39) (2) What material layer was grown on single crystal silicon that was stable,
ID: 2265832 • Letter: 3
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39) (2) What material layer was grown on single crystal silicon that was stable, reproducible and controllable that led to the ability to form millions of identical components (diodes, transistors, capacitors, resistors) side-by-side? a. 40) (2) What are the two primary thin film deposition techniques used today? a. b. c. d. Evaporation and sputtering LPCVD and PECVD Oxidation and diffusion Chemical and physical vapor depositions 41) (2) HCl is added to the oxidation growth process to reduce which contaminate during growth? a. 42) (2) The threshold voltage (Vt) in a transistor is the transition voltage between and a. b. c. Accumulation and inversion Accumulation and depletion Depletion and inversion (2) Name two different advanced lithography techniques to obtain smaller feature sizes? a. b. 45) (2) The field oxides used in IC fabrication are generally grown/deposited how? (2) Polishing etches are considered what type of etchant? (2) Define the term "selectivity" with respect to etching materials. a. a.Explanation / Answer
39) Polisilicon layer denoted as PolySi.
40) Chemical and physical vapor depositions. (a) is used for depositing layers of molecules or atoms, (b) is used to deposit high quality and uniform Si nitride based films, (c) is used for intriducing impurities ie., dopants.
41) Sodium(Na)
42) Depletion and inversion
Advanced lithography techniques to obtain smaller feature sizes: X-Ray lithography(XRL) and electron beam lithography.
45) Layering - this is the first step in the growth of a field oxide. This is used as a mask for patterning.
Patterning - creates an opening in the field oxide for growing source, drain and gate oxide. It means the series of steps that create this opening in the oxide.
Layering - the field oxide is etched and then the gate oxide is grown.
Etchants can be organic or inorganic acids, alkalis, or other complex substances, in a solvent such as water, alcohol etc. Etching is used to remove unwanted depositions. Generally a mixture of phosphoric acid and acetic acid is used in VLSI.
Selectivity: It means the selection of a particular etchant over another by consdering/comparing their etch rates. It refers to the ability of the etchant to remove only the material needed for etching, while leaving the mask and substrate materials unaffected.
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