Getter

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A getter is a chemically reactive material that is used to maintain a vacuum for as long as possible. On the surface of a getter, gas molecules form a direct chemical bond with the atoms of the getter material , or the gas molecules are retained by sorption . In this way, gas molecules are “trapped”.

Titanium ( titanium sublimation pump ) is mostly used in getter pumps ( ion getter pumps ) in vacuum technology . Platinum is also suitable.

Areas of application

Electron tubes

Getter ring and getter in an electron tube

This principle is mainly used to bind remaining gases in electron tubes (including picture tubes ) or vacuum pumps . In order for electron tubes to function properly, it is necessary that there is as good a vacuum as possible inside them (high vacuum). By exposing getter that bind the remaining gas molecules per se after pumping. For activation, the getter material is heated and the resulting reactive vapors bind the residual gases through adsorption or chemical bonding. In addition, the vapors deposited on the free surfaces can also bind residual gas arriving later until their adsorption capacity is exhausted.

Barium , aluminum or magnesium alloys are often used in electron tubes . The getter metal is brought into the tube in the form of a pill or ring mounted on a sheet metal together with the electrode system and, after the glass bulb has been pumped out and melted, it is inductively heated in order to vaporize the getter metal.

Semiconductor manufacturing

So-called defect gettering is also known in semiconductor production. This makes use of the fact that impurities in crystals tend to accumulate in fault zones in the crystal structure. The back of a wafer is specifically provided with crystal defects (roughened), so that during subsequent annealing, impurities diffuse to these defects. Another possibility of generating getter centers is the targeted introduction of foreign substances (e.g. boron , phosphorus , argon ) on the back. The front side of the wafer used for producing the circuit structures becomes cleaner as a result.

Food production

For reasons of hygiene, vacuum insulation with barium tubes is often used in steam lines in the pharmaceutical and food industries. Due to their low equilibrium pressure with hydrogen , barium getters are also suitable for vacuum insulation at higher temperatures (e.g. pipe systems in the petrochemical or chemical industry).

  • Oxidized getter in an electron tube due to glass breakage

  • Getterring of an electron beam system

  • Tubegetter with barium

  • Zr-Fe getter in the outer bulb of a sodium vapor lamp

literature

  • Werner Espe, Max Knoll, Marshall P. Wilder: Getter Materials for Electron Tubes . In: Electronics . tape 23 , no. 4 , October 1950, ISSN  0013-5070 , p. 80–86 (English, PDF ).

Individual evidence

  1. ↑ Max Wutz (founder), Karl Jousten (ed.): Wutz manual vacuum technology. Theory and practice. 9th, revised and expanded edition. Vieweg, Wiesbaden 2006, ISBN 3-8348-0133-X , pp. 366-367.