TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The concentration of surfactant in the aqueous dispersion system is 1-500, preferably 5-100 ppm, based on the total weight of the aqueous dispersion system. The surfactants are selected from sulfate compound of formula (R 1O)(R 2O)SO 2, sulfoacid of formula R 3SO 3M or its metal salt, phosphate compound of formula (R 5O)(R 6O)(R 7O)PO, fluorine-containing polyether of formula R 8(R 9-O) nR 10, and/or polymer surfactant having molecular weight of greater than 1000.R, R 3, R 5=alkyl;R 2=H ion, alkyl, or metal cation;M=H ion or metal cation;R 6, R 7=H atom, alkyl, or metal cation;n=1-10;andR 8-R 10=H atom or alkyl, where at least one of R 8, R 9, and R 10is fluorine-containing alkyl or perfluoroalkyl, metal cation is Li cation, Na cation, K cation, Mg cation, Ca cation, Ba cation, Cu cation, Fe cation, Co cation, Ni cation, Al cation, In cation, or Sn cation, the alkyl is branched or linear 1-20, preferably 5-12C alkyl or fluorine-containing alkyl or perfluoroalkyl, any one or more H in alkyl can be substituted by 1-10C alkoxy, 1-6C carbonyl, 1-6Si silanyl, 2-10C acylamino, and/or 5-22, preferably 5-14C aryl.The surfactant is selected from one or more of 67 compounds e.g. C 12H 25OSO 3Na, C 10H 21OSO 3Na, C 11H 23OSO 3K, C 11H 23OSO 3H, (CH 3) 2CHO(CH 2)6OSO3Na, (CH3)2CHO(CH 2) 8OSO 3Na, (CH 3) 2CHCH 2O(CH 2) 6OSO 3K, C 4H 9(OCH 2CH 2) 3OSO 3Na, (CF 3) 2CFO(CH 2) 6OSO 3Na, H(CF 2CF 2) 3CH 2(OCF 2CF 2) 6OSO 3Na, C 6H 5C 12H 24SO 3Na, CH 3(CH 2) 10CH 2SO 3Na, CH 3(CH 2) 8CH 2SO 3Na, CH 3(CH 2) 9CH 2SO 3K, C 3F 7(CH 2) 2SO 3H, C 3F 7(CH 2) 8SO 3H, C 2F 5(CH 2) 6SO 3H, CF 3COC 6H 4SO 3H, C 2F 5COC 6H 4SO 3H, CF 3C 6H 4SO 3H, C 2F 5C 6H 4SO 3H, CF 3OC 6H 4SO 3H, C 2F 5OC 6H 4SO 3H, (C 2F 5) 3(CH 2) 3SO 3H, CF 3CF 2(CF 2CF(CF 3)O) 2CF 2CF 2SO 3H, CF 3CF 2(CF 2CF(CF 3)O) 4CF 2CF 2SO 3H, C 3F 7(CH 2) 2SO 3Na, C 3F 7(CH 2) 4SO 3Na, C 3F 7(CH 2) 6SO 3K, CF 3COC 6H 4SO 3Na, CF 3C 6H 4SO 3Na, CF 3OC 6H 4SO 3Na, (C 2F 5) 3(CH 2) 3SO 3Na, CF 3CF 2(CF 2CF(CF 3)O) 2CF 2CF 2SO 3Na, CF 3CF 2(CF 2CF(CF 3)O) 4CF 2CF 2SO 3Na, CF 3CF 2(CF 2CF(CF 3)O) 6CF 2CF 2SO 3K, C 18H 29SO 3K, CH 3(CH 2) 10CH 2SO 3K, C 18H 29SO 3Na, H 3SiC 7H 14COOH, C 17H 35COONa, C 15H 31COOK, C 8H 17CONH(CH 2) 5COONa, (CH 2CF 2) 4COOH, C 2F 5(CH 2CF 2) 6COOH, CF 3(CH 2) 5COOH, C 2F 5(CH 2) 6COOH, CF 3OC 6H 4COOH, CF 3(CH 2CF 2) 4COONa, and/or CF 3(CH 2CF 2) 6COOK.Preferred Method: The time for etching the polycrystalline silicon film is 2-120 hours. The aqueous dispersion system is heated at 120-250, preferably 150-200 degrees C.