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Doping Impurities into Porous Silicon from a Nonaqueous Solution

IP.com Disclosure Number: IPCOM000083537D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Beyer, KD: AUTHOR [+2]

Abstract

During the anodization process for producing porous silicon regions in a monocrystalline silicon substrate, doping impurities are added to porous silicon from a nonaqueous solution instead of from a vapor solution. Then a high-temperature cycle is used in order to diffuse the dopant into the silicon, which eliminates base leakage due to boron depletion or an excess charge in the recessed-oxide-insulation oxide.

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Doping Impurities into Porous Silicon from a Nonaqueous Solution

During the anodization process for producing porous silicon regions in a monocrystalline silicon substrate, doping impurities are added to porous silicon from a nonaqueous solution instead of from a vapor solution. Then a high- temperature cycle is used in order to diffuse the dopant into the silicon, which eliminates base leakage due to boron depletion or an excess charge in the recessed-oxide-insulation oxide.

After the electrochemical anodization (H(2)O-HF) process, when porous silicon is formed on the substrate, a nonaqueous solution (typically cyclohexanone and orthophosphoric acid) is substituted in the anodization process, which introduces P into the SiO(2)/Si. Porous silicon with boron is added (see Fig. 1, 5); then there is a short diffusion in an inert ambient and finally the porous silicon is converted into SiO(2) in an oxygen ambient, thus, predoping the silicon region at the Si/SiO(2) interface.

Fig. 2 shows a constant lateral diffusion where 7 is porous silicon doped with phosphorous and 9 is the spacing between the diffusion (a constant). Fig. 3 is a diffusion profile with a normal surface diffusion where 11 is the spacing between diffusions. If the structure shown in Fig. 2 is used as an NPN lateral transistor, the emitter-base and base-collector junctions have constant dopant concentrations, which is not true in normally diffused (NPN or PNP) lateral transistors.

Fig. 4 shows "reach...