Gold (Au) Pellets Evaporation Materials

Gold (Au) Pellets Overview

We sell these pellets and pieces by unit weight for evaporation use in deposition processes. These approximate materials prices are published to provide budgetary guidelines. Actual prices can vary and may be higher or lower, as determined by availability and market fluctuations. To speak to someone directly about current pricing, please click here .

Gold (Au) General Information

Gold is one of the most valuable and sought-after metals in the world. Since its discovery during ancient times, it has been utilized as jewelry, coins, and tools. Still, in today's economy, its most popular use is as jewelry. Gold is one of the more beautiful precious metals with a lustrous, yellow sheen. It has a melting point of 1,064°C, a density of 19.3 g/cc, and a vapor pressure of 10^-4 Torr at 1,132°C with its ideal evaporation temperature being around 1,400°C. It is soft, dense, malleable, ductile, and an excellent conductor of heat and electricity. Deposited films of gold are used as layers in the production of semiconductors, sensors, batteries, and data storage.

Gold (Au) Specifications

*** Alumina Coated.

**** Suggestion based on previous experience but could vary by process. Contact local KJLC Sales Manager for further information

Z-Factors

Empirical Determination of Z-Factor

Unfortunately, Z Factor and Shear Modulus are not readily available for many materials. In this case, the Z-Factor can also be determined empirically using the following method:

• Deposit material until Crystal Life is near 50%, or near the end of life, whichever is sooner.
• Place a new substrate adjacent to the used quartz sensor.
• Set QCM Density to the calibrated value; Tooling to 100%
• Zero thickness
• Deposit approximately 1000 to 5000 A of material on the substrate.
• Use a profilometer or interferometer to measure the actual substrate film thickness.
• Adjust the Z Factor of the instrument until the correct thickness reading is shown.

Another alternative is to change crystals frequently and ignore the error. The graph below shows the % Error in Rate/Thickness from using the wrong Z Factor. For a crystal with 90% life, the error is negligible for even large errors in the programmed versus actual Z Factor.

Thermal Evaporation of Gold (Au)

Gold alloys with refractory metals making thermal evaporation out of a tungsten boat nearly impossible. We recommend using either an alumina-coated boat or a shielded, tantalum crucible heater with an alumina crucible. With an evaporation temperature of ~1,400°C and a base pressure for evaporation of 10^-6 Torr or lower, we anticipate the deposition rate to be 1-5 Angstroms per second.

If using a KJLC^® system, we recommend EVS9AAOW which is our standard alumina-coated, dimple-style boat for gold evaporation. It is important to mention that the power supply used must be capable of running high voltages in order for this method to work.

The second option is to use a shielded, tantalum crucible heater with an alumina crucible such as our EVCH1 or EVCH10 with EVC9AO if using a KJLC^® system. Great care must be taken when installing the heater to prevent the outer shields from becoming warped which can cause a short in the heater, causing the welded joints to fail. The heater should be centered between the contacts and the outer shielding must be clear of the leads. Crucibles should be stored in a cool, dry place and always handled with gloves or forceps.

Correct - Crucible heater centered, outer shielding clear of leads

Incorrect - Crucible heater off-center, shielding in contact with leads/inner shielding

E-beam Evaporation of Gold (Au)

Gold can be tricky to e-beam evaporate. The most common problem is spitting. We find that spitting is more recurrent if certain process parameters are not regulated carefully. The process parameters of concern are cleanliness of the chamber, the amount of power applied, the power ramping procedures, heat transfer from the gold into the e-gun hearth, the consistency of the crucible liner dimensions, and the crucible liner material. Improper control of these parameters may result in a deposition process that is less stable, as well as, poor consistency of films produced in terms of particles in the film.

The degree of heat transfer from the gold melt proves to be the biggest factor when it comes to spitting. When the gold heats or cools too rapidly, liquid droplets are ejected from the pocket. We have determined that the e-beam power directly relates to this issue and applying higher levels of power results in more spitting of the material. It is extremely important to use a slow ramping procedure while the shutter is closed to slowly increase the temperature of the melt. The other option is to reduce power overall during deposition to decrease or eliminate the spitting.

Chamber cleanliness also plays a significant role in proper gold deposition. The chamber should be free of any background contamination and the base pressure must be 10^-6 Torr or lower before attempting to evaporate the gold.

We recommend sweeping the e-beam and ramping power to fully melt the material before depositing films. Once melted, a focused e-beam can be used for the deposition process. With an evaporation temperature of ~1,400°C and a base pressure for evaporation of 10^-6 Torr or lower, we anticipate the deposition rate to be 1-5 Angstroms per second.

We also recommend using a FABMATE^® or molybdenum crucible liner when e-beam evaporating gold. Another process note is to consider the fill volume in the e-beam application because we find that the melt level of a material in a crucible directly affects the success of the crucible liner. Overfilling the crucible will cause the material to spill over and create an electrical short between the liner and the hearth. The outcome is cracking in the crucible. This is the most common cause of crucible liner failure. Placing too little material in the crucible or allowing the melt level to get too low can be detrimental to the process as well. When the melt level is below 30%, the e-beam is likely to strike the bottom or walls of the crucible which immediately results in breakage. Our recommendation is to fill the crucible between 2/3 and 80% full to prevent these difficulties.

Cleanliness and condition of the crucible liner are important as well. Our crucible liners are cleaned and ready for use upon receipt by our customers. However, a good practice to follow would be to wipe out each liner with IPA on a KIM wipe and check the KIM wipe to ensure no dirt is remaining. The crucible must then be allowed to dry completely.

Crucible liners should be stored in a cool, dry place and always handled with gloves or forceps.