EVAP,temp,rplan,dcr,mtl,sel
Deposition rate of metals using E-beam planetary evaporator

temp       temperature of the metal charge contained in the crucible  in C
rplan       radius of the planetary wafer holder in cm
dcr          diameter of the crucible containing the metal charge in cm
mtl          Evaporated metal, select Aluminum or Gold
sel          deposition rate

Deposition rate of metals using E-beam planetary evaporator

Notes

An equipment often used in MEMS for depositing metals like Aluminum is an E-beam planetary evaporator. It consists of a vacum chamber pumped to very low pressures. The charge or metal to be deposited is loaded into a crucible like the one shown in picture above. A stream of electrons is directed from an electron gun directly on to the charge in the crucible. The metal evaporates and deposits itself on the silicon wafers as a thin layer. To ensure a uniform deposition over the whole wafer surface, the wafers are loaded on a planetary wafer holder, which moves the wafers above the target on a spherical contour. The radius of this planetary wafer holder should be known for the evaporator.

This design interface can be used to calculate the deposition rate in /min for aluminum and gold deposited with an e-beam planetary evaporator with a known planetary radius and crucible dimension at any given temperature.

The plot shows the variation of deposition rate with temperature of charge. The deposition rate is found to increase with temperature and that is due to the increase of vapor pressure of the metal with temperature. Gold has a lower deposition rate than Aluminum at a given temperature.

Assumptions

-The metal charge is assumed to be uniformly heated to a liquid state at the specified temperature.
-The area of the opening of the crucible is assumed to be equal to the exposed area of the molten metal.
-The decrease in area of the molten metal surface due to evaporation is not considered.
-Sufficient vacuum in the chamber is assumed. Interaction with background gases are not considered.
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Process > Film deposition > Metal > Evaporation


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