Engineering Module: Integrated Circuits & Microprocessors

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Questions and Answers

What is the primary challenge when connecting internal circuits to external circuits in IC packaging?

Minimizing the cost of materials

Reducing the size of the device

Ensuring high reliability of components

Managing the number of I/O terminals (correct)

Which material provides excellent hermetic sealing for IC packages but may experience dimensional shrinkage during firing?

Ceramic (alumina) (correct)

Silicon

Metal

Plastic (epoxy)

What is a common style for IC packaging that can be configured for both through-hole and surface mount technology?

Square package

Pin grid array (PGA)

Dual in-line package (DIP) (correct)

BGA (Ball Grid Array)

What is a crucial factor for profitability in semiconductor IC fabrication?

Achieving high yields Signup and view all the answers

Which issue is primarily related to environmental factors affecting IC performance?

Heat dissipation Signup and view all the answers

What is the purpose of final testing after IC packaging?

To check for damage and ensure functional performance Signup and view all the answers

What is a significant disadvantage of using plastic materials in IC packaging?

Lower robustness compared to ceramics Signup and view all the answers

Which IC package style features closely spaced pins in a multi-pin arrangement?

Pin grid array (PGA) Signup and view all the answers

What is one of the steps involved in the manufacturing of ICs?

Encapsulating the chip in a package Signup and view all the answers

What complicates the IC packaging process due to device size reduction?

Increased complexity of interconnects Signup and view all the answers

What is the primary material used in the fabrication of integrated circuits due to its favorable properties and cost?

Silicon Signup and view all the answers

What is the primary reason for maintaining cleanliness in a clean room environment during IC fabrication?

To minimize contamination affecting microscopic features Signup and view all the answers

Which level of integration describes ICs that can embed millions of microscopic devices on a single chip?

Very Large Scale Integration (VLSI) Signup and view all the answers

Which of the following statements about electronic grade silicon (EGS) is true?

EGS is the main material for fabricating microelectronic chips. Signup and view all the answers

What is a significant reason for packaging integrated circuits?

To protect from environmental damage Signup and view all the answers

The Czochralski process is primarily used for what purpose in silicon processing?

To pull a single crystal boule from molten silicon Signup and view all the answers

What measurement is typically used to define cleanliness standards in clean rooms?

Number of particles per cubic foot of air Signup and view all the answers

What stage follows the refinement of sand into pure silicon in the processing sequence for silicon-based integrated circuits?

Lithography Signup and view all the answers

What is the primary characteristic of solid-state electronics?

They are fabricated into a solid piece of material. Signup and view all the answers

Which characteristic is NOT important when slicing silicon wafers?

Chemical composition of the saw blade Signup and view all the answers

Why are edges of wafers typically rounded during the preparation process?

To provide easier handling and reduce chipping Signup and view all the answers

What approximate dimensions describe typical silicon chips used in integrated circuits?

5 to 25 mm on a side Signup and view all the answers

Which processing technology is involved in creating, altering, and removing thin layers on silicon wafers?

Fabrication Signup and view all the answers

What is the primary purpose of chemical etching in wafer preparation?

To remove damaged surfaces from slicing Signup and view all the answers

In semiconductor processing, what type of silicon is used for ensuring high performance in ICs?

Electronic grade silicon with ultra-high purity Signup and view all the answers

Why is a clean room environment critical during the IC fabrication process?

To prevent contamination of sensitive materials Signup and view all the answers

What device is a typical component in an integrated circuit?

Transistor Signup and view all the answers

What process involves cutting wafers into chips using a thin, diamond grit saw blade?

Wafer slicing Signup and view all the answers

What does the acronym ULSI stand for in the context of integrated circuits?

Ultra Large Scale Integration Signup and view all the answers

Which of the following best describes the implications of cleanliness on feature size in ICs?

Higher cleanliness levels are crucial for maintaining smaller feature sizes. Signup and view all the answers

What is the primary purpose of photolithography in wafer processing?

To transfer a geometric pattern to the wafer surface Signup and view all the answers

Which type of lithography uses ultraviolet light for exposing the photoresist?

Photolithography Signup and view all the answers

What is a significant disadvantage of contact printing in lithography?

Physical wear on the mask Signup and view all the answers

How does proximity printing improve upon contact printing?

By eliminating mask wear Signup and view all the answers

What is the effect of UV exposure on photoresist during lithography?

It changes the photoresist's solubility based on the mask pattern Signup and view all the answers

What is the primary function of the mask in photolithography?

To define the geometric pattern for circuit designs Signup and view all the answers

What is a key advantage of projection printing over contact printing?

It provides improved resolution and eliminates mask wear Signup and view all the answers

What occurs to the silicon wafer during the initial step of photolithography?

It is oxidized to form SiO2 Signup and view all the answers

What does the processing sequence in photolithography primarily aim to achieve?

To selectively modify the wafer surface using photoresist Signup and view all the answers

What is associated with the final fabrication step in integrated circuit packaging?

Connecting components to external circuits Signup and view all the answers

Study Notes

International & Access Foundation Programmes: Engineering Module, Semester 1

The module covers Integrated Circuits & Microprocessors, part of Electronic & Electrical Engineering.
The lecturer is Dr Nevan Bermingham.

