Effectiveness of anisotropic etching of silicon in aqueous alkaline solutions

;Optical effectiveness of anisotropic etching of (100) silicon in inorganic alkaline solution has been studied from the view point of its application in commercial silicon solar cells. The damage caused by ID saw or wire saw during slicing of the wafer is required to be removed for fabrication of so lar cells. The etch rates for removal of the surface damages for boron dope d Czochralski wafers of 1-2 Omega cm resistivity in 20% NaOH solution at 80 degreesC was measured and was found to be similar to 1.4 mum/min. After th e damage removal, texturisation was obtained in 2% NaOH solution buffered w ith isopropyl alcohol at 80 degreesC. An optical effectiveness parameter f( eff,lambda) was defined and its value was estimated from the study of refle ctivity and topography of the wafers textured for different durations of ti me. The kinetics of anisotropic etching was studied which indicated that gr owth of pyramids begins at preferential sites which may arise due to crysta lline defects or wetting. Silicon solar cells have been realized by standar d process involving phosphorous diffusion and vacuum evaporated front and b ack contacts. The value of optical effectiveness parameter is found to have a direct correlation with the improvement in short circuit current density of the textured cells. (C) 2001 Elsevier Science B.V. All rights reserved.