The fabrication processes of semiconductor devices, etc. require reducing as much as possible contamination of the surface of a wafer with particles, metal ions or the like at each process step for the purpose of preventing the performance of the device from becoming worse and improving on yields, and the wafer surface is cleaned for the purpose of eliminating such contamination.
Among such cleaners as proposed recently in the art, there is a cleaner solution for semiconductor device substrates, which comprises (A) an alkaline component, (B) a nonionic surface active agent having an oxyalkylene group having 4 or more carbon atoms as a recurring unit, and (C) water (see, for in instance, patent publication 1). In general, however, the so-called RCA cleaning developed by RCA in 1970 has been commonly used for the elimination of particles, metal ions or other contaminants off the surfaces of Si wafers. This cleaning technique involves removing particles under the conditions of 70 to 80° C. and 10 minutes using an aqueous solution containing ammonium hydroxide and hydrogen peroxide and called the SC-1, and then eliminating metal ions under the conditions of 70 to 80° C. and 10 minutes using an aqueous solution containing hydrochloric acid and hydrogen peroxide and called SC-2. Instead of, or in addition to, these solutions, an aqueous solution containing sulfuric acid and hydrogen peroxide for removal of organic matters, an aqueous solution containing hydrofluoric acid for removal of Si oxide films, etc. may be used (see, for instance, non-patent publication 1).
In any case, however, this RCA cleaning has numerous problems. Specifically, there are:                1) redeposition of other contaminant species at a removal step for a certain contaminant species;        2) a more cleaning steps count because of involving the steps of SC-1 cleaning, water washing, and SC-2 cleaning;        3) an increase in the size of a cleaning system in association with the use of 300-mm wafers;        4) a relatively high content of hydrogen peroxide, which renders it impossible to apply the RCA cleaning to W or other metals badly vulnerable to hydrogen oxide;        5) a more cleaning steps count, which can never address the throughput of the cleaning system in non-batch-fashion, and        6) variations in the wafer surface, which are caused by heating in a non-batch fashion.        
Thus, the development of a cleaner free from such problems is now in demand.    Patent Publication 1: JP(A)2003-109930    Non-Patent Publication 1: W. Kerh and D. A. Puotinen, RCA Review, 31, 187 (1970)