Vacuum Ion Etching for Microelectronics Manufacturing

What pressure is UHV in your thinking?

Look at the surfaces of spacecraft and satellites being eroded by the solar wind!

Allow for big cryo-pumps.

RHABE

Ion etching can be performed at UHV conditions. I am not sure how much etching it can do but a plasma can exist at at least 10-11 torr. I built a vacuum chamber for Columbia University that was for a plasma fusion experiment and it was tested and used at 10-11 torr. If you visit the website for the LDX Cryostat at MIT you will see a torroidal magnet we built for another Plasma Fusion experiment and I believe the vacuum in that chamber was 10-10 torr. A Hydrogen Plasma is formed and contained aaround that magnet.

ability@ameritech.net

Hi,

plasma can exist at any pressure, there are lots of molecules and atoms existing at the lowest obtainable pressure and if you get a considerable fraction ionised, then you have a plasma.

And if you extract the ions by electric or magnetic action into a differentially pumped chamber you will have a lot of wanted together with some unwanted species.

Etch rate will be needed to judge if the original question can be answered.

Did you ever try to stabilise the outgassing performance of Al alloys? Pretty good if treated properly but welding is much more difficult so we switched to glued (from plates) constructions. Only intended for sputtering, so Viton seals and 10^-6mbar were sufficient.

RHABE

I do not see any reason not to get this done. There are equipments in field as well as in universities across USA which generate plasma of different ions for etching and coating. MIT goes to the limit of actual vacuum measuring standrad tool which is E-10 vacuum stability

Vacuum ion etching is a common practice in semiconductor industry. Typically reactive ion etching occurs at 10e-10 Torr to 10 e-12 Torr. Argon or nitrogen gas is ionized with RF energy to ionize the gas to isotropically etch down into the silicon surface on the wafer. Alternatively high energy microwave 6KW can disassociate O2 into mon-atomic oxygen for the same purpose but at higher vacuum limit of 10e-2 torr.

In the semiconductor industry most plasma etching is done near the 200-300 millitorr range. You can use more vacuum but that slows the process of etching way down.

With more vacuum you get less atoms able to "knock" a piece lose "in the plasma" to be etched.

I have quoted "in the plasma" because the etching actually takes place immediately next to the plasma. In the semiconductor industry the plasma does not actually touch the wafer. There is a depletion zone next to the wafer that has name that I can not remember right now.

-10 to -12 vacuum is for implanting into the wafer not removal from the wafer.

Plasma only contain a small percentage of ionized atoms. Most of the plasma is non ionized highly energetic atoms.

Come to my lab and I can prove this to you.