Silicon-containing surface modifier, resist lower layer film-forming composition containing the same, and patterning process

A silicon-containing resist lower layer film-forming composition comprising:

• a polysiloxane compound containing a component derived from a tetrafunctional hydrolyzable monomer in an amount of 70 mole % or more of the polysiloxane compound;
• and
• a silicon-containing surface modifier containing one or more repeating units each represented by the following general formula (A), or one or more partial structures each represented by the following general formula (C):
• wherein:
• R1 represents an organic group having a hydroxyl group or a carboxylic acid group;
• and
• R2 and R3 each independently represents the same as R1, a hydrogen atom, or a monovalent organic group having 1 to 30 carbon atoms, wherein a blending amount of the silicon-containing surface modifier in the silicon-containing resist lower layer film-forming composition is 0.01-50 parts by mass with respect to 100 parts by mass of the polysiloxane compound.