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SP 2005 Lecture03 Preview

This lecture will cover concepts related to vacuum systems and thin film growth, including mean free path, flux, pressure, and gas kinetics. The lecture will explain how these concepts are used in microfabrication processes and vacuum pumping systems. Key concepts that students should review beforehand include the definitions of flux, mean free path, the ideal gas law, and Maxwell's speed distribution. Understanding these foundational concepts will help students learn how to apply them to thin film deposition.

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51 views1 page

SP 2005 Lecture03 Preview

This lecture will cover concepts related to vacuum systems and thin film growth, including mean free path, flux, pressure, and gas kinetics. The lecture will explain how these concepts are used in microfabrication processes and vacuum pumping systems. Key concepts that students should review beforehand include the definitions of flux, mean free path, the ideal gas law, and Maxwell's speed distribution. Understanding these foundational concepts will help students learn how to apply them to thin film deposition.

Uploaded by

stansilaw
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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3.155J/6.

152J Spring Term, 2005

Preview and preparation for Lecture 3, Feb.9, “Vacuum Systems, film growth”.

In this lecture we will review concepts of mean free path, flux, pressure, and gas kinetics
in order to understand the role of vacuum pumps and chamber pressure on the quality of
the thin films you will be depositing.

Concepts you are expected to be familiar with before class begins are listed below. (You
do not need to know how to derive these.) In this class you will learn how to use these
concepts in the context of microfabrication.

1. Flux, J, of particles: the number of particles flowing through a unit area per
unit time:
J = N /(area ¥ time) .

2. Concept of flux, J, of a species diffusing down the concentration gradient,


∂c/∂x (c = number /volume), in a solid. J is proportional to diffusion constant
D (cm2/s): †
∂c
J x = -D
∂x
Plummer sections 7.1 to 7.2.2 should get you up to speed.

3. Mean free path, l: the average distance a particle travels between collisions,
† its momentum.
i.e. events that change

4. Ideal gas law relating pressure, volume, temperature, and number of particles:
pV = NkB T (or pV = NRT )
or p = nkB T , i.e. n = N/V

Check your high school or freshman chemistry books


† †
† prepared)
(…and if you are well
5. Maxwell speed distribution describing the probability, P(v), of finding a
particle with a particular speed for given particle mass, m and temperature T.
È E ˘ È mv 2 ˘
P(v) µ v 2 expÍ- k ˙ = v 2 expÍ- ˙.
Î kB T ˚ Î 2k B T ˚
Note, `v may be different from vrms

Ohring, “Materials Science of Thin Films” (on class reading list), sec. 2.1 is
† source.
an adequate

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