Questions and Answers
What is the primary purpose of Chemical Vapour Deposition (CVD) in semiconductor manufacturing?
Which is NOT a material that can be formed using Chemical Vapour Deposition?
During the CVD of polysilicon, which reaction occurs?
What distinct factor characterizes the deposition of Silicon Dioxide in comparison to oxidation?
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What role does silicon nitride play in semiconductor devices?
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Which metals are commonly deposited on polysilicon to form silicides?
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Study Notes
Overview of Chemical Vapour Deposition (CVD)
- CVD is a process for forming thin films through thermal decomposition or reactions of gaseous compounds.
- Can be performed under various pressures: Atmospheric Pressure (AP), Low Pressure (LP), or Vacuum.
- Variants include Plasma Enhanced CVD (PECVD), which uses plasma to enhance the deposition process.
Types of CVD Processes
- APCVD (Atmospheric Pressure CVD): Utilizes atmospheric pressure to deposit thin films.
- LPCVD (Low Pressure CVD): Operates under reduced pressure for improved film uniformity and quality.
- PECVD (Plasma Enhanced CVD): Uses plasma to lower the deposition temperature and enhance film properties.
CVD of Polysilicon
- Polysilicon is produced by decomposing Silane gas (SiH4) into silicon (Si) and hydrogen gas (H2).
- Reaction: SiH4 → Si + 2H2.
- Common application is in MOS transistors where polysilicon serves as a gate material.
CVD of Silicon Dioxide
- Functions as an insulator between metal layers and serves as a passivation layer to protect surfaces.
- Different from oxidation, which is a growth technique rather than a deposition method.
- Silicon dioxide deposition occurs at low temperatures after metallization to prevent metal melting.
- Reaction involves Silane and oxygen gas.
CVD of Silicon Nitride
- Used as a passivation layer and a barrier mask, as well as for gate dielectric applications.
- Formed by the reaction of Silane with nitrogen (N2) or ammonia (NH3) gas compounds.
CVD of Metals
- Metals such as Molybdenum (Mo), Tantalum (Ta), Titanium (Ti), and Tungsten (W) can be deposited on polysilicon.
- These metals form silicides with silicon, which significantly reduce the resistance of the polysilicon gate.
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Description
Test your knowledge on Chemical Vapour Deposition (CVD) processes. This quiz covers various methods including Atmospheric Pressure CVD, Low Pressure CVD, and Plasma Enhanced CVD, as well as the materials that can be formed like polysilicon and silicon nitride. Dive into the details of thin film formation and reactor types involved in CVD.
