Adsorption of Metal and Organic Impurities

In addition to adsorption of hydrogen, hydroxyl, and fluorine, the silicon surface may also contain trace amounts of other species due to the impurities present in the solution. A clean silicon surface is easily contaminated by metal impurities in water or solutions. For example, the surface concentration of metals after immersion in dilute HNO3 containing 1-3 ppb of Ba, Cu, Ni, Sr, Zn, K, Al, Ca, Cr, and Fe can be in the 

FIGURE 2.14. Dependence of fluorine coverage of silicon surfaces on the pH of 1 moldm ammonium fluoride solutions which were used for the surface treatment. After Fukidome et 

TABLE 2.9. Surface Concentrations of Deposited Metals, 10 °/cm, from Aqueous Solution at Metal Concentrations of 5 x 10 M and 20°C after Immersion for 1000s  

At an impurity level of metal concentration on the order of 10 °/cm , deposition may occur by physical adsorption, chemical absorption, and displacement 

Physisorption due to van der Waals interactions takes place when the 

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