Getter Device

To eliminate the above problems and address the lifetime issues posed by the appliance industry, a novel getter device, the COMBOGETTER, has been recently proposed [40]. 

The getter device does not need to be heat activated or pre-treated before being used in VIP and can be handled in air for a reasonable period of time (several minutes), during the panel manufacturing process, without affecting its sorption capacity. 

To maintain a high vacuum during the life of the component, power tubes contain a getter device. The name comes from the function of the element to get or trap and hold gases that may evolve inside the tube. Materials used for getters include zirconium, cerium, barium, and titanium. 

In order to remove tlie unwanted electrical activity associated witli deep-level impurities or defects, one can eitlier physically displace tlie defect away from tlie active region of tlie device (gettering) or force it to react witli anotlier impurity to remove (or at least change) its energy eigenvalues and tlierefore its electrical activity passivation). 

Gettering is a black art. It consists in forcing selected impurities (typically, transition metals) to diffuse toward unimportant regions of tlie device. This is often done by creating precipitation sites and perfoniiing heat treatments. The precipitation sites range from small oxygen complexes to layers such as an A1 silicide. The foniiation of such a... 

Light is strong enough to knock off electrons from cesium, which makes this phenomenon useful as a coating for photoelectric cells and electric eye devices. Cesium iodide (Csl) is used in scintillation counters (Geiger counters) to measure levels of external radiation. It is also useful as a getter to remove air molecules remaining in vacuum tubes. 

Misch metal, an alloy of cerium with other lanthanides is a pyrophoric substance and is used to make gas lighters and ignition devices. Some other applications of the metal or its alloys are in solid state devices rocket propellant compositions as getter in vacuum tubes and as a diluent for plutonium in nuclear fuel. 

Rubidium alloys easily with potassium, sodium, silver, and gold, and forms amalgams with mercury. Rubidium and potassium arc completely miscible 111 the solid state. Cesium and rubidium form an uninterrupted series of solid solutions. These alloys, in various combinations, are used mainly as getters for removing the last traces of air in htgh-vacmim devices and systems. 

Dopant species can be codeposited with the Si02 by introducing small amounts of the dopants in hydride or halide form. P-doped Si02, called P-glass, functions as an insulator between polysilicon gates and the top metallization layer of ICs. It is also used as a final passivation layer over devices, and as a gettering source (17). 

The trend here is for simpler lifetime measurement methods and a better understanding of the mechanisms within the device or material, giving rise to the measured values. For example, for the denuded zone/precipitated interior intrinsic gettering mechanism, a high t and low is clearly an indicator of a successful process. 

For this reason, float-zoned silicon intended for the fabrication of semiconductor power devices is often specified -to contain low carbon concentration, e.g., less than 1 ppma. Carbon has been reported to play a role in the heterogeneous nucleation of oxide precipi-tates (37-40). In principle, carbon nucleation of oxide microprecipitates could be used to advan-tage in designing IC processes. In practice, however, the nonuniformity of the carbon distribution renders this an impractical approach. Thus in order to avoid uncontrolled variations in the oxide precipitation, low-carbon silicon is often specified for processes which use intrinsic gettering. 

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