A study to understand the transport and kinetic effects in three-phase, acid-based wet etching of silicon has been accomplished. Reactants overcome the liquid-phase mass-transfer resistance and the kinetic resistance to complete the reaction. The gaseous bubbles formed by the reaction adhere to random sites on the surface and, thus, mask a fraction of the surface from the reactants. This bubble masking effect is modeled as the bubble transport resistance that acts in parallel with the liquid-phase mass-transfer resistance. These transport effects are lumped into an effective mass-transport resistance, which acts in series with the kinetic resistance. It is shown that the etched surface morphology is a function of the ratio of the effective mass-transport resistance to the kinetic resistance. A rough surface is a field of peaks and valleys. It is theorized that under mass-transfer influence, etch rates at peaks are higher than etch rates at valleys. Hence, the surface is chemically polished. It is shown that the polishing efficiency increases with increasing ratio of mass-transfer resistance to the kinetic resistance, reaches a maximum, and then decreases. Effects of mass-transfer and kinetics on the surface roughness and gloss are explained by both the developed phenomenological model and experimental data.

On page 176, Eq. 3 and the two sentences immediately following should read:µ ∝ e Ea µ /KT Since the viscosity is a transport property of the liquid, they claim that the temperaturen dependence of the viscosity can be a measure of the temperature dependence of mass-transfer rates. The argument can be valid in a limited context because the mass transfer rate decreases with increasing viscosity. However, the argument is not entirely valid because the mass-transfer coefficient is a function of many temperature dependent parameters other than viscosity.In addition, the descriptions of Fig. 4 and 6c given on pages 180 and 181, respectively, are in error. Correctly stated, they should be: Figure 4 shows the qualitiative dependence of the polishing efficiency (η pol ) on the ratio of the mass transfer resistance (R m,i ) to the kinetic resistance (R r,i ). The parameters (R m,i /R r,i ) and (R m,i /R r,i ) max , in general, should correspond to the same η pol . Figure 6c shows the qualitative dependence of the polishing efficiency on the ratio of the effective mass transfer resistance (Rm,eff,i) to the kinetic resistance (R r,i ). The parameters (R m,eff,i /R r,i ) and (R m,eff,i /R r,i ) max , in general, should correspond to the same η pol .

Approximately 40% of the refined silicon is lost as sawdust (kerf) during the cutting process while producing wafers. Attempts have been made to recycle this kerf, but abundant impurities such as carbon (∼13000 ppm) burden its recovery. Using conventional bulk heating methods to remove carbon requires long residence time and inevitably causes silicon oxidation. This makes the treated kerf unsuitable for further processing and reuse. A novel aerosol method that is effective for selective carbon removal from silicon kerf at low residence times is described. The design of the aerosol process is supported by thermogravimetric analysis of kerf that provides insights into kinetics of the carbon removal process. At 900 °C in an air atmosphere carbon was removed below detection levels at a residence time of 6 s. Under the same conditions in a nitrogen atmosphere, 90% elimination of carbon was measured. Minimal oxidation of the Si sample was observed under these conditions.

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