In modern semiconductor technology several impurity species with different applications are used. The most important ones are atoms of the third and the fifth group of the periodic table. They are used to generate positively (p-type) or negatively (n-type) doped regions in the semiconductor. For p-type doping mainly boron and indium are used while the preferred species for n-type doping are phosphorus, arsenic and antimony. The implantation of nitrogen is used to influence the diffusion behavior of boron in silicon dioxide and polysilicon. Sometimes also silicon, germanium and carbon are implanted to destroy the crystalline structure of the substrate (pre-amorphization) before the implantation of a dopant species. Thereby shallower dopant profiles can be generated because the channeling effect is suppressed (Sec. 5.2). Recently there are also investigations on the implantation of oxygen to form buried silicon dioxide layers, for the generation of silicon-on-insulator (SOI) devices. This technique is called: Separation by IMplanted OXygen (SIMOX) .
The impurities are implanted by single atomic ion beams or by molecular ion
beams, which facilitate shallower doping profiles. The disadvantage of the
molecular ion implantation is that additional impurities are introduced. The
most widely used molecular species are BF and recently also BH for
the implantation of boron and N for the implantation of
nitrogen. Tab. 2.1 summarizes some properties of the most important
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