Vacuum Technology and Photolithography Concepts

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Questions and Answers

What characteristic of gas molecules is given as 0.5 km/s?

Amplitude of oscillations

Characteristic velocity (correct)

Resonance frequency

Pump exhaust velocity

Which vacuum pump is identified as causing oil contamination?

Diffusion pump (correct)

Cryo pump

Rotary vane pump

Turbo-molecular pump

What is the amplitude of the resonant oscillations of the PZT plate?

0.1 mm

3 µm (correct)

20 MHz

0.5 km/s

Why might turbines in turbo-molecular pumps be used over piezoelectric oscillators?

They provide a greater velocity change. Signup and view all the answers

What is the consequence of molecules bouncing against a moving surface of an oscillator?

They have equal numbers that are both accelerated and slowed down. Signup and view all the answers

What is indicated by the resonance frequency of oscillations at 20 MHz?

The oscillation rate of piezoelectric crystals Signup and view all the answers

Which vacuum pump is not associated with oil contamination?

Cryo pump Signup and view all the answers

What property does helium have that makes it suitable for vacuum leak-testing?

It can penetrate small leaks easily. Signup and view all the answers

Which of the following statements about photolithography resolution is correct?

Resolution is limited by diffraction of light used for exposure. Signup and view all the answers

What primarily limits the speed of pattern writing by an e-beam?

Bandwidth of deflection system Signup and view all the answers

Which statement correctly describes the behavior of atoms during deposition methods?

Sputtering has better step coverage than evaporation. Signup and view all the answers

What is the effect of using a higher vacuum in a gas-transfer pump?

It prolongs the mean free path of gas molecules. Signup and view all the answers

How can the thickness of the edge bead in photolithography be effectively reduced?

By using circular wafers. Signup and view all the answers

Which of the following statements is true regarding pressure in the context of vacuum systems?

The higher the vacuum, the lower the pressure. Signup and view all the answers

Which characteristic does not help improve photolithography resolution?

Increasing the thickness of photoresist. Signup and view all the answers

In terms of deposition methods, which statement about sputtering is true?

Sputtered atoms often have higher kinetic energy than evaporated atoms. Signup and view all the answers

What happens to sputter yield in relation to the energy of incident ions?

Sputter yield is directly proportional to the energy of incident ions. Signup and view all the answers

In a diffusion process, how can the particle flux be described?

Particle flux is directly proportional to the concentration gradient. Signup and view all the answers

Which of the following parameters is NOT part of the simplified atomistic model of diffusion?

Pressure fluctuations Signup and view all the answers

What does the Debye length measure?

The size of a mobile electron cloud around a positive ion. Signup and view all the answers

Which formula is correct for estimating diffusion length?

(Dt)0.5 Signup and view all the answers

What characterizes the relationship between sputtering yield and beam incidence angle?

It first increases, then decreases with the angle. Signup and view all the answers

Which of these statements is accurate regarding the relationship of particle flux to concentration derivatives?

Particle flux is inversely proportional to the concentration time derivative. Signup and view all the answers

What is required for a discharge to occur?

Sufficient particle flux. Signup and view all the answers

What are the numbers used to describe plane orientations in a crystal lattice called?

Miller indices Signup and view all the answers

Which of the following factors does not affect photoresist adhesion?

Incorrect alignment Signup and view all the answers

Which etching method is not reliant on postbake?

Wet Etching Signup and view all the answers

What characterizes electron-beam lithography compared to photolithography?

It provides a smaller beam spot size Signup and view all the answers

In terms of decreasing de Broglie wavelength, which order of particles is correct?

Electrons, protons, photons Signup and view all the answers

Which statement about electron-beam lithography is true?

It has a limited fabrication throughput Signup and view all the answers

Which of the following methods uses phase-shifting masks to mitigate diffraction effects?

Electron-beam lithography Signup and view all the answers

Which of these factors is not relevant for the time of post bake?

Wavelength of exposure light Signup and view all the answers

What does photolithography resolution NOT depend on?

Density of photoresist Signup and view all the answers

In a simple evaporation-type thin-film deposition system, what is the function of the shutter?

