Tuesday, November 11, 2014

Thermal Solutions for Condensate and Particulate Control in Semiconductor Vacuum Pumps and Lines

semiconductor gas line heaters
Semiconductor Gas & Pump
Line Heaters (courtesy of Durex)
Low vapor pressure gas delivery lines must be held at elevated temperatures (higher than the gas vaporization point) in order to prevent condensation that adversely effects process yields. Similarly, sublimation (transition of a substance directly from the solid to the gas phase) occurs when the vapor phase materials are allowed to cool in a vacuum line.  The most common types of sublimation in the semiconductor process is of ammonium chloride (AlCl2) and nitrides (NH4) (NH4Cl).

The more common semiconductor processing applications requiring unique thermal solutions for condensate and sublimation prevention are PECVD, LPCVD, MOCVD, ALD, plasma etch and other vacuum applications.

Keeping temperatures elevated along the vacuum lines, and in the vacuum pump, assures gas temperature above the vapor condensation point, thus keeping condensate at bay.  Heating the vacuum lines, vacuum pumps, and forelines, also substantially reduces sublimation in these areas.

By controlling condensate and sublimation, the need for frequent preventive maintenance is dramatically reduced and subsequently, the costs. Additionally, the life of associated valves and vacuum pumps is increased as well.

The ideal heater should be self contained, be easy to install and remove,  fit tightly on the lines and pumps, and provide optimum heat transfer. It should be powered by readily available voltages (120, 240), have built-in fasteners, and provide over-temperature limit control. It should provide process temperatures up to 200°C and have the ability to distribute wattage along the length of the process line to compensate for colder line sections. The backside of the heater should include thermal insulation that can withstand the operating temperatures, while still providing good thermal insulation.

For more information on semiconductor line, pump and valve heating contact Belilove Company-Engineers at (510) 274-1990 or at sales@belilove.com.