Silicon Wafers and Properties

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Questions and Answers

What is the first step in the semiconductor wafer fabrication process?

Slicing

Polishing

Ingot Growth

Converting sand to silicon (correct)

Which material is commonly used in the production of semiconductor wafers?

Aluminum

Silicon (correct)

Plastic

Copper

How many individual steps are generally involved in the production process of semiconductor wafers?

300 (correct)

200

350

250

What is one of the critical roles of foundries in technology?

Enabling advancements in computing power Signup and view all the answers

What is the purpose of the polishing step in wafer fabrication?

To enhance the surface smoothness Signup and view all the answers

In which step of wafer fabrication is silicon sliced?

Step Three Signup and view all the answers

What aspect of foundries is highlighted as critical in the modern world?

Their value in enabling digital connectivity Signup and view all the answers

Which of the following statements is FALSE regarding the semiconductor fabrication process?

It consists of simple and few steps. Signup and view all the answers

What is the primary purpose of the edge grinding procedure in silicon wafer manufacturing?

To round the edges and reduce breakage Signup and view all the answers

How much can the polishing step reduce breakage in the silicon wafers?

Up to 400% Signup and view all the answers

What is the highest clean room class rating in terms of cleanliness?

Class 1 Signup and view all the answers

What is the main function of the stock removal process during polishing?

To remove a thin layer of silicon Signup and view all the answers

What aspect is primarily focused on during the final polish of the wafer?

Surface cleanliness Signup and view all the answers

Which stage in the polishing process does not remove material?

Final chemical mechanical polish (CMP) Signup and view all the answers

What is the main requirement for workers in a clean room?

To don clean room suits Signup and view all the answers

What typically happens during a backside scrub of the wafer?

Surface particles and residues are removed Signup and view all the answers

What is the primary material used to create silicon wafers?

Silica sand Signup and view all the answers

What is the main advantage of using larger silicon wafers in semiconductor production?

Increases production at a lower cost Signup and view all the answers

What is the primary purpose of the Siemens process in silicon refinement?

To convert metallurgical grade silicon to electronic grade silicon Signup and view all the answers

At what temperature range is the reaction of silicon and hydrochloric acid conducted in the Siemens process?

300°C to 400°C Signup and view all the answers

What is the temperature required to reduce SiO2 to form silicon in the furnace process?

2,000°C Signup and view all the answers

What is the outcome of the reduction of purified trichlorosilane in the final step of the Siemens process?

Production of electronic grade silicon Signup and view all the answers

What type of silicon is produced as a result of the submerged electrode arc furnace process?

Metallurgical grade silicon Signup and view all the answers

What is the energy bandgap of silicon, allowing it to effectively control electrical currents?

1.1 eV Signup and view all the answers

What happens to the silicon carbide (SiC) during the reduction process in the furnace?

It reduces SiO2 to form silicon Signup and view all the answers

What structure does raw electronic-grade silicon have, making it unsuitable for semiconductor manufacturing?

Polycrystalline structure Signup and view all the answers

Which technique is NOT used to turn polycrystalline silicon into single crystals?

Crystal growth by fusion Signup and view all the answers

Which property of silicon aids in its reliability over various temperatures?

Thermal stability Signup and view all the answers

What are silicon wafers primarily used for?

Fabricating integrated circuits Signup and view all the answers

Which impurity affects the color of sand used in the construction industry?

Iron Signup and view all the answers

What characteristic of silicon dioxide (SiO₂) is crucial for semiconductor applications?

Electrical insulation Signup and view all the answers

What happens during the Czochralski Process at the melting point of silicon?

The silicon liquefies and becomes molten Signup and view all the answers

Which property of a single silicon crystal is essential for semiconductor devices?

Three-dimensional periodic pattern Signup and view all the answers

Why is silicon considered a cost-effective material in semiconductor manufacturing?

It is the second most abundant element in the Earth's crust. Signup and view all the answers

What role does the seed crystal play in growing an ingot of silicon?

It defines the crystal orientation of the ingot Signup and view all the answers

What mature processing technique is commonly used for silicon in the semiconductor industry?

Czochralski method Signup and view all the answers

During the Czochralski Process, what is the effect of rotating the seed crystal and crucible in opposite directions?

It enhances doping uniformity Signup and view all the answers

How does the scalability of silicon benefit the production of electronic devices?

It supports integration of billions of transistors on a single chip. Signup and view all the answers

What supports the high-volume production of silicon-based products?

Established supply chain Signup and view all the answers

Which of the following advantages does silicon NOT have for semiconductor applications?

Rare and costly Signup and view all the answers

Study Notes

Silicon Wafers

Silicon is a metalloid with the symbol Si and atomic number 14.
Due to its unique properties, Silicon is essential in the semiconductor industry.
Silicon wafers are thin, flat discs of silicon that are used as a substrate for fabricating integrated circuits.
The size of wafers range from 1 inch to 300mm with a thickness of 0.7mm.
Larger wafer sizes allow for the production of more chips simultaneously, which results in increased production at a lower cost.

Properties of Silicon

Silicon has an energy bandgap of 1.1 electron volts (eV), which makes it ideal for semiconductors as it allows it to control electrical current across a wide range of voltages and frequencies.
Silicon is abundant and cost-effective as it's the second most abundant element on Earth.
The semiconductor industry has developed efficient processing techniques for silicon, including the Czochralski method and photolithography.
Silicon has high thermal conductivity, which aids in heat dissipation, and it forms a durable layer of silicon dioxide that provides excellent electrical insulation.
Silicon supports the integration of billions of transistors on a single chip, enabling the production of high-performance microprocessors and memory devices.
The supply chain for silicon is well-established, with a global infrastructure supporting mass production.

Wafer Fabrication Process

The wafer fabrication process requires over 300 individual steps.
The process begins with the conversion of sand (silicon dioxide, SiO2) into silicon.
The starting material for Si manufacture is quartzite or sand.
Sand used in building industry is often impure, but pure silica sand is used for silicon manufacture.
The silicon is purified through a process called the Seimens process, which involves reacting the Si with HCL gas to form trichlorosilane, which is then purified through fractional distillation and reduced using hydrogen gas.
The resulting product is electronic grade silicon—nearly 100% pure Si.
The polycrystalline electronic-grade silicon is then turned into single crystals through the Czochralski Process or the Float Zone technique.
The silicon ingot is cut into thin wafers, which are then polished and cleaned in a dust-free clean room.
The polishing process involves using polishing pads and polishing slurry to remove a thin layer of silicon, leaving a mirror finish.
During the final polishing step, there is no removal of material.
Wafers are then cleaned and packaged for use in the fabrication of integrated circuits.

Czochralski Process

The silicon is heated above its melting point (1412°C).
A seed crystal is positioned on top of the melt, with the same crystal orientation required in the finished ingot.
The seed and molten silicon crucible rotate in opposite directions to ensure doping uniformity.

Wafer Cleaning and Polishing

The wafer cleaning and polishing process takes place in a highly controlled clean room environment.
The clean room rating system ranges from Class 1 to Class 10,000, indicating the number of particles per cubic foot.
Workers in clean rooms wear clean room suits to prevent contamination.
Typically, wafers are polished on the front side only, with 300mm wafers being polished on both sides.
The polishing process involves two steps: stock removal and final chemical mechanical polish (CMP).
The final polishing step leaves a mirror finish on the wafer.

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Description

This quiz explores the fundamental properties of silicon and its applications in the semiconductor industry, particularly focusing on silicon wafers. It covers the significance of silicon's energy bandgap, its processing techniques, and the advantages of larger wafer sizes. Test your knowledge on this essential material used in electronics.