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Sputtering Target Care

Care and Feeding of Your Sputtering Target

Getting Set-up to Sputter

Cleanliness is paramount when working with a vacuum chamber and, specifically, a sputtering system. Any residual build up of grease, dust, and old coatings will trap water and other contaminants and both impede your ability to achieve a good vacuum and increase the possibility of making bad films. Target arcing, surface roughness in deposited films, and trace chemical impurities are often times linked to dirty sputter chambers, guns and targets.

The cleaning requirement extends to the backing plate, dark space shield, chamber walls, and other neighboring surfaces as well as the target itself. To clean the vacuum chamber, we recommend that you bead blast the dirty components THAT YOU CAN EASILY REMOVE FROM THE SYSTEM (using glass beads), then lightly brighten the surface using alumina impregnated sand paper. Following the sanding, the surfaces should be chemically washed through a series of bathes including trichlor, acetone, alcohol, and deionized water. We prefer to use an ultrasonic bath for these rinses, with cycles of 5 minutes per fluid.

Our sputtering target will be shipped to you in a clean, vacuum sealed, poly bag. It is important that you never touch the target with bare hands - likewise you should wear protective gloves whenever working inside your sputter chamber.

In the event that the target does need cleaning:

Metal Targets can be cleaned using a four step process. First the target should be wiped using a lint-free lab towel soaked in acetone, followed by a similar wipe with alcohol, followed by a final wipe with deionized water. After the final wipe, the target should be baked out in air for 30 minutes at 100ºC. DO NOT USE A BEAD BLASTER ON THE TARGET SURFACE.

Oxide and Ceramic Targets can be cleaned using a non-impregnated "scotch bright" pad. After removing the soiled area, flush the target with high pressure, low moisture, Argon gas - to remove any dust particles that may cause arcing in the sputter system.

Installing the Target

There are several important things to accomplish during target installation. The most important aspect of installation is establishing a good thermal coupling between the target and the cooling well in your sputter gun. The target, and bonding assembly (if applicable) were checked for flatness during final inspection at our facility, prior to shipment. The assembly is flat to within the tolerances specified in our standard specifications. YOU MUST CHECK THE FLATNESS OF THE COOLING WELL OF YOUR SPUTTER GUN.

In our experience, warpage of the sputter gun can be a real problem. Many gun manufacturers provide a silver load vacuum grease to use as a thermal link between the target and gun - to adjust for whatever variations there may be between the two surfaces. This thermal grease works well and helps hold the target in place during installation.

If the warpage of your sputter gun exceeds our flatness specifications you may have a problem getting good thermal conductivity through the backing plate to the target. Further, when you attempt to clamp a target assembly to a warped surface it is possible to bend or crack the target.

Refer to the Operations Manual for your gun on how to secure a target in the assembly. If your manual has omitted this section then try our technique. When tightening the target clamps, make sure that you torque the clamp bolts as you would a car wheel. Finger tighten one bolt, then go opposite the bolt - across the diameter of the target, and finger tighten another bolt. Then move one bolt to the right and repeat, until all bolts are finger tight. Next - using a tool, tighten the first bolt further, and repeat the torquing pattern again.

We recommend - for round targets - that you bond ceramic targets into our copper cooling cups. These bonding assemblies improve the mechanical integrity of a ceramic target and also allow you to clamp directly to the copper edge of the cup - instead of clamping to the target itself. This greatly reduces the chance of cracking the target during installation and operation.

Target Break-In

Power should be ramped up SLOWLY to avoid arcing. Typical ramp rates for oxides are 10 watts /hour /square inch of target surface. On a 2" diameter target this means that 30 watts /hour is a good break-in ramp rate. Metal targets are much faster to break-in than oxides and can be ramped faster. A reasonable ramp rate for non-refractory metal targets is 50 watts /hour /square inch of surface area.

For metal targets ramp at 50 watts /hour /square inch of surface area. Check the target for arcing - and let it sputter for 5 minutes. If no arcing occurs, continue to ramp the power to the desired operating density. As a "rule of thumb" we use a maximum operating power density for metal targets of 140 watts /square inch of surface area.

Refer to your systems Operation Manual for recommended chamber pressure settings during deposition.

Target Maintenance Between Depositions

You may experience some build up of sputtered material on the center and outside the racetrack of your target. It may be necessary to remove this material periodically in order to avoid arcing during deposition. This will allow continued operation of your target at the maximum power density. Refer to the section on GETTING SET-UP for tips on target cleaning for oxides and metals.

Target Storage Between Depositions

We recommend that you always keep your targets, metal or oxide, stored under vacuum. To assist you, we ship your targets in vacuum sealed poly bags. We suggest storage in a vacuum desiccator jar which is essential to maintaining target integrity on reactive materials such as Barium metal, or even YBCO. You can also store your targets in your deposition system, under vacuum. Metal targets are much more forgiving and can usually be sealed and stored in a dust free bag.

Remember - NEVER TOUCH A SPUTTERING TARGET WITH YOUR BARE HANDS.

More Technical Support

If you have questions that weren't answered in the section above please fill out our Technical Question Submission Form and let one of our sales engineers assist you. We have also compiled a list of technical papers from clients who have used our materials, and there may be something in our library that can help.