Manufacturing Processes Questions and Answers – Electrochemical Etching – 7

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This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Electrochemical Etching – 7”.

1. Morphology of μpSi and mpSi can be defined by a concrete spatial distribution.
a) True
b) False
View Answer

Answer: b
Explanation: The sponge-like morphology of μpSi and mpSi cannot be defined by a concrete spatial distribution because of the complex structure of their porous network.
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2. The resulting pore structure in pSi is intrinsically dependent on the doping level of the Si wafer.
a) True
b) False
View Answer

Answer: a
Explanation: MpSi is produced by electrochemical etching of n-type wafers. The etching of p- and n-type Si wafers with a high or moderate level of doping yields mpSi structures and μpSi structures.

3. Why the pore characteristics of the resulting pSi structures depend upon the doping type? Choose the most correct option.
a) Processing time depends on doping
b) The manufacturing process is selected on the basis of doping
c) The pore formation mechanism relies on doping
d) Atomic size of doping atom affects the final structure
View Answer

Answer: c
Explanation: The reason why the pore characteristics of the resulting pSi structures depend upon the doping type and its level of the silicon wafer is that the pore formation mechanism relies on these parameters.
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4. _____ mechanism is associated with the pore formation in μpSi structures.
a) Enhanced electric field
b) Tunnelling
c) Quantum confinement
d) Space-charge limited mechanism
View Answer

Answer: d
Explanation: The space-charge limited mechanism is associated with the pore formation in μpSi structures, which results when n-type silicon wafers are electrochemically etched in HF solutions.

5. The enhanced electric field and tunnelling mechanisms are associated with the formation of _____ structures.
a) mpSi
b) MpSi
c) μpSi
d) pSi
View Answer

Answer: a
Explanation: The enhanced electric field and tunnelling mechanisms are associated with the formation of mpSi structures when highly or moderately doped Si wafers are electrochemically etched in HF solutions.
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6. In the pore formation mechanism of MpSi, electronic holes initiate the dissolution process of silicon.
a) True
b) False
View Answer

Answer: a
Explanation: As far as the pore formation mechanism of MpSi is concerned, electronic holes initiate the dissolution process of silicon and these are minority charge carriers in n-type silicon. Therefore, the concentration of electronic holes in n-type silicon under equilibrium conditions is very low.

7. The neutral state is achieved when the concentration of electrons is equal to the concentration of electronic holes and ionized donors.
a) True
b) False
View Answer

Answer: a
Explanation: Three types of charges are present in the bulk silicon: namely, electronic holes, electrons and ionized donors. The system is a neutral state when the concentration of electrons is equal to the concentration of electronic holes and ionized donors together.
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8. For a given level of doping, the growth of MpSi in n-type silicon substrates can be controlled by_____
a) amount of electric current passed
b) current density
c) voltage drop
d) processing time
View Answer

Answer: b
Explanation: For a given level of doping, the growth of MpSi in n-type silicon substrates can be led by the current density and the illumination applied in the course of the etching process.

9. A pre-treatment by a lithographic patterning stage enables the production of ordered pore distribution.
a) True
b) False
View Answer

Answer: a
Explanation: As-produced MpSi has a random pore distribution since pores nucleate uniformly on the Si wafer surface. A pre-treatment by a lithographic patterning stage enables the production of MpSi structures with perfectly ordered pores featuring square or triangular arrangement.
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10. Among all the etching parameters, the etching current density (J) is the most critical factor.
a) True
b) False
View Answer

Answer: a
Explanation: The growth of well-defined cylindrical macropores from top to bottom in MpSi can be precisely controlled through the etching parameters (e.g. etching current density, HF concentration and its temperature, wafer doping, illumination intensity, etc.). In particular, among these parameters, the etching current density (J) is a critical factor to lead a homogeneous pore growth as the longer the pore the more effective the collection of photo-generated holes.

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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