METHOD FOR SURFACE TREATMENT OF EPITAXIAL SILICON WAFERS TO FORM ACTIVE REGIONS Russian patent published in 2015 - IPC H01L21/306 

FIELD: chemistry.

SUBSTANCE: invention relates to power silicon transistors, in particular, to surface treatment of epitaxial silicon wafers to remove any type of soiling and form active regions. The epitaxial silicon wafer treatment comprises a two-step cleaning process in two baths with different solutions: the first bath contains a "CARO" solution, comprising sulphuric acid and hydrogen peroxide (H₂SO₄:H₂O₂) at a ratio of 7.2:1.2 and temperature of T = 105±5°C; the second bath contains peroxide-ammonia solution (PAS), comprising aqueous ammonia, hydrogen peroxide and deionised water (NH₄OH:H₂O₂:H₂O) at a ratio of 1:4:22 and temperature of T = 65°C, duration of treatment in each bath 5 min. The method principle is to make sure that all the organic, ionic, chemical, gaseous and mechanical contamination is removed from the epitaxial silicon wafer surface, i.e. all heavy grease to be removed in the first bath, and all the remaining contamination to be removed in the second bath.

EFFECT: complete removal of organic and mechanical contamination and impurities from the surface of epitaxial silicon wafers, reduced process time.