Manufacturing Processes Questions and Answers – Electrochemical Etching – 17

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This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Electrochemical Etching – 17”.

1. The etching rate in p-type silicon is faster than that of n-type silicon.
a) True
b) False
View Answer

Answer: a
Explanation: As far as the doping type is concerned, the etching rate in n-type silicon is faster than that of p-type silicon for (100) and (111) crystallographic orientations with the same resistivity (i.e. 7–13 Ω cm).
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2. The morphology of silicon nanowires produced by metal-assisted etching of silicon changes with the doping level.
a) True
b) False
View Answer

Answer: a
Explanation: The etching rate is not the only parameter affected by the type of doping. It has been reported that the morphology of silicon nanowires produced by metal-assisted etching of silicon changes with the doping level of the wafer as well and they can present rough surface or contain mpSi or μpSi structures on the side walls with increasing doping level.

3. In highly doped silicon wafers the diffusion of electronic holes occurs from _____
a) noble-metal to silicon
b) noble-metal silicon interface to bulk silicon
c) silicon to noble-metal
d) there is no electron hole transfer
View Answer

Answer: b
Explanation: In highly doped silicon wafers the diffusion of electronic holes occurs from the
interface noble metal-silicon to the bulk silicon substrate, which would result in the etching of the side walls, producing mpSi or μpSi structures.
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4. Lithographic techniques can produce silicon wafers with well-defined geometric features.
a) True
b) False
View Answer

Answer: a
Explanation: Porous Si structures with precisely controlled and exquisitely defined morphology and geometric features can be produced when the surface of the silicon wafer is patterned by lithographic techniques prior to the etching step.

5. Among all the lithographic techniques, interference lithography, nano-spheres lithography give better results.
a) True
b) False
View Answer

Answer: a
Explanation: Some lithographic methods have demonstrated outstanding results when combined with metal-assisted etching. The most representative ones are interference lithography, nano-porous anodic alumina masks and nano-spheres lithography.
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6. IL provides excellent definition of features at nanometric scale.
a) True
b) False
View Answer

Answer: a
Explanation: Interference lithography (IL) is a top-down nanofabrication technique with high throughput and scalability for large surface areas used in the production of nanostructures. IL provides excellent definition of features at nanometric scale. Usually, an IL pattern is generated by two coherent laser beams and subsequently transferred to a film of photoresist covering the substrate.

7. IL can be combined with metal-assisted etching to produce _____ Choose the correct one.
a) silicon bars
b) porous silicon
c) porous silicon sheets
d) silicon nanowires
View Answer

Answer: d
Explanation: IL can be combined with metal-assisted etching to produce silicon nanowires. Scientists used this approach to produce silicon nanowires by metal-assisted etching. In this study, first, silicon substrates were coated by a layer of photoresist, which was cured and exposed to IL. This process resulted in perfectly ordered arrays of silicon nanowires.
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8. Silicon wires with square and rectangular can be produced by IL technique.
a) True
b) False
View Answer

Answer: a
Explanation: The geometric features and arrangement of these arrays of silicon wires can be accurately designed by modifying the IL patterns and the feature size and its shape. Therefore, silicon wires with square, rectangular and circular cross-sections can be produced by this approach.

9. To etch the surface of silicon wafers at specific positions by metal-assisted etching, nano-porous anodic alumina (NAA) mask technique is used.
a) True
b) False
View Answer

Answer: a
Explanation: Another approach used to etch the surface of silicon wafers at specific positions by metal-assisted etching is the use of nanoporous anodic alumina (NAA) masks. Self-ordered NAA is basically a nanoporous matrix based on alumina (aluminium oxide–Al2O3) that features close-packed arrays of hexagonally arranged cells, at the centre of which a cylindrical nanopore grows perpendicularly to the underlying aluminium substrate.
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10. NAA is produced by electrochemical anodization of _____
a) silicon
b) aluminium
c) noble-metals
d) carbon
View Answer

Answer: b
Explanation: NAA is produced by electrochemical anodization of aluminium, which is typically performed in acid electrolytes based on aqueous solutions of sulphuric (H2SO4), oxalic (H2C2O4) or phosphoric acids (H3PO4).

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter