The invention discloses a wet chemical 
etching method for preparing large-area and flexible ultra-thin 
monocrystalline silicon wafers, and belongs to the field of 
semiconductor technology. According to the method, 
acetone, 
anhydrous ethanol, deionized water and 
hydrofluoric acid are adopted to treat a N(100) double-side-polished 
monocrystalline silicon wafer in advance, so that the surface of the 
silicon surface is cleaned. 
Potassium hydroxide, isopropanol and deionized water are uniformly mixed to prepare a 
reducer and the 
reducer is preheated in a water-bath. After that, the 
silicon wafer is well fixed and dipped in the 
reducer by a clamp. In this way, an ultra-thin 
wafer of a desired thickness can be obtained through controlling the reaction time and the 
reaction temperature, The surface of the 
silicon wafer is bright, flat, smooth and free of any obvious 
thinning defect, and appears the mirror-surface result. According to the technical scheme of the invention, the 
thinning process of silicon wafers is simplified by adopting the single-
step method, and the characteristics of the wet 
etching technique in the low-temperature and normal-pressure condition are maintained. 
Silicon wafers with the thickness thereof smaller than 10 mm are obtained for the first time. Meanwhile, the application range of the wet 
silicon etching technique is expanded. Therefore, the method provides a novel idea and a novel technical means for the 
thinning process of silicon wafers.