L08-Sputtering_b

L08-Sputtering_b - Sputtering (cont.) and Other Plasma...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Sputtering (cont.) and Other Plasma Processes
Background image of page 1

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

View Full DocumentRight Arrow Icon
Sputtering Summary ± Create an ionic plasma by applying a high voltage to a glow tube. ± Ions bombard the target material at the cathode. ± Target atoms are ejected (sputtered) from the cathode by energy and momentum transfer. ± Sputtered atoms from the target are deposited on to the substrate (anode).
Background image of page 2
Keys to Proper Sputtering ± The right choice of ions ² The atomic weights of the ions and the target atoms should be close. ± The right pressure for a sustainable plasma ² 10-1000 mTorr ± The right cathode voltage so that the ions have the right energy for sputtering ² E ion > 100 eV and V cath ~ 2-5 kV ± The right angle for high sputter yield ² 60° - 70° from normal ± The right substrate voltage and temperature for a clean film
Background image of page 3

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

View Full DocumentRight Arrow Icon
Glow Discharge Sputtering ± As the gas molecules are ionized and energized by collisions, eventually they will have enough energy to cause ejection of atoms from the cathode surface. ± This is not a very efficient system (ionic MFPs are very low due to their high mass). ± The film quality is not very good due to the high pressures required to maintain the glow.
Background image of page 4
DC Sputtering ± Initially pump system down to 10 -6 ²10 -7 Torr for purity. ± Then let in controlled amount of the gas to be ionized (generally Argon). ± Eventually the chamber pressure will be around 1 ² 100 mTorr. ² This number is determined by the pressure required to have a sustainable plasma given the chamber dimensions. ± The main control is the energy of the ions. ² They need to be in the right range for sputtering.
Background image of page 5

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

View Full DocumentRight Arrow Icon
Some Limitations of DC Sputtering ± The high pressures required to achieve a plasma can degrade film quality. ± Only a small fraction of the gas is converted to ions. ± All of this results in deposition rates that are low (~ 100 ǖ / min).
Background image of page 6
Substrate Biasing ± Applying a small negative voltage to the substrate (50 ² 300 V) ± Removes physisorbed (adsorbed) contaminants such as Oxygen ± Also, by increasing the energy of the surface atoms enhances diffusion ² This improves adhesion, nucleation and crystal structure. ± Other modifications to DC sputtering (hollow cathode, triode) enhance ionization and enable lower gas pressures.
Background image of page 7

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

View Full DocumentRight Arrow Icon
The Major Limitation of DC Sputtering ± Suppose instead of a metal, we want to sputter an insulator like quartz. ± Due to the high resistivity of the target running an appreciable current through would require an impossibly large voltage (~10 12 V).
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 02/29/2012.

Page1 / 26

L08-Sputtering_b - Sputtering (cont.) and Other Plasma...

This preview shows document pages 1 - 9. Sign up to view the full document.

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