To allow periodic termination for better uniformity Signup and view all the answers

What is the ratio of the thin-film thickness at the edge of the wafer to that in the center if it is 4” below the center?

0.77 Signup and view all the answers

According to Le Chatelier's principle, what happens when the conditions of a system in equilibrium are changed?

The equilibrium will shift to amplify the changes Signup and view all the answers

In thin-film deposition without a shutter, which of the following is true?

Thin films can be deposited under continuous conditions Signup and view all the answers

What can be concluded about the relationship between thin-film thickness and distance from the center of the wafer?

Thickness decreases as distance from the center increases Signup and view all the answers

Which factor primarily affects the uniformity of thin film thickness during deposition?

Shutter operation Signup and view all the answers

What effect does heating have on an unstable equilibrium system according to Le Chatelier's principle?

It can cause an explosive reaction in certain conditions Signup and view all the answers

Study Notes

Vacuum Pumps

Cryo pumps, Diffusion pumps, Turbo-molecular pumps, and Rotary vane pumps all can be used to create a vacuum environment.
Diffusion pumps can cause oil contamination, while turbo-molecular pumps and rotary vane pumps can also cause oil contamination.
Moving turbine blades in a turbo-molecular pump add velocity to gas molecules pushing them towards the pump exhaust, this helps reduce pressure in the vacuum chamber.

Pumping Speed and Pressure

Pumping speed measures the ability of a pump to remove gas from a vacuum chamber.
Pumping speed is determined by the momentum transfer of gas molecules colliding with the chamber walls during pumping.
The higher the vacuum, the lower the pressure and the longer the mean free path in the chamber.

Photolithography Resolution

Higher resolution in photolithography can be achieved by using shorter wavelengths, larger numerical aperture lenses, and phase-shifting masks.
Resolution is limited by the diffraction of light used for exposure.
Thick photoresist does not improve photolithography resolution.

E-Beam Lithography

E-beam lithography has a smaller beam spot size and a higher flexibility compared to photolithography.
E-beam lithography can have raster and vector modes for exposing the desired pattern.
E-beam lithography has a limited fabrication throughput, but this can be overcome by using newer technologies.

Thin Film Deposition

Sputtering and evaporation are common methods for thin film deposition.
Atoms deposited by evaporation typically have lower kinetic energy than sputtered atoms.
Sputtered atoms undergo more collisions before landing on the substrate compared to evaporated atoms.
Sputtering has better step coverage than evaporation, but fewer grain orientations compared to evaporation.
Sputter yield depends on the energy of incident ions and the crystallographic orientation of the target.
In evaporation deposition, a shutter is often used to control the deposition process and ensure homogeneity of the film.

Diffusion

Diffusion is a process where particles move from areas of high concentration to areas of low concentration.
The particle flux is directly proportional to the concentration gradient.
The main parameters for a simplified atomistic model of diffusion are jump frequency, jump distance, and activation energy.

Debye Length

The Debye length is a measure of the size of the mobile electron cloud that forms around a positive ion when it is pushed into charge-neutral plasma.
It can also be seen as the average distance between charged particles in the plasma.

Crystallography

Miller indices are used to describe plane orientations in a crystal lattice.

Photoresist Adhesion

Photoresist adhesion is affected by the wetting characteristics of the resist, surface smoothness, and the alignment of the resist during processing.
Postbake is not needed for wet etching, lift-off, and Ar-ion etching processes.

Le Chatelier's Principle

When a system in equilibrium is subjected to a change in conditions, the system will shift in a direction to minimize the change.
The new state of the system will be the new equilibrium.

Thin Film Thickness

Thin-film thickness can be affected by many factors, which may leads to a gradient in film thickness across the wafer.
In cases where a wafer is not perfectly level the film thickness will be greater in the center of the wafer and lesser at its edges.

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Description

Explore the principles behind various types of vacuum pumps and their applications in creating optimal vacuum conditions. This quiz also covers the essentials of pumping speed, pressure, and resolution techniques in photolithography, crucial for manufacturing processes. Test your knowledge on these integral topics in vacuum technology and imaging systems.