Titanium Ti Evaporation Process Notes

Titanium is a common material found in a myriad of products including watches, drill bits, laptops, and bicycles, just to name a few. In pure form, it is lustrous and silvery-white in appearance. It has a melting point of 1,660°C, a density of 4.5 g/cc, and a vapor pressure of 10^-4 Torr at 1,453°C. It is a sturdy material which is easily fabricated when heat is applied. Its strong, lightweight characteristics and excellent corrosion resistance make it ideal for ocean liner hulls, aircraft engines, and designer jewelry. Titanium is biocompatible so it can be found in surgical tools and implants. Titanium is generally evaporated in vacuum for the purposes of wear and decorative, semiconductor, and optical coatings.

Titanium Ti Specifications

Material Type	Titanium
Symbol	Ti
Atomic Weight	47.867
Atomic Number	22
Color/Appearance	Silvery Metallic
Thermal Conductivity	21.9 W/m.K
Melting Point (°C)	1,660
Coefficient of Thermal Expansion	8.6 x 10-6/K
Theoretical Density (g/cc)	4.5
Sputter	DC
Max Power Density (Watts/Square Inch)	50*

Type of Bond	Indium, Elastomer
Z Ratio	0.628
E-Beam	Excellent
Thermal Evaporation Techniques	Boat: W Crucible: TiC,TiB₂-BN
E-Beam Crucible Liner Material	FABMATE^®, Intermetallic
Temp. (°C) for Given Vap. Press. (Torr)	10^-8: 1,067 10^-6: 1,235 10^-4: 1,453
Comments	Alloys with W/Ta/Mo; evolves gas on first heating.

* 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 Titanium (Ti)

Titanium can be evaporated via electron beam or thermal evaporation. However, e-beam evaporation is preferred. It is important to note that titanium alloys with refractory metals.

A material's evaporation temperature is often regarded as the temperature that is needed for the material's equilibrium vapor pressure to be 1E^-2 Torr. At that vapor pressure, the deposition rate on a substrate in a system of "normal" geometry is good or high. For titanium, that temperature is ~1,750°C. Titanium has to melt and "wet" a boat or crucible in order for efficient evaporation to take place. At this temperature, titanium will be liquid and will quickly alloy with a refractory boat, destroying its electrical and mechanical properties. The end result is the boat typically cracks and falls apart. Despite this, we have had limited success thermally evaporating titanium from a thin width, thick gauge, high current tungsten boat such as our EVS20A015W.

Using a new EVS20A015W, we were able to complete three short runs of about 2,000 angstroms per run with rates between 3-5 angstroms per second. Rates above 10 angstroms per second were possible. We used six 1/8" X 1/8" pellets in each run. The boats will only last for one or two complete evaporation runs at 2,000 angstroms per run. However, these boats are relatively inexpensive when compared to a box heater and crucible setup.

E-beam Evaporation of Titanium (Ti)

Titanium is rated "excellent" for e-beam evaporation. We recommend using a crucible liner as opposed to running the material directly from the copper hearth. Like with thermal evaporation, intermetallic crucibles work well with titanium due to the crucible liner material's unique lubricious and conductive properties. graphite or FABMATE^® crucible liners are available as an alternative to the intermetallic crucible liners. Graphite and FABMATE^® liners tend to be less expensive than their intermetallic counterparts. However, we have found that power levels have been more stable with the intermetallic liners. More consistent results are achieved when pre-melting titanium, as the material will wet the crucible allowing for efficient evaporation to take place.

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.

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

Titanium Ti Evaporation Process Notes

Titanium Ti Specifications

Z-Factors

Thermal Evaporation of Titanium (Ti)

E-beam Evaporation of Titanium (Ti)