Surface treatment of silicon@ wafer by electrochemical etching in dark - includes monitoring of etching progress to produce reproducible surface conditions for subsequent applications

摘要

The Si surface is etched anodically in a fluoride containing soln., pref. a watery soln. of NH4F with a pH of 3.5-5.5, of watery HF soln. or a watery soln. of a fluoride salt, in the dark, while electrostatically the reaction progress is checked by continuous measurement of parameters which each define a physical condition of the Si surface. The parameter values are constantly compared with required values and the Si wafer isolated when a predestined condition has been achieved. The wafer is then given a further treatment with liquid or gaseous reagents, pref. consisting of rinsing, pref. using water, under a shielding gas, pref. N2 or Ar. The wafer is thend ried in N2. The etching takes place pref. in an electrostatic or galvanostatic circuit. The counter electrode used (4) is pref. a net or gauze. Also claimed is the use of an etchant which is in continuous movement. USE/ADVANTAGE - The etching process can produce predefined surface conditions of the Si wafer which can be verified with other analysis methods such as X-ray photoelectron spectroscopy (XPS) or other optical methods. The process is capable of removing the oxide layer without generating defects in the Si surface. The process increases the yield of usable wafers and of devices made with them. The conditions can also be modified to generate e.g. very smooth of rough surface textures. The process is used in the mfr. of wafers for production of electronic devices e.g. transducers, integrated circuits or solar cells.