Match the following : Codes :List - I List - II (a) Lift OFF (i) Etching (b) Rant's Rule (ii) Crystal Growtd (c) Hydrofluoric acid (iii) Packaging (d) Float zone (iv) Metallisation
(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
Three of the four links are unmistakable, and they fix the fourth by elimination.
(c) Hydrofluoric acid → (i) etching. HF is the one acid that attacks silicon dioxide, converting it to soluble fluosilicic acid while leaving the underlying silicon untouched. That selectivity makes it the standard wet etchant for opening windows in an oxide mask, and it is also why buffered HF is a laboratory staple in device fabrication.
(d) Float zone → (ii) crystal growth. The float-zone method grows a silicon boule by passing a molten zone along a polycrystalline rod held vertically, with no crucible touching the melt. Because the melt never contacts a container, oxygen and other impurities stay out and the resulting crystal is the purest available — which is why float-zone silicon is used for high-voltage power devices and detectors, while cheaper Czochralski silicon serves most ICs.
(a) Lift OFF → (iv) metallisation. Lift-off is the standard way of patterning metal that is hard to etch. A resist is patterned first, the metal is deposited over everything, and dissolving the resist carries away the unwanted metal, leaving the tracks behind. Its natural place in the process flow is the metallisation step.
(b) Rent's Rule → (iii) packaging. Rent's rule is the empirical relation between the number of external pins a block needs and the number of gates it contains:
\(T=t\,g^{p}\)
with the exponent p typically 0.5 to 0.7. Since it predicts pin count, it is a packaging and interconnect law rather than a fabrication one — it tells the designer how many pins a package must provide as circuits grow.
| Item | Belongs to | Code |
|---|---|---|
| Lift off | Metallisation | (iv) |
| Rent's rule | Packaging | (iii) |
| Hydrofluoric acid | Etching | (i) |
| Float zone | Crystal growth | (ii) |
The order (iv), (iii), (i), (ii) is option 2.
Hence, the correct match is (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii).
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Choose the correct answer from the options given below:
