) False
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Explanation: The etching rate of p- and n-type silicon wafers under room light illumination is about 0.05 times faster than under dark conditions. This difference becomes even higher (i.e. 150 times faster) when 20 W illumination is used.
7 - Question
The faster etch rates of the silicon wafer under light illumination is due to photo-excited electronic holes.
a) True
b) False
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Explanation: The etching rate of p- and n-type silicon wafers under room light illumination is about 0.05 times faster than under dark conditions. This effect can be explained by the fact that under illumination the number of photo-excited electronic holes can be higher than the number of electronic holes injected from the oxidant agent, thus enabling faster etching rates.
8 - Question
Metal assisted etching of silicon is dependent on the orientation of silicon atoms in the structure.
a) True
b) False
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Explanation: Actually, metal assisted etching of silicon is anisotropic and dependent on the crystallographic orientation of silicon. As an example, slanted porous silicon structures can be produced by etching (111) and (110) silicon wafers.
9 - Question
The etching of silicon atoms becomes more difficult for stronger back-bonds.
a) True
b) False
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Explanation: The back-bonds of the silicon atoms located on the surface of the substrate must be broken during the oxidation and dissolution of silicon. Therefore, the etching of silicon atoms becomes more difficult for stronger back-bonds. In that respect, it is worth noting that silicon atoms have one, two and three back-bonds in (100), (110) and (111) substrates.
10 - Question
Intrinsic properties of silicon substrate have no effect in the metal assisted etching of Si.
a) True
b) False
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Explanation: The Important parameter affecting the resulting pSi structures produced by metal-assisted etching are the different intrinsic properties of the silicon substrate, which have a direct effect on the geometric features and characteristics of the resulting pSi structures.