Method for forming multi-layer wiring structure

A method for forming a multi-layer wiring structure, wherein a lower wiring layer and an upper wiring layer are electrically connected through a via hole, comprising the following steps of:

• forming an organic SOG layer from a coating liquid directly on said lower wiring layer or on a predetermined film including a hillock protection layer which is formed on said lower wiring layer in advance, wherein the coating liquid for forming said organic SOG layer contains a compound, which is obtained through hydrolysis and condensation of an alkoxysilane compounds into an organic solvent under existence of an acid catalyst, said alkoxysilane compound being expressed by the following equation:
• general equation:
• RnSi(OR1)4−n
• where R is an alkyl group having a carbon number of from 1 to 4 or an aryl group, R1 is an alkyl group having a carbon number of from 1 to 4, and n is an integer of 1 or 2;
• forming said upper wiring layer on said organic SOG layer without using an etching back process;
• forming the via hole through an etching process by using a patterned resist layer provided on said upper wiring layer as a mask;
• conducting an ashing process to remove said patterned resist layer with a plasma by making ions or radicals which are induced from oxygen gas as a main reactant, under an atmospheric pressure of about 0.01 Torr;
• and
• filling said via hole with a conductive material so as to electrically connect said lower wiring layer to said upper wiring layer.