Microcontamination Control in Wafer Fabrication

Questions and Answers

What is microcontamination primarily concerned with?

Micro foreign material or energy affecting products (correct)

Detection of visible dust in the air

Measurement of temperature variations

Monitoring chemical reactions in laboratories

Which of the following is NOT a control measure in wafer fabrication for microcontamination?

Electromagnetic Shielding (correct)

Clean Room

Ultra Pure Water

ESD Control

How does defect density influence yield according to the provided information?

Lower defect density increases yield (correct)

Yield is directly proportional to defect density

Higher defect density increases yield

Defect density has no effect on yield

According to Poisson's principles, yield is exponentially inversely proportional to which of the following?

Area of Product and Defect Density Signup and view all the answers

What typically causes short circuits and/or ESD damaged devices in microcontamination?

Particle-related failures Signup and view all the answers

Why does a smaller product size lead to a higher production yield?

Smaller surface area is less likely to be contaminated Signup and view all the answers

What is the detrimental effect of microcontamination on a product?

Reduced performance and reliability Signup and view all the answers

Which of the following statements about microcontamination and yield is true?

Higher cleanliness leads to improved yield. Signup and view all the answers

What is the range of sizes for particulates classified as contaminants?

0.01 to 100µm Signup and view all the answers

Why does device yield improve as things get smaller according to Poisson?

Failures are primarily attributed to contamination. Signup and view all the answers

Which of these is a characteristic of airborne particulates?

Weightless Signup and view all the answers

What size range of particulates can be considered invisible?

0.3 to 10µm Signup and view all the answers

Which of the following is NOT an example of invisible airborne particulates?

Human hair Signup and view all the answers

In the context of microcontamination control, why is the size of particulates critical?

Smaller particles can penetrate clean areas. Signup and view all the answers

What is a cleanroom designed to control?

Concentration of airborne particles Signup and view all the answers

Which particle size is closest to that of human hair?

75-100µm Signup and view all the answers

What type of dust is categorized as aerosols?

Metallurgical dust Signup and view all the answers

Which of the following characteristics is NOT true for particulates in contamination control?

They are typically heavier than air. Signup and view all the answers

What is the maximum allowable number of particles greater than 0.5µm in a Class 1000 cleanroom per cubic foot?

1000 particles Signup and view all the answers

Which filtration mechanism is primarily effective for small particles?

Electrostatic Signup and view all the answers

At what specific particle size does HEPA filter efficiency peak?

0.3µm Signup and view all the answers

What airflow speed is recommended for cleanroom operation?

70 to 110ft/min Signup and view all the answers

What is the primary reason for changing HEPA filters in a cleanroom?

When airflow speed decreases Signup and view all the answers

Which part of cleanroom attire is typically used to prevent contamination from saliva?

Face Mask Signup and view all the answers

What is the role of a raised floor in cleanroom operation?

To remove standing recirculating air Signup and view all the answers

What is a common source of contaminants in a cleanroom environment?

Human presence Signup and view all the answers

Study Notes

Microcontamination Overview

Microcontamination refers to foreign materials or energy that negatively impact a product or process.
Examples include solid particles, ions in liquids, molecular gases, vibrations, electromagnetic interference, and electrostatic discharge.

Microcontamination Control in Wafer Fabrication

Critical measures include maintaining a cleanroom environment, utilizing ultra-pure water, and implementing electrostatic discharge (ESD) control.

Effects of Microcontamination

Direct impact on product or process yield, performance, and reliability.
Particle-related failures can cause short circuits or ESD damage to devices.

Yield and Microcontamination

Yield (Y) is exponentially inversely proportional to both the area of the product (Y = e^-AD) and defect density.
Larger product size increases susceptibility to contamination; smaller sizes enhance yield in a cleaner environment.
Poisson's principles indicate yield is heavily influenced by microcontamination control measures.

Particulate Contaminants

Contaminants size ranges from 0.01 to 100µm, typically invisible and airborne due to their lightness.
In comparison, human hair ranges from 75-100µm, while visible particles are approximately 35µm.

Cleanroom Environment

A cleanroom controls airborne particle concentration and has designated clean zones.
Cleanroom class is defined by the number of particles (>0.5µm) per cubic foot, with Class 1000 having less than 1000 particles.

Cleanroom Operation

Key components include filtration systems and airflow control.
Filtration techniques encompass gravity, inertial impaction, direct interception, electrostatics, and diffusion.

Filtration Efficiency

HEPA filters achieve 99.997% efficiency at 0.3µm, while ULPA filters reach 99.999997% efficiency at 0.12µm.
Filtration maintenance is crucial, with filter changes indicated by decreased airflow speed.

Airflow Control in Cleanrooms

Recommended airflow speeds are between 70 to 110ft/min (0.35 to 0.45m/s).
Laminar flow systems combined with raised floors help eliminate standing air.

Contaminants from Personnel

Human activity is a significant contamination source; skin, sweat, and saliva contribute to particle contamination.
Cleanroom protocols require specific apparel like face masks, hairnets, jumpsuits, booties, and gloves to minimize contamination.

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Description

This quiz covers essential concepts of microcontamination, particularly in the context of wafer fabrication. It highlights the various forms of micro contaminations such as particles, ions, and energy interferences, along with the control measures like clean rooms and ultra-pure water. Test your knowledge on how to maintain the integrity of processes in semiconductor manufacturing.