Sputtering Targets

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At ACI Alloys, Inc. sputtering targets are made from high-purity elemental metals.

Arc-casting in inert gas (argon) means 100% density and minimal oxygen.

Sputter targets may also be hot-pressed, cold pressed, vacuum induction melted, hot or cold rolled or cut from sintered plate.

The targets are then machined to within the tolerances of the customer’s sputtering system in house. Our full machine shop with lathes, mills, grinders, EDM and experienced staff mean that we are able to make intricate shapes with difficult material.

Finally, our targets are vacuum-sealed and shipped to the customer, usually as soon as they are finished.

We offer quick turn-around times because we specialize in the research and development market.

ACI Alloys Inc stocks many standard crucibles for evaporation in commonly used materials like Tungsten, Molybdenum, Tantalum, Graphite, Al2O3 and more.

Because of our large material range, we can make no standard materials into crucibles and liners to help you find the maximum efficiency for your evaporation process.

(Note: some of the below suggestions appeared in the “Ask Stan” column in Vacuum & Coating Technology magazine. -Charles Albert, PhD, ACI Alloys, Inc.)

1. Are you DC-sputtering a target that has high magnetic permeability? If so, you may need to reduce the thickness of the target, or else switch to RF-sputtering.

2. Does your target have low electrical conductivity? If so, you may only be able to do RF sputtering with it.

3. Verify that the ground shield is installed properly, and is not grounding out the target, and that it is creating the necessary “dark space”.

4. You may be able to improve the electrical conductivity by applying a conductive paste to the bottom surface of the target, or by bonding the target to a copper backing plate.

5. Be sure you have sufficient water flow cooling the target, and that the exit water is not warm. This may trip an interlock.

6. Check the magnetic field: for a 2″ magnetron gun, it should be several hundred gauss at 1cm from the target.

7. Make sure the system pressure is not too high. Look for signs of internal discharge besides on the substrate.

8. Has the target been properly degreased, and handled only with clean, lint-free gloves?

(Note: some of the below suggestions appeared in the “Ask Stan” column in Vacuum & Coating Technology magazine. -Charles Albert, PhD, ACI Alloys, Inc.)

1. Is there any chamber shielding? If so, is it getting a build-up? This can affect vacuum, effective power, etc. It may need replacing.

2. Chemically active materials (Al, etc.) may react with water to release H2, lowering power yield but not otherwise easily measurable. Try pumping longer, or a mild bake, or water vapor pumping.

3. Change the water in your closed cycle cooler on the turbopump/sputter source.

The below information comes from the Gencoa.com faq:
4. What principles determine the maximum power I can apply to my target materials?

A: The main aspect to what power the target can withstand is down to the material itself and also the means of heat removal from the target or backing plate. For good thermal conductors such as Cu and Al which also have good mechanical properties, max power densities can be high (20-50 W/cm2).

If the target is bonded to a backing plate (as is the case for more fragile or soft materials), then the bond material maybe the point of weakness due to a low melting point (in the case of indium). There are higher melting-point bonds, but for the family of bonded targets the maximum power density is generally 10-20 W/cm2).

Thermal shock is also a problem. Brittle target materials will crack if the power is too high or the thermal heating and cooling cycle is too agressive. For these materials generally the maximum is 5-15 W/cm2.

For low melting point target materials, the heat removal will be the most important, and special high water flow magnetrons are recommended. Power levels for such materials are 5-20 w/cm2 depending upon the cooling mode, efficiency and the material.

Once the power density that the material can withstand has been assessed its important to always bear in mind the coating quality required. Even though high powers maybe possible, the demands of the product may limit the effective power that can applied.

5. What is the operating standard range of distances from target to substrate?

A. As a general rule, the target to substrate separation should be more than the target width / 2. So if its a 150mm wide target 80mm t-s is good. Any closer and the substrate will be in the magnetron plasma and could become charged electrically leading to substrate heating, arcs or thin film device damage. Further away and the uniformity drop-off starts at the ends starts to increase. Sometimes the distance is greater to reduce heating effects on temperature sensitive materials.

The issue of degreasing a sputter target is necessitated by the nature of the manufacturing process. Any sputtering target will require mechanical finishing–i.e. machining or grinding–to uniform, finished dimensions after the slug of material has been vacuum-cast or hot-pressed. It is this mechanical finishing that can introduce the greases that must be removed before the material is compatible with a high-vacuum environment.

The standard method for removing surface contamination is wiping with a lint-free material that has been soaked in isopropyl alcohol.

In special cases of extremely reactive materials (e.g. rare-earths, alkali metals), isopropyl alcohol is not recommended. In that case, paint-thinner has been found to be satisfactory in removing the protective oil coatings often covering these materials (commercially-available at retail stores like Sears).

Certain evaporation materials can be direct-cast with no machining or grinding necessary afterward. ACI Alloys can make a variety of materials in this fashion: especially, precious metals, refractories, and other non-reactive materials.

Other elements and alloys, notably Au/Be, Al-bearing alloys, Cr-bearing alloys, and rare-earths, will develop an oxide layer in the melting process, and are not suited for this method of manufacture. Their surfaces must be cleaned abrasively to remove their oxides.

OTHER METHODS: RESULTS OF WEB SEARCHES FOR DEGREASING A SUBSTRATE

1. Spray impingement with an Alliance Aquamate SF booth

2. Since lanthanum is easily oxidizable, it is soaked in oil (liquid paraffin). Thus, acetone was eliminated by degreasing or, as needed, ultrasonic cleansing.

3. Ultrasonically in acetone

4. Degrease in warm (40° C.) alkaline surfactant

5. Samples were sandblasted and degreased by ultrasonic cleaning in acetone

6. Si substrates of electronics grade were cleaned in acetone and methanol in an ultrasonic bath. Then the substrates were subjected to vapour degreasing in isopropyl alcohol and were dried in a hot atmosphere of it.

7. Then the substrates were subjected to vapour degreasing in isopropyl alcohol