Method for preparing Si3N4 composite film on surface of monocrystalline silicon chip

The invention provides a method for preparing a Si3N4 composite film on the surface of a monocrystalline silicon chip. The method comprises the following steps: taking a monocrystalline substrate of which the surface is processed as a substrate material; preparing sulfonic silane on the surface of the monocrystalline substrate by a self-assembly method; placing the substrate in a Si3N4 dispersion solution; and preparing the Si3N4 composite film on the surface of the substrate. The substrate is soaking in aqua fortis to be heated for 5 to 6 hours, is taken out to be washed by deionized water, is placed into a hydroxylation solution to be processed for 1 hour at room temperature, is soaked into a prepared hydrosulphonyl silane solution after cleaning and drying, is taken out after 6 to 8 hours standing, and is dried by nitrogen and is placed in nitric acid after washing; end thiol is in-situ oxidized into sulfonic group; and the substrate is placed in a suspension of Si3N4 to stand for 2 to 24 hours at a temper