10 Questions
Which type of etching is strongly isotropic and not suited for transferring patterns with sub-micron feature size?
Wet etching
In IC fabrication, which method involves sputtering particles from a sputter target in a low-pressure plasma chamber?
Physical vapor deposition
What is the main advantage of plasma enhanced chemical vapor deposition over traditional chemical vapor deposition?
Lower temperatures required
Which process is used to planarize the wafer surface by using a chemical slurry?
Chemical mechanical planarization
What is the main reason oxidation is important in IC fabrication?
To convert silicon into silico
What is the main purpose of lithography in semiconductor fabrication?
To transfer a pattern from a photomask to the wafer
How does a MOS transistor gate area get defined in the IC fabrication process?
By applying a specific pattern of photoresist
What happens to the photoresist after exposure to light in the lithography process?
It changes its physical properties and can act as an etching mask
How does etching contribute to semiconductor fabrication?
By selectively removing material to create patterns
Why is lithography considered one of the most important process steps in semiconductor fabrication?
Because it transfers patterns accurately onto the wafer
Study Notes
Semiconductor Fabrication Processes
- Hundreds of sequential process steps are required to fabricate integrated circuits (ICs) starting with an uniformly doped silicon wafer.
Lithography
- Transfers a pattern from a photomask to the surface of the wafer.
- Uses a layer of photoresist that changes its physical properties when exposed to light or another source of illumination.
- Can be developed by wet or dry etching or by conversion to volatile compounds through the exposure itself.
- Can act as an etching mask for the underlying layers.
Etching
- Removes material selectively to create patterns.
- Pattern is defined by the etching mask, which protects the parts of the material that should remain.
- Can be done using wet (chemical) or dry (physical) etching.
- Wet etching is isotropic, limits its application, and has a difficultly controlled etching time.
- Dry etching is highly anisotropic, less selective, but more capable for transferring small structures.
Deposition
- Physical vapor deposition (PVD) and chemical vapor deposition (CVD) are the two most important deposition methods.
- PVD involves accelerated gas ions sputtering particles from a sputter target in a low-pressure plasma chamber.
- CVD is a chemical reaction of a gas mixture on the substrate surface at high temperatures.
- Plasma enhanced chemical vapor deposition (PECVD) avoids high temperatures using radio frequencies.
- CVD has a better uniformity than PVD, especially in layer thickness.
Chemical Mechanical Planarization
- Used to plane the wafer surface with the help of a chemical slurry.
- Necessary for lithography due to correct pattern transfer.
- Enables indirect pattering by removing material always starting on the highest areas of the wafer surface.
Oxidation
- Converts silicon on the wafer into silicon dioxide.
- ... (rest of the text is incomplete, so no further notes are possible)
Test your knowledge on the fabrication process of Integrated Circuits (IC) including oxidation, diffusion, ion implantation, photolithography, etching, and more. This quiz covers topics such as semiconductor fabrication processes and the design of resistors in Electronics & Telecommunication.
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