Engineering Questions with Answers - Multiple Choice Questions
Manufacturing Processes – Electrochemical Etching – 14
1 - Question
The etching rate is also affected by the diffusion of by-products.
a) True
b) False
View Answer
Explanation: Apart from the ratio between acid and oxidant, the etching rate is also affected by other factors such as the etchant temperature and the diffusion of by-products (e.g. SiF6-2) and etchant through the pores.
2 - Question
Bigger pores enable faster etching rates.
a) True
b) False
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Explanation: Some studies have demonstrated that bigger pores enable faster etching rates as a result of a more efficient diffusion of etchant and by-products through the pores and the interface noble metal-silicon.
3 - Question
Which of the following increases the etching rate?
a) Lower temperature
b) Stirring the etchant
c) Low concentration of the etchant
d) High concentration of the oxidant
View Answer
Explanation: More efficient diffusion rates can be achieved by stirring the etchant during the etching process. Another important factor directly related with the etching rate is the temperature of the etchant. Etch rate increases with the temperature.
4 - Question
In which temperature range the etching rate in metal-assisted etching of silicon increases?
a) 0—32 °C
b) 0—50 °C
c) 20—60 °C
d) Above 50 °C
View Answer
Explanation: Scientists have demonstrated that the etching rate of silicon nanowires produced by metal-assisted etching of silicon in HF/H2O2 and HF/AgNO3 increases with the temperature from 0 to 50 °C. Moreover, it was established a linear relationship between the silicon nanowires length and the etching time within the aforementioned range of temperature.
5 - Question
Which of the following metals are used in metal-assisted approach to etch silicon?
a) Vanadium
b) Copper
c) Zinc
d) Gold
View Answer
Explanation: As far as the different aspects associated with the noble metal is concerned, the most typical metals used to etch silicon by metal-assisted approach are silver, gold, platinum and palladium.
6 - Question
The noble metals used in metal assisted approach are deposited by thermal evaporation, electroless deposition, etc. techniques.
a) True
b) False
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Explanation: These metals can be deposited by thermal evaporation, electroless deposition, electrode position, sputtering, electron beam evaporation, focused ion beam deposition, spin-coating and self-assembly of particles, etc. methods.
7 - Question
The metal-assisted etching of pSi structures with lithographic deposition technique produces highly ordered geometric features.
a) True
b) False
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Explanation: Some of the deposition methods can be combined with lithography masks generated by micro and nanofabrication techniques. This enables the production of metal-assisted pSi structures with highly ordered geometric features.
8 - Question
The resulted pore geometry is the same for all the noble metals.
a) True
b) False
View Answer
Explanation: When isolated particles are used to produce metal-assisted pSi, the structure, geometric features and morphology of the resulting pSi are dependent on the noble metal. For instance, while Ag or Au particles yield pSi featuring straight pores.
9 - Question
Etching through Pt particles can generate straight as well as helical-like pores.
a) True
b) False
View Answer
Explanation: The pore geometry in pSi produced by etching through Pt particles can vary from well-defined straight pores, helical-like pores or curvy-like pores. Under some conditions, Pt particles move randomly in the course of the etching process, producing complex pSi structures.
10 - Question
Etching rate is different for different noble metals.
a) True
b) False
View Answer
Explanation: The etching rate varies from one noble metal to another. As an example, the etching rate achieved during the etching through Au particles is much slower than that obtained when Pt particles are used.