Phosphorus diffusion

For example, during oxidation, enhanced diffusion of phosphorus, boron, and arsenic are observed, as well as retarded diffusion of antimony. However, if direct nitridization of the silicon surface occurs, then the inverse effects are observed, that is, enhanced antimony diffusion and retarded phosphorus diffusion. Also, oxidation-enhanced diffusion is significantly affected by doping. As either p- or n-type doping concentration increases above nh oxidation-enhanced diffusion diminishes. If chlorine is introduced into the oxidizing ambient, oxidation-enhanced diffusion is likewise diminished. 

Point Defect Generation During Phosphorus Diffusion. At Concentrations above the Solid Solubility Limit. The mechanism for the diffusion of phosphorus in silicon is still a subject of interest. Hu et al. (46) reviewed the models of phosphorus diffusion in silicon and proposed a dual va-cancy-interstitialcy mechanism. This mechanism was previously applied by Hu (38) to explain oxidation-enhanced diffusion. Harris and Antoniadis (47) studied silicon self-interstitial supersaturation during phosphorus diffusion and observed an enhanced diffusion of the arsenic buried layer under the phosphorus diffusion layer and a retarded diffusion of the antimony buried layer. From these results they concluded that during the diffusion of predeposited phosphorus, the concentration of silicon self-interstitials was enhanced and the vacancy concentration was reduced. They ruled out the possibility that the increase in the concentration of silicon self-interstitials was due to the oxidation of silicon, which was concurrent with the phosphorus predeposition process. 

Figure 18. Micrographs showing variation of stacking faults inside a narrow phosphorus diffusion region and the slight enhancement of arsenic diffusion and retardation of antimony diffusion. P diffusion was at 1150 °C for 60 min. (Reproduced with permission from reference 24. Copyright 1987 The Electrochemical Society, Inc.)...

Silicon Dioxide Etchiiig Doping by phosphorus Diffusion... 

Silicon of high purity, normally p-type, is the basic material for this detector type. As with surface-barrier detectors, the silicon piece has the shape of a thin wafer. A thin layer of n-type silicon is formed on the front face of the wafer by applying a phosphorus compound to the surface and then heating the assembly to temperatures as high as 800-1000° C for less than an hour. The phosphorus diffuses into the silicon and dopes it with donors (Fig. 7.20). The n-type silicon in front and the p-type behind it form the p-n junction. 

With time, some of the adsorbed phosphorus diffuses into solid phase (absorption) where it forms discrete phosphate minerals. This process occurs very slowly over timescales of days to months or years. Decrease in quantity of phosphorus on solid surfaces results in more sites for soil pore water phosphorus adsorption. These conditions can reduce soil pore water phosphorus concentration, resulting in a new equilibrium. 

Phosphorus has more known fimctions than any other mineral element in the animal body. The close association of phosphorus with calcium in bone has already been mentioned. In addition, phosphorus occms in phosphoproteins, nucleic acids and phosphohpids.The element plays a vital role in energy metabolism in the formation of sugar-phosphates and adenosine di- and triphosphates (see Chapter 9). The importance of vitamin D in calcimn and phosphorus metabolism has already been discussed in Chapter 5. The phosphorus content of the animal body is considerably less than that of calcimn content. Whereas 99 per cent of the calcium found in the body occurs in the bones and teeth, the proportion of the phosphorus in these structures is about 80-85 per cent of the total the remainder is in the soft tissues and fluids, where it serves the essential fimctions mentioned above. The control of phosphorus metabolism is different from that of calcium. If it is in an available form, phosphorus is absorbed well even when there is an excess over requirement. The excess is excreted via the kidney or the gut (via sahva). In monogastric animals, the kidney is the primary route of excretion. Plasma phosphorus diffuses into saliva and in ruminants the large amount of chewing during rumination results in saliva being the major input of phosphorus into the rumen rather than the food. 

Khedher N, Hajji M, Ben Jaballah A, Quertani B (2005) Gettering of impurities from crystalline silicon by phosphorus diffusion using a porous silicon layer. Sol Energy Mater Sol Cells 87 605-611... 

External gettering techniques according to Hull (1999) are (i) phosphorus diffusion gettering, (ii) Al gettering, (iii) backside damage and poly-backside seal gettering, (iv) chemical gettering, and... 

The gettering efficiency of cavity gettering (proximity gettering), example of which is gettering by incorporation of controlled porous silicon single or multilayer diffusion barrier, is comparable to Al- gettering or phosphorus diffusion gettering. While the latest will remain dominant in PV industry... 

Furthermore, brittle diffusion products may be produced at the filler-base-metal interface as a result of the reaction of a component of the filler alloy with a base-metal component, e.g. phosphorusbearing fillers used for steel in which the phosphorus diffuses into the steel. 

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