lecture_14_chex42

lecture_14_chex42 - Vacuum Science and Technology Vacuum !...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Vacuum Science and Technology Vacuum Science and Technology ! Most CVD , Epitaxy and Plasma processes use vacuum ! Vacuum : < 1 atm = 760 Torr ! ~ 0.1-760 Torr : Rough Vacuum ! ~ 10 -4 -0.1 Torr : Medium Vacuum ! ~ 10 -8 -10 -4 Torr : High Vacuum ! < 10 -8 Torr : Ultrahigh Vacuum (UHV) ! Base pressure: the lowest pressure the chamber can be pumped down to without any gases flowing. ! Processing pressure (with gases flowing) maybe higher than the “base pressure”
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Why doesn’t pressure go to 0? Why doesn’t pressure go to 0? pump chamber virtual leaks leaks ! Even if gas flow is 0, there are always leaks. They may be very small but they are always there. ! Virtual leaks are leaks that are not associated with transport across the chamber wall but act as a gas source (e.g. , desorption from gas walls, slow leak of gas trapped inside crevices and cracks.) ! Pumps are characterized by pumping speed (liters/second, m 3 /h, etc.) ! They are called vacuum pumps but they are really compressors. ! Think of pumping speed as volume captured per
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/29/2011 for the course CHE 142 taught by Professor Ceweb during the Fall '09 term at UCSB.

Page1 / 18

lecture_14_chex42 - Vacuum Science and Technology Vacuum !...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online