The surface of silicon wafer was treated with F-2 gas at 25 degrees C for 10-120 min. The surface roughness (R-a) of silicon fluorinated for 120 min was 7 times larger than that (3.2 nm) of untreated silicon. Also, the water contact angle of fluorinated silicon decreased to 7 degrees. The adhesion strength of Ni metal deposited on the silicon substrate could be enhanced by surface fluorination due to increased roughness and hydrophilic surface of the silicon substrate.