Diffusion - 2 layers Solids are available in two forms...

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Diffusion • Process by means of which a species moves as a result of a concentration gradient • Method of introducing dopants in a semiconductor • Conducted in systems called diffusion furnaces • Three main sources of Dopants: Gaseous , Liquid , Solids • Gaseous Sources (most widely used) – Reliable, convenient BF 3 , PH 3 , AsH 3 . • Source gas reacts with oxygen at the wafer surface to form a dopant oxide , the dopant then diffuses from the oxide into silicon resulting in a uniform dopant concentration across the surface Liquid and Solid Sources of Diffusion • Liquid sources are available in two forms – Bubblers and spin on dopants- POCl 3 , BBr 3 – Bubblers convert the liquid to vapor, which then reacts with oxygen to form dopant oxides on the wafers – Spin on dopants are solutions which on drying form doped SiO
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Unformatted text preview: 2 layers Solids are available in two forms Tablet / Granular and Disc /Wafer form BN discs are most commonly used oxidized at 750 - 1100 C to serve as the diffusion source Stacking Pattern for Solid Disc Type Dopants in a Diffusion Furnace Ion Implantation An alternative to high temperature diffusion for introducing dopants A beam of highly energetic dopant ions is aimed at the semiconductor target Collision of the ions with the lattice atoms distorts the crystal structure Annealing is performed to rectify the problem Ion Implantation is now preferred and extensively used by companies like INTEL. Diffusion vs. Ion Implantation. Profiles Dopant Effect on Etching...
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This note was uploaded on 11/16/2011 for the course MSE 5960 taught by Professor Douglas during the Fall '04 term at University of Florida.

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Diffusion - 2 layers Solids are available in two forms...

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