Integrated Circuits (ICs)

ICs are collections of electronic components (transistors, diodes, resistors).
These components are fabricated and interconnected on a small silicon (Si) semiconductor chip.
Silicon is the most widely used semiconductor due to its properties and cost.
Other semiconductor materials include germanium (Ge) and gallium arsenide (GaAs).
The term "solid-state electronics" describes circuits made from a single solid piece of material.

Levels of Integration in Microelectronics

Integrated circuits evolve over time, increasing in complexity and the number of devices on a chip.
This progression includes Small Scale Integration (SSI), Medium Scale Integration (MSI), Large Scale Integration (LSI), Very Large Scale Integration (VLSI), Ultra Large Scale Integration (ULSI), and Giga scale integration.
Data on the number of devices and approximate year of integration is included in the course.

Overview of IC Technology

ICs contain hundreds, thousands, or millions of microscopic electronic devices.
These devices are fabricated and interconnected on a silicon chip.
The chip is a thin rectangular plate, usually 5-25mm on a side and 0.5mm thick.
Different layers with distinct electrical properties form each electronic component (e.g., transistor).
These layers work together to accomplish the device's functions.

Packaging of ICs

ICs are packaged outside the clean room to prevent environmental damage.
Packaging involves attaching the chip to leads and enclosing it in a protective package.
This package protects from factors like moisture, corrosion, temperature fluctuations, vibration, and shock.
The package includes leads that connect the IC to external circuits.

Processing Sequence for Silicon-based ICs

Sand is refined into pure silicon, forming wafers.
Fabrication involves creating, altering, and removing layers to form electronic devices.
Lithography defines the processing regions on the wafer's surface.
Packaging processes test, divide into units, and encapsulate the chips.

Clean Rooms

IC fabrication occurs in controlled environments called clean rooms to minimize foreign particle contamination.
Cleanliness is crucial for maintaining feature size; standards are measured by the number of particles per cubic foot of air (e.g., class 100 or 10).
The level of cleanliness is directly related to the size of microscopic features on the integrated circuits and is decreasing annually.

Silicon Processing

Electronic-grade silicon (EGS) is the main material for microelectronic chips.
It makes up over 95% of semiconductor devices worldwide.
Purification, crystal growing, and wafer shaping are critical steps in substrate fabrication.

Crystal Growing

Silicon substrates for microelectronic chips require single-crystal structure with specific unit-cell orientations.
Semiconductor device fabrication demands ultra-high-purity silicon.
The Czochralski process is a common technique for pulling a single crystal boule from molten silicon.

Wafer Slicing

Wafer slicing uses a diamond-grit saw to cut silicon ingots into individual chips.
Slicing happens at the internal diameter of the blade to ensure uniform thickness, parallelism, and flatness.
Wafer accuracy and reduction of kerf loss are crucial during slicing.

Wafer Preparation

Wafer rims are rounded to prevent chipping.
Chemical etching removes damage, followed by polishing for smooth surfaces.
Chemical cleaning removes residues and contaminants.

Lithography

ICs have microscopic regions on the wafer.
Planar processes involve adding, altering, or removing layers to create a specific pattern on the wafer.
Lithography transfers circuit design information to the wafer surface.

Lithographic Technologies

Various lithography techniques exist (photolithography, electron lithography, X-ray lithography, and ion lithography) using different radiations to transfer the mask pattern to the wafer surface.

Photolithography

Light radiation exposes a photoresist coating on the wafer to transfer the mask pattern.
UV light is common for high-resolution imaging.
A mask prevents unwanted exposure.
Photoresist is an organic polymer, sensitive to light (UV).
Patterned mask exposure controls photoresist solubility.

Photoresists

Photoresist is an organic polymer which is sensitive to light
UV exposure impacts photoresist's solubility and is controlled by the pattern on the mask.
Photoresists selectively alter the wafer surface during processing.

Contact Printing, Proximity Printing, and Projection Printing

Contact printing presses the mask directly against the resist for high resolution but can cause wear.
Proximity printing separates the mask from the resist, reducing wear but slightly reducing resolution.
Projection printing projects the mask pattern onto the wafer using lenses for higher resolution and less mask wear.

Processing Sequence in Photolithography

The wafer surface is oxidized to form SiO2, preparing it for photolithography.
Photolithographic steps follow the processes.

IC Packaging

Packaging is the final IC fabrication step connecting components to external circuits and protecting from environmental damage.

Design Issues in IC Packaging

Electrical connections to external circuits.
Protection from factors like humidity, corrosion, temperature, and heat dissipation.
Manufacturing cost is critical.
Issues involve separating the chips from the wafer, connecting them to packages, and encapsulating them.

Input/Output (I/O) Terminals

Interconnecting internal to external circuits is challenging due to the high numbers of devices and reduced size.
Device size reduction and more devices increase interconnection complexity.

IC Package Materials

Ceramic (alumina – Al2O3) is a common material for IC packages.

Yield Testing

After packaging, each IC undergoes tests for damage and functional characteristics.
IC yield loss and variations during fabrication are significant factors.
High yield is critical to profitability.

Wafer Processing

High-quality production requires pure starting materials, modern processes, well-maintained clean rooms, and effective testing procedures.

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Description

This quiz focuses on the Engineering Module for International & Access Foundation Programmes, specifically on Integrated Circuits and Microprocessors. Explore the levels of integration in microelectronics and the materials used in fabricating ICs. It is essential for understanding the foundations of Electronic & Electrical Engineering.