Palladium Pd Evaporation Process Notes

Palladium is a silvery-white precious metal that bears a sharp resemblance to platinum. It has a melting point of 1,554°C, a density of 12.038 g/cc, and a vapor pressure of 10^-4 Torr at 1,192°C. It belongs to the platinum group of metals on the periodic table. It has the lowest melting point of the elements of this group and is the least dense. Palladium is remarkably malleable, ductile, and corrosion resistant. Like platinum, its most prominent use in industry is as a catalytic converter. It can also found in jewelry and surgical instruments. Palladium is evaporated under vacuum for the manufacture of semiconductors, sensors, and data storage.

Palladium Pd Specifications

Material Type	Palladium
Symbol	Pd
Atomic Weight	106.42
Atomic Number	46
Color/Appearance	Silvery White Metallic
Thermal Conductivity	72 W/m.K
Melting Point (°C)	1,554
Coefficient of Thermal Expansion	11.8 x 10-6/K
Theoretical Density (g/cc)	12.02
Sputter	DC
Max Power Density (Watts/Square Inch)	100*

Type of Bond	Indium, Elastomer
Z Ratio	0.357
E-Beam	Excellent
Thermal Evaporation Techniques	Boat: W* Coil: W Basket: W Crucible:** Al₂O₃
E-Beam Crucible Liner Material	FABMATE^®, Graphite, Tungsten
Temp. (°C) for Given Vap. Press. (Torr)	10^-8: 842 10^-6: 992 10^-4: 1,192
Comments	Alloys with refractory metals.

*** Alumina Coated.

* This is a recommendation based on our experience running these materials in KJLC guns. The ratings are based on unbonded targets and are material specific. Bonded targets should be run at lower powers to prevent bonding failures. Bonded targets should be run at 20 Watts/Square Inch or lower, depending on the material.

Thermal Evaporation of Palladium (Pd)

Thermally evaporating palladium is difficult, if not impossible, given the capabilities of the vacuum system and power supply available.

Palladium is known for spitting. It is recommended to implement a slow power ramp and soak procedure before opening the shutter to deposit films. Incremental power increases and subsequent holds help to expel any trapped gases and reduce spitting.

Palladium has a vapor pressure of 10^-2 Torr at ~1,500°C and is very reactive with refractory metals. Once palladium becomes liquid, it will alloy with and destroy a standard tungsten evaporation boat. We recommend using an alumina-coated tungsten boat such as our EVS9AAOW (if using a KJLC^® system) to thermally evaporate palladium. Using this boat, we were able to deposit a film with a thickness of approximately 3,000 angstroms in one run. The power requirements to deposit palladium from our EVS9AAOW are at the upper limit of a single Kepco^® power supply. At 100% power, the voltage tops out at 4V and the current is around 230A. Soaks of up to 5 minutes may be required to get the palladium to melt and start depositing.

Evaporating palladium from an alumina-coated boat pushes the limits of the alumina coating. Being that aluminum oxide has a vapor pressure of 10^-4 Torr at 1,550°C, and the evaporation temperature of palladium is around 1,500°C, there is the risk of aluminum oxide showing up in deposited films. The probability of aluminum oxide contamination in films is fairly high but to what extent is unknown.

It is also important to note that an EVS9AAOW boat is good for only one deposition run. We've found that the palladium does attack and break the boat when a second run is attempted. Therefore, thermal evaporation results in limited success. E-beam evaporation is the preferred method for depositing palladium.

E-beam Evaporation of Palladium (Pd)

E-beam evaporation is the preferred method for depositing palladium as it is rated excellent for this method. Palladium is known for spitting. It is recommended to implement a slow power ramp and soak procedure before opening the shutter to deposit films. Incremental power increases and subsequent holds help to expel any trapped gases and reduce spitting.

We recommend using a FABMATE^®, graphite, or tungsten crucible liner for e-beam evaporating palladium. A key 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 3/4 full to prevent these difficulties.

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

Palladium can also be run directly from the copper hearth of the e-gun. Because of this, some customers prefer to use a pre-machined slug (or starter source) that is directly placed in the hearth pocket. The two main benefits of using a starter source are ease of use and handling as well as superior packing density. Because not using a crucible liner is not always an option, especially in shared systems, some customers will use a copper crucible liner and place the starter source in the copper crucible liner instead of placing directly in the hearth.

KJLC^® can produce these starter sources. Contact us by clicking here with your e-gun manufacturer, pocket size, and number of pockets in order for us to produce a quote.

E-beam Crucible Liner Fill Rate Calculator

Instructions for use:
Input the Crucible Liner Volume, Select Material (if not available in menu, manually input Material Density in g/cm³), and input fill rate %.

KJLC recommends a fill rate between 67-75%. Overfilling the crucible will cause the material to spill over and create an electrical short between the liner and the hearth causing the crucible to crack. 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.

The fill rate above assumes that the material is fully melted and does not take into account packing density. It should be noted that the crucible liner may need to be loaded multiple times, pre-melted, and topped off in order to achieve the final desired melt level/fill rate. When loading the crucible, do not load more than 80% of the height of the crucible liner.

This calculator is for estimation purposes only.

Crucible Liner Volume (in cc):

Material:

- or -
Density of the material in g/cm³:

Fill Rate %:

Result

See highlighted results that match your result in the table below.

Material Needed to Deposit a 1 Micron Film Calculator

Instructions for use:
Select source type, input distance from source to substrate and Select Material (if not available in menu, manually input Material Density in kg/m³).

This calculator is for estimation purposes only. The estimated mass is that needed to produce a desired film thickness (1 micron in this case) on a flat substrate at a point directly above the source, accounting for the approximate plume distribution of the selected source type. It does not account for any expected nonuniformity in thickness over a larger substrate area. More complex geometries, e.g. those with offset and/or tilted sources, may have higher material requirements. The estimated mass is for the film deposition only; additional margin should be included to account for loss during ramp-up, burn-in, stabilisation and ramp-down.

Source:

Distance of source to substrate (in cm):

Material:

- or -
Density of the material in kg/m³:

Multiplier:

Mass for 1 micron layer

Palladium Pd Evaporation Process Notes

Palladium Pd Specifications

Z-Factors

Thermal Evaporation of Palladium (Pd)

E-beam Evaporation of Palladium (Pd)