Looking To Upgrade Your E-Beam System?
With thousands of E-Beam systems worldwide, there is certainly a need for gridded ion sources for improved optics. Plasma Process Group has a team that is familiar with these upgrades and can provide support for your next step toward an improved process.
We can help you choose a source that is best for your configuration by first referring you to our learning center on our website. There, you can see some theoretical beam profiles and beam energy levels based on the ion source. You can also review process related papers that talk about the assist source processes commonly used, and some of the advantages for a variety of coating processes. Let us know if you are looking at upgrading your system and we can help go over our options with you.
Affiliated Machine Shop Open for Business
One of the advantages to our growth over the years is gaining additional resources. We are excited to announce our new sister company, Millennium Machining is open for business. Millennium Machining is a fully operational high vacuum quality machine shop. This enables us to support our own machined products, as well as provide vacuum qualified machining for your specific equipment.
If you are looking for a vendor with a background in machining components for your vacuum system, Millennium Machining LLC is ready to support you. They can provide a one-off part for a prototype project, provide ongoing production machining, and even machine custom tooling for your planetary like substrate holders. They currently have short lead times. Please contact Millennium Machining LLC for your next project. The Website is coming soon. Give Joe O’Brien a call at 1-970-833-1983 or send him an email at [email protected]
Tech Tips – Parasitic Plasma Formation
Have you ever had your RF source just go out for no apparent reason? One of the most annoying parts of this problem is the dreaded E-71 error! Those familiar with this error code, know what we are referring to. This is the error you see when the source goes out. Unfortunately, this error happens for a broad range of different source failures. It could mean many things. However, one common cause is parasitic plasma.
Parasitic plasma is an unwanted plasma that is generated outside the discharge chamber of an RF source. That usually means that pressure outside the source discharge chamber is much greater than the inside. This higher pressure makes it very easy to generate parasitic plasma. Unfortunately, it is produced where it is not wanted. Below is an image of a source that has had a single event of parasitic plasma. Note that in this case everything appears to be copper colored, including the antenna insulators.
Why does it happen? The most common cause is higher pressure in this area of the source. If pumping is not sufficient, or you have a leak, pressure behind the source increases and the plasma can form. Causes can be a leaking gas fitting or gas isolator, a water leak or atmospheric leak at a flange seal surface, or even a worn out cryo pump for example.
What does it do to the source? – When it happens, it is almost always catastrophic. The plasma generated sputters silver and copper from the antenna and RF leads and deposits the metal material all over the inside of the shroud, including the ceramic insulators meant to isolate the RF from ground. This plasma, when generated, quickly changes impedance of the RF power, and shuts down the source. You may be able to restart it, but usually by this time the damage has already been done. It will likely keep happening so it’s best to stop while you are ahead.
What can you do to fix it? – First and foremost, find the cause. Remove your grid set and look for deposition patterns on the inside of the shroud behind and around the discharge chamber. Also look around the RF leads from the feedthrough to the antenna. If there is shiny silver or copper anywhere other than the leads and antenna, then you may have had parasitic plasma develop. If you’re not sure what to look for, send us some good quality photos of the inside of your source. Below is an image of a brand-new source with no coated areas on the inside of the source.
Leaks can occur anywhere there is a connection point. Gas lines, gas isolator, water lines to the antenna, and at the feedthrough. Most common water leaks occur at the copper to stainless steel gland braze point. They do not need to be large leaks either. Once the cause is identified, repair it. Then remove the source, media blast the shroud and shroud back plate, and clean all ceramics and metal surfaces of the DC connection spring tabs while being careful not to damage seal surfaces for water line connections. Be sure to also clean the grids and DC leads inside the source. Check for conductance between the two metal ends of the gas isolator, if there is conductance, replace it.
Why not just clean all the ceramics and try again? – Because if it happens again, you won’t know it because the source is still dirty from the first event. So, you cannot detect if the plasma has occurred again. Addressing the issue completely by cleaning everything will greatly reduce your chances of more downtime and chasing more issues.
Can’t find any leaks? Check your pumping. Even if you have a great base pressure in your chamber and your cryo pump temps are within normal operation range, remember this; the 1st stage cryo temperature should not exceed 65K. This is the threshold for this unwanted plasma to occur. Check your 1st stage cryo temp during process, not just while at base pressure. When under load and running process, the cryo efficiency drops and your pressure behind the source can increase. If the temperature exceeds 65K there is a high probability that this event may have occurred. Your Cryo likely needs to be refurbished because it has lost its pumping efficiency under load. We hope this Tech Tip helps you but if not, and you still have questions, call us.